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Are my ears really that sensitive?

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Posted on September 10, 2014 at 10:11:40
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 I have a set of MGIIIa with stock crossovers. They are the version with 2 ohm wide tweeter and 1 ohm resistor fitted, and the slightly earlier version with a 10uF midrange parallel cap (not 12uF as in latter examples).

I've had these MGIIIas a few years but have not used them much or touched the crossover, as I used my 3.3Rs instead (and did a lot of mods on those). I recently broke a ribbon on the 3.3Rs and have dragged out the MGIIIas to play with in the meantime whilst I wait for some new foils for the 3.3R from Magnepan.

Bear in mind here I am a bit of a caveman and still use (and like) single amp passive drive. I personally find it a bit more coherent than biamp setups I’ve tried. Never tried triamping.

The MGIIIa started life with the older 3 ohm wide tweeter. Magnepan discontinued this tweeter ribbon at serial no 063744 and introduced a thicker 2 ohm tweeter. I’m not exactly sure why. Perhaps because the 3 ohm tweeter was thinner and broke more easily?. They put in a 1 ohm wirewound resistor into the speaker to account for the lower impedance of the new tweeter.
As we know this puts the tweeter output about 3.5 dB down in output compared to the original configuration with the 3 ohm ribbon. I can really hear this decreased output on my MGIIIas with 2 ohm ribbon. The treble with stock config on my speaker is basically muted in the compared to the 3.3Rs. So I embarked on decreasing the resistor value to increase the tweeter output. First tried 0.47 ohms for a while (ceramic 10W wirewound coffin resistor). Much, much better, but actually a bit too bright. The bass seemed a lot less substantial too, no doubt that increased tweeter output changed the whole balance of the speaker a lot. Then I tried 0.68 ohms, and that was not bad, but was too dull and lacking treble detail. Tried 0.56 ohm that was better, but also too little in treble output. So I’d narrowed it down to between 0.47 and 0.56 ohms. I can hear quite a bit different in between these two values. I would not have thought that possible?!

Anyway to get a value in between these two I’ve started using 2W metal film or 2W carbon film resistors in parallel (four or five of them). Tried 0.55 ohms, , - better but still slightly too dull. Then tried 0.51 ohms. Slightly too bright!! I’m now going to try 0.53 and 0.54 ohms, and I suspect (and hope) one of these will do the trick.

I am stunned that such small differences in the tweeter output are audible and affect the balance a lot (in my opinion)

The paralled film resistors do also sound a lot better than the cheap wirewounds, so this is a good (and easy) upgrade to do anyway. The carbon films do lose a bit on the transients (and perhaps have a smoother sound) so I prefer the standard metal films, but the carbon films are still better than cheap wirewound coffins. I also bypassed the tweeter attenuation socket to get better sound.

I changed the midrange parallel cap value in the speaker from 10uF to 12uF and this seemed to decrease the midrange output quite a bit (and changed the balance quite a bit somehow, making the midrange more distant). 12uF was too much so I tried 11uF which was quite a good compromise but I also fine tuned with this parameter and have settled on 11.2 uF. Again small differences are audible.

Will report back when I’ve tried 0.53 and 0.54 ohms on the tweeter.

I think Magnepan was a bit careless by just slapping in a 1 ohm resistor when changing to the 2 ohm tweeter as the audible decrease in output of the tweeter from the 3 ohm without resistor is very large in my opinion. You go from an open, detailed, airy sounding speaker to something that sounds like it doesn't have a ribbon tweeter in it at all. All the fantastic ribbon tweeter transients are lost as well IMO. The 2 ohm tweeter actually measures about 2.2 ohms (measured mine a few years ago) and the original 3 ohm measured 2.75 ohms (measured some I had in a set of Tympani IVa few years ago), so using a resistor of about 0.5 ohms gives roughly the same impedance.

On a separate issue. I am having a slight problem with the sound of the MGIIIa. On the electrical frequency response of the stock crossover there is a bit of a peak at around 1-3 KHz and I think I can hear this. Its making the sound a bit too forward and hard to listen to.

Andy’s MGIIIa tweaks page http://www.integracoustics.com/MUG/MUG/tweaks/AndyR/
usefully outlines a few ideas for getting the FR a bit flatter (and shows the stock response with that peak), but changing those values does involve quite a bit of work (especially if I am using the crossover at speaker level with a single amp changing all the speaker level components). Bit of a longshot but was wondering if anyone had any ideas of how I could try to reduce that excess energy around 1-3 KHz?, without having to resort to EQ or changing loads of crossover values? It might not be possible to easily reduce it unless the stock crossover is changed quite a bit I guess. One thing I had thought of doing which might reduce that energy was to disable the midrange parallel capacitor (turning the midrange bandpass LP into 6dB octave, instead of 12dB/octave), essentially going back to MGIII specification (and also using MGII spec of 35uF worth of caps on the external HP crossover instead of 60uF and the inductor as per MGIIIa specs). The bass LP crossover values are the same in these two models.

The later Magnepan models 3.3R, 3.5R and 3.6R introduce an “audiophile dip” in the presence region around 1-3 Khz, which addresses the problem I am hearing with the MGIIIas. Those crossovers are quite different in terms of values though and also designed around the specific (and different) panel tension of those particular models

If anyone (who is more technical than me!) has any ideas of what might help (and preferably be simple) regarding the peak I am hearing from my MGIIIas, I’d love to hear from you.

 

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RE: Are my ears really that sensitive?, posted on September 10, 2014 at 10:40:08
Swamis Cat
Audiophile

Posts: 272
Location: Illinois
Joined: September 7, 2013
 I recently upgraded from my 27 year old IIIa's to the new 3.7i's and agree that the upper midrange is substantially smoother in the new speakers. The upper mids are the biggest difference between the two models, IMO.

Straight on, the upper mids are peaky in my room on the IIIa's. The way I always addressed it was to use a Limage type set up -- placing the speakers wide closer to side walls WAY out in the room from the front wall with minimal toe in and tweets inside. This reduces upper mids in two ways, it reduces the front wall reinforcement (based upon distance), and it reduces the direct mids due to minimal toe in. Side benefits are awesome low bass and amazing soundstaging. Others mileage may vary of course.

One last trick that worked in my room was to reverse the panels. I simply played them backward. This smoothed out the peaks and increased treble relative to mids, perhaps also compensating for my later model IIIa tweeter. I swear the IIIa sounds wrong to me when played facing forward. Reversing the panel is not without drawbacks, but the pros outweigh the cons, especially in a Limage setup.

For the record, I have not found the Limage set up to work to my ears in my room on the new 3.7i's (nor does playing them backward!). The new speakers only seem to work when set up as per the manual -- with tweeters aimed directly at or within inches of my ears. Even here, the upper mids are still recessed pleasantly.

Not sure if any of this helps. Setup can be so room dependent.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 11:22:53
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Thanks for your insights.

Assuming you had the same MGIIIa version as me (with 2 ohm tweeter and 1 ohm resistor) I think the reason it sounds wrong played face forward is because the tweeter is attenuated too much (like I say Magnepan not taking enough care with that tweeter change). Reversing the speaker obviously increases the tweeter output as there is no cloth or tweeter cage in the way. Decreasing the resistor value also does the job in increasing the highs very well though, but I'm still left with these peaky mids which are troublesome. According to Neoliths old spreadsheet (can't get the new version working) the older MGIII spec might reduce this midrange problem. I might try it. Its not too hard to do from where I am now with stock MGIIIa spec.

The 3.7i looks really nice from the views I've read. Apparently the older 3.7 model is colder sounding which I would not want. Again there is a problem in Europe as if you bought the original model there it's not feasible to send it back to Magnepan for the "i" upgrade.

Sadly my room is the wrong shape for the Limage set up and there is too much stuff in it at the moment, but I am very intrigued with views I've read about that configuration. When I get a more suitable room one day I will definitely try it.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 12:06:51
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 "Setup can be so room dependent."

Really true. Maybe even more so with dipoles. I think measuring the frequency response in various directions could give more insight. It is also true that later models have slight audiophile dip. Have you tried any acoustic treatment? Hang some damping material behind the midrange drivers and see what happens.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 12:41:12
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001



Hi Roger,
Thanks for the tips.
The MGIIIas have magnets to the front, so its not so easy to add damping, but maybe I can suspend something like you say, or reverse the speakers back to front (though that will mess up my tweeter resistor tuning). Have you any ideas what's a good damping material to try.

I have tried measuring the FR sweep again using the Anthem ARC system in my MRX500 AV receiver (this time with a 0.47 ohm tweeter resistor installed instead of 1 ohm), though as we know dipoles are hard to measure so this is probably not quite what we hear. The output does look quite strong around 1-2 KHz, but its not as bad or a peaky as the measurements I took the other week before I changed the mid cap from 10 to 11.2uF and decreased the tweeter resistor. I guess the improvement in the peakiness has come from increasing the mid parallel cap.

I will try measuring at different positions in the room, - in fact with these graphs you can measure between 5-10 positions for a single graph and it averages it. I was doing 5 positions quite close around the listening area, which was probably not the best way to do it!

One thing I will say about the MGIIIa is that the bass (when they are run full range) is good. It's bigger and more punchy than the MG3.3Rs. Not sure why. The bass panel tension is different of course, - two buttons on the MGIIIa and one on the 3.3R and tuned differently.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 12:47:52
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001



Here is the FR sweep I did the other week when the 10uF midrange cap and 1 ohm tweeter resistor were still installed. Its more peaky in the midrange, so things have improved somewhat!

The big peak at 60-80 Hz (which is also visible on the subwoofer plots) must be mainly from the room itself.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 13:07:10
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 Davy,

I meant adding damping or diffusors behind the midrange driver. You can also try to locate where this midrange peak is alonge the midrange driver. I think the frequency response is slightly different along the driver in the vertical plane. I have not seen any strange peaks in my own Magnepan speakers, maybe you hear some sort of distorsion? No loose wires or buttons?

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 14:14:39
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 Your observations are all in line with my own and those of others who have listened to the "sound of components". Ribbons are all too revealing of the differences between various components. If you still hear end of record distortion then you probably would notice all you described as well.

As to the proportions with the damping resistor, you have a up 50% down 30% adjustment and a subsequent up 6db difference in relative levels (no resistor vs 1 ohm ) and a change of XO freq from say 2khz to 3khz, and move of tweeter phase at 2khz by something like 20 some deg.. So discerning a difference between 0.4 and 0.6 ohm resistors is not at all outlandish as the difference in overall impedance is 10%.

***The other thing to remember in changing your tweeter's damping resistor is that it changes not only the level at the tweeter but also at the other drivers - since it is not buffered, so you have a double impact - lowering impedance brings more current to your tweeter and less to the others.*** Besides this you are changing the phase significantly and changing the corner frequency for the tweeter high pass, raising the defacto HP freq as you lower impedance. This can have the added impact lower down in freq where the upper mids have less of an overlap with the tweeter.

Item in bracketed in *** is incorrect in this case since the other legs in the XO are isolated by reactive components. This mind fart is because of my 2 level adjustments in the PLLXO and their interaction with each other and the filter loads - something I need to keep in mind every day as I need to tune bass to the recording at least once every listening session.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 14:18:53
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Hi Roger,
Yes I realise you meant add damping behind the driver, was just wondering what sort of damping to use.

I've did dealm repair on these IIIas a while back, no problems inside. Like Swamis Cat says above, the MGIIIa with stock crossover is just peaky in the mids, which I am sure is the issue I am experiencing. Like we said before Magnepan addressed this issue in later speakers. In fact when i had my 3.3Rs stock there was too much suckout in the midrange for me personally, though it was still probably easier to live with than a hard midrange sound. My father had a pair of original MGIII and those were not as peaky from memory and sounded good. Might revert to that crossover and see what happens, its quite easy to do from MGIIIa stock and much easier than changing all the values in the crossover. I already have the 35uF external HP caps made up. The imaging etc might change but to be honest I don't' really care if the tone/FR is better.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 14:37:49
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Hi Satie,

Many thanks for the explanation as to what I've been experiencing, - particularly with your last point. When I reduced the tweeter resistor to 0.47 ohms the bass was really reduced. I actually suspected the reason was a bit more than just the tweeter being louder, - the bass and mid had actually reduced too! Some fine balance to be tuned here. Its a bit of a pain in some ways. One might say I should have gone with triamping to get more control and avoid these sort of issues! In the meantime I think either 0.53 or 0.54 ohms will do nicely. When I've sorted that I get on with trying to address the hardness in the midrange with these MGIIIas.

Don't laugh but I'm not using vinyl much these days so don't experience end of side! In fact I'm mainly using the Spotify streaming service app from an Ipad Mini Retina into a DAC with a long USB cable (holding the ipad at listening chair!). Works very well and oh so very convenient. Perhaps not quite the full choice of everything with classical (but still very good), and all the mainstream stuff is there. Whatever you want to hear is one simple search away and plays immediately. I know it does not sound as good as vinyl, but I really like the convenience and the way you can listen to new stuff so easily. I recommend trying it with Ipad, PC or even a smartphone into a DAC. It free to try out.

I used to hate end of side distortion to be honest. I could always hear it even with setting up cartridges very well. Don't miss that not using vinyl much!

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 15:41:32
Davey
 That's not a damping resistor. A damping resistor would be in shunt with the driver, not series.

Also, the changing value of the tweeter series resistor will not affect the other drivers. Once again you're being confused by the voltage source aspect of the power amplifier and how current is "distributed." Yes, more current to the tweeter, but current draw to the other drivers will be unchanged.

You really need to work on your understanding of these issues.

Cheers,

Dave.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 16:04:54
Davey
 It's not sensitive ears......these are low resistance drivers you're dealing with so it makes sense that finer increments of attenuating resistors can be audible. No mystery there at all.

Dave.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 18:20:17
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Agreed,
I tried 0.53 ohms tonight and I can clearly hear the difference between that and 0.51 ohms.

I think Satie has a good point. Its not just about the output of the tweeter changing, the levels of mid and bass are changing too (and the crossover point and phase are slightly changing too) when altering this resistor, kind of magnifying the effect of the change. One thing is for sure IMO, that Magnepan messed it up putting a 1 ohm resistor in there..

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 18:38:29
Davey
 No, the levels of the mid and bass are not changing. Satie is mistaken with his understanding of that aspect. He fell into the same trap awhile back with his misunderstanding of the Sanders interconnect A/B scheme. It's a very simple concept here, and one that he's over-thinking and coming to the wrong conclusion on.....as he generally does. :)

Yes, xover point and phase are slightly changing, but only as a result of the change to the tweeter network and not because of any change to the mid and bass networks.

Cheers,

Dave.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 19:18:02
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Well I will say that the bass does seem to change a lot with a reasonably small decrease in the resistor value, going from quite a big bass to verging on anaemic, so it kind of made sense to me when Satie said the bass/mid was decreasing as well as the tweeter increasing.

I'm not as technical as you two guys so I wouldn't want to comment. Guess I have just have to fine tune it to my tastes. I have it near to dialled in now at about 0.53 ohms. My next problem is trying to reduce the 1-2 KHz excess in this speaker somewhat.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 20:09:08
Davey
 The relative change is tricky and can easily fool you subjectively.
But, the fact remains, there's simply no mechanism for that series tweeter resistor to change the woofer or midrange drive level. It's just not electrically possible under normal circumstances.

Satie is under the illusion there's some sort of zero sum game regarding current "splitting" at work here, but it just doesn't work that way. :)

Cheers,

Dave.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 20:09:51
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 Re Damping resistor - acknowledge the incorrect use of the word.

Re current distribution - depends on how much reactive components are "isolating" the other legs - in this case you are obviously right because of the series capacitor.

 

RE: Are my ears really that sensitive?, posted on September 10, 2014 at 21:38:05
Davey
 The large capacitor feeds both networks, but nominal tweeter resistor changes like Davy is experimenting with will not change the midrange drive level. However, if the tweeter fuse were to blow, ie, creating a LARGE value resistor for the tweeter, then you would see about a 1db increase in the midrange drive level. But not in the bass level.....that section is isolated from the mid/tweet section so it wouldn't matter.

The power amplifier does most of the "isolating" not the reactive components in the crossover network.

Cheers,

Dave.

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 00:40:27
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 What does your dac do to the spotify stream to make it tolerable?

Going to my DAC it was too hard and sharp sounding like early digital or lossy mp3. I tried with Grado 325s which are quite forgiving but couldn't bear it there either.

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 03:18:18
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Well digital is likely going to sound somewhat harder and sharper than vinyl to some extent , no two ways about it.

I still use the Beresford Caiman Class A output DAC with the Gator Board (that has discrete components). This is the least digital sound I have heard, it's much smoother sounding than the older caiman board with integrated chips. I have ditched my newer Beresford Bushmaster. Quite smooth but way too bright sounding. There is a new Caiman 2 that people are raving about at the moment. Might try that one. I also have an Arcam RDAC which is duller sounding than the Beresfords and very smooth sounding, though it's not quite as detailed. That’s not a bad choice for someone who wants a smooth digital sound coming from analogue, and it can be very cheap if you pick up a used one. Apparently the Rega DAC is also very good too. I want to try that one. The Lavry DA10 or DA11 DAC is also supposed to sound very smooth, but more pricey.

I had a conversation on a headphone forum a few years ago about getting used to the tone of a particular headphone and this (quite technical) guy reckoned it takes about 2 weeks or more for your brain to become fully accustomed to the FR/tone of a new headphone and its only effective if you exclusively use that new headphone over that time. I have noticed this is certainly true with headphones. If you have been using one particular headphone for years, you've become very used to the Fr and virtually anything else won't sound right unless you give it time. Similarly if you want to be able to tolerate the lack of treble and bass on horn speakers it's only possible if those are exclusively the only type of speakers you listen too. So this is a key principle to bear in mind. You will be very used to the sound of your Record Deck. To be honest I think many record decks have a somewhat u shaped sound, and digital is flatter and more "accurate". When you are used to a u shaped sound, it can be pretty difficult (but still possible) to go to more "neutral". I certainly found this the case with headphones too.

If that doesn't work I suppose it might be possible to adjust your mid/tweeter crossover to give less in the presence region, and reduce the treble output too if you still have problems.

One thing I did notice with my 18 6 6 6 modified 3.3Rs (when I recently tried them after not hearing them for a couple of years) is that I think that crossover has way too much output in the presence region/at the crossover point of mid and tweeter. The mid and tweeter are connected with same polarity. I recall you using the same mid/tweeter crossover on your Tympanis. I remember in the past when I tried opposite polarity on mid and tweeter it was too sucked out in the presence region. Though it will affect imaging and you will not get linear phase I think it's possible Magnepans MGIII 18 6 6 12 crossover is better tonally at the crossover point, with the phase of the tweeter 90 degrees different to the other 18 6 6 6 crossover, and providing a nicer response in the presence region response. Can't tell you for sure as my 3.3Rs have a dead tweeter right now! Might be also be something worth altering if you intend to listen to digital.

Also I use interconnects made from Belden 89259 which has low capacitance and a very smooth and slightly dark sound. Something like that can help with digital too. Certainly stay away from anything with silver in it completely (interconnect or speaker cable wise)

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 08:14:21
Swamis Cat
Audiophile

Posts: 272
Location: Illinois
Joined: September 7, 2013
 "One thing I will say about the MGIIIa is that the bass (when they are run full range) is good. It's bigger and more punchy than the MG3.3Rs. Not sure why. The bass panel tension is different of course, - two buttons on the MGIIIa and one on the 3.3R and tuned differently. "

The deep bass on my IIIa's is a completely different beast from my 3.7i's. My room is real favorable to 30 hz, and in the right set up I can get good bass down to the upper twenties with the old model, with a small and appreciated peak at 32. The new model only reaches into the upper thirties. However, the middle and especially upper bass is substantially better and fuller on the new guys. On most music, the new models have punchier effective bass. Considering I can also get better low bass from a good sub, I think the tuning of the new models is more practical for me.

One thing I forgot to mention for dealing with the peaky upper mids, is that I bought a pair of DWMs. This fills in the upper bass and lower mids and balances the IIIas. I am not currently using the DWMs with the 3.7i's. They simply do not need it. The IIIa's benefited greatly.

Oh, and I tried placing felt over the rear of the midrance at one time. It definitely affects frequency response and depth, but I was not happy with the overall effects in my room. It was a short lived experiment. Oddly it didn't just decrease mids. It increased it at some frequencies and decreased it in others. I don't know why.

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 08:18:45
Swamis Cat
Audiophile

Posts: 272
Location: Illinois
Joined: September 7, 2013
 "If you still hear end of record distortion then you probably would notice all you described as well."

Satie, would you say ribbons are more revealing of end of record distortion? This characteristic in records is frustrating, to say the least.

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 10:03:17
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Thanks for the info. Yes I guess the 3.7i has slightly less ultimate extension than the older models as the bass driver has to work up higher due to the first order crossover. Still sounds great if the bass quality is better. Will have a wait quite a while for used ones to turn up on the market. I don't want to get a 3.7 if I can't upgrade it to "i" spec (I'm in London, UK).

Thanks for the info on the damping you tried, and the DWMs. Might get a pair of those at some point soon anyway, as they look like useful devices.

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 10:30:38
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 My DAC is a musical Fidelity so is not voiced brightly and is quite smooth - it has the openness but not the extension of say the PS audio DSD DAC, which is also smoother and alive on top. The vinyl deck has a far stronger top end, compared to the DAC the vinyl is downright raucous while the digital is nowhere near that lively.

The tonal balance of my midrange drivers actually dips down 2db to 4khz and I moved the XO to 5khz which dictated a 2nd order HP, which is composed of a pole at 5khz and one at 250 hz to match with the mid HP. For bass I have been switching between the LR4 Rane 23 (has a delay adjustment to match phase) and 1st order.

Point is that the mids don't share the maggie bumps at 1 and 2-3 khz. I left a potentiometer in the midrange LP so that I could tune the 5khz combination bump out by ear.

This is all to say that the same DAC doing Spotify (or pandora) produces screechy violin sections and unfriendly sharp piano. Doing PC playback from downloads or rips produces slightly better results than the transports I use and there is by no means any hardness or grain. To the contrary, the top end is too quiet for my taste - unless playing Spotify or Pandora.

The cartridge I use, the 205C Mk4 is sporting a JICO SAS stylus, not the 206C that you heard. That does not produce the smiley shaped FR but is flat on top with a strong bass.

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 14:33:44
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Hi Staie,
Ahh yes I forgot you had an MF Dac. Must be quite smooth sounding (comparatively).
You obviously have a cartridge with a lively top end. Sounds nice. I think I did hear a 205 but can’t remember which one. Didn’t like it but that might have been partly as my MM capacitance was not optimal.

It's good the Neo midrange drivers don’t have the Maggie midrange bump and its possible to use the first order crossovers (or near to first order in the case you have now), without a bump in the presence region (like I am experiencing with both my MGIIIas stock and the 3.3Rs with my modded 18 6 6 6 crossover).
Your Rane active crossover sounds v useful on the bass to introduce delay. If I go active again I would want an adjustment like that.

I don’t know why digital does not sound as natural as vinyl on particular things like strings or piano. People have theories about quantization, the record deck adding nice distortion and other theories but there certainly is quite a difference and it can be hard to tolerate digital if you are very used to vinyl.
My point before was that (although it is difficult to do!) if you abandoned vinyl for a while and only listened to digital your ears would likely slowly adjust to the tone and the overall sound somewhat over time. I don’t think the two work that well side by side as the vinyl is nearly always going to sound preferable.

Also a lot of digital transfers of older stuff are not that great and the vinyl sounds way better. that is a problem. Some older classical recording are intolerable to me too. The newer recorded stuff seems a lot better on digital.

When you are talking about doing rips are you talking about ripping 44.1K/16 bit CDs? If that’s the case it is a bit strange that your rips are different in tone from Spotify or Pandora. It should really be the same I don’t really see why the tone would change even though the bitrate is lower with the streaming service (320 kps max with Spotify). That should not make a difference so I’m not sure what is going on there. Apparently Deezer are bringing out a 1441 kps cd quality uncompressed streaming service (on 15th September) which might be good. Though apparently most people can’t tell the difference between 320kps mp3 and uncompressed 1441 kps, the difference is probably quite audible on Maggies.

I’ve had success getting rid of the midrange peak with my MGIIIas!. Will do another post.

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 14:42:51
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Success!!!!

I’ve converted my MGIIIa into MGIII spec by simply disabling the parallel midrange cap and replacing the external HP (originally 60uF caps and 3.5 mH inductor) with MGIII spec of 35uF caps only.
The sound has transformed. What it has done is remove the nasty 1-3 KHz peak I was having trouble with. I realise this is probably a combination of a few things happening, - the phase of the midrange being altered 90 degrees to the tweeter giving less constructive interference at the crossover point, and removal of the cap maybe doing other stuff.

Essentially these speakers now sound very similar to the MGIIIs my father used to have. Wonderfully extended treble but a (crucially) a non fatiguing sound.

Might it be a good idea to try to flip the tweeter polaity and see if there is any difference to the sound? I don’t think there should be much, but you never know until you try I guess.

One slight issue is that I find the treble a little too bright with a 0.51 ohm attenuation resistor on the tweeter, but the bass is already quite strong (stronger than it was with MGIIIa spec with that value resistor). If I increase the resistor (say to 0.54 ohms) the treble will probably be more to me liking but the relative balance of the bass is likely to become too strong I think (will try it though). I suppose biamping is a simple solution to this issue if it’s a problem (just need to get another power amp, I have the crossovers needed).

So there we have it. An pretty easy way to remove the nasty hard midrange peak your MGIIIas, and improve the top end if you have the 2 ohm tweeter and 1 ohm resistor. Disable the 10 (or 12) uF midrange cap, and decrease the tweeter resistor value. I recommend between 0.5-0.65 ohms depending on taste.

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 19:01:50
Utley1
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 TRY THIS ONE ON FOR SIZE...Pull out your ears or put wine corks behind the out rim of each ear while you listen to music....Probably it is something every one knows---a noticeable and wonderful change occurs in the depth and fullness of sound...I am 60 plus and need every audible advantage...this one of the cheapest fixes I have every found..Ears are that sensitive...Crazy UT

 

RE: Are my ears really that sensitive?, posted on September 11, 2014 at 21:15:10
Davey
 Your rhetoric is silly and pointless.

I don't speculate.....I'm just informing Davy/Satie the way the crossover network operates, electrically. Maybe you didn't catch/understand the fact that I agreed with Davy that small value tweeter resistor changes could certainly be audible with these transducers?

Anyways, you're perfectly at your leisure to ignore the engineering. Many in this hobby do. :)

Cheers,

Dave.

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 00:03:48
JBen
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 Yey! Ain't that the truth, UT! I am also intrigued by the SQ differences in corks. Like, if the cork came from a bottle of Merlot wine it doesn't quite develop as much slam as if from Malbec. Hmmm, actually, they both equalize to the same slam if one drinks the whole bottle, come to think of it. LOL!

Oh, and remember the old "arms behind the head" trick? I love it but can't find a way to measure the frequency response unless I glue the damned microphone to an elbow. :-))

On a more serious note, Davy you seem to be on the right track, kudos! With the feedback from some of your measurements and what your ears tell you, you will keep discovering a few fun and useful things. Your "...you never know until you try..." is right on the money.

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 01:00:09
Utley1
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 Although each of our skulls vary, he nerves along the parietal bone somehow come into play.Obviously the frequency response from the 'speakers' remain 'objectively' the same sound as perceived becomes distorted in some sort of lively way. Once again I enjoy Davy and Satie figuring things out.

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 01:05:38
Utley1
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 Hardly meant to offend...

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 07:15:58
Davey
 No offense was taken. You comment was simply silly and had nothing to do with the topic under discussion in this thread.
As you've probably seen me say before, subjective evaluation is incontrovertible, so there's no way I can argue with what you or Satie or Davy or JBen or whoever is hearing. But what I can do is analyze the electrical changes of networks when they're made and determine whether the audible change has any basis in the engineering.

You fellas can beat me up all you want......I don't mind. :)

Dave.

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 07:25:38
Utley1
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 I respect everything you say and try to do..What I offered was inappropriate given the context. Sorry.

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 07:49:17
Davy
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 Cheers, yeah that's right. I'm not too technical with stuff like Davey and Satie are, but just like playing around, and you never know until you try is quite true with Maggies in my (reasonably limited) experience. Magnepan must do that to some degree too, - look at all the tension buttons in the 3.7 for example. I suspect some of that was done by trial and error.

I find it useful and v interesting to have some solid technical input at times though, so many thanks for your sound input Davey, and thanks to Satie who in the past pretty much taught me all I know about crossovers etc. Didn't do that much physics at school (wish I had) but it's really great to learn a little bit to help with this hobby later in life!

The stock MGIII crossover was good (much better than the MGIIIa crossover IMO) but I had a bit of a suckout between 400-900 Hz, though the troublesome 1-2 Khz area was much improved. The bass was also a little too prominent. Will post the Anthem ARC FR graph of this setup I measured last night (average of 5 different microphone positions around the listening area).

To improve things Roger (who has experience and some simulation software) kindly suggested to increase the external HP caps to 60 uF, which decreases the midrange dip and the 1-2 KHz is still much better than the MGIIIa crossover (the latter had a considerably bigger peak). I used Neo's spreadsheet to run simulations too and saw the same thing.

I've increased the midrange caps from 35 uF to 45 uF and really like the result. Bass is less muddy and not as overbearing, and the suckout in the midrange is really improved. I tried 60 uF too and that was pretty good, but the bass was getting a little weak. I suppose that also adjusting the tweeter attenuation resistor would alter the balance as well so I need to try that too with these new different cap values.

I am not sure how Magnepan got the original MGIII to sound well balanced with 35uF of caps on the external HP (and it does sound excellent, from my memories of my Father's MGIII). With this exact same crossover setup put in the MGIIIas it clearly sounds too sucked out in the 400-900Hz region and that's very visible on both in room FR graphs, the electrical simulation, and what you hear (well, what I hear!). I have the original Magnepan Schematic for the MGIII which Karen kindly emailed me a few years ago. (I should probably submit it to the MUG page), and 35 uF caps is definitely what they used. Perhaps the bass or midrange drivers in the actual MGIII had different sensitivity?. Perhaps they used different gauge of aluminium wires altering the resistance of the drivers? Will check with Magnepan RE the wire gauge as I'd be interested to know.

So I think somewhere between 45-60 uF on the external HP will be optimal for my MGIIIa. No parallel inductor (as in MGIIIa spec) is needed so it now an all first order bandpass like the MGIII. If you look at the electrical simulation, introducing the parallel 3.5 mH HP inductor actually makes the FR more peaky!, - especially in the 1-2Khz region by around 2 dB! That makes the speaker sound way too forward and hard to listen to in my opinion.


 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 07:59:35
Davy
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Here is the measurement I had last night after adjusting the MGIIIa crossover to stock MGIII (35uF caps on the external HP, and disabling the internal crossover's midrange inductor).

Compared to stock MGIIIa (see higher up the thread) the midrange is overall reduced in volume, with the peak around 1-2 KHz much improved, but the 400-900Hz area is more sucked out.

Will measure again soon with 45 or 60 uF worth of caps on the external HP. 45uF sounds great to me so far. Pretty well balanced. Perhaps I would like a bit less midrange suckout and more output in the 100-200 Hz region (like there is with the later Maggie 3 series models) but that would probably be quite hard to do without completely redesigning the crossover and changing many values.

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 08:03:22
Davy
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And here are some electrical simulations with Neo's spreadsheet (old version)

Stock MGIII

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 08:04:55
Davy
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Modified MGIII type crossover with 60uF caps on the external HP

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 08:08:21
Davy
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Stock MGIIIa crossover.

Note the bigger 1-2 KHz peak, which (IMO) is audible and troublesome, and the slightly worse dip centered around 500 Hz, compared to the crossover Roger suggested just above (MGIII type crossover with 60uF caps on the external HP)

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 12:06:36
Satie
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 This one looks better than the one with the inductor connected in the mid HP.

If you are saying that the one with Roger's 60uF cap but keeping the 2nd order mid HP has an audible midrange bump I would agree. I think the midrange comes out slightly more sensitive than the bass so to get an idea of the actual final response you would need to imagine the Gann diagram as having the midrange contribution about 1 db higher. That coincides with the measurements you took, though you would want more of them averaged on a 20-30" window to get a definitive idea of the FR.

Anyway, this looks better on the lower peak impedance and flatter FR and lack of a bump in the 1-2 khz range. Besides that it is a 1st order filter, which I would take over a 2nd order any day so long as no drivers are put in danger and nothing untoward happens.

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 14:57:55
Davy
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 Thanks for the input Satie. Will bear in mind the midrange sensitivity issue when looking at electrical response.
The Anthem Arc software can do up to ten positions for one graph, so I will take you advice and do that and spaced further apart. Thanks for that. Using ARC is substantially quicker than doing manual measurements with a meter!

I'm a bit confused with your second paragraph. I'm trying 60 uF worth of cap on the external HP, no inductor. When you say keeping the 2nd order mid HP do you mean the mid LP? If so. I've not tried that with solely the caps on the external HP. I've disabled the mid LP parallel cap in the internal crossover and it's just a 0.4 mH series coil, as per MGIII stock spec. That's the first thing I did. The mid HP is the 60 uF worth of caps and no inductor

To be honest with that particular setup (60uF caps on the external HP with no inductor (18 6 6 12 spec) the sound is not right somehow . The bass is weak and the sound quite thin overall and it sort of sounds "dead".Although the electrical plot of it above (2nd graph) looks similar to the 18 12 12 12 stock MGIIIa plot (last graph above) the two don't really sound similar. The MGIIIa stock crossover is actually pretty good throughout the freq range with much better bass, better lower mid. The only problem is the nasty peak at 1-3 KHz which really spoils things. Roger also suggested trying a dip filter to combat it. I suppose that's a possibility, or doing more extensive redesign of the crossover and changing many part values. The latter is quite a big job though.

It's a shame the straight MGIII spec with 35uF external caps sounds too u shaped as otherwise it sounds good and very pleasant. I think Magnepan must have increased the midrange driver sensitivity in the original MGIII to make that work I think. I actually quite like a somewhat u shaped FR but it's a bit too sucked out in the 400-900 Hz region even for me.

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 17:16:47
Davy
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 Was thinking of another couple of options rather than redesigning the whole crossover.

1. Find out if the wire gauges of mid and bass are different between MGIII and MGIIIa and if so, rewire the MGIIIa and use the MGIII crossover. A big job, but could be an option and probably far cheaper than redesigning and changing the whole crossover. Would just need to buy the wires. Have all the other stuff for the job. The original MGIII does sound v good IMO so this is an option I'm considering.

2. Put in an extra midrange LP inductor into the stock MGIIIa internal crossover (0.4 mH inductor and 11uF cap) making it third order (as in the 3.3R, 3.5R and 3.6R spec) and hopefully reducing the 1-2 KHz dip. Not got the spreadsheet at hand to run simulations and am not sure how easy or hard this is. I suppose it might take quite a bit of trial and error to get it to sound ok. This is the sort of crossover that was in the 3.3.R stock spec which I found phasey and a bit troublesome, but if it helps the Nasty midrange peak I'm interested in it.

Won't be using the speakers again until early next week so I have some time to think of strategies.

On a separate note I wanted to ask. In the 18 6 6 6 spec I put in my modded 3.3rs (before I broke the tweeter) I was also having trouble with peakiness in the presence region after not hearing it for a long time. This showed up on the Anthem graphs too. Your Neo mids blend well with the Maggie tweeter for 1st order but there is too much constructive interference with the Maggie mid and tweeter for this first order crossover. Would I spacing it more help? Another option is obviously to make the tweeter HP 2nd order as per MGIII spec and leave the mid LP first order, though you lose the linear phase and the imaging is less precise as a result.

 

RE: Are my ears really that sensitive?, posted on September 12, 2014 at 21:39:57
JBen
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 Davy, with the skills that you already have, plus good hearing, I suspect that you could do even better by adopting REW or similar measuring programs. This, to further monitor in-room acoustic behaviors. REW is free, and getting an adequate calibrated mic for a PC has become very inexpensive. This would offer you a higher degree of analytical options.

By careful listening and by careful measuring in-room acoustic outputs, I've had terrific results modding my MMGs & system along the years. We can't easily turn our homes into labs but that's the beauty. We can get the individualized, room-inclusive soundscape that takes us closest to our goals. I get the feeling that you could do monstrously well if you keep at it. Finer tools may make things more impressive still.

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 06:11:46
Davy
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 Thanks for the advice. I was going to ask about REW as it seems to be so popular. Will read up more and look for a calibrated mic. Do you really need a special, advanced sound card too or is that not absolutely necessary?

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 06:21:16
Davy
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 Was just thinking that rewiring the panels might not work as the magnet strength and/or magnet distance might not be the same between MGIII and MGIIIa. These models are coming up for 30 years old now so it might be hard to get info on that from Magnepan!, though I see it's also hard to get new information from them too!

I could give the extra inductor a go and/or adjust the existing ones in the mid/tweeter crossover. A bit fiddly but not that hard to do as I have a cheap Chinese inductance meter!

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 08:48:39
JBen
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 These days, newer sound cards -- even most of the motherboard-integrated ones -- are adequate for the acoustic measurements. There is more than enough headroom in terms of linearity, low distortion and good S/N for in-room takes.

So, for example, REW's ability to provide good comparative measurements of harmonic distortion in a room, are practical with almost any newer audio chip. The room + speakers figures are way over any normal electronic distortion. Yet, as long as one keeps the limitations in mind, some useful information can be gathered from comparing things "apples-to-apples". Absolute distortion figures without an anechoic environment are not achievable in our rooms. OTOH, comparing the distortions of, say "tweak A vs tweak B", can be quite revealing if done with care regarding environmental acoustic variables.

The same goes for finding some other kinds of distortion at the macro level, and this is quite useful. For example, some types of unseen damage to Maggies, or the impact of defective bias controls (as in crossover distortion in the amps) are not hard to see even with basic gear.

Some laptop built-in audio cards are tricky. The auto setups need to be bypassed. Yet, as long as the basic [laptop] quality is good, even the worst case I've seen can be made useful for many practical purposes.

Now, REW also allows a few measurements of the electronics at line level. For these, yes, you would want some of the better cards. These, for example, could allow meaningful stand-alone electronic distortion figures. In my case, an oldish E-mu 0404 USB that came with solid specs is normally used. The better internal add-on audio cards can do the trick also. With the growth of PC-based audiophile requirements, the overall quality of the audio electronics has improved greatly.

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 09:58:12
Satie
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 I was referring to the HP, you didn't show new changes in the LP.

The problem with the 18 6 (6 12) is likely phase difference between the tweeter and mids. you can flip the tweeter phase to get it entirely out of phase or go to 18 6 (6 6) again, or 18 6 (12 12) otherwise, you can move the tweeter HP further up to get the phase at the overlap region closer. You can tell better whether it is a phase issue by changing toe in. The Gann charts only show you the on axis equidistant theoretical response. At the 3khz range a 45 deg phase difference (6 vs 12 slopes) is a matter of 1/2" relative distance.

The original III spec (w/35 uF) really takes the mid out too high up and so reduces midbass.

If the stock IIIa alignment is generally better but for the peakiness in the top of the midrange, then you might just want to put a resistor in series with the midrange to lower its relative output. Or increase the resistor on the tweeter - but I think aligning the crossover for better FR is probably a better way.

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 10:06:18
Davy
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 Many thanks for the info, sound really good. I need to start using this. I bet there are lots of guides online to REW but is there anything specific you would recommend reading?

It's great that computer sound cards are probably ok for the job, or if not I could just get a 0404 USB. Had one before for use with the Hauptwerk organ system and they are pretty cheap. Guess I will have to find a place in the Uk selling a decent calibrated mic for the job.

In the meantime I was perhaps thinking a bit too far with the idea of putting an extra inductor in the midrange LP internal XO of my MGiiia. Another simpler solution might be an internal crossover more like the 20 or 20.1, increasing the existing midrange inductor to a higher value of around 0.7 to 1.1 mH. This would probably also help the 1-3 KHz peak. I can easily change the tweeter cap to 10 uF for this to be more like the MG 20 crossover. I'm not sure how this type of crossover would blend with the stock MGiiia external crossover though as that is 2nd order HP whereas the mg20/20.1 external is first order.

I already have some made up 0.74 mH inductors I could use for this so it very easy to try and see how it sounds.

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 10:40:31
Davy
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Joined: July 20, 2001
 Hi Satie,

Many thanks for the advice. I will try flipping the polarity of the tweeter in the present 18 6 (6 12) spec and see what happens. (I didn't think it would matter but seems I was wrong) Thanks also for the tip of trying the resistor too to reduce peakiness. Could be worth a go as well. Not sure if that would work well though as the bass is already quite strong in stock MGIIIa. It might swamp everything with the mid reduced.

Otherwise I had another idea which is quite easy to do. Going back to 18 12 (12 12) stock MGIIIa xo setup but then simply increasing the midrange series inductor from 0.4 to around 0.7 mH or higher. This is similar to the mg20/20.1 internal crossover and looks good for reducing that peak on the spreadsheet. I have some 0.74 inductor I could use for this. They use 18 awg wire not 16, but I guess it should be ok for testing purposes. The tweeter cap in the MGiiia is a 10 uF paralleled with 2uF so I could disable the 2uF cap easily to make it more like mg20 spec. I'm not totally sure how this would blend with the stock MGIIIa external 18/12 crossover as the MG20 external is 18/6

This is also very easy for me to try so I think it's worth a go. Certainly easier than adding an extra inductor on the mid LP making that 3rd order as that might take a lot of playing around with the values.

Yeah bit of a mystery how Magnepan got the original MGIII crossover sounding good with that kind of midrange suckout. The lower and upper bass are too sucked out for sure.

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 10:50:51
JBen
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 [my wife's got me shopping...or rather she shops and I sit on a aisle bench and pray...lol! This is me wriritng on phone while hooked to my PC via remote VPN. i have copied and pasted an earlier relevant post. ]

--start snip
...I mentioned that in recent times the availability of calibrated microphones has increased while the prices have come down. I have tested several units and they fare well vs my more expensive ones, at least for all practical purposes. In fact, the Dayton Audio iMM-6 Calibrated Measurement Microphone is less than $20 and works well with REW on PC/Mac (though it was originally designed for iPhones & Android). Look it up at Dayton (link below).

I wish I could offer a proper basic "how-to" but I am a bit short on time these days. ...count also on others who have similar experience to pitch in. You may also want to roam REW's forum on HometheaterShack.com

I do plan to place more emphasis on some practical examples of what can be achieved with REW or similar packages. Folks tend to become more motivated to learn when they see the usefulness.

Once they see how easy and practical it has become to measure, the real challenge is to remind them that some discipline helps achieve the best results.
---end snip

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 11:16:43
Davy
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 Thanks for the advice Satie. I replied but responded to the wrong post. My latest is above.

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 15:13:00
Satie
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 The option of raising the mid LP inductor from .4 to .7 mH is interesting, but may end up cutting you off too low- that is nearly an octave's worth - if you have something like 0.1-0.2 mH to add on to the 0.4 that might not be too drastic, but if you like what the simulation shows, go ahead - you already have the parts. I would not worry about the 18ga wire for now, as you say, it is good enough for experimentation.

As for reproducing the MG20 XO in the IIIa, I think that you can start with the top filters and change the 18/12 to 18/6 later on. It is just a wire snip and possibly a cap substitution. In my setup doing anything other than 1st order on the midrange is so disuptive to SQ that I just don't do it at all. The initial experimentation with the free midrange was incredibly instructive as to how good things can sound. I only added the filters because the amp and drivers needed protection from loud bass and in order to do away with the head in a vise problem due to low dispersion of the midrange beyond 6-8 khz.

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 16:32:41
Davy
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 Thanks for the advice. I've asked Roger to kindly run a simulation to check how 0.74 mH on the mid LP looks. I am hoping this is going to be an easy change to sort out the peakiness at 1-2 KHz. That inductor is 0.7 mH in the original mg20 (but with a 7uF parallel cap) and goes up to 1.12 mH in the MG20.1 (with a 12 uF parallel cap) though I guess the drivers are a bit different. The 20.1 (in particular) simulation does have quite a broad suckout centered around the prescence region. I can always unwind some inductor if 0.74 mH is too much and measure with my meter.

You are right it's v easy to change the external HP from 2nd to 1st order so I can do that later. The 18 12 bass to lower mid transition is quite good in the stock MGIIa XO. Better than it sounded with the stock bass HP in 18 6 so I think I'll try stock external first with this internal inductor change and it from there but I will definitely try both and see which one blends better.

The Neo 8 array must have great ability to be able to be run full range, but yes I guess it's sensible to protect it from bass and reduce the beaming problem in the upper mids/lower treble. I guess when it was run full range the lack of phase etc made things sound really good?

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 16:40:20
Davy
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 Thanks a lot for the info. Sounds very interesting. I can get that microphone you linked from Amazon UK ( double the price though!) . So I assume you just get an extension lead and plug it into the pc's (or soundcard's) mic input?

I will have to read up thanks for the advice I'll take a look at the Hometheatreshack site.
Is measuring FR and measuring distortion levels the most useful thing to use it for?

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 18:41:00
Davy
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 Been running some sims and things don't look too great increasing the mid LP inductor to 0.7 mH whilst running the stock external 18 12 setup with (with 3.5 mH inductor and 60uF caps on the external HP)
18 6 external with 60 uF HP caps looks better.

I think the problem I had with thinness increasing the external HP caps to from 35uF to 60uF with the first order external HP yesterday is that it increases the mid output meaning bass is less prominent. With a resistor on the mid it might work much better. The FR is quite flat with that particular config. When AndyR altered his MGIIa crossover he also had to use resistors so perhaps this is something to bear in mind. Increasing the caps higher to 75 or 90 looks even better but I'm not sure the mid would be happy running that low in first order.

If I used a resistor on the mid what wattage should I use? Several 10 watts in parallel or a much higher rating?

My other idea of adding an 2nd mid LP inductor to make it 3rd order won't work unless the present inductor is increased substantially in value, to 8mH or higher, whilst also increasing the parallel cap significantly to around 50uF. This is basically the 3.3 or 3.5 internal crossover setup. That's quite a bit of work.

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 22:55:35
Satie
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 I think the broad suckout may not play out that badly in the presence region since I suspect the sensitivity of the mid is possibly 1 db higher than the bass. So long as the depression on the gann chart is not deep it may not sound like it looks.

Re the Neo8, it is phenomenal in the range it covers and yes, the lack of phase is really a great plus. But doing things that way just leaves me without the ability to play as loud as I need.

 

RE: Are my ears really that sensitive?, posted on September 13, 2014 at 23:07:41
Satie
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 It is possible that the 60uF swap was making the lower mids (250-500 hz) too prominent and creating a dip from destructive interference lower down. If it is just a matter of mid prominence then you might get rid of the problem with a smallish resistor.

The resistor can be made of a few parallel 5 or 10 watters. You probably don't need any massive resistors like 50 watt rated ones that often have heat sinks.

I would not go to 3rd order in the mid or treble. It starts sounding rough.

Replicating the XO you built for the 3.3 or 3.5 is not necessarily a bad idea since you liked it all things considered. Your lower levels of playback are friendlier to the 1st order XO than my need to shatter glass with operatic sopranos.

 

RE: Are my ears really that sensitive?, posted on September 14, 2014 at 03:32:37
Davy
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Joined: July 20, 2001
 Thanks Satie. I think even with the new mid LP inductor value I'd still need to lower the midrange output level with a resistor. I see Andy used 30w resistors so that seems sensible.

Like I said I was not happy with the 18 6 6 6 crossover I put in the 3.3rs after not hearing it for a long time. Also way too much peakiness in the prescence region. It would need adjusting, maybe back to stock MGIII 18 6 6 12 (which actually worked well in them before, unlike in the iiia where the mid is too sucked out), or I might actually go back to the stock 18 12 18 12 crossover in them when I get the ribbon repaired. You are right things do start to sound a bit rough with third order on the mid LP but I would not mind trying it again anyway as it was designed for the speaker. Does not help that the cap Magnepan use in parallel on the mid LP is an electrolytic...

Wow you do listen loud. Front row of concert stuff! I remember that from before! Be careful with your hearing though!

Another option ( though it's harder to do as you have change all the values) are Bobwire's two 18 12 12 12 crossovers which are very flat. Much flatter than stock MG IIIa . I would probably want to introduce a slight dip in the prescence region if possible but I might play around with them in simulation to see. AndyR ran them in Lspcad for me a few years back and thought they looked extremely good. They might need the relative driver levels adjusting too.

 

RE: Are my ears really that sensitive?, posted on September 14, 2014 at 07:45:47
Davey
 You guys conversation makes my head hurt. :) This kind of tedious, iterative approach to tweaking is MUCH easier handled by a DSP-crossover and multiple amplifiers. You can experiment endlessly and ultimately come to a solution (if you're careful) that can be recreated with passive components.
And always remember, just looking at simulations of the electrical curves are limited in value when determining suckouts, peaks, phase responses, etc, etc. You MUST factor in the acoustic responses of the drivers and be skilled with an acoustic measuring acumen or it can be pointless.

Cheers,

Dave.

 

RE: Are my ears really that sensitive?, posted on September 14, 2014 at 08:13:47
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 This is true. We also need to know what kind of frequency response is prefered. Most of the DSP-systems available seems to think it is a straight line from 20-20000 Hz at the listening position we are aming for. It is not!

 

RE: Are my ears really that sensitive?, posted on September 14, 2014 at 10:38:33
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 We have competing goals in mind. These have to be weighed against each other and I (not so Davy) can't stand mediocre DACs such as those in DSP devices. Using them makes my subjective evaluation useless as I focus on the irritating sound they produce - all I can do is say "I don't want this". I can easily tolerate wow, noise, hum, non linear FR and peaky mids, bloated bass, or overcooked highs, I can take lots of phase issues, I shut down with bad digital.

Though I suggested all along that Davy use REW to do the characterization of the drivers (I did it on spreadsheets a decade ago with manual measurements for my drivers) and work things out on the computer, but he did not want to redesign the speakers from the drivers up, but to tweak them. I knew that is what I would have to do from the get go, Davy did not and still doesn't intend to.

Davy is very sensitive to coherence and has gone back from multiamping to single amping. Your solution is a design tool instead of a tweaking/fine tuning of the FR and phase issues. I don't think that within the limited scope of Davy's goals he would benefit from creating a DSP and multiamp setup he can't listen to. Not to speak of the learning curve in using the measurement and dsp software which would not be in place for his final product.

Neither Davy nor I intend to be professionals in this field but to tweak what we have. I kept an adjustable PLLXO/hybrid XO so that I can change things on the fly for recordings and experimentation with positioning (Limage and Rooze setups that do better with tweaking of the XO to complement them because of timing issues with something so large as the T IV).

I had done the mod TIV/Neo8 with Marchand's XO and had excellent results. I liked what I heard with the naked Neo8 array and attempted to use it that way for a couple of years, but the practical limitations drove me to rework the XO again with the constraint of having a 1st order XO for the midrange.

Davy is trying to iron out a peakiness in the top of the midrange that is the flaw in an otherwise fine speaker that he likes. An all out redesign assault on the speaker is not what he wants to do.

 

RE: Are my ears really that sensitive?, posted on September 14, 2014 at 11:08:44
Davey
 Yeah, I'm well aware of your sensitive ears and point-of-view on this, but if you can't listen past the sound of some digital circuitry to make relative evaluations it REALLY makes this sort of evaluation tedious and difficult. That's all I'm saying.

I can appreciate the learning curve of measurement, DSP-software, etc, etc, but eventually you get to a point with this hobby that you're forced to learn/utilize this stuff. You two guys are at (beyond) that point and seat-of-the-pantsing experimentation is a real double-edged sword.

If you're going to be a master auto technician, you need a complete set of tools......you can't do everything with a crescent wrench. :)

Cheers,

Dave.

 

RE: Are my ears really that sensitive?, posted on September 14, 2014 at 16:57:21
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Thanks for the input. I do kind of personally like plodding along, adjusting stuff slowly, even if its no the best way to do it. Guess it depends on what floats your boat. I am also however quite interested in your suggestions. Which DSP crossover(s) do you recommend?, seem to be quite a few out there.

From my (reasonably limited) experience I do think you can get some idea of the sound from the electrical response, and AndyR also agreed with me on this. I acknowledge it does not account for many other factors though (as you say), but obvious things like the big presence dip in the electrical response of the stock 3.3R crossover, or the presence peak on the MGIIIa or Stock Tymapni IVa are certainly audible to me.

 

RE: Are my ears really that sensitive?, posted on September 14, 2014 at 18:16:59
Davey
 My favorite currently is the miniDSP 4x10Hd. An extremely versatile unit that offers the ability to go 4-way, control your system volume, provides digital inputs, and a host of other features.

However, Satie would reject this unit out of hand. :) There's no satisfying some people. :)

Dave.

 

RE: Are my ears really that sensitive?, posted on September 14, 2014 at 23:35:42
JBen
Audiophile

Posts: 3082
Location: South FL
Joined: May 18, 2008
Contributor
  Since: July 26, 2010
 Davy, for this particular microphone to work on PC, laptop or sound cards you are going to need an adapter like what I link to at the bottom here. The mic has a thin male connector format like what iThings & Android phones use. The adapter separates the stereo mic and speaker feeds. You may also want to get a pair of long cables so you can use the mic anywhere in the room and also send a REW reference output to your audio gear. At the preamp (or power amp) end of this one, a set of male RCA terminations (adapters), can go to the AUX inputs, for example.

As to what REW is most useful for, it may depend on your needs at different points in time. For a long while, FR, group delay, phase and impulse measurements come in handy most of the time; but waterfalls not too often. Lately, since REW's harmonic distortion & IM distortion measurements have become more reliable in the past 2 years, I often find them very useful while testing the more radical tweaks.

I do many quick FR takes with the RTA, feeding or playing pink noise at the source. However, I can switch to the more informative sweeps very easily. This graph below shows a "quick and dirty" RTA from a few days ago. The PLLXO bi-amp here is set to run both drivers in "same polarity" (see that slight center dip?) which I prefer. (Incidentally, flat enough as it looks, I have actually "de-tuned" the settings. This is not exactly how I really listen but that's another story. )




One thing that I like very much about recent versions of REW is having up to 30 sweeps per file. It makes it easier to compare results. For example, back in 2012 someone had asked me what kind of difference could the line-level bi-amping be making. I found enough of the old original xover parts to restore them in the left MMG. This allowed me to tell a portion of the story with measurements; many actually, all in one file. And not just the a whole MMG but also of its separate drivers. (BTW, knowing individual driver behaviors can be pure gold when tweaking the Maggies.) This image below is an example.




The many sweeps in one file has another huge benefit for me. I can repeat the same sweep a few times when I have concerns about ambient noise intruding into a more critical set of reads. I live in hot South Florida, where A/C compressors' noise easily intrudes into measurements. I schedule most of the critical acoustical measurements for verification in the cooler months. In the warmer months...I sweep and re-sweep, LOL! The group delay comparison of the two settings shown before (old parts vs PLXXO) was repeated. That hot June summer, they still did overlap in 2 out of 3 sweeps. However, look what a starting compressor did at the bottom of the PLLXO (orange) in this one. At this low a frequency it may not seem to matter for the MMGs. Yet, it would, had this been real and not noise-induced like it really was. (There can normally be very faint but real acoutical output down to 32hz in mine and other tweaked MMG systems).





The other thing I like about REW it the ample space to add details about each sweep. I chose this slide below to demonstrate it for 3 reasons. One reason is that it shows the various facilities and options in the program. The 2nd reason is that you can see the space to add comments about an individual sweep. I tend to cram in a lot of details in each here when conducting tests with a long-term intent. One forgets key details easily...and almost everything is really "key"...

The 3rd reason is to show how important it is to consider the room's noise floor in many cases. The first sweeps that I showed at the top display a minor bass peak at right under 40hz from both MMGs. However, THAT ain't really by the MMGs. You will actually find it in the noise floor as recorded below. In fact, it is this same kind of noise peak that distorted the group delay sweep (PLLXO, orange) shown above, back in 2012.





Lastly, there are some of these same sweeps and tests that can be conducted at the line level instead of acoustically. One usually hooks up the output of the sound card to the input (loopback) and adjust signal levels. There are other tests that require a more elaborate hookup setup. Of all these, at least testing the soundcard with a loopback the first time around may be a wise thing to do. Most newer sound cards are good enough by default but one never knows...and it is not hard to make sure that they meet specs.

 

RE: Are my ears really that sensitive?, posted on September 15, 2014 at 10:36:10
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Thanks for very much info and graphs. Looks like a really useful tool indeed. I haven't had time yet to read the hometheatreshack guides but will do soon and also use what you've written here.

Just a quick question for now though. How does it measure the room noise floor?

 

RE: Are my ears really that sensitive?, posted on September 15, 2014 at 12:16:13
JBen
Audiophile

Posts: 3082
Location: South FL
Joined: May 18, 2008
Contributor
  Since: July 26, 2010
 The room & ambient noise floor can be done in at least 2 ways:
- In RTA mode while playing nothing, the mic is just listening to the background noise. In the case shown earlier, above, I asked the program to average 16 continuous samples (about as many seconds, I think). When compared to the pink noise reads in the RTA, there's good SPL correlation if using the same input gain settings. I may repeat this up to 3 times when I suspect there's too active an external environment. Approaching thunderstorms, hot days (A/C) and delivery trucks are the worst offenders. A nearby soccer park contributes with crowd and whistle noises during weekends and some evenings.

- In "sweeps mode" I let REW try taking a sweep but I turn off the power amps. The program records the noise anyway. Right now I am on coffee break. So, I just took the one below remotely while my wife watches TV (the mic is in place). The sound is from the small speakers on the TV, not the surround system. She reports that the program is "The Chew"...they are cooking some delicious stuff...and I can only have a miserable tasteless snack, LOL!



 

RE: Are my ears really that sensitive?, posted on September 15, 2014 at 13:16:25
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Hi Satie,

Sorry didn't see your post until now.
I hear what you say about the DSPs if they do degrade the sound somewhat. I know the older Behringer DXC2946 didgital crossover is very dated compared to modern DSP crossovers but I don't think I could have used that on the Maggie mid and tweeter to make subjective evaluations.

You are right, I am just tweaking what I have right now, and I freely admit that quite a bit of it is a shot in the dark, but I do quite enjoy that and eventually getting to something that works.

I do like single amp drive (being sensitive to coherence as you rightly say). Part of the trouble trying to get the drivers to blend well with biamping and triamping is having to do lots of experimentation with different power amps, crossover setups etc. That can take lot of time to get it to work well. For sound quality above anything else, PLLXO on the mid and treble is better than any active crossover in my view (and also better than single amp drive at speaker level), though it can be harder to blend PLLXOs with active bass due to delay issues etc. I might eventually go back to biamping or triamping in the future and really go for it and try to get something coherent, but for now I'm just tweaking the basic sound I've got with these MGIIIas in single amp drive. Ultimately I'm not sure if you'd ever quite the same degree of coherence of single amp speaker level passive drive with any multi amp setup, but with careful tweaking and matching I am sure you could get very close and also get the big advantages of biamping/triamping such as enhanced clarity and less distortion. I could likely also live with the latter.

Davey is likely right in that it could be easier and quicker to iron out the issue I am having with now, but only if I had the system set up already and knew what I was doing (and know how to transpose it well to passive components). The expensive of buying the DSP and more power amps along with the learning curve and time needed don't really make it viable for my situation right now (especially with single amp drive), but thanks for the advice Davey. It's certainly something I will bear in mind to try out in the future, especially if I do go back to a multiamp setup.

I will try flipping the tweeter polarity with the 18 6 (6 12) setup as per your suggestion now to see how that fares. Then think about the mid LP inductor change.

 

RE: Are my ears really that sensitive?, posted on September 16, 2014 at 04:46:23
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001



Ok I tried several things on the MGIIIas last night. I think I am slowly dialing things in.

With 60uF worth of external HP caps (first order filter) in the 18 6 (6 12) config I flipped the tweeter polarity as you suggested, and this did make the sound more to my liking, but it was a bit too sucked out in the presence region and lower treble.

So instead (still running 18 6 6 12 I put the polarity back (to + - + for the drivers) and increased the mid LP inductor from 0.4 to 0.72 mH. Obviously this spaces the mid/tweeter crossover more and brings down the XO point. This was better than flipping the tweeter polarity, but again things were too sucked out in the presence region. I think you are right, with a less drastic change, - maybe to 0.5 or 0.6 mH things might work well. Another additional thing which might help is to bring the tweeter XO down slightly by increasing the cap (and possibly reducing the tweeter inductor).

Anyway, the next move (with 0.72 mH mid inductor still installed) was to reconnect the parallel midrange 10 uF cap, going to 18 6 12 12 (MG20/20.1 type spec). This change the sound a lot and it did not sound as good as 18 6 6 12 in my opinion as the sound was much thinner and anaemic and the presence region was becoming more prominent. The midrange output had gone up significantly I think. Quite a bit of work would probably be needed to get 18 6 12 12 sounding better, - maybe increasing the Mid LP inductor more to around 1mH or higher (as in the 20.1). I did try decreasing the tweeter cap to 10 uF and that improved things slightly, but not enough. I think the midrange output is higher in 18 6 12 12 than 18 6 6 12.

So I think I'll go back to 18 6 6 12 and try to get that to work. I'll start unwinding the 0.72 mH inductors and go down slowly to around 0.5 to 0.6 mH. Might also try lowering the tweeter, and maybe try increasing the external HP from 60 uF to 70 uF or higher.

This is the electrical plot I am getting from the spreadsheet with 18 6 6 12, 70uF external HP, and 0.55 mH mid LP and the tweeter adjusted to 15uF and 0.4 mH parallel inductor (reduced from 0.7 mH). I can use the previously used 0.4 mH midrange inductor on the tweeter instead. The ribbon is still safe as its not going as low as it does in the 3.3, 3.5 or 3.6

The plot looks good, but one issue is that I have noticed is that when I change the tweeter crossover values on the spreadsheet, the midrange curve also changes. I guess this must be wrong. I am trying to get to grips with LSPCAD demo version instead (which is limited to 2 drivers, but still usable).

 

RE: Are my ears really that sensitive?, posted on September 16, 2014 at 14:19:39
Davy
Audiophile

Posts: 500
Location: London
Joined: July 20, 2001
 Sorry didn't see this earlier. Thanks a lot again for the info. Will bear all that in mind when I eventually use this great program.

 

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