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In Reply to: RE: So the mid-range fuse didn't save it? nt posted by macmagman on April 13, 2016 at 20:15:28
a few years ago, i had to sent my 3.6s in for a complete rebuild of the mid/woofers. the older bonding agent for wires to mylar are more prone to delaminating (and the effect of moisture) compared to the newer "glue". You may to give them a call to find out when they switched to the newer material. The assumption is that if you do need to sent it in, your repaired 20.1's will last many years . On the other hand, if you are driving your maggies hard, are you sure that your upper Sanders amp NEVER is driven to its max. From multiple Asylum discussions, you need about the same power to drive a mid/tweeter as is used for the bass panels....just sayin....
Follow Ups:
> > > you need about the same power to drive a mid/tweeter as is used for the bass panels < < < <
I probably wasn't paying attention when this was brought up in the past but I'd like to revisit this concept. I've got a pair of Emotiva XPA-1 mono blocks on each bass panel (high current, 1000 watts @ 4ohm), no way would I even consider my mids/tweeters getting pumped with those. I use a pair of UPA-1s which are about 400w ea @ 4ohm.
The reason I mention this is I just had a discussion with M3 Lover the other day regarding a pair of Parasound JC1s on the top end of my 20s and we both felt it would be a bit of an overkill. Although it would be possible to reduce the gain on my Marchand XO, I figure that would defeat the purpose.
Just my opine, YMMV.
The MAIN drive behind the 'how much power' question is Crossover Frequency. Full range requirements are certainly high. But, with the crossover used @line level, your amps are given QUITE a break and actually put out more power (apparent) 'in band'.
It gets a Little more comlicated with 3-way and up speakers or when you have a 2-way, like my 1.6 panels AND a sub.
Generally, the 50:50 point is considered to be 350hz. In NO case should the power to the bass end be less than maybe 30 to 40% of the total. If you crossed as high as 5000hz, you could easily make due with 100 watts for the highs given the kilowatt below crossover.
Too much is never enough
The mids of the 20-series will certainly not withstand hundreds of Watts without melting the Mylar. Remember the foli conductor is just 0.0005" x 0.1". They will also compress in its lower range as they cannot move very much air.
Those of you running 1000 W amps with Magnepan speakers. Have you ever measured how many Watts you really feed to the speakers? I would be surprised to see 1000 W in the bass, at least the in low bass where the fundmental resonance take up very much of the limited excursion.
Do foil conductors in the 20 series (0.0005" x 0.1") differ from those in the 3 series. If not it doesn't explain the failures in the 20.Xs. Additionally, there are probably fewer 20.s than 3.s in service.
Do the 20.s move less total 'corresponding' air than do 3.7s (or 3.7is) when given the same amount of 'juice', which might then tempt their owners to crank it up?
The 3.7/3.7i has different foil conductors, 0.001"x0.075". These can take more power. I am not sure if the 20-series mid have the thinner Mylar as the Tympani IVa had. Thinner Mylar will melt earlier/quicker. The mids of the 20-series are more "stressed" due to the lower cut-off frequency compared to the Tympani IVa.
The 20.1's are newer so delam is not an issue, but I was under the impression that the mid-tweeter took less power to drive than the bass, if what you stated is true would I be better off switching the amps and put the Magtech on the mid-tweeters? Or would I then be putting the bass panels in jeopardy? I have no way of knowing if I am in fact pushing the ESL too hard. I do drive them pretty hard that's why I have the set up that I do.
I think Magnepan switched to the new glue in 2004. You will need about the same power for bass and mid/tweeter. The mids are not very well protected as they operate at rather low frequences with a first order crossover. The mid foil conductor is thinner than any foil used for the QR-tweeters!
Thanks Roger,
that explains a lot, what's the use of having the fuse then? that's a poor design by Magnepan, I rarely blow midrange fuses, I've blown a few tweeter fuses but an exchange tweeter for $100 is one thing, seems that Magnepan want's to sell $1200 panels instead thats a VERY POOR business practice, and this is my second one!!
Would I be better off with the Magtech on the mid-tweeters until I can get a second one?
The midrange crossover freq and slope (1st order vs 2nd order in a few MG20.x and T4 iterations) is coupled with the lower mass mylar and thinner foil are related issues. The power handling of the midrange is reduced as you go down in mylar thickness and thinner foil/wire gauge. The lower crossover freq and lower order XO also reduce the midrange's robustness as it is allocated more of the lower frequency load.It is a long struggle of many planar makers to provide at the same time
1. higher power handling (higher XO, thicker mylar or tougher diaphragm like kaladex, Neo magnets and thicker foil)
2. higher resolution (thinner mylar thinner foil/wire, lower HP freq)
3. enhance coherence.. (lower XO freq so that midbass fundamentals are carried by the lower mass mids)Genesis and Infinity using BG RD75 or RD50 drivers or EMIMs with Al foil on Mylar, had provided the user with the option of adjusting the mid XO from appx 100hz for low output music to appx 200 hz for louder music. That provided better coherence and resolution at lower volumes and sufficient power handling at higher volumes.
I think magnepan had taken the crossover freq slightly too low and are facing the same problem that Genesis and Infinity reached and should have provided the loud playing user with the option of either switcing the speaker to a higher crossover freq. on the 20.1 or 20.7 or ordering the 20.7 with a higher XO freq.
Since the 20.1 can be crossed over electronically, the crossover can be switched to a higher freq (for both LP and HP) - following the Infinity and Genesis example I would suggest you do just that and put the XO freq up one octave. Very easy to do with a Marchand or Pass crossover.
For the 20.7 you can do exactly the same with internal mid HP cap halved and bass LP coil halved in either a replacement strategy or as a hot switchable option. That would allow playing at higher volume without burning your midrange drivers.
The solution I picked was to go out from the Mylar and ferrous magnet construction chosen by Infinity Magnepan and the BG RD series (and Wisdom) and go for a Neo8 line array that uses a polyamide or imide kaladex that can withstand higher temperatures and Neo magnets that allow a thinner metal foil. The result is higher sensitivity, higher ultimate output and higher resolution. As a result I gradually lowered my XO from the "just to be safe" 300hz 4th order to 250 hz 1st order and now even 150 hz 1st order. In an accident a few years back I clocked my mids running 126 db.
I don't know if the Neo8 line array is a solution for 20.1 owners even if the drivers were still available. The AMT Pro 8" drivers can't be driven as low as the Neo8 and will likely require 4-500hz high pass. Or 300 hz with a high order slope.
Edits: 04/15/16
Great info Satie;
But way over my head,I am using a Marchand XM44 my question to you would be should I back off on the high setting on it?
Get Phil at Marchand to build you new boards with the same slope but the crossover frequency (actually both HP and LP freq would be doubled) one octave higher, or keep the same crossover frequency but go for a steeper crossover - say a symmetrical LR4. Then you plug in the new boards and can play more loudly - and can swap back the original boards for low volume playback if you end up lacking detail with the new boards.
I would personally go for the LR4 choice since it is not that bad in a 2 way biamp setup and would allow you to keep an octave's worth of the midrange driver's higher resolution.
Thanks Satie;
I am pretty ignorant when it comes to the technical side of this hobby, Phil did send me some other boards.
This is what I have installed now 300HzHP6, and 135HzLP18
This is what he sent also 200HzHP24, and 200LP24
Using your suggestion translated with these numbers what do I ask Phil for?
Many thanks for all of your help....
Since you already have them, the 200 hz LP24 boards should help you by taking out low freq drive requirements from your mids. Plug those in and you should have less congestion in the midrange when playing hard and be less likely to burn them again.
If I were making fresh boards I would have taken 250 hz on a "just to be safe" driven choice.
Read how to replace the boards, it is easy but you need to do it correctly and plug the new LP board where the old one was and the HP board where the old HP board was.
For future improvement you will want to swap the caps on the boards with better foil caps as the LR24 have many of them so the difference in SQ is significant. .
Sure wish there was a way Phil could design the mother board to accept those mods so one could simply select them via selector switch on front rather than manually inserting them.
My complaint is the same - after desoldering and resoldering the boards so many times I was beginning to lose the loops on the circuit board. I was looking at vacuum and air variable capacitors to make changing freq and slope easy rather than deal with the potentiometers' familiar problems in transparency and tracking, but it seemed to have equivalent problems as the potentiometers and those are cheaper and far smaller in size. I used wire wound pots for the PLLXO for a while.
the cards on these boards are fairly small. See pix on link below of an example. you mention foils to mod the cards, what specific foils have you tried that will fit the cards and could you elaborate on the actual audible improvements. I have added a link to this topic from the past.
thanks image link http://www.canuckaudiomart.com/details/649258631-marchand-xm44-crossover/images/1175005/
Edits: 04/16/16 04/16/16
were first of all in smoothness at the top end while retaining the sparkle on high hats triangle and the metallic sheen of brass, just that these were now more realistic and less electronic sounding. The second was that it sounded fuller in the mids when the bandpass boards were done. The slight bit of upper mid/low treble shrillness was gone as was the slight thinness in tone. Imaging improved, particularly in the depth dimension and it tightened the bass a bit further.
I used mostly 0.01 uF Dayton foils but also RTE polystyrenes and platinum caps from sonicap.
I used both sides of the boards to get the real estate required. Smaller values would be easier to fit on one side. But the smallest Dayton foil is 0.01uF and that is the best value in foil caps.Absolute results are just a notch or two below the best foils from Jantzen and Duelund.
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