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DMW

76.112.209.8
Posted on March 9, 2017 at 19:13:55
timm
Audiophile

Posts: 780
Location: Ann Arbor Mi
Joined: January 15, 2008
 Hi all.

Has anyone tried dual DMWs with a 3.7 or 20 series? There was an article written that the 3.7+ dual DMWs would go down to mid 20 Hz. I'm not sure how this phenomenon occurs. Just wondered if anyone has experienced it. Thanks Tim

 

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     RE: DMW - finbad 15:28:22 03/16/17 (3)
       RE: DMW - timm 15:33:37 03/16/17 (2)
         RE: DMW - finbad 18:47:49 03/17/17 (0)
    ...
RE: DMW, posted on March 16, 2017 at 15:28:22
finbad
Audiophile

Posts: 62
Location: St. Pete Beach
Joined: September 29, 2016
 I'll be picking up a courtesy pair of DMW's from my dealer tomorrow as a four day trial to be integrated with these 3.7i - Will report back my findings .

Magtech or Halo A21 driven.

I have great hopes the endeavor will be satisfactory that I will be able to forgo a Rhythmic F15HP w/ H600PEQ3 amp Sub as my other option in consideration .

I'm finding the Sanders Magtech being relatively bass light vs the A21 consistently with all variable sources here . This was an unexpected revelation with the said to be neutral Magtech vs what I knew was a slightly warm Parasound and now known to be a tipped up lower end , though articulate . Though on a few recordings its lower end could impart a tube amp-like bloom .

In any event I would like to experience the DMW's in my room and my dealer agreed .

- Stay tuned (cheap pun;')

I will research what I can about placement , and perhaps options here.

 

RE: DMW, posted on March 16, 2017 at 15:33:37
timm
Audiophile

Posts: 780
Location: Ann Arbor Mi
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 Very cool. Surprised about the magtech. What pre do you have?

 

RE: DMW, posted on March 17, 2017 at 18:47:49
finbad
Audiophile

Posts: 62
Location: St. Pete Beach
Joined: September 29, 2016
 Thing is, I ran direct out of Aurender A-10 Musi server hard drive / 120 solid state drive - Very respectable DAC section(s) integration with high ReZ downloads , with also as well matched / integrated , easily as impressive if not betters this Auralic Vega DAC which is quite dry though highly accurate and relatively smaller sounding too , in terms of soundstaging, wider than the 10" off sidewalls .

Also direct from CD v. Oppos 103 / 105 - or Aurender A-10's 96 - 128 in catalog amongst 4 Terabits of space .

Nice thing with the Maggies of course, in finding the voicing nuances of Comparable components .

I now have the DMW panels in place without resistors , 19" forward of Mains & 90 degrees butted to SW - Mains 18" off SW and 7'4" v 7' toe-in , tweets inboard.

- Subtle improvements as advertised , very subtle fatter tone in this first listen position fronted by the A-21 and A-10 unbalanced ,to begin.

Satie, I proposed the same wonder to my dealer, that is if the A-21 running out of steam accounts for its bass affects v the Magtech (ran now for 3 weeks) seemingly "needing" the DMW's stated purpose.

-Stay tuned

 

RE: DMW, posted on March 17, 2017 at 11:40:26
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 Finbad's profile lists Audio Research Tube LineStage - 17se

Surprised that the deliberate warmth on the A21 is not subtle. The Magtech should have had better bass performance given the greater current capacity and much higher rating and a 2kw peak draw. Perhaps it is how well the Magtech damps the stiff bass diaphragm, producing tighter bass while the A21 might come out looser but louder?.

 

RE: DMW, posted on March 11, 2017 at 14:18:23
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 As others have pointed out, what appears to happen is that the panels couple acoustically, creating a larger baffle, and to the proximate side wall as well. In some cases, this reduces dipole cancellation, increasing bass output and extension.

The magnitude of the effect depends on room and setup, which is why Magnepan doesn't advertise it -- it works in their listening room, and it apparently worked in Chris Martens', but Magnepan has no way of knowing whether it will work in yours. I would think that proximity of your mains to the sidewalls is important.

If you're using a model that goes lower than the DWM's, you could model it by making two barriers the size of the DWM and placing them between your speakers and the sidewall, then measuring with the barriers in different positions. A full height barrier that completely coupled the speaker to the wall would give you a 6 dB increase in bass output. These barriers aren't full height, but then, most of the lowest frequencies are produced at the bottom of the Maggie, so a DWM-height barrier may have a disproportionately large effect. (Remember when visualizing this to think of the floor and walls as mirrors -- any baffle is "reflected" and becomes twice as wide or tall.)

 

RE: DMW, posted on March 12, 2017 at 04:38:20
Swamis Cat
Audiophile

Posts: 272
Location: Illinois
Joined: September 7, 2013
 Josh,

Nobody is denying that it increases bass output. I am denying that it makes any material difference in low end extension in any room I have tried it in. I have measured it in three different rooms with countless set ups and two different sets of main speakers.

If you have measured the differences objectively then share your data. Seriously, exactly how much extra gain did you get with DWMs added at 32 or 40 hz? I will share my number and it rounds to zero. Please share your numbers with us.

 

RE: DMW, posted on March 12, 2017 at 07:03:15
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 I didn't try it myself, this is what Wendell found when he was first experimenting with the DWM/large maggie combination. (I'm using a barrier now on my left woofer panel to bridge a gap caused by a radiator and there is a lot of bass reinforcement since not only does it extend baffle width it gives me the full 6 dB dB of proximity gain, but that isn't sufficiently analogous since it runs about 2/3 the length of a speaker and there are no large gaps between it and the wall.)

IIRC, Wendell was astonished to discover while tweaking the DWM arrangement at an audio show that he was measuring response into the 20's from two speakers that didn't go that low, so when he got back to Magnepan, he conducted some experiments in the listening room at Magnepan and was able to reproduce the phenomenon and modulate the effect by moving the DWM in an arc between the speaker and the wall. However, since the effect was room and setup dependent, they couldn't use it as a specification or selling point.

I don't know why specifically it worked in Christ Martens' and Magnepan's setups but not the ones you tried -- it would be interesting to find out.

 

RE: DMW, posted on March 12, 2017 at 10:58:29
Roger Gustavsson
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Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 If you add another bass driver with a similar response, it will not change the extension but it will for sure add more bass.

 

RE: DMW, posted on March 12, 2017 at 13:58:26
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 I think there are several effects here. One, the additional driver will increase bass levels and if the two speakers have similar low frequency cutoffs (not at all certain) that in and of itself will lower the frequency of the 3 dB point, so give you a bit more bass extension. Two, the coupling of the two baffles which will increase baffle area. This will have the effect of reducing the frequency at which the 6 dB/octave rolloff begins and that will increase bass extension.

Of course, the baffle itself is a complex shape and reflections from the room surfaces have to be taken into account as well, so it's really more complex than that. But suffice it to say that adding baffle area will lower the 3 dB point, as long as it's near enough to couple effectively, and that the baffles themselves will interact with their reflections in proximate surfaces, possibly resulting in a disproportionate increase in bass output and extension if the large speaker is coupled to the wall by the smaller speaker -- keeping in mind that the deepest bass is emitted at the bottom of the speaker where the lowest resonance segment is. This assumes that the diaphgrams will impede bass frequencies effectively despite the fact that they're underdamped. Since they are, there may also be some resonant coupling between drivers.

As I see it, anyway -- it's others who have measured the effect, I'm just trying to account for it.

 

RE: DMW, posted on March 12, 2017 at 18:12:57
zulugone
Audiophile

Posts: 98
Location: Seattle, Washington
Joined: August 31, 2013






I don't want to reorganize my room to repeat my DWM experiments from years ago but here are a couple of REW sweeps I took today both without any smoothing and with the sub off. The key in the first is the level at 60 db. That shelf drops off at 24 HZ and moving the 1.7s +DWMs around can move that level much higher. The second is just a sweep with the mic as close to the rear wall as I could get it which just illustrates some more extension below 40 HZ. Earlier some one mentioned a 'big German amp' with a 'grip' issue. My little 1.7s +DWMs in parallel run steady just below 2 ohms. Crown amps are unaffected. I also got more extension from the DWM by using DSP to cut them off above 50 HZ.

 

RE: DMW, posted on March 13, 2017 at 17:10:58
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Most interesting, thanks. A great illustration of how sensitive low frequency reproduction is to setup and the room!

 

RE: DMW, posted on March 11, 2017 at 09:49:22
timm
Audiophile

Posts: 780
Location: Ann Arbor Mi
Joined: January 15, 2008
 Interesting topic to me at least!! :). Yah when I read that I was skeptical. I was looking for real live experience mixed in with a little science. You guys are great.

 

RE: DMW, posted on March 11, 2017 at 07:51:50
zulugone
Audiophile

Posts: 98
Location: Seattle, Washington
Joined: August 31, 2013
 I have 1.7s with a pair of DWM. In my current more or less permanent setup they only improve mid bass per Swamis Cat. Without the DWM REW shows mid bass with lower SPL and a more ragged response curve. DWMs improves the curve depending on their position relative to the 1.7s and the room. They can make the curve worse depending on positioning. The difference heard is audible depending on the recording.

I have used the DWM to get high SPL down to 24 HZ. This depends on how all four speakers are set up relative to each other,the walls and the listening position and in my case on having separate amps for the DWM. Overall I didn't get the best sound with this setup and went to my current positioning with a Rythmik sub for below 40 HZ.

 

RE: DMW, posted on March 11, 2017 at 08:20:51
Swamis Cat
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Posts: 272
Location: Illinois
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 Exactly! As Zulu mentions, the DWMs can be positioned to accentuate or smooth bass response in the mid bass and even the lower midrange.

I have had two for years, and I usually have them running to help mid and upper bass. However, in some positions, the bass is already full and smooth, in which case I put the bass panels away. In no case have they ever made the slightest difference even as low as 50 hz. If Wendell or someone else at Magnepan suggests differently, I would love to see their before and after measurements.

If you want more lower bass the only options (assuming optimal placement) are either subs or a different model of Maggies, such as the 20 series or an older set of 3's prior to the shift to larger midrange panels.

 

RE: DMW, posted on March 10, 2017 at 17:02:31
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 The DWMs and speakers couple together in the deep bass frequencies so long as they are closer than the 1/2 wavelength and roughly in phase. If the speakers and DWMs are spread out within 13 ft they should couple below 40hz and you get a slower roll off. It would not be outlandish to expect something below 30 hz to be well within audible range.

 

RE: DMW, posted on March 10, 2017 at 20:47:10
timm
Audiophile

Posts: 780
Location: Ann Arbor Mi
Joined: January 15, 2008
 So I am wondering. Given that the frequency would drop in the 20s do you believe this type of setup would pressurize a room equal to or better than the 20.7? I assume people that purchase Maggie's love planar bass. It seems this would be an excellent option at a very affordable cost assuming amplification is covered for the DMWs.

 

RE: DMW, posted on March 11, 2017 at 06:06:47
Satie
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Posts: 5426
Joined: July 6, 2002
 No. The DWMs will not give you 20.7 quality bass, nor extension. Nor would they match a Tympani IVa. What they will do is provide audible extension below the resonance freq.

As Roger noted planars don't actually "pressurize" a room the way a sealed dynamic speaker would, but given sufficient power you can get deep powerful impactful tight and dynamic bass. The bigger the speaker and the more DWMs the more bass output and extension you get.

If you want big planar bass cheap then build a frame to take a stack of used MMGs - take their buttons out and bypass/disconnect the tweeters 4 or 5 MMGs per side stacked sideways should give you more bass than you can imagine. Same if you do this with a stack of DWMs just that it is a more costly option.

 

RE: DMW, posted on March 11, 2017 at 08:29:48
Davey
 You can't remove the buttons......and you wouldn't want to even if you could. The speakers would sound horrible.

Dave.

 

RE: DMW, posted on March 12, 2017 at 12:57:01
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 Just for use as bass panels. Think planar subwoofer.

 

RE: DMW, posted on March 13, 2017 at 08:30:36
Davey
 Yeah, usage just as bass panels is what I was talking about.

Dave.

 

RE: DMW, posted on March 11, 2017 at 04:28:22
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 Dipol speakers will not pressurize a room. I still do not believe you get anything like flat to 20 Hz from any setup of Magnepan speakers. The roll-off below the lowest resonant frequency will be there and there is almost no room gain from a dipol.

 

RE: DMW, posted on March 11, 2017 at 14:04:46
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 What apparently happens is that the baffles and proximate sidewall couple, shifting Fequal, so the 3 dB point really can move lower than it otherwise would. But the effect is room and setup dependent, which is why Magnepan makes no claims -- it's basically a fortuitous occurrence that surprised them when they first discovered it.

 

RE: DMW, posted on March 10, 2017 at 02:42:36
Roger Gustavsson
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Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 That is strange because both drop below about 45 Hz by 18 dB/octave. Not even the MG 20/20.1/20.7 will do 20 Hz without drop.

 

RE: DMW, posted on March 10, 2017 at 05:48:00
timm
Audiophile

Posts: 780
Location: Ann Arbor Mi
Joined: January 15, 2008
 Well right... I agree.... that is why I bring it up... Chris Martens apparently wrote something about it.... I asked on another forum and was told 'it was physics'.... the 'superposition principle'.... and I wondered if anyone had actually tried this..... To me... 40Hz + 40Hz just equals a louder 40Hz.... But, I'm not a physicist... :)

In the article he claims 25Hz..... using dual DMWs with the 3.7...... So- I would think someone has tried this at home??

 

physics, posted on March 10, 2017 at 14:26:38
DrChaos
Audiophile

Posts: 2063
Location: San Diego
Joined: July 13, 2009
 Because the bass wavelengths are of some order as speaker to speaker distance, it works.

There is not a hard cutoff at 40 Hz, just a roll off. After all, a small headphone driver can make 20 Hz sound, just not a lot of it.

 

RE: physics, posted on March 11, 2017 at 21:38:37
Green Lantern
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Contributor
  Since: June 17, 2003
 excellent headphone analogy -









 

RE: physics, posted on March 11, 2017 at 07:09:43
Swamis Cat
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Posts: 272
Location: Illinois
Joined: September 7, 2013
 I have twin DWM's and must disagree with the above. They do absolutely NOTHING, zero, nada, zilch at extending the lower bass of the panels. I have tested them in several different rooms in hundreds of configurations, and in every case all they do is accentuate the range from 63 to 300 hz. They are mid and upper bass accentuation devices. Indeed, they hardly even make a difference at 63.

 

RE: "extending the lower bass of the panels" ..., posted on March 11, 2017 at 15:53:44
andyr
Manufacturer

Posts: 12548
Location: Melbourne
Joined: September 2, 2000
 I heard a pair of DWMs with 20.7s in a very large room. They were set up by the dealer and it was not a success ... although the owner of the 20.7s was using a huge German amplifier to drive them, when the DWMs were also driven by the amp ... it no longer had the grip to drive them.

But the dealer explained that the main use of DWMs was to get bass pressurising the room from other positions in the room (than the 20.7 bass panels) - to smooth out the bass - not to deliver low bass. So his idea was the same as yours.

Andy

 

RE: "extending the lower bass of the panels" ..., posted on March 13, 2017 at 23:53:43
Roger Gustavsson
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Posts: 2054
Location: Huskvarna
Joined: February 12, 2010

The owner of these 20.7 is complaining about lack of power below 50 Hz. A while ago he got some 40 year old Tympani IIIA basses to work with.

 

RE: "extending the lower bass of the panels" ..., posted on March 28, 2017 at 13:01:22
josh358
Industry Professional

Posts: 12332
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 It's a beautiful room, but a terrible one for line sources (and probably anything else, but mostly line sources). Line sources want a ceiling, they depend on the reflections from ceiling and floor to approximate an infinite line.

 

RE: "extending the lower bass of the panels" ..., posted on March 28, 2017 at 22:27:54
Roger Gustavsson
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 So why do peoble use sound deadening ceiling panels? It is not common here in Europe and most acoustic Consultants do not recommend them except for placement just behind/above conventional radiating speakers.

 

RE: "extending the lower bass of the panels" ..., posted on March 30, 2017 at 11:44:52
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 With boxes, you'd normally put absorption on the ceiling at the first reflection point, which is to say a bit in front of the speaker. I'm not sure why anyone would want to do more than that, unless they're trying to lower the Rt of the room and they can't use the side or front and rear walls or perhaps if they want to suppress the reflection to a lower frequency, which wouldn't be bad except that there's a risk with a large area of making the room too dead.

Full-length dipoles are entirely different and you really don't need absorption on the ceiling or floor, or want it at frequencies at which wavelength becomes large compared to driver height.

 

RE: "extending the lower bass of the panels" ..., posted on March 18, 2017 at 05:50:00
Green Lantern
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Contributor
  Since: June 17, 2003
 Interesting room; great looking setup. I have what many may consider a modest setup powered by modest components. Dual XPA-1 mono amps on the bottom of my MG20r cranks out 'enormous' bass; so much I have to turn down the low gains on my Marchand XM44 to #2 on the dial. Neither muddled nor boomy, but nice and controled bass. I hesitate to use the word 'tight' since my room isn't acoustically setup for correct bass response (yet).

Now what I'm about to say will raise a few eyebrows but here it goes: I'm convinced my 20s have hit 20hz-30hz at times (yes you read that right!) I'm only speculating since I don't have equipment to measure such. But I've never heard bass reach as low and controlled even with past subwoofers I've owned. Keep in mind this doesn't happen frequently at that level, in fact only once or twice and I also feel it's source specific- meaning if your album, cd doesn't send it, Maggies won't receive it. My jaw dropper source is John Barry's "Dances with wolves" soundtrack, "Main Title - Looks Like a Suicide". Out of nowhere a kettle drum kicks in and lays a blanket of bass so deep it literally -if only momentarily, reaches into the bottom of your soul.

Room and engine(s) dictate such; and high current is the key. I had a single Krell KSA 200 that couldn't do it; whereas these Emotivas handle it with ease.









 

RE: "extending the lower bass of the panels" ..., posted on March 18, 2017 at 11:31:23
Roger Gustavsson
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Location: Huskvarna
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Stereophile measured this.

 

RE: "extending the lower bass of the panels" ..., posted on March 18, 2017 at 06:26:37
josh358
Industry Professional

Posts: 12332
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 The 20.7's definitely can go down that low.

Also, if your XPA-1's are like my XPA-2 was, they have a wooly, prominent midbass compared to my A-21. I have no idea why that should be the case since they both have high damping factors and they're feeding a mostly non-reactive load. There shouldn't be a difference, but there is.

Some sonic differences are easy to explain -- crossover notch distortion, harmonic distortion spectrum, impedance interaction, instability, RFI -- but I continue to be mystified by some of the differences that I hear.

 

RE: "extending the lower bass of the panels" ..., posted on March 18, 2017 at 16:14:50
Satie
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Posts: 5426
Joined: July 6, 2002
 I think the key difference is in the Marchand XO vs. the maggie speaker level XO box. The XPA might have a better time driving the panel direct rather than dealing with the XO box's reactance.

My own experience was that the XO box is woolly sounding. All the amps I tried on the bass panels sounded much more extended and tight without the XO box. I also tried the bass panels as full range speakers out of curiosity. Even the Crown 5002 sounded woollier with the speaker level XO box. But it definitely sounded worlds ahead of the Bryston 4BNRB Classe DR9 whether in stereo or bridged mono and Nuforce 8b .

No problem believing that you get audible 20-30 hz content, particularly with some wall loading. Wall loading the T IV bass panels and bracing them brings out organ foot pedal fundamentals that are inaudible without wall loading and weak without bracing.

The Stereophile bass measurements are done at close proximity so don't show what it actually sounds like in the far field - where room modes also come in. My own 1m measurements show a resonance at 30'ish hz. But the particular frequency changes with the angle between the panels, appearing lowest when the panels are flat and face forwards. all this from memory as this was done over a decade ago and the PC used for it is long dead without a full backup.

 

RE: "extending the lower bass of the panels" ..., posted on March 18, 2017 at 19:52:00
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Without looking at the schematic (too late, I'm about to head for bed) I'm guessing that the issue with the passive XO is that the amp isn't seeing the driver above the crossover point and is losing electrical damping as a result. But that doesn't explain why the amp would make a difference. So -- it might have something to do with the amp's ability to deal with the back EMF. But I'm not sure why that would be an issue, since these amps generally have plenty of reserve unless you're really cranking them, and the feedback loop of a modern amp should have enough bandwidth and slew rate. And I don't think the harmonic spectrum would have that much of an effect.

Really, there is something going on here that I don't understand from an engineering perspective -- not just the wooly bass but the different ways amplifers handle the ADSR envelope/20 dB transients on piano etc. This stuff isn't happening at a high frequency, but at a very low one.

These Stereophile measurements say they were taken at 100", so it isn't near field. But they say anechoic. Don't have the original review and I was wondering what the setup was. Were they done outside? Did they try to take a quasi-anechoic gated measurement at 100", which you *can't* do with a line source unless you measure it in a room the size of a gymnasium? In any case, as you say, the only meaningful measurement of the bass response of a dipole is in a room, because you have cancellation from the rear wave reflection. And that of course is going to vary widely depending on room and setup -- as bass always does.

Reminds me that I have to measure my IVA's in their new position . . .

 

RE: "extending the lower bass of the panels" ..., posted on March 19, 2017 at 11:56:53
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 The caption says the bass was measured separately below 300 hz in "quasi anechoic" conditions which is long form for near field.

The speaker level XO should reduce the damping available from the amp. At least vs. not having it in the way.

The transient dynamics are a matter of power supply and the IV curves of the output devices. Pass points out somewhere in his white papers that besides power supply sag the output devices are just not linear outside the narrow range at their center where the IV curve is straight. so he chooses where to operate the output devices to get the least compression and then to make that compression come off as naturally as the drop off of SPL in air. That way he is thinking that the effect would be similar to sitting a bit further away from the sound source rather than being perceived as drooping output.
Pass also discusses the effects of transformer saturation. The effect is compression of dynamics and he gauged its audible effect by using two giant spools of magnet wire on pallets .stacked on top of each other as an air core transformer for the same amp design. There he noted how it differed in there being a lack of compression, among other things. He then lamented the impracticality of air core transformers since they would be as big as speakers beyond a few watts and be entirely immobile..

 

RE: "extending the lower bass of the panels" ..., posted on March 30, 2017 at 14:14:08
pictureguy
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Posts: 22597
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 I'd say, just off hand, that maggies don't store enough energy for amp damping to be a Huge Factor.


Too much is never enough

 

RE: "extending the lower bass of the panels" ..., posted on April 20, 2017 at 03:28:34
Roger Gustavsson
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Posts: 2054
Location: Huskvarna
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 Remember this room?
http://i331.photobucket.com/albums/l454/cmbfoto/_P0F5690.jpg

It is now slightly different, Tympani IIIA Bass Speaker added.
http://tinyurl.com/lwxdcwh

 

RE: "extending the lower bass of the panels" ..., posted on April 20, 2017 at 11:40:42
Satie
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 Any idea how those are crossed over?

I see he is using the new concentric U profile diffusers. They really took off recently.

 

RE: "extending the lower bass of the panels" ..., posted on April 21, 2017 at 03:09:32
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 Originally his room housed some conventional box speakers. In order to tame them the room was filled with a lot of Svanå Diffusors. After switching to Magnepan 3.7 and later on to 20.7, the room has been changed a couple of times. The side walls are now without most of the diffusors, the wall behind the speakers have them partially coverd with absorbers from Sounds of Silence (http://www.sofsci.com/). The transparent diffusors are from Svanå (http://www.diffusor.com/). The Tympani Bass Speakers are driven by a LAB poweramp with built-in crossover (maybe even DSP).

 

RE: "extending the lower bass of the panels" ..., posted on April 22, 2017 at 07:36:17
Norman M
 Yikes! I'm having a somewhat difficult time believing a 20.7 is that deficient in delivering "lower bass" that it needs to be supplemented by four Tympani Bass panels. Perhaps their individual total bass output has been adjusted (by use of a X-O of some type?) to meet the task. Nevertheless, just too much of a good thing?

 

RE: "extending the lower bass of the panels" ..., posted on April 22, 2017 at 12:56:10
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 The panels couple together. So having them as an add on increases lower freq output and extension beyond that of either set.. Besides which the T III bass panels are likely crossed over in the vicinity of 50hz while the 20.7 likely play full range.

 

RE: "extending the lower bass of the panels" ..., posted on April 22, 2017 at 19:50:16
Norman M
 Thanks Satie, points taken.

 

RE: "extending the lower bass of the panels" ..., posted on March 20, 2017 at 16:20:10
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 They spec'd the measurement at 100", though. That isn't near field. And if they tried to gate it at that distance to make it quasi-anechoic, they screwed up *unless* they were outside or in a huge space in which the reflections were outside the window.

Some other wrinkles -- if the gating is too short, you won't get a contribution from the full height of the line source or the floor and ceiling reflections that you do want. And if you do it outside, you won't get a contribution from the ceiling reflections.

Just very hard for these reasons to do meaningful quasi-anechoic or even anechoic of a planar. What counts is the in-room response -- and then you have to accept that bass levels vary widely between rooms and speaker/listening position.

Sounds like an interesting white paper. I remember Pass saying that he tries to mimic the harmonic distortion of the air but I'm afraid I'm missing the effect of device linearity -- that's what feedback is for. Of course you'll hear effects of feedback such as the adverse effect on the harmonic spectrum, but I'd expect the feedback to take care of obvious effects of the magnitude I was hearing. That I think is too high for the harmonic distortion spectrum of a modern amp, usually what I hear of harmonics is subtle except for crossover notch distortion and this didn't sound like that to me.

 

RE: "extending the lower bass of the panels" ..., posted on March 21, 2017 at 08:27:12
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 They say it is nearfield right on the caption. That is how they get "quasi anechoic" in the bass. Atkinson details these measurements somewhere on the Stereophile website.

Part of Pass' philosophy is to avoid using too much feedback, so he can't rely on it to entirely flatten out non linearities in the output devices. He is mainly avoiding high order odd harmonics so far as I understand it and that relates to the HD spectrum in air - which does not contain those. And his DIY projects going into the First Watt concept also try to avoid time domain issues due to overly aggressive feedback, which is something he also worked into his "regular" AB and Class A amps.

 

RE: "extending the lower bass of the panels" ..., posted on March 28, 2017 at 13:13:17
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 He's wrong, though. For the typical planar, 100" isn't near field, it's medium field -- on the border of the near and far field, which is to say it's near field at some frequencies, far field at others. This is very apparent when you look at a plot of dispersion as a function of both distance and frequency.

"Quasi anechoic" just means the measurement has been gated to suppress room reflections and at that distance in the typical room you *can't* gate out the reflections. Unless he measured outdoors, but then it would likely be described as an outdoor measurement and would include the reflections from the ground -- which are actually crucial to the LF response of a dipole since they effectively double the baffle size.

I seem to remember having read Pass on the harmonic distortion of the air some years back. The man is an artist. On the other hand, high order harmonics sound more dissonant and have to be weighted in a harmonic distortion measurement because they're a good deal more audible. One of the main arguments against high levels of negative feedback is that the distortion spectrum changes to emphasize higher-order harmonics. They really should dispense with THD and use the formulas for audibility to create a meaningful weighted measurement. It would take into account both the relative audibility of the harmonics and the Fletcher-Munson curves.

 

RE: "extending the lower bass of the panels" ..., posted on March 19, 2017 at 04:38:08
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 I have seen in-room measurements of the MG 20, 20.1 and 20.7. There use to be a drop in the lowest octave. They cannot simply move that much air. My Tympani IIIA basses are similar, the lowest resonant frequency is 33-34 Hz and from there it drops by about 18 dB/octave. The 3.6 I am using today are also driven by an active crossover and four channels of power amplification. They are not doing much below 40 Hz. Maybe I have to continue my modification of the Tympani IVa...

PS. Kettle drums = timpany? Timpany is playing at higher frequences, from about 55 Hz and upwards. What you hear in that track is the orchestral bass drum at about 35 Hz or so. Here an analysis of that track.

http://www.forumbilder.com/image/E85

 

RE: "extending the lower bass of the panels" ..., posted on March 19, 2017 at 06:14:00
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 The room reinforcement from early front wall reflections would reinforce the bass by 3 dB at half a wavelength path length difference, so if the speakers are 5' from the front wall you'd get cancellation at 100 Hz (10' wavelength and path length) and reinforcement at about 50 Hz (20' wavelength and 10' path length) rather than the bottom octave. At 20 Hz you're talking a 50' wavelength so you'll get a fair degree of cancellation from a 108 degree net phase shift. So it seems to me that a very effective bass trap could potentially increase bottom octave response, though of course it will ultimately be limited by the woofer's resonance.

I didn't see much bottom octave bass when I measured my IVA's but there are two important caveats -- I've moved them and there's delam on the lowest frequency resonant sections. So the measurements probably aren't meaningful and since I'm in the middle of some long-overdue Ebay selling it's going to be a few days before I have a chance to take some new measurements (as a matter of curiosity, I want to compare the response before and after the delamination is repaired).





 

RE: "extending the lower bass of the panels" ..., posted on March 19, 2017 at 07:58:22
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 I think it is a complex mix of reinforcement and cancellation from reflections. Not only from the wall behind and beside the speakers but also from the area around the listening posistion.

 

RE: "extending the lower bass of the panels" ..., posted on March 19, 2017 at 08:11:30
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Definitely. A room mode calculator will predict what happens pretty well for a rectangular room if you remember that with dipoles, a node is an antinode and vice-versa, and that dipoles excite fewer modes than omnis because of the dipole null, which I think is one of the main pluses for planar bass.

 

RE: "extending the lower bass of the panels" ..., posted on March 20, 2017 at 22:01:38
BDP24
Audiophile

Posts: 1070
Location: Vancouver, Washington
Joined: September 12, 2013
 Josh, I'll gladly display my ignorance in exchange for you explaining your statement "with dipoles, a node is an antinode
and visa versa". If you share your knowledge with me (and others), assume I know nothing, which ain't far from the truth! I understand that bass frequencies collect in a room at locations (nodes/modes. Are they one and the same? Also called standing waves, right? More things I don't know!) and frequencies determined by the rooms dimensions. What is an antimode, and why the reversal with dipoles? Thanks---Eric.

 

RE: "extending the lower bass of the panels" ..., posted on March 14, 2017 at 12:43:06
timm
Audiophile

Posts: 780
Location: Ann Arbor Mi
Joined: January 15, 2008
 I can't believe he is having trouble with bass in that room given the hardwood and all of the diffusion.... I can't see his electronics... do you know what they are? Unless he is looking for Wilson Alexandria xlf bass.... Can't get under 50Hz??? That just doesn't sound right.....

 

RE: "extending the lower bass of the panels" ..., posted on March 14, 2017 at 12:32:14
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 So where would he put his T III bass panels? behind him?

 

RE: "extending the lower bass of the panels" ..., posted on March 15, 2017 at 00:28:19
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 The response certainly goes below 50 Hz but he feels there could be more bass. I think he had 20.1 earlier. Power amps are probably LAMM. Not sure how he would use the T-IIIA basses. Will have to visit him soon... Lot of acoustic stuff from Svanå.

Here is a thread from a Swedish forum.
http://www.euphonia-audioforum.se/forums/index.php?/forums/topic/11142-v%C3%A4stkustskt-v%C3%A4lljud-fr%C3%A5n-maggiesar/

 

RE: "extending the lower bass of the panels" ..., posted on March 15, 2017 at 03:48:43
Hasse
Audiophile

Posts: 414
Joined: June 2, 2000
 Most of the bass traps/ diffusion are no longer there. He is using Lamm M2.2 monos.

 

RE: "extending the lower bass of the panels" ..., posted on March 15, 2017 at 08:01:11
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 Hasse,
Have you been there at Claes' place? Yes, his room changed over time.

http://i331.photobucket.com/albums/l454/cmbfoto/_P0F5690.jpg
http://i331.photobucket.com/albums/l454/cmbfoto/_49U3326.jpg

Maybe this is what Claes is refering to? The lack of bass.
http://i331.photobucket.com/albums/l454/cmbfoto/image1.jpg

 

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