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Bass panels one after the other?

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Posted on June 15, 2014 at 09:35:49
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 I just started thinking (for my DIY project) that would it make any sense to stack a few Maggie bass panels one after the other? I mean; instead of having a huge setup with 2 bass panels side by side, what would happen if second (and maybe third?) bass panel would be placed just behind the first one, with maybe something like 5 - 20cm gap? Would it actually be just the same than with one panel, or what..?

 

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RE: Bass panels one after the other?, posted on June 15, 2014 at 10:27:44
j beede
Audiophile

Posts: 239
Location: NorCal
Joined: March 28, 2011
 Have you already done a search for "isobaric woofers"?

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 10:59:55
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 No I did not, thanks for the hint!

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 11:04:05
Davey
 That's not really an Isobaric configuration since the cavity between is not sealed. This is more of a "compound" dipole configuration ala the Legacy Whisper system.
Unless one of the panels is reversed to create even-order distortion cancellation there isn't much point to it. There is no inherent sensitivity gain/loss nor any frequency extension.

Cheers,

Dave.

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 11:21:36
Roger Gustavsson
Audiophile

Posts: 2055
Location: Huskvarna
Joined: February 12, 2010
 If the bass drivers come from a Tympani, they will not be identical.

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 11:22:33
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 Ok, thanks Davey!

But it did not quite understand that "Unless one of the panels is reversed..." part, could you explain a bit more? Did you mean putting two bass panels together, both magnets facing outwards, and changing the phase from other panel? Would this be a bit like one push-pull driver..?

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 11:51:07
Roger Gustavsson
Audiophile

Posts: 2055
Location: Huskvarna
Joined: February 12, 2010
 If there is a distance between the two, let us say a few cm or inches, it will be far from a push-pull driver. A push-pull driver need to have everything carefully aligned and the tension of the diaphragm probably need to be different too. If you put the drivers behind each other, they need to move in the same direction.

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 12:26:45
Davey
 Other than the 20.X series, the Maggie panels are asymmetric. So, if you reverse one (transducer or magnet sides facing each other) then you'd have one diaphragm moving toward the magnets while the other one was moving away. You've created a symmetric configuration where (net) even-order distortion has been reduced, relative to a single panel.

Cheers,

Dave.

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 12:32:05
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 Ok, thanks Davey!

But it did not quite understand that "Unless one of the panels is reversed..." part, could you explain a bit more? Did you mean putting two bass panels together, both magnets facing outwards, and changing the phase from other panel? Would this be a bit like one push-pull driver..?

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 12:41:21
Roger Gustavsson
Audiophile

Posts: 2055
Location: Huskvarna
Joined: February 12, 2010
 You cannot make them push-pull that way. The idea of push-pull is that it is all symmetric.

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 19:18:28
hahax@verizon.net
Audiophile

Posts: 4306
Location: New Jersey
Joined: March 22, 2006
 How about 2 bass panels but with the mid/tweeter between them like the Quad 57?

 

RE: Bass panels one after the other?, posted on June 15, 2014 at 21:56:21
Roger Gustavsson
Audiophile

Posts: 2055
Location: Huskvarna
Joined: February 12, 2010
 If the bass panels are crossed over at a low frequency (below 500 Hz or so)it works fine.

 

RE: Bass panels one after the other?, posted on June 16, 2014 at 04:45:53
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 That's also on interesting option, hahax!

How much benefit would two bass panels per side actually give, against one? If stock 2.6R's go down to 37hz, what would be the lower limit with two panels per side? Would it be Tympani IV- like solution..?

And; how would the bass panels on both sides of the mids & high effect their representation?

 

RE: Bass panels one after the other?, posted on June 16, 2014 at 06:52:32
Roger Gustavsson
Audiophile

Posts: 2055
Location: Huskvarna
Joined: February 12, 2010
 The bass driver of the 2.6 has different tuning than the Tympani basses. The mass of the wire is also different, double for the 2.6. One or two identical bass drivers will not change the low frequency roll-off.

There is something strange with the technical data on the 3-series, the cut-off frequency is not as low as indicated. My 3.6 roll-off below 42-44 Hz, 18 dB/octave as any open panel. My Tympani IIIA roll-off below 31-33 Hz. I have not checked my Tympani IVa but expect them to be similar to the IIIA.

 

RE: Bass panels one after the other?, posted on June 16, 2014 at 09:01:38
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 "One or two identical bass drivers will not change the low frequency roll-off". But Roger, if I use active setup with digital equalizer such as DEQX, shouldn't it be possible to get a bit more lower freqency? I mean; two identical drivers will give 10db more on a whole frequency range (or was it so...?). So, I need to drop 10db from the basses to match mid's level again. But if I would not cut anything from the lowest frequencies, only above roll-off point, wouldn't it give a bit more basses on the lowest section?? I don't know how much, anyway...

On the other hand; two bass drivers per side could give a bit more sound pressure and/or less distortion on higher basses, but I don't know if it actually makes any difference in real life?

 

RE: Bass panels one after the other?, posted on June 16, 2014 at 09:05:05
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 "There is something strange with the technical data on the 3-series, the cut-off frequency is not as low as indicated. My 3.6 roll-off below 42-44 Hz, 18 dB/octave as any open panel. My Tympani IIIA roll-off below 31-33 Hz. I have not checked my Tympani IVa but expect them to be similar to the IIIA".

I don't know if these numbers are accurate: http://www.integracoustics.com/MUG/MUG/articles/speakers.html

But it says that;
- Tympani III-A: 42hz
- Tympani IV: 43hz
- Tympani IV-A: 30hz
- MG-20- series: 25hz

It's quite surprising to see that MG-20's would really go lower than IVīs??

 

RE: Bass panels one after the other?, posted on June 16, 2014 at 09:56:47
Roger Gustavsson
Audiophile

Posts: 2055
Location: Huskvarna
Joined: February 12, 2010
 Well, the 3.6 has a "hump" at 50 Hz. The "hump" for the T-IIIA and the MG-20.1 is at 35 Hz. Two drivers lowers the distorsion for the same soundpressure. Magnepan states 34 Hz for many 3-series, not really true...

 

RE: Bass panels one after the other?, posted on June 17, 2014 at 08:03:10
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 Roger; did you have any comment on my post posted on June 16, 2014 at 09:01:38..?

 

RE: Bass panels one after the other?, posted on June 17, 2014 at 08:15:28
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 When you switch around the T IV panels and wall load the deep bass panel and place the upper bass in the middle, you get a rolloff at about 25 hz. Together with the tangent or oblique room mode when the speakers are placed midway into the room near the sidewalls, you get an elevation of the 30-40 hz band - I set it up to have the deep bass 3-6db above the midrange 30 to 50 hz.

 

RE: Bass panels one after the other?, posted on June 19, 2014 at 11:07:41
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 I can answer You Aku.

You will get somewhat louder sound and lesser distortion.
But the loudness depends on if You connect them in series or paralleled.
But the distortion is only lesser if the drivers are very close together.

But You have to get that You will NOT be able to play any louder at all!
This because the chain is not stronger then the weakest link and the membrane that would before the build hit the magnets will do it again at the same db and at that hz that the tuned part will resonate.

No gain apart from lowered distortion!!!!!!!!!


The one who succeeded was the one who didn't know it was impossible.

 

RE: Bass panels one after the other?, posted on June 21, 2014 at 04:16:48
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 Ok, thanks JLindborg! I don't care about playing any louder, I'm just thinking is there any way to get more lower bass from Maggie bass panels, somewhere near 30hz or even a bit lower. Of course buying 20.x should do it, but it's just out of my budget.


BTW; what actually is purpose of those tuning buttons? What would happen if they are removed...?

 

RE: Bass panels one after the other?, posted on June 21, 2014 at 04:46:47
Roger Gustavsson
Audiophile

Posts: 2055
Location: Huskvarna
Joined: February 12, 2010
 The tuning buttons are to the distribute the resonance behaviour over a larger frequency range. If you remove them it will change the low frequency behaviour. Not sure if you can use a 2.6 without the buttons. Maybe the diaphragm will hit the magnets early? A low resonant frequency will result in a large peak that takes a lot of excursion, lowers the maximum soundpressure. One of the buttons came loose om my 3.6, made an awful resonance around 90-100 Hz.

 

RE: Bass panels one after the other?, posted on June 21, 2014 at 04:51:32
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 You can use EQ to boost.
But be aware of the fact that particularly the bass frequencies are directly related to move a LOT of air.
With a fixed area of membrane, the only left thing is larger excursion. And with as little excursion ability that a Magnepan speaker has, You are not going to be able to play any "loud".

Removing the tuning buttons will only be possible by removing the whole membrane.

Cheers!
The one who succeeded was the one who didn't know it was impossible.

 

RE: Bass panels one after the other?, posted on June 21, 2014 at 10:36:50
Roger Gustavsson
Audiophile

Posts: 2055
Location: Huskvarna
Joined: February 12, 2010
 True, you cannot remove the buttons without destroying the diaphragm, the buttons are glued to a piece of foam tape sitting between the Mylar and the magnets.

 

RE: Bass panels one after the other?, posted on June 21, 2014 at 11:45:38
audiozorro
Audiophile

Posts: 628
Location: VA-MD-DC
Joined: January 9, 2007
 "How much benefit would two bass panels per side actually give, against one?"

A lot or a little depending on how you have them set up. The bass panels get a boost when they are positioned perpendicular to the side walls. The bass panels also get a boost when they are powered with a separate amp.

Would you have the outer L/R bass panels powered separately, the inner L/R bass powered separately, or all bass panels powered by an amp separate from the amp driving your main panels? The right answer is achieved by trial and error and depends on your room, audio equipment, levels of distortion, desire for smooth bass and tonal balance.

How many bass panels are too many? I don't know but adding bass panels and separate amps can get costly, approximately $3K for a pair of DWMs and a suitable amp.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 00:52:22
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 Audiozorro, does it really matter if both bass drivers use the same amp or different amps? I mean, wouldn't is be just the same to have one 600W amp or two 300W amps? Anyway, I'm going to use Hypex UCD's for basses (that is 400W, 700W, or 2kW, don't know yet which ones) and fully active setup with digital XO's.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 01:00:12
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 JLindborg; "But be aware of the fact that particularly the bass frequencies are directly related to move a LOT of air. With a fixed area of membrane, the only left thing is larger excursion. And with as little excursion ability that a Magnepan speaker has, You are not going to be able to play any "loud".

But wouldn't it be so that using twice the driver area, those drivers need to move only half of that with one driver, on a same volume level? So basically I could add a bit more level on the lowest frequencies (25-40hz etc.) with EQ, without having to be afraid that driver hits the magnets?

I don't know if my thinking is totally wrong with this...?

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 01:31:21
Roger Gustavsson
Audiophile

Posts: 2055
Location: Huskvarna
Joined: February 12, 2010
 If you are going to use identical bass panels and want to the same crossover frequency, you can use one channel of amplification. Is it still two 2.6 bass panels each side? If yes, remember the amplifier will se 2 ohm. I think more than 200 W per panel is of little use as they will compress above 150 W and the diaphragm will hit the magnets if going for even more power, especially if you hit the fundamental resonance of the panel.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 01:34:50
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 That is only true if You actually ADD bass area.
Joining 2 panels as You described with the magnets opposing each other will not ADD any surface at all!!!
It will still be the same amount of square meters/feet.
Joining them side by side will add to surface area and will double the space they take up in the room.
That is why they built the Tympani models! To make up for the limited excursion ability of the Magneplanar design.

Cheers!



The one who succeeded was the one who didn't know it was impossible.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 02:04:26
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 No no no, that idea of joining two panels was already rejected. So now I'm thinking if two 2.x (or such) panels would give any benefit when positioned side by side, maybe on a one stiff wooden panel? It might not be IVA- like, but could it be even close?

BTW; why couldn't two unequal drivers connected parallel be driven with one amplifier? I think that even IVA- drivers are not quite similar, and for what I have understood, they are often driven with one amp..?

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 02:26:21
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 Sure You can drive 2 panels with 1 amp! No problem at all!!!

If You are serious with low frequency reproduction with a Magnepan dipole, You have to use panels without tuning buttons.
If You have tuning buttons You will restrict movement at each place a button is placed and thus the whole membrane will NOT move as 1.

1 tuning button will render about 2/3 of usable membrane the rest is downforced by its own mounting at the surround AND the button creating a curved movement. So in practice, to say that the whole of the membrane is usable as bass reproduction is EXTREMELY faulty reasoning as it does NOT move like a piston at all!!!
Only the center of the membrane is close to a piston movement and the rest is a declining function of a curve.

Cheers!

The one who succeeded was the one who didn't know it was impossible.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 05:03:02
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 Well, you can't take out the buttons without making holes in the Mylar, but you can fix the holes with packaging tape. For the bass freq you want to cover with it that should not be a problem. The downside is that the speaker will never sound like the 2.x it once used to be and will have really low resale value.

Wiring it up you would want to have the second bass driver kicking in at a lower freq so as to avoid smearing so you would hook it up in parallel with its own new inductor calculated to kick in at the 100-200 hz range.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 05:03:06
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 "If You are serious with low frequency reproduction with a Magnepan dipole, You have to use panels without tuning buttons."

Do you JLindborg (or anyone else here) have any experience on removing those buttons? Would not want to be first one to try, just to see that it destroys the whole driver and it can't be fixed back...

On the other hand; why would Magnepan use those buttons, if removing them would be better? Or does it have something to do with upper frequencies?

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 05:32:31
Davey
 Unfortunately, he doesn't understand the trade-off the buttons provide and the result if they were removed.

If the folks at Magnepan were to construct a bass transducer (for one of the buttoned systems) with their normal procedure with the exception of not gluing in the tuning buttons it would yield a drum skin with a large resonant mode at a single frequency. This resonant frequency would be much lower than the existing one(s) and then front/back dipole cancellation effect/distance created by the baffle width would no longer line up to EQ it.

It's simplistic to think you could achieve a superior result just by removing the tuning buttons and leaving all the other design aspects the same. I'm not sure that's what he's advocating, but if it is, it won't work. :)

Hope that makes sense.

Cheers,

Dave.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 05:56:10
JLindborg
Audiophile

Posts: 1037
Location: Uppsala
Joined: April 26, 2010
 Magnepan uses tuning buttons for the very reason they are called just that.
To remove them You will have to ruin the membrane and replace it with a new with specified tension to get the resonance frequency You need.

Cheers!
The one who succeeded was the one who didn't know it was impossible.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 06:31:04
audiozorro
Audiophile

Posts: 628
Location: VA-MD-DC
Joined: January 9, 2007
 "Does it really matter if both bass drivers use the same amp or different amps?"

I have found that it really matters but that may depend on your setup. For me it is very important to control the volume on the bass panel, which I accomplish by using a separate passive preamp or volume control. I would want to increase the bass levels of the second pair of DWMs to be just below any audible hints of distortion.

The first pair of DWMs are connected to the main speakers and both are controlled by the primary preamp. The volume of the second pair of DWMs is controlled by the passive preamp, which allows me to tailor the bass to the room and my taste. The placement of the DWMs is used to achieve smoother, and if necessary lower, bass response.

This would not be easy to achieve with one amp, which is one of the reasons that many audiophiles prefer the older Maggies that can be biamped. For me it's all about tailoring the panels to your room and tastes.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 07:32:21
AkuAnkka
Audiophile

Posts: 167
Joined: February 3, 2013
 But for what I have understood, DWM's go only down to 40hz? If 2.5R's are already able to go down to 37hz, how could DWM's help them to go lower?

Or on the other hand; if DWM's really could help, wouldn't it still be better to add another 2.x bass panel instead of the DWM's? Larger driver, lower frequency range, and maybe also cheaper as second hand.

 

RE: Bass panels one after the other?, posted on June 22, 2014 at 08:00:47
Swamis Cat
Audiophile

Posts: 272
Location: Illinois
Joined: September 7, 2013
 Zorro and Aku,

I have no thoughts on using a separate full speaker as a bass panel. I do have experience with DWMs though.

I have a single pair driven by my main amp as suggested by Magnepan. In my room with my main speakers well out in the room eight to ten feet, the DWM's (set up about a foot closer to listening position) go down to 80hz max. They cover 80 to about 250. Based upon exact placement relative to side walls and relative to the mains and with the use of resistors to attenuate output, I can tune the bass to be perfectly flat (or as desired.)

The aha! Moment for me with DWMs was when I realized I could use the tuning freedom to optimize the placement of mains for low bass and imaging. So the answer to the question of how can DWMs help us to lower the bass on main speakers is that it gives us the freedom to position the main speaker in the place which optimizes low bass. In my case, the place with the best bass for 30 hz had a major suckout in the crucial mid and upper bass. I optimized the mains for bass in the upper twenties and low thirties and optimized the DWMs to fill in the holes.

This is one guys experience (in two rooms), so take it for what it is worth.

Zorro, am I reading you right that you have four DWMs? Way cool. I do not have an extra amp or preamp, but if I did it would be interesting to further dial them in. Do you get bass to 40 or 50 out of yours? How close to the FW are they?

 

RE: Bass panels one after the other?, posted on June 23, 2014 at 12:46:14
audiozorro
Audiophile

Posts: 628
Location: VA-MD-DC
Joined: January 9, 2007
 "If DWM's really could help, wouldn't it still be better to add another 2.x bass panel instead of the DWM's? Larger driver, lower frequency range, and maybe also cheaper as second hand."

If you can get the Tympani bass panels that would be better. I was more comfortable with new speakers that would be under warranty and in my choice of colors. The only other benefit for the DWMs over the Tympani bass panels might be they may be less obtrusive and multiple DWMs might allow for greater flexibility in placement. But you have to add a lot of DWMs to provide the same surface area of the Tympani bass panels. If Magnepan would offer a modern version of the Tympani IVa I would buy them in a heartbeat.

 

RE: Bass panels one after the other?, posted on June 23, 2014 at 13:14:56
audiozorro
Audiophile

Posts: 628
Location: VA-MD-DC
Joined: January 9, 2007
 No I don't have four DWMs. My experience to date was to experiment with the Mini Maggie system with two DWMs.

When I had the Mini Maggies in the basement, I had one DWM on a speaker stand and centered between the midrange/tweeter satellites. The 2nd DWM was located on the floor below the other DWM and powered by a separate amp.

When I moved the Mini Maggies upstairs to the living room I had the typical L/R stereo pairing of the DWM and midrange/tweeter panels. The Maggies are all on stands and I have subs on the floor.

My goal was to someday either have a multi-channel system using two Mini Maggie systems for the front and rear speakers in the living room upstairs or a multi-channel system using the Mini Maggie system with 2 DWMs as the rear speakers to my full range electrostatic speakers in the basement.

 

RE: Bass panels one after the other?, posted on June 29, 2014 at 02:31:52
triamp
Audiophile

Posts: 780
Location: USA
Joined: August 6, 2008
 The Martin Logan CLX full range electrostatic uses three stators / two diaphragms like this- they call it "dual force transducer" see the link

I assume they drive the diaphragms 180 degrees apart. I assume but I'm not CERTAIN, though, that they do....
Science doesn't care what you believe.

 

RE: Bass panels one after the other?, posted on July 15, 2014 at 18:34:03
jdcarlson
Audiophile

Posts: 1
Joined: July 15, 2014
 Isn't this what Legacy does with their top of the line "Whisper" series?
It seems like they put two woofers, one behind the other, with not baffle to keep the front wave from the back wave?????

 

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