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Old 17th February 2012, 03:23 PM   #321
Elias is offline Elias  Finland
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Quote:
Originally Posted by Tubamark View Post
Something I've been trying to work out in my head: If one wants to do a really minimalist full-spectrum SSS - using just 3 speakers and 2 channels of amplification, how do we deal with the bass?
I've got some bass-capable coaxes that I want to try SSS . . .

It seems that the L vs R level and phase shifts would make bass very challenging. 3 drivers won't play together well in a common bass enclosure. Creating a (non-matrixed) Lowpass and successful highpass into a matrix would get pretty complicated due to interaction thru the passive crossover region, etc.

Would everything work just fine if we make M = .33 in the bass range? , L-R bass is rarely very far out of phase on most recordings . . .

Waiting for a 'light bulb' in my head to come on,

-- Mark

I think there is no problem with the bass using the matrix x = 0.5. What problems are you seeing ?

If L and R signals are opposite phase, then due to matrix the center element is mute and side elements are in opposite phase working as a dipole, and in this case there is no pressure change inside the box.

More generally, I think we should look what is the ideal bass reproduction method in the small room acoustic space overall. I have found that dipole bass is very good. Thus I'm using separate dipole bass due to its performance in a small room rather than trying to minimalise the design at this point.

One certainly could design a true single speaker stereo by integrating the bass elements at the base and use a matrix. In this case there is a need for two matrixes (in a two way system). The cross over filter should be installed at the entrance points of the matrix.

I have plans to try the bass matrix as well.


- Elias
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Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
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Old 17th February 2012, 04:10 PM   #322
John L is offline John L  United States
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Originally Posted by Elias View Post
What do you mean by "ideal center of one's position" ?

The location of SSs is not a problem, I have experimented placements in various configurations. It works when placed on the front wall and also 1 m from the front wall. I also succesfully placed it above a TV set.


- Elias
By "ideal center of one's position" I was referring to the need to have the sound balanced to one's ears. And generally that might be a placement which is centered in front of the listener. In most cases this would be near the wall, where the sound would be radiated to the left for the left speaker and to the right for the right speaker. It would radiate outward from the perpendicular walls and add depth, but still a sense of left and right channel.

If the speaker is placed off center, with all things considered, the sound may well be weighed to one side. The speakers could also be brought out into the room, but that would not be practical in most cases.

Also, could you show us a picture of the speaker placed above the TV set? I'd have to see that one. And I am assuming you are not married. Is that correct? Since you state that it was placed 'above' and not 'on top of' the TV, it is either sitting on a shelving unit, platform, or suspended from above? I am having trouble imagining this blending in with the room's other furniture.

My first impression concerning this type of project is that the low frequencies might best be fired downward. Low frequency sound is non-directional, and could be used like a subwoofer, radiating outward in all directions. That would leave the other two channels to be shot out each side of the cabinet. And it could be used to radiate from the side walls, or have a 'diffraction lense' to immediately redirect the sound to the front.

If the bottom is used for low frequencies, the top section would not need to be in larger chambers, so as to bring the frequency response of those upper speakers down lower.

I hope I am making sense here. But that is what immediately came to mind as I envisioned how the cabinet would be made.
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Old 18th February 2012, 12:14 PM   #323
Elias is offline Elias  Finland
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Quote:
Originally Posted by John L View Post
By "ideal center of one's position" I was referring to the need to have the sound balanced to one's ears. And generally that might be a placement which is centered in front of the listener. In most cases this would be near the wall, where the sound would be radiated to the left for the left speaker and to the right for the right speaker. It would radiate outward from the perpendicular walls and add depth, but still a sense of left and right channel.

If the speaker is placed off center, with all things considered, the sound may well be weighed to one side. The speakers could also be brought out into the room, but that would not be practical in most cases.

Also, could you show us a picture of the speaker placed above the TV set? I'd have to see that one. And I am assuming you are not married. Is that correct? Since you state that it was placed 'above' and not 'on top of' the TV, it is either sitting on a shelving unit, platform, or suspended from above? I am having trouble imagining this blending in with the room's other furniture.

My first impression concerning this type of project is that the low frequencies might best be fired downward. Low frequency sound is non-directional, and could be used like a subwoofer, radiating outward in all directions. That would leave the other two channels to be shot out each side of the cabinet. And it could be used to radiate from the side walls, or have a 'diffraction lense' to immediately redirect the sound to the front.

If the bottom is used for low frequencies, the top section would not need to be in larger chambers, so as to bring the frequency response of those upper speakers down lower.

I hope I am making sense here. But that is what immediately came to mind as I envisioned how the cabinet would be made.

Quite a few points you make.

The symmetrical room placement for the SSS and the listener is beneficial but not crusial. For example the lack of sweet spot allows lateral movements in the range of +/- 1 m in my 25 m2 room. Also, if the speaker cannot be placed on the symmetry line of the room, it can be compensated by moving the listening area to the opposite direction.

For the TV set you can see pics by clicking my signature and go to the loudspeakers area, or scroll back this thread for a few pages. Also another Diyaudio member Optic has been using SSS for a TV.

Directional properties at the low freq depends on the speaker. For example dipoles are directional down to DC. SSS is also directional at bass due to the vector steering of the matrix. The directionality depends on the recorded stereo material: If bass is mono in the recording, SSS reproduces it as absolute mono. If bass is coming from one stereo channel, SSS will aim the energy to that side.

For a practical construction integrating SSS bass, of course the bass elements should be placed in a separate enclosure. They should operate with their own matrix. Cross over connects the two matrixes together at the amplifier terminals. One stereo amplifier is enough for a passive implementation of a two way SSS.

- Elias
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Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
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Old 26th February 2012, 11:06 AM   #324
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Not sure if this was posted before but here's another single speaker example: M-S SPEAKER SYSTEM
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Old 27th February 2012, 10:04 PM   #325
Elias is offline Elias  Finland
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Originally Posted by markus76 View Post
Not sure if this was posted before but here's another single speaker example: M-S SPEAKER SYSTEM

Yes it's quite old article already 20+ years. Despite of that I havent's heard or read anyone actually build it, or similar construction.
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Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
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Old 27th February 2012, 11:33 PM   #326
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Originally Posted by Elias View Post
I think there is no problem with the bass using the matrix x = 0.5. What problems are you seeing ?

If L and R signals are opposite phase, then due to matrix the center element is mute and side elements are in opposite phase working as a dipole, and in this case there is no pressure change inside the box.
So far I haven't honestly experienced problems yet, as I'm yet using a subwoofer and my L-C-R speakers are in seperate enclosures. Like you point out, there are no problems 100% dipole (difference) signal. But this is a really rare event in recordings . . . so when using a shared enclosure where the phase and level of each driver is constantly changing - a ported enclosure would probably be out of the question.

Quote:
I have found that dipole bass is very good. Thus I'm using separate dipole bass due to its performance in a small room rather than trying to minimalise the design at this point.
I'm a fan of dipole bass as well, no problem there!

Quote:
I have plans to try the bass matrix as well.
Please do! Many thanks for sharing your ideas and findings.

-- Mark
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Old 28th February 2012, 12:44 AM   #327
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Bass matrix ? I tried it (post 268).
The subject of the test consists of a composite sub : 4 x 15" in an IB, and 2 x 15" by side fitted in H frames. So the results of the test are already conditioned by a difference of efficiency relatively to the frequency as only the central element will produce something in the lowest octaves (it's able to do 20 Hz @ 0 dB).

Any sub is very hard to measure in a confined space. But once the correct repartition optimized, the only residual problem is a lot of combing effect of moderate amplitude while the normal set up shows something smoother.

Listening to it alone, the lateralization is more pronounced. This comes at a price, the lateral H frames are under higher duty. Once listened with the whole system, this improved lateralization weights nothing in front of the clues provided by the mid bass arrays ( Fc 100 Hz), and the only effect of the matrix subs is a reduction of the head room. So, back to the normality and it's ordinary pleasures..
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Old 28th February 2012, 10:44 AM   #328
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I was focused on the bass and forget something more important.
I have extended the matrix wiring to the HF way and it's a very positive improvement. This goes against Gerzon's statements and more modestly against my findings when testing on the mids arrays.

The central speaker is made with two old dynaudio D54 domes in parallel. Like this, they miss the upper octaves, the D54 cuts after 8000, this sounds unbalanced. When joining to them a couple of high passed 1", it gets much better.

Not because supposed improvements of space rendering, but because it simply sounds obviously more natural. I have also seen this phenomenon with the mids, somebody can explain that ?
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Old 28th February 2012, 10:50 AM   #329
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Well, the problem with this kind of experimentation is that you change more than one variable at a time. So in the end you will probably never know what physical change relates to which perceptual change.
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Old 28th February 2012, 11:12 AM   #330
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Good warning markus, but I know the song, I progress step by step and don't post everytime I change something. Same, I keep silence on 99% of the process that results in degradation. I guess everybody is doing the same.
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