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Old 7th July 2013, 09:05 PM   #61
luigi is offline luigi  New Zealand
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Hi Scott

While my L and R subwoofers aren't towers exactly, they do do the business as side walls.

I have employed the Elias pschoacoustic filter of a resistor and cap, and that work pretty well. Have messed with cap values and found one that works, not yet with resistor values.

Like your comments about an upfiring tweeter because the B200s I've found always need a bit of top end reinforcement. Will consider that in time. Just not sure where it would go in the circuit.
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Old 7th July 2013, 09:45 PM   #62
ScottG is offline ScottG  United States
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The center's low-pass filter that Elias has further down on his web page are rather high in freq. and not as "steep" as it might be preferred.

Additionally, the overall intensity from the *sides* is also to high in spl relative to the center. (..the direct sound, NOT the reflected sound - which we want to be higher in level.)

Finally, the intensity gradient isn't "broken" because of the center (..and even if it were, the sides aren't either below about 1.7 kHz for a small fullrange driver). (..refer back to Elias's experiments with a seat cushion in front of the loudspeaker.)


1. you want a "broken" gradient (..that a side-mounted waveguide can provide where the center's output is strongly low-passed),

2. you want to be able to adjust the spl of the side's (above 1.7 kHz) freq. response to get a linear presentation (..or higher spl from those "side-wall" reflections).
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Old 14th July 2013, 11:49 AM   #63
Elias is offline Elias  Finland
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Quote:
Originally Posted by luigi View Post
Theoretically it doesnt really matter whether I terminate the circuit at one negative terminal or both does it?
If the stereo amplifier has common output terminals they should be already internally in galvanic contact.



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Originally Posted by luigi View Post
If Im using Visaton B200 drivers, any idea what kind of overall impedance load that will present to the amplifier? The B200s are nominally a 6ohm load each.
For 6 ohm elements the matrix gives 9 (= 6 + 6/2) ohms impedance for each amplifier. The R-C filter lowers the impedance at high freqs to 6 ohms (in this case).
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Old 14th July 2013, 11:53 AM   #64
Elias is offline Elias  Finland
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Quote:
Originally Posted by breez View Post
While it is usually the case that one speaker terminal is in fact 'common' or 'ground', it doesn't have to be. E.g. internally bridged amps. It means that both terminals are floating and carry a potential with reference to ground. These can not be tied together and the amplifier can go up in smokes if you do. At best you only trigger a protection circuit.

Many of the popular small Class-D/T amps have such configuration.

It would be prudent to add a cautionary note in Elias' page.

Yes the matrix needs a common terminal from the amplifier.

A bridged output amplifier does not yield the intended results, because it does not have the common terminal.

Common means in EE terms having same potential i.e. the voltage between the two common terminals is allways zero.
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Old 14th July 2013, 11:59 AM   #65
Elias is offline Elias  Finland
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Originally Posted by luigi View Post
Ok, so spent a weekend mussing around with this concept. And it works! But with riders, though isn't that always the case?

...

The psychoacoustic circuit is necessary, no doubt.

...

And the sound? If you've longed for a stable soundstage no matter where you are in a room, this is the stereo system for you. For those who mock without trying it, don't. You can move from one end of a sofa to the other and the image is utterly constant.

Glad to hear you got it working well for your purpose

Your comments about the sound I feel are exactly as mine too. No sweet spot, Imaging in the whole room, and the filter is mandatory (though it may depend on the side walls distance and their reflectivity capabilities)


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Even the Significant Other thinks that it is an improvement.
Now that is a heavy argument
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Old 14th July 2013, 12:20 PM   #66
Elias is offline Elias  Finland
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Originally Posted by ScottG View Post
The center's low-pass filter that Elias has further down on his web page are rather high in freq. and not as "steep" as it might be preferred.
I'm sure there is plenty of room for experimentation for the filter values

Basically the required response depends on multiple of things, among others:
- Distance to the side walls
- Reflectivity of the side walls at high freqs
- Directivity pattern of the drivers

Since rooms are different, and because one may use any driver one wishes, there cannot be one universal filter that fits all the situations.



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Additionally, the overall intensity from the *sides* is also to high in spl relative to the center. (..the direct sound, NOT the reflected sound - which we want to be higher in level.)
You may be referring to a 'leakage' of the sound from the side drivers to the listening position.

It is only a potential problem at high freqs where the distance between drivers is getting too long relative to wavelength for proper vector steering to be formed. The solution is easy and can be handled by increasing the directivity of the side drivers.


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Originally Posted by ScottG View Post
Finally, the intensity gradient isn't "broken" because of the center (..and even if it were, the sides aren't either below about 1.7 kHz for a small fullrange driver). (..refer back to Elias's experiments with a seat cushion in front of the loudspeaker.)


1. you want a "broken" gradient (..that a side-mounted waveguide can provide where the center's output is strongly low-passed),

2. you want to be able to adjust the spl of the side's (above 1.7 kHz) freq. response to get a linear presentation (..or higher spl from those "side-wall" reflections).
Do you think anyone understands you "broken gradient" theory ?


If you refer to lobing, yes lobing is intentional and occurs in the whole freq band.

At low freqs the main lobe is steered by the incoming stereo signal and the lobe points to the direction of the highest amplitude panning. This is the whole purpose of the matrix.

At high freqs the lobing occurs due to drivers behaving more individually rather than by vector summing means. Still the matrix gives amplitude separation of 6 dB to the direction of the amplitude panned signal.

That's why this speaker generates stereo images in the room in the first place
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Last edited by Elias; 14th July 2013 at 12:23 PM.
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Old 19th July 2013, 11:43 AM   #67
luigi is offline luigi  New Zealand
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I'm enjoying the sound from the SSS system, still messing with psychoacoustic filter values. They have quite an appreciable effect.
I have always used tweets of some kind with the B200s. I am wondering how to implement auxiliary tweets or even just one in this circuit? If feasible electrically in which direction should this point?
This system is really a bunch of fun. I like that it SO goes against the grain and freaks out people who believe a pair of speakers is an absolute necessity for enjoyable two channel music reproduction. The SSS is way liberating.
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Old 24th July 2013, 08:34 PM   #68
luigi is offline luigi  New Zealand
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So I have been messing around with cap and resistor values for the SSS psychoacoustic filter and last night hit the jackpot at last. The cap/resistor values for the B200s are not so very different from those Elias suggested, though I only saw those after the fact. But last night, for the first time, the image became locked in above the speaker. It is really very much like an image you'd get with two-channel stereo, except that it doesnt matter so much where you're located or whether you head is tilted or which way the wind is blowing. In other words, the image stability is tops, and unchanging.
For those who haven't tried this system, it's definitely worth a shot because it is so easy to build. I had three B200s lying around, and a host of caps and resistors and wire. A basic build took only a couple of hours. Im not saying Im never returning to two speakers, but it will be interesting going back and comparing. Im just not prepared to do that right now.
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Old 24th July 2013, 09:05 PM   #69
ScottG is offline ScottG  United States
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Quote:
Originally Posted by Elias View Post




Do you think anyone understands you "broken gradient" theory ?




Physical Gradient: *direct* sound intensity as it decreases from source/loudspeaker over distance (and to listener).

Put something in the "path" between that source/loudspeaker (relative to freq.), and it becomes "broken".

You know, like a couch pillow in front of the loudspeaker - between the loudspeaker and the listener.


If you put a tweeter/compression driver in a waveguide that's at 90 degrees from the listener (i.e. "side-firing"), then for higher freq.s the gradient is effectively "broken" - it no longer has a direct path to the listener.

Generally, (depending on wavelength), if you can't see the source then the gradient is "broken".
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Last edited by ScottG; 24th July 2013 at 09:10 PM.
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Old 24th July 2013, 09:14 PM   #70
ScottG is offline ScottG  United States
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..A basic build took only a couple of hours..


Have you tried moving those subs further away from the center speaker/"array"?
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