It's a common sense (or myth) that LF portion in most stereo recordings is nearly mono.
However, in my experience, I had once encountered an extraordinary effect from bass matrix. So I suspect the statement of "LF in stereo is nearly mono" is solid enough.
That's in the early stage when I built and tuned my 3 dipole subs. It's an active system, I made the matrix in line level. A stereo amp drives L & R, and another plate amp drives the C.
Once the level settings of the sides and center were way off. Too little in center and too much on both sides. At that moment, I clearly sensed a very odd and very low frequency sound comming from the right side of the listening position -- that's the direction of 3 o'clock ! It's completely nuts because the speaker was not there and way off, but I did feel the sound was coming from that direction. (why 'sensed' instead of 'heard' ? it's because it's more of a sense of air flow or vibration than sound at that moment)
It's a wrong setup, but also revealing there're indeed chances to have quite a lot difference between stereo 2-ch. So I got strong enough differential signals.
After the levels among 3-ch are properly set, the odd effect is gone, with an significantly improved sense of space than ordinary 2-ch stereo bass with 3-ch matrix in mid-high sections.
That's on 3 separate subs. I don't know how it'd perform in a single box. Just guessing the symmetry and refections of side walls must be important.
However, in my experience, I had once encountered an extraordinary effect from bass matrix. So I suspect the statement of "LF in stereo is nearly mono" is solid enough.
That's in the early stage when I built and tuned my 3 dipole subs. It's an active system, I made the matrix in line level. A stereo amp drives L & R, and another plate amp drives the C.
Once the level settings of the sides and center were way off. Too little in center and too much on both sides. At that moment, I clearly sensed a very odd and very low frequency sound comming from the right side of the listening position -- that's the direction of 3 o'clock ! It's completely nuts because the speaker was not there and way off, but I did feel the sound was coming from that direction. (why 'sensed' instead of 'heard' ? it's because it's more of a sense of air flow or vibration than sound at that moment)
It's a wrong setup, but also revealing there're indeed chances to have quite a lot difference between stereo 2-ch. So I got strong enough differential signals.
After the levels among 3-ch are properly set, the odd effect is gone, with an significantly improved sense of space than ordinary 2-ch stereo bass with 3-ch matrix in mid-high sections.
That's on 3 separate subs. I don't know how it'd perform in a single box. Just guessing the symmetry and refections of side walls must be important.
Any suggestions for amps (preferably chip or class D) that can take the punishment, for I guess amounts to bridging, in this kind of matrix setup?
Alternatively how would one go about doing it at the line level?
Does it require a complex decoder like the Ambio or can it be done simply?
Alternatively how would one go about doing it at the line level?
Does it require a complex decoder like the Ambio or can it be done simply?
Last edited:
If you accept OP amps, it should be doable in simple differential/summing analog circuits:
L' = L- xR
C = (1-x) (L+R)
R' = R- xL
x can be 0.5 to 0.8
I asked mini dsp about this, they replied that such program was not readily available and there're not enough inquiries to support a proper business. That's maybe 2 years ago, don't know how it's going at this moment.
I myself use output transformers in pre amp with multiple secondary windings. And cross-connecting part of the windings to form the subtraction between 2 channels. So the outputs are R-0.5L / L-0.5R. And then the center is derived from summing them by a simple Y connecting resistor and a pot to ground. (It might be better if I use a bufferred mixer in the center channel.)
L' = L- xR
C = (1-x) (L+R)
R' = R- xL
x can be 0.5 to 0.8
I asked mini dsp about this, they replied that such program was not readily available and there're not enough inquiries to support a proper business. That's maybe 2 years ago, don't know how it's going at this moment.
I myself use output transformers in pre amp with multiple secondary windings. And cross-connecting part of the windings to form the subtraction between 2 channels. So the outputs are R-0.5L / L-0.5R. And then the center is derived from summing them by a simple Y connecting resistor and a pot to ground. (It might be better if I use a bufferred mixer in the center channel.)
long time since this topic was posted to, but fwiw, a good candidate for a stereo speaker box is the Metronome.
the woofer could be placed front. the sides at the right and left sides toward the top along with the center at about the same level, along with the tweeter. the last 4 could even be placed in a OB frame at the top of the Metronome cabinet.
the woofer could be placed front. the sides at the right and left sides toward the top along with the center at about the same level, along with the tweeter. the last 4 could even be placed in a OB frame at the top of the Metronome cabinet.
Small, it can fit in a shoe box
4 drivers 3 in.(4ohm 5 W) in a pannel,
My idea is to create a portable bluetooth speaker for near listening of movies, play games or music videos on a cellphone mounted on top, 1 to 2 feet away from you.
Or
Mount this speaker on the top of your computer screen
If you close your eyes, you can spot 6 different areas of this new spatial aura.
- central surround 1
- stereo at both sides almost at 1 meter away +2
- 1 Mono far away at your sides +2
- Mono behind your head +1
Little coloration and surprisingly good low frequencies; bass, explotions and drums are fantastic, in a different way not boomy but no more "one tone bass".
I think it can not be mesured because it is a feeling instead of phisical fact.
I can add a planar bass radiator so I can reach 25 Hz (12x4 in)
3 years experimentation, +40 prototypes I have to destroy to make the next one...
4 drivers 3 in.(4ohm 5 W) in a pannel,
My idea is to create a portable bluetooth speaker for near listening of movies, play games or music videos on a cellphone mounted on top, 1 to 2 feet away from you.
Or
Mount this speaker on the top of your computer screen
If you close your eyes, you can spot 6 different areas of this new spatial aura.
- central surround 1
- stereo at both sides almost at 1 meter away +2
- 1 Mono far away at your sides +2
- Mono behind your head +1
Little coloration and surprisingly good low frequencies; bass, explotions and drums are fantastic, in a different way not boomy but no more "one tone bass".
I think it can not be mesured because it is a feeling instead of phisical fact.
I can add a planar bass radiator so I can reach 25 Hz (12x4 in)
3 years experimentation, +40 prototypes I have to destroy to make the next one...
where do you live? there is no way to explain or understad until you listen the arrangement is the size of a shoe box, open baffle almost free air. I think it can be patented, I am looking for someone to share this adventure.
I think it does not interact with wals...
just special angles, there is no matrix
I think it does not interact with wals...
just special angles, there is no matrix
Last edited:
It all depends on how the speakers are driven.
If the three speakers are driven "mid-side" then perhaps yes, you may get something similar to Elias's designs (which basically are nothing else than the M/S microphone technique "reversed").
OTOH, if the two "back" speakers are simply driven by L and R signals, then it's something completely different. First of all, in such a case the front speaker is probably inessential (it's likely just a mono "sub" and/or it's used like an added center channel to avoid a possible "hole in the middle").
In any case, the reflections on the back wall will create two virtual speakers behind the wall (where the first reflection take place, thus way much more spaced apart than the real speakers are, depending on angle and distance from the back wall).
Such a setup may work well as far as the back wall will reflect sound without adding significant "coloration" to it. That is if it's equally well reflective at all frequencies within the audio range. Solid, stiff walls with even, flat surface (such as plastered bricks and/or concrete walls) should work well. OTOH, "light" walls made out of wood, drywall, etc., or walls made out of (or covered with) acoustically absorbent materials (and/or patterns) will likely not.
BTW: another way to look at such an arrangement (considering only the two angled speakers on the back, if they are driven by L and R signals, without stereo matrix processing) is to consider that it looks like an XY stereo mic setup... "reversed" (and pointed backwards).
If the speakers have the appropriate polar pattern, in principle it could work even "the other way 'round" (that is, front facing) ...
problem is, I guess that most real-world speakers are not directional enough to make it work that way.P.S.: also the traditional two-speaker stereo triangle can be seen as one of the common stereo mic. setup reversed... in fact, it's just like the spaced pair (a variation of the A-B technique, with much larger distance between the two mics). Given that it requires omni-directional mics, no surprise that IMO/IME the "traditional" speaker setup works best with omni speakers...
Have you addressed the derivation of height cues? Have you tried higher order ambisonics?
Do you believe the playback of binaural stereo recordings with head tracking and personalized dynamic convolution without the addition of crosstalk has the same performance than playback of 16 channel ambisonics output with the same head tracking and personalized dynamic convolution playback?
Please see the question and discussion at the following head-fi thread: head-if.org - Smyth Research Realiser A16 - post #596
This guy is doing something similar Home - Aspen Pittman Designs
https://www.thomann.de/ro/aspen_pittman_designs_monitoare-pa_active.html
https://www.thomann.de/ro/aspen_pittman_designs_monitoare-pa_active.html
Actually, this is exactly what Elias have been doing since several years!
See here: SingleSpeakerStereo
Last edited:
Actually, this is exactly what Elias have been doing since several years!
See here: SingleSpeakerStereo
Almost, but the Aspen Pittman Designs use one driver in OB configuration for the side info. So not exactly the same and the side effects will (probably) effect the room in a different way and therefor should (probably) display a different sound field compared to Elias speaker.
Last edited:
Very cool system Elias! I have to try this out!
Is there really need for active combining in line level? can' one just do the matrix between preamp and three power amps as illustrated with the speaker connection matrix? Given that the poweramps have equal input impedance.
Its very simple to use stereo amp and connect the speakers like the matrix, but this messes up speaker response if the speakers are multiway with passive crossovers?