The matrix circuit that I used, based on the design on Elias' website - the drivers are all in phase. Treat as if the drivers are parallel connected for left and right and then in series for the center channel. If you are running two drivers in center channel those are together in parallel but series with left and right. In any event it is same as 4 drivers wired in series-pararallel. Still in phase so calculate as if a box with 4 drivers. Same as 4x volume of single driver box and 4 vents at same length or equivalent single vent.
Most bass reflex calculators let you choose number of drivers.
Any reason this Jensen schematic couldn't be used in reverse to generate sum and difference channels at line level from a stereo source?
http://www.jensentransformers.com/as/as065.pdf
That would allow a two channel amp to drive the centre(s) and sides loudspeakers independently, and filters/gain could be added at line level before amplification.
Also, nice little class-D amps like the TPA3110 could be used (no need for an amp with common ground reference for both channels).
http://www.jensentransformers.com/as/as065.pdf
That would allow a two channel amp to drive the centre(s) and sides loudspeakers independently, and filters/gain could be added at line level before amplification.
Also, nice little class-D amps like the TPA3110 could be used (no need for an amp with common ground reference for both channels).
Pretty cool - passive summing junction via signal transformers! You are the transformer input wiz. This should work but you mean to use two of these and then use two class D amps to drive 4-drivers? L-R, L+R=C1, R-L, L+R=C2?
No need for two stereo amps 
The centre speaker would get one amp channel (with two drivers in series or parallel if required) and the two side speakers would be driven by the other channel (one speaker out of phase with the other).
Of course you could drive each speaker with a separate amp channel if you prefer.
My plan is to add one of these boards to the system:
DIY Kit--LM1036N Fever Volume control board Kit for DIY (12V DC/AC power supply) | eBay
The source would feed the transformer matrix, which would feed the LM1036 board before a TPA3110/3116 amp board. All active electronics running from one 12VDC supply.
The LM1036 would allow for equal loudness volume control, bass+treble control! overall volume and (drum roll!) the balance control would alter the level of centre audio relative to side.
I'm going to stuff all of this in one box with 4x Hiwave BMR drivers (2 at the front, one either side) and make a nice mount for my iPad on top.
The centre speaker would get one amp channel (with two drivers in series or parallel if required) and the two side speakers would be driven by the other channel (one speaker out of phase with the other).
Of course you could drive each speaker with a separate amp channel if you prefer.
My plan is to add one of these boards to the system:
DIY Kit--LM1036N Fever Volume control board Kit for DIY (12V DC/AC power supply) | eBay
The source would feed the transformer matrix, which would feed the LM1036 board before a TPA3110/3116 amp board. All active electronics running from one 12VDC supply.
The LM1036 would allow for equal loudness volume control, bass+treble control! overall volume and (drum roll!) the balance control would alter the level of centre audio relative to side.
I'm going to stuff all of this in one box with 4x Hiwave BMR drivers (2 at the front, one either side) and make a nice mount for my iPad on top.
I don't think you can just use one amp and swap phase of L & R speakers. The sum of L+R which you plan to use for the center and the difference R-L and L-R are inherently orthogonal "eigenvectors" and you cannot get one from the other. Maybe I am missing something but you need 3 channels of amplification minimum if you want to do the matrix upstream of the amps.
I could easily be oversimplifying things, so happy to review my thought process.
The original four driver schematic shown by Elias in post 1 shows the the two side speakers being connected to the same poles, with the two in opposite phase. This would make them equal but opposite, so this could be achieved with one amp channel driving both. In my solution the two front speakers would both produce the sum of R+L, rather than one R and one L.
The original four driver schematic shown by Elias in post 1 shows the the two side speakers being connected to the same poles, with the two in opposite phase. This would make them equal but opposite, so this could be achieved with one amp channel driving both. In my solution the two front speakers would both produce the sum of R+L, rather than one R and one L.
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I don't know - I will defer to the expert, Elias to answer this one.
If what you say is true we can also do this easily with two op amps in front of the amplifier as a summing junction and a difference junction. It also means that the drivers for L and R will be in series so need 4 ohm drivers.
If what you say is true we can also do this easily with two op amps in front of the amplifier as a summing junction and a difference junction. It also means that the drivers for L and R will be in series so need 4 ohm drivers.
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The drawing on the right in post #127 is so called linear matrix with x=0.5.
L'= L- xR
C= (1-x) (L+R)
R'= R- xL
It's said to have good results when x = 0.5 to 0.8.
Read this: AES Preprint: "An Optimum Linear-Matrix Stereo Imaging System"
L'= L- xR
C= (1-x) (L+R)
R'= R- xL
It's said to have good results when x = 0.5 to 0.8.
Read this: AES Preprint: "An Optimum Linear-Matrix Stereo Imaging System"
Oh, transformer was brought up. I missed that.
Guess what, I've done that with OPT in my tube preamp.
By configuring the secondary windings to 'subtract' part of the signal level of the other channel, I (sort of) got 2 channels of partially differential. See attachement.
These 2 outputs feed the L' & R'. And I simply sum them to get a C into another amp/speaker.
One thing I'm not 100% sure is about their impedance matching etc. Well, I haven't detected obvious ill effect nevertheless.
Guess what, I've done that with OPT in my tube preamp.
By configuring the secondary windings to 'subtract' part of the signal level of the other channel, I (sort of) got 2 channels of partially differential. See attachement.
These 2 outputs feed the L' & R'. And I simply sum them to get a C into another amp/speaker.
One thing I'm not 100% sure is about their impedance matching etc. Well, I haven't detected obvious ill effect nevertheless.
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Just two resistors and a volume pot in line level to feed the amp of center channel. I've been thinking to add a buffer stage, but lazy.
In the bass section, it's done in the plate amp, also in line level. There's a built-in mixer to sum both channel into mono.
Oh, my preamp is 4-channel, with built-in crossover
In the bass section, it's done in the plate amp, also in line level. There's a built-in mixer to sum both channel into mono.
Oh, my preamp is 4-channel, with built-in crossover
I have been following the original Stereo Sound from a Single Loudspeaker thread and would love to build one.
How would these designs work 3 foot out from a corner? I am thinking of building something to go under a flat panel TV which is on a low cabinet arranged diagonally in a corner.
Would the four speaker design benefit from one of the center speakers firing upwards, or backwards toward the corner?
How would these designs work 3 foot out from a corner? I am thinking of building something to go under a flat panel TV which is on a low cabinet arranged diagonally in a corner.
Would the four speaker design benefit from one of the center speakers firing upwards, or backwards toward the corner?
I tried it in a corner in a small room and it works still in that you get stereo separation as it bounces off the two walls of the corner. You need to be back a distance though (8 to 12 ft) to enjoy the best stereo image so no the best for small room. I would say that you should build a cheap and quick box out of foam core or cardboard to test out and make it in wood if you like it. This is one of those speakers that is very placement dependent and you won't know or be able to tell if you like it until you test it. Get qnty 3 Vifa TC9FD's (or other high Qts full range driver) and some foam core from the dollar store and in 2 hours you will know.
Matrix = 0.5 TV Speaker
Critique my design for a TV speaker to sit on a credenza in a corner underneath a 42" flat panel.
Design goal is good sound for televised concerts, with clarity of dialog and high WAF as the secondary goals. This is not "Home Theater"! Explosions and bullets flying behind me are not my thing; no "Transformers 3D" for me!
Note: The Dayton plate amp rolls off the front speakers at 12db an octave below 150hz. Woofer level, crossover point, and phase will be set by ear.
Critique my design for a TV speaker to sit on a credenza in a corner underneath a 42" flat panel.
Design goal is good sound for televised concerts, with clarity of dialog and high WAF as the secondary goals. This is not "Home Theater"! Explosions and bullets flying behind me are not my thing; no "Transformers 3D" for me!
Note: The Dayton plate amp rolls off the front speakers at 12db an octave below 150hz. Woofer level, crossover point, and phase will be set by ear.
Attachments
Neat design - I think it looks good and should sound good. You may not be able to use this plate amp though as it is class D. You cannot tie outputs of typical class D amps together in matrix without shorting it out if they are in what is known as "bridge tied load" (BTL). Alternatively, get a separate sub plate amp that is sub only with a high pass XO. Get a dedicated class AB chip amp to drive the matrix. Something like a standard TDA7297 can work for low power (<12watts)
http://www.aliexpress.com/item/New-TDA7297-2-15W-Audio-Amplifier-Board-15W-15W-2-Dual-Channel-DIY-Free-shipping-Airmail/980964823.html
http://www.aliexpress.com/item/1pcs-New-Version-A-AC-DC-9V-15V-12V-15W-15W-TDA7297-Dual-Channel-Amplifier-Board/1133420619.html
Or a LM38xx series for high power but needs dual rail PS.
Yuan Jing Audio - LM3886 + Power Regulator Board [68W + 68W] - $30.90 - Stereo
Or two of these 10 watt kits if you like making your own amp and like ease of PE ordering with your drivers.
http://www.parts-express.com/class-ab-10w-mono-power-amplifier-kit-tda2030--320-336
The slot vent on your sub is a little narrow at 1/4in - go bigger area and longer to reduce vent velocities and chuffing.
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Thanks for the information XRK. The plate amp issue may cause a rethink. All other plate amps I have found are either subwoofer only or very expensive. The availability of the Dayton drove me to the separate woofer design - otherwise I would have done a four speaker design with full-range drivers - maybe the new MarkAudio CHN-70.
And I bought a $50 piece of Cherry plywood yesterday!
And I bought a $50 piece of Cherry plywood yesterday!
stereo dipole in a single cabinet
Saw this auction and thought why couldn't these six sided hexagons be converted to two single cabinet stereo bipoles / dipoles.
How would the rear waves react?
Bose like?
"I'm just saying"
AKAI NDS-70'S OMNIDIRECTIONAL RETRO VINTAGE SPEAKERS MODERN FOSTER FOSTEX
RARE AKAI NDS-70'S OMNIDIRECTIONAL RETRO VINTAGE SPEAKERS MODERN FOSTER FOSTEX ©
Saw this auction and thought why couldn't these six sided hexagons be converted to two single cabinet stereo bipoles / dipoles.
How would the rear waves react?
Bose like?
"I'm just saying"
AKAI NDS-70'S OMNIDIRECTIONAL RETRO VINTAGE SPEAKERS MODERN FOSTER FOSTEX
RARE AKAI NDS-70'S OMNIDIRECTIONAL RETRO VINTAGE SPEAKERS MODERN FOSTER FOSTEX ©
Test out Active XO Bi-amping FAST for FREE!
This is kind of off topic but thought might be of interest to you all: a no-cost active XO bi-amp solution to try out FAST without investing anything more than current PC and amplifier system you have.
Apply a HPF to left channel and LPF to right channel. Connect left amp output to tweeter and right to woofer. Do this in Audacity at the sound file level. Bingo! A no-cost mono-FAST XO system to play with. See more here:
http://www.diyaudio.com/forums/multi-way/261506-using-stereo-sound-card-create-mono-2-way-active-crossover.html#post4047802
This is kind of off topic but thought might be of interest to you all: a no-cost active XO bi-amp solution to try out FAST without investing anything more than current PC and amplifier system you have.
Apply a HPF to left channel and LPF to right channel. Connect left amp output to tweeter and right to woofer. Do this in Audacity at the sound file level. Bingo! A no-cost mono-FAST XO system to play with. See more here:
http://www.diyaudio.com/forums/multi-way/261506-using-stereo-sound-card-create-mono-2-way-active-crossover.html#post4047802
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