JohnA Posted June 6, 2017 Share Posted June 6, 2017 i think I once had a Radio Shack add-on box that generated a center channel from stereo. What is/was available to do that? Quote Link to comment Share on other sites More sharing options...
mark1101 Posted June 6, 2017 Share Posted June 6, 2017 I have a PWK "minibox" built by forum member Dr. Bill if you are interested. I don't use it anymore. But it combines left and right channels and produces a mono center signal. Quote Link to comment Share on other sites More sharing options...
baron167 Posted June 6, 2017 Share Posted June 6, 2017 I have a Pioneer SX-9000 with a center channel out. 3 Quote Link to comment Share on other sites More sharing options...
muel Posted June 6, 2017 Share Posted June 6, 2017 Volume 14 #4 from the Dope from Hope: http://audioroundtable.com/misc/DOPE_from_HOPE.pdf Searching for "dope from hope" turns up nothing in search which is strange. https://community.klipsch.com/index.php?app=core&module=attach§ion=attach&attach_id=47088 I think there are enough people here who have built them that you might get a response with a WTB in the Garage section Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted June 6, 2017 Share Posted June 6, 2017 Something a little more sophisticated than a summed center is the SST Trinaural processor. http://www.sst.audio/trinaural 3 Quote Link to comment Share on other sites More sharing options...
ClaudeJ1 Posted June 6, 2017 Share Posted June 6, 2017 31 minutes ago, Wardsweb said: Something a little more sophisticated than a summed center is the SST Trinaural processor. http://www.sst.audio/trinaural So have you tried one? Quote Link to comment Share on other sites More sharing options...
Schu Posted June 6, 2017 Share Posted June 6, 2017 how would a mechanism that sums the channels be different than merely wiring in series or parallel? that means additional processing... Quote Link to comment Share on other sites More sharing options...
babadono Posted June 6, 2017 Share Posted June 6, 2017 From SST Audio: Proper implementation requires re-vectorization of the composite stereo information for three channels ----- And this is done without "processing" More Quote Link to comment Share on other sites More sharing options...
Schu Posted June 6, 2017 Share Posted June 6, 2017 let me google "re-vectorizing" 1 Quote Link to comment Share on other sites More sharing options...
muel Posted June 6, 2017 Share Posted June 6, 2017 Whatchur vector Victor? 3 Quote Link to comment Share on other sites More sharing options...
babadono Posted June 6, 2017 Share Posted June 6, 2017 Roger Roger 3 Quote Link to comment Share on other sites More sharing options...
hsosdrummer Posted June 6, 2017 Share Posted June 6, 2017 3 hours ago, muel said: Volume 14 #4 from the Dope from Hope: http://audioroundtable.com/misc/DOPE_from_HOPE.pdf It's in the link above, on pages 41 - 46. In 1980 I built the summation network exactly as shown in the DFH, used it with Khorns left & right and a Cornwall center (powered by 3 Luxman MB3045 tube amps), and it worked beautifully. The only circuitry in the network is a couple of resistors; no "processing" involved. This creates a derived 3-channel system, since the center info is derived from the left and right, as opposed to being discrete from the source. The derived 3-channel system produces sonic results that are a class above those possible from a straight 2-channel system. It widens the "sweet spot" so that more than one listener can enjoy the stereo perspective. It solidifies the center of the soundstage, producing much more precise 3-dimensional placement of all the elements in the recording. And the center speaker volume control on the summation network provides the listener with control of the stereo soundstage, allowing them to "dial-in" the left-to-right spread until all the sonic elements are evenly spread from extreme left all the way to extreme right, regardless of the recording. The further apart the left and right speakers are, the more important this becomes. PWK talked a lot about the "hole in the middle" of the 2-channel stereo soundstage; a 3-channel system eliminates this, and allows systems to be successfully implemented in larger rooms and on longer walls without sacrificing stereo soundstaging. The net effect of upgrading from 2-channel to 3-channel is that the 3-channel system creates a solid "curtain of sound" that extends from side to side, with each sonic element rendered precisely in 3-dimensions regardless of where it is located in the recording. If you do it right, the difference will be staggering, and you'll never go back to plain-Jane 2-channel stereo. 1 Quote Link to comment Share on other sites More sharing options...
Frzninvt Posted June 6, 2017 Share Posted June 6, 2017 I used to sum a center channel in my car audio days buy using the positive (+) of one channel of the amplifier and the negative (-) of the other connected to an L-Pad and then the speaker it worked great for my a/d/s L200i center speaker between two a/d/s 346is's. Then I got ahold of an Audio Control System 90 Model 11 unit that handled it all with an spatial restorer and built in amplifier. 3 Quote Link to comment Share on other sites More sharing options...
mark1101 Posted June 6, 2017 Share Posted June 6, 2017 40 minutes ago, hsosdrummer said: It's in the link above, on pages 41 - 46. In 1980 I built the summation network exactly as shown in the DFH, used it with Khorns left & right and a Cornwall center (powered by 3 Luxman MB3045 tube amps), and it worked beautifully. The only circuitry in the network is a couple of resistors; no "processing" involved. This creates a derived 3-channel system, since the center info is derived from the left and right, as opposed to being discrete from the source. The derived 3-channel system produces sonic results that are a class above those possible from a straight 2-channel system. It widens the "sweet spot" so that more than one listener can enjoy the stereo perspective. It solidifies the center of the soundstage, producing much more precise 3-dimensional placement of all the elements in the recording. And the center speaker volume control on the summation network provides the listener with control of the stereo soundstage, allowing them to "dial-in" the left-to-right spread until all the sonic elements are evenly spread from extreme left all the way to extreme right, regardless of the recording. The further apart the left and right speakers are, the more important this becomes. PWK talked a lot about the "hole in the middle" of the 2-channel stereo soundstage; a 3-channel system eliminates this, and allows systems to be successfully implemented in larger rooms and on longer walls without sacrificing stereo soundstaging. The net effect of upgrading from 2-channel to 3-channel is that the 3-channel system creates a solid "curtain of sound" that extends from side to side, with each sonic element rendered precisely in 3-dimensions regardless of where it is located in the recording. If you do it right, the difference will be staggering, and you'll never go back to plain-Jane 2-channel stereo. There was a retired priest here on the forum who was known as Father Bill............but preferred to be called Dr. Bill. He was an electronics buff too apparently and knew PWK. He used to build those PWK mini-boxes for forum members to derive the 3rd channel for situations where the L/R speakers were too far apart. Just what you are speaking about above. He built neat little boxes with some speaker terminals for inputs, and an RCA output jack and volume pot. I was lucky enough to get one. This was probably 10 years ago or more. 2 Quote Link to comment Share on other sites More sharing options...
babadono Posted June 6, 2017 Share Posted June 6, 2017 PWK's circuit is a non active summing circuit. Super easy to build your own if you can but solder. All old mixing desks contained these until the advent of the active opamp based summing circuit. The advantage of the opamp summer is no signal from one channel bleeds over into the other channel. With the passive resistive adder you will get some bleed over. It's not rocket science but it is electronic engineering. Quote Link to comment Share on other sites More sharing options...
tromprof Posted June 6, 2017 Share Posted June 6, 2017 Rolls makes a small mixer that will also do it. I used it for a time for a La Scala center between 2 widely spaced Klipschorns. I believe this is the one: http://www.rolls.com/product.php?pid=MX41b Worked quite well Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted June 6, 2017 Share Posted June 6, 2017 They are multichannel avr's, lol. Quote Link to comment Share on other sites More sharing options...
babadono Posted June 7, 2017 Share Posted June 7, 2017 1 minute ago, derrickdj1 said: They are multichannel avr's, lol. But they don't synthesize a center channel like this technique does do they? Old McIntosh preamps had a center channel output and you had to slide the chassis out of the case part way to access the secret center channel level control. Mine got stolen ages ago when I first moved out here, don't know if they still make'em that way. Can't afford Mac gear anymore, why look? Quote Link to comment Share on other sites More sharing options...
Coytee Posted June 7, 2017 Share Posted June 7, 2017 They demo'ed this once at HQ in Indy. My gut feeling of it would be that I personally, wouldn't like it when listening to something that panned hard left and hard right. (think some Queen where the voices bounce back/forth) Though they didn't demo any music like that, I had the feeling it would not bounce from left to right but would go from center to left or center to right... (or something odd relative to the original signal) I certainly might be misunderstanding how it works but that was my thoughts when I heard it. Quote Link to comment Share on other sites More sharing options...
babadono Posted June 7, 2017 Share Posted June 7, 2017 2 hours ago, tromprof said: Rolls makes a small mixer that will also do it. I used it for a time for a La Scala center between 2 widely spaced Klipschorns. I believe this is the one: http://www.rolls.com/product.php?pid=MX41b Worked quite well So you put the left channel in one input and the right in another and the output was a summed signal? Did you use TS or TRS plugs? Quote Link to comment Share on other sites More sharing options...
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