Three Channel Sound

[toomanyspeakers]

I understand that Paul Klipsch was pictured with a three channel front only setup using to Corner Horns and a Belle for the center.Has anyone tried this setup in this day of surround sound and would a Heresy work for a center channel?

[Parrot]

Even better was when they presented the Jubilee, with three of those across the front.

[WMcD]

This is a perenial subject around the forum. There are always requests for the diagram for the PWK designed mixer boxes.

The three channel works very well. Of course it is specifically used for two channel recordings. The most impressive result is when you go from two widely spaced flanking speakers and put the third in the center.

The effect varies from recording to recording. Of course the recording engineer did not have this set up in mind in most circumstances. The most common effect is that instruments and singers mixed to the center really do get situated there.

E.g. on The Dance by Fleetwood Mac, Ms Nicks is very distinctly in the center. It is sort of spooky. I do believe that any music gets more interesting when you can localize performers and give some analysis of how the whole is made up of parts.

The best level (volume) of the center channel seem to change from recording to recording, in my experience. Part of the multichannel HT experience is the calibration so that relative recording and play back levels are appropriate. If you have a two track recording made in 1970 (to pick a date at random), it may take some tinkering.

The decoding of two channel to three channel is a bit of an unappreciated art. It may be that the consumers, in years past, as a whole, were suffering a bit of sticker shock from the "stereo" upgrade to two speakers and amps. Three was a bit too much.

Gil

[PrestonTom]

Many of us have tried this set up. The results are positive.

A Heresy will work and the results will be quite noticeable. If you like that, then the next step would be horn loaded cabinet (LaScala or Belle). These are preferred since the distortion is comparably low re: your K-Horn. Personally, I use a Cornwall 2 and have been quite happy.

Plenty of threads on the circuit (which can be fairly simple & cheap). You will need an exrta amp. The set up takes a bit of tweaking. The trick is not to turn up the center too much. This set up may also cover up some possible anomalies in the room's acoustics.

Good luck,

-Tom

[WMcD]

Let me bump this a bit.

In Technical Questions there is a review of the CWII. I've pointed out, there, that the reviewer was more enthusiastic about the use of the CWII as a center channel than he was about the speaker itself. At least that is my read.

I'll also point out that the PWK center channel is not an an odd thing in this day of Dolby 5.1 The 5.1 systems use a center channel and thus are following his principles, which he credits to Bell Labs in the first place.

It is just something which works well and is rediscovered by every generation.

Gil

[Parrot]

True, Gil, but 5.1 has a discrete signal for the center, rather than a signal derived from the L and R.

[colterphoto1]

I have a Klipsch brochure that shows a Khorn setup with Cornwall at center. Sadly PWK is not in the photo.

Michael

[Tom Mobley]

I have a pair of unmodified 1960 Khorns in a 12 x 23 living room.

they're on the long wall and I had a hole in the middle effect on most

recordings. I built a matching Mahogany Belle and it fixed it

right up. The presentation can only be described as glorious.

[mark1101]

TooMany,

Yes a heresy will work just fine for a center. I'm using one between a pair of LaScalas. I think it would be better if I use a third LaScala or other horn bass unit, but a heresy isa great alternative.

I think the most important point is that the center channel signal is derived correctly. I'm using one of the PWK designed "black boxes" which was built by a forum member. There is plenty of info on this forum about that circuit.

[psg]

I have a pair of unmodified 1960 Khorns in a 12 x 23 living room.

they're on the long wall and I had a hole in the middle effect on most

recordings. I built a matching Mahogany Belle and it fixed it

right up. The presentation can only be described as glorious.

Someone (forgot who, sorry) in another thread said that the center

speaker was to making the sweet spot bigger, not really to fill a real

void. Yet you say there's a real void, right?

My Khorns are 18' apart and there's no hole. In fact, in most

every stereo recording you'd swear the center channel is working when

in fact it's not.

Strange.

[Hardhead]

I've used the derived center channel with a pair of Klipschorns and a Belle in the middle for 32 years, since I heard it in the listening room at the Klipsch factory in Hope. I didn't believe it would work until I heard it, and it really does sound wonderful. At the time a 3rd speaker and amplifier was a significant investment, but it was well worth it.

If you decide to derive a center channel, make sure the output of the center channel is 6 to 9 dBs below the left and right channels, depending on what sounds best to you (PWK suggested a 6 dB difference), or you'll start getting a mono effect instead of stereo.

While a Heresy will work with your Klipschorns, a higher quality speaker like a La Scala or Belle or even a Cornwall will sound even better. Especially with a better center speaker, moving from a derived 3-speaker stereo system to a discrete 3 channel (or more) system is a natural step. If you start using the 3-speaker setup for multichannel sound like I did--multichannel music and home theater--you'll be glad you have the better center speaker.

When I expanded my derived 3-channel system into a 5.1 system, I didn't want to give up the derived 3-channel system. I bought a high quality switch that I wired with the two resistors that are used to derive the center channel. When I listen to 2-channel material, I switch the signals through the path with the 2 resistors that divide the voltage going to the 3 channels so the center channel gets exactly a -7 dB level. When I listen to discrete 3-channel material, I switch the 3 signals through a direct path without the resistors, and it stays 3 discrete channels. It works very well. Just by turning a switch I can go from 3 discrete channels to a derived 3rd channel without having to touch any level controls.

I strongly suggest you try the derived 3rd channel with the Heresy. After you get the center output level adjusted, you'll see what you've been missing. Then you can decide if you want to get a higher quality center speaker and/or if you want to go multichannel.

If you do some research on this forum, you should be able to see how to build a mixer to derive the 3rd channel. If you can't find it or want someone else to build it for you, just post again.

Good luck.

[Parrot]

My long, thoughtful reply has just been eaten by the forum software.

[psg]

My long, thoughtful reply has just been eaten by the forum software.

I hate it when that happens.

[:@]

[WMcD]

I don't diagree with Parrot entirely. But . . . . there is more to it. (Some people don't mind my technical rantings, so I'll let go here. It is ancient history but you might want to know why things were the way they were. I'm going to mix in a lot of different principles which all converge.)

The original Dolby 5.1 used a sound track with just channels, L and R. That is why some VHS movies are labled as having Dolby surround.

The center speaker got L plus R. The two surrounds were actually mono and were fed L minus R and then delayed by 10 ms. The delay was to fool the ear so that the surround was not localized as coming from the front. The 0.1 was a subwoofer, and still is. This, BTW, is called a matrix system.

I believe this is the scheme in regular broadcast TV where you see Dolby in some reception areas. That is where the second channel is available.

Later there would be steering circuits to enhance the decoding a bit. You can see the problem. The engineer can mix a vocal mike as identical in L and R. It would not show up in the surrond. Crowd noise could be mixed L minus R and not show up in the center. However, strong R or strong L (necessary for the sound stage) would show up at a reduced level in both center and surround. Steering was used to help that.

It is interesting that PWK started making stereo tape recordings and then worked in a center channel. It was a speaker just hooked across the two hot stereo speaker output. Of couse that gives just L minus R. This is not quite what is sought.

He published an article showing that in his live recordings at least, the mono component in the recording (i.e. what was in the center of the stage) was random phase. So the argument was that the minus R was as good as plus R. This is in the Klipsch papers. PWK's recordings were done with two microphones situated L and R.

Later, this argument seems to have been quietly dropped. The later article in the Klipsch paper by John Ergle (sp) used a true L plus R set up. (I posted this long ago.) The diagrams showing test results by listeners show something which I had not believed. It is forward and rear localization from a two channel source.

More specifically, the listeners were able to better localize center performers, as advertised. But, they were also better able to pick out who was upstage and downstage. I thought two channel source, or even three channel playback including the "phantom center" was just a left and right issue.

Probably PWK was correct for his recordings with two mikes. But pop music was not recorded that way. The performers were individually miked and the singer was hard mono or L plus R in a "stereo" reconding. Therefore, the singer would not appear in his L minus R at all, by my logic. I think this is used in the magic boxes you see in old magazines where the singer is removed.

Interstingly, the matrix principle was invented almost as soon as stereo. I cring at "stereo" . It means "solid" in Greek (is that right, Max?) This is why the space a speaker is looking into is measured in steradians, or solid radians.

Mr. Blumlein (sp) used two microphones with different pick up patterns.

One had a figure 8 pickup, front and back. So it could be aimed perpendicular to the stage. (So the pick up pattern is more like the infinity symbol.) The L would be positive voltage and the R would be negative simply by what was hitting the diaphragm: a L minus R source of information.

The other mike was a cardiod which is mostly a very wide pick up to the front. Aimed at the stage, you get L plus R.

In his scheme, you have two channels to store or transmit. A L plus R, which is mono, and L minus R. The first gives you all the mono information. The L minus R picks up some of the house. But if you take L+R and add it to L-R you get just L. If you take L+R and subtract it from L-R you get just R. (Minus a minus is a plus.)

So Blumlein had set up a system which had done all the encoding just by the microphones. If you wanted mono, it was there. If you wanted stereo you had to decode a bit. He was ahead of his time and others would catch up.

This would be revisited when FM mulitplex came to the fore (and stereo TV later). There was already a mono signal. What to do? If we add another transmission channel we could make the original L and the second one R, but then all the mono receivers are just hearing one channel.

Rather, the L plus R main channel was maintained and the second channel is L minus R. When a second channel is sensed, or actually the pilot tone, then the new fangled multiplex receiver knows to do the mixing.

Why is this of any importance, you ask.

Basically, it is because we have roughly 40 or 50 years of stereo recordings which have more information hidden in them than we know. Some of it depends on the recording technique, and it is probable there more by accident than by design. Nonetheless it can improve our appreciation of the music by the simple use of the center channel..

Have a good bird,

Gil

[PrestonTom]

Gil,

That was a thoughtful, and thought provoking, review. BTW a couple of the "pluses and minuses" are inverted - but the context clarifies your intent.

It sparked something in my memory banks about a derived center channel. The summation version for a center is usually used to "anchor" the center of the image when the speakers (L & R) have a large separation. So this takes care of the "hole in the middle" problem. Not as frequently mentioned is that it will also enlarge the listening "sweet spot".

What you sparked in my memory was when I first came across the Bell Lab's etc symposium. One of the frequently mentioned observations was that the third "channel" now gave a sense of depth to the sterophonic image. This has always been intriguing to me. A number of folks get a sense of spaciousnes when there is a bit of de-correlation produced by reverberation, but the reports from the symposium (and these were individuals who could knowlegable and could articulate some of the percepts) was that there was now a sense of depth to the audio-image. The intrigue comes from the fact that this is difficult to explain. The stereophonic image, including the phantom center etc, is well-described / predicted by "stereophony" (as conceptualized and described by Ben Bauer). However, the sense of depth remains elusive in its mechanism.

Bottom line: I know it when I hear it, but I just can't explain it.

Good Luck,

-Tom