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Center Speakers in 1957


musicook

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"First introduced in 1957, the Heresy, a three-way design, started out as a compact center channel speaker to accompany the Klipschorn® in three-speaker stereo arrays."

I'm new to Klipsch home audio and have Cornwall 1s setup nicely as a 2 channel listening area. I was curious as to why they were introducing center speakers back in 1957.

I keep seeing a lot of Heresy's up for sale, and while in the back of my mind, I think they would look really nice with my Cornwalls, I'm curious as to why center channels were used besides modern day home theater systems.

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Why, because PWK was ahead of his time.

For wide rooms and khorns there could be a hole in the sound in the center because of how far apart the mains were. To fix this he designed a little box which kind of summed the mains into a center channel to fill that hole. It did not have to completely keep up with the mains just fill the hole. In a way almost just the opposite of todays center channel which carries more info and percentage of the sound than the mains

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My understanding is that the term Stereophonic was introduced by Western Electric in 1927.

My further understanding is that PWK felt that Left and Right ONLY channels did not always provide a cohesive enough soundstage for many stereo recordings, especially if the speakers were far enough apart to leave a "gap" in the center.

His "center" was not based upon signals from a third microphone, but rather from a combination of L & R signals to fill in this gap.

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Searching around I don't see a copy of the Klipsch Papers being available. They may have been lost in the new forum.

Basically . .

The need for a third, center channel goes back to at least 1933 when Bell Labs had an orchestra in one city and three speakers in a theater in another (DC and Baltimore?) The project was to recreate the orchestra many miles away. PWK must have be enamored with the concept long before home stereo.

About 1957 the first stereo LP was created. PWK was also making stereo tape recordings about the same time. So that was about the time he created the Heresy as a center. It is worth mentioning that the movie Fantasia (Disney) in the early 1940s had multi channel with the many tracks recorded on a synchronized film machine. But I think there was no real stereo or surround as we know it. Disney was a powerhouse of innovation and I believe the Disney organization has more Academy Awards than any actor, though for technical matters.

In any event, the advantages of a center channel at home for Klipsch was simultaneous with stereo LPs. PWK demonstrated it at Bell Labs, which he called "bringing coals to Newcastle." (BTW, the phrase refers to the fact that Newcastle, England is a coal mining town. So there should be no reason to bring coal to that location.) Bell Labs had originated the idea but it was somewhat forgotten. They loved it. I wonder if there is some publication by Bell memorializing the event.

PWK had many electrical schemes for producing the center Left-Plus-Right channel but the stereo mixer box is the best known. Some electronics manufactures picked up on it and so we see some McIntosh and Scott amps equipped with a center output.

There is a review by a magazine of the "Cornwall II" which is what we know as the mainstream Cornwall where the folks from Hope set up a center channel (three CWs) and the review found it to be the most exciting stereo effect ever heard.

Home theater came to the fore with the VCR particularly when the soundtrack was recorded by an additional video head rather than a linear track. Fidelity was wonderful. The HT stuff was Dolby 5.1. There were really only two tracks recorded but the center was derived from (like the mixing box) from Left-Plus-Right. The surround was Left-Minus-Right and put into two surround speakers. The .1 was a sub. Eventually we got true multi track.

With HT and movies there was the problem that dialog was best put in a center channel speaker just under the display.

Generally the use of a center channel for playback of LPs and CD's can give some weird results. One is that sometimes drummer are recorded such that the drum set takes up the whole soundstage. So you have the drummer with eight-foot long arms with cymbals at the extreme edges. Artto here spoke of it.

If you read the Klipsch Papers you'll see that for a while PWK advocated that a center with Left-Minus-Right was indistinguishable from Left-Plus-Right. This was true of live recording with two microphones. But then came studio recording of pop music where the singer was mixed hard center or Left-Plus-Right. When his Left-Minus-Right system was used, the singer would disappear. So he seems to have dropped that idea.

Purists will say that with a well set up stereo system as far a placement, the phantom image of center location comes through without a center channel. That is true in my experience but the speakers have to fairly close and the room very symmetrical, It helps if the speakers are pulled away from the walls. That is why so many purists have their dinky speakers on stands well out into the room.

Going back to the subject. The third channel center is about as old as two channel. Essentially, real three channel is best, but the derived center can be astonishing better than just two.

WMcD

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Thanks for the welcome and detailed responses. I guess the explanation is not enough for me to justify having some cute little matching Heresy's between my Cornwalls. Unless I have a mixer like the one described and want a karaoke mix set of speakers - to cancel out the center vocals.

I have an interesting listening room layout, which discussion may be better for another post/thread. My cornwalls are in a loft against a wood railing. The loft opens up to the main room downstairs, so there is no wall behind the Cornwalls - just open air space overlooking the living room. I don't know if that's a good thing or bad thing, since they're CornWALLS. I've decided to put my office desk behind my listening couch, so I've spread out the two Cornwalls really wide, so I can listen to music while I work, and the speakers are still directed to my ears, but music has to travel wide enough around my computer monitor in the middle. If I could only mount the center Heresy to the top of my computer monitor (joking).

Before the Cornwalls, I had Bose 10.2's in their place and picked up some old maggies - SMGa's and had them on each side of the desk since the computer monitor blocked quite a bit of sound. Since I've got the Cornwalls and spaced them wide, I'm trying to stick to 2 channels/speakers. So far so good. I'm not missing the 4 speaker setup.

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I also have found pulling my CWs away from the wall helped with the spacial qualities quite a bit... but I am talking inches, not feet. (Between 10-14 inches).

Frankly, I have done the wall of sound thing many times... and while it saturates the LP, it doesnt work for imaging and detail. Obviously HT is much different...

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How did they do it back then with the preamp, amp section? Did the old receivers or separates accommodate the three front speakers?

For three front channels you make a small box- the "Bud" box and add a mono amp for the center speaker.

BudBox_zps0ee270b1.jpg

Cool, sorry if I read over that didn't understand it. Thanks.

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How did they do it back then with the preamp, amp section? Did the old receivers or separates accommodate the three front speakers?

At least one McIntosh pre-amp has a center channel output with a little center volume control on the top of the unit. So then you have to buy a third amplifier. But the theory must be like the Klipsch mixing box. You can't just get center mono by directly connecting together the pre-amp outs without ill effects. If directly connected the Left and Right stereo are connected together and the Left and Right channels are no longer isolated. But if you put in the resistors, there is enough isolation so the Left doesn't contaminate the Right and vice versa.

Larry C IIRC had posted a schematic of a Scott tube receiver or integrated amp (pre-amp and power amp) which was difficult to dope out. My recall is that it had the center channel output for a third amp. It was a tube amp with output transformers and IIRC there was a scheme to drive a third, center amp bridged across the transformers, and give Left plus Right without a third amp.

This is a bit difficult to explain.

If we connect a speaker across the Left and Right outputs, the speakers receives a signal which is the difference between the two channels or Left minus Right. This is simply because of how a two terminal load like a speaker or resistor works. It responds to the difference in voltage at the terminals. For example, if we hook up our normal speakers to an amplifier it is responding to, for example, the Right "hot" or red and the ground or zero volts of the amplifier. So Right hot compared to zero (or minus zero) is just Right. Same with the Left.

So bridging gets us Left minus Right. Unless we do something else as a work around.

The workaround is to wire the output of the Left output transformer in reverse polarity. Now it is putting out minus left, just flipping over the sine wave at all frequencies.

Horrors you say, now my left speaker is getting an inverted signal and is out of phase. Not to worry, we just connect the left speaker inverted with its red to the minus ground and its black to the "high" output. So, that is sort of a double inversion returning things to how it should be for the Left speaker.

But now we can bridge the center channel speaker between the Right output and . . . what is negative or minus Left because the output transformer is wired, inverted.

As before, the center speaker is going to respond to the difference in voltage between its terminals. But it is difference between Right and minus Left. That is to say, Right minus (minus Left). It is exactly like our early math education with numbers. We learned that A - (- B) is equivalent to A + B. So the center channel is now actually responding to Left plus Right. You don't have to buy a third amp. But you will have to use some sort of "pad" to adjust level. Actually the bridging typically between the 4 ohm taps while the mains are connected to the 8 ohms taps. This reduces the level of the center channel.

Anyway. I believe the Scott amp did it this way. You'll also see similar schemes in the Klipsch papers.

These days it is difficult to accomplish because only tube amps use output transformers.

Sorry that got so long. But it does explain some historical things you see.

WMcD

Edited by William F. Gil McDermott
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Thanks WMcD for the much better answer, I only knew the rough idea and didn't know if anyone else would answer, thanks for the details. :emotion-21:

It's pretty amazing really, stereo was brand new and PWK was already working on a center speaker for non perfect rooms.

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Going back to the subject. The third channel center is about as old as two channel. Essentially, real three channel is best, but the derived center can be astonishing better than just two. WMcD

I concur with your history lesson. I had the 2PH3 setup with mono LaScala center between two KCBR flanks for over 30 years, using PWK resistor box. I built mine with a potentiometer in the center only and fixed R and L resistors. I could dial down the LaScala to perfection relative to the R and L.. Wide sound stage was always possible this way no matter where I moved the system. I think the peopel that do 2-channel this way are an even smaller minority than 50 years ago. When I visited PWK, he showed me some old papers from Bell Labs outlining a complete stereo LP playback system with mike, pre-amp, cutter head, turntable, etc. (all tube of course), from back in 1926. It took quite a while for commercial adaptation.

Then DVD came along with 5.1 srurround and I caught the upgrade bug after hearing K402's in 2007. Now I just do 2.1 and the vocals always sound like they are coming out of my HD TV withe the great imaging of the 402's.

Edited by ClaudeJ1
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Building the Klipsch box...more than 10 years ago, if I remember right, was a transformative experience. It consisted then of L and R La Scalas, with a derived center channel using a Heresy. It was a great improvement, IMO, and was used, highly attenuated, so the center fill was very subtle. I did get some mild bass bloat in the middle, which was fixed with an inline capacitor that rolled the Heresy off in the region of 100 cycles or so.

I had built a number of single ended tube amps that worked extremely well in this application.

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My further understanding is that PWK felt that Left and Right ONLY channels did not always provide a cohesive enough soundstage for many stereo recordings, especially if the speakers were far enough apart to leave a "gap" in the center.

No doubt quite true, but I don't know when or how PWK developed the idea. HOWEVER, it was a point of great pride to Paul that his Klipschorns were instrumental to assembling a world-class American stereo system for the Brussels World's Fair in 1958! See http://www.klipsch.com/Brussels-Worlds-Fair The combo of 2 K-horns and a Heresy seemed to be his 3-channel standard.

The list of components is nothing less than astonishing (see the above link, which I can't copy from). K-horns and a Heresy, Marantz pre, amps and stereo controller, Ampex tape machine, and a Fairchild TT and the fabulous 232 stereo cartridge. (I'd never heard of Fairchild turret head tone arms!)

Don Davis (wasn't he with Altec?) was the key person in working with the State Dept to transport HIS PERSONAL K-horn system and those classic electronics and sound sources to Belgium to set it up. Sounds like quite a story!

Edited by LarryC
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