Dumb K-horn Center Channel Question

[Gregg357]

When the Heresy came out as a center channel for the Khorn, music was in a 2-channel format. How was that center Heresy connected, if not driven by its own amp? Was it + from R spkr and L spkr to + of C spkr : - from R spkr and L spkr to - of C spkr, so the center wasn't directly connected to the 2-channel amp? Or, was it sourced direct from the amp in a similar fashion as described above? Or, other?

[Frzninvt]

It was connected using a circuit that Paul Klipsch designed and buily that summed the two channels for a mono center. I have seen the diagram on the forum. You needed a third amp if I am not mistaken.

That said I have done it in my car audio days using the + on one channel and - on the other and used an L-Pad to control the volume level with good results.

Some amps may not like it though.

[Captn Bob]

Ideally, you would come out of your center channel output - a lot of amps and preamps of the time, like the McIntosh MX 110 and Scott 299c had one - and connect it to a dedicated mono power or integrated amp In the late fifties, early sixties, there were a lot of those floating around cheap.

Failing that, PWK had the circuit described above - you connect the + terminal on the center speaker to the - terminal on the left speaker and the + terminal on the center speaker to the - terminal of the right speaker. The - terminal of the center speaker then returns to the amp.

Not all amps like this arrangement. Audio Research and HK Citations come to mind. You will let out copius amounts of smoke. You need an amp with a common ground or neutral.

[RagingBullWinkle]

Another way to skin the cat is to find 3 mono blocks that have both in and outputs.

I went this rout when I could not find a pre amp with the center.

Side note: A lot of people told me the Heresy III would not keep up with the K-Horns.

I could not be happier with my set up..

The Mono blocks I used are Hibachi's with a C2300 pre amp. I paid about 1200 for the three. Tube pre amp is a must.

http://www.angelfire.com/biz/bizzyb/HIBACHI.html

[steve]

I went the route of having a two channel tube amp run the KHorns, and another tube amp (same amp, but wired in mono) run the center, which is a Belle..which I also believe does a better job as a center, since the specs match the KHorns. My tube preamp has two syereo outputs, so output A goes to the stereo amp, and output B goes to a mini stereo to mono box (homebuilt by forum member Tom Mobley) and then to the mono amp. The mini box has a built in attenuator so I can control the signal level to the center, which I have set to about 5db less than the KHorns. It's there, but it doesn't announce it's prescence. Like a properly set subwoofer.

I used to own a Scott preamp that had a built in mono output, which was less hassle, but I enjoy this set up more. There is a diagram on this forum how to build the minibox, if you're interested.

[Invidiosulus]

[WMcD]

Sorry Greg, I don't quite understand your description.

In one article he was showing that L+R summing was working as well as L-R on two-channel two-microphone recording. The L-R could be easily achieved by wiring the center to the hot (red) output of the stereo amp. The pictures of the oscilloscope pattern showed the two channels of the music were random in phase and therefore sum versus difference didn't matter.

That apparently did not last long because he went to L+R information for the center. Although his X-Box (not the simple summing resistance network) had switches to allow comparisons. There were ways of slightly modifying the transformer connects on tube amps to allow L+R to be extracted without an extra amp. At least one amp had a special transformer to do this. Scott?

It seems to me that the L-R theory of operation became a big loser when pop stereo recordings mixed the singer to hard center or L+R (mono) in stereo records to put the singer n the middle of the sound field. If the center channel was responding to L-R, the singer mixed L+R would result in no acoustic output in the center speaker. I believe that some orchestral recordings used a microphone in the center position mixed mono and this would create the same problem with L-R.

Incidentally, you may have seen adds in old hi-fi magazines for a magic box which claims to remove vocals from recording so you can sing along. Maybe the precursor of Karaoke night at the neighboorhood gin mill. I expect it was using a L-R mix

The center channel speaker theory (originated by Bell Labs) and championed by PWK has always had a strong following, if a small one. A review of what was called the Cornwall II at the time reported on it.

Eventually, Dolby 5.1 for home use (and theater) extracted L+R to send to a center and now we're enjoying it on a larger scale.

FYI one way of getting a L+R with just wires was as follows. The red inputs of the speakers are wired to L and R outputs of the amp. The black inputs were wired together. Normally these would go to the ground of the amp. But instead, this junction was wired to the red input of the center speaker and the black ground of the center speaker went to the ground of the amp. In this fashion, the ground "return" from the flanking speakers was sent through the center speaker. However, this ruined the damping factor and also introduced cross talk. Different impedances of the speakers over the audio band would cause problems. Further, the left and right speakers are receiving some of the signal meant for the other side. PWK would never have liked this, IMHO

WMcD

[artarama]

If you have a preamp that has two pair of main outs, you can run an additional amp dedicated just for the center.

Use only one side of the center amp, I have always used just the right channel and then switch the center amp to mono. Set the volume on the center amp to your liking, something below the volume level of the two side (flanking) speakers. Now everything is controlled by the preamp just as before.

[IB Slammin]

Bob,

Lets not forget the Saul Marantz first SS preamp and the three matching SS mono blocks. The 7T preamp, with the 60wpc mod 15's under a face plate for flanking and the 60wpc mod 14 for the center.[]

tc

[Captn Bob]

Or for that matter, three Model 5s - the amp PWK took with him to Europe for the World's Fair. He said they had trouble with the Russians trying to sneak into the exhibit and seeing just how loud Klipschorns could go. I assume they were never disappointed.

Several of the early Marantz ss preamps had center outs, like the 7-t you mentioned, and the 33 and 3300. Both of the latter were pretty good sounding, and are kind of underpriced nowadays.