Jump to content
The Klipsch Audio Community
Sign in to follow this  
Cathedral Guitar

HERESY: Center Channel in a 1957 MONO System???

Recommended Posts

On 4/9/2020 at 11:45 AM, JRH said:

Prior to the Belle, PWK used a WALNUT LaScala as a center.  I have it.

 

And You Suck!  😁

  • Like 2

Share this post


Link to post
Share on other sites

I took a look at the on-line Allied Electronics catalog from 1958.  There are a few stereo tape machines.  There are a few packages of a stereo pre-amp and two mono amps and just one stereo power amp as part of a package..  Two speakers areap  included.  No mention of stereo vinyl.  

 

I dont find any three channel equipment or applications mentioned.

 

Of course what PWK used in any specific year must have been a work in progress.

 

We see from the photo that he used different models in his array.  It must have been part of an "add-on" theory.

 

All this amplification was getting expensive.  Maybe a third (center channel) could be extacted from  a two channel amp.  In early days he just connected the center speaker between the two hot (red) terminals of a stereo amp.  Therefore the speaker was putting out Left minus Right.  He published an article showing that the random.phases involved made this indistinguishable from Left plus Right.  But that random phase situation changed with use of a microphone for the solo singer which made him a L plus Right signal. When put through the Left Minus Right system described, he would be eliminated.

 

 

Engineers, later, must have mixed stereo so that the singer was solid center, meaning in Left minus right the system cancelled him out.  His phase was not random.

 

PWK apparently abandoned this Left minus Right and went with Left plus Right in the bridging system.  This was accomplied by rewiring the output transformer of one side, say the Right one, to invert polarity.  Therefore the bridge resulted in Left minus a minus Right. = Left plus Right.  The Bell Lab system which he references used this.

 

 

Probably people didn't like the idea of messing with their amps and the center channel minbox resistor system was advocated by him.

 

WMcD

 

 

Share this post


Link to post
Share on other sites
On 4/7/2020 at 7:27 AM, Cathedral Guitar said:

Was it for home stereo, or for theaters and other professional installs?

 

Just because you mentioned theaters, I'll mention that:

  • Starting in 1953, 35mm CinemaScope had magnetic 4 channel stereo -- three channels behind the screen, and a 4th for surround that could either play through all the surround speakers at once, or left side, rear or right side.   In cheap theaters, or the boonies, the projectionist had to manually switch them.  In the better theaters, the switching was done in response to a low pitched beep in the surround channel (surround didn't go much below 50 Hz), that, when detected, automatically switched.
  • 70 mm Todd-AO was introduced in 1955, with 6 channel magnetic sound by Ampex, that sounded great!  Ampex hired JBL (then known as Jim Lansing) to design and provide the speakers.  Later the Jim Lansing company licensed Ampex to make the speakers they designed. Todd-AO used 5 channels behind the screen, and a single surround with switching similar to that of CinemaScope.
  • By 1957 we were used to wide, deep, dynamic multihannel in the theater, but heard the vinyl soundtrack records at home in unexciting mono.  When stereo records came out a bit later, those with extra money immediately "went stereo."  Others pooled equipment for a few days at a time.  At the next HiFi Fair, Klipsch showed up with 3 channel stereo from a 2 channel source.  We had to have it!  For one of us it took 45 years.
  • Thanks 1

Share this post


Link to post
Share on other sites

Thanks everybody for all the great info!! Do you understand PWK's comments on on 4-Channel in "Dope From Hope" as talking about configuring Quad with 3x in front and 1x in the rear? I have a bunch of Quad stuff, and have never even thought to try that, as all the outputs label the other 2 channels as Rear L and Rear R. I wonder how he would configure Quad with 3x in front?

Share this post


Link to post
Share on other sites

Interesting.  Would you kindly point me to the DfH, please. 

 

Also maybe you have the schematic for the decoder.  It might be the one requiring furlongs of wire and a variable resistor.  Perhaps there is more than one design.

 

Smile

 

Share this post


Link to post
Share on other sites

I believe this is the referenced Dope from Hope.  Wish I had an original, but fortunately it was reprinted!
 

Dope 740700 Vol 14, No 4 Reprint.jpg

Share this post


Link to post
Share on other sites
On 4/8/2020 at 5:58 PM, DizRotus said:

 

Perhaps Jim @JRH, Andy @HDBRbuilder or Claude @ClaudeJ1 can speak to this.

PWK had a Lascala as a center channel speaker between his K-horns for awhile, until he designed the Belle to replace it.  Belle's Low WAF of the LaScala in her living room is WHAT got PWK to design the Belle in the first place!

 

  • Thanks 1

Share this post


Link to post
Share on other sites
On 4/16/2020 at 10:06 AM, Cathedral Guitar said:

Thanks everybody for all the great info!! Do you understand PWK's comments on on 4-Channel in "Dope From Hope" as talking about configuring Quad with 3x in front and 1x in the rear? I have a bunch of Quad stuff, and have never even thought to try that, as all the outputs label the other 2 channels as Rear L and Rear R. I wonder how he would configure Quad with 3x in front?

When I told PWK that I had a quad system, he told me that the three speaker stereo array is really all one needs, but if somebody really wants to buy four of his speakers for quad he would be happy to sell them four!  He DID recommend to me to add a front center speaker for use, though...especially for whenever playing back stereo source material. 

 

As for how it would be set up with a center channel front and rear....it depends on what equipment you are using to amplify the signal to the speakers!   Center channels are basically just both left and right channel signals going into one center speaker...unless the SOURCE was originally recorded in three channels! 

 

When they set up that TASCAM tape deck in the company listeining room, that is how they did it on the R2R....three separate channels, IIRC!  There was a special demo tape made that way...it had lots of stuff on it...including  parts of Michael Jackson's "Thriller"!  JRH was involved in setting that up...so he should be able to tell you more about it!  It was a specific three-channel recording...being played back thru only three of the four channels on that Tascam deck!...also that recording was DBX encoded.

Share this post


Link to post
Share on other sites

Thanks for this!! I do have a Tascam 4-track R2R, and could try running things to tape in 3-ch. Or I could just just run the outer 2 L/R speakers in stereo, and then run the line out to a separate receiver with a mono button, and just run that center channel in mono. Both are pretty easy to set up try. Of course, I'd be tempted to run the center channel through a multi-band tube compressor before hitting tape.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...