[Keywestjimmy]

Brian Eno is known for suggesting Left, Right and rear speakers set to play out of phase sounds is ideal. Anyone else agree?

[WGH]

Out of phase rear channel sound was ideal in the 1970's when Brian Eno probably said that because that was the only way to extract ambience. Brian was thinking of the Hafler/Dynaquad setup.
It works but not that well.

By 1982 Dolby Pro Logic Surround Sound ran circles around the Dynaquad.

You can probably still find a decoder somewhere. You can also wire the rear speakers directly but the volume knob is handy.

Dynaco QD-1/IIL...a Decoder Cheap?
http://www.enjoythemusic.com/magazine/equipment/899/decoder.htm

[Keywestjimmy]

Great info...thanks! I'm looking for others doing "surround" with 2-channel systems. Yep. I own both models of the Dynaco. They do pass the information but are limited. I don't use them anymore, since I've found a better solution. No decoder needed or wanted!

Maybe this should titled: Who is doing surround-sound using two stereo amplifiers? 

I now use two rear speakers and a preamp that allows for 2 pre-outs with separate volume controls. (I assume one could use a Y-adaptor if you're careful about impedance--anyone doing this?) For the rear, I run the preamp-out to an amplifier wired to only play the stereo signal difference. Specifically: simply run speaker wire to both +,+ amp terminals to the positives of two speakers. (The negative terminals on the amp are NOT used. Plus I assume the rear amp must be negative grounded, not floating.) Then connect the two negatives of the rear speakers together. Voila, ambience signal only!  The main speakers' volume is controlled independently from the rear ambience. Lastly, I use a simple high-pass attenuator at 2500hz on the rear. Dolby Pro Logic filters and attenuates too--the main improvement over their prior versions, that with discrete volume adjustment and delays. Again, my method requires absolutely no surround encoding. A simple stereo signal only.  2-Channel stereo and home theatre peacefully co-existing.

The result is pure (unprocessed) front L,R channels and beautiful, immersive sound. Soundstage is enhance proportionately. None of the cheesy delays, no fake sound effects from behind you. (Which are the other "improvements" of Pro Logic, DTS, Logic7, etc). As you can guess, this type of rear/side channel set-up does home-theater exceedingly well. There is no downside. I do think you need to have a volume control on the rears as some recordings present with more or less ambience.

My set up is not exactly as Eno recommended. I use two separate amps and I could also use two mono-block amplifiers for the front L,R channels. You cannot do this, if you wire per his suggestion with only one amplifier. His passed full signal and you still need to control rear volume.

Anyone else turned on by using the stereo signal to its full potential? (As you may know, it is impossible with a mono signal to achieve this.)

Note:
I'm not a 5.1 or 7.1 or 9.1 "surround" fan (and the digital encoding added to SACD and other recordings), however, if a recording engineer knows what they are doing (for example Brian Eno's recordings and many live performances) the effect is pretty remarkable. In fact I've found very few regular stereo recordings that don't benefit. If you're looking for a home theater system, but don't want to compromise world-class 2 channel, this is the best solution I've found. Anyone else agree?

[rollo]

Brian Eno is known for suggesting Left, Right and rear speakers set to play out of phase sounds is ideal. Anyone else agree?

  One of the oldest tricks in the book for enhancing 2ch listening as well. Set up two speakers about 2ft apart wired out of phase directly behind your listening chair. The affect is really good.


charles

[Keywestjimmy]

That might be a trick in someone's book, not here.  Using a set of speakers with reverse polarity is distinctly different than the Eno third channel. (Many call reverse polarity out of phase. The concepts are similar, but phase involves the time domain.) Reverse polarity sounds completely different than the Eno third channel.

Eno third channel is a very different animal. It reproduces the part of the audio signal that is NOT common to both Left and Right. It utilizes the out of phase, higher order harmonics captured during the original recording. In layman's terms it's the echo created.

Again, the Eno third channel uses the +, + of the amplifier, not switching positive for the negative. (IE. The negative terminals on the amplifier are not used.)

[dB Cooper]

Out of phase rear channel sound was ideal in the 1970's when Brian Eno probably said that because that was the only way to extract ambience. Brian was thinking of the Hafler/Dynaquad setup.
It works but not that well.


Dynaco QD-1/IIL...a Decoder Cheap?
http://www.enjoythemusic.com/magazine/equipment/899/decoder.htm

The Hafler/Dynaco system worked very well, if...

• you were playing a live recording, and/or...
  
• You had a largish space, as I was fortunate to at the time I was playing with it (I was still living 'at home'), and/or most importantly:
• You ignored the norm of putting a speaker in each corner and used a single rear speaker well behind and above the listening position.

I was fortunate to meet all these criteria. A good live recording could sound great through this setup. The original Dynaquad setup was conceived as follows:



The customary speakers-in-the-corners alternative (a horrible idea then and now) was introduced later for 'marketing' reasons (that's how everybody else was doing it). The front center fill was optional and really only worked properly with Dyna electronics because they had a Blend position on the mono stereo switch which corrected for the center speaker dominating when connected as shown.It also required identical speakers, at least across the front.

One rear speaker worked better than two here because there really was only one 'rear' channel anyway. 'Matrix' quad, of which Dynaquad was but one example, had definite shortcomings, but the Dyaquad system could sound surprisingly good on the right recording.
[/list]

[Keywestjimmy]

A little history is always appreciated. I notice you say this is something you did awhile ago, implying you don't think it's the ultimate set up. Why? I'm looking for others who ARE setting up ambience channels with world-class "2-channel" systems solely because they believe it sounds the best. The fact that it does home-theater (HT) is a bonus. Or if you've tried and do not like it, why? I can find no downside. I don't claim all recordings are improved, but maybe 95%.

Mono recordings can sound fantastic and as noted before, will play zero signal on the Eno third channel. I find it VERY interesting that mono recordings can capture a performance space's acoustical signature--the ambience, ie. a large church or stadium, quite well. However, no matter how good, in mono the soundstage is small and certainly in front of you. It may sound like a church, but mono will never feel like you are in that church.

The Hafler system with front center in my view collapses the soundstage. It almost eliminates depth. The rear is full-range and problematic. Next is the rear level. Putting a cheap volume control on the rear hurts the sound. Using small bookshelf's may help, but doesn't solve the problem of interference with the front speakers.  The impedance is the number one reason the Hafler set up is problematic. Adding 2, 3 or 4 speakers to one amp is difficult for the average audio person and not possible with most systems without sound quality compromise. Lastly, you cannot do Hafler w mono-blocks.

Were we or are we brain-washed to think only name brand systems eg. Dolby Atmos, DTS, Logic 7 or even the simple Halfler circuit can only produce enveloping sound?

Simply put, ALL stereo speakers (L, R systems) play this exact information. The hypothesis is that they do not play it well or at least not ideally. Two speakers up front will produce the ambience to a more or less extent depending on room dampening treatments. Near-field listening (getting closer to the speakers) is allowing more of the ambience signal to be heard over the dominate, direct, in phase L and R.