[EDS_]

I'm a huge believer in running a few watts from behind the listing position as a way to infuse music with presence and air.  It's way easier to talk about that to pull off.

I've listened this way for years, recently using a McCormack MAP-1, sadly the MAP-1 appears to be dead.  So I think Frank's Insight and Ultra Bridges can be used to extract surround info.  Am I nuts?

[DustyC]

They are not designed for ambiance extraction. The MAP1 used a variation of the old Dynaco Quad adapter (I think) to provide a signal to a pair of speakers behind or to the side of the listening chair. It's nice because the ambiance is not added on artificially but depends on the available L-R information in the recording.
Find another MAP1. 

[rajacat]

 Dr. Lloyd Peppard of Mapletree Audio has a device called the "Thingy"(hate the name!! ) which may be something similar to what you're looking for.   
 
The "Thingy" crossover and multi-channel driver.
http://hollowstate.netfirms.com/#miscellaneous

[Wayner]

Dynaco had a surround system that was pretty good for the time. It featured 3 speakers in front and 1 in the rear. You really need to have 4 of the same speakers for this to work:



Wayner

[dB Cooper]

It is desirable, but not essential, for the rear speaker to be the same (the fronts must be identical, although Dyna claimed their speakers were pretty much interchangeable). I used a cheap Radio Shack 4" "full range" acoustic suspension speaker placed high on the rear wall and the fronts were placed along the narrow side of approximately a 12" x 18' room. The effect was surprisingly realistic with the right source material. (Try it with good live recordings like The Allman Brothers at Fillmore East.)

[Wayner]

Agreed.

Wayner

[Listens2tubes]

I'll have a look around my parents house for my Quadapter. Would be an interesting experience to try it once again. aa

[oneinthepipe]

I was looking through some of my old LPs and found a few "quadraphonic" recordings.  Of course, the "quad" cartridge and "quad" receiver have been gone for at least 30 years.

[Wayner]

Make sure your amps have common grounded output terminals.

Wayner

[EDS_]

Make sure your amps have common grounded output terminals.

Wayner

Doesn't the common ground architecture only matter if one is going to bridge amps?

[EDS_]

It is desirable, but not essential, for the rear speaker to be the same (the fronts must be identical, although Dyna claimed their speakers were pretty much interchangeable). I used a cheap Radio Shack 4" "full range" acoustic suspension speaker placed high on the rear wall and the fronts were placed along the narrow side of approximately a 12" x 18' room. The effect was surprisingly realistic with the right source material. (Try it with good live recordings like The Allman Brothers at Fillmore East.)

Done right; not too much volume from behind and not too much bass from behind.......the effect is like listening in a bar or church. 

Relatedly, I wonder how great The Allman's would have been if Duane had lived?

[turkey]

Make sure your amps have common grounded output terminals.

Wayner

Doesn't the common ground architecture only matter if one is going to bridge amps?

It matters in a number of cases, not just bridging.

Look at the diagram Wayner posted and you'll see the Dynaco method connects the common terminals of both amp channels together. If you do this with an amp that isn't common-ground, you risk blowing it up.