Hafler matrix questions. Dynaco / Kenleigh audio QD-2 hardware

QuadraphonicQuad

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kfbkfb

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Cut one of the headphone outputs off, checked the wires with my analog ohm meter, twisted the appropriate wires together, connected it to L+ and R+ on my Pioneer SX-2300 receiver, connected the output to the Polk Audio computer speakers that came with my HP xt953 PC - Hafler/DynaQuad surround sound achieved.


Kirk Bayne
 

Soundfield

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I like your Dynabox. What is the difference between Spatial & Amb(ience)? What kind of blending does the front panel knob do? Or maybe it's just for level?

One of the best simple designs I've encountered is the original Electro-Voice decoder. A little blend on the front, a lot in the rear (but not total as in Hafler). I think it was successful at giving a listener what they expected when playing stereo "into quad."
Hi Sonik, thanks. I really only build these boxes to make it easier for non technical friends to connect the rear channel speakers without the risk of them shorting their amps out! This is the circuit of the one shown –
haflerbox.JPG



As you can see, the front panel switch swaps between pure Hafler connection and the variant introduced by Michael Gerzon (which he called spatial stereo) blending the front channels into the rear by an amount controlled by the “Spread” knob. But most of the complication is due to the fact that this particular friend was going to use a dedicated amp for the rear channels in order to provide full control over rear channel volume (sensible, as the chief failing of passive Hafler is the inability to increase the rear channel level WRT to the front). But this chap had read that if you did that, the strange load presented to that rear amp could make it unstable and wanted load resistors to normalise the load seen. I don’t think it’s necessary but I was happy to include them (along with a switch to remove them to prove they weren’t needed!)
 

jaybird100

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No. The front channels are totally untouched in a Hafler set up. As Par4ken said, bass is usually mixed to both front speakers in a stereo recording (so it appears to come from 'the middle') and so would cancel out in the rears. If the bass was only in one channel, then it would also appear in the rear speaker. This is another reason you want your front speakers to dominate the sound. In this set up you want the soundstage to remain in front of you.

Jaybird, it doesn't sound like Brjoon is trying to play quadraphonic recordings and even stated that he wasn't real clear on what 'quad' means. He is just trying to add some surround elements to his stereo recordings. (And there is nothing wrong with that and should enhance his stereo listening experience.)
Absolutely nothing wrong with enhancing stereo recordings by "decoding" them. We do it all the time! That's a nice advantage of matrix quad.
 

par4ken

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As I said before, a lot of early seventies audio equipment especially the budget stuff boasted of Quad sound (via Halfler/Dyna) speaker connections. Even car stereo such as this Sanyo Cassette deck form the early seventies. Photo is showing the bottom of the unit.
s-l400.jpg
 

Sonik Wiz

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jefe1

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Interesting. I have one Longines quad album I found in a thrift store. Picked it up just because. I will have to give it a listen now.

Reminds me of another oddity I have a 3 record set of childrens music songs recorded in QS dont remember the label.
I recall that on the last album side the house band started to rock out and just jammed not too bad at all.
 

jaybird100

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Interesting. I have one Longines quad album I found in a thrift store. Picked it up just because. I will have to give it a listen now.

Reminds me of another oddity I have a 3 record set of childrens music songs recorded in QS dont remember the label.
I recall that on the last album side the house band started to rock out and just jammed not too bad at all.
I have that one, too. It's not immediately accessible, or I'd tell you the marketing company. I found it in a thrift shop, and was surprised that it was still in great condition. "Cock-a-doodle-doo and Mother Goose, Too" is the title of the set.
 

brjoon1021

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Brjoon, were you referring to 3dB of separation across the front or rear speakers? I believe a passive system, such as the QD2 uses, should still provide full separation across the front. 3dB is the minimum amount of separation that the human ear can discern. That would be the same as the original Dynaco decoder. When Dynaco originally introduced the system, they marketed it as a way to extract a surround effect from stereo recordings. That it can also use the phase differentials in matrixed quad recordings to deliver a decent, although not accurate, quad effect from SQ and QS recordings, can be a "gateway" to see if you truly like the effect. That's what hooked me on quad, and I've never looked back.
I thought that it was 3db between the two rears to give a hint of localization as opposed to just "behind me" Kenleigh seemed to suggest that this was his wisdom, but I am not surprised to hear that it was there all the time in the Dynaco. Mine is a Dynaco, with some Connections changed to line level it would seem
 

brjoon1021

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Absolutely nothing wrong with enhancing stereo recordings by "decoding" them. We do it all the time! That's a nice advantage of matrix quad.
Hi,
Thanks. What about phase cancellation ? you have two pairs of bass drivers pointing right at each other (fronts and rears). I was just curious as I hope to get this done in the next week or so and find out for myself.
 

jaybird100

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I thought that it was 3db between the two rears to give a hint of localization as opposed to just "behind me" Kenleigh seemed to suggest that this was his wisdom, but I am not surprised to hear that it was there all the time in the Dynaco. Mine is a Dynaco, with some Connections changed to line level it would seem
That's what I thought; 3dB across the rears. It's just enough to perceive.
 

Soundfield

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That's what I thought; 3dB across the rears. It's just enough to perceive.
A pure Hafler connection only derives a mono (L-R) signal for the rear so if you choose to use two rear speakers to reproduce it there is zero separation across them. You can blend in some of the front stereo signal into the rear which will give a sense of separation but at the expense of front to rear depth.
 

par4ken

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Hi,
Thanks. What about phase cancellation ? you have two pairs of bass drivers pointing right at each other (fronts and rears). I was just curious as I hope to get this done in the next week or so and find out for myself.
Most recordings employ mixed bass, so with the Hafler system there will not be a lot of bass from the rear speakers to begin with, i.e. the in phase bass signals cancel via the "speaker" matrix. If less than full L to R blend is applied the uncancelled bass will still be in phase with the fronts.

If a recording has bass in one channel only (not too common) then you could get that situation with reverse phase woofers and some bass cancellation effect.
 
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