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

[jaybird100]

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.

If the subs have phase controls, you could try adjusting that, just on one sub. You'll be able to tell right away when it's right. That will end any fear of bass cancellation.

 

[MidiMagic]

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.

The Dynaquad has a 1.2 dB separation between the front and back channels on the same side, and 1.2 dB separation between the back channels.

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.

There are two reasons that most deep bass is recorded at front center:

- Phonograph recordings allow deep bass only in lateral cutting. Any other location requires turning down the bass to avoid overcutting the groove.

- Bass is best when both stereo speakers are producing it inphase. They fake a much larger speaker.

 

[brjoon1021]

I have had so much going on with year end: taxes, professional education deadlines, Christmas, etc... etc.. that I have not even been able to move on the project.

If anyone is bored or game I think I have a quick easy question, (I think):

Referring to my Kenleigh Audio version of the QD-2 which has line level connection (output) for an amplifier (connection diagram available here in this thread thanks to someone).

Can I run the line level out from my QD-2 to a line level input on my receiver (CD. Tape, Aux, etc...) to use that Receiver to power my sub ? I looked back over your helpful posts and that seems to be the advice, but my first effort failed. I wonder if it is because the AV receiver I have is so complicated that I have a settings issue or if the entire idea of: amplifer > QD-s (by speaker cables) > QD-2 line out (inteconnects) > Receiver line level in > speaker cables to passive sub - is the right connection ?

Thanks for all of your help !

 

[barfle]

I have had so much going on with year end: taxes, professional education deadlines, Christmas, etc... etc.. that I have not even been able to move on the project.

If anyone is bored or game I think I have a quick easy question, (I think):

Referring to my Kenleigh Audio version of the QD-2 which has line level connection (output) for an amplifier (connection diagram available here in this thread thanks to someone).

Can I run the line level out from my QD-2 to a line level input on my receiver (CD. Tape, Aux, etc...) to use that Receiver to power my sub ? I looked back over your helpful posts and that seems to be the advice, but my first effort failed. I wonder if it is because the AV receiver I have is so complicated that I have a settings issue or if the entire idea of: amplifer > QD-s (by speaker cables) > QD-2 line out (inteconnects) > Receiver line level in > speaker cables to passive sub - is the right connection ?

Thanks for all of your help !

That device is more than a bit confusing, given its speaker-level inputs which will vary with the volume control of the amplifier, and the line-level outputs. Truly not how a good engineer would make a commercial product. Anyway, trying to decipher what’s going on there, it looks like you might be taking the output from the decoder and feeding them back into the same chassis you’re using to drive the decoder. While that might work OK if you’re careful about which amplifier you’re connecting to, it’t likely to feedback.

 

[par4ken]

I have had so much going on with year end: taxes, professional education deadlines, Christmas, etc... etc.. that I have not even been able to move on the project.

If anyone is bored or game I think I have a quick easy question, (I think):

Referring to my Kenleigh Audio version of the QD-2 which has line level connection (output) for an amplifier (connection diagram available here in this thread thanks to someone).

Can I run the line level out from my QD-2 to a line level input on my receiver (CD. Tape, Aux, etc...) to use that Receiver to power my sub ? I looked back over your helpful posts and that seems to be the advice, but my first effort failed. I wonder if it is because the AV receiver I have is so complicated that I have a settings issue or if the entire idea of: amplifer > QD-s (by speaker cables) > QD-2 line out (inteconnects) > Receiver line level in > speaker cables to passive sub - is the right connection ?

Thanks for all of your help !

If you are using an AV receiver why not let that do the decoding? What is the point of the QD-2?

I notice they say that the grounds are isolated by the QD-2. To do that it would need to use isolation transformers, high quality ones are not cheap so maybe the high price is justified? It would be nice to see a schematic or at least a picture of the board inside.

The Hafler or Dynaquad speaker connection has the advantage of being dirt cheap. To complicate the unit with low level outputs derived from speaker feeds you lose that one advantage, creating sort of a hybrid unit with no advantage over an active decoder circuit.

 

[brjoon1021]

If you are using an AV receiver why not let that do the decoding? What is the point of the QD-2?

I notice they say that the grounds are isolated by the QD-2. To do that it would need to use isolation transformers, high quality ones are not cheap so maybe the high price is justified? It would be nice to see a schematic or at least a picture of the board inside.

The Hafler or Dynaquad speaker connection has the advantage of being dirt cheap. To complicate the unit with low level outputs derived from speaker feeds you lose that one advantage, creating sort of a hybrid unit with no advantage over an active decoder circuit.

Thanks for your response but I want to use the QD-2

 

[brjoon1021]

That device is more than a bit confusing, given its speaker-level inputs which will vary with the volume control of the amplifier, and the line-level outputs. Truly not how a good engineer would make a commercial product. Anyway, trying to decipher what’s going on there, it looks like you might be taking the output from the decoder and feeding them back into the same chassis you’re using to drive the decoder. While that might work OK if you’re careful about which amplifier you’re connecting to, it’t likely to feedback.

Thanks for your response.

"it looks like you might be taking the output from the decoder and feeding them back into the same chassis you’re using to drive the decoder."

No

Here it is:
Audible illusions pre-amp > (interconnects) to Counterpoint Amp > (speaker cables) to QD-2 speaker input > line lever sub out (interconnect) > Receiver line source line level input such as "CD" , "Aux" > speaker cables to passive subwoofer.

Can the blue italics connection above work ? Is that how to do it ? The whole reason for using a receiver rather than an amp is for volume control - I want to be able to turn the sub up or down depending on the music I am listening to. Also, having a "bass" tone knob on the reciever running the sub might come in handy too.

Thanks

 

[MidiMagic]

That device is more than a bit confusing, given its speaker-level inputs which will vary with the volume control of the amplifier, and the line-level outputs. Truly not how a good engineer would make a commercial product. Anyway, trying to decipher what’s going on there, it looks like you might be taking the output from the decoder and feeding them back into the same chassis you’re using to drive the decoder. While that might work OK if you’re careful about which amplifier you’re connecting to, it’t likely to feedback.

No. You need another stereo power amp.

 

[barfle]

Thanks for your response.

"it looks like you might be taking the output from the decoder and feeding them back into the same chassis you’re using to drive the decoder."

No

Here it is:
Audible illusions pre-amp > (interconnects) to Counterpoint Amp > (speaker cables) to QD-2 speaker input > line lever sub out (interconnect) > Receiver line source line level input such as "CD" , "Aux" > speaker cables to passive subwoofer.

Can the blue italics connection above work ? Is that how to do it ? The whole reason for using a receiver rather than an amp is for volume control - I want to be able to turn the sub up or down depending on the music I am listening to. Also, having a "bass" tone knob on the reciever running the sub might come in handy too.

Thanks

It seems like that ought to work, then.

If you’re using a receiver’s amp section for the sub, I’d probably pick the tape monitor input (terminology may vary) instead of one of the AUX inputs, simply because it’s later in the signal chain, with fewer switch contacts to cause trouble.