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4 channel sound with stereo receiver

 

Anonymous
 
Hi I have a Harman Kardon 3380 stereo reciver that puts out 80 watts x 2 rms at 8 ohms. Currently i have a pair of cerwin vega v12-f floorstanding speakers connected to the A speaker terminals. They are 8 ohm compatible, can take up to 300 watts and are very sensitive at 98db. My question is can i connect another pair of the exact same speakers to the B speaker terminals to have 4 channel stereo sound playing simultaneously? The receiver is rated to handle a 4 ohm load but would having these 4 speakers playing at the same time put to much stress on the power supply? I want to play these pretty loud for movies and i don't want to get a HT receiver.

Thanks for any response
 

Bronze Member
Username: Hokievt

Post Number: 56
Registered: Aug-04
Yes you can. Is it as good as surround? No. But you will feel the movie.
 

Anonymous
 
ok thanks does anyone else have an opinion on doing this? Will the resistance ever drop below 4 ohms with these four speakers?







 

Bronze Member
Username: Hokievt

Post Number: 58
Registered: Aug-04
Playing the 4 speakers will not stress it unless you really crank it up. I do it all the time.
 

J. Vigne
Unregistered guest


If you have the A and B speakers set up as two pair; one pair in front and the other pair in the rear, with both being driven by the same source and same amplifer you are going to have voices and all sound effects that should be in front of you also coming from behind you. The pair of speaker that is closest to you will be the speakers you hear the most. That would not be listenable to me. Why don't you research a passive surround wiring system and get some sense of surround?



 

Anonymous
 
That is a good point but i would also like this setup for loud music too. I am not sure what a passive surround system is or how it works. I'm not new to audio equip. but i have never heard of this type of setup. What does it involve? Also would it be unreasonably expensive?
Thanks
 

Gold Member
Username: John_a

Post Number: 2380
Registered: Dec-03
Try simple Hafler connections for rear ambience.

For the "surround" pair, you connect the left surround speaker + terminal to amp "speakers B" L +, the right surround speaker + terminal to amp "speakers B" R + .

Then you connect the two - terminals of the surround speakers.

This presents the out-of phase information to the speakers, which should be placed behind you, and need not be such good quality as the mains. If they are too loud, you can put an attenuator in the path connecting the two speakers' - terminals.
 

J. Vigne
Unregistered guest


Thank you, John. The student becomes the teacher. Hafler is the main person responsible for Dynaco. If you will place "DynaQuad surround" in a search engine you should get the information you will require to make these connections.



 

Unregistered guest
What? The 2 speaker - are connected to each other, the left speaker + is connected to the amp left +, the right speaker + is connected to the amp right +? Nothing connects to the amp -.One loop from amp output positive to amp output positive? You're kidding?
 

Unregistered guest
Years back, ran into a guy that had this set up:
http://www.dynaco.com/Merchant2/merchant.mv?Screen=PROD&Product_Code=QD-2&Catego ry_Code=

Had no idea what it was; it sounded OK.
Believe it is what the others have suggested.
 

Gold Member
Username: John_a

Post Number: 2383
Registered: Dec-03
dennisnate, Anonymous,

No kidding. Try it.

dennisnate, you have it; I double-checked.

I learned it from my Armstrong amp manual from 25 years ago. That was a quality amp. It has a diagram, but I gave it you in words.

It goes on:

"...Results vary according to the amout of out-of-phase information on the record or in the FM broadcast...Four channel matrix records can be particularly pleasing....Some experts prefer a Hafler circuit to genuine 4 channel systems for natural ambience..."

"I you find the rear channel is too loud and obstrusive a 25 - 200 Ohm potentiomenter may be connected in the place shown in the diagram..." [I wrote it in words] "....Connect one wire to the centre tag and the other to either the left or right tag...." [that refers to tags on the potentiometer] .

I have not tried this for years, but I think it will work very well with modern stereo radio broadcasts and especially videotapes marked "Surround sound" or similar. There, the engineers are deliberately managing the out-of-phase info in the stereo signal, to give surround sound effects from digital phase decoders. I think "Pro-logic" and other proprietory systems are not doing much more than a Hafler connection.

And with Hafler, it is all still analogue. The main channels are intact, as nature intended, and the surround is generated without having an A-to-D converter to send the signal into the digital domain, for processing.

That has to be a good thing. Don't you agree, J.V....?!
 

J. Vigne
Unregistered guest



The Dynaco circuit is the predecessor to Dolby Surround, which was the first Dolby surround format used. (The original Dolby format was Dobly Stereo.) I indicated in another thread Ray Dolby took what David Hafler was willing to give away free in many articles and publications and Mr. Dolby has made millions and millions off the same circuit. The original Hafler/Dynaco circuit was, as John points out, all analog. It used the difference signal to create the back channels of ambient information. Since it was only difference signals it was exremely effective, given a good source, at keeping vocals from leaking into the rear channels. When Dolby took the idea and turned it into Dolby Surround it was using the same signals procesed digitally. When that circuit made its first change it became Dolby Pro Logic Surround. This added the summed signals (those signals that are alike) and focused them into the center channel. This was taken from an analog connection that was established by Bell Labs and later Paul Klipsch to create what is known as a phantom center channel. I believe you can still find that diagram on the internet also. (It amounts to hooking the two positives together.) Both circuits were very effective at what they tried to accomplish and, because they are analog, they don't have the tracking problems of the later digitally matrixed formats. They will not do what a true discrete format will accomplish but they beat the early Dolby products in many people's opinion.
The box pictured in the link was the Dynaco circuit with the refinements that were made as the idea became more flexible. It allowed the surround circuit to be switched out and the speakers could then be used as two stereo pair. It also included a volume control for the rear channels instead of a fixed resistor value. It had a thrid control that allowed the user to adjust how much difference signal was injected into the rears which gave the user the ability to remove sounds that over zealous mixing engineers had panned and phase looped into a difference signal. The Dynaco circuit is from the late 60's. The phantom center channel circuit is from the 30's.
If you wish to try this circuit I would contact HK and ask if there is any reason your reciever cannot be run with the needed connections. This circuit relies on a common earth ground to both channels. This is a typical manner for recievers design but you want to ask if there is any separation of the two channel's ground paths that might cause a problem.
NPR ran a story that Ray Dolby is about to retire and is thinking of ofering the company as a publicly traded stock to cover the inheritance taxes that his benefactors might incur. Dolby's main income is from licensing fees which, like THX, run in the $100's of millions each year. The IPO is expected to be worth over $1 billion.



 

Gold Member
Username: John_a

Post Number: 2386
Registered: Dec-03
Great stuff, J.V.

I have just read a UK movie mag "Empire" from 1993 where Dolby Pro Logic is claimed to be "state-of-the-art"; there was no true multichannel, then. I think that is where we get this ridiculous center channel; before that it was 4-channel; only common sense. There were some extremely naff speaker designs, and systems for getting surround. Basically from Nicam stereo on VHS tapes. Although the mag was saying Laserdisc was about to take off, as it was doing in US and had already in Japan. It never did, in UK, really.

I would not mind betting the simple Hafler connection does a good job with stereo, and especially "Dolby surround". If I had a spare pair of speakers I would try it myself.

Quite how Dolby manages the get its name on things I have no idea. We have a DVD of an old TV series which announces it is in "Dolby Mono". I suppose they are selling reassurance of brand recognition. What a gullible lot we all are.
 

Anonymous
 
thanks for the info guys. I might try that connection and see how i like it. Would it be safe for the receiver to hook it up that Hafler way with the 4 speakers?





 

J. Vigne
Unregistered guest


Suprisingly, Dolby Mono came after Dolby Stereo. I have no bad feelings about Dolby making money off license fees. What he did for the recording industry in the 70's and 80's with his noise reduction schemes puts him well ahead of dozens of others that are collecting royalties for someone else's work. The NPR article did mention that along with Bose, Dolby is one of the most recognized names in the entertainment industry.

Would it be safe? Call HK.




 

Gold Member
Username: John_a

Post Number: 2387
Registered: Dec-03
Anonymous,

As for me, I would try it. Volume right down at first. Turn it up slowly. See if anything begins to sound bad, or get too hot. The A speaker channels are driving normal speakers. With Hafler connection, the B speaker channels are driving much higher impedence than normal; that is OK. There is nothing between the + and - on each channel. It is almost like having no speakers connected. That has to be OK. However, it is your gear, and your decision. If you call HK, will you get through to anyone who knows?
 

Anonymous
 
I am not sure but i will see. John, the Hafler connections raise the impedance seen by the amp on speaker B which would decrease the load on it. The rear speakers are slightly less sensitive then the fronts so im thinking this would almost act like the connections u proposed.
If i just went with wiring both pairs of speakers in normally to a and b and played at the same time would this be viable as all speakers are 8 ohm and the receiver is 4 ohm capable?

 

Unregistered guest
Hmm! The QuadraphonicQuad website confirms this Hafler cicuit so...I think one could get good effect w/ 1 speaker connected in series across the left and right positive amp outputs. Varying the speaker used to match the ohm loads of the fronts i.e. a 16ohm rear w/2 8ohm fronts would control the volume difference. Hmm!
 

Gold Member
Username: John_a

Post Number: 2388
Registered: Dec-03
Anon,

That is back to your original question, and I think the answer is "Relax; try it". The amp is designed to drive two sets of speakers simultaneously.

Anon and dennisnate

About the Halfer connection, if you give it a try, let us know how you get on.

Also, which one. I think I will one day try the four-speaker system as in my post "Thursday, October 28, 2004 - 10:10 pm".
 

Anonymous
 
Thanks for the opinions on this matter guys. I will try these different connections and see what suits me best.
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