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Impedance Differences and Mixing Speakers and Amplifier Impedance Rating

post #1 of 5
Thread Starter 
I am very very confused. I would appreciate your opinion and advice. Thanks in advance.

Is this a correct statement? That you can't mix 4 ohm and 6 ohm or 8 ohm speakers working on a receiver?
As stated in my question to Onkyo,
My Front and Surround speakers are 6 ohms.
My Center speakers is 12 ohms.
My Rear Surrounds are 8 ohms.

How about their statement that;
-- The TX-SR608 model receiver (which is rated to work with 6 ohm speakers) can only work with speakers that have a minimum impedance of 6 ohms or higher.

It is my understanding that a speaker with a listed impedance of 6 ohms is in all cases the NOMINIAL impedance of that speaker and that some frequencies will, by definition, be below 6 ohms and that some frequencies will be above 6 ohms.
In that case no amplifier rated for 6 ohm speakers would work with speakers of 6 ohms!!!

This is my answer from Onkyo Customer Support:
Thank You for contacting Onkyo USA Product Support.
We apologize for the delay in responding to your email. We are experiencing a heavy volume of inquiries. *We appreciate your patience and understanding.
Larry,
The TX-SR608 model receiver can only work with speakers that have a minimum impedance of 6 ohms or higher. *So your speakers must be 6 ohms or higher. *The TX-SR707 can work with speakers that have a minimum impedance of 4 ohms. *But all your speakers must be 4 ohms in order for this to work. *You can not have 4 ohm and 6 ohm or 8 ohm speakers working on a receiver.
Bob E

This is my question to Onkyo Customer Support:
Comments: Hi, I am thinking of purchasing an Onkyo Receiver and I would like your advice on whether your Model TX-SR707 and Model TX-SR608 will drive my speakers. My primary speakers are HSU speakers as follows: Powered Sub-woofer; VTF-2 MK3 Left Front; HB-1 (Spec's say Nominal impedance 6 ohms, Minimum impedance 4 ohms) Right Front; HB-1 (Spec's say Nominal impedance 6 ohms, Minimum impedance 4 ohms) Left Surround; HB-1 (Spec's say Nominal impedance 6 ohms, Minimum impedance 4 ohms) Right Surround; HB-1 (Spec's say Nominal impedance 6 ohms, Minimum impedance 4 ohms) Center; HC-1 (Spec's say Nominal impedance 12 ohms, no Minimum given) The Rear Surround Speakers are Cerwin-Vega Speakers Rear Left Surround; L7 (8 ohms printed on back of speaker) Rear Right Surround; L7 (8 ohms printed on back of speaker ) Will these speakers be acceptable in this configuration to work with the Model TX-SR707 and Model TX-SR608. If not which of your other AV Receivers will work? Thanks, Larry Smith VISITOR INFORMATION:HTTP REFERRER:http://www.us.onkyo.com/feedback_form.cfm?cat=Receiver
SERVER: 251
post #2 of 5
Most speakers dip below 6 ohms. If the nominal impedance is 6 or higher you should be fine. I wouldn't worry about it too much. How would anyone know if their speaker DOESN'T dip below 6 ohms?

I have never heard of "You cannot mix different impedance speakers". The nominal impedance is a guide. If you took 3 speakers from the same line and tested their impedance curve they would all be different. Imagine how different different brands could be! You could have an 8 ohm speaker that is more demanding than a 6 ohm. It may be one very small frequency, but the 8 ohm could dip lower.

I currently have 4 ohm front speakers matched with 8 ohm speakers to fill out a 5.0 system. My Onkyo 805 can handle 4 ohm, and I have never had an issue with my surround setup.

I would bet many others will chime in. Sounds like the Onkyo customer support doesn't really know what they are talking about.
post #3 of 5
Some receivers adjust the rails/current limits/whatever to drive lower-impedance speakers. I have not heard, and find it hard to imagine, that you would hurt anything if you mix and match. Might have a little lower power if you have to set everything to 4 or 6 ohms. Of the four (!) AVRs I have in the house, I think only one requires me to actually tell it if I have high/low impedance speakers; the rest just deal with whatever is attached on the speaker terminals without problems.

FWIWFM - Don
post #4 of 5
Basically, don't worry about it. If you really look at impedance curves, they go all over the place, and the one number given usually doesn't mean much of anything. Other than some hellacious drivers like bare ribbons and some electrostats, most consumer speakers are benign loads. There's ignorant bliss, there's knowledgeable bliss, and then there's partial-picture hell...
post #5 of 5
Thread Starter 
Quote:
Originally Posted by tlag View Post

Basically, don't worry about it. If you really look at impedance curves, they go all over the place, and the one number given usually doesn't mean much of anything. Other than some hellacious drivers like bare ribbons and some electrostats, most consumer speakers are benign loads. There's ignorant bliss, there's knowledgeable bliss, and then there's partial-picture hell...

I Just purchased the Onkyo TX-NR808 AV Receiver and think it will solve the problem. Thinking the speakers just pulled to much from the old Amp. So, the much higher output from the new one should fix it. It is THX Rated for 4 ohm speakers as well.
Another plus is all the latest features of the NR808!!
Thanks loads for all the inputs. It really helped.
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