Using low impedance speakers for surround speakers only - likely to burn my village down?


Standard Member
Hi all,
I'm aware that using low impedance speakers places a higher load on the amp which can overheat it. My question is if i'm using within spec speakers for the fronts and sub, can I get away with using lower than spec impedance speakers for the rears only?

This is for a budget system in the basement. I have an old Onkyo receiver (s3400 I think), rated for 6-8ohm speakers at 100W. But I only have the front speakers and sub that came with it, that are 6ohms. I have some spare old speakers from an ancient Sony DAV-c990 system, that are rated 3ohms. If i use these speakers for rears only, and don't try and blast the roof off with volume, what're the chances of wrecking the amp?

Obviously what I should do is buy some in-spec rear speakers (or a whole new system), but cash is tight right now. The system sounds much better as 5.1 even with these old sony speakers, than it does as 3.1 if I don't use them.

The surround speakers are restricted range, with a 180Hz crossover set on the amp, so they are not trying to put out loads of bass (they only have 2 inch cones on them), and it seems bass signals through low impedance speakers are the most demanding, not midrange/treble.

What say you all?



Distinguished Member
I highly doubt it would fry anything with normal volumes and Onkyo would likely go in to protection mode first.

You can basically buy any 6-8ohm (nominal impedance) speakers used from ebay or gumtree for pocket money if you are too afraid to use the Sonys.


Each channel in your onkyo runs on a separate amp. Each of those amps is 6-8 ohm stable. Your 3 ohm speakers are going to put an increased load on your Onkyo. However, Onkyos typically have an internal circuit breaker so if it's too much it'll over heat and shut down. It shouldn't fry anything. The situation improves a lot if you cross the rear channels over like at 80 or 100 and do not run them full range. Many speakers have a nominal impedance and the lower frequencies often drive the impedance down. The higher frequencies also take less power, generate less heat, etc.

I'd hook them up, cross them over at 80 or 100 or such and test.


Standard Member
Thanks both, that sounds reasssuring. The sonys aren't really that great but they are nice and unobtrusive in the living room, and i've certainly had my money's worth out of the onkyo, so i'm giving it a go and working well so far. Certainly not noticing any extra heat from the amp.
Appreciate the help!

(edit - and wow, my signature is about 15 years out of date - time flies!)

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