Question regarding speaker impedance

TheSVD

Standard Member
right, i've been scouring the web for a clear answer but i can't seem to find one...

Basically, i have an AV receiver which outputs 110w per channel at 6-16 ohms.
I have some older speakers i would like to use with it which are rated at 4-8 ohms.

Now, what i would like to know is whether i can safely use these speakers with my system, because i have heard mismatched speaker impedances can cause damage to the equipment.

However, i have heard that is only if you were to use 4 ohms on a 6-16ohm setup, but because the speakers do 4-8, surely they would work on 6-16 safely?

Ah i dunno, i really do have no idea, any help would be much appreciated :)
Cause i dont wanna fry my brand new surround sound :D
 

BlueWizard

Distinguished Member
How about telling us specifically what the Amp and Speaker are; brand and model.

Though I don't know about your speakers specifically, generally when speaker are rated like this, it means the impedance dips down at one specific frequency to something close to 4 ohms. Why that happens varies from speaker to speaker.

I think as long as you only put one speaker on each amp channel, you are likely to be OK. But again, I don't know what the speakers are so I can't speculate why they would drop to 4 ohms.

If the speakers have a second woofer, there by creating a 2.5-way speakers system, then across the range from the lowest frequency up to the crossover of the second woofer, both woofers are playing resulting in a solid 4 ohm load. So, between, say, 30hz and 300hz, you could have two woofers per speaker playing. Once the second woofer drops out, you just have a normal 8 speaker.

That is a very different load, than say a Mordaunt Short with a single woofer. In the case of a single woofer, then likely due to cabinet and speaker tuning, there is only one specific frequency at which the impedance drops low. That is a much easier load to drive because the low impedance probably doesn't span more than 20hz to 30hz.

So, specifically, what amp and what speakers are we talking about.

Steve/bluewizard
 

TheSVD

Standard Member
whoa, very detailed response :eek:
thankyou very much for your help, but an audiophile friend of mine already helped me out here. Turns out they dont sound so great anyway :facepalm:
now this might sound like a real noob question, but i do have some other speakers which are rated at 6 ohms (these are speakers from a phillips fwc399 hifi system) but are 120w, rather than the amps (sony ht-ddwg800) 110w output. i assume this will be fine? one person has said the speakers will try to draw too much power from the amp? :confused: wasnt sure about that aha.
Help appreciated on my last question by the way :)
 

BlueWizard

Distinguished Member
Think of speaker power as being analogous to the speed limit on the roads.

You can drive your car at any speed up to the legal speed limit. Anything in that range is fine. The same is true of speakers, you can feed them any amount of power from none up to their limit.

And, as we all know, there is nothing to stop you from driving faster than the speed limit. You are only limited by your good judgment and your skill, combined with the proximity of law enforcement.

The same it true of speakers, you can drive them beyond the stated limit as long as you exercise reasonable caution, care, and common sense.

The difference between 110w and 120w is virtually nothing. For practical purposes you can consider them the same.

What makes a speaker difficult to drive is the impedance. The lower the impedance goes, the more current it demands from an amp. Amps can easily supply voltage, but delivering current cause all the heat and potential damage. Supplying electrical current to a speaker is hard when the impedance is low.

But for most amps, as long as you stay in the rated range of the amp, whether 4 ohms to 16 ohms or 6 ohms to 16 ohms, you should be fine.

The power rating on a speaker does not indicate how much power the speaker draws. It indicates the maximum limit of sustained power before heat builds up to a dangerous level in the speaker.

But also keep in mind that a speaker can sustain short term peaks in power well above the rated continuous power. So, you have to be trying pretty hard to damage a speaker.

Steve/bluewizard
 

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