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Is it okay to run 4ohm speakers off a 6ohm Amplifier?

N

nobb

Senior member
I have some really nice sounding speakers which are 4ohm, and they are currently being run off an amplifier rated for 6ohm. The amplifier gets fairly hot, so I installed some cooling fans. The amplifier is very cool now. In fact, the amp running at high volumes with a 4ohm speaker is even cooler than when I tried to power some 6ohm speakers at moderate volume. The hottest part is the transformer, but even that feels warm to the touch (touching the backplate which is connected to the transformer).

The system has been running like this just fine for over a year. But I am wondering if maybe there is a chance I am doing damage to the system this way? Everything is cool, so there should be no problem right?
 
No problem as long as you're not turning the amp up as far as it goes and exceeding the current capability of the transistors. If it's still working fine, you're not damaging it. Though any good amp will have protection anyway.
 
Not knowing what amp you are referring to, there are many things that can cause an amplifier to be 'allowed' to be called 'high current' which means it can handle low impedences. While keeping the amplifier cool is one thing, another is the actual components within the amp. They may or may not be appropriate to run high currents. If you have no problems over the course of a year, I would just keep going with it.

But, do realize that technically, what you are doing is not recommended usually. 4ohm speakers demand high current, and if the amplifier is not spec'd do deliver that high current, you could run the amplifier into clipping which could damage your speakers. If you listen at moderate levels, you may never have a problem. Most likely, the issue would come when you are, for example, watching a movie and there is an explosion on screen where the current demands of your speakers spike and your amplifier (could) smokes.
 
You'll only do damage if you play it too loud. If it sounds distorted in any way or less dynamic then turn it down.
 
4 ohm will demand more current than 6 ohm, but how much current it draws is a function of how much voltage you give it, Tiamat. If you are current limited at 6 ohms then you're only going to be able to pull 4/6 the amount of power using P=I^2*R. But as long as the amp is not set up to monitor impedance (as opposed to just detecting over-current) and as long as you don't pull more current than it can supply (assuming the protection doesn't trip), you're fine. And I'm sure the cooling helps anyway.
 
Originally posted by: dandragonrage
4 ohm will demand more current than 6 ohm, but how much current it draws is a function of how much voltage you give it, Tiamat. If you are current limited at 6 ohms then you're only going to be able to pull 4/6 the amount of power using P=I^2*R. But as long as the amp is not set up to monitor impedance (as opposed to just detecting over-current) and as long as you don't pull more current than it can supply (assuming the protection doesn't trip), you're fine. And I'm sure the cooling helps anyway.
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Right, as I as saying, except Impedence is a function of frequency unlike resistance. unless you know what the impedence profile is of the speaker plotted against frequency, we dont know what the actual demands of the speakers will be. 8ohm speakers commonly dip down into the 4ohm range (frequencies at which they would demand more current) for example. There are many 4 ohm speakers that are less reactive, easier to drive than 8 ohm speakers. But, we don't know that information, but that info. may be purely academic compared to the recommended practice of just listening to the speakers and when you hear something odd, just turn it down.

At the worst, your receiver shuts down when the speakers demand more current than it can offer (assuming your receiver has this safety feature). Typically you will get distortion as a warning sign and you just need to lower the volume.

At the best, your receiver doesn't mind the load from your 4ohm speakers, and you never have any problems.
 
At the worst, your receiver shuts down when the speakers demand more current than it can offer (assuming your receiver has this safety feature). Typically you will get distortion as a warning sign and you just need to lower the volume.

At the best, your receiver doesn't mind the load from your 4ohm speakers, and you never have any problems.
Click to expand...

QFT.
 
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