Comments on powering 4 ohm speakers with an 8/6 ohm amp? (1 Viewer)

[Troy LaMont]

Looking at getting some new speakers and I'm not sure if the above posed question will be a problem with a regular amp.

Can most amps power 4 ohm speakers?

Thanks.

Troy

 

[Bob-N]

I would think that the amp wouldn't care what the ohmage is for the most part unless you exceed the maximum power it can provide. In a typical situation, the 4 ohm speaker will demand more power (twice) vs. an 8 ohm speaker. Quite a few amp manufacturers spec power consumption at various loads (8/6/4 ohms) so make sure you check the specs or contact the amp manufacturer before you buy.

 

[Troy LaMont]

In a typical situation, the 4 ohm speaker will demand more power (twice) vs. an 8 ohm speaker.

Just what I was looking for.
So I would assume that would also mean that my present amps power rating would be almost halved?
Thanks a bunch Bob!
Troy

 

[Gordon C Jr]

I'd be very careful with this... Running a 4 Ohm speaker on a amp rated for 8 Ohm speakers will demand twice the load as stated above. This could be very hard on the amplifier at higher volumes and you may run into problems with the amplifier overheating or clipping.

I believe a 4 ohm speaker is rated on an average resistance and the load could go down to 1 or 2 ohms at times, which could really stretch the amplifier capabilities.

Unless you plan to upgrade your amp sometime in the near future, I would avoid 4 ohm speakers for these reasons.

my 2 cents

 

[Clinton McClure]

I must concur with Gordon. If the amp is rated for 6 or 8 ohms, it would be best to use 8 ohm speakers. The power consumption of the 4 ohm speakers (especially during resistance spikes where impedance drops to 1 or 2 ohms) may stretch your amp to its limits and cause thermal shutdown or premature wear & tear on the internal workings of the amp itself.

 

[Kerry Hackney]

Troy,

In general, I agree that you should use the amp with some caution. However, a lot depends on which 4 ohm speaker you use and how loud you intend to play it. Also, is this just for stereo listening or is it a surround receiver/amp? Some speakers have larger impedence dips than others.. for instance, I once owned some Infinity speakers with the EMIT tweeters which were very difficult to drive. They would really dip down as far as 2 ohms. Even though they were rated as 8... My current speakers are 4 Ohm but the cheap Sony receiver I had drove them just fine in stereo mode. I only had heating problems in surround modes. My advice is try it in the beginning at low volumes. Monitor the amp/receiver by laying your hand on it and see if it is getting past warm. That will give you some idea of how far you can push it. If your volume requirments aren't too high you may be able to get by for some time with what you have. Eventually, I'll bet you want to upgrade but this could buy you the time you need.

 

[Bob-N]

Hmmm, it's hard to explain. What's really happening is that the 4 ohm speaker is requiring roughly twice the power that the 8 ohm speaker requires. So if the amp is rated for 100W at 8 ohms, in theory, the amp will only be able to supply about 50W into a 4 ohm speaker. Does that make sense?

Clinton and Gordon have valid points also. When you're talking ohmage for a speaker, it's an average. You have to take a look at the minimum ohmage (or resistance or impedence). Unfortunately, ohmage is not static and changes as frequency changes. So be careful as the other posters have noted. You might blow your amp if it's not rated for 4 ohm speakers.

 

[Troy LaMont]

Well,
Looks like I'll also be updating my amp(s) with the speakers (not that there's anything wrong with that! )
So does anyone know of any companies that manufacture 4 ohm amps (other than car audio)?
Thanks again.
Troy

 

[Troy LaMont]

I think I may already have an amp idea...

I'm spending way too much money lately!
Troy

 

[Bob-N]

How much do you want to spend? Krell, Rotel, B&K, Outlaw would be amps I would recommend and come recommended by members. There are many others (others chime in!) but those companys are the ones I'm familiar with. They all have high power amps and I'm pretty sure they have specs for 4 and 8 ohm loads. Most of the mid to hi-fi companies do spec for multiple load conditions from what I've seen.

I personally have a Rotel RB985mkII 5ch amp which is an older amp (last one built sometime in '98) and provides 110w/ch. I listened to it's newer brother, RMB1075 (coupled to a Rotel DVD player, RSX972, B&W 602 S2s) and liked the sound. I'm hoping it will couple well with the Outlaw 950. That's the last piece of my HT puzzle.