SKareKrow

or does it have to do with effiency?

Alf Garnett

Presenting a 2 ohm load to an amp will make the amp try to double its output power...at a trade off of extra heat and reduced sound quality...Normally done with subwoofers so the loss in quality is lessened...

4 ohms is the point @ which most amps are advertised for power delivery, becareful which amp you present a low impedance load to...some will just shut down...Quality gear won't have a problem...

Marcus

HDClown

Amps that are designed for low ohm loads are not going to generate any extra heat than they are designed for, nor will they sacrifice sound quality.

An amp NOT designed for a low ohm load and you then place a low ohm load on is another story. That will do exactly what you indicated.

Most amps have a standard 4 ohm rating on stereo channels, and even bridged mono, however, many amps are 2ohm stable these days, and monoblocks are stable to 1ohms, and Orion and Soundstream (and other I'm sure) offer amps stable to like .5 ohms.

Now back to the original question, how does it effect sound quality? I think there's some RTA data to show a 4ohm setup is more accurate on the graph, but when it comes to human ears, I don't believe there is any noticeable differences what so ever.

SKareKrow

Thanks for the info..

RobC

For a given amp, if you decrease the load from 4 to 2 ohms, the amp will run hotter because it is supplying more current (I=V/R). However HDClown is correct in that certain amps are designed to operate at lower impedances (by using lower voltage rails) and will play cleanly at these low impedances.

I can think of only one reason for an amplifier that can drive low impedances: car stereo competition. They typically rate your amplifier power based on its 4 ohm power rating (atleast back in the days when I was still into the stuff). That way your "50 watt" amp could compete in the 50 watt class, but was actually delivering 400 watts because you had the amp loaded down to 1/2 ohm. Some may argue that high current amps let you use multiple woofers. However you can get around that by using a series-parallel combination, so I don't buy that reason.

As far as sound quality goes, you really can't generalize and say that 4 ohms sounds better than 2. However most "non-subwoofers" (midbass/midrange/tweeters) are going to be 4 ohms, and if you use these with your high current amp, you won't be getting your money's worth when it comes to watts/$. ie, that 400W high current amp is only putting out 25 watts/ch because you're running it at 4 ohms.

What I typically do is find an amp that has a good 4 ohm power rating and use it to drive my highs. For bass I typically will find something that will drive low impedances because current is what you need for subs. I'm personally using an ADS amp for my highs (8-ch version) and Precision Power for bass.

FROMA42TT

They have an impedance leveling main board. For instance, the 500 watt mono amp, wired in any number of different ways, will continue to run at 4 ohms. Advantage: Hook up as many speakers as you like, experience even distribution of power instead of overworking the amp, especially with dual voice coil sub-woofers. Buy the power you need, high current amps sacrifice sound quality at higher volume. -Ex-Pheonix Gold High Current Amp Junky!