A theoretically ideal power amp would double its power every time the load impedance halves.
There are power amps on the market that either claim this or come close to claiming it.
IME, these amps are the results of specsmanship, not technology.
Here's a real world data point for the controversy about power amps needing to be able to put out twice the power for half the impedance:
I ran some bench tests on what may be one of the most overbuilt power amps in the history of audio - the Threshold SA/4e from the early 1990s.
No visible effort was spared to build a robust power amp, as this article shows:
http://www.thresholdlovers.com/artic...?lng=en&pg=394
The Threshold SA/4e weighs about 120 pounds, according to my calibrated biceps. You really want two people to tote it around, and it facilitates this by having two comfortable handles on each end.
In contrast, in similar tests a Behringer A500 which weighs about 15 pounds puts out about the same amount of power at clipping at 8 ohms, but puts out about 144 watts at both 4 and 2 ohms. This is what I would expect from a typical contemporary mainstream amplifier.
Among other features, the Threshold SA/4e amplifier has extremely soft clipping. In the end I decided to measure its output power at about 0.1% THD @ 1KHz.
The actual measured power is as listed here:
http://cgi.audiogon.com/cgi-bin/auc....82027&auc&3&4&
Namely 112 Watts per channel @ 8 ohms with both channels driven @ 1000 hz, 196 Watts @ 4 ohms, 264 Watts @ 2 ohms.
This is still very far from doubling power as load impedance halves, particularly at 2 ohms.
The emotiva XPA-2 is not expensive and they claim doubles at 4 ohms but there is no spec for 2 ohms.
But, that's not what their own test reports show. They show just over 200 wpc into 8 ohms and 300 wpc into 4 ohms.
Their spec sheet claims 300 watts into 8 ohms and 550 into 4. Close but no cigar on that power doubling claim. They use what I consider to be a bogus means of rating it - power at 1% THD. IMO, power amps should be rated by power at clipping, not power so deep into clipping.
By the same standards that I consider the A500 to be a 100 wpc amp, the XPA-2 is a 200 wpc amp. You can buy 4 A500s for the price of one XPA-2.
As a rule, you should get more watts per buck as the power goes up. Economises of scale and all that.
There's only a 3 dB difference in power, which you'd be hard put to actually hear unless you do a very close comparison.
There are power amps on the market that either claim this or come close to claiming it.
IME, these amps are the results of specsmanship, not technology.
Here's a real world data point for the controversy about power amps needing to be able to put out twice the power for half the impedance:
I ran some bench tests on what may be one of the most overbuilt power amps in the history of audio - the Threshold SA/4e from the early 1990s.
No visible effort was spared to build a robust power amp, as this article shows:
http://www.thresholdlovers.com/artic...?lng=en&pg=394
The Threshold SA/4e weighs about 120 pounds, according to my calibrated biceps. You really want two people to tote it around, and it facilitates this by having two comfortable handles on each end.
In contrast, in similar tests a Behringer A500 which weighs about 15 pounds puts out about the same amount of power at clipping at 8 ohms, but puts out about 144 watts at both 4 and 2 ohms. This is what I would expect from a typical contemporary mainstream amplifier.
Among other features, the Threshold SA/4e amplifier has extremely soft clipping. In the end I decided to measure its output power at about 0.1% THD @ 1KHz.
The actual measured power is as listed here:
http://cgi.audiogon.com/cgi-bin/auc....82027&auc&3&4&
Namely 112 Watts per channel @ 8 ohms with both channels driven @ 1000 hz, 196 Watts @ 4 ohms, 264 Watts @ 2 ohms.
This is still very far from doubling power as load impedance halves, particularly at 2 ohms.
The emotiva XPA-2 is not expensive and they claim doubles at 4 ohms but there is no spec for 2 ohms.
But, that's not what their own test reports show. They show just over 200 wpc into 8 ohms and 300 wpc into 4 ohms.
Their spec sheet claims 300 watts into 8 ohms and 550 into 4. Close but no cigar on that power doubling claim. They use what I consider to be a bogus means of rating it - power at 1% THD. IMO, power amps should be rated by power at clipping, not power so deep into clipping.
By the same standards that I consider the A500 to be a 100 wpc amp, the XPA-2 is a 200 wpc amp. You can buy 4 A500s for the price of one XPA-2.
As a rule, you should get more watts per buck as the power goes up. Economises of scale and all that.
There's only a 3 dB difference in power, which you'd be hard put to actually hear unless you do a very close comparison.