Does amplifier wpc @ 4 or 2 ohm really matter at "low" volumes?
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damacman
Resident Psycho
A "100 Watt" amp that makes 200 Watts when impedance is halved doesn't really make 100 Watts - rather, it's under rated. While we can apply Ohm's Law on paper and achieve that, losses in the real world prevent it.
As for the original question, I've never seen any definitive proof to support that a bigger amp can sound better than a smaller one at low levels. I've tried it over and over again ...
As for the original question, I've never seen any definitive proof to support that a bigger amp can sound better than a smaller one at low levels. I've tried it over and over again ...
The ‘doubling power as impedance is halved’ thing is more important if you like to listen loud using speakers with impedance curves that dip very low (for example some early TOTL Infinity, and Apogees, and possibly Thiel IIRC). But IME these use cases are outliers, and most speakers (assuming you’re just using one pair, not two pairs in parallel) are not going to tax the amplifier in that way.
The thing is that some reviewers used speakers that demanded this ability, so panned amps that couldn’t. And some of those amps being reviewed outright failed when asked to do so. But for most people it’s really not that important, especially if listening at lower levels. My MacCormack DNA 1.0 does this but I never ever listen anywhere loud enough to make it a real benefit, to be honest.
The thing is that some reviewers used speakers that demanded this ability, so panned amps that couldn’t. And some of those amps being reviewed outright failed when asked to do so. But for most people it’s really not that important, especially if listening at lower levels. My MacCormack DNA 1.0 does this but I never ever listen anywhere loud enough to make it a real benefit, to be honest.
BilboBaggins
Addicted Member
The other example is with output transformers such as you would see in vintage McIntosh. An example would be the MC2205. 200 watts into 8 ohms and 4 ohms. Do they sound the same? I don’t know. How do you compare two different speakers into the same amp, but my inclination would be to say no.
I’ve actually done a lot of real life experimentation on this topic, as it seems I prefer 4 ohm speakers to 8 ohm speakers.
My conclusion is, no. Even at 1 watt output. Why? In my thoughts, it is because the 4 ohm amp can handle the transients better. Bass is fuller and highs are smoother. I did do an experiment with my Klipsch Cornwalls where I first used the MC2205, and then I used my MA6200. The MC2205 sounded much better than the MA6200 even at very low output. And even though I wasn’t even close to the rated output of the MA6200.
savatage1973
Addicted Member
And to expand upon this, most speakers that have known low-impedance dips, tend to have them in "critical" areas of the frequency response curve. My Kappa 9's dip below 1 ohm at both 32-35 Hz and 7 KHz--two areas where there is a lot of music--places where there is going to be a lot of demand on the amp.
Throughout its history through the present day, the majority of Mc amplifiers are O/T design.
savatage1973
Addicted Member
Actually, it was in the late 70's and early to mid 80's with the "new Class A" amps that would operate in pure Class A mode for a substantial portion of the lower wattage range, and then move to Class A/B for full output operation. I know some Yamahas had "defeat" switches to hold/limit the amps to pure Class A operation, and not go out of that range.
45rpmspinner
Super Member
Interesting discussion.
And while perhaps a bit over my head, I have been thinking about this subject a good bit.
Hypothetically speaking [although I can provide a real-world example], wouldn't an amp capable of doubling output into 4ohms, and at least in bridged mode be capable of doubling again into 2ohms possibly sound more dynamic under some speaker loads than say an amp of vaguely similar output at 8ohms which is only capable of increasing output by only 40% into 4 ohms?
This is of course only if the power supply is sufficient.
And while perhaps a bit over my head, I have been thinking about this subject a good bit.
Hypothetically speaking [although I can provide a real-world example], wouldn't an amp capable of doubling output into 4ohms, and at least in bridged mode be capable of doubling again into 2ohms possibly sound more dynamic under some speaker loads than say an amp of vaguely similar output at 8ohms which is only capable of increasing output by only 40% into 4 ohms?
This is of course only if the power supply is sufficient.
The bottom line is whether a given amplifier is able to make the current & voltage being asked of it under a given set of conditions. If so, not an issue; if not, there is.
A high power, 2 ohm amplifier isn't going to perform any better than a lower powered amplifier designed for 4 - 8 ohm loads under identical 8 ohm loads - solely on the basis alone of being a higher power, higher current model - so long as neither is being overdriven.
A high power, 2 ohm amplifier isn't going to perform any better than a lower powered amplifier designed for 4 - 8 ohm loads under identical 8 ohm loads - solely on the basis alone of being a higher power, higher current model - so long as neither is being overdriven.
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mhardy6647
Lunatic Member
At low volume, or with high sensitivity loudspeakers, what matters (IMO/IME) is the performance of the amplifier at very low output power levels.
Many, perhaps most, amplifiers are not at their best at output power levels below one watt, due (perhaps) to compromises (design choices) driven by the market's perceived
obsession with high power output.
Some amplifiers do sound good at, say 50 mW output.
There's a reason Nelson Pass calls his "less commercial" venture FirstWatt.
http://www.firstwatt.com/
Many, perhaps most, amplifiers are not at their best at output power levels below one watt, due (perhaps) to compromises (design choices) driven by the market's perceived
obsession with high power output.Some amplifiers do sound good at, say 50 mW output.
There's a reason Nelson Pass calls his "less commercial" venture FirstWatt.
http://www.firstwatt.com/
BilboBaggins
Addicted Member
Completely agree with this. Well worded 62caddy! If you don’t use or intend to use power hungry speakers, then a regular 8 ohm amp is fine. But if you are like me and like to experiment with different speakers in your setup, then a high current amp is essential. I once sold my Yamaha M40 because I had just bought a nice Sansui b2101. I compared the two amps with the speakers I had at the time, and I figured the Sansui was the keeper. Then I picked up a pair of Camber 2.0 and the Sansui just couldn’t cut it! I should have kept the M40!
Now, my keeper systems are all substantial. Never a worry about whether I’m hearing the speaker at its best.
I wasn’t sure about whether McIntosh still makes amps with output transformers, so I stuck with what I knew.
45rpmspinner
Super Member
In the abstract.
In the real world, no two amps are the exactly the same, each having different output characteristics.
The presumption being that the actual speaker impedance never dips below a level where either amp is stressed more than the other.
As we all know, speaker impedance varies a great deal.
To the extent that a speaker rated at 4ohms drops to 2ohms, the ability of an amp to handle that load via current draw can only be a plus.
But my original question wasn't really about low vs high power.
It was about the ability of amps to react dynamically under certain loads....and whether in the end that translates to a more dynamic sound.
slimecity
Super Member
I dont see the point of equating an amp's specs with its sonic characteristics. You can have some designs with terrible specs, but which reviewers and other listeners completely love.
I have some high-amplifier amps. the only one I think sounds fantastic is my sansui X1.
Otherwise, I agree with Nelson's first watt principle - I love some of his designs and my fave amps are low-power, single-ended ones. I bet the specs for a SE tube amp look terrible on paper, BTW
I have some high-amplifier amps. the only one I think sounds fantastic is my sansui X1.
Otherwise, I agree with Nelson's first watt principle - I love some of his designs and my fave amps are low-power, single-ended ones. I bet the specs for a SE tube amp look terrible on paper, BTW
IME this is nothing to do with performance of trafo/rectifier but everything to do with negative feedback. Negative feedback is claimed to be "most important part of amplifier". BS I say, as it completely destroys transient behaviour making amp sound dull and boring. Thats why Wirst Watts amp (or any no-feedback SE amp with output trafos) sounds so good damn good but have terrible specs.
Of course one can argue that negative feedback can be designed correctly to have excellend sound and be powerful. Sansui is known about this and definitely Luxman.
All that matters is that the amplifier has the ability to supply the current & voltage demands for a given speaker at a given listening level - whatever it happens to be.
If all dynamic peaks in a given piece of music do not exceed a given amplifier's abilities to meet them, there is no improvement a larger amplifier is going to accomplish.
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bowtie427ss
Lunatic Member
Quoted for truth and emphasis.
Doubling down of amplifier output only occurs on paper and in the minds of the un-informed.
Krell FPB 300 for example is rated at 300, 600 and 1200 wpc respectively into 8, 4, and 2 ohm loads. Thorough testing on a competent tech's bench will show that the amp actually puts out just under 600 wpc into 8 ohms, a bit over 900 wpc into 4 ohms, and just shy of 1300wpc at 2 ohms.
There are other amplifers out there that come closer to the doubling down trick, but there are none to my knowledge that actually double their output with halving the load impedance.
bowtie427ss
Lunatic Member
It seems like the OP's question is generally about the realm of the first watt. I wonder(actually suspect) that there are amplifiers out there(in the solid state world) that need to be driven to a minimum threshold before they will meet certain specs.
Consider the FTC's standard testing procedure that requires preconditioning before testing. I believe this is done mostly to establish a working thermal benchmark, but there may be other factors at play too.
Given the OP's question and stated conditions of low level listening, isn't it quite possible that in that specific scenario there are amplifiers that would never run up to their normally assumed operating temperature, and actually run slightly out of spec under those conditions?
The Krell FPB mentioned above is a good example that when driven at low levels( a watt or less) will run all day at barely warm to the touch. Turn it up a bit causing the plateau bias to ramp up and within a few minutes the heatsink and case temperature will stabilize somewhere north of 130 degreesF.
I'm talking about the exceptions among what most of us would consider average/normal performing amplifiers.
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damacman
Resident Psycho
And to think there was also an FPB 600!
I think it's going to depend on your music taste as well.
Some amps have highly regulated power supplies. Those amps should put out more continuous power into lower impedance loads than those with less regulation. But an amp that relies primarily on a huge amount of capacitance in the power supply can probably match that performance for transient power delivery. Stack too many transient spikes too close together and those capacitors start to droop. At what point that becomes audible is going to depend on the music and the average listening level.
Some amps have highly regulated power supplies. Those amps should put out more continuous power into lower impedance loads than those with less regulation. But an amp that relies primarily on a huge amount of capacitance in the power supply can probably match that performance for transient power delivery. Stack too many transient spikes too close together and those capacitors start to droop. At what point that becomes audible is going to depend on the music and the average listening level.
savatage1973
Addicted Member
Yeah--I realize that it is all marketing BS, but in their defense, the amp will/does meet or exceed the published ratings at all impedance points.
Yes--it all looks good on paper when you do the math, but in the "real world" there are losses that occur along the way, so it is physically impossible to attain a 100% "doubling down".
Operating temperature certainly is a factor in amplifier performance. Read any service manual, and they will tell you to "warm up" the amp for XX minutes before setting bias and offset. My Krells (KMA 160 monoblocks) are pure class A, so they get hot, even at idle, but they do sound better once they warm up, than they do at cold start.