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Matching Power and Speakers -- Much Ado about Not-that-Much? (Tube amps and speakers)

Interesting conversation at the Part Time Audiophile's The Occasional Podcast.
There, tube amp maker Justin Weber of Amps And Sound makes these comments:

At about 24:03 in, they have an interesting conversation about power in tube amps and speakers' needs.

Justin makes an interesting comment about power and speaker efficiency. He's careful to caveat that room size might be an important differentiating factor, but for many (most?) audiophiles (with small-medium size rooms), there is just not that much to worry about regarding amplifier power and speaker matching. He is not touching on "synergy" in some larger sense -- he's just addressing the "power needed to drive speakers" question.

If I'm understanding the upshot of what he's saying, it's that lower-power tube amps made with quality transformers (and well made generally) have a very good shot at doing an excellent job for a much wider range of speakers than is typically assumed in conversations audiophiles have.

The whole interview is interesting, but here's the interesting bit -- I did my best to transcribe it, but go listen for yourself!

"Almost always, you need vastly less power than you realize....I've seen 1 watt power whole rooms and big rooms with moderately efficient speakers....What's a practical standard? 30 watts should do 99% of everything for everyone, and 15 watts should do 95% of everything for 99.9% of everyone....

Most audiophiles have small listening rooms.... [A more powerful tube amp may sound better, but] I think that’s a matter of it having a better output transformer and [that] output's transformer's core actually having a flatter frequency response and going lower.

So [in those cases where a more powerful amplifier is used] I don't know that it's a question of producing more power -- that you need more power -- as much as the transformer [in] the more powerful amplifier is [instead just] a better transformer."

Not sure what folks here think about these claims. Perhaps they seem so obvious as to almost not need repeating. But there are so many conversations about speaker sensitivity and watts that do not mention the quality of the transformers or which seem to overstate the importance of how powerful an amp is.

If Justin is right, then many, many pieces of advice related to "how many watts do you need" are basically wrong.

 

SOURCE: 
5 Things To Consider When Buying A Tube Amplifier
March 13, 2023 Brian Hunter Occasional Podcast 1
URL: https://parttimeaudiophile.com/2023/03/13/5-things-to-consider-when-buying-a-tube-amplifier/

hilde45

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
12,099 posts
 

There’s also cases of speakers rated for 4 ohms which are 2 ohm speakers and they don’t need power so much as current. You tend to get higher current with bigger amps (not universally true).

@erik_squires

Uh, just so we’re clear: current cannot exist without voltage; when voltage and current are present there is power.

1 Watt equals 1 Volt divided by 1 Amp. That’s the Power formula and its inescapable.

The art of music reproduction in the home lies somewhere in between. I have to wonder if you or Ralph love music because if you really do, you would know that the reproduction of music is not subject to pure measurement.

@fsonicsmith1

The disconnect between sound and measurement used to be quite real. But in the last 30 years the technology has become available which makes your conclusion above false.

What has lagged behind the technology though is our understanding of how the ear/brain system perceives sound. As a result, even though we can make the measurements, most people including those that make the measurements don’t really know what is important about them or how to interpret them so you can predict how the circuit will sound. I spend some time over on ASR and I see this a lot over there.

I also see that both the measurement and subjectivist camps are equally guilty of confirmation bias.

As you point out, the sound is everything- its the proof of the pudding. Personally I fall into a middle ground category which is unpopular with both the measurement crowd and the subjectivist-listen-only-to-your-ears crowd. Daniel von Recklinghausen of HH Scott fame first stated my position:

If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you’ve measured the wrong thing.

atmasphere's avatar
atmasphere
12,099 posts
 

If I'm understanding the upshot of what he's saying, it's that lower-power tube amps made with quality transformers (and well made generally) have a very good shot at doing an excellent job for a much wider range of speakers than is typically assumed in conversations audiophiles have.

The issue is deciBels. The ear hears on a logarithmic curve; deciBels are a logarithmic unit of volume. 3dB is barely perceptible to the ear in terms of volume increase but requires double the amplifier power. So the difference between 30 Watts and 300 Watts is only a doubling in the perceived sound pressure.

This is why if you need more than 100 Watts to make your speakers work, you'll probably need 600-800 Watts or more to get the sound pressure you're looking for without clipping the amp. If you need more power than that the speaker is really impractical or your room is really large.

OTOH we have SETs which are a unique phenomena. Because they use no feedback (and so are 10% distortion before clipping), if you want to get the most out of them, your speaker has to be so efficient that the amp is never asked to do more than about 20-25% of full power. At power levels above that the amp will make more higher ordered harmonics on transients, causing the amp to sound 'dynamic', since the ear uses those harmonic to sense sound pressure.

That makes SETs impractical on most loudspeakers and is why horns made a comeback in the 1990s. SET users get by with so little power because the amp can sound 'loud' when pushed, so the user tends to think its plenty of power. When using a cleaner amplifier the volume tends to go up... but if such a user goes from a 7 Watt SET to a 30 Watt PP amplifier, they may find themselves running the 30 Watt amp out of gas because they are trying to get the same 'loudness' as they got before, if they don't understand that the perception of 'loudness' was caused by distortion.

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