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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/

128x128hilde45
8th-note
408 posts
 

Mr. Weber is ignoring a significant swath of high end speakers that have low sensitivity and a difficult impedance curve. Wilsons and Thiels are two prime examples. In the more extreme cases the speakers also have phase issues which makes them even more difficult to drive. Anyone who reads Stereophile and pays attention to the sensitivity, impedance, and phase measurements is aware that many speakers require a robust amplifier to operate at their best.

In my case I have a pair of Thiel CS6 speakers driven by a Krell KSA 300S (2400 watts into 1 ohm) and it takes everything that amp can produce to drive my speakers to concert levels. Because of the punishing impedance curve (around 2 ohms for part of the audio band) a tube amp will act as an unintended tone control on these speakers.

It's interesting that high end speaker companies are still designing speakers that have low sensitivity and a low, variable, impedance curve. This apparently is a tradeoff that some speaker designers are willing to make to get the sound they are after. These speakers need a solid state amplifier that can double it's output as the impedance drops by half.

Mr. Weber designs tube amps that cannot run speakers like mine. Sure, they will sort of work but they will sound anemic and the frequency response of the speakers will not resemble what the designer intended. His statements are uninformed and obviously intended for people with little experience in matching amplifiers and speakers. As this subject comes up over and over again I am disappointed that people like Weber, who should know better, espouse this drivel.

hilde45's avatar
hilde45 OP
4,974 posts
 

@8th- note I suggest you listen to a bit more of the interview before judging him so harshly.

erik_squires
16,057 posts
 

I do think audiophiles are taught to chase big amps far too much and you can get amazing results with some sweet small amps and a half-decent speaker.

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).

I’m thinking of models from older Legacy and the KEF Reference1 which I’ve recently seen measurements for and going "wow."  The current requirements of those speakers is just far above what a lightweight amp which otherwise would sound fabulous.

Take a CJ Classic 60.  Pair it with a Fritz speaker and it's going to sound fabulous.

fsonicsmith1
101 posts
 

@8th-note 

I am sorry but you are beyond harsh, you are just extreme. Extremism is to be avoided 99% of the time. 

Frankly, Mr. Karsten borders on the same end of the spectrum but at this point I believe he is just too hell-bent on the scientific approach. It amazes me that he ever built tube amps. 

The art of medicine needs strict adherence to the scientific approach because there is no room for subjectivism. Art itself, visual, musical, or in letter form is not subject to the scientific approach. 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. If it make you feel any better, I think the same of John Atkinson and Kal Rubinson. 

Do you know the only thing worse than old men with fixed sets of belief and value systems? The answer is old ENGINEERS with fixed belief-systems. 

atmasphere's avatar
atmasphere
11,800 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.

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