Amp Output Power and Perceived Loudness

[K Teacher]

This tread: "Leo and his 420V 6V6", now on its 5th page, got totally off track (after page 2), so it's time to start a new thread…

The assumption here, which caused the previous tread's disruption, is:

Although an increase of 3dB represents a doubling in power, an increase of about 10dB (10x more power) is required, before the sound subjectively appears to be twice as loud. The smallest change one can hear, is about 3dB. Or in other words, an average person, with everything the same (specially speaker's efficiency), can barely tell loudness difference between a 5W amp and a 10W one; and a 50W amp will be perceived to be twice as loud as a 5W amp !!

Therefore, an output power increase from 14W to 22W, with all else being the same (including the speaker), cannot be heard by an average person.

Additionally, I read somewhere, that an average person can perceive 1dB increase in loudness for a SINGLE TONE, but not for a complex signal like music.

Comments / experiences?

[Chuck H]

I don't think this is a question of plain wattage other than in a pedantic, dry and theoretical way. There have been a lot of low watt amps that couldn't cut through and a few that would. And then there's the particulars of speaker efficiency. All things are NEVER created equal. So if you have an amp rated for 15W that has a reasonably flat response overall, a speaker of unremarkable efficiency and the power supply is not up to much dynamic performance... You find it doesn't cut through the mix. But then you see a guy at the club with an amp that has the same power tube compliment and it's loud and clear!?! Well THIS amp happens to have a high mid and a little treble bump, it's making 20 watts and has a speaker with 3dB greater efficiency and it has a little more dynamic peak available because of the power supply. It all adds up. Or, in the case of amps that just don't get out, subtracts. If you take the worst scenario for a fifteen watt amp it's not enough. If you take the best scenario for a twenty watt amp it's plenty.

This as it applies to guitar amps and NOT the laws of physics. Which I suspect is the lynch pin of this debate.

[K Teacher]

Well, everybody is entitled to their own opinion.

If you don't enjoy a pedantic, dry and theoretical discussion, stay away from the amps, theory and design section !!

For me, I read the theory and I verified it in practice.

I can tell you, that back in 2008, I built a Mojotone 5E3 Tweed Deluxe replica (approx.14W output) with Weber 12A125 speaker, which was broke-in for 10hrs. before install. After that, I built another Mojotone replica, a Tweed Super 5F4 amp (approx.35W output) and used a pair of Weber's 10A125; also, 10hrs break-in before installing them in the amp.

I spent about 6mo with the Tweed Super, because I thought there was something wrong with it. At full tilt, it was just a smidge louder than the 5E3. I then replaced the Weber's 10A125, with new Jensen's P10Q (also broke in for 10hrs.) -- same result !

I did a lot of reading, research and measurements to find out, at the end, that there was NOTHING wrong with the 5F4. BTW, I had hearing test done, and my hearing is fine.

I also like to note, that I listened to these amps, side-by-side, same everything else.

Now, if you are talking about the 57 Tweed Deluxe reissue, with a P12 Jensen (95dB SPL) vs. a 65 Deluxe Reverb, with a C12 Jensen (100dB SPL), then it's another story. That would be like comparing the loudness of a 14W amp with a 44W one, with the SAME speaker efficiency) !!

I did my tests and I have my answers.

So, you believe what you want, I don't care…

I thought on opening a new tread about the "6V6s at 420V plates", but I was concerned that all of this blather was going to continue there too, so I create this one instead.
I just wanted to create a tread for people to talk about loudness, and get it out of the way, so I could learn more about the 6V6s at 420V plates, from people with experience on that particular issue.

But I guess this is not gonna happen, is it ?

How foolish of me, one can't teach what one don't know…

[Chuck H]

Take it easy. I'm actually in total agreement with you. I'm just noting there is a devil in the details when it comes to guitar amps and the variables of their construction. Certainly two amps with similar charactersistics for tonality, speaker efficiency and peak performance ratio, with the only actual difference being ten watts between them, will have an almost indiscernible difference in volume.

Instructing me to stay away from the forum is just mean and I really think you're taking this too personally.

I know you believe that the high voltage used on 6V6's by Fender was the result of marketing hype. Fine. It probably was. YOU believe what you want just as you have instructed me. I'm just saying that maybe it wasn't marketing hype. A dB here and a dB there can eventually add up. Higher performance is higher performance. Even if it's not much higher. At some level you don't have enough and at some level you do. So at what point should Leo have stopped trying to get more performance? These are nebulous questions burried in history that can only be speculated on.

[loudthud]

I want to get a gig playing the National Anthem at a Baseball game. I'd really like to use two 100W double stacks, but somehow it seems wrong to use Marshall cabinets. I only have one Fender 4x12 with Vintage 30's. Will that be enough ? Gotta play loud enough to get feedback with a Les Paul.

[Helmholtz]

I did my tests and I have my answers.

So have others.

So, you believe what you want, I don't care…

If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent.

How foolish of me, one can't teach what one don't know…

This might be one of your problems.

I just wanted to create a tread for people to talk about loudness, and get it out of the way, so I could learn more about the 6V6s at 420V plates, from people with experience on that particular issue.

Here's a practical experience:
I have a great sounding little 18W Rivera Fender Super Champ (2x6V6, B+ around 400V)
It's just not powerful enough for me (lead guitar in a medium loud blues/rock band) even when paired with an EVM 12L in a larger cabinet.
I'm typically fine with a '63 Brown Vibroverb Reissue (35W) in smaller venues.
So the Super champ to me only is a nice practice amp.

According to acoustics expert and guitar player Prof. Manfred Zollner, it's around 4dB which makes the difference between "always somewhat too low" and "loud enough" in a typical stage situation.

[pdf64]

… I built a Mojotone 5E3 Tweed Deluxe replica (approx.14W output) with Weber 12A125 speaker, which was broke-in for 10hrs. before install. After that, I built another Mojotone replica, a Tweed Super 5F4 amp (approx.35W output) and used a pair of Weber's 10A125; also, 10hrs break-in before installing them in the amp.

I spent about 6mo with the Tweed Super, because I thought there was something wrong with it. At full tilt, it was just a smidge louder than the 5E3. I then replaced the Weber's 10A125, with new Jensen's P10Q (also broke in for 10hrs.) -- same result !

35W seems unrealistic for a 5F4, did you check that, or the 14W you note for the Tweed Deluxe build?
Mojo suggest 20 to 30W for their 5F4 kit.

The SPL those amps can generate will depend on the speakers. Weber don’t publish that info, probably because it’s not feasible, due to them offering so many options.
Also a 2x10 will project differently to a 1x12.

[g1]

Although an increase of 3dB represents a doubling in power, an increase of about 10dB (10x more power) is required, before the sound subjectively appears to be twice as loud. The smallest change one can hear, is about 3dB. Or in other words, an average person, with everything the same (specially speaker's efficiency), can barely tell loudness difference between a 5W amp and a 10W one; and a 50W amp will be perceived to be twice as loud as a 5W amp !!

Therefore, an output power increase from 14W to 22W, with all else being the same (including the speaker), cannot be heard by an average person.

I'm not sure why you put italics where you did here, but you are mixing quotes and your own personal opinions.
The first part, before the "in other words" comes from this link (2nd paragraph), and it is a direct quote: https://www.e2s.com/references-and-g...ecibel-ratings

That is fine although you should show your source when quoting verbatim like that. Then you add your own 'can barely tell' which is the opposite of what many observe. Here is a source for my assertion: https://www.soundonsound.com/sound-a...e-change-level

To further muddy the waters and risk going off topic again, you are invested in your assertions to back up your claim in the other thread; about why amp models power output levels increment the way they do ("That explains why there are a lot of 5W amps but not many 10W ones! Same goes for 15W and 30W or 50W and 100W ones… Doubling the power doesn't cut it").
Generally, power output levels are based around output topology, single ended, pairs, quads, not db ratings.

Lots of players put 6L6 in their 6V6 amps for a very modest low end boost. It is perceivable and measurable. Some hear it and some don't. There are blanket generalizations we can make about novice players, but they do not account for seasoned veterans who are attuned to every nuance of their gear.

[Helmholtz]

Lots of players put 6L6 in their 6V6 amps for a very modest low end boost. It is perceivable and measurable.

I like your post above, but can't agree with this statement.
Tubes don't have an intrinsic frequency response as tube parameters don't depend on frequency.
Means that any tube can have a flat response from 0 Hz up to MHz, provided the circuit supports it.
6L6s may give a bit more output than 6V6s because their saturation plate voltage is lower, but will not boost bass.
If there are FR measurement results demonstrating otherwise, please show them.

[g1]

Tubes don't have an intrinsic frequency response as tube parameters don't depend on frequency.

Yes, I agree with you and my wording was not good. The 'fuller bottom end' is the reasoning that is usually given for the swap. As you say, it should actually be a bit better peak response across the frequency range. I don't have any FR data, sorry.
In any case I would think it would be much less than 3db, more likely closer to the 0.25db gain stated in the link I posted above.

[35L6]

Your "bass boost " may be Fletcher Munson raising it's ugly head agai n . Psycoacoustics confound analysis of small changes in volume . And yes , the total is made of many small parts . Maybe more than we'll ever know but I can measure Watts . Well , sort of , speaker load varies with frequency . I did the test ( rather crudely ) with the 1 to 1.4 voltage gain . The difference wasn't huge but noticeable .If I had changed my amp from cathode bias to fixed bias and got that change I would be happy .

[loudthud]

Many of the perceived differences in tone experienced when changing output tubes are due to changes in open loop gain and damping factor. You probably won't see any difference when measuring frequency response into a dummy load. Expect some measurable difference in power output and clipping waveform shape.

[Chuck H]

Hang in there. This is going to get pedantic

So a ten watt amp isn't noticeably louder than a five watt amp. (<period)
A twenty watt amp isn't noticeably louder than a ten watt amp. (<period)
A fourty watt amp isn't noticeably louder than a twenty watt amp. (<period)
An eighty watt amp isn't noticeably louder than a fourty watt amp. (<period)

etc. ad nauseam

So why don't metal players use Fender Champs??? Since a one hundred watt amp isn't noticeably louder than a four watt amp.

The implication that wattage differences don't make volume differences unless they are measured in specific amounts is ridiculous.

Drop something and it will never hit the floor. I can prove it. It has to travel an indefinite number of halfway intervals before reaching it. Therefor it never does.

[Chuck H]

If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent.

I'm going to sig this.

[Helmholtz]

So a ten watt amp isn't noticeably louder than a five watt amp. (<period)
A twenty watt amp isn't noticeably louder than a ten watt amp. (<period)
A fourty watt amp isn't noticeably louder than a twenty watt amp. (<period)
An eighty watt amp isn't noticeably louder than a fourty watt amp. (<period)
etc. ad nauseam
.

That is a very good point.