[JackD201]

10dB is just an average which became the rule of thumb over time. The roots of this hark back to the time before electronics to the days when larger conservatories and opera houses were being built. Some instrument sections particularly woodwinds and strings needed 8 or 9 more of the instruments playing the same note to sound "twice as loud". I underlined some because the doubling up is contingent on propagation and the assistance of purpose designed boundary reinforcement. Tubas and Kettle Drums for instance needn't have an additional 8 or 9 pieces. This frequency and reinforcement dependencies makes the 10dB rule of thumb misleading . No surprise now that there is so much need for bass control products in the here and now even for folks whose speakers go only into the low 50s. Also being just an average anywhere from 3 to 12dB can be perceived as doubling up depending on the noise floor and the reference level set above that.

To get back on topic I think JoshK nailed it. Distortion definitely is a factor. Another "rule of thumb" is that tube watts sound twice as loud as a solid state amp of the same power rating. It's something I've found true a lot of the time but again not all the time. Conversely I've found that as damping factor increases in a tubed design the closer the perceived loudness goes to SS amps of the same power rating. Could that be part of the answer? Overhang especially in the lower octaves gives an illusion of fullness which can be misconstrued as having more bass just as midbass humps in smaller speakers sound as if they go lower. Again JoshK nailed it, a watt is a watt. I believe it is the way the watt is delivered and not the watt itself.

[roymail]

from JackD201
To get back on topic I think JoshK nailed it. Distortion definitely is a factor. Another "rule of thumb" is that tube watts sound twice as loud as a solid state amp of the same power rating. It's something I've found true a lot of the time but again not all the time. Conversely I've found that as damping factor increases in a tubed design the closer the perceived loudness goes to SS amps of the same power rating. Could that be part of the answer? Overhang especially in the lower octaves gives an illusion of fullness which can be misconstrued as having more bass just as midbass humps in smaller speakers sound as if they go lower. Again JoshK nailed it, a watt is a watt. I believe it is the way the watt is delivered and not the watt itself.

Thanks, that's helpful.  Perhaps I should have asked if there really is any difference.  I use to have a 6 watt RWA ClariT amp.  It wasn't a tube amp but it was my first exposure to what was possible with lower powered amps.  I was amazed at the volume and quality of sound that came from that little amp.  Of course it was SLA battery driven which underscored the importance of a good power supply.  I admit, I've got a lot to learn.

[Pez]

10dB is just an average which became the rule of thumb over time.

As long as we agree that 3 db is not twice as loud.

[JackD201]

Fine by me Pez, as long as you don't get "technical about it" because if you do there are indeed instances (frequency in the 3 to 5kHz range, 50 dB masking level for instance) that 3dB may be even more than twice as loud. For me to insist on this however would be me just being a pr#ck because I'd just be splitting hairs.  I don't listen to recordings of crickets for fun and I don't know anybody else that does either. So yeah, I'll concede that under normal conditions 3dB won't cut it.

[JackD201]

Hi Roy, we all have a lot to learn. I've never owned or even tried any battery operated amps but have read that the other-wordly silence can be profound. That Dodd battery powered tube amp looks mighty interesting and I've been eyeing it for months now, I have a pair of speakers that look like a good candidate for 'em.

[Pez]

  I don't listen to recordings of crickets for fun and I don't know anybody else that does either.

The soundtrack to your life?   

Seriously though I think it's pretty much agreed on that measuring human perception is pretty futile. That's why this hobby is such a mind f@#$. Engineers, listeners, scientists all are equally bad at quantifying that which by definition is unquantifiable.

[JackD201]

Yeah it can feel that way huh and that's what makes this hobby more contentious than most. Yet the discussions can still be fun as long as those that can dish it can take it  aa

[srb]

Engineers, listeners, scientists all are equally bad at quantifying that which by definition is unquantifiable.

Yeah it can feel that way huh and that's what makes this hobby more contentious than most.

Ain't that the truth?  If our hobby was racing cars in the quarter mile, it would be pretty cut and dried.  A 9.9 second time is better than a 10.1 second time.  Not subject to perception or interpretation.
 
Steve

[Ericus Rex]

Sorry to revive this long dead thread, but this controversy still rears its head in the tube-o-phile every so often and I've found new info on why tube watts sound louder (more dynamic is my preferred terminology) than ss watts.  It's in Bruce Rozenblit's brand new book "Tubes and Circuits" pages 126-7.  The explanation is too long to reprint here in full and requires lots of back info to digest anyway.  But he basically says that 'the movement of the donor electrons in the cathode drop the resistance of the tube and allow for a transient current peak 5-10 times the tube's rated steady-state level for the span of a few milliseconds.'  This is a temporary condition and may explain why the effect is not always noticeable.  'If music is generally steady with an occasional peak the donors can handle it, but if the music has many steady peaks the donors won't have enough time between peaks to be replenished.'  In the latter case, the tube equipment's peaks and the ss amp's peaks will sound more similar.  It's all a little over my head and I hope I've relayed it here accurately.  Anyway, the book is good (I just started my second reading of it) and I'd recommend it to anyone wanting to understand their tube amp and it's complexity.  Maybe we can now put this issue to rest?