Constant Power

[mep]

Peter-I read that article yesterday and found it quite interesting. It just reinforces what many of us know-we all don't like the same things in music reproduction.

 

[ack]

Peter-I read that article yesterday and found it quite interesting. It just reinforces what many of us know-we all don't like the same things in music reproduction.

Yes, quite interesting; been reading it the last few years again and again... Off topic, but I find Pass having matured a lot in his designs since the Aleph days - the last Pass product line I experimented with and found it to be what a lot of people hate about solid state.

 

[KeithR]

Peter-I read that article yesterday and found it quite interesting. It just reinforces what many of us know-we all don't like the same things in music reproduction.

it is a very well-balanced article. but what does seem obvious is no global feedback is optimum. whether you get that way with 2nd or 3rd preferred is more up for debate (push/pull, single ended, etc)

it all comes down to speaker/amplifier matching in the end though

 

[das]

My bigger question is what percentage of speakers being manufactured today were designed so that they will sound their best with an amplifier that conforms as strictly as possible to the power paradigm vice speakers that will sound their best when driven by voltage paradigm amplifiers?

This topic comes up surprisingly often, and you will find components that adhere to this so-called "power paradigm."

But to answer your question about how many are designed for CONSTANT VOLTAGE, the answer is: almost all. The reason I know this has to do with speaker measurements and how they're done. The standard is to applied a CONSTANT 2.83V across the frequency band, and with that the speaker comes out as flat as its intended to. In other words, it's made for a constant voltage. Although I'm sure they exist somewhere, I've personally never seen a speaker designed for constant power.

I first encountered this issue with an Orpheus Labs amp I reviewed VERY long ago -- it was a solid-state "constant power" amplifier. It had a special circuit so that its power remained the same regardless of load.

Doug Schneider
www.soundstage.com

 

[Duke LeJeune]

That was the Bose philosophy and I always found it to be flawed...

If that was indeed Bose's philosophy, its implementation (as embodied in the 901), is what was flawed.

For the right way to do it, see Floyd Toole's "Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms".

 

[Duke LeJeune]

in my other post, I referred to this whole issue as a variation of the old musical vs. accurate theme. When the designer's goal is to "replicate the perception of a live performance" or create musicality, or euphony, or warmth or an enveloping presence or whatever poetry of the day describes this approach to audio design, one thing is clear; the designer is endeavoring to broadly, systematically alter the art; all the art played on the system.

Whenever we adopt a definition of "accurate" that leads us away from recreating the perception of a live performance, we are measuring with the wrong yardstick (unless our audience is made up of test instruments).

It's not a bad idea to get a feel for how much of a divide there is between generally accepted distortion measurements (THD) and human auditory perception. Information and resources have been posted in this thread, but the concepts are not necessarily obvious - just like Toole's perspective on reflections certainly isn't obvious at first bounce.

If you're not familiar with what Toole has to say about in-room reflections, my post (the one you were responding to) probably didn't make much sense. Here's an excellent introduction:

http://www.madronadigital.com/Library/RoomReflections.html

 

[Duke LeJeune]

Although I'm sure they exist somewhere, I've personally never seen a speaker designed for constant power.

In November of 2001, SoundStage reviewed a speaker whose frequency response curve would have been smoother on a power paradigm amp than on the constant voltage amp used to measure it.

http://www.soundstagemagazine.com/measurements/silverline_panatella_ii/

Notice how, in the 3 kHz region, the frequency response curve zigs where the impedance curve zags.

There may have been others, I just happened to come across that one years ago and remembered it.

If you make it to RMAF, pop into the Lupine room and room 1100, and you'll walk away having seen at least two speaker systems designed for constant power.

 

[mep]

This topic comes up surprisingly often, and you will find components that adhere to this so-called "power paradigm."

But to answer your question about how many are designed for CONSTANT VOLTAGE, the answer is: almost all. The reason I know this has to do with speaker measurements and how they're done. The standard is to applied a CONSTANT 2.83V across the frequency band, and with that the speaker comes out as flat as its intended to. In other words, it's made for a constant voltage. Although I'm sure they exist somewhere, I've personally never seen a speaker designed for constant power.

I first encountered this issue with an Orpheus Labs amp I reviewed VERY long ago -- it was a solid-state "constant power" amplifier. It had a special circuit so that its power remained the same regardless of load.

Doug Schneider
www.soundstage.com

Doug-Thanks for your response-I do appreciate it. When I asked the question about how many speakers are designed for constant voltage, it was almost a rhetorical question because because I know that most speakers are designed that way. It has been proffered here that Wilson speakers are designed to be constant power speakers or at least one version of the WATT speaker had one place in the crossover region (2kHz) that needed a constant power amplifier. Ralph and Duke have a list of speakers they believe are power paradigm speakers and most are horns. And anything with a Lowther driver too.

 

[mep]

If that was indeed Bose's philosophy, its implementation (as embodied in the 901), is what was flawed.

For the right way to do it, see Floyd Toole's "Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms".

That was indeed Bose's philosophy and the entire reason he created the 901 to bring his dream to life. I would think that anytime you add something to the signal in order to change the sound, you have a high risk of having a flawed implementation. Whether it's 8 drivers firing backwards towards the wall so that most of the sound you hear is reflected or whether you add 10% THD to the signal.

 

[mep]

Yes, quite interesting; been reading it the last few years again and again... Off topic, but I find Pass having matured a lot in his designs since the Aleph days - the last Pass product line I experimented with and found it to be what a lot of people hate about solid state.

I had an X-250 and it had a lot of what I can hate about SS. I wrote a thread about it years ago on the Tape Project forum and I think I called it Solid State and Zombies. There was no meat on the bones and no soul there either.

 

[microstrip]

That was indeed Bose's philosophy and the entire reason he created the 901 to bring his dream to life. I would think that anytime you add something to the signal in order to change the sound, you have a high risk of having a flawed implementation. Whether it's 8 drivers firing backwards towards the wall so that most of the sound you hear is reflected or whether you add 10% THD to the signal.

Mep,
The idea is not adding 10% of distortion to anything. As far as I understand the main idea is having the proper relative values of the different harmonics, even if this has a consequence of getting an higher value of an harmonic that does not affect sound reproduction in a nasty way.

 

[mep]

i am not sure about that one. any time we even think that two channel is "supposed to or even attempt to" sound like the real event, its the first, and fundamental wrong step IMO. just as has been brought up in this thread about how the speaker attempts to control the amp, ie feedback or none in either case the speaker still controls the amp to certain extent, butr just differently, "stereo" controls the listening experience. its a totally differnt animal, and at best can hardly deal with more than three instruments playing at the same time before the IMD starts to "become" the new sound as opposed to the recorded sound. let alone, the "stereo effect".

i have never and never will expect a stereo to sound like the real thing, not in the same room. but play some simple acoustic guitar, and go down the hall to another room and yeah, you could have a hard time kmowing if its real or not.

IMO the first expectation to get over is ecpecting stereo to sound real. then, IMO, you are left with assembing a system that is accurate to the recording and adding in your own processing, or assemble as system that overall creates a sound you like, without processing. either camp, IMO works, but if you do the processing your less likely to feed the high end manufacturers sales though.

Another anti-two channel rant brought to you by Tom. If everyone felt the way you do Tom about how deficient two channel stereo sounds, it would have died out a long time ago. We would all be stuck with some sort of multi-channel sound. The majority of people on this forum have high-end two channel systems and love the illusion their systems and rooms provide. Your constant beating on the stereo illusion with both the statements you make in your posts and your tag line that is on everyone of your posts hasn't swayed anyone that their stereo doesn't sound as good as they think it does.

 

[mep]

Mep,
The idea is not adding 10% of distortion to anything. As far as I understand the main idea is having the proper relative values of the different harmonics, even if this has a consequence of getting an higher value of an harmonic that does not affect sound reproduction in a nasty way.

Fransisco-It might not be the idea to add 10% THD, but it's a byproduct of the design and it exists. You say it doesn't affect sound reproduction in a nasty way, but I guess we must ask relative to what? If you mean relative to high order odd harmonics (5th, 6th, 7th, etc.) you can probably achieves some degree of consensus on that. The bottom line is that 10% THD is going to affect the sound. It may affect the sound in a way that pleases you and others (and hell, it may please me when I hear some of Ralph's amps at RMAF), but have no doubt it will affect the sound.

 

[Duke LeJeune]

That was indeed Bose's philosophy and the entire reason he created the 901 to bring his dream to life. I would think that anytime you add something to the signal in order to change the sound, you have a high risk of having a flawed implementation. Whether it's 8 drivers firing backwards towards the wall so that most of the sound you hear is reflected or whether you add 10% THD to the signal.

The question of how to do reflections right (or whether reflections should be allowed at all) is an interesting one, and I highly suggest you read Amir's article (linked in post #207) before you paint reflections with an overly broad brush. Intuition and common sense would lead you to believe that encouraging any reflections amounts to a flawed approach because you are adding something to the signal in order to change the sound, but that paradigm ignores human perception and so is itself flawed.

Back to amplifiers. The power paradigm is not based on adding euphonic distortion; rather, the idea is to reduce or eliminate audible & objectionable high order/odd order distortion components and propagation delay (which are introduced by the high levels of global negative feedback typically needed to arrive at impressively low THD). As a consequence, the power paradigm approach may well result in unusually high levels of second order harmonic distortion (and 10% is a huge exaggeration if you're talking about Ralph's amps). The resulting relatively high THD spec looks worse on paper but is perceptually a good trade-off because up to 40% second harmonic distortion is statistically undetectable, and is not objectionable. You can find my sources for these claims back in post number 19.

It's not so much what's there with a good power paradigm amp (and what's there is benign with complimentary speakers); it's what's not there.

 

[microstrip]

Fransisco-It might not be the idea to add 10% THD, but it's a byproduct of the design and it exists. You say it doesn't affect sound reproduction in a nasty way, but I guess we must ask relative to what? If you mean relative to high order odd harmonics (5th, 6th, 7th, etc.) you can probably achieves some degree of consensus on that. The bottom line is that 10% THD is going to affect the sound. It may affect the sound in a way that pleases you and others (and hell, it may please me when I hear some of Ralph's amps at RMAF), but have no doubt it will affect the sound.

Mep,

I can not understand why you insist on the 10% figure. As said by Ralph the 10% is untrue - it was due to an inadequate measuring technique (these amplifiers have a DC coupled cyclotron output configuration) and an unit with faulty tubes. It can happen with the Atmasphere's - when they are faulty the tubes become open circuit and only affect reproduction reducing power - no tube big-bang!

 

[mep]

Mep,

I can not understand why you insist on the 10% figure. As said by Ralph the 10% is untrue - it was due to an inadequate measuring technique (these amplifiers have a DC coupled cyclotron output configuration) and an unit with faulty tubes. It can happen with the Atmasphere's - when they are faulty the tubes become open circuit and only affect reproduction reducing power - no tube big-bang!

Fransisco-Go back and read what Ralph said about the bad tubes and the way Bascom King took the measurements. I *believe* that Ralph said the reason the MA-1 didn't meet the specified power output was because of the defective tubes and the way Bascom set the variac. Ralph went on to say in another post that his newer amps have 90% less distortion than the MA-1 did which means that his current amps should measure 1% THD.

 

[Duke LeJeune]

Fransisco-It might not be the idea to add 10% THD, but it's a byproduct of the design and it exists. You say it doesn't affect sound reproduction in a nasty way, but I guess we must ask relative to what? If you mean relative to high order odd harmonics (5th, 6th, 7th, etc.) you can probably achieves some degree of consensus on that. The bottom line is that 10% THD is going to affect the sound. It may affect the sound in a way that pleases you and others (and hell, it may please me when I hear some of Ralph's amps at RMAF), but have no doubt it will affect the sound.

Fransisco-Go back and read what Ralph said about the bad tubes and the way Bascom King took the measurements. I *believe* that Ralph said the reason the MA-1 didn't meet the specified power output was because of the defective tubes and the way Bascom set the variac. Ralph went on to say in another post that his newer amps have 90% less distortion than the MA-1 did which means that his current amps should measure 1% THD.

Dude... wait a minute... are we on the same side now? It's getting harder and harder for me to find something to quibble about...

 

[mep]

Duke-Do you know if any magazine that takes measurements has reviewed one of Ralph's amps since the MA-1 review and we can see some measurements of the new amps? I would rather we had nothing to quibble about and I'm looking forward to meeting you at RMAF. You seem like a cool dude in a loose mood.

 

[Duke LeJeune]

Duke-Do you know if any magazine that takes measurements has reviewed one of Ralph's amps since the MA-1 review and we can see some measurements of the new amps? I would rather we had nothing to quibble about and I'm looking forward to meeting you at RMAF. You seem like a cool dude in a loose mood.

Thank you sir! And I'm sorry I got snarky with you there a time or two... sometimes I give in to my inner jerk.

Unfortunately I don't know of any recent article on Ralph's amps that include measurements.

 

[mep]

Duke-I for one never felt you were snarky and took zero offense at anything you said. It would be nice to see some independent measurements of one of Ralph's current amps to see how they have improved. Has the S/N ratio improved over the years?