Constant Power

[Duke LeJeune]

I think you've got this backwards. You're the one making the claims. Specifically that a properly matched OTL amp/speaker combo can deliver both deeper and smoother bass than an unnamed SS amp/speaker combo. The burden of proof is yours. I won't trouble you to do any modeling, though. Just some independent measurements of the response of a speaker/amp combo you consider appropriate would be a good start, as I'm not really looking for "proof," just some evidence more substantive than the opinion of someone with a vested interest in the outcome.

Okay, so you don't want to put any effort into this in the interest of making sure there's no grounds for questioning my choice of examples.

Thanks (I think) for your offer to accept independent measurements in lieu of modelling, but I don't have access to the independent measurements you are asking for and am not about to spend the time and money it would take.

So I did some modelling. I modelled three prosound subwoofers, the Eminence Kappalite 3015LF, Kilomax Pro-15A, and B&C 15TBX100, following the procedure outlined in my previous post. Minimum F3 for these subwoofers in 6 cubic feet, optimally tuned, was 40 Hz, 39 Hz and 38 Hz, respectively (and the one that goes down to 38 Hz has over 2 dB of "droop" in its curve from 72 Hz on down, so it falls short on smoothness). F3 for my example was 32 Hz. And if I optimally tune the woofer/box combo in my example, we can get down to 31 Hz. That's nearly 1/3 octave greater bass extension with no increase in box size, and no loss of efficiency, simply by going from an optimized system driven by a solid state amp to an optimized system driven by an OTL amp.

Let me know your reaction to this, and we'll go from there. You or anyone else are more than welcome to provide a counter-example that disproves my claim.

 

[KeithR]

Then your practical experience is disputing the case being made here for constant power, etc. That argument falls apart if amps regardless of output impedance sound great.

put me in the camp that Wilson's have always sounded best with tubes---and I've owned Sophias and had both types of amps. as I recall, i've also heard Dr. Williams setup both ways.

 

[Atmasphere]

Or you can use a McIntosh tube/transformer amp (or the like) which has an output impedance of <0.1 ohms.

This constant hammering on feedback is getting a little tiresome. Does not the McIntosh use feedback? And what does feedback have to do with how we perceive sound pressure? Please explain the fundamental rule to which you refer. Thanks in advance.

When global loop feedback is applied to nearly any amplifier you will get a slight enchancement of odd-ordered harmonic distortion, on account of the propagation delay in the amp. Odd orders are used by the human ear/brain system to sort out sound pressure. That is why I hammer on negative feedback so much- it makes any amplifier brighter than the real thing.

Really now? You described the Power Paradigm as follows:

"The Power Paradigm
The Power Paradigm assumes that amplifiers produce power and speakers are power-driven. Current produced by a power amplifier is not ignored and is considered in the amplifier's power response. Under this model, the ideal amplifier will make the same power into all loads, 4, 8 and 16 ohms. The typical amplifier, in this case, is a vacuum tube amplifier which usually makes its power into these loads via taps of its output transformer."

The quote is correct but your interpretation strains credulity. We can see that just because an amplifier is typical does not make it the only example. Our amps are good examples too and they don't have a transformer (however OTLs overall are rare so most of the amps will have a transformer as most of them are also tube; are we arguing about 'typical' vs 'most'??). If we apply enough feedback to our amps they can become voltage sources. Its about the feedback.

You state in your paper the “typical” amplifier that meets the power paradigm model is a vacuum tube amplifier that makes its power into these loads via taps of its output transformer. McIntosh makes tube amplifiers with output transformers. McIntosh also makes SS amplifiers with output transformers (autoformers). According to your paper above, that puts McIntosh squarely into the power paradigm camp. Now output transformers have nothing to do with the paradigm an amp fits into and “it is more about global feedback”? And again, I asked you if you had any papers you could reference with regards to McIntosh being leaders in the voltage paradigm, but I received no answer one way or the other.

With regards to the comment in bold, the paper says nothing of the kind. It does however say that this is more about feedback than it is about solid state vs tubes. Why do I have to keep pointing things like this out to you?? You say you read the paper but then it really seems as if you didn't.

I did mention in the comment wherein I included Mac that EV was one of the others that lead the way in the Voltage Paradigm. I mentioned one of the early articles by the head EV engineer elsewhere in this thread.

 

[KeithR]

Really now? You described the Power Paradigm as follows:

"The Power Paradigm
The Power Paradigm assumes that amplifiers produce power and speakers are power-driven. Current produced by a power amplifier is not ignored and is considered in the amplifier's power response. Under this model, the ideal amplifier will make the same power into all loads, 4, 8 and 16 ohms. The typical amplifier, in this case, is a vacuum tube amplifier which usually makes its power into these loads via taps of its output transformer."

You state in your paper the “typical” amplifier that meets the power paradigm model is a vacuum tube amplifier that makes its power into these loads via taps of its output transformer. McIntosh makes tube amplifiers with output transformers. McIntosh also makes SS amplifiers with output transformers (autoformers). According to your paper above, that puts McIntosh squarely into the power paradigm camp. Now output transformers have nothing to do with the paradigm an amp fits into and “it is more about global feedback”? And again, I asked you if you had any papers you could reference with regards to McIntosh being leaders in the voltage paradigm, but I received no answer one way or the other.

well, McIntosh does use negative feedback. i will also say that Mac amps sound more like tubes because of the output transformers most likely. they would probably sound even better without the negative feedback. I had MC601s in my system for a full year fwiw

 

[Atmasphere]

well, McIntosh does use negative feedback. i will also say that Mac amps sound more like tubes because of the output transformers most likely. they would probably sound better without the negative feedback.

Well there is a nuance here. And that is how the amp performs open-loop (feedback disconnected). Some amplifier designs can't be operated this way at all- they rely on the negative feedback. Other amplifiers already have good linearity without feedback. Most of the latter are actual tube amplifiers, because this is easy to do with tubes.

 

[microstrip]

Really now? You described the Power Paradigm as follows:

"The Power Paradigm
The Power Paradigm assumes that amplifiers produce power and speakers are power-driven. Current produced by a power amplifier is not ignored and is considered in the amplifier's power response. Under this model, the ideal amplifier will make the same power into all loads, 4, 8 and 16 ohms. The typical amplifier, in this case, is a vacuum tube amplifier which usually makes its power into these loads via taps of its output transformer."

You state in your paper the “typical” amplifier that meets the power paradigm model is a vacuum tube amplifier that makes its power into these loads via taps of its output transformer. McIntosh makes tube amplifiers with output transformers. McIntosh also makes SS amplifiers with output transformers (autoformers). According to your paper above, that puts McIntosh squarely into the power paradigm camp. Now output transformers have nothing to do with the paradigm an amp fits into and “it is more about global feedback”? And again, I asked you if you had any papers you could reference with regards to McIntosh being leaders in the voltage paradigm, but I received no answer one way or the other.

Mep,

There is a fundamental difference between referencing the transformer coupled tube power amplifier as an example of the properties of the Power Paradigm as Ralph did and its normal operation. You can not dynamically change taps in operation of an amplifier. In normal operation you are stuck with one impedance tap and variable power versus impedance. OTLs have the same power versus impedance in normal operation - no taps to change. This is a big difference, and IMHO makes your post #1 referring to the RM9 compared to the Ma1 and the current comparison meaningless and error inducing.

Again IMHO it seems to me you are misinterpreting the Power Paradigm as specified by Ralph.

 

[KeithR]

I think the bottom line with this thread is properly matching of speakers with amps is CRITICAL to successful sound. but the old "amps have to double down to provide loads of watts and current" adage has been debunked as I see it with certain speakers.

I will say empirically in my system (17 amps in 3 years and counting)- the best amps I have heard eschew the use of global negative feedback. And that includes an Ayre VX-5 which is certainly no SET.

 

[microstrip]

Then your practical experience is disputing the case being made here for constant power, etc. That argument falls apart if amps regardless of output impedance sound great.

Amir,
Only if we forget that sounding great is an expression of a preference and is much more than perceived flat frequency response.

 

[ack]

You mean voltage paradigm, no? Are not most amps voltage paradigm? Certainly true for SS amps. I'd say also the case for tube amps. First, we have to use the correct criteria. This "same power for different impedance" is being misinterpreted as a criterion for power paradigm. This has a) nothing to do with the max output (i.e. 10% or 1% THD) power, and b) it has nothing to do with a nice tube amp such as McIntosh that offers the same total power into 2, 4, 8 ohms, as that only happens when the speaker of that impedance is connected to those three different sets of output transformer taps.

Every illustration of how amp/speaker matching interaction affects sound quality ignores all of this, and focuses (rightly) on how the varying impedance of a speaker over frequency interacts with the output impedance of the amp. If the nominal 4 ohm speaker has an 8 ohm impedance at the crossover, changing the connections to the 8 ohm taps is not an option.

So if we can ignore power supply stiffness and output transformers, we'll much more quickly arrive at the operative characteristics of the amp/speaker interaction that affect sound quality.

A modest SS amp might have a damping factor of 40 into a 4 ohm load. That means an output impedance of 0.1 ohm. What would be the damping factor of a McIntosh tube amp? Anyone? They state >40 wideband for the MC302. So it exhibits the same 0.1 ohm source impedance as a SS amp. Sure, you can find SS amps with higher damping factor, but after 10 - 20 feet of speaker cable, it might not matter.

Based on my previous paragraph, I would assert that the McIntosh amps are voltage paradigm, since they behave essentially the same as far as the amp/speaker relationship is concerned as SS voltage paradigm amps. Atma-Sphere stated a power paradigm amp exhibits "moderate output impedance (1-20 ohms is typical)". An easy way to make an amp with a 10 ohm output impedance is to add a 10 ohm resistor in series with the speaker. Or pick whatever value makes the speaker sound best.

Thanks for your response - I highlighted some key points in your post, which are relevant to the questions below.

First, let me repeat my first question: "name *current-day* SS amplifiers or other tube amplifiers that are not following the power paradigm" [hence, yes, I was asking which ones follow the voltage paradigm] - the responses included Pass, D'Agostino, Ayre, Dartzeel; it was further pointed out that any amp with damping factor of <100 has a low damping factor, thus higher output impedance. To repeat, these are amps that DO NOT follow the power paradigm; now let's focus on of the highlighted statements above (which was in response to my second question: how do you factor output impedance into all of this): Atma-Sphere stated a power paradigm amp exhibits "moderate output impedance (1-20 ohms is typical)" - that would translate to a *very low* damping factor. So can I then draw the conclusion that Atmasphere amps DO NOT follow the power paradigm either? Do you see my confusion???

Then we have andy_c's post #33 upthread, which allegedly shows that: at the frequency for which the speaker impedance is large, there is substantial frequency response peaking caused by the high output impedance

I would love for someone to clarify for me what is going on and what we are all saying here...

 

[mep]

That's not a woofer that I would ever use with a power paradigm amplifier. Instead, let's look at the Faital 12FH520. This is a high efficiency 12" prosound woofer with a very good motor, smooth response to nearly 3 kHz on-axis, and inadequate bass response when driven by a voltage paradigm amp. Except for that inadequate bass response, it's a good candidate for a high performance two-way with a horn or waveguide for the top end. My modelling software assumes an amplifier with negligible output impedance, and suggested .8 cubic feet tuned to 62 Hz for a F3 of 75 Hz as being a "maximally flat" alignment. Hardly inspiring bass performance.

So the Faital 12FH520, when driven by a solid state amp, is at best a midwoofer that would need help from a subwoofer, but it becomes a serious fullrange woofer when driven by one of Ralph's amps.

I’m not following your logic here. The above speaker has an FS of 50Hz which means it was never really designed to be a subwoofer as we mentioned yesterday (or at least I did). You put that speaker into a .8 cubic foot box tuned to 62 Hz, power it with a SS amp, and say it will have “hardly inspiring bass performance.” Well, of course it doesn’t have inspiring bass performance because it was never designed to.

Next you want to build a six cubic foot box which is over six times bigger than .8 cubic foot box and you want this box tuned for 35 Hz. So now we have a much, much bigger box tuned much lower, but your driver still doesn’t have much output below 50 Hz. Now somehow if you hook up an Atma-Sphere M-60 to this speaker with an FS of 50Hz, you will get a flat bottom that extends to the lower 30s? How many dB down will this driver be in the lower 30s? Since this is an 8 ohm driver which would also be an odd choice for a subwoofer, how is it that you would get more bass extension from an OTL than you would a SS amp? Oh, would that be because the SS amp was hooked up to a .8 cubic foot box tuned to 62 Hz and the OTL amp was hooked up to a six cubic foot box tuned to 35 Hz? We are hardly comparing apples to apples here.

This whole exercise seems wacky and not “real world” in the sense that who would really take a speaker never designed to be a subwoofer and put it in a big box and power it with an OTL amp so they could make the speaker supposedly do something it was never designed for?

 

[FrantzM]

Quite an expensive way to get bass if you ask me .. I would rather optimize the driver with really cheap power from a plate amplifier or a Class D Pro amp .. I am not following the logic .. Maybe this is just a thought experiment ...

I must say that I have found the bass from the Joule Electa Rite Of Somehing , OTL amps, startling. Actually the whole presentation was superb. I haven't heard an Atmasphere since the mid 90's so can't comment.

 

[mep]

Mep,

There is a fundamental difference between referencing the transformer coupled tube power amplifier as an example of the properties of the Power Paradigm as Ralph did and its normal operation. You can not dynamically change taps in operation of an amplifier.

I know, I already pointed that out in a previous post. You and Ralph are trying to have your cake and eat it too. Don't tell me that the "typical" power paradigm amplifier is a tube amp with output transformers that put out the same power at 4,8, and 16 ohms and then tell me it's not.

In normal operation you are stuck with one impedance tap and variable power versus impedance.

I know, I know. You keep repeating what I have previously said in another post.

OTLs have the same power versus impedance in normal operation - no taps to change. This is a big difference, and IMHO makes your post #1 referring to the RM9 compared to the Ma1 and the current comparison meaningless and error inducing.

I couldn't disagree more. I contend that OTLs do not have the same power versus impedance. The measurements of Ralph's MA-1 showed how big the discrepancy is between 4-16 ohms at 1% THD. The power levels aren't close. If you can come up with some other measurements of other OTLs that show they put out the same power as impedance rises up to 16 ohms, please publish them. My comparison of the RM-9 and the MA-1 was spot on in my opinion because the RM-9 fit the definition of a power paradigm amplifier as described by Ralph in his paper. The MA-1 did not.

Again IMHO it seems to me you are misinterpreting the Power Paradigm as specified by Ralph.

That's your opinion and I don't agree. Frankly, since Ralph twists everything around including even his own words to suddenly mean something else other than what was originally written and he is relentless in his attacks on me and the mods aren't stepping in to stop the nonsense, I'm not posting anymore on this thread even though I started it because you can't have a decent discussion with someone who is bent on subterfuge and name calling. I'm sick of the nonsense and I started this thread to eliminate the nonsense of the other thread which started this one off. I'm off of this merry-go-round. All of this going around in circles is just way too much.

 

[Atmasphere]

First, let me repeat my first question: "name *current-day* SS amplifiers or other tube amplifiers that are not following the power paradigm" [hence, yes, I was asking which ones follow the voltage paradigm] - the responses included Pass, D'Agostino, Ayre, Dartzeel; it was further pointed out that any amp with damping factor of <100 has a low damping factor, thus higher output impedance. To repeat, these are amps that DO NOT follow the power paradigm; now let's focus on of the highlighted statements above (which was in response to my second question: how do you factor output impedance into all of this): Atma-Sphere stated a power paradigm amp exhibits "moderate output impedance (1-20 ohms is typical)" - that would translate to a *very low* damping factor. So can I then draw the conclusion that Atmasphere amps DO NOT follow the power paradigm either? Do you see my confusion???

Then we have andy_c's post #33 upthread, which allegedly shows that: at the frequency for which the speaker impedance is large, there is substantial frequency response peaking caused by the high output impedance

I would love for someone to clarify for me what is going on and what we are all saying here...

An amplifier with a damping factor of 100 or even 20 is likely in the Voltage Paradigm. Usually such high damping factors are obtained by use of feedback although the Ayre is an exception. So we are talking about amplifiers that will likely have a damping factor less than 20. You might want to refer to the Tomcik article I mentioned earlier- what we see from this article is that no speaker needs to have a damping factor of more than 20:1 to control it, and some speakers are adversely affected if the damping factor is as high as 2:1. A lot depends on the Q of the speaker and what kind of baffle (if there is one).

The main issue here though is feedback, not the damping factor. There is a nuance here of course as damping factor does relate to output impedance.

Now here is one that is tricky for some, especially if schooled in the Voltage camp: the output impedance is measured differently depending on which paradigm you subscribe to. In fact two different things are being measured. In the Power Paradigm we are measuring the actual output impedance of the output circuit using a black box technique. In the Voltage Paradigm we are measuring the servo gain available to the output section. The two are not the same! The Radiotron Designer's Handbook was published in the early 1950s and so is on the Power Paradigm; it has a simple formula for calculating output impedance in an amplifier. It is within 5% of what we measure in our amps using a black box technique. If you use the Voltage Paradigm method on the same amp you get a value that is much higher. This particular difference between the two approaches can be confusing!!

 

[Duke LeJeune]

I’m not following your logic here. The above speaker has an FS of 50Hz which means it was never really designed to be a subwoofer as we mentioned yesterday (or at least I did). You put that speaker into a .8 cubic foot box tuned to 62 Hz, power it with a SS amp, and say it will have “hardly inspiring bass performance.” Well, of course it doesn’t have inspiring bass performance because it was never designed to.

Right, with a solid state amp in a "maximally flat" alignment, that woofer doesn't go very deep. I never said it was a subwoofer and I don't know why you keep bringing that up.

Next you want to build a six cubic foot box which is over six times bigger than .8 cubic foot box and you want this box tuned for 35 Hz. So now we have a much, much bigger box tuned much lower, but your driver still doesn’t have much output below 50 Hz. Now somehow if you hook up an Atma-Sphere M-60 to this speaker with an FS of 50Hz, you will get a flat bottom that extends to the lower 30s? How many dB down will this driver be in the lower 30s? Since this is an 8 ohm driver which would also be an odd choice for a subwoofer, how is it that you would get more bass extension from an OTL than you would a SS amp? Oh, would that be because the SS amp was hooked up to a .8 cubic foot box tuned to 62 Hz and the OTL amp was hooked up to a six cubic foot box tuned to 35 Hz? We are hardly comparing apples to apples here.

Sorry if my wording was so unclear.

For an apples to apples comparison (same woofer, same box, same tuning, different amplifier output impedances), please see post number 45 by andy_c. To answer your two questions I have bolded above, "yes" and "-3 dB at 32 Hz".

This whole exercise seems wacky and not “real world” in the sense that who would really take a speaker never designed to be a subwoofer and put it in a big box and power it with an OTL amp so they could make the speaker supposedly do something it was never designed for?

Once again, that speaker is not a subwoofer, but if we can get it to go down to 32 Hz, then it makes a really good woofer for a high output two-way system. It has plenty enough excursion (7.25 mm Xmax) and thermal power handling (1200 watts music program) to serve as a woofer in a two-way system, so your argument that "it was never designed for" this both incorrect and irrelevant.

If you would like to see some data on how this woofer on an OTL amp compares with three prosound subwoofers on solid state amps, same efficiency and same box size, see post #101. Please don't get distracted by the semantics. A subwoofer is a type of woofer, and both are constrained by the same laws of physics.

 

[ack]

An amplifier with a damping factor of 100 or even 20 is likely in the Voltage Paradigm. Usually such high damping factors are obtained by use of feedback although the Ayre is an exception. So we are talking about amplifiers that will likely have a damping factor less than 20.

OK - so power paradigm amps are those with damping factors roughly <20, not < 100. And these will offer roughly constant power to a varying impedance load. Then how do we explain andy_c's graph in post #33???

You might want to refer to the Tomcik article I mentioned earlier- what we see from this article is that no speaker needs to have a damping factor of more than 20:1 to control it, and some speakers are adversely affected if the damping factor is as high as 2:1. A lot depends on the Q of the speaker and what kind of baffle (if there is one).

Yes, I will read.

The main issue here though is feedback, not the damping factor. There is a nuance here of course as damping factor does relate to output impedance.

Yes there is, and yes it does relate.

Now here is one that is tricky for some, especially if schooled in the Voltage camp: the output impedance is measured differently depending on which paradigm you subscribe to. In fact two different things are being measured. In the Power Paradigm we are measuring the actual output impedance of the output circuit using a black box technique. In the Voltage Paradigm we are measuring the servo gain available to the output section. The two are not the same! The Radiotron Designer's Handbook was published in the early 1950s and so is on the Power Paradigm; it has a simple formula for calculating output impedance in an amplifier. It is within 5% of what we measure in our amps using a black box technique. If you use the Voltage Paradigm method on the same amp you get a value that is much higher. This particular difference between the two approaches can be confusing!!

Now that's very clear, thank you. I now need to study all of this.

 

[Phelonious Ponk]

Okay, so you don't want to put any effort into this in the interest of making sure there's no grounds for questioning my choice of examples.

Thanks (I think) for your offer to accept independent measurements in lieu of modelling, but I don't have access to the independent measurements you are asking for and am not about to spend the time and money it would take.

So I did some modelling. I modelled three prosound subwoofers, the Eminence Kappalite 3015LF, Kilomax Pro-15A, and B&C 15TBX100, following the procedure outlined in my previous post. Minimum F3 for these subwoofers in 6 cubic feet, optimally tuned, was 40 Hz, 39 Hz and 38 Hz, respectively (and the one that goes down to 38 Hz has over 2 dB of "droop" in its curve from 72 Hz on down, so it falls short on smoothness). F3 for my example was 32 Hz. And if I optimally tune the woofer/box combo in my example, we can get down to 31 Hz. That's nearly 1/3 octave greater bass extension with no increase in box size, and no loss of efficiency, simply by going from an optimized system driven by a solid state amp to an optimized system driven by an OTL amp.

Let me know your reaction to this, and we'll go from there. You or anyone else are more than welcome to provide a counter-example that disproves my claim.

Even if I were qualified (which I'm not) to do the kind of work you've proposed, why would I be interested in putting any effort into supporting your hypothesis? I'm not aware that you've offered up any examples; I may have missed them. What I'm questioning is your hypothesis: To paraphrase, that an OTL amp driving a properly-matched speaker would produce deeper, smoother bass than any SS amp powering any drivers in a cabinet of the same volume. (the "any" are assumptions on my part because of your lack of qualifiers to your hypothesis). Do I have that about right?

Are you unaccustomed to having this hypothesis questioned? If you are you must only state it to OTL devotees, because it certainly defies conventional wisdom. Again, you haven't defined what you mean by "smooth" or if you propose that the extension of these hypothetical speakers be measured in an anechoic chamber or with room gain, but if, by smooth you mean linear and you are talking about the extension of the speaker system, not the room, the hypothesis can pretty easily be tested. Give me an example. I feel pretty confident that I can find a relatively small subwoofer that will go deeper, flatter. What OTL amp? What speaker? What frequency response? It's your hypothesis and you made it with confidence; I would assume it based in some examples you've seen/heard/tested in your endeavors as a professional speaker designer. One example is all we need to start. One OTL amp/speaker combination that goes deeper/flatter than any SS/speaker combination in which the speaker is the same volume or less.

I will be more than happy to attempt to provide a counter-example when you've provided an example to counter.

Tim

 

[andy_c]

Now here is one that is tricky for some, especially if schooled in the Voltage camp: the output impedance is measured differently depending on which paradigm you subscribe to. In fact two different things are being measured. In the Power Paradigm we are measuring the actual output impedance of the output circuit using a black box technique. In the Voltage Paradigm we are measuring the servo gain available to the output section. The two are not the same! The Radiotron Designer's Handbook was published in the early 1950s and so is on the Power Paradigm; it has a simple formula for calculating output impedance in an amplifier. It is within 5% of what we measure in our amps using a black box technique. If you use the Voltage Paradigm method on the same amp you get a value that is much higher. This particular difference between the two approaches can be confusing!!

You haven't described this "black box technique", nor the formula from the Radiotron Designer's Handbook.

But measuring output impedance is done the same way regardless of the type of amplifier. You short the input of the amp, inject an AC current into its output, then measure the amplitude of the resulting AC output voltage. The ratio of the output voltage amplitude to the amplitude of the injected current is the magnitude of the output impedance. You just have to make sure the injected current is high enough so the measured output voltage is well above the noise, yet not so high that it causes the amp to operate in a nonlinear manner.

There's no magic or mystery whatsoever.

 

[hvbias]

I am taking what you say at face value. If so, then there has to be the case that solid state amps with the same speakers produce worse fidelity and speaker manufacturer agrees with that. It can't be that both amps as I mentioned to Steve sound great.

The larger Wilsons have relatively benign impedance curves compared to some of their smaller ones. So it could be any negative (or positive) effects of the amplifier were masked by the larger differences caused by the room.

 

[Duke LeJeune]

Even if I were qualified (which I'm not) to do the kind of work you've proposed, why would I be interested in putting any effort into supporting your hypothesis? I'm not aware that you've offered up any examples; I may have missed them. What I'm questioning is your hypothesis: To paraphrase, that an OTL amp driving a properly-matched speaker would produce deeper, smoother bass than any SS amp powering any drivers in a cabinet of the same volume. (the "any" are assumptions on my part because of your lack of qualifiers to your hypothesis). Do I have that about right?

Are you unaccustomed to having this hypothesis questioned? If you are you must only state it to OTL devotees, because it certainly defies conventional wisdom. Again, you haven't defined what you mean by "smooth" or if you propose that the extension of these hypothetical speakers be measured in an anechoic chamber or with room gain, but if, by smooth you mean linear and you are talking about the extension of the speaker system, not the room, the hypothesis can pretty easily be tested. Give me an example. I feel pretty confident that I can find a relatively small subwoofer that will go deeper, flatter. What OTL amp? What speaker? What frequency response? It's your hypothesis and you made it with confidence; I would assume it based in some examples you've seen/heard/tested in your endeavors as a professional speaker designer. One example is all we need to start. One OTL amp/speaker combination that goes deeper/flatter than any SS/speaker combination in which the speaker is the same volume or less.

I will be more than happy to attempt to provide a counter-example when you've provided an example to counter.

Tim

Did you even read my post? How is the modelling that I provided not an example??

Your assumption that I'm talking about "any" drivers in the same size cabinet is totally wrong. I guess you missed my preceding post as well, which I referred back to, in which my procedure is described. It's post number 87. I shouldn't have to do this for you. If you're going to argue with me, you should make a good-faith effort to read and comprehend what I have posted before you resort to assumptions.

Please go back and read my post number 101 again. I compare three prosound subwoofers driven by a solid state amp to a prosound woofer driven by an OTL amp. Same efficiencies, same box size, intelligently tuned, and the woofer driven by the OTL amp goes almost 1/3 octave deeper. That is my example. Argue against that instead of pretending that I didn't provide an example. If you object to my methodology, explain why. If you get different results, post that.

Smooth = minimal deviation from flat. You don't really need that quantified, do you? You run the model and eyeball the curves. The one that deviates from flat the least is the smoothest.

We have to compare equal size AND equal efficiency (dB/watt) speakers, otherwise it's not apples-to-apples and the least efficient speaker will very likely have deeper extension. Surely you understand this, right? If not, then you really aren't qualified to argue with me on technical issues that I understand and you do not. If that is the case, I suggest you google "Hoffman's Iron Law" to get started.

Of course what I'm claiming defies conventional wisdom. In this case, I believe that conventional wisdom is wrong, and I have provided evidence to that effect. Not proof, evidence. Kindly stop trying to find excuses for objecting and re-read my post.

 

[microstrip]

I know, I already pointed that out in a previous post. You and Ralph are trying to have your cake and eat it too. Don't tell me that the "typical" power paradigm amplifier is a tube amp with output transformers that put out the same power at 4,8, and 16 ohms and then tell me it's not.

I know, I know. You keep repeating what I have previously said in another post.

I couldn't disagree more. I contend that OTLs do not have the same power versus impedance. The measurements of Ralph's MA-1 showed how big the discrepancy is between 4-16 ohms at 1% THD. The power levels aren't close. If you can come up with some other measurements of other OTLs that show they put out the same power as impedance rises up to 16 ohms, please publish them. My comparison of the RM-9 and the MA-1 was spot on in my opinion because the RM-9 fit the definition of a power paradigm amplifier as described by Ralph in his paper. The MA-1 did not.

That's your opinion and I don't agree. Frankly, since Ralph twists everything around including even his own words to suddenly mean something else other than what was originally written and he is relentless in his attacks on me and the mods aren't stepping in to stop the nonsense, I'm not posting anymore on this thread even though I started it because you can't have a decent discussion with someone who is bent on subterfuge and name calling. I'm sick of the nonsense and I started this thread to eliminate the nonsense of the other thread which started this one off. I'm off of this merry-go-round. All of this going around in circles is just way too much.

Apologies if I missed your recent correction. But you are missing the main point. The so called "Power Paradigm" is not a mathematical rule that you can check with a calculator. It is IMHO one trend - similar or even less power versus impedance compared with the rule of increasing power with decreasing impedance of most other amplifiers. The different criteria that are used in tests for checking power in tube amplifiers rule out an ultra simplified analysis and are also part of the paradigm. Tube amplifiers measurements are not easy to correlate with their sound quality and maximum sound levels.

We should be thankful to have manufacturers here at WBF and learn from their posts. IMHO, in order to learn from them we must make an effort to see their perspective and aims - not just systematically and in an unfounded way object them.

Also IMHO there was no subterfuge in any of the manufacturers involved in this debate. I would be very happy if other manufacturers could expose their technicalities so openly. Perhaps you do not know, but Ralph published the schematics of his OTLs and helped many DIY people building them, and provides technical and support advice in audio forums to people owning his amplifiers. When possible, he supplies instructions and parts to people wanting to upgrade their units - his fair play and generosity is known in the OTL audiophile community. For more details look at the AudioAsylum OTL and Atmasphere archives.