Full range, quality high efficiency speakers tend to be big and expensive. I think you have blame the laws of physics for that!!! NEwer high efficiency amplifier technology is capable of taking a lot of the technical guesswork out of the equation and driving most ANY speaker well. PLus they are small and affordable! I assume you are talking about Class D or switching amps. I'd love to hear Atmasphere and Almarg comment about how that type of amplifier's inherent electrical characteristics interacts w speaker loads. W respect to the 'why" of inefficient speakers w widely varying impedance and phase angle v. frequency response, it's my understanding that a lot of that has to do w the laws of physics. You need a large driver to propagate bass energy. But large drivers tend not to work very well at higher frequencies. So in many cases you solve that w a multi-driver speaker w a crossover. If you want extended HF & LF response and have the important mid-range covered by a single unit, you end up w a 3 or 4 way design w a more complex crossover. To maximize efficiency in the bass region (which really eats up power), many designers use ported speakers. All of these elements make it difficult (not impossible) to design a full range or near full range speaker w flat impedance and modest phase angles. If you've been following other threads, you will see that there is market resistance to so-called "simple designs" at what some perceive as "high" prices. And then there is the "wow" factor of those multi-driver behemoths like the guy from "New Hampsha" hawks. Pay $10K for a near full range 2 way or $30K for a near full range single driver or pay less for a 7' tall coffin w 5, 6, or 7 drivers. You make the call. |
In the Power Paradigm the box design puts the peak at a lower frequency to take advantage of the extra energy- but again netting fairly flat frequency response, but wiht the additional benefit of bass extension, which might well be up to half an octave. Atmasphere, what does this mean? The box resonance peak is where it is. How does the Power Paradigm amplifier move that peak to a lower frequency? If the resistance in the bass region goes up (due to a box resonance) then the current into that higher resistance goes down. the voltage must go up to keep constant power. Where does the bass extension come from? A good example is an ESL, whose impedance curve is based on a capacitor. It really works a lot better if the amp makes constant power rather than constant voltage. I believe that a traditional SS amp (one that was not designed for an ESL in mind) will likely sound mediocre 'cuz of the high capacitance load that will tend to make that amp oscillate & eventually fail. OTOH, if a SS amp is designed with an ESL in mind (& a few names come to mind that are being used successfully with ESLs & planars) then these SS amps will be effective. The answer here is quite simply, such amps that can drive such loads are usually incapable of sounding like real music, as they have design features that violate human hearing/perceptual rules. I'm afraid that I do not agree with this either. Again, a few examples come to mind where amps that have been designed to tackle tough-load speakers do sound very musical. I agree that copious amounts of global negative feedback totally ruin the sonics of the amplifier. However, there are a few manuf who have figured out how to tackle hard speaker loads & yet sound musical. |
" Full range, quality high efficiency speakers tend to be big and expensive.
I think you have blame the laws of physics for that!!! "
WHo better to blame without a dispute? :^)
Of course, Atmasphere's claim that negative feedback always makes an amp not sound like music as always is highly debatable, though he certainly backs up what he says with his products by not using NF.
The consensus answer to the NF issue seems to be that the results are a function of how it is done, with global feedback being more problematic than local.
My observation from listening and reading on teh topic is that good Class D switching amps seem to have a good NF implementation that makes it a non issue in terms of sounding "like music" or more like a good tube amp. Of course, what music really "sounds like" is highly subjective anyhow, so arguing about it is probably a moot point. Each experienced audiophile knows what does or does not sound like music or not to them.
I think Atmasphere and I do agree though from past discussions that one of the best indicators that things are working well is when turning the volume up sounds good and the high volume does not call attention to itself and is best indicated mainly by its volume relative to other sounds, like people talking, etc., and a bad NF implementation would seem to work against that goal. |
IME, there is wisdom in what Ralph says about musicality and distortion. As I mentioned above, after switching output tranny taps, I think the midrange "forwardness" of my speakers has been tamed somewhat and bass seems more honest and extended.
And as far as turning up the volume, I do not detect any break-up or audible distortion. However, to be fair, when the SPL get's really high, my ears hurt. So what's the point of that exercise?? ;>')
As a point of scientific interest, I am curious how my speakers would perform if FR was measured in an anechoic chamber. But as Mapman said, and I agree with him, musicality has a significant subjective element to it.
Heck, even if my rig was ruler flat as proven in an anechoic chamber and my room didn't add any coloration, some recording are so bad, I think I'd prefer listening to pure distortion. LOL. Lately, I've been trying to get my hands on old London LPs. Many sound pretty good. OTOH, I've picked some LP dogs that are so bad, the neighborhood dogs howl. And I don't think that's because of NF or impedance peaks or negative phase angles. Some recorded music just stinks.
Great thread. I thank everyone for their terrific comments. |
HEy, look, if it weren't for fretting over how well every technical detail of one's system is working in theory compared to others, what else would one do? Listen to music and find out, maybe? |
05-09-13: Swampwalker
I'd love to hear Atmasphere and Almarg comment about how that type of amplifier's inherent electrical characteristics interacts w speaker loads. Hi Michael, I'm not especially familiar with Class D amplifiers. But in terms of output impedance they are of course firmly in the voltage source camp, with some of them having extraordinarily low output impedances/high damping factors. In terms of feedback, I don't have a particular feel for how much negative feedback most of them use, but I'd imagine that it is not insignificant in most cases. An exception would apparently be the ARC amps that have switching output stages. Those are described as using no global feedback, and are spec'd as having 1% THD. Which would seem to raise the possibility that their behavior is somewhat tube-like. Also, the Spectron writeups on their Musician III indicate that although negative feedback is used its adverse effects are claimed to be essentially eliminated as a result of the fact that transit time (aka propagation delay) through the signal path is exceptionally fast. I see no reason to doubt that claim. As I say, though, I have no particular knowledge of the degree to which feedback may be employed, and the degree to which it may be an issue sonically, with Class D in general. 05-09-13: Bombaywalla
"In the Power Paradigm the box design puts the peak at a lower frequency to take advantage of the extra energy- but again netting fairly flat frequency response, but with the additional benefit of bass extension, which might well be up to half an octave."
Atmasphere, what does this mean? The box resonance peak is where it is. How does the Power Paradigm amplifier move that peak to a lower frequency?
I believe that Ralph was referring here to speakers that are designed per power paradigm principles, not to amplifiers. One of his underlying points is that both must be designed in accordance with the same paradigm, if they are to work well with each other. 05-09-13: Bifwynne
I've picked some LP dogs that are so bad, the neighborhood dogs howl. And I don't think that's because of NF or impedance peaks or negative phase angles. Some recorded music just stinks. Truer words were never spoken :-) Best regards, -- Al |
"I've picked some LP dogs that are so bad, the neighborhood dogs howl. And I don't think that's because of NF or impedance peaks or negative phase angles. Some recorded music just stinks."
No doubt.
Personally in my audio "journey" I have been in places in the past on occasion where few recordings seemed worth listening to. Nowadays, no two sound the same, and some are still barely listenable but the vast majority sound good enough for me to enjoy, especially if one takes pleasure in the variety of sounds a recording might deliver rather than futilely attempting to make them all sound similarly good.
FWIW, I use an ARC tube pre-amp and a Bel Canto Class D amp. There is a lot to be sid about pairing a tube pre-amp with a good Class D amp, if a tube amp is not what the speakers ordered.
So my conclusion is that the devil is in the details and the details are what will swing you one way or the other, for better or for worse.
As the great scholar and musician Frank Zappa once said, "you are what you is". Very true when it comes to recordings. |
The box resonance peak is where it is. How does the Power Paradigm amplifier move that peak to a lower frequency?
If the resistance in the bass region goes up (due to a box resonance) then the current into that higher resistance goes down. the voltage must go up to keep constant power. Where does the bass extension come from? This is a matter of design. The peak exists as a relationship of the driver and the box. Change the relationship, change the peak. The bass extension comes from designing the box so the peak occurs at or below the cutoff of the driver, in such a way that the peak maintains the bandwidth. Not hard to do if you understand speaker design. I believe that a traditional SS amp (one that was not designed for an ESL in mind) will likely sound mediocre 'cuz of the high capacitance load that will tend to make that amp oscillate & eventually fail. OTOH, if a SS amp is designed with an ESL in mind (& a few names come to mind that are being used successfully with ESLs & planars) then these SS amps will be effective. Belief and reality are usually two different things. In this case I invite you to do the math. How much power will an ideal 400 watt SS amp make into 30 ohms and into 3 ohms? If you answer 'about 100 watts and about 900 watts' then you have some grasp of the problem. to be fair, when the SPL get's really high, my ears hurt. So what's the point of that exercise?? ;>') If that happens with less than 105 db, then its an indication that the system has some sort of odd ordered harmonic generation associated with its operation. A sound pressure level meter might be handy to sort out the actual volume level. |
"If that happens with less than 105 db, then its an indication that the system has some sort of odd ordered harmonic generation associated with its operation. A sound pressure level meter might be handy to sort out the actual volume level."
Maybe, but levels louder than 80-85 db (much lower) are often cited as the limits of safe listening without causing damage to ones hearing.
Even if you can go 105db, it may not be such a great idea to do so.
Maybe our hearing works a certain way with certain sensitivities for a reason?
I wonder what happens if one listens to nicely produced music, say a big band with lots of brass and high frequency energy live at 105DB? Is it as comfortable as listening to the no NF tube amp at the same level? Its a fair question, I think.
ANyway, its nice to know if one can go to 105db cleanly in any case. That's a pretty good indicator that you have the headroom needed for good results at more moderate volumes, where excessive loudness should not be an issue. |
I believe that a traditional SS amp (one that was not designed for an ESL in mind) will likely sound mediocre 'cuz of the high capacitance load that will tend to make that amp oscillate & eventually fail. OTOH, if a SS amp is designed with an ESL in mind (& a few names come to mind that are being used successfully with ESLs & planars) then these SS amps will be effective.
Belief and reality are usually two different things. In this case I invite you to do the math. How much power will an ideal 400 watt SS amp make into 30 ohms and into 3 ohms? If you answer 'about 100 watts and about 900 watts' then you have some grasp of the problem. Atmasphere, it was not clear to me what was being referred to. Al cleared that up for me - you were referring to speaker design & not amp design. I figured you were speaking of amp design given your vocation. The "I believe" part was a way of writing in the English language. Maybe I should have written "I believe it to be true....". Re. the math problem you cited, yes, I did get those values. So? The amps I'm thinking of are capable of generating these kinds of wattages & sounding musical at the same time. Indeed that's what I was thinking in the 1st place when I wrote that post..... |
Re. the math problem you cited, yes, I did get those values.
So? The amps I'm thinking of are capable of generating these kinds of wattages & sounding musical at the same time. Indeed that's what I was thinking in the 1st place when I wrote that post..... I may have misunderstood, but I think Ralph's point is that a 9 to 1 ratio of power into a load based on its impedance vs. frequency characteristics would likely result in significant frequency variation driven from this amp. He earlier mentioned the higher impedance in the bass and lower impedance in the treble for ESL's and the bass weak and bright sound of SS amps driving them. I am "inferring" what he meant and bring no real expertise to this discussion; however, I am enjoying the discussion and thank all contributors for keeping it going. |
I am "inferring" what he meant and bring no real expertise to this discussion; however, I am enjoying the discussion and thank all contributors for keeping it going. Ditto!!!! |
Often as the speakers impedance changes so does the the sensitivity, and that should correspond to flat frequency response from such a ss amp. |
I wonder what happens if one listens to nicely produced music, say a big band with lots of brass and high frequency energy live at 105DB? Is it as comfortable as listening to the no NF tube amp at the same level? Its a fair question, I think. It is. If you sit close up in a concert hall it will easily be that loud. So? The amps I'm thinking of are capable of generating these kinds of wattages & sounding musical at the same time. Indeed that's what I was thinking in the 1st place when I wrote that post..... Its rather obvious from those numbers that the amp is going to be challenged at the least, challenged in the regard that it is likely to make too much power at high frequencies and not able to make enough power at low frequencies. And in practice, that is what you hear with them as well. The feedback is supposed to help the amp with this, but because the model is incorrect (IOW the speaker's impedance curve has nothing to do with box resonance) it does not work. Often as the speakers impedance changes so does the the sensitivity, and that should correspond to flat frequency response from such a ss amp. This is true for some box speakers- those that are built with this expectation. But as we saw in the ESL example, the model falls apart. When the Voltage Paradigm was being developed (in the late 1950s and early 60s EV and Macintosh led the way on this) ESLs were not a significant part of the market (and they still aren't). So there was not and still is not a concern to make them work right. Folks, if you've not picked up on this yet, the Voltage Paradigm is all about marketing and the almighty dollar. The ability to double power as you cut impedance in half has little to do with sound quality. It has a lot to do with looking good on paper. And a lot of audiophiles buy with their eyes rather than their ears. OTOH the Power Paradigm is based on the rules of human hearing, which makes it a lot trickier to execute. The Industry wants something convenient, so you can just plug things in (easier to sell). But our ears are more complex than that. Its the conflict of these two approaches in audio that generates the equipment matching conversations, the tubes vs transistors conversations, and the objectivist/subjectivist conversations. Its really aspects of the same issue. If the Industry was open about talking about this, audiophiles could save a pile of cash and have better sound at the same time. But very little in audio occurs for the sake of better sound. Mostly its about cashing in. |
05-10-13: Atmasphere
I wonder what happens if one listens to nicely produced music, say a big band with lots of brass and high frequency energy live at 105DB? Is it as comfortable as listening to the no NF tube amp at the same level? Its a fair question, I think. It is. If you sit close up in a concert hall it will easily be that loud. I once sat in the very first row at Tanglewood for a performance by the Boston Symphony Orchestra of Prokofiev's "Romeo and Juliet." I have no doubt that peaks reached at least 115 db, perhaps even 120 db. I would have to say that it came close to the point of being uncomfortable, but for me didn't quite cross that threshold. There were a couple of times, though, that my wife briefly put her hands over her ears. I've measured the Sheffield direct-to-disk recording of that work as reaching about 103 to 105 db at my listening position. The acoustics on that recording are dry and excessively bright, though. If it had a tonal balance that is more typical of well engineered minimally mic'd orchestral recordings, I suspect I would be setting the volume control such that peaks would approach 110 db. Out of curiosity, a while back I examined the waveforms of that recording on a computer, using an audio editing program. Its dynamic range, the difference in volume between the loudest notes and the softest notes, was around 55 db! Best regards, -- Al |
But as we saw in the ESL example, the model falls apart. nah! your ESL example, I think, is a bad one. There are several SS amps manuf that have ESLs in mind & they do sound very good with ESLs. Yes, if you pair a SS amp not designed to take a high capacitative load then it will destructively fail immediately/over time. Your example assumes that one would take a SS amp not designed for high capacitative loads & pair it with an ESL & then complain about the sonics. Give both the manuf of ESL amps & the listener the benefit of doubt that they will be using an ESL amp for an ESL speaker & then compare tube vs. SS power amps for ESLs. Maybe there is another example that you could cite where the voltage paradigm fails? Thanks. |
Bombaywalla, actually that example is excellent. I have yet to hear a transistor amp that can play bass on a full range ESL, assuming the ESL is set up properly (at least 5 feet into the room). Horns are of course another example with the only exception I know of being the Avantgarde Trio, which is (or was) designed for transistors. One of the reasons horns got a reputation for being 'honky' is the fact that a crossover designed for an amplifier with a high output impedance will not work right with an amp that has a low output impedance. As a result the horn is trying to play material that is out of its passband. Full range single drivers are yet a third example. You will find that the users of such speakers are usually using a low power tube amp, usually one that has no feedback. A 4th example is the very first acoustic suspension loudspeaker ever made, the original Acoustic Research AR-1. This speaker was designed for an amplifier with a 7-ohm output impedance, and would not play bass right with most solid state amps as a result. With such amps a simple solution was to put a resister in series with the output of the amp, simulating a higher output impedance. I can also refer you to this: http://paulspeltz.com/tomcik/index.htmlThis article shows that just simply having a high damping factor does not always do the trick. Some speakers want a 10:1 damping factor, and others want 0.1:1 (and yes you read that right- such a speaker might be designed for open baffle operation). I did not make this stuff up BTW, it was well-known back in the 1950s when the industry was trying to sort out what to do about it. Tomcik, in his article above, proposed a solution that was also used by Fisher. Here is a google search on the Fisher A-80 amplifier: https://www.google.com/search?client=ubuntu&channel=fs&q=fisher+A-80+amplifier&ie=utf-8&oe=utf-8Take a look at the first hit. Its a YouTube image of a Fisher A-80 tube amp from the 1950s. Take a look at how the damping knob is labeled: "Constant Voltage" at fully counterclockwise, "Constant Power" at 12:00 and "Constant Current" at fully clockwise, where the amp is using current feedback. |
I have to agree with Bombaywalla. Some manufacturers of ESL's specifically made/make ss amps for use with their speakers, Acustat and Sanders come to mind. Many ESL manufactures use ss amps when demonstrating their speakers. I remember a particularly fine demonstration of Martin Logan's with Threshold amps. |
It does beg the question, why aren't more manufacturers making powered speakers, and why is it that people don't seem to buy them. Since the interface between speaker and amp is critical, and hopefully a designer has taken that interface into consideration in the design, it does seem logical that a powered speaker should be the best of both worlds. Ideas? |
The problem with powered speakers is it eliminates any possible flexibility of choice.The asuumption that the builder will have selected the 'best' amp-speaker match is well,an assumption. If your hearing/listening bias differs from the builder you won`t be satisfied with this 'fixed pairing' and won`t be able to tailor to your preferences.This powered speaker could measure superbly on paper yet the possibility exists you may not care for the sound regardless. |
I think Hifigeek1`brings up an excellent point! |
Why aren't more manufacturers making powered speakers, and why is it that people don't seem to buy them. Lots of reasons come to mind. Charles mentioned an important one. Let's say that a passive speaker is designed such that it will perform optimally, in a typical room, with an amplifier having a certain output impedance, a certain amount of feedback, and a certain power capability. Separate power amplifiers meeting those criteria might range in cost from say $500 to $100,000. Their size, weight, and design philosophies will vary enormously. If the speaker manufacturer were to design a speaker incorporating an amplifier meeting the impedance, feedback, and power criteria, how would he choose among all of those kinds of possibilities without greatly limiting the number of potential customers? Also, the size and weight of the speaker is likely to increase considerably. Its physical complexity and its appearance will change. WAF is likely to decrease considerably. Microphonics would have to be addressed in the design. Finally, the expertise required to design speakers is obviously very different than the expertise required to design amplifiers. As might be expected, there don't seem to a lot of high-end companies capable of, or even interested in, producing both kinds of products to a high standard. Israel Blume of Coincident being a notable exception. Regards, -- Al |
Al,
Israel Blume is one of the very few.
MBL,Gryphon and Tidal for example build power amps and speakers.The problem, some like their speakers but not necessarily the amplifiers to match them.Again, the reality of being limited to a particular voicing chosen by the builder.Al you list many other good reasons against the universal practically of powered speakers.
Regards, |
The only disadvantage I can see is a service issue. If one of that amps fails in an active speaker system you lose both the speaker and the amp vs. just one or the other in a passive system. Remember, in an active speaker system the filters for the crossover can be active. |
Another thought on the powered speaker issue (btw, I love the NHT powered speakers I use at my computer)is that they don't appeal to the tweaky gearhead side that exists in many of us that the high end market is geared (pun intended) toward. |
Powered speakers are like an albatross around your neck. If you want more power, you can't. You have to sell the amps *and* the speakers to upgrade. I have to agree with Bombaywalla. Some manufacturers of ESL's specifically made/make ss amps for use with their speakers, Acustat and Sanders come to mind. Many ESL manufactures use ss amps when demonstrating their speakers. I remember a particularly fine demonstration of Martin Logan's with Threshold amps. 'Many ESL manufacturers'. A bit cumbersome to be a real oxymoron, but nevertheless it is an oxymoronic phrase. And a bit of a red herring, there are not 'many' ESL manufacturers :)... There is more going on here than meets the eye. ML and Sanders (the Acoustat powered speaker used a tube amp) are both trying to make their speakers work better with transistors by reducing the impedance of their speakers (unfortunately, Quad has been treading this path in recent years too). To this end you encounter some very low impedances (0.5 ohms to 4 ohms) with them. However if you can get around the impedance problem (with a set of ZEROs or the old Atma-Sphere Z Music autoformer) what you find is that the tubes sound better even on those speakers. Sure, such and such a speaker might have sounded 'fine' with a transistor amp, did you then compare it with a tube amp in such a way that that the tube amp was not having a problem with the load? Just because a speaker sounded 'fine' is not the same as it sounding its best. The old Quad 57s and 63s, as well as most Sound Labs and some Acoustats, have impedance curves that vary from about 2 to 30 ohms or more. Usually if someone with such a speaker and a transistor amp claims that it makes bass, its because the speaker is too close to the wall. They are not winnowing out the performance of the speaker in that fashion. Paul Speltz, who make the ZEROs, has a letter from Steve McCormick, who makes (or made) the McCormick amplifiers like the DNA1. In the letter, Steve states that while the amp can easily double power into 4 ohms, it actually sounds better driving the 4 ohm load through the ZEROs (meaning that it is seeing 16 ohms). If you interview solid state amp manufacturers, you will find that they will pretty much agree on this point- just because they can double power into 4 ohms does not mean that they are sounding their best, and you can see that in the specs on any solid state amp- the distortion is higher as the load impedance is decreased. Essentially, if the goal is the audio *quality*, there is no argument for four ohms or less. If sound *pressure* is the goal, then 4 ohms has a weak argument. Looked at another way, a simple means of making your speaker sound smoother and more detailed is to increase its impedance, not because the speaker will work any differently, but because the amplifier will. |
It might interest you to know that the Quad 405 current dumping solid state amp which was designed for use with the Quad 57 and later the Quad 63 actually damaged the speaker because is lacked a limiter. The amp was capable of producing to much output for either speaker. A limiter add on circuit board was designed for the 405-2 to stop the damage. Ten different iterations of clamp circuit boards were designed for the Quad 63 speaker so that when the clamp engaged, it didn't blow up the amp powering it. Quad had it right with their original QuadII amps which were tube. Quads prefer voltage amps not current amps. The Quad 57 wanted to see no more than 40 Vp-p or about 25Wrms across 8 ohms. |
I don't mean to sound picayune, but I would once again call attention to the first of my posts dated 5-5-13 in this thread, dealing with terminology. IMO the terms "voltage amp" and "current amp" are incorrect and misleading.
A "voltage amp" would be one that amplifies voltage. A "current amp" would be one that amplifies current. But all or nearly all amplifiers amplify both. What is really being referred to are amps that act as voltage sources, and amps that act as current sources. But that isn't right either, in most cases, because most of the amps that are being referred to as acting as current sources only act in that manner to an extremely loose approximation.
What would be better, IMO, is to refer to amps that have negligibly small output impedance (i.e., most solid state amps) and amps having significant output impedance (i.e., most tube amps and a few solid state amps). Or, alternatively, using Atmasphere's terminology, amps conforming to the "voltage paradigm" and amps conforming to the "power paradigm."
Regards,
-- Al |
Al, that is why I came up with the 'Paradigm' part of it. In investigating this topic years ago what I found was just as you pose in your last post, that the terms are slung loosely and freely, resulting in a lot of confusion.
On top of that, I used the word 'paradigm' since a paradigm is a platform of thought, outside of which exists only blasphemy. This is why you see such staunch argument on this topic!
I also saw failure. I say this because whenever a new technology comes along, if it is really better it will supplant the prior art. In the case of audio, the Voltage Paradigm and all that it entails failed to supplant the Power Paradigm which was the only game in town before 1956 or so. The proof of that? Tubes are still in production 60 years on, audiophiles still can't tell how an amp sounds by looking at the spec sheet. The tubes/transistor debate and the objectivist/subjectivist debate have raged on the internet as long as the internet has existed.
If you look at internal combustion, the overhead valve supplanted the side valve in the early 1950s with no-one looking back except collectors. That should have happened in audio too, but it didn't, for the simple reason that the Voltage Paradigm was not in fact better. It was just different. |
05-14-13: Hifigeek1
It might interest you to know that the Quad 405 current dumping solid state amp which was designed for use with the Quad 57 and later the Quad 63 actually damaged the speaker because is lacked a limiter. The amp was capable of producing to much output for either speaker. A limiter add on circuit board was designed for the 405-2 to stop the damage. Ten different iterations of clamp circuit boards were designed for the Quad 63 speaker so that when the clamp engaged, it didn't blow up the amp powering it. Quad had it right with their original QuadII amps which were tube. Quads prefer voltage amps not current amps. The Quad 57 wanted to see no more than 40 Vp-p or about 25Wrms across 8 ohms. fwiw I used the 405-2 with the limiter with my WPK Quad 57Â’s. It sounded ok. The 405 was bettered by the Music Reference RM10 which was also designed for the Quad 57Â’s and no fear of damaging them. Sold the 405. Cheers. |
Powered speakers can be sold with separate power units chosen specifically for the task at hand, the way some speakers are sold with separate cross-overs, or have upgradeable power modules. I typically (always?) prefer systems that have speakers with low impedances rather than higher impedances. Historically speakers with lower impedances are more likely to be able to produce wave form fidelity than speakers with higher impedances. There are many good reasons for speakers to have a low impedances and the market place has proven this for a long time now. |
Unsound,
I believe the marketplace is a strong case for what's convenient and expedient but not for superior sound quality as the objective. I realize you and I are at different ends of the spectrum, but the introduction of low impedance speakers wasn't a direction chosen for improved music reproduction .These sre probably the easier design vs high impedance speakers Al and Ralph do make a more compelling argument in my opinion. I do appreciate your comments and contributions to the dialog here.Variety is the spice of life afterall.
Regards, |
I suppose everybody thinks their way is best, when in fact there always turns out to be many ways to skin the cat, including the means to superior sound quality, though personal preferences always determines what happens in the end.
Economics, convenience and ease of use are real factors for most along with superior sound. So that largely determines what is best.
Each paradigm has advantages and drawbacks. Which matters most will determine the winners.
Regarding sound quality alone, I would guess power paradigm has advantage of lower risk of bad sound up front for many, while results with voltage will be more variable case by case. However voltage scales to larger applications more cost effectively these days I would think.
Again, the game changer on the scene of late are high performance, high efficiency switching amps, that take a lot of cost and risk out of the equation for voltage amp applications. In lieu of these, I personally would be more inclined to go the current/tube amp path I think. I had strongly considered it during last major upgrade phase but decided to give Class D amps a try first, and am glad I did. |
Historically speakers with lower impedances are more likely to be able to produce wave form fidelity than speakers with higher impedances. [facepalm]I can't let that one pass[/facepalm]. Its well known for decades that the Quad ESLs have had very low distortion (re.: 'wave form fidelity'[sic]), some of the lowest out there. Yet the ESL57 and 63s both have a fairly high impedance. In fact impedance has nothing whatsoever to do with waveform fidelity in a loudspeaker. That is entirely a matter of design. There are many good reasons for speakers to have a low impedances and the market place has proven this for a long time now. The 'good reasons' are sound *pressure*, not sound *quality*. I recommend you reread my previous comments. Its one thing if I say it- I own a small company that makes tube amps. But its another thing entirely when transistor amp manufacturers say that, and especially when that is re-enforced by the distortion measurements. We are talking about distortion that is audible too. Go ask Paul Speltz to show you that letter from Steve McCormick. |
More challenging impedance loads would seem to go hand in hand with getting a more full range sound out of a smaller speaker design that will fit in well to most user's living/listening space.
For less full range applications especially in smaller rooms, there would appear to be more viable/affordable options in well designed higher impedance speakers.
However, the trend over time for most things is to become smaller and more efficient and also usually more cost effective and usable accordingly. The old paradigms have their strengths, but do not hold up well from an overall end user perspective these days. Too big, too expensive, and more maintenance required to keep things running well over time. But they can and often do sound really good. As do a lot of voltage based systems that leverage modern technology.
Its not valid to base decisions today on technology from 40 years ago. It is a different story now. THough I do love nostalgia including tubes and even Victrolas and have the Victorian styled home to potentially put these things in to prove it, the game continues to change, so one has to keep an eye on the ball! |
Mapman, I'm not sure where you are holding with SS vs tube amps. But I think it's important to restate for emphasis sake that what Al and Ralph have been trying to explain all along is IME accurate.
If you read my posts about the SS/tube amp Paradigms and varying speaker impedances, I think Al was spot on when he said that an important factor, maybe the most important factor, is a tube amp's output impedance. The lower it is, the more "SS-like" it will perform.
I posted bench test reports from Stereophile and Soundstage for the ARC Ref 150 and ARC VS-115 (my amp). I found John Atkinson's comments quite interesting. He said that the FR output performance of the Ref 150 significantly "flattened" when driving a simulated speaker load off the 4 ohm taps as compared to the 8 ohm tap. Atkinson measured the Ref 150's output impedance to be lower off the 4 ohm taps as compared to the 8 ohm taps.
That result is consistent with what AL said about tube amps having low output impedance performing somewhat "SS-like" when driving speakers that were designed and voiced to be driven by a SS amp -- like mine.
Of course the reason the Ref 150 and VS-115 have low output impedance attributes is likely because of NF, which as Ralph says introduces odd ordered harmonics. So in the end, I guess it comes down to design trade-offs, with respect to both speakers and amps.
Bottom line: My Paradigm S8s have an impedance peak of 28 ohms at 2.2K Hz, which corresponds to the midrange/tweeter x-over point. In contrast, there is an impedance "saddle" of 4 ohms at 100 Hz. Paradigm advised me that the S8s were designed and voiced to be driven by a high current/high output SS amp. Ooopps.
I always thought the S8s sounded a bit "forward" when driving them off the VS-115's 8 ohm taps. At Al's and Ralph's suggestion, I tried the 4 ohm taps. I had to get used to the change in presentation, but now I like it better. Less listener fatigue, less forward, slightly crisper bass, and so forth. My anecdotal experience is consistent with what Atkinson predicted when he bench tested the Ref 150.
Not sure what else to say. Seems to me that if one can pick up a great speaker with relatively flat impedance and phase angle plots, the issue of tube versus SS amp compatibility will be largely mooted. But based on my read of reviews on some of the "big boy" speakers out there, like Magicos and Revel Salons, you are looking at speakers that need to be driven by some monster SS amps to sound their best. But don't take my word for it. Pull some of the bench test reviews and see for yourself.
Cheers and thanks again Ralph and Al for your patience and help. |
Bifwynne,
What you relate sounds fine and does not surprise me. Whatever the details, paying attention to impedance matching between components pays off. Its a fundamental thing to get right, sometimes harder than others.
I just do not buy into the assertion that power paradigm and no negative feedback is the only way to make music sound real. It is based on sound theory perhaps, but in practice is not consistent with what I have heard in both cases over the years.
Cheers! |
I just do not buy into the assertion that power paradigm and no negative feedback is the only way to make music sound real. That's fine but it will not change the reality: The problem here is that the human ear is more sensitive to odd ordered harmonics than almost anything else. Add on top of that that the ear is most sensitive at higher frequencies (FWIW the human ear is tuned to be more sensitive to bird song frequencies, something that comes from our forebears as a survival trait); the result is we can hear odd ordered harmonic content that is hard to measure on the bench. We constantly hear how the ear is insensitive to this or that (for example we cannot detect the phase of a sine wave at all) but this is certainly an exception, and for a very good reason: the ear uses odd ordered harmonics to figure out how loud a sound is. This is vital to our survival- if you can't figure out how loud certain sounds are, you might soon be dead! The thing about negative feedback is it does two things- one thing we like, the ability to servo-control the output of the amp so it will produce flat frequency response on *certain* speakers. The other thing it does is reduce distortion overall while actually adding odd ordered harmonic distortion. When you add odd ordered harmonics even in trace amounts, it is audible because of what I have already explained. The result is it won't/can't sound real. You don't violate a fundamental human hearing perceptual rule without a price! Get rid of the feedback get rid of this problem! But now you have to sort out how to get flat frequency response and low distortion without feedback. There are ways to reduce distortion, but how do you get the flat frequency response? Use Power Paradigm design rules. Many speaker designers do this, whether consciously or not, depending a great deal on the sort of amplifier that they like to listen to. The Voltage Paradigm will work fine if you can build an amplifier that is simultaneously free of odd ordered harmonics and can also behave as a voltage source. That is the leading edge of the envelope in amplifier technology; so far no-one has been able to do it. There are some very notable amplifiers IMO that point the way- Ayre, Pass and I am also a fan of Berning, although the latter might be considered more of a hybrid approach. I suspect class D has something to offer here as well. |
Ralph,
Yes I know and you are very consistent in communicating the principles you design from and execute accordingly with your products, which I have heard sound pretty darn good.
But as I said its not the theory I have problem with, but the fact is that what I hear otherwise does not support it, and I do not think I am alone.
Its not that your way is a not a good way, I accept that it is, but the proposition that it is the only way or even the best way these days in all cases is debated. |
Ralph does have some very valid points. For example it is believed that language evolved from "bird sounds" if that makes sense(prehistoric dialect)? Children are more sensitive to higher frequencies and sounds than adults, you can claim a part of that on desensitization/acclamatization etc. But it was a very specific purpose ... survival. Females like childeren are more in tune with their senses all for survival.
Plenty of research on this on the medical aspect.
However I'm wondering if one could near completely eliminates "any" distortion, as seen a few of the newer class D, is it possible to bypass the odd order issue? |
Ralph is what makes these forums hum.{In a good way!}Thanks again for the tips,cheers,Bob |
It appears that most of us here agree the ultimate quest is sound quality. Which ever technology approach that gets you there, so be it.If someone truly believes a particular class D amplifier is equal or surpasses the sound quality of a tube amplifier with NFB absent then case closed, you've found the right amp for your needs. I've yet to experience this result and find the class D examples I've heard so far inferior in realism and natural sound.So newer technology withstanding, some older ideas and designs simply stand the test of time and at least to some listeners are the superior choice for sound quality. So it's good we rely on our ears regardless of what measurements and new technology may promise in theory. The audio marketplace caters to all the various preferences we have, choice is good. |
Charles1dad,
I infer you have directed your post to me? Either ways I'm just curious about the alternatives, since this has been a one way argument "for" the power paradigm. I would have loved to see some valid discussion from the other side.
ITs not only the class D, but there are a few SS amps out there with newer tech or resurrection of a older tech that has some semblance with tubes.
"Real music" is a relative term. Like a picture one can take and make it more real with photoshop. "Accuracy" would be an appropriate term.
Let me bring up a point - tube amps are said to have a SNR of 80-90 dB. To listen to CD (16/44) in its full resolution you need 96dB or greater. For hi rez (24/96) you need a SNR of >144 dB. Higher the resolution, bigger is the SNR value. Also you need a "system" to play the music accurately, if that's what you mean by sound quality. Of course in life there is no free lunch, and where do we trade off is the question. |
Deadlyvi,
My post was a general observation based on my own listening opportunities. I thought my last sentence made it clear where I'm coming from.What I prefer has nothing to do with your own specific listening experiences and conclusions. Some hear similar to me and others don't . We're all here just expressing our individual opinions. What ever amplifier topology suits you is fine with me. I just know what sounds better to me.
Regards, |
It's good to get the manufacturers talking like Ralph, it's like gold, to get into their design perspective and ideology. I believe we do not have such similar opportunities in any other commodities. |
Deadlvj,
I agree and wish other builders/designers would express their beliefs and ideas.This can lead to very informative discussions and of course different views and conclusions. There's no rule that demands we all have to agree on everything. Varying perspectives are good and reflects our individual experiences.
Regards, |
"I would have loved to see some valid discussion from the other side."
I think there has been some of that. ANy specific questions or subtopics of interest?
"I agree and wish other builders/designers would express their beliefs and ideas."
There is a lot of such discussion on the various A'gon threads, but Ralph is perhaps one of the more persistent contributors.
Plus Ralph's paradigm (based around avoidance of use of NF as the best means to avoid those nasty odd order harmonics + the rest seems to stem from that), FBOFW, is more unique and "radical" and a huge minority relative to the norm these days, so I think he has more work to do to gain mind share overall accordingly. He does a fine job though and I admire his tenacity in delivering on his vision!
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...plus I must add that I share the feeling expressed by many others that I do learn things of value from Ralph's posts and I thank him for that as well. |
Plus Ralph's paradigm (based around avoidance of use of NF as the best means to avoid those nasty odd order harmonics + the rest seems to stem from that), FBOFW, is more unique and "radical" and a huge minority relative to the norm these days, so I think he has more work to do to gain mind share overall accordingly. A lot of people think that this Power Paradigm thing is something of my doing. Its not. The Power Paradigm is what existed as the means of design test and measurement in the old days, pretty much everything before about 1958 or so, which EV and Mac lead the charge to move to a Voltage model. For evidence of that I direct you to Google: https://www.google.com/search?client=ubuntu&channel=fs&q=fisher+A-80+amplifier&ie=utf-8&oe=utf-8The Search is for 'Fisher A-80 amplifier'. The first hit has a YouTube image, a photo of the Damping (feedback) control on the amp. If you look at it closely, you can see the range of control goes from 'Constant Voltage' to 'Constant Power' and finally 'Constant Current'. IOW I didn't make this stuff up. FWIW it appears that there never was a current drive paradigm, although Nelson Pass has done a lot of experimentation in that area. I also found that the means of measuring output impedance has changed- the Radiotron Designer's Handbook, which dates from the early 1950s shows a very different means of doing so, with different math, than the techniques typically used today. It did take me a while to sort out why, and the why is that as an industry we went from using power measurements to voltage measurements. You can see this in the recording studio; older studio equipment is based on the power model, for example older microphones are often set up to drive 150 ohms, while modern mics are set up quite a bit differently! Another way of looking at this is output impedance- many SET designers are accustom to building amps with higher output impedances and choose speakers accordingly. This is that equipment matching conversation that all audiophiles hear about sooner or later. All I did, FWIW, was to gather these tidbits from all over and put them in the same place at the same time, and gave them a name so it would be easier to have a conversation about them. But many people have confused this with it being something I came up with, which is obviously not the case, if you look at that YouTube image. The fact that negative feedback does what it does is also not a matter of debate. It is knowledge that has been documented since the 1950s- I refer you to Norman Crowhurst, who outlined many design parameters of audio equipment in his many writings. (If we were able to build amplifiers with absolutely zero propagation delay as the signal propagates through the amp, then the feedback would work correctly with no ill effect. FWIW, most amplifier design theory that involves feedback actually assumes that this is the case. Unfortunately the real world does have have such examples, and being pragmatic, I figure since that is the case maybe we should look elsewhere for fidelity, since the feedback model clearly fails.) I persist in this is only because I want to forward the art. I don't see any amplifier technology as having the answers, all amplifiers have weaknesses and tradeoffs. I am simply pointing to What Is; what you want to do with the resulting knowledge is another matter. Now Mapman tries to make it look like I might be tilting at windmills; the evidence that I am not is very simple: If the Voltage Paradigm really worked, there would **be no vacuum tube industry**. Its really that simple. But here we are, over half a century after tubes were declared obsolete, and tubes are still being made (they are the easiest way to create an amplifier on the Power model). FWIW normally how it works is when a superior technology replaces the prior art, the prior art dies out. How many of you still use a rotary dial on your phone? |
Atmasphere,
For the record, I never said you made this stuff up.
I would say you are its most vocal champion these days, at least in these parts.
Just making an observation. You offer a way that works and these days at least is different than most. Plus you are willing to spend time talking about it and educating others in the process. Kudos to you for all that!
On of the pivot points of the argument would seem to revolve around how how well a good local NF implementation implementation in a SS amp these days can work in comparison. That is something I have seen discussed here as well by some who are quite knowledgeable about NF and SS amp design, but I would like to learn more.
Meanwhile, I have to trust my ears, which largely thanks to you are tuning in more and more these days for those nasty odd harmonic side effects of NF. My ears tell me that use of NF these days does not necessarily have to be the road to audiophile hell, as perhaps it can be and has been perhaps in the past.
ISn't there a threshold below which all kinds of distortions become insignificant? Pick your distortion, all amps have them. The goal is to make them as unoffensive as possible.
Odd order harmonics from NF might be quite nasty relative to others as suggested, but that does not mean there is no way to get the negative effects into a range that is not significant, at least for most. No amp is perfect, I think we would agree on that?
But I am not convinced distortions from NF is such a pox on good sound necessarily these days as perhaps it was in the past. Seems like a curable disease to me, but I have no data to support that, only a gut feel from what I read and hear, only what my ears are telling tell me after years of listening.
Time will tell. WHat technologies will dominate 20 years from now I wonder? How will they sound compared to today?
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