More than a few people over the years on these pages have said only those SS amps which double down in output power as impedance drops are truly special or worthy amps. Eg., 200 @ 8ohms; 400 @ 4 ohms; 800 @ 2 ohms; etc.
Not every SS amp made does this trick. Some very expensive ones don’t quite get to twice their 8 ohm rated power when impedance halves to four ohms. BAT, darTZeel, Wells, and Ypsalon to name just a few.
An amps ‘‘soul’’ or it’s ‘voice’ is the main reason why I would opt in on choosing an amp initially and keeping it. Simultaneously , I’d consider its power and the demands of what ever speakers may be intended to be run with it or them.
I’ve heard, 80% of the music we are listening to is made in the first 20wpc! I’m sure there’s some wisdom in there somewhere as many SS amps running AB, are biased to class A Only for a small portion of the total output EX. 10 – 60 wpc of 150 or 250 wpc.
After all, any amps true output levels are a complete mystery when anyone is listening to music anyhow.
I suspect, not being able to actually measure true power consumption, the vast majority of listening sessions revolve around 60wpc or so being at hand with traditional modern reasonably efficient speakers.
Sure, there are those speakers which don’t fit into the traditional loudspeaker power needs mold such as panels or electrostats, and this ain’t about them.
The possibility of clipping a driver is about the only facet in amp to speaker matching which gives a person pause while pondering this or that amplifier.
I feel there is more to how good an amp is than its ability tou double output power with 50% drops in speaker impedance.
However, speakers are demanding more power lately. Many are coming out of the gates with 4 ohm ‘nominal’ IMPs which lower with fluctuations in frequency. Add in larger motors on larger drivers, multiple driver arrays, and on paper these SOTA speakers appear to need more power.
IMHO It is this note which introduces great concern.
I’ve read every article I can find on Vienna Acoustics Music. Each one says give them lots of watts for them to excel.
Many times good sounding speakers I’ve owned sounded better with more power, albeit from arguably a better amp.
I tend to believe having more than an adequate amount of cap power is indeed integral. … naturally the size and type of transformers in play possess a strong vote for an amps ability to successfully mate with speakers.
Controlling a driver’s ability to stop and restart is as well a key to great sound and only strong amplifiers can manage this feat. Usually this gets attributed to ‘damping’ factor, but damping as I read it is more a shadow than a tangible real world figure as it depends on numerous factors. Speaker cable length alone can alter damping factors.
A very good argument exists about those mega watt amps voices. Each 500 or 600 wpc amp or amps, I’ve heard have had stellar voices too, not merely more watts.
So is it predominately these mega watt power house amps souls or their capacities that fuels the speakers presentation?
Would you buy an ‘uber expensive’ amp based more on its voice or soul, than on its ability to output loads of watts, even if you feel the amp may be somewhat under powered for the application?
Choosing this latter option also saves one money as the more powerful amps do cost more than their lower outputting siblings.
Blindjim > yep. They do be ‘spensive. It’s a matter of taste… faith… trust.
Loudspeaker designers could fix all of this by focusing on building more efficient easier loads and without stonewall x overs. The only prevailing scheme for making speakers easier loads are those which have chosen to support their own bass drivers with amps thus offering a hybrid solution. Fine by me..
Its gonna be interesting. = = = = = = = = = =
@Gryphon Audio > The Gryphon Kodo has active bass cabinets with a dedicated 2000 watt amplifier
Blindjim > many thanks. Sorry. I simply forgot about that aspect of the Kodo’s build. Regardless, they are quite the impressive loudspeaker. = = = = = = = = = = = =
Yep. I’ll use a scale and hang my hat on their sonics, then see how it all shakes out. Buy something and play it or them until they dry up, fall apart and eventually disintegrate.
One last note here….
I’ve said in all honesty each mega watt amp or amps I’ve ever heard provided very good to outstanding sonics. Each varied slightly of course, but all were easily keeper arounders for long term.
If its true the best sound is developed in the first watt, portions there of, and a bit thereafter, ala SET amps, why then do these giant amps have such an inviting enjoyable sound while having the where with all to push out 400 – 600wpc @ 8 ohms?
Sure, during any sane listenting sessions it or they are not kicking out welder like current into the speakers. Instead, supplying the same amount more modest amps would deliver to the speakers.
So is it their over built construction that is providing the more sailient voice? The fact these immense power houses are merely loafing along and under no duress?
IMO? I’ll throw a dart at build, once more, or rather, over build.
@kosst_amojan . design a speaker that sounds good, not treats the amp kindly. A competent amp deals with it.
Blindjim > I have no argument for that what so ever. Wisdom filled words. Thank you. However, it doesn’t seem to resolve the question presented herein.
Unreproachable built amps with solid power resources seems the solution, although the exact output or capacity of the amp and how one determines it beforehand with respect to any speaker remains elusive.
Naively I thought out there somewhere was a formula, theory, or practice apart from practical past experiences which would satisfy it. It looks like there is none. = = = = = = = = @atmasphere > @blindjim that description really sounds like the amp clipping- all bets are off at that point.
OK. lets be clear on what clipping actually is for a change. I thought it was an insufficient supply of power to a drivers demands or desires to produce a set of frequencies at a particular volume level.. Or IOW, a driver being starved of necessary voltage.
EX. Sony HT receiver w/120wpc + BW 9s, and later BW 802s. replacing the sony amp with a Krell KaV 250 no fuzziness or softness was perceived..
EX 2 Jamo R909s with BC 500 mono blocks.
I can’t help but feel after the upgrade in EX 1, and the Jamo + BC 500 amps, clipping was not an issue. Please, correct me if I’m flatly wrong.
@atmasphere > are you nutz even suggesting any of your amps would compete with the Gryphon I mentioned on a speaker such as the Wilson Alexia, or others even with similar hard varying loads.
Blindjim > huh? Sorry Ralph, but You obviously have my remarks confused with someone else’. I never alluded to anything remotely disparaging regarding Gryphon amps. Nor did I make any reference to Wilson speakers.
Check your reference… you must have meant someone else yet did not include their handle to indicate your words were directed to them.. = = = = = =
What about McIntosh amps? With their autoformer, weather you use either the 8 ohms, 4 ohms, or the 2 ohms tap you get the same power. So why have three taps when each taps produce the same wattage?
Mike, as I understand it the rationale for the use of autoformers in McIntosh solid state amps is to enable the output stage of the amp to "see" a higher load impedance when driving low impedance speakers. Specifically, to "see" the same load impedance when a 2 ohm load is connected to the 2 ohm tap as when a 4 ohm load is connected to the 4 ohm tap, and as when an 8 ohm load is connected to the 8 ohm tap. Thereby making life easier for the output stage (i.e., improving its performance) when the amp is required to drive low impedances. Of course, that benefit will trade off against whatever sonic downsides may be introduced by the autoformer itself.
Most tube amps are the equivalent of a graphic equalizer - hence a no no for me.
If the amp employs about 20 db of loop feedback, it is capable of acting as a true voltage source, whether it can double power into half the impedance or not. IOW, it can be within 0.5db if there are no limitations in the bandwidth of the output transformer. The trick is not to look at things at full power, but to observe what is going on at 1/10th full power, where most of the amplifier power is likely spent. At those power levels you will see any voltage source acting like any other voltage source, doubling power when it needs to or cutting it in half when it needs to.
Most of the time the coloration that people really complain about in a tube amp is the 2nd harmonic, which adds richness. Solid state amps usually lack this on account of being fully differential. Its possible to build a tube amp fully balanced and differential as well, and if so built they too will lack even ordered harmonics as they are canceled throughout the circuit, not just in the load.
However there is a price that solid state exacts of its owners- they too have coloration, only in this case it is higher ordered harmonics. They are certainly at a low level, but the human ear/brain system uses higher ordered harmonics to sense sound pressure (likely because pure sine waves are non-existent in nature and so are not part of our evolution) ; as a result humans are very sensitive to higher ordered harmonics and can hear them easily. The audiophile terms for this are 'bright', 'harsh' and similar turns. This explains why two amps can have similar bandwidth within 0.5db yet one might sound bright and the other not. IOW we respond to distortion by perceiving it as a tonal coloration.
This simple fact is why tubes are still around decades on after being declared obsolete. If you can eliminate the oppressive nature of the top end in a system, then the system might get more listening time.
IOW the real reason behind the tube/transistor ad nausem is all about distortion.
Check your reference… you must have meant someone else yet did not
include their handle to indicate your words were directed to them.. R
@blindjim , my remarks were quoting George from the other thread by the same name in the amps section.
@atmasphere Thanks. I sort of thought so but wasn’t sure.
I’m reading thru amp measurements done here and there, and often the terms get conveyed as ‘db’ losses or gains of voltage, I suspect. When the DB comes up, I am lost.
Anyone point me to how voltage or current is converted to db with a link or simple explanation? I feel I’m missing something the person measuring the amp is saying.
This is why I buy McIntosh Double or Quad balanced design. The Mac autoformer takes care that the amp drives the rated output across all loads 2,4,8, without raising distortion! (which these other brands dont do) This gives the Mac a very non fatiguing sound especially when listening loudly for long periods. So much so is this true that the Grateful Dead used Mac amps in all live performances because they loved this type of sound and shared it with all their fans. Did I mention they never break either...and last forever! Woodstock spread beautiful music throughout Max Yeagers farm using McIntosh amps! These amps were abused and yet they rocked the hell out of that place.
Go ahead and spend gobs of money on those pure class A amps that burnout after 7-10 years...not me.
Kosst_Amojan 12-14-2017
It's called impedance matching. The closer a load matches the impedance
of the source, the more efficient the energy transfer. Generally you
want the load to be at least twice the impedance of the source to avoid
odd coupling effects. The ratio of impedance difference also defines the
damping factor which can significantly effect speaker behavior.
Kosst & Miketuason,
The following statement appears in the manual for the McIntosh MC601 that is listed in Mike's system description. I believe similar statements appear in the documentation of other McIntosh solid state amplifiers which use autoformers. And this is what I was alluding to in my previous post, although I referred to performance benefits rather than benefits to long-term reliability. (Kudos to Mattmiller for citing both benefits):
All solid state power amplifier output circuits work best into what is called an optimum load. This optimum load may vary considerably from what a loudspeaker requires. In the case of more than one loudspeaker connected in parallel, the load to the power amplifier may drop to two ohms or even less. A power amplifier connected to a load that is lower than optimum, causes more output current to flow, which results in extra heat being generated in the power output stage. This increase in temperature will result in a reduced life expectancy for the amplifier.
The special Balanced Winding Autoformer creates an ideal match between the power amplifier output stage and the loudspeaker.
Also, regarding the comment about damping factor, the MC601 has a specified damping factor of "greater than 40," which presumably means effective output impedances of the 8, 4, and 2 ohm taps of approximately 0.2 ohms, 0.1 ohms, and 0.05 ohms respectively, all of which of course are very small fractions of the impedance of most speakers. Which in turn reinforces the notion that the multiple taps are provided mainly to benefit the amplifier's output stage, as opposed to optimizing interactions with the speaker, such as impedance interactions, bass damping, and energy transfer.
I’m reading thru amp measurements done here and there, and often the
terms get conveyed as ‘db’ losses or gains of voltage, I suspect. When
the DB comes up, I am lost.
@blindjim Decibels are a logarithmic expression. They are handy because our ears are logarithmic as well. Voltages and audio equipment in general are linear expressions, so sometimes conversion is needed.
1 decibel is the least difference the ear can detect. 3 db is a minimum easiest change in volume that we hear. +3db requires twice as much power, -3db is half the power 6 db is a doubling of voltage, not power. This can be a bit confusing! 10 db is what we perceive as 'twice as loud' and requires 10X more power 20 db is 100x more power. 30db is 1000x more power.
In amplifiers there is something known as 'golden decibels', an expression that comes from the radio broadcast industry. 3 db represents a doubling of power, and to hear any significant increase in volume you need 3 db, so this gets increasingly expensive and in amps, the more power the less likely it will sound like music. This is why speaker efficiency is so important.
This gives the Mac a very non fatiguing sound especially when listening loudly for long periods.
That's because they sound like a big fat sponge, no life, no dynamic contrast, that's why they're not much of a hit amongst audiophiles, but the "glitz queens" love them.
The Mac autoformer takes care that the amp drives the rated output across all loads 2,4,8, without raising distortion! (which these other brands dont do)
This reeks of MacItosh proper-gander "Good designed" solid state amps are designed so the output transistors are used in their most linear part of their curve.
You said earlier, there are a lot of amps that will work for you.
I agree. Finding the exact right one is the issue. Or exact right 3 for that matter. Or even finding the exact wrong ones helps too.
I think, knowing no better, it would be an easier task were more speakers 8 ohm impedance.
RE speaker eff I often see sensitivity and impedance figures noted by makers on their speakers. Now, I’ve been reading where possible, measurements are made on which ever unit, and am often lost once more until the final analysis commentary arrives indicating if the tester felt positive or not about what all they saw from this or that model.
Although, I don’t routinely see an item declared as speaker efficiency, per se.
Is this a product of some other factors or measurements? Or is efficiency another term for sensitivity?
I’m thinking this is more involved than that somehow.
Strictly speaking, speaker efficiency would be the ratio of acoustic power out to electrical power in.
However, it is common practice for the term "efficiency" to be used to refer to the sound pressure level (SPL) that would be produced at a distance of 1 meter in response to an input of 1 watt.
It is also common practice for the term "sensitivity" to be used to refer to the SPL that would be produced at a distance of 1 meter in response to an input of 2.83 volts.
2.83 volts into 8 ohms corresponds to 1 watt. (2.83 squared/8 = 1). So for an 8 ohm speaker, that is truly 8 ohms, sensitivity and efficiency are equal.
2.83 volts into 4 ohms, though, corresponds to 2 watts (2.83 squared/4 = 2), which is 3 db more than 1 watt. So the efficiency of a 4 ohm speaker would be 3 db less than its sensitivity, assuming those terms are used in their most usual sense.
Also, keep in mind that as can be seen in measurements provided by John Atkinson in Stereophile, and measurements that are provided in reviews at SoundStage.com and elsewhere, manufacturer sensitivity and efficiency specs are often overstated by a few db. In some cases, I believe, because the manufacturer’s rating may be based on a single frequency, rather than an average across a wide range of frequencies.
When it comes to the perfect amp, Ralphs OTL Atamsphere’s are it.
But, and it’s a big BUT, you need the perfect speaker. One that is efficient, has a nice even resistive high impedance load across the frequency range, with virtually zero phase shift also across the frequency range. And Autoformers such as the Zero are a bandaid fix to get it, as they create other evils instead, similar to the Mac autoformers.
Full range speakers and horn speakers ("maybe Magie’s"??) are possible to have these 4 attributes, but are severely compromised in too many other areas, eg: colouration’s and distortions. Good luck finding any without these compromises.
kosst_amojan " Wouldn't it be nice if speakers makers provided electrical characteristics so you could make a better choice about amps? "
Of course many do provide the relevant specifications, performance limits, and technical particulars of there speakers and of those who do not you could inquire and of those who do not you can conduct you're own measurements or even listen for your self?
kosst_amojan " I've NEVER seen a speaker company provide charts of impedance magnitude or phase angle. I've never even heard of one providing that information upon request. I'm not exactly sure how you would listen for those specifications. I'm not sure buying thousands of dollars worth of test gear and constructing an anechoic chamber so that I can measure a few speakers once or twice a decade makes a lot of sense. " I am very surprised to here you state this because you have carved for yourself a staunch position of demanding from people here who are just hobbyists rigid scientific analysis for their opinions and yet with actual manufacturers of components comprised in a Music Reproduction System you've NEVER even heard of anyone asking for the data that you seek and then you state you can't be bothered to purchase test equipment!
I've NEVER seen a speaker company provide charts of impedance magnitude or phase angle.
You couldn't trust them anyway, only independent testers like Stereophile and the Miller Audio Research Company (you have to join), give you "unbiased test reports" For advertising propaganda some amp manufacturers deliberate understate the 8ohm wattage so the 4ohm looks to be doubling, you can catch them out with Stereophiles real tests, which shows far higher 8ohm and then the 4ohm guess what? it doesn't double.
finally I’m able to comprehend fairly well what you said. Almost.
I feel I was already on board with your preliminaries. XDB @ 1w, or XDB at 2.83v.
As for that -3db item regarding 4 ohm impedance speakers, is this attribute a constant with respect to power across the bandwidth?
IN other words, with a 4 ohm IMP whatever speaker will it always be 3db down in SPL at what ever rated amplifier output that it would be if an 8 ohm load was present?
I got the impression making a speaker IMP 4 ohms incidentally obtained automatically about a 2 – 3db gain in response or sensitivity.
Another item has my attention with respect to amplifiers. Gain.
Actually, matching pre amps (lines, DAC, etc) with what ever amplifier. Each amp, has its own amount of gain.
Regularly we see here and elsewhere, output to input IMP should have 1 to 10 ratios. 1K out IMP needs a 10K input or better.
Is there as well a general rule of thumb for preamp gain and amplifier gain one should keep in mind irrespective of the load when choosing a preamp & power amplifier match?EX. Keep the line stage gain at 25% of the power amp rated gain. Keep the line stage gain at 50% of the power amp rated gain. Keep the line stage gain at 75% of the power amp rated gain.
Or this relationship is not how or where to look best for synergistic or electrical matching purposes?
Best regards… = = = = = =
RE – testing and verifying speaker or amplifier specs I suppose one avenue is to look towards amplifier & loudspeaker makers individual reps.
Some speaker makers are decidedly making their units aimed squarely at lower powered amps like SET. More than a fair number of monitors stay in a more ‘easy’ range many amps will like to see too.
The rest whose EFF or as they rate them in IMP at 4 ohms or lower, despite their rated sensitivities, are probably saying use decent amplification here. As a fair number of maker spec sheets often include minimum power ratings for their units. Albeit, the speaker makers seldom if ever indicate what listening levels one will derive using an amp outputting their minimum recommended wattage.
Apart from first hand evals a good reviewer will drive what ever speaker with several amps for comparisons sake and detail those desparities in their accounts.
Then too, some are mighty vague saying only “these speakers enjoy power”. Or ABC speakers worked best with a lot of power or a powerful amp. This leads one to believe they MUST employ a substantial power plant and no less, if that speaker is picked for a system.
Of course, one can deny the accounts and reviewer’s reviews as mere advertising and as such all bets are off regarding probative value or integrity contained within the account.
At some point however, we gotta believe someone somewhere on something.
The vast majority of people neither have the inclination, training, or resources to get uot there and test everything, everywhere, everytime. Nor would many want to.
It isn’t wrong to expect device makers demonstrate good faith in the specs they claim either. It does seem a bit naïve to lean more than lightly onto them of late.
As for that -3db item regarding 4 ohm impedance speakers, is this attribute a constant with respect to power across the bandwidth?
IN other words, with a 4 ohm IMP whatever speaker will it always be 3db down in SPL at what ever rated amplifier output that it would be if an 8 ohm load was present?
I got the impression making a speaker IMP 4 ohms incidentally obtained automatically about a 2 – 3db gain in response or sensitivity.
If a 4 ohm speaker is rated to produce the same SPL at 1 meter as an 8 ohm speaker, and both ratings are specified on the basis of an input of 2.83 volts (rather than 1 watt), and the SPL and impedance ratings are accurate, the 4 ohm speaker will require twice as many watts (i.e., 3 db more power) to produce the same volume as the 8 ohm speaker, at a given distance and at all frequencies for which those ratings are accurate.
But also keep in mind that most solid state amplifiers can deliver significantly more power into 4 ohms than into 8 ohms, and in some cases twice as much.
Regularly we see here and elsewhere, output to input IMP should have 1 to 10 ratios. 1K out IMP needs a 10K input or better.
Although that guideline is commonly stated, as you indicated, it’s not that simple. See my post dated 10-3-2016 in the following thread:
Is there as well a general rule of thumb for preamp gain and amplifier gain one should keep in mind irrespective of the load when choosing a preamp & power amplifier match?
Power amp gains generally tend to be in the area of 25 to 30 db or so, although some are significantly higher and some are significantly lower. The gains of active line stage preamps in recent decades generally tend to be in the area of 6 to 15 db or so, although some are considerably higher, and at least a few are somewhat lower. Differences in gain will affect what settings of the volume control will be used, but of course won’t affect the maximum amount of power that can be delivered to the speakers. Volume control positions will also be affected by speaker sensitivity and the output level of the source components. If any of these four factors is considerably higher or lower than usual attention should be given to the possibility that the volume control may have to be used too close to the bottom of its range, or at the other extreme that it might even run out of range at the top with some recordings.
It's useless to talk about 4ohm speaker and 8ohm speaker, as none are flat at that impedance across the audio band, they are very different. And the best way to treat it is to look at the lowest impedance and - phase angle and base an amp around that.
1: There can be dips in the impedance curve at certain frequencies that can be very low. 2:There are also negative phase angles at certain frequencies that can be very high.
Combine the one and two at certain frequencies and you have almost a short as seen by the amplifier "usually" in the bass.
EG: Wilson Alexia is spec'ed by Wilson at 90db and 4ohm
Independent test measured: I in the power region of the bass between 60hz and 110hz approx it has a nominal impedance of just 1.9ohms!, combine this with the negative phase angle of around -45 degrees and you have an EPDR (equivalent peak dissipation resistance) that the amp sees as just .9ohm!!!!!
So much for being designated as a "4ohm speaker"!!! And the Sofia 3 is even worse than this.
The conclusion is that good engineering demands speakers that are easy to drive and amplifiers that retain a flat frequency response under varying loads. Combine such units, and you are fine. Combine hard to drive speakers with most tube amps and you have a response that is all over the place.
good engineering demands speakers that are easy to drive
This would be great, maybe in the future with different construction techniques, motor design, materials ect, but for now easy to drive speakers usually have other permanent compromises, that can’t be fixed driven by the right amp. At least the expensive hard to drive speakers are just that because they present no compromises except one, being asked to be driven with amps that can drive them with the current that's needed.
Thanks Al. = = = = = = More than interesting. Thanks George.
Do you know if the Sabrinas and later model Sash’s have similar IMP traces as the Wilson’s you just mentioned here?
I’m hearing from this person and that, they have listend to the Sabrina and Sasha with very modest power amps, even < 100 wpc., tube amps and really enjoyed what they heard.
BTW, Does that third party measuring facility come with any verifiable credentials? What’s the annual subscription run? Do they cover as much as Stereophile, or more?
Again, I do appreciate the input and all the effort.
Do you know if the Sabrinas and later model Sash’s have similar IMP traces as the Wilson’s you just mentioned here?
Both are hard to drive, not quite as bad as the Alexia, but both to sound at their very best in the bass would need an amp with good amount of current ability.
I’m hearing from this person and that, they have listend to the Sabrina and Sasha with very modest power amps, even < 100 wpc., tube amps and really enjoyed what they heard.
Yes it would sound good, I'm not saying it wouldn't. But he's not hearing them at their best with an amp with a bit of current. for the load they represent in the bass, that would make most tube behave like an equaliser (tone control).
Hey @kosst_amojan Interesting point about speaker requirements. Is there some speaker performance or design spec that signals when a voltage vs a current source is preferable? How about with amps...is there a way to identify current vs voltage delivery designs? Any power amp is going to deliver both volts and amps; how does one recognize the type? Is it by the ratio of V to A? Where is the dividing line?
A theoretically ideal voltage source has an output impedance of zero, and a theoretically ideal current source as an output impedance that is infinite.
Neither exists in practice, of course. However most (but not all) solid state amps have an effective output impedance that is low enough in relation to speaker impedance to enable them to be considered as voltage sources for practical purposes. Provided, of course, that they are operated within the limits of their maximum voltage, current, power, and thermal capabilities.
On the other hand, tube amps have output impedances that are usually significant in relation to speaker impedances, and also tend to differ widely among different designs. Consequently tube amps fall at various points on a continuum between ideal voltage source and ideal current source.
An ideal voltage source will maintain an output voltage that is constant as a function of load impedance (again, as long as it is operated within its maximum voltage, current, power, and thermal capabilities). Per Ohm’s Law, if the load impedance is purely resistive the current that is supplied will equal that output voltage divided by the load resistance. It gets more complicated when the load has a significant inductive or capacitive component.
An ideal current source will maintain an output current that is constant as a function of load impedance, and per Ohm’s Law the voltage it will supply into a purely resistive load will equal that current multiplied by the resistance, as long as it is operated within its maximum capabilities. And again, it gets more complicated when the load has a significant inductive or capacitive component.
Is there some speaker performance or design spec that signals when a voltage vs a current source is preferable?
If the impedance of the speaker is relatively high, and does not vary greatly in magnitude over the frequency range, and does not have phase angles that are severely capacitive (i.e., extremely negative) at any frequency (especially at frequencies at which the impedance magnitude is low), and has medium to high sensitivity, chances are it would be suitable for use with either type of amplification.
To the extent that those criteria are not met, as Ralph (Atmasphere) has said in the past it can often be helpful to try to determine the intentions of the designer. For example, it can be inferred that a small two-way speaker having an impedance in the vicinity of 4 ohms in the bass region and 8 ohms at higher frequencies is probably intended for use with solid state amplification, which will augment the bass by delivering more current and power at bass frequencies than at higher frequencies, for a given output voltage. While the classic Quad ESL-57 electrostatic speaker was designed before solid state amplification existed, so it can be presumed to be suitable for use with tube amplification even though its impedance varies widely over the frequency range and is highly capacitive.
Al - Yet again, THANK YOU for another well written and accessible explanation. Much appreciated. I'm gaining ever greater appreciation for John Atkinson's measurements in the Stereophile speaker reviews (especially his Impedance & Phase vs Frequency graphs).
The more I’ve dug into amp designs and uses the less important watts seem to be.
Correct, you just have to listen to a pair old well serviced huge Class-A Mark Levinson ML-2 monoblocks, these were only 25w!!!! into 8ohms, yet could almost double that wattage all the way down to 1ohm, which meant bags of current. These are one of the most magnificent amps you will ever hear.
Nothing could touch them on a pair of ESL57’s, and they could drive anything, even the .9ohm Wilson Alexia’s maginficently, just not party levels, remember they are still only 25w.
The good watts are pretty much always the clean ones
Correct, you need good watts, but also good current to back them up, otherwise you end up with a "tone control" instead a of an amp that trys to remain dead flat into varying impedance's.
However, transformers do have drawbacks. Many speakers don't expect the
low damping factor transformers provide and they drive a lot of speaker
hot in the highs. There's a reason DC coupling is the standard in solid
state amps. It gives the output stage maximum control over the load.
We direct-couple our amps and they are vacuum-tube. An output transformer does not mean that you get a low damping factor. Its far more complicated than that!
Tube amps, including OTLs, can operate at voltage sources much like solid state. It all depends on the design and intention.
The thing is, with tube amps you get linearity, but usually not a low output impedance. So you add loop feedback and then you have the low output impedance. With solid state, you don't (usually) get linearity but you usually have a low output impedance. So you add loop feedback to obtain linearity.
The problem is that loop feedback, while suppressing distortion, adds some of its own in the process (this fact has been known for decades- see the writings of Norman Crowhurst). Some of it is IM distortion (which is highly audible) and some is higher ordered harmonic distortion (which is also audible). This is why amps with feedback tend to sound brighter (and also harsher) than amps without.
To this end, loop negative feedback is eschewed by many designers as they don't want coloration. Contrary to what has been stated elsewhere on this thread, its possible to design a speaker for an amplifier that has a higher output impedance (which it will have if it has no feedback). Such a speaker does not have to have a flat impedance curve either! Its also possible to find speakers that will obtain flat frequency response even though the amp has a high output impedance, despite the fact that the speaker was not designed for such an amp.
Its easy to see in the specs of the speaker when it will work with amps of higher output impedance. We've stayed in business for over 40 years doing just that. But there are also speakers that are designed with this expectation- Audiokinesis, Coincident Technology, Merlin, Altec, JBL, Tannoy...and many more. Intention also plays a big role.
So there is more than one way to obtain flat frequency response. The thing is, higher ordered harmonics are very audible to the human ear as the ear/brain system uses them to sense sound pressure. So if the system has more higher ordered harmonics than it should, it will sound bright and harsh despite the actual distortion being quite low. This is why amps with a high output impedance exist; its not because somehow we designers can't make them low impedance- we can! - its because we are trying avoid not just some colorations but **all** colorations, and a higher output impedance is a result of that. But no worries- if you want accurate reproduction that sounds like real music, look at it this way:
If the speaker requires that the amp employ feedback to sound right (regardless of why the amp has the feedback), **with today's technology** that speaker can't ever sound like real music- it might sound like a really good stereo, but it won't have the feeling of real music.
slfoth I think it is important to distinguish between good "performance" versus just "sounding good".
Carefully matching amp and speakers along the lines you spoke of is key to getting good performance, which can be measured. Good performance matters a lot but alone does not mean one will like the sound or even that it sounds better. But you cannot accurately reproduce all forms of music similar to the original without it.
Good sound is totally subjective and is a judgement call. Good performance is not required. It may sound lovely in some cases to some people but cannot compete with good performance any more than a nice driving Toyota Camry (very nice car!) can compete with a state of the art luxury vehicle.
My recommended strategy is get the good performance first using specifications to match components (as opposed to pure luck or just hope) then tweak from there as needed to get the sound just right.
Its not a black and white thing. There is a match between a low power SET amp and high impedance high sensitivity speakers (optimized performance) as well as a match between high power high current SS amps and smaller and harder to drive, lower efficiency speakers still with good bass extension. There is also everything in between (less optimal at least on paper). Both done right should perform fairly optimally though each will still likely sound different for various reasons and the choice will come down more to personal preference based on a myriad of factors in the end.
Of course one can always just choose to roll the dice and pick each component you like for whatever reason. Most any amp and speakers are "compatible" to the extent that you can connect the two with no issue and hear what you got. You might get lucky but chances are if you want it all then it will take much longer to get anywhere near that goal than otherwise.
Stfoth, as Mapman indicated the net result of the myriad factors and tradeoffs that are involved in a middle ground situation such as you've described will come down to a combination of the specific designs and listener preference. And chances are that a multitude of different approaches will work well for many listeners, as we often see here.
A good understanding of those factors and tradeoffs can reduce the randomness of the selection process, and the risks of wasted time and expensive mistakes, but in the end, as the saying goes, the proof of the pudding is in the eating. Or in this case, the listening.
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