Which watts are the right watts in SS amps?

I know about one solution, curious about other.
Hypex Ncore500 are rated 100 watt continuous with the thermal limit of 200 watt.
Peak power is 700 watt into 4 ohms.The peaks can be fairly long, measured in seconds, the limits are thermal.  Some Hypex UCD units go up to hundreds of watt continuous. Those have big radiators both on power supplies and amp modules.

I am curious about the peak/transient power approach to the topic. Apparently
peaks/transients can demand 5-7 times the power of continuous (RMS?) power demands. Hence if an amp is capable of  100 wpc continuous delivery it should muster 700 wpc for those short-time events. How is this realized in practice?
Which amplifiers are built to this spec and how?

First 5 – 7%? I’ll presume this initial area pertains directly to the scenario you presented, otherwise, isn’t the first 10 – 20% of a class AB amp where one finds Class A functionality, and many adore that area of operation.

@blindjim  Well they do say its all about that 1st watt, but in the case of less efficient speakers it might be about the first 5 watts in the case of some behemoth amps.

(If you've ever heard the maxim that lower powered amps tend to sound better, this is one of the reasons why. IMO, there are some fairly musical low- and mid-powered solid state amps, but there aren't any that are really high powered. As for tube amps, there are very few high powered amps that sound like real music either!)

Class A is helpful for reducing distortion. Most AB solid state amps go from class A to AB within the first watt or so. But even class D amps which operate on a different principle (as well as many push-pull tube amps) have this quality of increased distortion at lower power levels. So even if they were all perfect voltage sources, you would still want to match the efficiency and power handling of the speaker against the low power distortion issues of the amp.

For this reason, I suspect our grandchildren will still be talking about equipment matching- we're not seeming to be solving this issue anytime soon.

Imhififan > Wolcott.

Blindjim > Thanks. Nice thoughts.
I thought they quit making these amps. I looked hard at it many years ago as a choice. I think then however, the cost was out of reach very likely as they seldom if ever appear on the used pages for sale.
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@stfoth > I often tell them not to overthink it and just order a decent Champagne, especially on a date or in a group. 95% idiot-proof.

Blindjim > thanks much. I tend to agree. I suspect this should be the ‘default’ answer for anyone who is either in doubt as to which way to upgrade, update, or just start a first audio build in terms of which amp to go with, keeping budgetary considerations in mind.
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@atmasphere > all amplifiers that are capable of acting as a voltage source are push-pull, and such amps (with rare exception) have distortion characteristics wherein the distortion actually **increases** below a certain minimum power level, typically about 5-7% of full power. So if you use a speaker that is too efficient for the amp, you will not be getting the best sound out of it.

Blindjim > thanks for the links and observations. outstanding.
Ralph, why do you have to make this affair harder,? Lol

First 5 – 7%? I’ll presume this initial area pertains directly to the scenario you presented, otherwise, isn’t the first 10 – 20% of a class AB amp where one finds Class A functionality, and many adore that area of operation.

As for Damping, referring to another article from a JBL rep I saw online written some time back, the idea of rated damping factors is nearly fantasy when viewed practically vs rated given so many factors can and do intervien altering the amps ability to actually perform damping.
I read another one from a different source but a likewise quite technically oriented soul which is more recent but collaterally confirms damping ratings as nearly superfluous when put to practice. IOW picking amps based on damping ratings is not a true key spec one should lean on too heavily or at all.

Atmas > The bottom line is that equipment matching is still very much with us and won't be going away anytime soon.

Blindjim > lovely. And after all that great technical data, it comes to that? Super. ;-))
Many thanks.
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@gdhal > anything that can be done to extend Class A amp longevity?

Blindjim > as was said, ventilation.
Better still…. control the ambient temperature better immediately about the amp. Make the joint sweater wearing listening, or place the amp into an area where its quite cold via a dedicated AC. Heat kills. Especially extensive, and extended applications of it. Also, running it only in advance of listening sessions seems a prudent course of action, and in the interim keep a signal passing thru it as no signal allows it/them to produce their excessive temps given the way they operate in signal vs no signal eff.

I mean, if a pair of class A mono is gonna run ya $20K to God knows K, maybe spending a grand or two for extra cooling aint’ such a bad idea.

It is also why I like and use the idea of placing amps into an area apart from the listening room and cooling that area independently, and use remote extenders for operation.

I simply used an adjacent room and used longer speaker cables.

Later, I enclosed off a section of the listening room so a space was allowed for everything to be in that walk in closet like area accessed by bi fold doors in the middle of a false wall.

In either case, AC cools things quite well.
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IMO The number one issue with any and all of this speculation, rhetoric, and suspense is due to the lack of proliferation of the products sought, and the likely bigger attribute deeply set into the being of the audio possessed psyche who constantly notices the grass is, or might be greener on the other side.

Often we can’t just waltz across town to listen to the apple of our eyes. Usually the ??? piece is far far away making it more a dream or fantasy than a real option.

Distance however, does not prevent one from thinking, or believing that logistically out of reach piece either ‘is’ or could be the solution!

The mind is a terrible thing!

The scenario changes drastically and becomes a real quagmire when this same fool (meaning ‘me’) decides he wants to reroute his path from the SS highway and take a more scenic glass powered state road byway instead.

‘to thine own self be true’.Nice to hear perhaps, lots harder to do. ‘Once bitten, twice shy’ comes to mind during that wrestling match with being true to myself. The shoulders which get pinned to the mat are always the ones appealing SS power. despite their simpler nature and how they can be amended, they keep losing the match.

Return bouts with SS vs Tubes are perpetuated ONLY from what is being noticed by way of a desired loudspeaker’s demands for I/E from the amp. Either in reality, or in my head.

One example that keeps turning in my head is a user account of a particular speaker and how they decided that seemingly, watts alone made the speaker perform best.

This account said on pages right her that it worked well with 300wpc. Then better with 400, much better with 500 and then its very best with 600wpc!!

Along that way, nothing was said of the better build of each amp used in that trek. Merely an annotation of the power level, or available power itself was given the ‘spotlight’. I’ve found as have many here, when an amp retials for $60K vs an amp that retials for $6K, there is usually some disparity in the quality of the sound iself, not merely their possible power outputs.

Regardless, the note on power alone keeps revolving saying look to more power… and maybe quality too. But power first!

Its very disconcerting.

Throw in the fact many amps will indeed power what ever speaker, albeit to what ever degree of efficiency or optimization, and the apparent formulae for amp selection gets twisted and convoluted a bit more.

Wanna make the selection process still more difficult? Up the ante on the purchase prices. A lot. A whole lot. To the point where you’re actually playing with, or about to play with scared money.

For the uninitiated scared money is a gambling term. It means you should not be playing in that game if you’re using the mortgage, rent or child support funding, or simply can’t afford to lose the bet. Or such a cost puts you way out of your comfort zone. This is why ya need to know the players more than the cards most of the time and one of the ideas behind this thread.

Mapman said it and so has Atmas. Despite the actual values, specs, and ratings, synergy seems to claim numerous avenues which end up at its doorstep. Synergy, like beauty is in the ear of the listener.

I will whenever possible opt for the item whose quality I perceive is greater, if the electrical compatibility needs are even close. If I can swing it financially. Even if it hurts a little at first. Even for a while. When possible.

In the end, this is all about perception, which is indeed reality, then the sound, not the optimization is key. Argue it any way possible and it always comes out the same way.

I believe with all due considerations, a set of quality amps running a set of quality speakers will yield an ‘as’ commensurate presentation.

My hat is in the ring of best sounding amp, over that of the reputed ‘right’ electrically matched amp within reason, of course for one simply can not ignore outright, the factors amps and speaker marriages need for compatibility..

The right watts are what you hear in the showroom that impressed you enough to buy the amp in the first place.  The rest of the watts are what you hear at home when you try to get the amp to sound as good as when you laid out that hard-earned cash.

Go ahead and spend gobs of money on those pure class A amps that burnout after 7-10 years

Any truth to this? (i.e. is a class A amps life span known to be less than other designs)

No. We've been making class A amps for the last 41 years, and recently serviced one that had been in the field since 1988.

Just make sure that they can get adequate cooling and they are fine.

I'd like the process of component pairing to be less guess work and more analysis.

Me too- but its not going to happen unless the audio industry cares enough about quality of reproduction to address the shortcuts (including measurement issues) that have been taken so often in the last 50 years. Until then, equipment matching is a thing :/

If so, is there anything that can/should be done from a practical perspective to prolong the longevity of a class A amp?

Thanks.

Keep them biased right, Pass recommends palm hand test on the hottest part of the heatsinks being able to keep them pressed for at least 6 seconds (no brickies hands) any shorter and it’s running too much Class-A, and also keep them in a well ventilated spot.

Cheers George

Go ahead and spend gobs of money on those pure class A amps that burnout after 7-10 years

Any truth to this? (i.e. is a class A amps life span known to be less than other designs)

If so, is there anything that can/should be done from a practical perspective to prolong the longevity of a class A amp?

Thanks.

I’m also not convinced that the drawbacks of feedback are so bad it should be completely avoided.

A little story about feedback.

An output transformer "GOD" wound up some very nice massive cores for a friend of mine who was his buddy cost no object, interleaved to the hilt. I ended up with these cores when he passed away.
The transformer "GOD" I got in touch with and he got me to get some special C-Cores from Egypt where apparently is the best silicon. These transformers could be changed via the separate interleaved winding tabs for 16,8,4,2,and even 1ohm.

They sounded magnificent on a big pair of 150w tube monos I had, and I decided that maybe because the transformer were that good that there was maybe no need for feed back to help them have a lower output impedance. So I put on a variable feedback pot that could be changed from 30db down to zero. Adjusting the volume for the change in gain, it was clear as a bell that zero feed back was by far the best and because the transformers were that good the bass remained tight and dry.

So that proved to me, feedback is good in tubes to get better bass with lower output impedance, but it does have a negative effect on the rest of the music.

Cheers George 

I'm not sure I've ever seen any transformer coupled amp show damping over 100 into 8 ohm. I'm also not convinced that the drawbacks of feedback are so bad it should be completely avoided. I feel like thats a knee jerk reaction like many people have about guns. It's just a tool to be used.

The thing about feedback is there are more variables than the formula taught in school! You have to deal with RFI being injected into the amp via the speaker cables (and most designs don't...) and the amp has to have sufficient phase margins prior to application of the feedback... here is a great article about how to apply feedback properly:
http://www.normankoren.com/Audio/FeedbackFidelity.html

Since feedback is rarely applied with this sort of care, its incorrect to say that eschewing it is a 'knee jerk' reaction. Its misapplication is audible!

With regards to speakers, there is never a need for 100:1 (or more) damping; almost any speaker made is overdamped with a damping factor that high. Here is another great article that despite its age has stood the test of time, written by the head engineer of Electro Voice:
http://www.dissident-audio.com/Loudspeakers/CriticalLSDamping.pdf

Note that at the time of this article, there were speakers that needed far less damping than even 5:1, and there are still speakers around today that barely need that or even less (as an example, Nelson Pass demonstrated a small yet very impressive open baffle speaker at RMAF about 10 years ago that was driven by a current source amplifier, so the damping factor in that system was less than 1:10 and you did read 1:10 correctly, yet it played bass quite well).

It was Electro Voice and MacIntosh that led the way in championing the idea that the amplifier should be a voltage source and the speaker voltage-driven, back in the late 1950s and into the 1960s. But the simple fact is that this model simply did not and does not encompass all speakers and speaker technologies (any speaker that does not employ a cabinet would be an example, as well as many speakers that do have cabinets..). In addition, all amplifiers that are capable of acting as a voltage source are push-pull, and such amps (with rare exception) have distortion characteristics wherein the distortion actually **increases** below a certain minimum power level, typically about 5-7% of full power. So if you use a speaker that is too efficient for the amp, you will not be getting the best sound out of it.

The voltage model is intended to eliminate equipment matching issues, and if you are only interested in box store mid fi, none of this is a problem. But in high end audio there is quite a bit of diversity such as planar speakers, horns, full range devices as well as more conventional designs, SETs, OTLs, class A, class D, etc. because everyone is approaching the goal of electronics sounding like real music in a different way. So if you apply a generalization such as 'all amps should be voltage sources' right away it is belied by very notable exceptions!

The bottom line is that equipment matching is still very much with us and won't be going away anytime soon.

Wolcott Audio tube amp:
http://www.wolcottaudio.com/WA_Pres_why.htm
http://www.wolcottaudio.com/WA_Pres_specs.htm
Best tube amp?

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.

Best regards,
-- Al

P.S:  Ghosthouse, thanks for the nice words :-)
 

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.

Cheers!

Well, my Harbeths are easy to drive and nobody will deny that they are very good sounding speakers. So it can be done.

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.

The First Watts are the best watts.

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.

Cheers George 

The good watts are pretty much always the clean ones, ie no clipping.

Clipping has, is, and always will be public enemy # 1 for good sound. Does not get near the attention and focus in discussions that it should.

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.

Cheers George

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).

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.

Best regards,
-- Al

Hi Ghosthouse,

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.

Best regards,
-- Al

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?

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.

https://www.stereophile.com/images/416WiSabfig1.jpg

https://www.stereophile.com/images/archivesart/710Wilfig1.jpg

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).   

Cheers George

Combine hard to drive speakers with most tube amps and you have a response that is all over the place.

Yeah EQ'd to the sh**-***se, some call this tube sound or euphonic's. I call it an equaliser.

Cheers George

Got it.

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.

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. 

Cheers George

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.

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.

Cheers George


   
  

Hi Jim,

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:

https://forum.audiogon.com/discussions/audio-research-ls-25-mkii-compared-to-actual-ar-production

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.

Best regards,
-- Al

@almarg
Hi Al. Thank you.

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.

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.

Cheers George

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! 

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?

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.

Cheers George

Hi Jim,

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.

Best regards,
-- Al

@atmasphere
Thank you.

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.

Best regards

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.

Cheers George

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.

Cheers George