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Feb. 2018
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"Damping factor" - another great audiophile myth?

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  • "Damping factor" - another great audiophile myth?

    How many times have you heard the tired old phrase that amplifier A must be better than amp B because A has a 'much better damping factor'. We have discussed in the amplifier A-B testing that, under absolutely optimal conditions, a level difference of 0.1 or 0.2dB may be barely audible to the most attentive listener in the middle frequencies. Now read the report.

    Well, is there any truth whatever in the cliché? Or is this yet another example of marketing claptrap? You decide.

    >
    Attached Files
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  • #2
    Widely held misconception

    Yes, there is the widely held misconception that the damping factor exhibits a control far greater than it actually does, and I blame the simple mathematical (mis)representation of damping factor by the term Rspeaker/Rsource, which implies a ratio of effective change in damping which the analysis shows is not actually the case.

    However I do not doubt that amplifiers with a low damping factor do often exhibit a lesser controlled sounding bass than those with higher ones. In the 70s I temporarily bought a Quad 303 which I substituted for my then in use Nelson Jones 10+10 home built amp., and the results showed a considerably less controlled bass. What was happening is a subject for investigation.

    My recent amplifier changes have shown another improvement in that the bass is tighter, but the improvement in damping factor must be only minimal, the O/P halves being composed of three transistors rather than two as in the previous amp., which must produce only a slight reduction in O/P Z.

    The problems of acquired misconceptions from half studied, and half understood science enumerate. In the 70s I was told that 'Tubing is stronger than bar'.
    That is true for a fixed amount of material per unit length, and only for that case, but this was taken by some to mean that if one drilled out a solid bar it became stronger. One cannot make a bar stronger by removing material from it.

    Comment


    • #3
      Cracks in the concrete?

      Originally posted by Pharos View Post
      Yes, there is the widely held misconception that the damping factor exhibits a control far greater than it actually does, and I blame the simple mathematical (mis)representation of damping factor....
      I have this growing feeling that there may not be one single generally held 'fact' amongst audiophiles that is actually true and demonstrable under controlled conditions. Is it possible that the entire audiophile industry has foundations of sand?

      What is odd is that hard, cold physics is (obviously) brought to bear by equipment designers to create and produce physical audio equipment, but that hard, cold physics is then replaced by mythology when the product reaches the audiophile marketplace. I'm struggling now to think of one 'fact' that could be independently validated. Can you do better than me?

      How did a hardware industry of the 50's transition into a fashion industry where there are no absolutes, no norms, no frames of reference .... all opinion. Is it any wonder the industry is stagnant? Expensive blue-sky R&D is unnecessary because a new marketing spin will keep the production lines flowing with yesterday's technology. It really is a strange business and for sure, the consumer is not benefiting.
      Alan A. Shaw
      Designer, owner
      Harbeth Audio UK

      Comment


      • #4
        Myth upon myth upon myth - then given a marketing spin

        So-called "Damping Factor" is pure marketing spin - nothing more, nothing less. The implication that Amplifier A can exert a vice-like grip over the loudspeaker cone compared to Amplifier B is clearly highly attractive to the people that write the brochures or reviews, but it tells you nothing about the rest of the system. Damping Factor tells you less about how an amplifier sounds than 0-60 times tell you about the day-to-day driving experience of a car.

        Of course, a designer can make the output impedance of an amplifier equal to any value he or she wants. As close to zero as the output connectors allow if you take the negative feedback from the terminals. And including negative - which some active system designers might want (I think that's the essence behind Yamaha's Active Servo Technology, for what that's worth).

        Worrying about 0.1 verses 0.01 ohms of output impedance is specious in the extreme when you consider that you have 6 (probably more) ohms in series from the cabling, inductors and voice coil. But it's the difference in DF of 80 and 800. Wow...

        Have a look at page 25 of this book preview:

        http://books.google.co.uk/books?id=X...page&q&f=false

        Actually, many here would enjoy the bulk of the first chapter of that book. It contains a pretty comprehensive discussion of subjectivism in audio, and is fairly accessible to non-technical readers. PDF versions of earlier editions can be found if the gaps in the preview are a problem, and as each new edition adds new content (rather than major re-working), these earlier versions remain just as valid.

        There are lots of amplifier myths out there - like Class A operation always results in better sound, whatever the rest of the amplifier might be. Or turning up the bias on a Class B amplifier (to make Class AB) will improve the sound (no, it always results in increased distortion, although the rest of the amplifier needs to be pretty "sorted" for the difference to be apparent, and it certainly won't be audible). Or that mono-bloc operation is essential for decent stereo imaging. Or MOS-FETs sound better because they are more like valves (they don't, and they're not).

        Overall, a modern, competently designed amplifier that is not clipping will have a pretty small influence on the overall sound. Much more than cables and other tweaks, obviously, but it's still a tiny slice of the pie, where loudspeakers and room acoustics dominate, followed by source equipment, then the amplification. I've often thought about how big each "slice" should be, and I guess that amplifiers would be comfortably less than 20% or perhaps 10%, providing they have the power you need for your chosen loudness level.

        Sadly, there will always be those who believe the spin. As an engineer, not a marketing expert or businessman, I don't fully understand the arguments, but I do accept that it's essential to differentiate yourself in a crowded market. But it's a shame that manufacturers don't follow Harbeth's lead, promoting sensible engineering and long-term stability and sustainability. Most businesses prefer to sell new products rather than support a customer through a long relationship with their original purchase - I know that brings the money in, but the amount of perfect good gear that ends up in landfill because of consumerism is simply shocking and utterly unjustifiable.

        Certainly, most mainstream consumer electronic goods are no longer built to last, or to be repaired when they fail. Manufactures only stock the bare minimum of spares so they can claim to complying with the Sale of Goods act. And the service trade has nearly entirely died in the last 5 years - why would the public want to spend £100 fixing their old TV when they can buy a new one for not much more in the local supermarket? Sorry - I've drifted away from the topic, but this particular vicious circle is starting to affect all walks of life, and the world is becoming a poorer place for it.

        All the best,

        Mark

        Comment


        • #5
          Nurture the deluded and make $$$$$ !

          Originally posted by A.S. View Post
          Well, is there any truth whatever in the cliché? Or is this yet another example of marketing claptrap?
          The underlying problem here is that, regardless of the quality of the science presented, a significant body of audiophiles will destroy it with the argument that "human aural acuity is far greater than mere science can encapsulate" or other claptrap to that effect, and promptly place their collective heads back in the sand.

          The canny marketeer will feed and nurture this delusional state.

          Comment


          • #6
            So Mark, that's a few more myths exposed. Where does the poor audiophile now stand? So there is no truth in damping factor, Class A operation, MOSFETs, bias tweaking .... for goodness sake man, what is there left to believe in? People need to have something to put their faith in. Next you'll be saying that the cable industry are all crooks and that Gypsy Rose Lee* speaks only the truth!

            It really is possible that the entire audiophile game has nothing more rigid than foundations of strawberry blancmange? I am in shock.

            Seems that after years of being one of the few talking sense, others are now stepping forward. Great.

            *Last known address: a Romany caravan hitched up on Brighton Pier. "Guaranteed results". "Astonishingly accurate" (that sounds familiar...).
            Alan A. Shaw
            Designer, owner
            Harbeth Audio UK

            Comment


            • #7
              High output impedance ...

              It has been suggested by a design engineer I trust that amplifiers with higher output impedances alter the filter frequencies of the passive crossovers they often drive, lowering the tweeter one and raising slightly the bass/mid one (in a two way speaker).

              Maybe this is exaggerated in many transformer coupled valve amps, with output impedances of getting on for half an ohm and driving nominal 4 ohm speaker loads, this being used as part of the speil to promote "active" speakers, where the crossover is before the amp and each amp module is directly coupled to the driver concerned all through its pass band. The argument is made that passive crossovers progressively disconnect the driver from the amplifier with rising frequency as they begin to take effect.

              Comment


              • #8
                Let's spend $$$$

                Love this quote from page 15:

                "It is now commonplace for audio critics to suggest that frequency-response inadequacies should be corrected by changing loudspeakers. This is an extraordinarily expensive way of avoiding tone controls."

                Comment


                • #9
                  Er......?

                  Originally posted by DSRANCE View Post
                  ...The argument is made that passive crossovers progressively disconnect the driver from the amplifier with rising frequency as they begin to take effect.
                  And? How would that manifest itself as a sonic problem if it were true? The amount of energy in the mid and upper frequencies is, as we have demonstrated, negligible.
                  Alan A. Shaw
                  Designer, owner
                  Harbeth Audio UK

                  Comment


                  • #10
                    A sense of perspective and priorities - the dominance of marketing speak

                    Surely it is only because most audiophiles lack technical knowledge training and understanding, that they are not able to evaluate the lack of validity of much of the sales related and innaccurate, rhetoric and mysticism.

                    There are facts in audio which I think we all will agree with; hard scientific correlates which reliably can be shown to affect sound quality, and these were discovered decades ago by the pioneers in the heyday of Hi-Fi development.

                    Low O/P Z is a valid objective which does affect cone control, but only minimally so; it is not the 'be all and end all' which it is often portrayed to be by reviewers; but perhaps they too lack the scientific understanding, and attribute a tighter sound to a reduced O/P Z when that is not actually the cause.

                    There are also some differences resulting from Mark's technological list, but how significant? As these differences approach zero, we are left by definition, 'evaluating' them in the absence of objective evidence, there being so little with which to substantiate any truth.

                    But in the absence of real progress from the 70s onwards, the verve, energy and excitement which had resulted in increased public awareness and participation in Hi-Fi, probably resulted in a lessening of the growth of sales seen at the time of the Tottenham Court Rd 'warehouses' selling high volumes of much discounted equipment.

                    This is in my opinion why the marketing people gained power and prominence; to prop up the lessening sales, and to do so they used mystical terms and 'magical' language, coupled with an emphasis on the style of the products.

                    But this is not unique to Hi-Fi; look at the fitness culture, and the basis on which ancillaries are sold for it which are so often just mythical and illusory, and for the same reasons. Expensive trainers are sold with high heels which are actually more likely to cause injuries, and drinks are sold on all sorts of bases which are unfounded, when water is fine. (Isotonic; Ha-Ha).

                    In the absence of real scientific work, and resulting progress in any field, the need for continued sales to support business will always I suspect result in the use of misleading BS.

                    Comment


                    • #11
                      Speaker mounting?

                      Originally posted by A.S. View Post
                      I have this growing feeling that there may not be one single generally held 'fact' amongst audiophiles that is actually true and demonstrable under controlled conditions. Is it possible that the entire audiophile industry has foundations of sand?
                      It's pretty weak, but how about that speakers placed on wall mounted shelves or box pieces of furniture will not sound optimal? That can be verified and is a generally held fact. Best I can suggest.
                      Ben from UK. Harbeth Super HL5 owner.

                      Comment


                      • #12
                        Hardness etc.

                        Originally posted by A.S. View Post
                        And? How would that manifest itself as a sonic problem if it were true? The amount of energy in the mid and upper frequencies is, as we have demonstrated, negligible.
                        Harshness (I'm told) and too great an overlap between the drivers which may upset frequency balance. What about consistent phase tracking across the crossover?

                        Apologies, I'm not baiting, but just trying to discover as simply as possible the hows and whys of it all and possibly with objective tested backup.

                        A HUGE exaggeration here, but back in the mid 70's, I remember comparing IMF transmission lines (the bigger ones which would dwarf 40.1's) and other more conventional speakers using different amps (I think one was the Radford HD250 and the other a Crown pairing, similar to which which I inherited and now use in very gently updated form with great pleasure with modern sources and the Soendors). On one amp, speaker 1 seemed to have no bass at all compared to the other bigger one, yet with the Crown amps with high damping factor, almost the reverse was true, the bigger IMF jumping into line and the smaller one sounding far more powerful and far closer. NOT a scientific evaluation by any means, but recent experiences of SHL5's with some valve gear can give very inconsistent results, where well-sorted solid state amplifiers do seem to give more predictable sonics of very high quality - to me at any rate...

                        Comment


                        • #13
                          Crossover overlap?

                          Originally posted by DSRANCE View Post
                          Harshness (I'm told) and too great an overlap between the drivers which may upset frequency balance. What about consistent phase tracking across the crossover?...
                          Let's just break your comment (which you clearly believe) down into two parts.

                          Part 1:

                          Originally posted by DSRANCE View Post
                          Harshness [is] too great an overlap between the drivers which may upset frequency balance...
                          OK, have a look at Fig4. here. For a two-way speaker to acoustically sum to flat (or nearly flat) around crossover there cannot be 'too great an overlap': there has to be just the right amount of overlap, not too much and not too little in the crossover region. If there is too much, the resulting summed sound from the woofer and tweeter may give a boost in output; too little overlap and the summation may be depleted dependion on level and phase relationship. Either case is the result of design decisions by the crossover designer. Most speakers made since the mid 60s have had a tolerably smooth junction between woofer and tweeter, so this is really crossover overlap issue unlikely to be the real source of hardness.

                          If the designer's attention is drawn away from the crossover region (because he is a bass fan, and spends all his time tweaking the bass end), he may well be unaware that he has created a peak or hole in sound output at crossover, and if that is the case, we could indeed reasonably expect that to be audible. We could synthesise that same peak/dip in a perfect good speaker using a graphic EQ and we could reasonably expect to hear the same effect, which could indeed sound 'hard'. But that is not specific to passive crossovers - an active solution having the same park or hole probably would also have a characteristic sound. If anything, most speakers have a depression at crossover, not a peak.

                          Part 2:

                          Originally posted by DSRANCE View Post
                          ...What about consistent phase tracking across the crossover?...
                          I'm not trying to be difficult here David - far from it - but what do you mean exactly? We know that the ear is remarkably tolerant of phase. I refer you back to my Fig.4. If the phase and amplitude (they must be considered as a pair together, never one alone in isolation) of the woofer and tweeter's acoustic outputs are not in some sort of predictable relationship with each other through the crossover region, they cannot ever add together to give an approximately flat response through that region. If that relationship is not, at the very least, smooth through the crossover region - which I guess is what you imply by 'consistent phase tracking' - then the summed outputs will, depending upon level and phase together, show constructive (adding to a peak) or destructive (adding to nothing) interference which may well be audible, and again, could be synthesised on a good loudspeaker with an external EQ box.

                          What you hear is what you hear. What you hear is evidence of something going on in the design of the speaker, intentional or not. It is absolutely impossible to arrive at any valid conclusions about the source of the hardness unless you partially dismantle the speaker and acoustically measure the drive units with/without crossover. You have to analyse by measurement to uncover the source of the 'hardness' you mention: it just isn't likely to be as simple as a crossover overlap - it will be more subtle. It would only be the most careless or misguided speaker designer who would so poorly execute the transition from bass/mid/top by screwing-up the crossover. But it is not at all uncommon to hear this 'hardness'; surely there are not legions of inexperienced speaker designers are there?

                          Having cautioned you and encouraged you to do some measurements, I dismantled a speaker from a well known Euro-brand because it was fantastically fatiguing, utterly intolerable even for a few minutes. How this product came to market and received favourable reviews remains a mystery. What the measurements (crossover bypassed) showed is that the bass unit has a huge peak near to crossover frequency. No amount of clever crossover design can eliminate that. Boy, does that modern speaker sound hard. But neither you, nor me nor anyone else can do better than an educated guess as to where 'hardness' is coming from. We would have to roll up our sleeves and do some serious forensic investigation - and who'd have the time or interest?

                          As I only said yesterday, 'What is odd is that hard, cold physics is (obviously) brought to bear by equipment designers to create and produce physical audio equipment, but that hard, cold physics is then replaced by mythology when the product reaches the audiophile marketplace. I'm struggling now to think of one 'fact' that could be independently validated.'
                          Alan A. Shaw
                          Designer, owner
                          Harbeth Audio UK

                          Comment


                          • #14
                            'Damping factor' and audibility

                            From personal experience I'd say that a high damping factor is not important in selecting an amplifier. I once switched from an amp that a damping factor of 1,000 to one with 200 and preferred the latter. Also, not all amp makers advertise this number and if they do, how likely are they to give a low figure?

                            Comment


                            • #15
                              Investigation of cause

                              DSRANCE, your post (12) describes some interesting experience, but with no disrespect intended, I cannot clearly understand it and would like to; particularly the sets of conditions under which you obtained the various subjectively experienced bass performances.

                              I agree with you BAS-H that one can produce changes in the performance of a system by changes, for example, in speaker mounting. A few months ago I purchased with considerable scepticism, and a cast iron refund guarantee of refund if required, a pair of granite plinths for my speakers; these to stabilise and decouple from the wooden floor.

                              The change in sound was immediately felt, and it was not slight or subtle; it gave the impression of an increase in output level of bass and mid of 3-4dB. Hackneyed and 'audiophilisitic' as it is, the sound was much more dynamic.

                              I am sure that my experience, and of others hearing these results, could be verified and measured as a scientific change, and my guess is that lower coloration from the floor, and lower 'rocking' of the speakers are a reasonable 'stab' at explaining what has happened. My 'Funky friend AK' has heard the results, seen the improved stability, and looked at my mathematical explanations, which he thinks are valid.

                              If we put a brick wall low pass filter between a preamp and power amp set at say 5kHz, we will hear the loss of top, and it is a fact that the top has been removed above 5kHz, measurably.

                              If we listen to a 1960s preamp using OC21 transistors, we will hear the appalling S/N ratio, (of only about 20-30dB), the music embedded in the 'sound of frying eggs'. This is clearly audible, and verifiable by measurement.

                              I regard anecdotal listening results as an experiential database, which although lacking in any scientific rigour, does provide a basis for further investigation. This is analogous to becoming aware of the smell of burning, and then running through ones mind whether or not one has left something cooking which one has forgotten about, whether a mains socket is failing, or the electric fire is too close to a furnishing.

                              One then runs through possibilities, ruling out the electrical socket, because the smell is not the 'fishy' one of burning phenolic plastic, recalls that one has not started cooking lunch yet, and proceeds through other possibilities to seek out the actual cause. Without that initial sensing, one would not have any direction indicated for the investigation of cause.
                              Last edited by Pharos; 03-02-2013, 12:29 AM. Reason: Errors due to tired to disfunctionality, mind

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