Assuming the definition of dynamic “range “is the difference between the softest sounds & the loudest ones a speaker is capable of without minimal distortion, then high efficiency speakers don’t necessarily have a greater range. How dynamic they sound, to me, meaning how quickly they can start & stop & thus sound more like live music in this way, is another story. High efficiency speakers w/ reasonable impedances ( not silly low w/multiple drivers connected in parallel), generally horns of some type can sound much more dynamic than low efficiency ones. I’m a believer of this & own & love my Volti Audio Rivals @ a true 98db efficiency. They can image pretty well, pretty detailed, not crazy extended at either frequency extremes but with a good input, sound more like live music than most other speakers I’ve heard at anywhere near their price range. I guess I value true dynamics over etched, hyper detailed “hi fi” sounding speakers. We all have favorites.
@jonwolfpell This statement is false; the reasons why explained on the first page of this thread. |
Sorry, that was a bit snarky and defiantly not a fair comparison of some of the very nice and efficient speakers of today and even some vintage. Back in the early 80s, I much enjoyed my Vandersteen, 2Cs but by mid 80s, while looking for something that would make a little larger, deeper stage in my large listening area I auditioned both the big K-Hornes and the large Altec Lancing speakers. I did enjoy the big full stage they presented but decided, even for my relatively large area, were a bit much. I Auditioned and bought a pr. of Quad ESL 63s and fell in love with their deep, wide stage and their organic rendering of acoustic music and voices. Even more so, the Duetta Sigs. I Have been a fan of Electrostatics and Planers since. Some years later, because of a change in living spaces I had to revert to smaller, monitor style speakers. After moving back into a larger home with a decent sized listening room, I had a chance to pick up a pr. of the little Maggie 1.7s and like them allot. If I could find a pr. of used 3.7i within a reasonable driving distance of my area I’d pick them up, without worry of their efficiency. If my old ADCOM doesn’t do a good job at driving them, I should be able to find a fair buy on a used Bryston, Krell, Coda, etc that would. To be fair, except for Spatial Audio (which I did like) I’ve not auditioned or entertained much, the idea of going with an efficient speaker - so my opinion of them may be a bit limited and irrelevant and my love for electrostatics and ribbons, a bit biased.....Jim |
That's funny! Mike +2 @phusis |
+1 @phusis The snarky misguided jukebox reference adds nothing to what is a good and informative thread. Different opinion and perspective can be contributed without condescension for sure. Charles |
@jhills --
Absolutely fair. Being natural representatives of the (very) high efficiency segment: do you have experience with horn speakers, be that horn hybrids or all-horns? Tall large-horn speakers can have a sound reminiscent of large panel speakers, certainly akin to a limited dispersion "big open and natural sound" you’re describing, and a sound that sets itself apart from smaller, low efficiency box speakers in general. Not trying to convert you into being a horn freak (I suspect that attempt would be futile), but just to break down more stereotypical assumptions of their characteristics as being in every case from the same piece of sonic cloth. With horns in particular, size matters, but few want to accommodate that in their homes.
I hope that’s not your condensed takeaway from what high efficiency is necessarily about. By contrast a jukebox is only representative of that: a jukebox. |
Last word in efficient or not, I prefer the big open and natural sound of electrostatics and planers over boxes, hands down, but that’s just my personal preference. My favorites over the past many years was a pair of (not so efficient) Apogee Duetta Sigs. driven by a Mark Levinson 333. Not everyone’s cup of tea, but was mine. If all I wanted was loud, forward and dynamic I’d buy a Jukebox.....Jim |
Lonemountain- why did you arbitrarily start at 102 db volume for the high efficiency speaker but 86 db for the lower one? The more efficient one can also of course play @ an 86 db level using a small fraction of a watt & thus probably w/ extremely little amp distortion. Both speakers can have the same dynamic range assuming a sufficiently powerful enough amp for the lower efficiency speaker. The high efficiency speaker can achieve it more easily, likely quicker too & w/ much less required power |
@jhills wrote: "... it seems a bit irrelevant unless you are listening at live concert SPLs (104 - 115+ db)." In my experience freedom from compression effects is audible at pretty much all volume levels, including low levels, which is where I normally listen. I never listen at anything approaching "live concert levels", and only rarely listen "loud". Duke
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@jhills -- Making this about low efficiency speakers/higher power SS amp vs. high eff. speakers/low power tube amps is not the strictly defined combo context here, but rather low vs. high eff. speakers - certainly per the OP. It makes sense using low powered tube amps with high eff. speakers (and vice versa with low eff. speakers), but you get lots of the benefits with high eff. speakers no matter the amp principle. Myself I use a combination of class A and class D solid state coupled actively to my high eff. speakers, and from my chair bypassing the passive filter is the real treat with the benefits it offers with digital filter settings to more readily accommodate horns with steeper slopes, etc.; not whether tube amps are used instead of SS. Re: playback volume, it’s a common misconception that high SPL capabilities (with high eff. speakers) necessarily equates into the need or want for high SPL playback. To me at least it’s generally about how it sounds at average SPL’s (i.e.: ~65 to 90dB range) and how the segment of speakers I’ve chosen excel here, but with the added bonus of a greatly enhanced, effortless dynamic bandwidth, in addition to prowess into transient capabilities and overall presence and physicality of reproduction, whether at low or high SPL’s. It’s not about clearing the roof over my head with +120dB levels, but the incentive to listen at higher SPL's with speakers that can handle it cleanly with ease and powerfully is not diminished, I might add. And let’s expand a bit on ’effortless’: headroom is your friend - can’t be re-iterated enough, it seems - and that even more so when we enter LF territory. You want 105dB clean peaks at the listening position you want headroom to spare, not just merely enough, and this goes for speakers as well as amps. So, when I say my subs can put out ~127dB’s at the LP down to almost 20Hz, that’s not to say it’s my desire to actually achieve those levels - far from it - but once you hear bass reproduced effortlessly at every desired level, headroom makes sense. |
While I much enjoy the wisdom, experience and informative posts of Audio Kinesis, Atmosphere and others, the debate of which is best between which combination - efficient speakers paired with a low powered tube amp vs low efficiency speakers paired with a quality high powered SS amp (correct me if I'm wrong) it seems a bit irrelevant unless you are listening at live concert SPLs (104 - 115+ db). I listen to my system several hours at a time, three to four evenings a week and can't even imagine wanting to listen to music that loud or re-create the scope and volume of a live concert in my home. So, for me, at any volume I now care to listen at, I'd say either combination works very well. At lower volumes my inefficient 1.7 Maggies seem to perform quite well with either my 100W Rogue, tub amp or with my 200W/350W SS ADCOM.........Jim
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I like a Dynamic ...Live.presentation from my system with a DEEP soundstage. I like to transport myself right into the auditorium....I wanna' Be There. Low powered Tube amp with the glorious 845's and a high eff. speaker system (Tekton...Klipsch..JBL etc. gets me there. Let's enjoy the Music...Not the system. |
Just to clarify on this comment, at the point the transformer saturates it will also be making distortion and thus describe an upper limit on the range of the speaker. Sound Lab is known for using dual transformers, one for bass and one for treble to get around this problem a bit. |
@deludedaudiophile wrote: "can you comment on room response of line arrays? "... I expect that electrostatic speakers and large planar speakers must be fairly immune to these power compression / thermal modulation effects within limits?" The room response of a given line-array system depends on the specifics. Obviously at frequencies where they approximate a line source the sound pressure level is falling off at about 3 dB per doubling of distance rather than the normal 6 dB per doubling of distance, not counting the contribution of reflections. There are of course tradeoffs to be juggled. If small fullrange drivers are used, they beam moreso than most tweeters in the horizontal plane, resulting in a pretty big spectral discrepancy between the direct sound and the reflections. If tweeters are stacked alongside midwoofers, the frequency response in the crossover region changes significantly with the horizontal angle. If there is a central tweeter flanked north and south by stacked midwoofers, the tweeter may not approximate line source behavior as well as the midwoofer array. All of that being said, with a line-source-approximating speaker the direct sound tends to be more dominant than with a point-source-approximating speaker, so I’m not sure how audible the aforementioned off-axis anomalies tend to be in practice. Electrostatic speakers can have compression from transformer saturation at high power levels, and in extreme cases the transformer can overheat and melt. My impression is that in general they are less prone to compression than cone-n-dome speakers, but also less efficient and/or more difficult to drive, and in general will not go as loud as comparably-priced cone-n-dome floorstander speakers. Single-ended planar magnetic speakers, those having magnets only on one side of the diaphragm, have a compression-ike mechanism because of the non-linear motor; that is, the motor strength decreases when the panel is further from the magnet, and increases when the panel is nearer the magnet, such that motor strength available for the higher frequencies is modulated by the lower frequencies. A push-pull motor structure eliminates this effect. I don’t know much else about compression mechanisms specific to planar magnetic speakers, but I am not under the impression that they are champions in the realm of dynamic contrast. Loudspeaker/room interaction happens to be something that I give high priority to. The two types of speakers I sell are large, curved, line-source-approximating fullrange electrostats, and hybrid horn systems. I think full-range horn systems can be superb but they are inevitably larger than what I want to work with. Duke |
Huh? Why? The dynamic range is a function of the recording being played back. Its not as if a system using more sensitive speakers is somehow only being fed signals of less dynamic range :) The 250 Watt amp has slightly over 10dB more power than the 20Watt amp, but the 102 dB speaker has 16dB over the 86dB speaker; your numbers don’t seem to add up. Or am I misinterpreting what seems to be written here? @deludedaudiophile ESLs are immune to this problem as I stated earlier since their MO uses a power supply plugged into the wall. Field coils are as close as you can get to this with ’conventional’ drivers. Of course both technologies do have their practical limits. Both easily measure and sound more dynamic than their permanent magnet cousins. IMO/IME your surmise about horn speakers isn’t quite correct (although we are starting to see more line arrays in PA applications). You may not be taking into account the controlled directivity of horns which line arrays and planars lack. In a home instead of a PA application, you are probably correct since the energy needed to fill the room is so much less. But some horn systems are pretty efficient; over 104dB and so only need a fraction of a watt for 90% of all listening. ESLs and all the line sources I’ve seen so far need considerably more... @audiokinesis Thanks Duke! |
@johnk , I see no physical mechanism by which a horn speaker would throw better than a dynamic speaker. The impedance matching improves efficiency, but it is still effectively a point source so it must follow the inverse square law. Only a line array and the equivalent electrostatic or planar speaker would have improved throw. The room response would be different though. @audiokinesis can you comment on room response of line arrays?
@atmasphere @audiokinesis , I expect that electrostatic speakers and large planar speakers must be fairly immune to these power compression / thermal modulation effects within limits? By virtue of the large number drivers and small amount of power per driver, line arrays must be pretty immune as well.
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A 110db horn running off 20 watts will not see any heat that can cause compression a 86db speaker requiring over 250 watts will be near melting at peak SPL levels. A horn also has better throw so at distance, its SPL level isn't dropping as fast as a standard dynamic speaker design. Standard dynamic designs can sound pretty darn nice but they are toys when compared to a proper large horn speaker. Now I know most cant house anything over a toaster-sized box or overly slim tower and they don't want to consider that larger is better even though the brand of small boxes they bought most likely has a much larger model as the top of the line. |
I know many here hate ASR, but it would be good to collectively push them to do more frequency response measurements at varied power levels, and perhaps at different frequency sweep speeds to induce this issue. I personally don't see Stereophile doing that and I definitely don't see suppliers going out of there way to highlight problems. |
Thanks Duke, that might explain why I really like tube amps feeding high efficiency speakers. Most of the tube types I like don’t put out much power. I like 45 and 2a3 in SET amps and 6L6 and KT 66 for push pull amps. In my own amp that is currently in my system, I run 349s—two per channel for about 5 watts. |
@inscrutable wrote: "if the amplifier has a very large - let’s say infinite - current capability, so can maintain voltage to be applied as the speakers impedance changes with signal frequency changes …?" A constant-voltage amplifier will put out reduced wattage into a higher impedance. That's just the way that type of amplifier behaves. However a constant-power amplifier will put out essentially the same wattage into the speaker's impedance even as it changes, at least within a realistic range of change. Most tube amplifiers have a constant-power characteristic, and therefore the system's dynamic contrast would be less sensitive to heat-induced changes in the drivers' impedances. Duke |
Good dynamics is not just about the range of capability. It is more about whether, when the signal goes up, there is a corresponding increase in the output of the speaker (i.e., no compression). This is less the case with low efficiency speakers because, more watts have to be delivered for any given volume level, and a bigger proportion of those watts are being dissipated as heat. The problem with this heat is that heating of components increases resistance which reduces the flow of current/power. In other words, there is not a proportional increase in driver output to the power being delivered to the speaker because of such heating. This is thermal compression and it is a bigger issue with low efficiency drivers which, dissipate more of the power being sent through the driver as heat than is the case with high efficiency drivers. |
I appreciate this informative discussion. @audiokinesis your detailed explanation for the inherent advantages of a higher efficiency/sensitivity speaker I find more compelling and logical compared with the counter position for the lower efficiency speaker expressed thus far in this thread. What you have described/explained does seem to correlate to the actual listening experiences of what others here have reported. Charles |
@deludedaudiophile, to quote my favorite line from The Princess Bride, with poetic license invoked: "Speaker design is tradeoffs, Highness. Anyone who says differently is in marketing." Duke |
So now you are poking holes in those that proselytize first order cross-overs for better time alignment :-) In many ways speakers are much more interesting that the other parts of an audio system, but so much less time seems to be spent discussing them beyond the cursory. Aesthetically or for practical reasons, efficient speakers, which I assume are normally large, may not be practical. I did mean more immune. Thank you for the correction. |
@deludedaudiophile wrote: "I was more thinking smart people, i.e. like what I see with Kii, as a start, will figure out some way to compensate for these effects in real time." I think you are right, though there is a limit to how much compression "active gain riding" can compensate for. More wattage to compensate = more heat = more compression = even MORE wattage needed to compensate... "From a simpler aspect, would not an active cross-over system be less [do you mean MORE?] immune to the effects of variable voice coil resistance on speaker response including critical crossover points?" Yes, but if you start out with drivers that don’t compress significantly anyway, you have already addressed the crossover issue. Also, second-order and higher passive crossovers are much less sensitive to driver DC resistance variations than are first-order passive crossovers. Duke |
@audiokinesis , I was more thinking smart people, i.e. like what I see with Kii, as a start, will figure out some way to compensate for these effects in real time. From a simpler aspect, would not an active cross-over system be more immune to the effects of variable voice coil resistance on speaker response including critical crossover points? |
+1 @avanti1960
I agree: Higher amplifier power is not a substitute for speaker efficiency, dynamics come from the speaker not the amplifier. Mike |
@deludedaudiophile wrote: "You are convincing me more and more that active is the way to go long term." Going active will have no direct impact on driver compression effects, but if you are "rolling your own", going active may make it easier for you to use drivers which have inherently low compression characteristics. Duke |
@lonemountain wrote: "my point about dynamic range was "system dynamics" not one system vs another. The 86dB efficiency speaker on a 250W amp has more total dynamics to cover incoming source material of a wider dynamic content than the 102dB/20w amp system. " In your example upthread, the 86 dB/250 watt system has a maximum SPL of 110 dB, while the 102 dB/20 watt system has a maximum SPL of 114 dB (actually the math says 115 dB). How is 110 dB max SPL "more total dynamics" than 114 dB max SPL? The only way I can see that happening is IF the system noise floor is at least 5 dB lower for the 86 dB/250 watt system, and that’s not something you have included in your example. (Dynamic range does not start where the amp is producing 1 watt; dynamic range starts at the system noise floor. I mention this because, upon re-reading, one of your posts above seems to make that assumption.) And here’s another real-world effect which may come into play: If the 20 watt amp is a tube amp (which is likely), and if the 250 watt amp is a solid state amp (also likely), clipping will become audible and objectionable about 3 dB sooner on the 250 watt solid-state amp than on the 20 watt tube amp. In other words, you can push the AVERAGE SPL 3 dB higher on the tube amp than on the solid state amp before clipping becomes audible and objectionable. So instead of the 102 dB/20 watt system having 4 (or more precisely 5) dB more dynamic range from the raw math, real-world that difference may be more like 7 (or 8) dB. Duke |
Thank you for the post. Very interesting. This is something that was in the back of my head to look at for a while but never took the time. To me it makes all these discussions, not to mention the concept of 4, 5, 6 figure speaker cables rather foolish. Given the electromechanical nature of the drivers, it could be difficult to measure the electrical resistance of the driver(s) in circuit during operation. Perhaps as an academic exercise you could limit the frequency of the incoming signal to say 50 or 60 Hz, and then use a small DC stimulus to measure the DC resistance. You would be severely response limited, perhaps 100 millisecond rise time. I expect someone has given this a lot of thought and has a better method. Also interesting about the speaker becoming a different speaker at different driver levels. There was an interesting post on ASR recently where a person was "fixing" a commercial speaker. He did response and impedance measurements at multiple drive levels. There were some significant differences, though less after his changes. You are convincing me more and more that active is the way to go long term. |
The 127dB info only served to prove that eff. + extension is readily possible. I wouldn’t dream of using the max. potential in my home environment, but headroom is your friend, not least in LF, and thus the max. SPL numbers should make more sense in this context. Operating the amps much below full tilt is also worthwhile headroom, I might add.
But more wattage in low eff. speakers comes with a price eventually, as per Duke’s post just above.
Quality wattage where it matters most, and power quantity (and overall quality) ditto; I use 30W class A from ~600Hz on up, ~2kW from ~85 to 600Hz, and 500W below ~85Hz. The pro class D-based amps used below 600Hz are quality amps and more than sufficient for the respective frequency spans - that's one of the beauties of active config. that such a distribution of amp types is possible. |
Phusis I think your post makes my point. Efficiency alone is not the sole issue or a spec to chase. Amp power, purpose and many other factors matter a lot. In live sound, 127dB SPL is important. In home audio, its damaging to our hearing. |
@lonemountain , I don’t follow your reasoning. You said: "So your 102dB 1w/1m speaker may not have such good dynamics with a 20W amp if 1W= 102dB SPL then .2W=105, 4W =108, 8W =111, 16W=114dB SPL and that’s it! That’s 12dB of dynamic range. "86dB 1w/1m, 89dB 2w, 92dB 4w. 95dB 8w, 98dB 16W, 101dB 32W, 104dB 64W, 107dB 128W, 110dB SPL at 256W/1m. 86dB 1/1m speaker on a 250W/ch amp = 24dB of dynamic range! 12dB dynamics is better than 24dB dynamics?" The dynamic range of a system is the difference between the softest and the loudest sounds the system can produce. Assuming both systems are limited by the same noise floor, the 102 dB system is capable of 114 dB peaks while the 86 dB system is capable of 110 dB peaks. So in your example, the 102 dB system has 4 dB more dynamic range. But that’s not the whole story. Making another comparison and using 110 dB SPL for both, the 102 dB system will have negligible compression effects from the 7 watts it needs (this may not be true if it’s a single fullrange driver), while at 110 dB/256 watts the 86 dB speaker is far more likely to have thermal compression effects. And since musicians use dynamic contrast to convey emotion, compression effects tend to rob the music of emotion and "life". The use of very high-quality drivers (and/or many drivers) in the 86 dB speaker does make a worthwhile improvement in this area. Let’s revisit noise floor for a moment: To a crude first approximation the in-room reflection field can be thought of as a "noise floor" which can mask low-level sounds. For a given room, the narrower the loudspeaker’s radiation pattern, the higher the direct-to-reverberant sound ratio, and therefore the lower the "noise floor" imposed by the in-room reflection field. So IF our 102 dB speaker is also highly directional (which is likely), it will probably result in a lower effective "noise floor" and correspondingly greater dynamic range and may result in better retrieval of low-level details. Edit: Looks like several of us were typing at the same time, and I was the slowest. Duke |
Duke, nice post on thermal/mechanical driver compression. It’s an esoteric topic, but almost every transducer designer has to come to terms with what steps to take in their driver design to cope with heat, bandwidth, efficiency and intended performance. I know the ATC driver designs are remarkable, such as short coil/long gap, in lowering distortion while maintaining a wide dynamic range. Some of the live sound driver designs these days are insanely good. |
That’s a matter of size, not that you can’t mate efficiency with extension on principle. My tapped horn subs 97dB sensitive and will do ~127dB’s at the tune, which is 22Hz. 20cf. volume per cab - that’s (one of the reasons) why.
Why would you limit the power to 20W for this example? Only suits your argument. I have a 97 to 111dB sensitive subs to main speaker setup powered actively by ~2.5kW total - problem solved.
That's being creative. Not only will you have to deal with peak power compression effects here but long term power compression as well, which in effect limits the available dynamic bandwidth. May look good on paper, but.. |
@audiokinesis, Bravo! |
I know Doug Button, one of the brilliant engineers of the late 80s and 90s who led us to a series of higher output JBL drivers called "vented gap" which enabled dissipating higher heat which enabled higher SPL (and more reliable live sound systems with fewer boxes producing the same output). These were no home hifi drivers, but Live Sound drivers. This whole efficiency argument is twisted by marketing. If you ask a designer like Billy Woodman at ATC (who is on Dougs level), he will tell you if you want additional low end from a driver, you can optimize it for more bass but the efficiency will decline. So a lower efficiency driver may have a better performance from a bandwidth perspective and may indeed be desirable. This is what folks like ATC and B+W and Magico do to get superior bandwidth. Its a choice, not a mistake; this choice does not improve or decrease dynamics- the size amp you mate it with does. Its the combination of efficiency and power handling of the driver that determine dynamic range. So your 102dB 1w/1m speaker may not have such good dynamics with a 20W amp if 1W= 102dB SPL then .2W=105, 4W =108, 8W =111, 16W=114dB SPL and we are out of [low distortion] power. That’s 12dB of dynamic range! That's not even equal to the dynamics of vinyl. So now compare a speaker with 86dB 1w/1m: 2W = 89dB, 4W = 92dB, 8W=95dB, 16W = 98dB, 32W =101dB, 64W=104dB, 128W= 107dB, 256W = 110dB SPL! So the 86dB 1/1m speaker on a 250W/ch amp has 24dB of dynamic range! That's a huge increase when you take into account the log level nature of dB SPL, ideas such as 10dB SPL is considered twice as loud. 12dB dynamics is never better than 24dB dynamics, under any measurement or circumstance. Don’t drink the high efficiency kool aid kids! Brad
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There are multiple mechanisms by which powert compression can occur, and minimizing them just about always favors high-efficiency designs. This will not be a textbook-comprehensive look at the topic, and I will make some generalizations along the way. There are two main types of thermal compression, both originating with voice coil heating, and we’ll come back to them in a minute. Flux modulation is a compression mechanism which occurs because the permanent magnet’s field strength is modulated - temporarily weakened - by interaction with the magnetic field induced in the voice coil by the amplifier signal. For a given SPL, in general the more powerful the motor (and therefore in general the more efficient the speaker) the less the magnetic flux is modulated. Faraday rings in the motor can reduce flux modulation; alnico motors are inherently relatively immune to flux modulation (and neodymium drivers less so); and field-coil motors (electromagnets) are effectively immune to flux modulation (because the perpetual current from the power supply instantaneously restores the magnetic flux). Mechanical compression can also occur as the suspension system becomes non-linear at long excursions, and/or the voice coil exceeds its linear excursion limits. Big drivers are less likely to get into mechanical compression than are small drivers, and since big drivers tend to be more efficient, there is again a correlation between efficiency and low compression. And now for the two types of thermal compression: As the voice coil heats up its resistance rises, and the voice coil in turn heats up the magnet over time, which reduces the magnet’s strength. When the magnet cools back down, its strength returns. Alnico magnets are relatively immune to thermal compression UNLESS they are overheated, and THEN they unfortunately will permanently lose strength. The greater the thermal mass of the voice coil and magnet, the more gradual this heating. And the less wattage required to reach a given SPL, the less heat there is in the first place. Compression due to the magnet heating up and losing strength takes a while to set in, and it takes a while to go away. This topic has been studied because it matters a lot in prosound. Imo the most interesting and audibly significant thermal compression effect arises from the rapid heating of the voice coil due to high-power music transients. This heating is instantaneous. So a 100-watt peak is (to a crude first approximation) like touching the voice coil with a 100-watt soldering iron that transfers heat instantly. So there will be an instantaneous spike in the voice coil’s temperature and resistance, which dissipates fairly quickly to the surrounding air and motor assembly, but the onset is still much faster than the dissipation. What can happen is this: Since the PEAKS are where that instantaneous heating occurs, it is the PEAKS which are compressed the most. We might call this effect "thermal modulation", to distinguish it from the more long-term "thermal compression" which includes the aforementioned reduction in motor strength due to the magnet heating up over time. Unlike thermal compression, "thermal modulation" has not been studied because it’s not a critical factor in prosound (where the financing for such studies usually comes from), and because there is insufficient incentive to finance such a study coming from the consumer audio side. Floyd Toole had this to say on the topic, in a conversation with me on another forum: In other words, the speaker Toole measured had a midrange driver which was subject to significant thermal modulation effects, while the woofer and tweeter were not. So 20 dB crescendos were compressed by 4 dB in the midrange region. Yuck! Years ago Stereophile published an article which supposedly "debunked" the "myth" of thermal modulation. Their measurement procedure was flawed in that they did not sample the voice coil temperature at the instant of peak power, but rather they sampled voice coil temperature at regular time intervals and then averaged the results. So whatever was happening at the peaks was not captured. Anyway as you can probably see, the less wattage required to reach a given sound pressure level, the less thermal modulation effect on the peaks. And also the greater the thermal mass of the voice coil, the less thermal modulation for a given power level. Therefore in general, big, high-efficiency prosound-style drivers have a significant advantage over small, low-efficiency high-end audio drivers in this area. If you have ever heard a speaker whose tonal balance is different at different volume levels, this is probably because the thermal modulation effects are different for the various drivers. The designer has probably "voiced" the speaker to sound best at a particular volume level. Any driver will eventually run into thermal (or mechanical or magnetic) compression issues, but big efficient prosound-style drivers will have similar thermal characteristics over a much wider SPL range, so they are more likely to retain the same tonal balance from very low to very high volume levels. Duke so-called hardcore technical speaker designer |
@deludedaudiophile there is- his name is Duke @audiokinesis |
I agree! See the article below thermal compression Mike
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I would expect though, @atmasphere, that powerful less efficiency speakers have considerably more thermal mass at least, so more thermal transient immunity. I have no feel for their relative ability to dissipate heat though. Certainly they have come a long way. Trying to visualize some of the more advance companies, i.e. Magico, I would expect some reduced sensitivity to power compression from the design of their motor structure and the reduction of inductance effectively taking out a circuit element. I have only given it, now, about 10 minutes thought though :-) .... Is there a hardcore technical speaker designer in the house? |
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@deludedaudiophile Good point and one more problem to add to the list... If the speakers are inefficient, powering them really won't help the dynamic issue. You simply need greater efficiency to get around that. |
