Why? Choosing speakers to buy / avoid based on efficiency is like choosing a new car based on a sole factor such as weight or acceleration. I am not sure if I need to tell you it doesn't make sense. ATC drivers/speakers are one of the most inefficient speakers (around 85dB/w/m) but, with due amplification, I am pretty sure that I do not need to tell you how good they are.
We should reject hard-to-drive speakers more often
Sorry I know this is a bit of a rant, but come on people!!
Too many audiophiles find speakers which are hard to drive and... stick with them!
We need to reject hard-to-drive speakers as being Hi-Fi. Too many of us want our speakers to be as demanding as we are with a glass of wine. "Oh, this speaker sounds great with any amplifier, but this one needs amps that weigh more than my car, so these speakers MUST sound better..."
Speakers which may be discerning of amplifier current delivery are not necessarily any good at all at playing actual music.
That is all.
176 responses Add your response
@jeffrey75 If the amplifier is behaving as a voltage source and the speaker is designed for that (and 99% are) then a flat impedance curve isn’t important, and if you look at the impedance curves of many speakers, you’ll see that most speaker designers don’t value a flat impedance curve.
@jon_5912 As a manufacturer of class D amplifiers I can tell you this statement isn’t correct. The advantage of higher sensitivity combined with higher impedance will always result in lower distortion from the amplifier and the speaker will have greater dynamic contrast owing to less thermal compression in the drivers, plus the speaker will be less critical of speaker cables. Until those three problems are solved easier to drive speakers will have an advantage.
See above. |
@jon_5912 wrote:
And how do they make up for that? There's only so much heat that can be dissipated in a given voice coil, not least a smaller one through typical low sensitivity. Power is power, and the less efficient receiver, unless extremely capable in power handling (which could have other, potentially detrimental effects), always ends up storing more heat, with all that entails. Thermal compression as in actually overheating the VC and causing heavy compression or sending the VC up in smoke is hardly the only, if even the main consequence following here, but rather what happens way earlier as something that has actual, audible effect. The degree to which this is pronounced, and at the (early) juncture this occurs and starts becoming a problem (referencing not least to a higher eff. scenario in which it isn't) would seem to be the more important aspect to investigate here.
I don't see how they do when properly implemented. |
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Let me try to use a better metaphor. It's fine with me if you buy a car that gets 10 MPG. What I disagree with is the awe and bragging rights associated with that. No, your car is not better to ride in or more exclusive than high MPG Cars just because it's low MPG. Also, if you lie about your MPG you should be held accountable. That's my complaint about hard to drive cars. I personally have no stake in high vs. low efficiency. It's the reviewers and machismo that says "Oh, look, my car needs to have 99 Octane fuel to run therefore it's a real sportscar!" that needs to die.
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I still say it’s just different human perceptions of what sounds good I had some 3-way tower speakers that were supposed to be the bees knees- scan speak drivers with Ber. tweets) at around 87db sensitivity (translation more like 84 db) Same thing, comments on how “smooth” or “even” they sounded… Every time I tried to turn them up loud for a more live concert experience (rarely), they always seemed to fart out (probably the thermal compression mentioned) Im talking loud as hell here (balls out) for just a song or two.
My floor to ceiling line arrays do seem to get there db wise, but still sound smoothed to hell in terms of dynamics Only thing I really like about em is their uniform loudness wether listening close or far (they don’t blow your head off up close, or fade way off if far away…)
As always.…YMMV |
In the opening, the OP said out loud that "We need to reject hard-to-drive speakers as being Hi-Fi". Now the tone was evolved to "... It's fine with me if you buy a car that gets 10 MPG. What I disagree with is the awe and bragging rights associated with that..." and followed by "No, your car is not better to ride in or more exclusive than high MPG Cars just because it's low MPG." In reality, in the hi-fi world, I think very few audiophiles (if there is any) will procure speakers just because it's low efficiency. The speaker designed to have lower efficiency has its good reason. Take ATC speaker/driver as an example, if one desires a good low frequency extension out of a small-to-medium sealed enclosure (which I prefer) design speaker with a given size of driver, efficiency has to be sacrificed. Manufactures/designers could achieve higher efficiency by utilizing vented enclosure like tube/flat ports, lighter material for moving parts, horns, etc., but the sound reproduced from those designs may not suit some audiophiles' taste. In addition, quoted from the ATC designer, "The low mass parts are often not suited to the forces and resonances generated when reproducing audio at high SPLs and the structures that behave well at low levels can become unstable. When the driver was reinforced for its stability and high internal damping, reduced sensitivity is unfortunately a trade-off.
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It is really hard to get nuance across in a single sentence so I really am happy when readers take the time to digest the entire paragraph. Of course no one types things perfectly, and hard thoughts often require multiple drafts to craft well. My apologies for the confusion but overall I stand by the entire paragraph, as a whole:
I realize that there are technological marvels which may be very hard to drive because of the way they are stretching the state of the art. The legendary Apogee ribbon speakers are probably the best example I know of at 1 Ohm resistive, and if that’s your thing go get some. My complaint is more about the machismo that hard to drive speakers are naturally better sounding, and more hi-fi than speakers which meet their spec, and stay at 4 Ohms or higher. Of course there are great sounding but hard-to-drive speakers as well. I’d also like to point out that there’s a sub-thread here about high efficiency speakers which is not mine, I take no responsibility for those statements regarding efficiency vs. sound quality. |
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@jeffrey75 I don’t think Wilson is doing what you’re suggesting, if that’s what you mean by ’off base’.
@lanx0003 While this is certainly true, what about large multi-driver full range speakers that are really hard to drive? They don’t get the Murphy that a smaller speaker does for low efficiency. I might see this a bit differently because our ears hear on a logarithmic curve. I figure if 100 Watts won’t do the job, 200 or 400 Watts won’t either because 2 or 4x more power isn’t that much louder- 3 or 6dB. To get to a perceived ’twice as loud’ its generally accepted that you need 10x more power. In radio parlance this is known as ’gold plated deciBels’; 1000Watts, I think we can all agree, simply isn’t practical. |
Fortunately for we humans, distortion of lower frequencies isn’t as audible/objectionable to our ear/brain mechanism as is distortion of higher frequencies. Right, Ralph? Since the beginning of hi-fi and continuing to this day, woofers commonly produce 10% (and higher) harmonic distortion. If a tweeter produced that much distortion it would be unlistenable. If only @kenjit would put into production one of his perfect loudspeaker designs. The selfish sob is keeping them all to himself. |
@bdp24.... What if a few of us got together to try to design a speaker, we all liked.......This is the thing, and it is ok. We each like what we like, without need to defend why. Unfortunately, many are still searching for that " perfect sound forever ". And Eric, I meant zero offense. We all just need to lighten up a little. My best, always, MrD.. |
@atmasphere thank you, speakers designers can flatten out higher impedance in 4 Ohm speakers not sure how I got it mixed up. |
@bdp24 I have no idea what was said by kenjit, as I pass him over when reading. My point was, there is no ONE speaker for all of us, let alone a perfect one. Sorry if I was vague in my communication of that point. |
WRONG. Of course there is a perfect one. Why shouldn't there be? The perfect speaker is by definition one that satisfies all of us. We must stop creating imperfect speakers and start aiming for perfection. Also perfect speakers require perfect audiophiles. Some audiophiles dont WANT perfection. That is a completely different issue. I am one of the finest tuners in the industry. I have never met anybody who is as obsessed. |
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“I’d also like to point out that there’s a sub-thread here about high efficiency speakers which is not mine, I take no responsibility for those statements regarding efficiency vs. sound quality.” @erik_squires With your post headline I’m not sure how you would expect anything else here on Audiogon. We’re a subjective bunch, often ignoring objective facts about “why we should reject hard to drive speakers more often “ Perhaps “bragging rights” with cost or watts? Nothing is more disappointing than too spend a small fortune on “hard to drive speakers” and mega watt amps only to come away disappointed or longing for something that seems missing. So getting back to my point (or highjacking). Personally, trying to use and/or enjoy “hard to drive speakers” repeatedly has been a “The Emporers new clothes” thing.
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My experience with ESL's says that this low impedance (1/3rd of an Ohm) in the upper octave is quite noticeable and often pushes owners to beefier solid state amps. |
Thx for the comment. You got me to think a bit while longer but it is definitely worthwhile. I think the answer to that is the so-called Hoffman’s Iron Law that someone more knowledgeable has pointed out. It states that the speaker designer could pick two parameters out of the bass extension, sensitivity, or small cabinet size in any given design, but in doing so it will compromise the third. So extending that notion to your question, you can have efficient larger floorstander containing multiple, larger drivers in combination with cabinet designs to give great bass, small speakers with great bass and low sensitivity that I have craved for, or small highly sensitive speakers that can’t reproduce bass well. |
@jon_5912 Rather than innuendo, could you be specific about ’way worse problems’? If any amplifier is properly designed and operating properly, it will not add dynamic contrast to the signal. The signal itself is the source of dynamic contrast. Loudspeakers only take away from that; if you value dynamic contrast, using a speaker that has the least thermal compression will bring you closer to your goal. In this light, ESLs have the least thermal compression owing to no voice coil at all; a close runner up is higher efficiency loudspeakers, in particular those that employ field coils (since the magnetic field in an electro-magnetic loudspeaker does not sag when current is applied to the voice coil). Some argue that SETs are the most ’dynamic’ of all amplifiers, but if you use a sound level pressure meter you find out that isn’t true- its really distortion on the leading edge of transients interacting with the way the ear perceives loudness that causes this impression. Amplifiers cannot ’make up the difference’ in terms of dynamic contrast.
@erik_squires FWIW, about 90% of our MA-2 (a 220Watt class A triode OTL) production are running on Sound Lab ESLs. Tubes work quite well with ESL57s, ESL63s and ESL98s. Most solid state amps behave as a voltage source and since ESLs in general tend to have an impedance curve that varies by about 9:1 or 10:1 from the bass region to the highs, quite often a voltage source will sound bright as the amp doubles its output again and again as frequency is increased. For this reason, some ESL producers make their speakers low impedance in the bass and nearly a dead short in the highs, limiting the ability of the amp to drive the higher frequencies (partly due to the speaker cable impedance becoming a significant portion of the source impedance). Even then, brightness is an ever-present danger with such amps, particularly if they have distortion rising with frequency.
@lanx0003 Exactly!
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@atmasphere - I'm trying hard not to use absolutes. I'm sure your amps do fine! Rather, I think ESL's bring a lot of other qualities to the listening experience which makes us swant to overlook the hard to drive aspect. We buy ESL's in spite of the low impedance, not because of it. |
So far nothing perfect has ever been found by humans in this Universe and from my understanding of physics if it did exist all molecules in our universe would be equally distributed thus we wouldn't exist. It's all variables and compromises in any human endeavor these perfect loudspeakers could never exist since perfection itself doesn't exist. As far as rejecting lower eff that's more of a taste and experience or bias issue hi- eff low- eff most can have a good system built around them if you embrace strengths and mitigate known issues. If one wants dynamics, large image size, great transient response, and the ability to run off lower power but can accept a bit of size, different appearance from audiophile standards and can handle the limited market options or you can DIY, Hi Eff would be the logical choice. If you want what almost all audiophiles use and approve of, like to have many easy-to-source options, enjoy large power or need a small speaker. Low-Eff may be the best choice for you. There are still loudspeakers that are neither low or high eff those also may be worth checking out if you feel you want a bit of both worlds. |
speakers make the sound we hear in our rooms... and wonderful sound is what we are striving for in our rooms speakers should be evaluated when performing at their best, which is properly set up in room, driven by a suitable amp to get peak performance (or something very close to it) from them efficiency of the speaker, and the requisite amp, are all part of the tradeoffs to get the sound we really want all others things equal, yes, easy to drive, efficient speakers are nice to have... but it is foremost about the sound... that is the big dog that wags the tail of efficiency and amplification |
@atmasphere wrote:
Which only gets you so far being ESL's have the lesser macro-dynamic range compared to horns/high efficiency designs, unless extremely (unrealistically?) large and rid of bass signals. Before thermal compression would ever become an issue with horns, other potential factors like horn material resonance and truncated horn size in the midbass horn in particular would be the primary concerns. While ESL's don't compress per se - and as such some of their implementations can have an advantage over low eff. direct radiating, dynamic driver designs - it's well known that when they limit out they do so abruptly, not least when applied full-range. |
Technically Atmasphere is correct, they use the aluminum panel as the voice coil, and they still use magnets. I highly doubt that apogee's suffer from thermal compression, the area is much larger to dissipate heat. I listened to a pair of Diva's that were driven by over 2,000 watts and they had effortless dynamics. |
That’s just it. They are a panel, not a coil. There’s no "coil" there. They are however electromagnetic instead of electrostatic. In addition, the very large size and direct exposure to ambient temperature makes them behave in an entirely different manner thermally than a tightly wound coil in limited distance between round magnets. I’m going to go with the Wikipedia article, that specifically calls a voice coil as consisting of a former, collar and winding, as proving these speakers have no voice coil to speak of. Even if they did, the reasons for thermal compression in actual voice coil speakers can't possibly apply here. |
Hence my use of the word 'possible'... In the case of a magnetic panel speaker like the Apogee, the 'voice coil' for lack of a better term can be heated. It seems to me that would take some power. If it heats, then less current can be applied because the impedance is higher. That's what causes thermal compression. The thing about thermal compression is that it can happen with individual bass notes; IOW the 'voice coil' is heating and cooling dynamically with the music. If the speaker is using a magnetic principle then this can happen. How much it happens is a different matter. |
While Atmasphere is correct in saying that it is possible to achieve thermal compression in planar-magnetic drivers, in practical terms it really doesn’t happen much, at least not in larger drivers. Being involved with Analysis planar-ribbon speakers for almost 2 decades, I have witnessed some very informative testing. In one test the bass panel was subjected to considerable power at low frequencies to test thermal saturation and the mechanical integrity of the adhesives used. Even beyond its usable max excursion practically no heat was generated (short term). The very thin aluminum foil with considerable surface area is essentially self cooling. This test was extreme. I would not call the planar foil a coil because it’s not, at least not in the case of the Analysis design. Some compression occurs in planar drivers, including ESLs, because the membranes are stretched across a frame. The mechanical impedance is not linear. The greater the excursion the more power is needed. Analysis speakers address this mechanically induced compression by using a rubber surround. The design is quite effective in reducing compression. Other ways around this inherent quality is by using VERY large panels or subwoofers. To the OP, I think people like what they like for a variety of reasons. Some people like large aluminum boxes with tons of power because they think they are cool, others like tube amp with exposed tubes because they think they are cool. Some people are fulfilling their audio dreams from a time before they had the money to buy their dream gear. There are valid arguments for high and low efficiency speakers. There are also trends. Personally I lean toward high efficiency speakers. Our Apollo series OB line array speakers are high efficiency for several practical reasons, mainly because HE speakers always sound much more lively (linear dynamic contract) to me. Live music sounds lively. It’s one of the main elements that creates the experience. We will be showing our Apollo 9s at AXPONA using 300B amps if anyone wants to hear high efficiency OB line arrays.
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That was kind of where I was going with that. 99% of the surface area of the conductor is directly exposed to air, unlike an actual coil where you may have multiple layers of windings or the former acting as insulators.
True for all drivers, except perhaps the massive fan subwoofers. I think the difference in measurement/thinking about thermal compression vs. mechanical is that thermal compression changes the behavior of the speaker in time, sometimes within milliseconds, while mechanical compression is always there, until you blow the driver. :) I do think it’s odd audiophiles have fixated on thermal compression, specifically, as being the only one that matters, though I do agree that higher efficiency drivers seem to be at an advantage here. There’s a reason JBL professional drivers are so expensive, and one of the main reasons that is that they are built specifically to avoid thermal compression even at constant power levels that would make most audiophile systems weep. |
As a mechanical compression artefact this is hardly true for all drivers. Dynamic drivers have suspensions, and the "stretch" of a membrane here wouldn't occur in a way comparable unless the suspension iself is (getting close to being) mechanically edged out.
Question is when, and perhaps not least how thermal compression starts becoming prevalent and an actual audible effect. Thermal 'modulation' may be a better term to explain or correlate what happens sonically; thermal compression impacts SPL envelope and ultimately driver failure, but it also appears to dull transient cleanliness and snap at a much earlier juncture as a very dynamic phenomena.
Other pro brands would do equally well, and at a cheaper price, but yes pro drivers are simply on another level here. |
@phusis Then I’d really like to know what you think happens when your reach the maximum excursion of a driver. Either they have limited excursion, and therefore compression, or they have infinite excursion and no compression. I wish I could find them but I remember seeing tone burst tests showing that thermal compression could happen in a tweeter in less than half a second. You could see the first tone burst perform perfectly, and then half way through the second compression sets in. |
@erik_squires wrote:
That’s indeed what I’m talking about in regards to mechanical compression, but how often do we reach, let alone exceed X-mech? My point is, before that happens the driver’s suspension has a range of motion within which compression per se as a mechanically induced phenomenon isn’t relevant. What’s arguably more relevant mechanically is hysteresis (or magnetically, hysteresis distortion) as that which happens through the range of cone movement, but that’s hardly a compression issue, no? Although: smaller (<10"), low eff. woofers certainly makes their effort in reproducing the range <40Hz at elevated, but hardly prodigious levels be known, and when you’re used to a pair of corner loaded, high eff. tapped horns fitted with 15" pro woofers in 20cf. enclosures where the cones barely more than a few mm’s at bonkers SPL’s, it’s all the more obvious. With smaller hifi woofer cones working hard it’s likely a combo of mechanical noise and -compression, as well as the onset of thermally induced compression.
Interesting; I take it what could also be referred to as thermal modulation as a more dynamic phenomenon. It’s a shame this area isn’t more well documented, leaving us with the more general ’thermal compression’ description and correlation as heat build-up in the voice coils over longer time. |
@phusis I don’t claim to be an expert in all measurements but this seems not to go along with what I’ve seen or measured. At some point significantly below Xmax I believe there begins to appear evidence of compression, both within the FR and distortion. I'm not sure how we could attribute any/all of it to thermal without tone burst testing. Take a look at the SoundStage speaker measurements, just about any of them, since they are the only mag I know of that takes compression measurements regularly. |
This thread got seriously above my IQ this page, I've been able to play in waters previously too deep because my family took care of me in their passing and I was living within my means before that. Anyhow I learned the hard way about how dull and lifeless a pair of speakers can sound without enough juice.
Here's where I get confused and I hope somebody can explain it in simple terms. Why does huge power matter when I'm listening between .5-5 watts? My speakers sounded dull and lifeless until I turned the volume past 90 db so I swap out my 300wpc and replace with a couple mc 611's and suddenly low volumes sound dynamic? Shouldn't any amp have power to spare at 1 watt? I've shipped several very highly regarded speakers out because 250 wpc wasn't enough to 'wake them up'. I only mentioned the mac model because IDK if output transformers on a SS amp are a factor in my question. |
@erik_squires Wrote:
100% correct! See articles below: Power compression Vs Thermal distortion in loudspeaker drivers: Mike https://www.linkedin.com/pulse/power-compression-vs-thermal-distortion-loudspeaker-alexander-wilson/
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this may help... ... also don't confuse input sensitivity of an amplifier with its power output
I watched the video, not sure PM did the job of explaining the difference between the quality of a Cambridge audio watt vs the BHK. How would somebody confuse power output with input sensitivity or is input sensitivity a possible reason for the low volume differences I'm hearing? |
@steve59 Wrote:
Maybe this will help. Why is the first watt important? See below: Mike |
Typically, speakers respond to the amount of current available…. Basically the number of electrons instantaneously available when a bass note comes along. Watts does not measure this. Amps do. I remember getting my first truly high powered amp it was 250 wpc… but could put out around 4 amps… that was roughly what my arc welder put out at work. When you have that much power in your amp, it just grabs your speaker and says…”do this”, and compliance is mandatory. It does it. |
