"Inefficient" speakers are "worse" than "efficient" speakers

[Luvchampagne]

A common complaint by ASR members is that so called "inefficient" speakers, 85db or lower sensitivity for 2.83v at 1M, are inferior to efficient speakers, 90db or higher sensitivity. I find this complaint difficult to understand from an objective and scientific viewpoint, especially with amplifier power being relatively inexpensive these days.
1. Inefficient speakers perform poorly at low volumes. Can someone explain this concept since it makes zero sense to me.
A side question would be more in general, the concept of why certain speakers perform better at lower volumes than other speakers at the same volume. What science is behind that?

2. Inefficient speakers are poorly designed. I can actually understand this comment if there are no benefits to the inefficient design such as poor bass response. Otherwise, isn't speaker design, a series of tradeoffs to obtain a result? Size of cabinet. Bass response. SPL capability. What am I missing?

3. Side question - why do some people convert sensitivity level measured at 2.83v at 1M into different sensitivity level based on impedance? Example - 85db at 2.83v at 1M converted to 82db at 4 ohms. How is this conversion useful?

4. Is this just a preference due to already owning lower power amplifiers? If so, I get that. But that has little to do with better or inferior.

Thank you in advance.

 

[Heinrich]

1. Inefficient speakers perform poorly at low volumes. Can someone explain this concept since it makes zero sense to me.

Zero is true, because 'poorly' is not defined, neither is 'low volume'. It may go back to times when high distortion was not only the rule, but was likewise expected to spice-up the playback together with a roller-coaster amplitude response, loops included.
WIth the advent of more sophisticated designs, BBC, KEF in the following, the cone's damping, sacrificing efficiency for linearity, came into focus. In parallel a decent bass extension, that always relates to size and, conversely, to efficiency.

It is said even today that studio monitors are not for 'sound', too sterile, lifeless etc. It could be argued, hence, that 'poorly' means good?

2. Inefficient speakers are poorly designed. I can actually understand this comment if there are no benefits to the inefficient design such as poor bass response. Otherwise, isn't speaker design, a series of tradeoffs to obtain a result? Size of cabinet. Bass response. SPL capability. What am I missing?

No, there's a tradeoff many hifi buffs don't understand. You're missing how mislead some guys are, full of doubt but still buying new gear every other day. For instance, restricted bass extension follows high efficiency given the same box size (and vice versa). The bass is determined by some 'iron law' (Hoffman?), and so is the relation of bass to the mids: size vs/ extension vs/ efficiency. That applies even to actives with equalisation, if efficiency is taken as a technical term, which is quite rarely the case; see below.

3. Side question - why do some people convert sensitivity level measured at 2.83v at 1M into different sensitivity level based on impedance? Example - 85db at 2.83v at 1M converted to 82db at 4 ohms. How is this conversion useful?

Because they can using elementary school calculations?

 

[kemmler3D]

Not sure where you have heard these objections to inefficient speakers, (I think they're incorrect) but generally speaking low efficiency is a trade off for some other aspect of sound quality. It can mean you have to spend more on your amp to hit the desired SPL, but it doesn't imply the sound quality is worse.

 

[DanielT]

....
2. Inefficient speakers are poorly designed. I can actually understand this comment if there are no benefits to the inefficient design such as poor bass response. Otherwise, isn't speaker design, a series of tradeoffs to obtain a result? Size of cabinet. Bass response. SPL capability. What am I missing?
...

It can almost be seen as the opposite. To get a nice even FR, it may be necessary to "sacrifice" a few dB in sensitivity.

As long as the speaker has decent power handling (likes, tastes and needs of what this decent level is) so you can play at a decent high volume without it sounding bad/distorting, it doesn't matter if the speaker has low efficiency.

Good amp power at a good price is now available on tap so you don't have to worry about that.

Also high-efficiency speakers. Let's say a fairly modest level of at least 92 dB sensitivity, how many good ones do you see? Has Amir even tested any such passive speakers? Has Erin tested any such?
Suggestions for GOOD high efficiency speakers (sensible FR among other things), that question comes up every now and then here on ASR. Often when someone who has a low powered vintage amp/receiver or an old/new low powered tube amp and wants to pair the receiver/amp with speakers. There are usually few suggestions.

Then we have active speakers where there is no mention of sensitivity but levels of SPL in combo when distortion/compression kicks in (as mentioned important even for passive speakers).

 

[dfuller]

1. Inefficient speakers perform poorly at low volumes. Can someone explain this concept since it makes zero sense to me.
A side question would be more in general, the concept of why certain speakers perform better at lower volumes than other speakers at the same volume. What science is behind that?

Not true. They just need more power to get to the same level as more sensitive speakers.

2. Inefficient speakers are poorly designed. I can actually understand this comment if there are no benefits to the inefficient design such as poor bass response. Otherwise, isn't speaker design, a series of tradeoffs to obtain a result? Size of cabinet. Bass response. SPL capability. What am I missing?

Not poorly designed. This is nonsense also. Hoffman's Iron Law applies - sensitivity (SPL handling, in actives), LFX, size. Pick two at the expense of the third.

3. Side question - why do some people convert sensitivity level measured at 2.83v at 1M into different sensitivity level based on impedance? Example - 85db at 2.83v at 1M converted to 82db at 4 ohms. How is this conversion useful?

Because it's comparing watt-for-watt. 2.83V AC RMS = ~1W of power into an 8R resistive load. A nominal 4 ohm speaker measured at 2.83V is actually being measured at 2 watts, not 1. Not all amps can "double down".

The big thing about sensitivity/efficiency is this: pumping more power in to get to a given SPL = you're more likely to have thermal compression effects become audible. A speaker that is 82dB/W @1m needs around 20 watts to do 96dB/1m (which is, at least in the bass region, not nearly as loud as one would think), one rated for 88dB/W @1m needs about 5. This isn't a given - good designs get around this with high quality drivers with better cooling capabilities- but it's definitely not an impossibility.

 

[DVDdoug]

There are LOTs of trade-offs & compromises.

Sometimes you lose sound quality to gain efficiency/ sensitivity.

In these "modern times" when amplifier power is cheap, speaker manufacturers don't have to worry too much about sensitivity and they can trade it off for other things.

There also often a trade-off between box size and sensitivity, with larger boxes allowing for more sensitivity.

Ported designs tend to be more efficient than sealed boxes. If you have a small (smallish) subwoofer you can often get sufficient bass with EQ and amplifier power.

Pro subs used live and in dance clubs are usually very efficient ported designs with big drivers in big boxes. They are also usually "tuned" to go down to around 40Hz, which is low-enough to feel in your body. By not going down to 20Hz, they can squeeze more efficiency and SPL out of it.

When I was young I helped to install a pair of Altec A7's in a school theater. I think we were testing them with a 5 or 10 Watt amplifier. The "sound power" was amazing and it was like you could feel the efficiency! They seemed to go "loud easily". ...Technically, that's nonsense if you're not measuring the power or A/B comparing to another speaker but that was my impression. I don't think they "measure" that great, but at the time they sounded great to me... probably the best speakers I'd ever heard at that time, and I still have fond memories!

Horn PA speakers can be super-efficient but they usually don't make good "music speakers". A quick search found this one which is rated for 107dB at 1W/1M.

 

[bmc0]

1. Inefficient speakers perform poorly at low volumes. Can someone explain this concept since it makes zero sense to me.

This impression may be based on the fact that a lot of high(er) efficiency speakers have somewhat hyped treble and/or midbass response (many Klipsch speakers, for example). Of course, this is just false attribution as it isn't an inherent consequence of high efficiency.

2. Inefficient speakers are poorly designed. I can actually understand this comment if there are no benefits to the inefficient design such as poor bass response. Otherwise, isn't speaker design, a series of tradeoffs to obtain a result? Size of cabinet. Bass response. SPL capability. What am I missing?

Nothing really.

3. Side question - why do some people convert sensitivity level measured at 2.83v at 1M into different sensitivity level based on impedance? Example - 85db at 2.83v at 1M converted to 82db at 4 ohms. How is this conversion useful?

Sensitivity and efficiency are related, but not interchangeable. Sensitivity (more specifically, voltage sensitivity) is the SPL for a given input voltage. Efficiency (in this context) is the SPL for a given nominal[1] input power. 2.83V RMS into an 8 ohm resistive load results in an average power dissipation of 1W, which is why that particular voltage is commonly used. For 4 ohms, 1W is 2V RMS (3 dB less).

[1]: "Nominal" because speakers virtually never have the same impedance at all frequencies. Standard convention is to use a voltage that corresponds to 1W power dissipation into a resistive load equal to the stated nominal impedance of the system. Efficiency ratings for speakers are thus usually just voltage sensitivity where the voltage is based on the nominal impedance. P=V²/R, so if P=1W, V=sqrt(R), where R is the nominal impedance.

Also high-efficiency speakers. Let's say a fairly modest level of at least 92 dB sensitivity, how many good ones do you see? Has Amir even tested any such passive speakers? Has Erin tested any such?

The JBL 4367 is one (of very few).

 

[DanielT]

The JBL 4367 is one (of very few).

Heco has used a lot of acoustic tricks to get a good speaker with relatively high sensitivity with the Direkt model. Not super high sensitivity but still decent. Fairly large box volume. Or rather with the box volume of the speaker they have used it well in terms of design; wide baffle, the port directed towards the floor.
With the intention to get good FR in combination with relatively high sensitivity:
Sensitivity 93 dB (2,83 V / 1m; 500-5.000 Hz):

Heco Direkt 2-way measurement interpretation request / should I buy?

Hello, maybe somewhat of an odd thread but is there anyone willing to give me a short rundown regarding the measurements linked below? Are these speakers measurements within an acceptable range? They are available for 1400€/pair in Germany online and would fit my space quite nicely. The German...

audiosciencereview.com

It seems to be a popular design because now they have come up with the premium model:

 

[staticV3]

A side question would be more in general, the concept of why certain speakers perform better at lower volumes than other speakers at the same volume. What science is behind that?

IMO, a combination of house sounds and equal loudness contours.

If they happen to match up for a low playback volume, then the speaker is labeled good for low volume listening.

It's often showroom-tuned speakers which in the long run sound piercing and annoying at normal volumes, but can sound quite nice when turned down, simply because their tuning happens to coincide with equal loudness compensation.

 

[Arindal]

A side question would be more in general, the concept of why certain speakers perform better at lower volumes than other speakers at the same volume. What science is behind that?

Cannot provide you with solid scientific findings, but from technical point there are aspects like compression, expansion and resonance decay depending on the SPL, while the psychoacoustical effects of masking are at play. Admittingly a pretty theoretical explanation, but whenever one is experiencing ´lost bass´ at lower SPL or reduced treble details, masking is the first thing that comes to mind.

Inefficient speakers perform poorly at low volumes. Can someone explain this concept since it makes zero sense to me.

It makes zero sense. Other people claim amplifiers are performing poorly when producing less power, which would actually call for low-efficiency speakers.

This impression may be based on the fact that a lot of high(er) efficiency speakers have somewhat hyped treble and/or midbass response

Would suggest another explanation: many high-efficiency speakers are also narrow-directivity speakers, that is what is actually driving up their efficiency (like horns or big midrange/fullrange cones). The impression of ´wow, that sounds pretty dynamic, impulsive, lively´ might be rather an outcome of reduced levels of reverb in this case.

 

[ChrisG]

Just a passing note that, all else being equal, a loudspeaker motor dissipating 10s of Watts will have higher harmonic distortion than a motor dissipating <1W.


Further, higher-efficiency speakers tend to use larger diaphragms, typically resulting in narrower directivity, which puts a huge confounding variable on top of the thing we're actually trying to discuss.

Has anyone made an 18" 4-way speaker with the same directivity as a 4" 2-way?
I think that would be an interesting comparison.


Chris

 

[Matias]

I chose my current speaker March Audio Sointuva AWG knowing well it has way below average sensitivity, but excellent low bass extension and the best linearity (see here). My amp can drive 700W at 4/2 ohms (NCx500), so that is one trade off I have no problem with.

 

[raindance]

Substitute the word "different" for better or for worse and the premise holds up. Chuckle.

 

[DanielT]

Then there are the speaker manufacturers who exaggerate their sensitivity figures, as Erin addresses in the video below:

 

[Looneybomber]

3. Side question - why do some people convert sensitivity level measured at 2.83v at 1M into different sensitivity level based on impedance? Example - 85db at 2.83v at 1M converted to 82db at 4 ohms. How is this conversion useful?
Thank you in advance.

Most likely, 85db/2.83v (the new measurement standard) would be 82db/1W at 8 ohms (old standard) since most speakers are 4 ohms despite the arbitrary 8ohm spec manufacturers give them.

I find it useful since so many speakers are getting lower in impedance to boost their 2.83v sensitivity…which increases sales. On the surface they seem to be efficient (db output per input power) until I see the impedance sweep shows dips will below 4ohm and perhaps rarely go above 8 ohms.

 

[egellings]

You can have small size. The speaker can go very low in bass frequencies. It can go loud. You can have any two of those three.

 

[MattHooper]

A common complaint by ASR members is that so called "inefficient" speakers, 85db or lower sensitivity for 2.83v at 1M, are inferior to efficient speakers, 90db or higher sensitivity. I find this complaint difficult to understand from an objective and scientific viewpoint, especially with amplifier power being relatively inexpensive these days.
1. Inefficient speakers perform poorly at low volumes. Can someone explain this concept since it makes zero sense to me.
A side question would be more in general, the concept of why certain speakers perform better at lower volumes than other speakers at the same volume. What science is behind that?

2. Inefficient speakers are poorly designed. I can actually understand this comment if there are no benefits to the inefficient design such as poor bass response. Otherwise, isn't speaker design, a series of tradeoffs to obtain a result? Size of cabinet. Bass response. SPL capability. What am I missing?

3. Side question - why do some people convert sensitivity level measured at 2.83v at 1M into different sensitivity level based on impedance? Example - 85db at 2.83v at 1M converted to 82db at 4 ohms. How is this conversion useful?

4. Is this just a preference due to already owning lower power amplifiers? If so, I get that. But that has little to do with better or inferior.

Thank you in advance.

I’m not sure where you’re getting this from ASR. Those sound much more like the claims you hear outside ASR from the golden ear crowd.

Is the type of stuff that fuels high sensitivity
“ low crossover count” speaker and low wattage tube systems.

I remember “ back in the day “ lots of the claims about low efficiency speakers or hard to drive speaker sounding lifeless or lacking clarity, and for me, it was in particular Thiel loudspeakers that put that to rest.

They were notoriously complex with crossover parts as well as notoriously, low sensitivity and hard to drive. And yet I found that they sounded particularly clear and detailed as well as dynamically life-like.
So I’ve never worried about such stuff.

I will say that… yes… I have perceived really high sensitivity designs like some horn designs as sounding very dynamic and lifelike. So there might be something to the high sensitivity thing. But ultimately, I think it just comes down to how a speaker is engineered.

 

[FrantzM]

Then there are the speaker manufacturers who exaggerate their sensitivity figures, as Erin addresses in the video below:

Great Picture from those who remember him .. and similar..
Hope his business doesn't sue Erin...

This seems to be all the rage these days..

Peace

 

[Chris A]

1. Inefficient speakers perform poorly at low volumes. Can someone explain this concept since it makes zero sense to me.
A side question would be more in general, the concept of why certain speakers perform better at lower volumes than other speakers at the same volume. What science is behind that?

This is typically poorly explained and not really asked about in hi-fi circles: measurement of threshold or minimum output signal levels from drivers and loudspeakers. It has been anecdotally noted by many listeners that inefficient/low sensitivity loudspeakers experience a loss of detail at very low signal levels.

These effects can be assigned to hysteresis effects in the cone and dome-type driver magnetic circuits of low efficiency/sensitivity drivers (especially woofers) and the effects of "stiction" in acoustic driver design, but, to date, I've not really seen a paper on that subject--even from Klippel.

However, I am aware that low sensitivity drivers are subject to a host of ills that higher efficiency drivers basically do not experience (due to their lower diaphragm displacements to achieve the same on-axis SPL). Micro-air leaks in lower efficiency acoustic drivers is another source that disproportionately affect lower sensitivity designs in terms of threshold output performance.

2. Inefficient speakers are poorly designed.

I don't believe this is a correct statement, to be honest. Many esoteric loudspeaker designs are of very low sensitivity/efficiency, such as electrostatic and Magnepan-like dynamic membrane loudspeakers. I think the problem isn't design quality--but perhaps a lower general understanding of why higher efficiency/sensitivity designs turn out to be otherwise superior in terms of an assortment of performance areas--that are not often discussed on forums like this.

Here is the problem with lower sensitivity loudspeakers (from Toole, 1st Ed.):

Note the assumed sensitivity of this loudspeaker for this figure is ~88 dB/(1m-1w). Note also the amount of power required to reach even 100 dB (over 10 w). And lastly, note that thermal compression distortion will eat up your listening fidelity (compression and intermodulation distortion) at well below "rock concert" levels. From the article that I just linked:

Lets do another quick calculation on how much energy injection is needed to heat up the wire from our first calculation by 100°C – from an ambient 20°C temperature to 120°C...We roughly need only around 1 Watt for 1 sec for each Kelvin temperature increase (no cooling assumed here), looking at the thermal material constants for copper

To heat up this < 3g of copper wire our voice coil is made from, we only need 10 sec of 10W input to finally arrive at a 100°C increase – or – if we have fortissimo playing – a very short 1 sec of 100W input.

Wow – almost as fast a turning on a light bulb !

Klippel also details problems of large signal nonlinearities--all of which stack up against lower sensitivity/efficiency drivers as compared to higher efficiency ones.

It should be noted that intermodulation distortion is ~25 dB lower when using a well-designed acoustic driver with well-designed horn vs. using the same driver in direct radiating fashion (i.e., at the same on-axis SPL)*. (Most everyone misses this point--that high efficiency designs do not experience audible levels of intermodulation distortion.)

A YT video from Klippel describing the sources of intermodulation distortion, all of which are a strong function of diaphragm displacement:

Chris

* see enclosed pdf

 

[Luvchampagne]

This is typically poorly explained and not really asked about in hi-fi circles: measurement of threshold or minimum output signal levels from drivers and loudspeakers. It has been anecdotally noted by many listeners that inefficient/low sensitivity loudspeakers experience a loss of detail at very low signal levels.

I'm glad I'm not the only one that has observed these comments. Not that I think they are valid from an objective and scientific viewpoint, just that they are present in the ASR forums.

These effects can be assigned to hysteresis effects in the cone and dome-type driver magnetic circuits of low efficiency/sensitivity drivers (especially woofers) and the effects of "stiction" in acoustic driver design, but, to date, I've not really seen a paper on that subject--even from Klippel.

However, I am aware that low sensitivity drivers are subject to a host of ills that higher efficiency drivers basically do not experience (due to their lower diaphragm displacements to achieve the same on-axis SPL). Micro-air leaks in lower efficiency acoustic drivers is another source that disproportionately affect lower sensitivity designs in terms of threshold output performance.

Are you referring to poorly designed drivers that are inefficient? If so, that is not my question. I was taking a generalized opinion and asking the basis for that. Do you believe your opinion is valid with a well designed lower efficient driver, such as many of the Purifi drivers?

I don't believe this is a correct statement, to be honest. Many esoteric loudspeaker designs are of very low sensitivity/efficiency, such as electrostatic and Magnepan-like dynamic membrane loudspeakers. I think the problem isn't design quality--but perhaps a lower general understanding of why higher efficiency/sensitivity designs turn out to be otherwise superior in terms of an assortment of performance areas--that are not often discussed on forums like this.

As other members have commented, IMHO well performing higher efficiency/sensitivity designs, in general, DO NOT measure superior to well designed less efficient speakers. Obviously there are exceptions.

Here is the problem with lower sensitivity loudspeakers (from Toole, 1st Ed.):

Note the assumed sensitivity of this loudspeaker for this figure is ~88 dB/(1m-1w). Note also the amount of power required to reach even 100 dB (over 10 w). And lastly, note that thermal compression distortion will eat up your listening fidelity (compression and intermodulation distortion) at well below "rock concert" levels. From the article that I just linked:

Again, for well designed lower efficient drivers, such as Purifi drivers, IMHO that this is incorrect. IMHO, Dr. Toole's summary does not apply to that. His summary is based on an "all else being equal" comparison. That would beg the question of why make an inefficient speaker design without some type of benefit, e.g., poor design.

Klippel also details problems of large signal nonlinearities--all of which stack up against lower sensitivity/efficiency drivers as compared to higher efficiency ones.

It should be noted that intermodulation distortion is ~25 dB lower when using a well-designed acoustic driver with well-designed horn vs. using the same driver in direct radiating fashion (i.e., at the same on-axis SPL)*. (Most everyone misses this point--that high efficiency designs do not experience audible levels of intermodulation distortion.)

Chris

* see enclosed pdf

Thank you very much for your response. This is exactly the opinion I was hoping to see. It is my understanding, that in a well designed lower efficient speaker, none of your concerns apply. If you take a poorly designed inefficient speaker with mediocre drivers, then your concerns are valid.
Obviously, I am not any kind of expert, just an above average enthusiast for audio equipment and reproduction.