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

[Mike123]

I love inefficient speakers because the noise-floor is much lower with the same amp. This actually makes them perfect for near-field use, or in quieter environments.

Maybe it would be better to install a normal amplifier that doesn't make noise even on sensitive speakers?

 

[Keith_W]

I would have thought it would be pretty simple. Inefficient speakers need more amplifier power to produce the same SPL. If you pump all that wattage into a driver, a lot of that gets converted to heat. And too much heat build-up leads to nonlinearities like dynamic compression and distortion.

 

[Arindal]

And too much heat build-up leads to nonlinearities like dynamic compression and distortion.

Compression and distortion created only by building up heat internally, sounds like a problem of a pretty compromised driver design. Would associate this problem rather with very compact bass drivers. The question is if it would be possible to increase solely efficiency of that particular driver without changing parameters like diaphragm area, excursion capabilities, equivalent volume or resonance frequency?

 

[olieb]

Yes. The farther the diaphragm moves, the higher the modulation distortion for a given SPL.

While this is correct, this has not much to do with efficiency. For a given SPL the same size diaphragm has to move the same excursion independent of efficiency. You cannot compare 4inch divers to 15inch or (bass) horn speakers and call this a difference in efficiency only.

2) How can you achieve higher sensitivity besides increasing the driver's physical diaphragm area...or the number of windings in its voice coil?

This is an interesting assumption and it shines some light on most of your statements/deductions.
Increasing the diaphragm dimensions will alter the speaker completely to the degree that a comparison becomes quite unreasonable, especially for woofers. You end up comparing 4inch drivers to 15 inch drivers. Apples and beers.
Instead one should compare like for like. So let's stick to direct radiating cone drivers of same size and impedance in a box.
If my algebra is correct this is the formula for (reference) efficiency.

Increasing the efficiency in this case will therefore be mainly an outcome of
- increasing the magnetic field (bigger magnet) [-> higher cost- > higher status -> probably the origin of the myth]
- decreasing the moving mass (lighter diaphragm or shorter voice coil winging)
The result will be a much different outcome regarding differences in distortion.
Using a bigger magnet is the most obvious way to increase efficiency without changing much else and that is exactly it. It will not change much in respect to SQ. But you have to adapt the design of course as Q will be different and that impacts low frequency response. There might be some effects from higher current (to compensate the weaker magnet) like hysteresis and flux modulation though. On the other side the bigger magnet is an obstacle to air flow and will create more reflections on the back,
A lighter diaphragm will have similar effects (more efficiency, lower Q) together with less bass form greater f_0 and maybe a different FR in midrange from a different breakup behaviour. Shorter voice coil winding will probably increase distortion.

So the answer of the OP is - as always - it depends.
As @Mnyb mentioned, many compromises have to be made and that defines the result, not one number.

About thermal compression my opinion is that this is overrated. It is more of a slow effect, no kick drum beat will have less dynamic because the voice coil/magnet heats up during reproduction. Instead a woofer will get warm over time and thereby volume will be slightly reduced (from increase in R and decrease in B). For hi-fi systems with a sound pressure level that does not jeopardise my hearing, this is as good as negligible. (PA or deafening party with low DR music is different.)

And 80dB with 30Hz is NOT too low for a reasonable measurement. Excursion of that small woofer will be a bit over 3mm. If you want more SPL in sub bass you will have to use other drivers for sure.
100dBspl on the other side IS unreasonable as these volumes will put my hearing in danger if sustained for more than fractions of a second once in a while. Therefore it might be less challenging to measure IMD with high SPL, but it is in no way "more realistic". Certainly not for the Purifi driver that would be driven to (rather high) Xmax at 30Hz/90dB.

 

[Marin]

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.

This under number 3 is not clear to me either, and the attached calculator application calculates the change of watts based on the Ohm's entered in the box?
But we all know that speaker is not steady load but dinamic based on Freqvency the amplifier will see different load, for example my Yamaha AVR V-6 is measured by Armim has 120 what's at 8 Ohma.What does that tell me if my speakers are rated at real 6 Ohma (Elac debut 5 tower first edition).
This is really driving me crazy and I have no idea about anything except that my amp drives the speakers the code is made for them and I've never turned them up all the way actually -10db is really loud that I'm afraid the neighbor come storm at my door
For serious listening and enjoyment of music so that all instruments can be heard without "hurting" the ears, I think -17DB on the scale is the right volume for me. I'm interested how loud other Yamaha amplifier users have volume set because they all have the same scale for volume and loudness(processing)?

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.

This third one confuses me too, especially the calculator calculations that change watts as you enter Ohms. in the box

We all know that speakers are a "dynamic load" - as the frequency response changes, the resistance also changes.

 

[Heinrich]

And 80dB with 30Hz is NOT too low ...

80dB is MASSIVE at that frequency. I really "LOL" all the time. What are you all talking about, how far can you go?

High efficiency makes intermodulation because the cone moves more?!? Really? I give myself a break (before the mod chimes in).

 

[DanielT]

A7 "Voice of the Theater" speakers reveal the inverse of Hoffman's Iron Law (btw, Hoffman was Henry Kloss's partner at Advent). If reducing size decreases sensitivity, then increasing size raises it. That's one of the reasons they were large--amps of the day were relatively small. I don't recall the official sensitivity--Google says it's 103-105 dB/W/m--but we used a pair for a country band that could fill a ballroom with deafening sound if they wanted to using a McIntosh amp that may have been 150 WPC.

But the bass reflex cabinet used in the A7 included an exponential horn baffle in front of the woofer, and that projects the sound out front to a greater extent than any home speaker. They would not measure that great, perhaps, in home use simply because of their long-throw horn, though there may be strategies to make them work. But that's not what they were made for.

Rick "different use cases bring different requirements that suggest different tradeoffs" Denney

Then the trick of placing the speakers in the corners via acoustic boost to get higher efficiency/acoustic gain. I googled: "Vintage corner speakers". A lot came up.Perhaps it's not surprising that this was the case. At a time when powerful amplifiers for home use were quite expensive, speakers needed to be efficient. I'm not the first to point out that this is the case, but I was a little surprised by how many different corner-designed speakers there were.

It might also have been an interior design style to place the speakers in the corners, I don't know about that.


In any case, you can try placing your subwoofers in the corners of the listening room. It gives a lot of extra dB boost that you then have to "take off" if you EQ.
A lot more dB actually:
A monitor with a flat frequency response in free space produces up to 6 dB higher sound level when placed against a solid wall. In a corner (two walls) this gain can be 12 dB. With three boundaries (corner close to ceiling) the gain can be +18 dB. This can be particularly seen at low frequencies.

Monitor Placement - Genelec.com

To create the ideal listening experience, several aspects need to be taken into account when placing the monitors within the listening space. First, you need to identify the listening area within the space and consider where the listener will be placed in relation to the space as well as the...

www.genelec.com

 

[Jukka]

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?

In context of a loudspeaker, that makes no sense to me. You cannot change the impedance of a completed speaker, so no point in such conversion, not even when comparing to other speakers. I don't understand why people approach this with Ohms law.

It does make sense in context of amplifiers, but not in speakers that are built and completed.

 

[dlaloum]

In context of a loudspeaker, that makes no sense to me. You cannot change the impedance of a completed speaker, so no point in such conversion, not even when comparing to other speakers. I don't understand why people approach this with Ohms law.

It does make sense in context of amplifiers, but not in speakers that are built and completed.

When you are looking for "rules of thumb" to use when comparing one thing to another... most amps are rated at 8ohm.... so translating to an "8ohm standard" makes sense in a rough sort of attempt at comparing apples with apples...

 

[Jukka]

When you are looking for "rules of thumb" to use when comparing one thing to another... most amps are rated at 8ohm.... so translating to an "8ohm standard" makes sense in a rough sort of attempt at comparing apples with apples...

There is a problem, it would be the other way around. It would make more sense to convert amp power ratings to match a speaker impedance, because you cannot convert speaker impedance to anything that would represent the speaker in any (scientific) way. Impedance is a "constant" for a given speaker. The voltage sensitivity actually makes more sense in that way.

Amplifier power for different loads is not related to how loud the speaker gets for each Watt or Volt.

 

[dlaloum]

There is a problem, it would be the other way around. It would make more sense to convert amp power ratings to match a speaker impedance, because you cannot convert speaker impedance to anything that would represent the speaker in any (scientific) way. Impedance is a "constant" for a given speaker. The voltage sensitivity actually makes more sense in that way.

Amplifier power for different loads is not related to how loud the speaker gets for each Watt or Volt.

What "makes sense" is what is most functionally useful at that point in time for its purpose.

The 8ohm (now apparently moving to 4ohm) standard for both nominal speaker ratings and amp ratings, is ubiquitous - hence it is useful for very broad generalisations.

Like any generalisation, you can poke holes in it with the exceptions fairly easily, which in no way reduces its value as a "rule of thumb".

 

[Marin]

What "makes sense" is what is most functionally useful at that point in time for its purpose.

The 8ohm (now apparently moving to 4ohm) standard for both nominal speaker ratings and amp ratings, is ubiquitous - hence it is useful for very broad generalisations.

Like any generalisation, you can poke holes in it with the exceptions fairly easily, which in no way reduces its value as a "rule of thumb".

I'm not sure that going to 4 Ohms is a good idea. Our amplifiers get hot and if you look at most AVRs and other amplifiers you'll see a piece of sheet metal acting as a heat sink.
In the auto industry they've already switched to 2 Ohms... that's a recipe for a short circuit ...
Not to mention that most cheap 5.1 all-in-one home theaters have almost all 3 Ohms rated speaker's as standard.
Not every amplifier can convert 100Watts RMS 8 Ohm's load in 200watts if loud is half like 4 Ohm's in 200W RMS....