Efficient speakers v. less efficient speakers

If driven with the appropriate amplifier(s), meaning a higher powered amplifier for a less efficient speaker and a lower powered amplifier for a more efficent speaker, are there any difference?
The most obvious differences are technical and practical -- not theoretical.
In theory, all you need is twice the energy for every 3db difference. In practise however your 90db spl/1m/2,83V will need 1000W energy to reach 120db spl and will have disintegrated long before those watts reach them!
That's assuming you have 1000Watts available to you, of course.

So, higher sensitivity allows dynamic headroom with reasonable requirements -- say 50-100 watts amplification. Indeed, if you have REALLY sensitive speakers, you can get away with less than 50 watts energy -- much easier to find than 1000!
You cannot compare efficiency alone without considering speaker/cone size and overall design...it is always a compromise.

The question:
If driven with the appropriate amplifier(s), meaning a higher powered amplifier for a less efficient speaker and a lower powered amplifier for a more efficent speaker, are there any difference?

The speaker design is generally what makes the difference.

An inefficient bookshelf speaker with a big amplifier can be comparable to a full size efficient speaker with a small amplifier when played at acceptable sound levels for both the bookshelf speaker and small amp.

A bigger speaker can ultimately go louder with less distortion particularly when pared with a big amplifier.

On the other hand,

An efficient bookshelf speaker, is rarely comparable to a full size efficient speaker.(Bookshelf being roughly up to 6" woofers, and full size being 12" or larger woofers)

In very general terms:

1) big speakers can be efficient, and play loudest with lowest distortion
2) small speakers tend to be inefficient if they have low distortion.
3) efficient small speakers tend to have the highest distortion even if they can play quite loud with a modest amplifier.
Yes, a big difference. High efficiency means lots of detail and resolution. Just try hooking up a noisy amp to a 100dB sensitive speaker and see what I mean. Inefficient speakers lose lots of musical information in the process.
I agree with both the above posts. High efficiency speakers can sound more dynamic, colorful, and detailed. The result is better impact and realism.
Ditto..these are the differences I hear between my system using 50 wpc and a friends system that uses an amplifier that puts out 800 wpc. His speakers are very inefficient (83dB) with a wicked load. It sounds a little slow by comparison on the same recordings.
What i am trying to get at is:
will inefficent speakers paired with high powered amp. equal to an efficient speaker paired with a lower powered amp. if the ratio db/wpc are constant, in terms of dynaic, detail, etc...
I`m GLAD to hear that! I have Infinity SM-152`s and
2 pairs of SM-155`s. They`re rated at
sensitivity 102db at 1 watt.
My Pioneer Elite C-91 pre-amp volume, sits at
9 o`clock MOST of the time,
that`s about .7-.9 watts per channel.
They DO sound loud.
Sorry I wasn't as clear. I intended my comments to apply to your stated comparison of efficient speaker plus low powered amp versus inefficient speaker plus high powered amp. My experience is that the inefficient speaker plus the high power amp will sound somewhat compressed and lack air and detail. As your original question implies, there is more going on than simple matching of efficiency with power. So, my answer is yes, there is a difference.
Rlew - I intended my reply to be a direct answer to your question. There will be a difference and it is mostly due to the speaker designs being inherently different. The amplifier power level is largely irrelevant assuming you are comparing same sound pressure levels - something your question implies.

Isellstuff - The volume knob position has nothing to do with power output whatsoever. If you used a power meter to calibrate it, ok, but if not, you have no way of telling what the actual power output is in absolute terms. Arthur
Short answer: no. You cannot generalize that higher sensitivity speakers paired with a low powered amplifier is equivalent to a high powered amp and low sensitivity speakers at a given sound pressure level. It depends on the quality of the amps and speakers. If you take an X brand amplifier line of two different wpc ratings and match them with speakers with different sensitivities and listen at the same SPL, then you will be essentially hearing the differences of the speakers - assuming that the amplifiers of the same line are very similar sounding and everything else equal. And overall speaker performance goes beyond, and not solely dependent on, the sensitivity rating.

High sens speakers are not necessarily better - if they were, then everyone would own them. Everything in audio is a trade-off, and high sens speakers are no exception. They require, among other things, low mass drivers and high magnetic flux which introduce distortions that rigid high mass drivers in low sens speakers do not have. Also, by their very design, they may have to result to horn loading to reach down to the lower midrange to bass frequencies. So what is actually "louder" or more "dynamic" may be mostly the upper frequency range.

So, for a given cost, it's basically either louder with a relatively limited frequency response (especially in the low end) or softer with a wider frequency reponse.
I'd choose a speaker you think sounds good and stop looking at the specs. Unless you're using a small tube amp under 10 watts per channel it won't matter that much; and 90 efficiency is good enough even for those.

I agree with you fully. I think you described the differences much better than I tried to explain.

Your point about horn loading is a good one.

A tuned bass reflex port is commonly used to increase a speaker efficiency enormously by adding extra bass response. Unfortunately, most of what comes from a tuned reflex port is resonance and not primary source signal...so that although you get a loud bass response it usually sounds boomy, muddy and warmly resonant => lots of distortion
I agree with the posts pointing out that a high efficiency system usually has better dynamic contrast than a low efficiency system.

Let me try to explain why. It's a nasty little secret almost nobody talks about.

Theoretically, a loudspeaker's output will increase by 3 dB for a doubling of input power. In practice, this is ALMOST NEVER true. The reason is power compression (also often called thermal compression), and its primary cause is voice coil heating. As you increase the power going into a voice coil, it heats up. As it heats up, its resistance increases. As its resistance increases, more of the power going into it goes into overcoming that resistance (heating it up still more) and less goes into actually producing sound.

Let me give a few numbers as an example (drawing on measurements posted by Bill Roberts on Audio Asylum). At normal volume levels, the typical 86 dB efficient speaker may well only give you an average of 2.5 dB increase in loudness for a doubling of input power. So let's say you have an 86 dB efficient speaker playing at 80 dB average volume level, and along comes a +20 dB peak (quite common). This speaker will compress the peak and you'll only get about +17 dB. On the other hand, a high-efficiency system (say 96 dB efficient or higher) usually has negligible power compression at normal listening levels, and will more than likely give you the full +20 dB that the peak calls for.

Once again, this is a generalization - I'm sure there are exceptions, but unfortunately this is something nobody measures and includes in their specifications.

Differences in the power compression characteristics of the various drivers within a speaker often cause the tonal balance to change with volume level, with woofers typically suffering from more power compression than tweeters and therefor many multiway systems sound dull at low volume levels and bright at high volume levels as they've been optimized to sound right at medium to medium-high volume levels.

On another note, bass reflex loading only increases efficiency in the region of the port tuning. It does nothing for midband efficiency. The reason why bass reflex speakers are usually more efficient than sealed box speakers is that the driver parameters most suitable for reflex loading include a more powerful magnet system, which is what raises the midband efficiency.

Hope this helps some.


Very good points about thermal compression issues and how they affect dynamic range and tonal balance. I agree with you fully.

A highly efficient speaker should certainly be better in these regards when listened to at moderate to higher levels.

Do you have a view on how distortion tends to be affected as you increase or decrease efficiency?
thank you for the comments/feedbacks

I am only concerned that someone reading this thread will think that a high sensitivity speaker is necessarily better than a low sensitivity speaker.

Unlike the general rule about a bigger box having better bandwidth and therefore being a better speaker.....there is no simple rule of thumb for efficiency.

There are indeed advantages in high sensitiivity speakers, as myself and others have pointed out, such as a better dynamic range (less compression), however speaker design requires a balance of compromises and high sensitivity is not always better.

In very general terms, ultra-efficient speakers should be avoided just as ultra-inefficient speakers should be avoided. Both will have strengths but extremes are generally achieved with large compromises in other areas instead of an overall balance in performance.

Let me give a couple of examples of how a manufacturer can achieve high efficiency at the expense of distortion;

Long coil operating in short magnetic gap gives a low cost and highly efficient driver but it increases harmonic distortion as the voice coil operates outside the linear area of the short magnet gap. Also the heat dissapation is poor in these designs....so while they are highly sensitive they do not dissipate heat as well as a shorter coil in a longer magnet gap.

Very light rigid cone diaphragms made from hard/stiff materials (magnesium,ceramic,polymers). These efficient rigid low mass cones have low internal damping and tend to have high Q resonances. This efficient choice of cone leads to higher harmonic distortion than more critically damped designs.
Here are a couple of links that clearly explain some of the complexity and compromise involved in speaker design.


Hi Shadorne,

I don't know enough to discuss the relative distortion properties of low efficiency vs high efficiency designs, much less their perception (which is what really matters).

I would think that some of the techniques used to get high efficiency are conducive to low distortion (such as powerful, symmetrical magnetic fields), and some are not (such as very short-throw voice coils and diffraction horns).

Distortion perception is often a level-dependent phenomenon; that is, we often don't hear the distortion until the volume level is sufficiently high. Also, the ear's sensitivity to distortion does not correlate well at all with distortion measurements; the shape of the distortion envelope and type of distortion play a huge role, and simple percentage distortion figures aren't useful.

On final point not to be overlooked is that it's not nearly as simple as comparing efficiencies. Box size, bandwidth, and cost also factor in. If we keep box size the same, then as efficiency goes up the bass exension is reduced. If we maintain the same bass extension, then as efficiency goes up box size and cost both go up.