To get “more!” out of a ‘speaker’, we have two choices:
- more electrical power to the speaker
- a speaker which makes more sound from electrical power
HAs call the speaker a receiver, and it is a very specialized thing, but does not break any laws of physics.
And there are dozens of receiver models to cover a wide range of needs. High power, extended bandwidth, ultra-tiny, even crude+cheap.
It does seem that “high power” receivers often go for lower impedance to suck more from a fixed battery voltage. But that hurts battery life. In general low impedance raises amplifier THD, but with B or D amplifiers the amp THD should be insignificant.
Speakers all have THD distortion, rising with level. The balanced armature receiver has some extra sources of distortion but the designer can work with proportions, size, and specs to deliver astonishing high clean levels to an ear.
Speaker/receiver acoustic output per electrical Watt, efficiency, can be good at low frequencies but always falls-off at high frequencies. Take receiver 17A003 as typical. If the iron in the armature is increased (red), the added iron in the varying magnetic field will produce more Force and higher output. However the higher Mass shifts the resonance(s) down and there is -less- output at higher frequencies. A lesser mass of iron (green) gives less output at low freq but vibrates better at high freq.
(In real receiver line-ups it is unlikely to find this simple relationship because other parameters may be tweaked.)
So it really matters “why?” we want “high power”. If it just has to sound louder, clarity not critical, the red curve makes the most of the power. This is also good for severe loss 100-1000Hz and “no hearing” (don’t even try) above 2kHz (many “power” users may be in this situation). For my ski-slope, I don’t want <1kHz and actually the stock '003 does best where I need it. For a musician with OK hearing to 4kHz but needing fine discrimination of 5k-10kHz cymbal and string-zing balance, the “green '003” light armature covers that area best.