He talked a lot about high efficiency. I just don't understand all of the craze for high efficiency speakers as if we are still in the 50's with limited powered amps.
First and foremost, the input power must be able to be converted cleanly and without distortion. So it’s not about how much power an amplifier can deliver, but how much usable dynamic range results from that power. A loudspeaker system is only as good as its ability to convert the input electrical energy into linear sound pressure. An inefficient speaker consumes a large portion of the input power without converting it proportionally into acoustic energy, whereas a highly efficient system actually transforms a significantly larger portion of this power into clean, undistorted sound pressure.
To achieve this, the bass range requires a large diaphragm area, sufficient excursion capability resulting in a high displacement volume, and, above all, a driver that remains linear even at large excursions.
A loudspeaker with an average efficiency of 86 dB/W/m requires power levels for high volume ranges that can quickly reach several hundred watts up to about 1,000 watts, while a 96 dB/W/m system achieves the same sound pressure level with just a fraction of that power, typically in the range of around 100 watts. This difference is not merely a matter of efficiency but determines whether the system is still within its linear operating range or has already significantly exceeded it.
In the rarest of cases is a traditional hi-fi speaker even designed to convert such high power into undistorted sound pressure. A large portion of the input energy is converted not into sound but into heat, causing the voice coil to heat up significantly. This immediately alters the driver’s electrical and mechanical parameters, as inductance increases and thermal compression causes efficiency to drop further under load. This means nothing other than that you have to put in more and more power just to achieve even a minimal increase in volume, while distortion increases exponentially at the same time.
In practice, this means that an average hi-fi speaker with moderate efficiency and about one or two 8-inch woofers reaches its limits and distorts audibly precisely when it is supposed to deliver dynamics in the bass range.
The only way to get around this is to sacrifice efficiency in order to achieve deeper bass, and/or to use large bass drivers with a high displacement volume and linear drive.
It is still not possible to consider sound pressure, low-frequency response, cone area, and enclosure size separately, even though many would like to and others imagine it to be exactly that way in reality; but these are all merely parameters that can still only be adjusted within the physically defined limits.
Even if you use a very powerful and clean amplifier—such as a modern Hypex or Purifi module highly regarded by ASR, with several hundred watts of low-distortion output power—the actual limitation remains in the loudspeaker, because what matters is not what the amplifier can deliver, but what the loudspeaker can derive from it in terms of sound pressure in a linear and undistorted manner.
For a speaker with 86 dB/W/m, you must use 10 times more power than for a speaker with 96 dB/W/m. This quickly puts the difference between 100 and 1000 watts into perspective, especially when you factor in some headroom.
This is precisely where the real advantage of highly efficient systems with drivers operating linearly within their “natural” operating range lies, because, first, they consume less power and, second, they usually convert this power in a much less compressed and distortion-free manner.
So not only do they operate at lower power levels, but they also remain stable under load because they can actually convert the supplied energy into linear sound pressure. What matters, then, is not the absolute amplifier power, but how much dynamic range is generated from the power that the speaker can still handle in a controlled and low-distortion manner, because a loudspeaker is, by its very nature, a very poor power converter and, in principle, little more than a sound-emitting complex impedance for the amplifier; even the most efficient loudspeaker systems have efficiencies in the single-digit percentage range.
So, in my opinion, it is still advisable today to select speakers that offer good efficiency and use high-power, linear drivers capable of moving large volumes of air in a controlled and distortion-free manner.
