It's not like that really, that's more like a side effect. More BL leads to higher efficiency (and lower Qes). Lower moving mass also, though trying to damp a cone for better upper frequency rolloff tends to become heavier. Efficiency IIRC is proportional to the square of the cone area, so tiny drivers cannot be very efficient (also because you can't physically shove much BL through their smaller coils and magnets). All this refers to midrange efficiency. At the lowest frequencies...hard to explain what I think. In a small box you need a heavy cone to keep the resonance low, then a lot of BL so the Q is not boomy.*
Really in the end you need to fix on your box size, sealed or ported and if ported how low, and then use a good modeling program to see what happens. Ideally you would have a program like LEAP that could input actual impedance magnitude and phase and model really closely. LEAP is defunct and I'm not sure what other candidates are as worthy these days. I want to find something like that, which will kick out absolute SPL including multiple drivers loading each other.
*yes you could EQ and DSP and all manner of other things like servo control (is Velodyne still doing that? Someone else is but I can't recall who).
For efficiency most important is having big drivers and enough of them. Qts and Qes is less important (with dsp) :
https://www.diyaudio.com/community/...how-off-my-new-18in-build.365764/post-6711139
https://www.diyaudio.com/community/...how-off-my-new-18in-build.365764/post-6765958
High Qts can give you more efficiency
https://www.diyaudio.com/community/...how-off-my-new-18in-build.365764/post-6767025
https://www.diyaudio.com/community/...how-off-my-new-18in-build.365764/post-6711139
https://www.diyaudio.com/community/...how-off-my-new-18in-build.365764/post-6765958
High Qts can give you more efficiency
https://www.diyaudio.com/community/...how-off-my-new-18in-build.365764/post-6767025
Hmmm...so now we have votes for both high Qts and low Qts leading to efficiency.
I will use an analogy to lighting to try to clarify.
Lighting efficiency increases as we go from incandescent to fluorescent to LED. In other words, if we feed 40w to each of these, in general the incandescent will produce the least amount of light, the LED will produce the most and fluorescent somewhere in between. Yes, we can use larger bulbs, higher power bulbs or more bulbs to produce more light. However, using a greater number of higher-power and larger incandescent bulbs does not increase their inherent efficiency (or may have only a marginal effect). The fact remains that LED is just the most efficient of this bunch in converting the electrical energy into light energy.
Indeed, just as in lighting, we can use larger subwoofers, higher power subwoofers or more subwoofers to increase output. It's pretty evident that a single 4" driver will simply never match the output of even the worst 18" driver. Likewise, we can take a dozen pretty crappy 12" drivers and get far more overall output than the very best single 18" driver.
The question again becomes...what parameters or materials etc produce the most efficient translation of electrical energy into cone motion and thus sound energy? Since subwoofers all follow the same basic design with voicecoil in a magnetic field, I'm wondering if there really is much difference? I suppose maybe the materials used for the magnet and the VC and maybe some design elements (air gap, shorting rings?) would have an impact along with cone material and weight, and we need to assume the basket will also not flex and lose energy. I suppose it is more like comparing efficiency amongst LEDs as opposed to LED vs incandescent.
As I look back at posts #16-20 in this thread, that seems to align with what I am getting at. I am coming to a conclusion here. If we have two subwoofers each of equal diameter in boxes of equal size being fed an equal amount of power, then in general the subwoofer with higher Bl and lower Qes will tend to be more "efficient" at converting electricity to cone movement. I understand we never go about designing a loudspeaker this way without taking into consideration size of room or car, power and space available, goals for the system etc. etc. I was really just more interested in trying to narrow down some quick ways of being able to look at specs and determine which ones might possibly lead to the most efficient use of available wattage.
Everything right.
I only wanted to remember that especially having high efficiency reproducing long (bass) waves needs cone surface or horns giving acoustical resistance/ impedance matching to the air.
Prominent example are big horns.
Instead you can stack (big) drivers.
So Qes is nice, but not maybe the most important parameter.
Usually you can beat expensive high power long throw drivers by choosing more cone surface with less sophisticated drivers.
I only wanted to remember that especially having high efficiency reproducing long (bass) waves needs cone surface or horns giving acoustical resistance/ impedance matching to the air.
Prominent example are big horns.
Instead you can stack (big) drivers.
So Qes is nice, but not maybe the most important parameter.
Usually you can beat expensive high power long throw drivers by choosing more cone surface with less sophisticated drivers.
