Originally Posted by gtpsuper24
The only thing I don't get is the recurring claim that XBL2 is more efficient cause to me it seems like my Arx need much more power to get to a certain level compared to all my other speakers i've. Going from Axiom to Arx was a huge step in the opposite direction especially for output were the Axioms didn't need as much volume to get as loud as the Arx.
If I may, any woofer's F3 limit and related efficiency at that point are tied to the physics of the driver, the cabinet air volume, and the bass reflex tuning parameters. These parameters describe both the bass limit and loudness at that limit, and involve only those inherent physics and not the speaker brand, quality, or even moving coil technology, at least to any significant degree. When we analyze them we always find that the larger piston enjoys an advantage - it is simply the larger acoustic lever.
In other words, to make the 5.25" woofer go as low as the 6.5" woofer in similar volumes of cabinet air, we have to decrease the efficiency of the smaller driver. Of course, we can easily gain this difference back with any good amplifier with ample available power.
Another significant factor enters in, which is current flow through the voice coil. Assuming that typical modern amplifier, a true 8 ohm woofer develops on average half (-3dB) the sensitivity of that same voltage across half that load, that being the 4 ohm woofer. The lower impedance driver will naturally be louder, at the cost of that much loudness again at the amplifier's maximum output.
Since current rises exponentially as frequency drops, the speaker with the 8 ohm midwoofer - regardless of the impedance peaks in its bass reflex region or in its crossover or tweeter region impedance magnitudes - should be considered a true 8 ohm system. Furthermore, the mid/woofer's impedance sets the entire speaker's average efficiency - a designer typically tunes tweeter levels down to the mid/woofer's level and not the reverse. (When the A1b is noted for spectral cohesion and natural dimensionality, it's partly because the tweeter is matched to the midwoofer.)
In short, to make them comparable under test, an 8 ohm load requires a 2.83v signal for 1W, while a 4 ohm load requires a 2.0v signal for 1W.
Whether such a difference applies here is up to readers to research in order to develop their perspectives.