Sean, these are the EX3 drivers which are rated at 98db at 1w/1meter, and in a suitable enclosure, they gain about 2db, which puts them at about 100db/1w/1m. With 2 watts, they do about 103db and with 4 they do about 106db. At 8 watts they are hitting about as high as they will go before some noticeable compression, due to to 8" driver size. They are rated to take 100w, but it really just doesn't make any sense to give them more than about 6 or 8 watts max. These are peak figures for music applications. They are not average SPL figures, nor are these figures relevant at the listening position. The much more expensive EX4 driver is rated at 99.5db/1w/1m and should do a little better, but it will still enter compression around the same point, because it is still an 8" driver, and starts to lose the ability to move enough air at around the same point. These are not long-throw drivers.
Also, it should be noted that these speakers don't go below 40 Hz, so there is not as much air for them to move at the frequencies they produce.In addition, the typical rear-horn enclosure will augment the bass response to help the driver out, when the freq's get lower. And, it should be noted that if the cabinet is narrow, the baffle-step losses will cause a 5db shelving-down at the 375Hz point, or thereabouts, depending on the width of the cabinet. This is why I added the mod to my Voigt Pipes. Many designers will just put in an electronic baffle-step compensating network and cut 5db off everything above 375Hz, but I didn't have the power to lose that 5db of efficiency, so I acoustically reinforced the frequencies below 375Hz with a wider, swinging baffle to keep the 1/2-space radiation much further down into the bass. I was a little concerned about edge-diffraction problems, but with the swinging baffle-extensions angled slightly backward, it doesn't seem to be any problem at all. So, I managed to squeeze all the efficiency of the drivers out of them, all the way down to about 48Hz, where much of the sound is coming out of the port mouth at the bottom, and has floor reinforcement. Simple and quite effective.
When these speakers are loaded into a front horn, then they can produce higher SPL, if the horn is properly designed, and they also generally have multiple drivers in these applications, due to the unacceptable size of bass horn cabinets. The Oris Horns mentioned above are good ones which provide about 104.5db/1w/1m, if I remember correctly. They use a powered subwoofer to handle the freq's below 150Hz.
Lowther claims the most efficient drivers in the world, but I think that there are a few others that can match them, and Loth-X is supposed to have one that is more efficient.
