tomp wrote:
It is even crazier when you look at the linear volume displacement of the driver. Even though it was 30" in diameter it only had .15" xMax. That gives it a total displacement counting both directions of 198 cubic inches. It also required a box volume of 300 cubic feet. Compare to a modern driver like the Dayton Ultimax 15. It has a smaller diameter but the xMax is .75". That results in a displacement of 199 cubic inches and can work in a 3 cubic foot box. And it only costs $225.
Where's the catch? Hoffman's law strikes again.The EV had a sensitivity of 100 dB and the Dayton a sensitivity of 86 dB. That was very important in the days when 6 watts was a monster output from an amp. However, at 86 dB sensitivity, a 125 watt amp will still give you 107 dB. Considering that you can buy a 500 Watt class D plate amp with DSP built in for $300 that is a non issue today.
Tom,
I cannot speak of this speaker in particular but, all drivers of pre-solidstate era had small xmax and high sensitivity. That is due to the fact that power was limited with the tube electronics.
Remember the driver you measured for me, Altec 411? It has 7.5mm xmax, which means it cannot play any frequencies below 46Hz at 110dB (assuming power is unlimited). The legendary Altec 416 driver used in VOTTs, has the xmax of only 4mm and it cannot play any frequencies below 63Hz at 110Hz (3dB more for vented enclosures) . kick drums go up to 114dB, so these drivers do need a subwoofer to be effective. In effect, pre-SS era drivers will have limited dynamics and frequency response in the sub region with tube electronics.
After the advent of Solid State Electronics. power became abundant so the, xmax went up and sensitivity went down.