one noob question..

[ryan750]

i'm just wondering how sub manufacturers measures their speaker sensitivity, are there any standard on what frequency is to be used?

[Moondog55]

I would assume that makers use that part of the measured response that gives the highest SPL, so if a sub has a rising response from resonance to breakup of ( lets say ) 6dB then that is the SPL they will use.


It's a cheat but most manufacturers do it.

I'd like to see all drivers measured at a reasonable frequency for the intended purpose, I mean what good is a sub that has SPL of 96dB at 200hz when it is only going to be used below 80Hz where its output may only be 81dB.

It pays to look at the graphs if they happen to be available

[ryan750]

hi,

another question..

i'm comparing the jbl gto series sub specifically the gto 1004d and the gto 1204d

1004d
http://manuals.harman.com/JBL/CAR/Bo...0Enclosure.pdf


1204d
http://manuals.harman.com/JBL/CAR/Bo...0Enclosure.pdf


it's stated on the woofer technical data that the 1004d(10") have a sensitivity of (91db,2.83v) and the 1204d(12") have (93db, 2.83v), but observing the graphs, specifically the "vented frequency response @ 2.83v" which means a watt into an 8 ohm load, the jbl 1004d(10") yields a much higher dbspl on all the frequencies on the graph than the 12". how could that be??? it's kinda weird for me, it's like having a 10" sub would produce slightly better spl than a 12 incher

[djk]

In general, the box size for a driver is proportional to the square of the Qts times the Vas.

The Vas of the 12 is twice that of the 10, thus it needs twice the box size (actually about 2.4x more considering the Qts too).

The box is undesized for the 12, hence it must have less output.

If you were to put both drivers in optimum boxes, the 12 would have higher sensitivity. The 12 would also have more maximum output due to it being able to displace more air.