JL Audio f112 blown speaker?

I am also glad I don't hear this compression.

JL use a 3.5" voice coil it should not normally compress too much at high
levels.
However, it appears to be a long coil short gap design which explains the high
harmonic distortion (around 10% and sometimes above). The long coil short gap
would be typical of PA and rock concert woofer designs - some manufacturers
make similar drivers in two versions (one short coil with less SPL output but
better accuracy and one long coil for more SPL) perhaps JL113 may lose power
due to very high excursions (4" peak is an unbelievable excursion- WOW!)
as the coil moves well outside the linear magnetic range, which woudl explain
the compression and THD. There is no doubt it is an excellent sub - one of the
best out there.

I turned up the F113 to levels I would never play normally and watched this excursion. Maybe 1" of excursion outward was noticed. To push this any further is not normal. At least for music. Movies may be a different story and I have had it loud enough to make it feel like my couch was being lifted. With one of these in a room 18' wide 40' deep and 10' high I have been extremely impressed. Two of these in this room will just work that much easier and give more depth and extension. It's going to be fun.

JPL,

4" is peak to peak - so 2 inch in and 2 inch out. This is the absolute maximum - it would probably sound even more distorted than 10% THD at those type of excursions.

One would have to drive this F113 to insane levels before hearing any distortion. As an owner I can promise you this.
The testing that is being done on these subwoofers are not real world. They do show what happens on a graph which does not mean too much to me. I would much rather listen to the sub in my own listening room and try to calibrate and integrate with the mains and room. The JL Audio has great features for doing this. Do we even know what excursions were taking place when this distortion was taking place?

Do we even know what excursions were taking place when this distortion was taking place?

The HT Shack Subwoofer test graphs are colored with a variety of measurements at various SPL outputs, all at less than insane levels. Many of the curves show what could hardly be called insignificant amounts of distortion.

If you look at an equal loudness contor plot of our hearing sensitivity then you will observe that the sound of 10% distortion will be much louder to our ears than an orignal 20Hz tone => because of our lack of hearing sensitivity at 20 Hz you hear the distortion louder than you hear the music.

Refer to the bottom of the page (last two plots) to see what Seigfried Linkwitz has to say about distortion at low frequencies.

Linkwitz suggests that 1% THD is the kind of distortion you ideally need in a sub - if you want to hear what is on the recording.