ELF (Check my work, please)

[fortyquid]

WinISD shows that the Peerless 831709 loaded in a sealed, 1cu.ft box will, if fed a 100W signal @ 20Hz, will play at 96Db. Implementing an active EQ I can apply graduated attenuation to the upper frequencies, thus producing a flat response to 20Hz @ 96db. Effectively, I have increased the bass extension of the system by one octave at the expense of 16db of efficiency.

Correct?

Thanks,
-fortyquid

 

[phase_accurate]

Effectively, I have increased the bass extension of the system by one octave at the expense of 16db of efficiency.

The expense should even be 12 dB "only" - if I didn't take a wrong assumption (because we are only extending by one octave we are still quite close to the original cutoff frequency).

Regards

Charles

 

[SY]

The exact amount of efficiency loss will depend on what the un-eq'd alignment looks like, but for an octave in a sealed box, 10-15 dB is a reasonable guess.

 

[Vikash]

Again, WinISD does not show you the excursion graph, and you need to correlate the response graph with it to gain something useful. The graph you're reading assumes that there is no limit on the driver's xmax.

Take a look at the attached graph which shows that in a 1cuft sealed box the driver has exceeded its linear excursion at ~77Hz with 100W input. It will further move non-linearly (maybe by 15%) before it is mechanically stopped by the surround/spider/former hitting the bottom plate.

Bottom line is that it won't play 96 db with 100W input unless the driver can suddenly near triple its mechanical excursion - something the laws of physics don't usually permit.

 

[catapult]

WinISD does not show you the excursion graph

The alpha of WinISD Pro does. It has all kinds of nifty graphs including Maximum SPL which is the lesser of the excursion-limited SPL or the thermal-limited SPL at each frequency.

It's not terribly stable on my computer but it seems okay if you only open one model (or maybe 2) at a time.