View Full Version : Did I build a wrong sized box?

03-20-2008, 11:28 PM
Hey guys,

I'm curious as to whether or not my box is too big/too small.

When I turn it up i get a sort of popping at certain low notes, its not a blown sub pop, more like a tat-tat-tat really fast at a certain hertz. This usually happens at low hertz, and if I cover the vent or put a piece of wood in to change the tuning by narrowing the vent, it goes away.

I used the free box plans that says 2.1ft^3 @ 32hrz, but when I put it into the RE calc I get 2.6ft^3 @ 28hrz.

I have a SS RL-P 12" and I'm pretty sure that the box is just too big for my sub, but am not sure.

Any input?

03-20-2008, 11:36 PM
how many watts are u running on what sub? imo could be bottoming out..just my thoughts
.5 isnt that much is that with sub displacement the 2.6cu/ft

03-20-2008, 11:37 PM
It is bottoming out... you are running out of useable excursion on the subwoofer when playing low notes at loud volumes By making the vent smaller you are lowering the tuning frequency. The port resonance reduces the excursion of the sub near the tuning frequency. Below the tuning frequency the sub is prone to bottom out--running out of excursion. A box that is tuned too high can lead to this if the program material has frequencies below tuning. If there are air leaks or if the port is too large or placed too close to the rear of the woofer the mechanical power handling may also be reduced, leading to a greater chance of bottoming out. A box that is too big can also unload the subs when too much power is applied. However I doubt that 0.5 cf will make a big difference. You are probably just playing a note that is too low and feeding it too much power.

03-20-2008, 11:53 PM
Holy ****, thank you.. Thats exactly what that nasty noise I was hearing is..

So pretty much, notes are to low for the sub to play?.. ugh...

03-21-2008, 12:00 AM
You have a SSF on the amp? Turn it up some if you do.....

03-21-2008, 12:19 AM
The subsonic filter (or high pass filter) will filter out (attenuate) signals below a certain frequency, preventing overexcursion of the sub. Raising the high pass frequency can help alleviate this problem.

03-21-2008, 01:06 AM
I do have a subsonic knob.

I'll play with that on some notes that I get the excursion limit and see if it helps at all.

I'm giving it ~700 watts