Quick ?

[wlmrs 10+ year member]

building a box to a set hz freq. is like a shot in the dark to me,It's my first box so i guess i'll go with 38hz unless somebody can tell me otherwise

 

[Moe Lester 10+ year member]

Hes probably referring to the great decrease in cone control under the tuning frequency. The lower under tuning you go, the easier it is for the sub to move and bottom out. Excursion is very low right at the tuning frequency.

 

[flakko 5,000+ posts]

building a box to a set hz freq. is like a shot in the dark to me,It's my first box so i guess i'll go with 38hz unless somebody can tell me otherwise

i would go with like 32-34. A mix of loudness and sounding good.

 

[PowerNaudio 10+ year member]

The lower under tuning you go, the easier it is for the sub to move and bottom out. Excursion is very low right at the tuning frequency.

that's true,

if you build the box taking into account the T/S parameters of the sub. then you would not put a sub that has a high Qts, and soft suspension, low EBP in a ported box, ones you get out of the "safe zone" of the tuning freq the sub might bottom out, so using a sub with low QTS, low Fs, high EBP would most likely not have the problem of bottoming out when playing out side the tuning freq of the sub.

EBP:

taking the driver free air resonance (Fs) and dividing it by the electrical Q (Qes). If the resulting number is around 50 or less, you are looking at a driver that is best suited to a sealed type box. If the EBP is between 50 and around 100 or more, the speaker will work best in a vented enclosure. Horn loaded designs will perform best with an EBP of 150 or even higher.

Sealed box (and sealed bandpass) woofers should have the following characteristics:

Qts => 0.40

Fs

Xmax => 4 mm

Vented or ported box (and ported bandpass) woofers should have the following characteristics:

Qts

Fs

Vas should be relatively low (less than 4 cubic feet unless enclosure size is not a factor).

pretty much enclosure design is critical not only to make the subwoofer sound good, but to keep other parameters like over excursion under control.