Need Help From Speaker Cab Gurus

[INTP]

So if I go with 4" ports what would be the optimal length?

I used box size of 2.25 ft^3 and tuning frequency of 50Hz and WinISD calculated 2 ports, each 4" diameter, 9.06" long. The assumption is that 50Hz tuning from Eminence is appropriate. WinISD calculates f3 at 62.44 Hz with the CB15

 

[Downunderwonder]

The Eminence tunings are verified. Compare to winISD to see the range of error.

You can always put in a best "longest" estimate and trim to suit using ears or rice.

 

[basscooker]

Should also say, with respect to the thread title, I'm no guru, I just learn stuff a bit at a time from guru's. Sometimes enough to get good results, and sometimes even enough to be dangerous.

I can say this definitely applies to me as well.

 

[Thor]

The one thing that amazed me when I rebuilt a Ratshack cab (2x12) was how fiddling the port sizes and lengths really changed the freq response curve. As you can see, it's all about compromises.

 

[AstroSonic]

Little hard to follow, but it sounds like you are considering the CB158. For the relatively small box you have, the CA154 is the better choice of the two (CA154 vs CB158). The mid-upper bass peaking is 'manageable' (+2.3db@100 Hz and crossing +1 db at 76 & 150 Hz), contributing a 'fullness' to the bass, but still with decent note definition. Tune to 56 Hz: F3=57Hz.

Alternatives include the dayton PA380-8, JBL K/E140, and the Faital Pro 15PR400. All 3 of these can be tuned in the box to produce a near 'flat' response. Many more alternatives are available IF you are willing to use a 12 inch driver or even two 10's (and make an adapter plate). The 2-2.5 cf box volume is a sweet spot for 12's.

If you would describe the kind of tone you are after we can be more helpful.