j/k sealed boxes are great! but...for the standard sealed box, with 2 12s what is the frequency range when fine tuning? any one willing to share there specefic setting? mostly trying to achieve a clean sound. anyone? thanx.

 

IMO, a subwoofer should generally be low-passed between 50-80 Hz. Especially for SQ purposes, a rear-mounted sub should be crossed over as low as possible since higher frequencies will be more likely to be "localizeable" to the rear of the car, bad for staging. I'd see how low your midbasses can cleanly play, and cross them and the sub over around that point.

If you're working with a more basic upgrade, keeping stock speakers, I'd start around 80 Hz. and try raising and lowering the crossover point. You should be able to find a setting somewhere around there that suits your taste and application, since that's what it really comes down to.

 

Well, the are numerous variables totake into account in order to answer the question. For instance, where is the enclosure mounted, where is it firing towards, what parameters did you build the box for, power to the subs, where are your mid bass drivers mounted etc etc etc.

For instance, in my GS400, I am running a three way array up front - 5 1/4 & tweeter in kick panel and 6 1/2 midbass driver in door(factory location). While the mid/tweet uses a Zapco 4.0 (4channel) for power (I went active,used the p9), the mid basses receive their power from another 4.0 running in 2 channel mode(lots more power to the midbass). My subs are powered by a Zapco9.0 (2000 watts total to the subs) MY system was set up for IASCA competitions - so the midbass run from 250 - 50 hz (24 db slope) and the subs are notched at 40 hz (24 db slope) I've got great detail and tremendous up front bass but it took several hours of tuning to get the slope and xover freq right. You'll have to find out for yourself