improperly tuned box

Ok, I am going to try and enlighten you here a little, since it seems as though you were not happy with anyone else's responses...

As you probably know from past correspondance, I have a set of the same subs you have (Earthquake DBX12, single 4 ohm coils). These subs are infact better suited to a vented enclosure than a sealed; HOWEVER - the bandpass box you keep touting is not a vented enclosure per se, and as I am guessing it is a pre-fab bandpass box, it is all the more useless. I can tell you with 99.9% certaintly that there is not a prefab bandpass box made that will sound acceptable, let alone good, with ANY speaker installed. There are just way too many design parameters that must be taken into account when building a bandpass box, and they will be speaker/listener dependant - a prefab, one size fits all design is not going to cut it here...

Now, if you'll refer to my origional thread regarding the box I built for my DBX's, it will tell you basically everything you need to know to build a PROPERLY designed vented enclosure for these subs; tuned to ~30hz (not 35hz as I origionaly posted). This is a nice, low tuning frequency that will dig deep and sound good playing all types of music - not just a one not wonder type of box. If you choose to keep your bandpass box, that's fine - people like what they like; just know that is is not the most efficient, or best sounding enclosure you can get for these subs, and you are truly missing out.

Now to answer your last questions; the subsonic filter is used anytime you want to cut the lowest frequencies from going to your subs - a sub being used in a vented enclosure would be a good time to use this type of filter; as you would set it slightly lower than the tuning frequency of the box to protect your sub from unloading itself below tuning. A bandpass box shouldn't need this type of filter, because by it's very design nature, it is already cutting out frequencies below and above a certin range (hence the term "bandpass"...). BUT, this is where your prefab box will let you down - you have no idea what the passbands even are for this box, since it was not designed to work with your application. It could be cutting out everything below 20hz, or everything below 50hz(more likely), and it could be rolling off everything above 80hz, or everything above 150hz - the point is you jsut have no idea, and it is more than likely NOT the exact passband you will want to work with.

Adjusting the amp: yes, you will have to adjust the amp any time you move it from a different type of enclosure; a vented box is loads more efficient than a sealed one, but you will also probably want to setup the subsonic filter in the vented box (again, probably a little lower than the tuning frequency of the box). You will also probably need less gain on the sub in the vented box than if it were in a sealed box.

-Matt

You can get those subs still; I have mine in the fFor Sale section right now (shameless plug...).

You should be safe using either amp on either setup - just watch and listen to make sure the low tones aren't going too low and unloading the sub in the vented box - you'll be able to hear it if it does.

Anyway, I can understand your concern - but there's a reason you like the way her sigle 10" sounds - it's in a vented box and not a bandpass. But if you are seriously in love with your bandpass, so be it...

-Matt