A Second DX12?

[puckster]

Hello,

I am currently happily running the following system in my 97 Integra. Polk MM465 in the front 602A's as rear fill and one DX12 in a sealed enclosure. The Momo fronts are powered by a JBL BP180.2 Amp and the reasr fills HU power. The sub is powered by a JBL BP600.1. My question is what effect would it have to add a second DX12 in a sealed box to the system?. I would still power both subs from the same amp.

[Kim]

By adding a second woofer you will increase the overall gain and impact of the bass. More bass... less volume.... It almost sounds like a beer commercial!!! Just make sure that the amp is capable of driving a 2 Ohm mono load if the woofers are 4 Ohms. Do you plan on installing the subs into two separate .88 cubic feet sealed enclosures or are you going to build a common chamber sealed enclosure for them? If you use a common chambered enclosure make sure that the internal volume is 1.5 to 1.75 cubic feet and install 1 pound of poly fill. Set the crossover frequency to 80 Hertz.

Thanks,
Kim

[puckster02]

Thanks for the advice Kim,

Is there a benefit soundwise to installing the second sub in a separate box as opposed to a single chamber one? When constructing the dual sub/single chamber box, is there any rules as to how far each sub must be apart from each other? And the last question, I'll be wiring them up to run on a 2 ohm load. Will my JBL 600.1 (which runs at 600Watts RMS at 2 Ohms) be enough to drive these two subs comfortably?

Thanks again,

Ken

[puckster02]

And Kim, One further question. When wiring up these subs in parallel in the single chambered box, can I wire each sub (positives, negatives) internally in the box and then run a single pair of speaker wire to my amp (externally from my speaker cup? Or do I have to run two separate pairs of wires directly to the amp? If it helps, the amp to speaker run is less than 3-1/2' long.

[Kim]

Ken,
The big adavntage of using separate chambers is that this will minumize cabinet resonances and make the enclosure more rigid.
If the panels are too large on a common chamber enclosure, there is a greater chance of the panels flexing and resonating at higher volume levels. Use 3/4 inch MDF for the box building material. This is a very dense material.
The JBL amp should drive these subs just fine. Set the low pass crossover to 80 Hertz. You can parallel both positive and negative leads together to obtain a 2 Ohm load and connect them to the positive and negative terminals on the terminal cup. This makes "removing and reinstalling" much easier if you need to put something large in the trunk.

Happy Cutting!!
Kim

[puckster02]

I will be using 3/4" MDF for the box. I'm going to cinstruct the box to be of the 1.5 Cu Ft Size so I'm hoping that I do not experiance the "resonance" problems you describe above. Once again, is there any rule for how far apart the subs should be mounted?

Thanks again,

Ken

[Kim]

Ken,
You can install some 2 inch wide braces along the interior of the longer panels in the enclosure. This will help to minimize the chance of encountering panel resonances.
For the location of the woofers on the front panel, I would suggest maintaining a distance of 3 to 4 inches from each driver and install a brace directly behind the middle of the front baffle.

Good Luck!!
Kim

[puckster02]

Ok Kim,

Thanks for all the advice. Because of space limitations, I have decided to construct a single sub box with dual sealed chambers. Two subs with a 3/4"MDF wall between them. I'll make the box out of 3/4" MDF and the inside dimensions will give me .918 cubic ft per sub. This wil also allow me to have the subs sitting side by side, roughly 2 or 3 inches apart. Do you see any problems with this idea? And I assume from your past advice that I should add approximately 1/2lb of Polyfill per sub? The outside top dimension of the sub box will be 27.5" x 18.25" if this helps. The box will be 9" tall (OD).

Thanks again,

Ken

[puckster02]

Bump

[PoweredByDodge]

argh...

i've got 4 dx 12's in my pickup.... and i did "one big box" ... two chambers, 2 subs per chamber, and i tell u i wish i had done separate chambers. I don't like how the subs fight for air space or how i get this little "flex" crap when the volume is all the way up. However, if u brace it like kim says, u prolly wont encounter that problem.

i keep tellin myself i'm gonna build another box when i get "un-lazy"... but the realiaty is that by teh time i do build another box, i'll be doing my "crack head" system which would be momo coomponents up front / dx 8 inch subwoofers for "mid sub bass" up front in custom fabbed sealed kick panels (with a lot of dampening to keep them from rattling along the walls) / 4 momo 10's bandpassed at 110 hertz low pass / 60 hertz high pass (yes i can build a filter that will do that) / and two IDMax 12's running 60 hertz to subsonic levels ... it might work... maybe.. :) lol.