Two Infiniti Perfect 12 DVC --> Isobaric Box

[ProjectRob]

I have four Infiniti Perfect DVC 12" (dual 4 ohm) subs that I want to throw two of them in a box. I can't recall if the power ratings that Infiniti publishes are per voicecoil or not. The sub is rated at 400W RMS but I'm pretty sure that is per coil, so i could wire up each sub at 2 ohms and drive an amp to each subwoofer. I am positive that it is way overkill which is why two of them will be more than enough, but I enjoyed making some isobaric boxes back in the day and was interested in getting your thoughts for what to go with. To power them, I have two JLB GTO601.1s which are 580Wx1 at 2 ohms. Both of the subs have the LowQ insert in them and I can only find one of the MidQ inserts, so that's what I'm stuck with.

I used to work in a Circuit City Roadshop (sad that they are gone...) and designed custom boxes but I will admit that I am a little out of the loop. I listen to mostly pop music and I can't even recall what frequency to design it for. They'll be going in a large SUV and I figured that I would throw in two subs because I could though I do not want to go deaf. My days of SPL competitions are behind me!

I would love it if someone could give me some advice on which type of isobaric would yield a good overall box and help me calculate the volume of the chambers in the box and I'll run with it and make the box.

Sub Manual:
http://manuals.harman.com/INF/CAR/Ow...2012-2-02).pdf

Detailed Sub Specs:
http://www.infinitysystems.com/car/p...=US&Region=USA

Thanks in advance!

- Rob

[ProjectRob]

anyone?

[taloyd]

Rob,

Try downloading Unibox (UniBox - Unified Box Model for Loudspeaker Design) -

input all the speaker specs in the top left corner

Under Drive Unit Configuration, select 2 Drive units in series, compound (the compound = isobaric). The subs you have are dual 4 ohm, so if the two coils are in parallel then that's 2 ohms per sub, then the 2 subs in series with each other is back up to 4, which is what the amplifier will be happy with.

The bigger the box the tighter the bass, and the less power they'll require (a good thing).

The power rating, btw, is definitely for both coils together.

Play with Unibox, read some tutorials online as to the relationship between box size, sealed vs. ported, etc.

All isobaric gives you is a smaller box - nothing more. It's basically a trade off between the extra cost/hassle of using TWO speakers that can only achieve the same sound output as ONE - but the box is HALF the size of a box for ONE speaker (kinda because each speaker is doing half the work, gross oversimplification).

What I'd check out if you want super low distortion, but it'd be a box 4 times the size (ie: the normal size for two speakers) is a push-pull slot loaded... look up PPSL subwoofer, and you'll find some information about that. That's basically the best way to use two identical sub drivers.

cheers,
-Tal

[bjorno]

Originally Posted by ProjectRob

anyone?

Hi,

Infinity-Kappa-Perfect-12dVQ suggestions:
The closed box seems IMO to be best choice for your van unless you can house a T-TQWT.

b

[GM]

Looks like as little as 5 L net for sealed isobaric. Hitting it with 1.6 kW/driver of pink noise would probably make a great YouTube video.

GM

[ProjectRob]

Thanks for the feedback! Any idea how long of a line I would need to do a T-TQWT? How about the volume? I found a useful article on it that had some useful CAD drawings that I could replicate for my application in my car (Infiniti QX56). The room is there and I guess I could part with it.

T-line dual 8" subwoofer build! - Home Theater Forum and Systems - HomeTheaterShack.com

Otherwise, I can just throw them in sealed boxes that are 1.25' which isn't nearly enough work/fun.

[revboden]

Originally Posted by ProjectRob

T-line dual 8" subwoofer build! - Home Theater Forum and Systems - HomeTheaterShack.com

in the link above the guy just made a pretty picture without doing the math. danger danger, stay away from that design. you'd be better off just making a BR with a long low slot port.

[bjorno]

Originally Posted by ProjectRob

.. Any idea how long of a line I would need to do a T-TQWT? How about the volume?..

Here is a crude picture containing the answers and almost a step by step folding approach:

b

[ProjectRob]

Originally Posted by revboden

in the link above the guy just made a pretty picture without doing the math. danger danger, stay away from that design. you'd be better off just making a BR with a long low slot port.

Ha, when I first saw his first post, I was impressed with his CAD skills but was worried that more time went into the drawing than ensuring that the angles and dimensions were calculated correctly.

Thanks bjorno - I'm thinking that may be out of my comfort level! Eek. Appreciate your insight.