Contour Enthusiasts Group Archives Forums Modifications Audio Using a car sub for HT

I bought a set of MB Quart DVC subs link to specs last year and I never used them so I sold one on ebay but the other has just been hanging around. I am thinking of using it for my HT but don't really know how much it would cost and if it would be worth it. It's DVC and I don't think(?) that most of the subwoofer amps would work with it? I don't really know. I guess if it's a lost cause I will sell this one too, just wondering what the gurus here think?

In the proper box, with everything set right.. i'm sure it'll work as a HT sub.

Sure, it'll work. Building the correct box is the key.

Would something like this be apropriate as an AMP or should I use a plate amp from a place like partsexpress? I am all ears

Use a plate amp, makes it extremely easy to build the box. Here's the one I built for my HT system.


I built it using an down firing 12" MTX sub and a 250w plate amp from parts express link It's been tested and will beat just about any sub on the market (killed the $500 Bose sub ) Just build the box to spec and you will be very happy.

I ran some simple calculations for you. That speaker would work well in a ported box tuned below 30 Hz. Typical box dimensions might be in the 1.85-2.30 CuFt range. Remember to allow additional volume for the volume occupied by the ports and the speaker. Fill the box 40-50% with fiberfill or similar material.

These are appoximate results from a simple 1st order model. Use available modeling software if you want more exact results. These designs should be safe but not optimized.

The port will control speaker excursion to below 29 Hz, so excessive cone movement should not be a problem unless you have a lot of signal below 25 Hz. A good subsonic filter should help if you have any concerns.

With most home sub amps you will probably have to wire the VC in series (4 + 4) = 8 ohms. Consider using one of the Parts Express 250 or 500 Watt plate sub amp that someone else mentioned.

MB Quart RWC304 Fs= 27 Hz Qts= 0.38 Vas= 2.47 CuFt SPL= 86 dB

1. 1.85 CuFt tuned to 29 Hz. Calculated -3dB @ 30 Hz (in a medium room) Use (2) 8.75" long 2" dia ports or (1) 10" long 3" dia port.

2. 2.10 CuFt tuned to 28.5 Hz. Calculated -3dB @ 28.5 Hz (in a medium room) Use (2) 7.82" long 2" dia ports or (1) 8.93" long 3" dia port.

3. 2.30 CuFt tuned to 27.5 Hz. Calculated -3dB @ 27.5 Hz (in a medium room) Use (2) 7.32" long 2" dia ports or (1) 8.32" long 3" dia port.

If you plot Box Volume on the X-axis with (-3 dB freq), (port freq) and (port length) on the Y-axis, you could interpolate port tunings and lengths for different box volumes between 1.85 and 2.30 CuFt.

Ported boxes smaller than 1.50 CuFt give up the deep bass you might want for a home theater. If you go much larger than 2.30 CuFt volume the speaker "Q" in the box drops below the optimal range (~0.55) in a ported box.

A sealed box for home theater would yield the following results.

4. 1.00 CuFt sealed box. -3 dB @ 50 Hz. (Qtc = 0.707)

You aren't going to get any low freq. gain in a large room that you might see in a car, so a sealed box isn't recommended for HT. Making the sealed box larger than 1.00 CuFt for this woofer will actually raise the -3dB freq.

Hope this helps...

I ran some simple caluclations to give an example of what you might want to try and what you might want to avoid. You would want to tune the box in the range of the two flattest curves (Red +1 db bump and Black (nominally flat) with a +0.1 dB hump)

You want to avoid tuning the box too high as shown by the green curve. This will result in a +3 dB hump in the bass curve centered around 45 Hz. You will get more bass, but the transient response will be degraded.



These are approximations of what you might get in a dead medium to large room. With an actual subwoofer you would have to include room effects.