View Full Version : SQ box questions?

04-14-2003, 12:21 PM
I am building a box for a CDT MS-80 8" sub. Due to tight space limitations it is being made of half inch MDF. Internal dimensions will be 13.5" wide X 8" high X 6" deep giving me 0.375 cu/ft internal volume.

The sub specs call for a box between 0.25 cu/ft and 0.45 cu/ft with no mention of whether that is raw dimensions of dimensions with sub installed.

I do not know exactly how to determine sub dispalcement volume but I guessing about 0.33 cu ft? If someone has a more exact measurement please let me know.

The box is being made fit in the passenger side footwell of a 99 Mazda Miata. It will be carpeted on the outside to match the car.

My questions are:

1-How much acoustic filling should I use for this application either by weight or by volume?

2-For maximum SQ would I be better off facing it forward towards the passenger seat or rearward towards the firewall (there is a couple inches of oddly spaced clearance back there.

3-Is there any benefit to using a hard coat of varnish inside the box or outside. I am sure this would help in sealing the box but am unsure of the effect on SQ.

4-Getting any larger size for the box is nearly impossible and still have the passenger seat usable. Shallower depth is possible. if I drop the depth to 5" internally this would leave a volume pf 0.3125 cu/ft without the sub. Are there any benefits SQ wise to this? Would SQ suffer? Would SPL be more or less?

Thanks in advance for all responses and opinions.


04-14-2003, 01:35 PM
Displacement - I would guess around .03 cu ft. My 15" is .085cu ft.

1 - That's just a trial and error thing. Try a little and see how it effects the sound.

2 - In most cars I have heard the subs sounded better facing backwards.

3 - Never tried that. But it couldn't hurt. Especially if it helps with sealing.

4 - I would think any differences caused by a slightly smaller box would be very little.
SPL might be slightly more, SQ would probably be about the same.

Randy Savage
04-14-2003, 01:44 PM
Yes, displacement of the sub should be somewhere around .03 ft^3.

The sub probably won't sound much different if you face it either way. Sound waves travel in 180 degree waves, so they will still be going in the same direction, it just comes down to which direction will induce more rattling, so try it both ways and see how it sounds.

Maybe just use the varnish on the corners, round them off inside, that should help a little.

A smaller box will just yield less of a low end.

04-14-2003, 02:30 PM
What about spraying a sound deadener of some type inside. Someone said that would help?

Thanks. More comments appreciated.


04-15-2003, 07:45 AM
the smaller the box, the more power you will need to drive them...betcha the box will sound tght as hell...

there are many SQ participants here who put sound deadners int eh box, and put vibration dampers outside the box. How does this help? I have no idea. I remember MTX having this awesome sealed box called "black gold". This was an incredible performer, according to CA&E. It had this THICK sound damper thing insdie, and the box was very, very small. It was able to go down to about 22Hz without a single complaint. They say it's all SQ friendly..didn't get louder than the cheapest alternative...