I spent all weekend building a box for the boot. I wanted it to look like MM's, with the sub mounted flush and with the height not exceeding the level of the bottom of the rear seat. And i did it with wood....not with glass.

Well, I am mostly done and I made the foolish mistake of cutting the 10" mounting hole BEFORE i calculated the box volume. OOOPS.
Now that it is done, i have a box with .4cuft of airspace and a 10" hole. The sub i made it for is an old Kicker Solobaric SC10. It has a hole in the bottom of the magnet that i have read creates a requirement for airspace beneath the magnet.

Anyway, to test this, i will need to rig up my amp in the garage from a battery and somehow provide the amp a proper signal source.

Does anyone with a lot of box experience know what the lack of volume, and lack of space between the bottom of the magnet and the box is going to do to the performance of the sub? Not to mention the integrity of the speaker and the amp?

Kicker 10" Solobaric SC10 8 ohm single voice coil (10 years + old)
Fosgate P450.4 4 channel amp that I will bridge one of the channels for the sub

Its either this or:
1. try to cut a ring that i can somehow attach to the 10" hole and create a new 8" hole for a JL 8" 4 ohm dual voice coil. (W3V2?)
2. start over and end up with a box that will be taller than i want.
3. start over and cut the 8" hole

 

I'd probably just go for an 8" sub, considering the space available and the age of your 10" sub.

Plus, an 8-ohm SVC sub isn't much good by itself, since it can only be configured as an 8-ohm load. This will cost you a lot of power. For example, if you bridge two channels of your P450.4, you would get 225 watts into a 4-ohm load. But if you use your 8-ohm sub, the amp will only produce half that much power (about 110W).

If you go with an 8" sub that can be configured as a 4-ohm load (either a single 4-ohm voice coil, two 8-ohm voice coils, or two 2-ohm voice coils), you'll be able to get the full 225W out of the bridged amplifier channels, plus the sub will be a better fit for the space you have.

As for the effects of an undersized box on performance, a speaker in an undersized sealed enclosure won't play as loud (volume) or as low (frequency) as the same speaker in a properly-sized enclosure. The power handling ability will increase slightly in an undersized box, but that's offset by the loss of volume from the box being undersized.

If there's not enough space behind the magnet, you might overheat the voice coil. That's what the hole in the back of the magnet is for - it's a vent to cool the pole piece in the speaker (the part that the voice coil rides up and down on).

 

Alta/I have a box coming out with .7 cubic feet thats more than enough and snaps into the boot, instead of having no airspace and crappy sound. I have a decent sized 10 in there and it sounds great, tunes low. Keep you eye out, pics were posted in interior/exterior, they'll get here soon.

have fun,
Josh

 

thanks all.
Scott...
What happens when a driver overheats? likely it will result in its death.
i am trying to set up the amp and a battery and a denon home theater receiver with pre-amp outs on my workbench so that i can test the sound reproduction. what i cant test is the overheating factor.
It appears that you looked up the specs on my amp. Thanks! I thought that when you bridge an 8 ohm load to an amp, that the amp sees 4 ohms. therefore pushing 225watts to the sub. if i am only going to get 110 or so, it will not work out.

 

What you're probably thinking of is the fact that a single four-ohm load on a bridged amplifier channel causes the amp to produce the same total power as if you had a 2-ohm load on each channel in non-bridged mode. It's technically not correct to say that each channel only "sees" 2 ohms, but if it helps you visualize, it's okay.

This means that bridging two of your amplifier channels together and using the bridged channel to drive a single 8-ohm load will get as much total power from the amp as if you left the two channels unbridged and gave them each a 4-ohm load. If you look at the specs for the P450.4, you'll see that the power produced by a single channel with a 4-ohm load is 60W.

The total power from two channels, each driving 4 ohms, is 120W. So, bridging two of the channels together into an 8-ohm load produces the same total power as two non-bridged channels each driving a 4-ohm load, or 120W total.

To get the advertised 225W from two channels bridged together, you need to provide the bridged channel with a 4-ohm load.

As for the overheating, it's not likely that you would actually burn up the voice coil, but the efficiency of the speaker will drop off as the voice coil heats up. I don't know if Kicker has a minimum recommended clearance between the magnet vent and enclosure, but I'd think as long as you have 1/2" or so, you'd be fine - just don't block the vent entirely.

 

Awesome. thanks.
I got the test set up finally and spent the last 30mins listening to the sub with my old amp. The amp is a carver kmos2200. the specs say: mono mode, 8 ohms 200 watts, 4 ohms 340 watts. So i am pushing the sub with 200 watts. I have always been happy with this sub in a pre-built enclosure but i have never listened to it as i did today. It was very noisy...make all sorts of vibrating and rattling noises that seemed to be coming from the speaker itself. I installed it back into the proper enclosure and while it got a little better, there was still quite a bit of unpleasant rattling. (like the rattle i have in my mini that is driving me nuts!)
Perhaps the age of the speaker is showing.

I think that i am going to try to instal the JL W3V2 D4 that i have. I plan to wire it in series and create an 8 ohm load as the driver is rated for 125W RMS at optimum levels...perfect for the bridged channel of the P450.4 if i understand properly.
thanks again for your help.

This is going to require some creative woodwork.