sub and enclosure question

[kenhoeve]

I have a sub enclosure that I'm a little confused about. The sub is mounted on the exterior of the enclosure such that the sub faces into the enclosure. The enclosure is sealed. Pardon my ignorance, but does this mean the sub is reverse firing? Basically I'm trying to figure out what kind of sub I can put in it's place.

 

[GlocksRock]

no it doesn't mean the sub is reverse firing, it's just mounted different. For instance, if you had a box for 2 subs, and one sub was in the box, and the other was mounted the way you describe, you would have to wire one of the subs out of phase so that the bass waves don't cancel each other out, but you can still do it like that. It's done fairly often in car audio applications.

 

[annunaki]

This is usually done for car applications, more for looks than function. For function, the woofer can cool better being in the ambient air. It also frees up a very small amount of space in the enclosure. When done with two woofers one in and one out, they will technically cancel any small non-linearities in output. Again, this will be in all likelyhood inaudible.

Disadvantages: Mechanical noise possibilities, takes up more space, less surface area to generate output (not audible in nearly all cases).

 

[kenhoeve]

Another question. Say this enclosure is very small. Maybe 0.33 to 0.4 cuft. If one can only find subs for a 0.5 cuft enclosure, but do not expect to run the sub anymore than the 50% range, does the volume discrepancy matter much?

 

[annunaki]

If the sub will be for car audio use, it should be fine in that small of an enclosure, though it may be a bit boomy and lacking in the low end.

What size is the driver? What driver is it?

 

[kenhoeve]

It's a factory sub and enclosure for the Volvo V70. It sits entirely hidden beneath the rear deck and is shaped such that it fits above the spare tire with the sub centered into the spare tire well. I really like that it is hidden, I just don't care for it's sloppiness.

 

[GlocksRock]

Add some polyfill stuffing to the inside of the box, add about 1/2 lb. That will make the sub seem like it's in a larger enclosure than it really is.

 

[annunaki]

The woofer is probably in too small of an enclosure. Stuffing will help, but very slightly. I am sure there are a myriad of other issues with it being a factory woofer. Enclosure resonance being first and foremost.

Try wrapping the enclosure in dynamat inside and out. You then may want to try putting a few layers of fiberglass over the top (of the dynamat on the exterior) to strengthen it up if that does not help. Make sure there are bends in it or it is curved. Fiberglass is not real strong on a broad flat surface. You will want the 'glass to be about 1/4" thick.

You may want to look at replacing the woofer and amplifier. Use an Image Dynamics IDQ10 or IDQ8 for that small of an enclosure (after you modify it of course) they work pretty well in small enclosures. 250-500 watts rms work well with those subs.

 

[GlocksRock]

Check this sub out, it will work well in that size of an enclosure.

http://www.edesignaudio.com/product_info.php?cPath=1_21&products_id=29

 

[kenhoeve]

Yes, I fully plan on replacing the amp at the same time. My conundrum now is that the original sub is 12"!!! No wonder I always think it sounds so damn boomy. I'll have to retro the cutout to fit an 8'' sub. Careful measurement has shown about 0.33 cuft, which is just right for many of the 8" subs. Also, the 8" subs fit my depth requirement of <5". Although I could shim the enclosure cap and get it to 0.5cuft, and go to a 10" sub. I am doing some dynamatting of the door panels, I'll use some back there too, thanks.

 

[annunaki]

Yes, I fully plan on replacing the amp at the same time. My conundrum now is that the original sub is 12"!!! No wonder I always think it sounds so damn boomy. I'll have to retro the cutout to fit an 8'' sub. Careful measurement has shown about 0.33 cuft, which is just right for many of the 8" subs. Also, the 8" subs fit my depth requirement of <5". Although I could shim the enclosure cap and get it to 0.5cuft, and go to a 10" sub. I am doing some dynamatting of the door panels, I'll use some back there too, thanks.

I meant wrap the enclosure in dynamat to help alleviate resonances. Shrinking the baffle size to accomodate a smaller sub would be a good solution. A better solution would be to mold a new enclosure .