Cheap way to have a subwoofer?

[technominds]

OK, so if you want a nice sounding sub... you generally have to spend hundreds on doing so... but here's whats wierd... I have a subwoofer in my car that sounds incredible inside and outside my car.... my question...

Why cant I buy a car subwoofer (can get them for like £50 with 15" drivers) and connect it to a decent amp... then I can set up an output in sonar so that it always runs through a single channel on my desk, then permanently have LPF on it?

Surely this would save me hundreds on buying a 'studio' subwoofer?

Let me know where im going wrong.... if indeed I am...

Peace!

EDIT: I seem to be coming up with so many cheap ways to do things... I might start my own 'Build a decent cheap studio thread'...

[frederic]

I tried that, and at least the MTX sub that's in my Lincoln, sounded way to thumpy in the studio.

Remember that the car interior (or truck interior) is very small and car subwoofers are generally tuned for a very tight frequency range, to add thump to the kick, bass, and so forth.

For a studio, you want a smooth response to the frequency spectrum that you want it to provide.

You'd be much better off with a quality home theater subwoofer, assuming it's of decent size. I have an old $99 realistic (radio shack) 12" down firing subwoofer, which I found the best placement is on it's side, under my console table, firing at the back wall, about 6" from that back wall. This was determined through trial and error, and I put together a switch and a bunch of relays so I can bypass it at will, as well as feed it off it's own channel/amp rather than the "factory" pass through crossover that it is.

So I can listen to it in series with my monitors, and I can bypass it completely.
I can switch it to it's own amp for 5.1 or 7.1 surround mixing, and bypass it completely.

[technominds]

Thats quite cool... but maybe your MTX had a build in crossover? My car sub doesnt... it uses the amp as its crossover.. so I can even use it as a muffled loudspeaker (not that I ever would) Im wondering if its the crossover that gives it that thumpyness because mine seemed quite smooth.... il pull it out my car and try again.. or maybe use my old dual 12" to test out with!

Il keep you guys posted..

[frederic]

Originally Posted by technominds

Thats quite cool... but maybe your MTX had a build in crossover? My car sub doesnt... it uses the amp as its crossover.. so I can even use it as a muffled loudspeaker (not that I ever would) Im wondering if its the crossover that gives it that thumpyness because mine seemed quite smooth.... il pull it out my car and try again.. or maybe use my old dual 12" to test out with!

Il keep you guys posted..

The realistic home theater sub in my studio has a stereo, pass through crossover.

The sub in my Lincoln doesn't, however the amp that drives it does, and I used the amp in the studio (on a 13V, 30A power supply) as an experiment. So it was wired with an adjustable crossover, and I tried several different settings.

The design of the sub cabinets are totally different. THe realistic unit is really just a box, with a subwoofer and a port, facing the floor, with 1" legs (or so). The sub in my Lincoln has more airspace (larger enclosure), and has no ports whatsoever. Instead, it has a passive radiator inside, seperating the two halves from each other. It's really a bizarre design, but it sounds excellent in the trunk. Picture two, unequal sized chambers, with a passive radiator between, with a subwoofer in the larger chamber.

[technominds]

No ports on a sub? Thats quite unusual... where does the airflow go?

Looking at some designs of studio subs and designs of some subs ive seen for sae, ive found some that air almost identical... so surely running through the same amp they should have a fairly equal sound...

This idea was a cheap idea of course, to get some form of bass to a studio that has none (which i seriously recommend because hardly anyone realise how much crap they cant hear without listening through a sub). But i think it could work well... im going to tweak some parts and let you know if I get a decent sound!

[mshilarious]

Originally Posted by technominds

No ports on a sub? Thats quite unusual... where does the airflow go?

Well if there is a passive radiator, then the change in air pressure moves the passive radiator's cone.

If the sub is not ported, then the pressure inside the cabinet varies more than it would otherwise. The air doesn't have to "go" anywhere, it can simply be compressed and decompressed. That will resist the movement of the speaker's cone, which gives you a higher cutoff frequency than a ported system. If the sealed box is too small, you lose lots of bass response.

With a ported system, you can tune the port to extend the sub's low bass response.

Cool site with calculators:

http://www.mhsoft.nl/spk_calc.asp#ported

[frederic]

Yep, the car sub has no port. It's a two chamber box, with a passive radiator in between the two chambers, and the sub is in the larger chamber.

I bought it because it doesn't "thump", but instead provide loud, smooth bass which is what I wanted actually.

I didn't need to rattle the truck lid (though I can if I cranked it), but rather just fill in the bottom end a bit considering the four 6x9's are just that - small.