4" Subwoofer?

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4" Subwoofer?

Hi,

I have a couple 2.5W computer speakers and I thought it would be fun to try and build a miniature subwoofer for them. I have a 4" driver I'd like to use. Any ideas for the enclosure? I'd like it to be small and/or easy to construct.

I have a 7W amp chip that I'll combine with a filter and power supply to make the electronics, this I need to fit in the box too.

Thanks!
Akshay
 
I agree that the bandpass enclosure would allow the 4"er to put out low bass. You may need some power to get it loud.

An offbeat idea that may work for close quarters listening would be to use the 4" up to the baffle step frequency of the satellites. This may give a good bass tone to a set of computer speakers that happen to need it.
 
How about horn loading it?
If you go for a cutoff of around 100Hz, it needn't be that big, especially if operating into 1/4 space or better.

The efficiency of this approach would also help overcome the power handling limitations of such a driver.

As you state this project is for fun, you needn't pay too much attention to correct horn flares, either. One of the good things about a horn is that even a really badly designed one will usually work to some degree!

Have fun!
 
Quite a stretch to get decent performance out of a 4" driver for bass. I'd consider a 5" midbass driver to be the minimum, and a 6.5" to be a good compromise of size and performance. Something like Vifa P17 in a vented box tuned from ~ 40 - 50 Hz. The 4" driver will have a lot of distortion, low output, and not much bass. If you do want to go ahead with it, you need some parameters to simulate its performance. Put it in a sealed box and you get no bass. Bandpass is tricky.
 
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