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Old 13th July 2006, 07:32 PM   #1
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Lightbulb 4" Subwoofer?


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.

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Old 13th July 2006, 08:01 PM   #2
zobsky is offline zobsky  India
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toss the 4", get an MCM 8" (can't remember the number offhead) and put it in a small box (maybe around 0.3 cu. ft. ported enclosure, . .play around in winisd) and it should serve well for PC duties,

7 watt might not be optimal for a SMALL subwoofer.
"Not everything that can be counted counts, and not everything that counts can be counted." - Albert Einstein
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Old 14th July 2006, 05:17 AM   #3
dangus is offline dangus  Canada
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Most of the 4" drivers I've modelled are hard-pressed to go below 100 Hz, even in a ported box. Model it and see if there are any alignments that can get useful bass out of it. Maybe a bandpass box would give you some kind of thump.
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Old 14th July 2006, 07:54 AM   #4
lndm is offline lndm  Australia
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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.
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Old 14th July 2006, 02:33 PM   #5
sreten is offline sreten  United Kingdom
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without the parameters of the 4" driver box design is impossible.

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Old 16th July 2006, 08:47 PM   #6
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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!
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Old 17th July 2006, 08:53 AM   #7
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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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Old 17th July 2006, 11:18 AM   #8
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There is even a "real" 6.5" sub driver available but it wouldn't come cheap:



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Old 22nd July 2006, 11:39 AM   #9
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Tangband also do a 4" subwoofer driver, and a few slightly bigger ones.


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