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Old 4th July 2009, 05:58 AM   #1
wicked1 is offline wicked1  United States
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Default Small sub for computer speaker setup

I'm building a small computer sound system w/ 3" full range(ish) drivers. The full range will have a small 10 watt or so amp. I'd like a small sub to pair with it. I don't need it to go super low, and will be used for music more than for movie or game FX sounds. keeping it small is my primary concern, as I'd like to set it on my desk behind my monitor, or worst case, on the floor under the desk. I think it will need to fill in at around 130hz and below.

I'd appreciate any advice on drivers and cabinets. (not pre-made cabinets, but sizes, and type)
Thanks!
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Old 4th July 2009, 06:34 AM   #2
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I was in search of exactly the same question, and this is, what I finally built:

Office desk as open baffle subwoofer

Franz
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Old 4th July 2009, 06:39 AM   #3
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Franz,

Your Axiom is not really in the spirit of small

We built a 1/2 ft^3 (14 litre) CSS SDX7 common woofer for the uFonken.

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Old 4th July 2009, 03:25 PM   #4
wicked1 is offline wicked1  United States
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That wont work for me. My desk is open.. just legs and top. (good idea, tho in your situation)
And I'm doing this project sort of because I want to do some woodwork. I want to build nice matching cabinets for the speakers and the tiny-sub.

I just looked up that CSS SDX7 driver and saw some cabinet design plans. Even one for "as small of a footprint as possible for computer speakers"!!

Any advice as to what to drive it with, to pair w/ the little 10 watt amp for the full rangers?
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Old 4th July 2009, 05:03 PM   #5
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Quote:
Originally posted by wicked1
Any advice as to what to drive it with, to pair w/ the little 10 watt amp for the full rangers?
One of Jack Hidley's Foster plate amps for $35.

dave
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Old 4th July 2009, 05:24 PM   #6
wicked1 is offline wicked1  United States
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Dave, you are amazing.

(I'm listening to my tube amp w/ B. Purvine output tx's based on your suggestion, and out of fostex drivers, also based on info from you (and many others in that case). My ears are very happy.

I'll attach a photo of my mini audio-shrine. I have a ways to go compared to others here, but compared to my old system... well.. there is no comparison!
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Old 12th July 2009, 10:26 AM   #7
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Get something like a Tang Band 6" woofer, Linkwitz (sealed) it to 40Hz ish?

http://www.parts-express.com/pe/psho...number=264-832

I'm thinking make the box as small as the driver's magnet etc will allow, then use an eq circuit to do the rest. You will need a significant amount of power (100W plus), but with 13mm Xmax, you won't run out of movement for a while. Looking at the TS specs, Vas is very low, meaning the Linkwitz circuit wouldn't need huge gain to go to 40Hz. And a low resonance means 40Hz shouldn't be a problem. Maybe you'd want to go lower, but then there's problems with a small driver trying to move lots of air.
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Old 12th July 2009, 10:35 AM   #8
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by chris661
Looking at the TS specs, Vas is very low, meaning the Linkwitz circuit wouldn't need huge gain to go to 40Hz. And a low resonance means 40Hz shouldn't be a problem.
are you sure one will not needs lots of Linkwitz gain to get a flattish response from a small box?
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Old 12th July 2009, 01:57 PM   #9
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Vas is driver air compliance, which is related to how big the box needs to be (where bigger Vas is more box volume) modelled in a 5.6 litre box (yes, you did read that right), closed, -3db at 60 Hz, and 9dB gain needed at 40Hz to bring it to level.

Vented is another story. 11litre box, tuned to 38.33Hz will give -3dB at 38 Hz, which is low enough...

The problem is the lack of efficiency. Possibly buy 4 or 8, to make up for the lack of volume?

8 would go for 39L box. Sealed. 92dB/1W/m efficiency.
4 would be 22L. Sealed. 89dB/1W/m efficiency.
4 in ported would be 40L, 89dB/1W/m efficiency.
8 in ported would be 82L, 92dB/1W/m efficiency.

Personally, I'd go for 4 sealed, with Linkwitz, as that would balance bass response with volume fairly well.
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Old 12th July 2009, 04:16 PM   #10
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by chris661
Vas is driver air compliance, which is related to how big the box needs to be (where bigger Vas is more box volume) modelled in a 5.6 litre box (yes, you did read that right), closed, -3db at 60 Hz, and 9dB gain needed at 40Hz to bring it to level.
you've checked, I have to believe you.

Now to the sensitivities you quote.
$ in a box gives 89dB/W/m
therefore one in a box will give 6dB less, i.e. 83dB/W/m.
Now take off the 9dB gain to get that response and you end up with a net 74dB/sensitivity at the bass end.
max SPL is going to be low.
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