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Old 25th March 2007, 09:49 PM   #1
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Default How to make the best from an 8" sub

A friend of mine gave me a 8 inches subwoofer with a 9,5 liters box, made for small cars, and i'm using it here in my vintage, but the speakers have more bass than this little one.

The box is made of polyetilen (plastic), thats why is not so good.

What is the best way to use an 8" sub? vented? sealed? band pass? LT?

I don't really need it for powerful-ground shaking-soundsystem, just for a good quality system, and for fun, of course!

Here are the specs:

Power RMS: 120
Power PMPO: 240
Impedance: 4 ohms
SPL 1 W @ 1m (dB) : 86
Frew. Response. @ -10 dB (Hz) 40 to 2,5 k
Ressonace Freq.(Hz): 40
Magnet Weight: 620g
Coil Diameter: 38mm

Qms: 15,8
Qes: 0,65
Qts: 0,62
Vas: 20l
Sd: 0,022m
Vd: 77,9cm
Xmax: 3,5mm
Bl: 8,1 Tm
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Old 25th March 2007, 10:27 PM   #2
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Location: Near Vancouver
Hi Denis,

I think you have a woofer rather than a sub so it might be hard to get a lot of extension. Down 10 dB at 40 Hz might need to be EQ'd. Have you thought about a box and a plate amp?
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Old 25th March 2007, 10:45 PM   #3
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good point!

but it is in mid term between a subwofer and a woofer, because it doesn't sound like a woofer and don't go to low frequencies, at least in this original box.

Click the image to open in full size.
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Old 27th March 2007, 02:15 PM   #4
OzMikeH is offline OzMikeH  Australia
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If it has PMPO figure stated it probably isn't worth building a box for.
86db/w is pretty poor efficiency too. this means you need a much bigger amplifier for the same noise.
look for something that has a higher efficiency. worth spending a little more on a louder speaker than a lot more on a bigger amp.

I have experienced bass you can feel from a 1W amp with a 103dB/w speaker, this is an extreme case and you don't want to know what that driver cost. But Low power amps are a very good idea in a car, if you can get away with a 20W amplifier everything stays a lot cheaper (no voltage step up circuitry required for amplifiers)

You say a Vintage, I presume you are talking about a car?
Please excuse my rambling if I have missed the point.
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Old 27th March 2007, 03:11 PM   #5
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OzMikeH, I got your point. I thought it would be good build a box just for fun, but if it will sound like the original box I'll leave it behind.

What I mean for vintage, is that I use an old 80's receiver in my bedroom plugged in my computer.
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Old 27th March 2007, 03:24 PM   #6
AndrewT is online now AndrewT  Scotland
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Location: Scottish Borders
that Qts tells you & the rest of us that the driver is not suitable for use in a vented box.
It is also above the sensible limit for use in a sealed box. If fitted to a sealed box it will need to be very big to keep the final Q below 0.9 and preferably below 0.8. Even those Qs are likely to be boomy (one note bass).
I think you could be talking about use in an open baffle, but the low Xmax would mean pretty low maximum output and that also rules out EQ as well, since it uses up enormous cone excursion to extend the bass lower.
Finally, forget Sub-bass, you are struggling just to get any bass out of it.
regards Andrew T.
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