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Old 26th February 2008, 07:50 PM   #1
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Default Eminence Alpha 10

Hi all

I was wondering if anyone could help - I have an eminence alpha 10
(see http://www.maplin.co.uk/module.aspx?...&doy=26m2#spec
for specs)

so I would like to make a subwoofer capable of 30Hz - 100Hz will no ill effects (distortion etc). I can get a maximum of 50 watts into it (amplifier could be better)

Anyways... I was wondering about the size of the box - please try to keep it small ish as I am limited for space if you have any ideas - would 30Litres be any good???

Thanks
Chris
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Old 26th February 2008, 08:14 PM   #2
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Sorry but I don't think it will work very well. The fs is too high for any conventional boxes to get down to 30Hz. You could try a horn (or a tapped horn) but the Q is a bit high. Maybe one of the horn experts here could model it for you. Theoretically I suppose you could do it in a 10 cubic foot BR but I have my doubts.

The only other option I see is a Ripole as it lowers the resonance a little. Still have my doubts though.

This driver is a nice driver for it's intended application but it is not really a subwoofer driver. So how about it ladies and gentleman? Could he do it in a tapped horn?

mike
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Old 27th February 2008, 07:03 AM   #3
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Default equalisation

Hi again.

suppose i could equalise it to play the low notes - you can buy/make bits of clever circuitry which increase the amplifier's output as the notes go lower...

Wouldn't the room resonance also help the low notes (people think they start helping around 40Hz)

I'm only doing this because the subwoofer i have is a 20W 5 inch driver in a tiny box which distorts with anything below 60Hz - so anything would be an improvement...

Thanks for the quick reply
Chris
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Old 27th February 2008, 07:03 AM   #4
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Default driver

if you surf around, you won't find a better NON-CAR driver for 30, it beats some 12" driver that are out, and i wanted to keep it compact... so 10cu. foot is a bit out of the question...
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Old 27th February 2008, 08:57 AM   #5
Thawach is offline Thawach  Thailand
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hi

isobraric design you can build about 30 litre. your driver has fs=50 hz it cannot repond at 30 hz. and at 30 hz i think your amp cannot supply the power.


regards

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Old 27th February 2008, 11:18 AM   #6
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i could mkae the target 40Hz if that would make things easier...
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Old 27th February 2008, 12:24 PM   #7
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That driver seems to benefit from horn loading due to the high FS...

It is a nice driver tho, just don't expect it to go real low in a sealed or bass reflex box.
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Old 27th February 2008, 01:14 PM   #8
Thawach is offline Thawach  Thailand
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hi chris


the specification of your driver can not design a small box.
if you build a small box. you cannot hear at 40 hz.

thanks
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Old 27th February 2008, 04:09 PM   #9
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You can make any high fs driver work in a small box and have a low f3 just by increasing the actual or apparent mass of the cone. Horn loading is one way but takes allot of volume, the other was is slot loading. By firing the woofer into a panel that forms a slot where the air escapes out the side you increase the mass and lower the fs. The basic physics are a cone is a weight and the air in the enclosure is the spring. Now imagine the mass is pulled and let go, it will start to oscillate at a frequency that is dependent on the softness of the spring and the weight. To have a lower resonance you can a) lower the spring force (bigger box/softer suspension) or b) increase mass (heavier cone). Some have experimented with adding weights to the cone but this is very dangerous as you can unbalance the cone or create breakup modes. Slot loading works well the only trade off is that the q will go up and efficiency will go down but thats acceptable to get a woofer that will play down to 20Hz. The reason that we have small subwoofers is because manufactures are willing to trade of efficiency for size. Power is getting cheaper so its not as much a problem as it once was. Car audio is the extreme with subwoofers that can work in tiny boxes and have 20mm+ xmax and low f3 but they need 1000w to get the same output that a pro audio 18" woofer with a light cone and a 8ft^3 box will produce with 50W. I have taken a similar situation and put a passive radiator right on it as if it was a isobaric box and then you can mass load the crap out of it and get 10hz f3s. Have fun.
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Old 27th February 2008, 04:13 PM   #10
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what is isobraric design????

is it easy(ish) to make????

if so, will 36mm chipboard do for the construction????
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