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Old 17th January 2008, 06:19 PM   #1
pdq2 is offline pdq2  United States
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Default Newbie needs advice on big horn subwoofer

I've always wanted to make a big horn-loaded subwoofer, and now I think I've got my chance. We're adding built-in cabinetry to our family room, and cutting across one corner, leaving a triangular space about 5 x 2.5 ft behind the built-in that I'm thinking I can put a big exponential horn in. This would go from the floor (throat end) up to the ceiling (~10 ft), then turn 90 degrees and come out of the corner over the built in, resulting in a horn about 11 ft long with a rectangular mouth around 2x8 ft.

I'm confused about drivers, tho. I've read online that a horn loaded driver should have a low Qts (one site said between .2 and .3) and an Fs/Qts ratio of >120. Is this true? I've also read that the Eminence Lab12 is a good driver for horn loading, but it's Qts is .38, and the Fs/Qts ratio is ~58.

I'm not looking for loud as much as minimally distorted low frequency, and just the fun of building such a beast. Any advice re a suitable driver (diameter, TS params, volume of sealed speaker chamber) and where to get it?

Thanks!
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Old 17th January 2008, 08:07 PM   #2
MaVo is offline MaVo  Germany
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get hornresp and simulate the horn. a variety of different drivers may work, depending on the horn shape. rough generalisations (like low qts) only get you in a direction but arent usefull for a single implementation. just find a horn driver combination, that has low frequency ripple and enough headroom for your intended spl.
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Old 17th January 2008, 08:59 PM   #3
pdq2 is offline pdq2  United States
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Thanks, Mavo.

Does HornResp dictate the size of the sealed box that the driver is mounted to?

That's one thing that I haven't really understood...
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Old 17th January 2008, 09:36 PM   #4
wg_ski is offline wg_ski  United States
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The size of the rear chamber is one of the input parameters in Hornresp - it won't pick it for you. High-EBP drivers will result in smaller rear chambers in general.

LAB12 has low EBP but was meant for a "relatively" short horn. One box is 1/12th of the full size mouth (in free space), and for that big of a stack, 13 feet of path length is "relatively" short.
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Old 17th January 2008, 10:27 PM   #5
GM is online now GM  United States
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Default Re: Newbie needs advice on big horn subwoofer

Greets!

Those old horn specs are based on being driven with a high output impedance amp that raised Qes/Qts considerably, so with today's vanishingly low output impedance SS amps you want a much higher Qes/Qts.

First you have to define the gain BW you want and find the horn's Fc before you can go driver shopping: Fc = sqrt(Fl*Fh).

GM
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Old 18th January 2008, 05:23 AM   #6
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Quote:
Originally posted by wg_ski
The size of the rear chamber is one of the input parameters in Hornresp - it won't pick it for you.
Hi wg_ski,

Just to clarify - it will if the "System Design > With Driver..." tool is used :-).

Kind regards,

David
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Old 18th January 2008, 10:28 AM   #7
MaVo is offline MaVo  Germany
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While playing with hornresp, i saw, that when the horn gets bigger in size, approaching an "ideal" set of paramters, the drivers parameters seem to matter less. Small compromised horns seem to be far more sensitive to changes in the drivers parameters.

Does someone know why that is so?
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