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Old 18th October 2003, 10:54 PM   #1
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Default Folded Horn PA sub in car

OK I know this isnt the PA pro audio board, and its not the car audio board either, but this is still audio and the fundamentals should be the same. Anyway, just wondering if anybody's tried this before. Bascially I have an extra Cerwin-Vega LR36 sub thats sitting around doing nothing. It is a folded horn loaded design. The rear of the woofer is sealed in a rather small space then it follows the folded horn out the front. It seems like a pretty efficient design, although being a PA sub it doesnt play that low, and it doesnt play as low as my EV SB180 subs.

At first I'm trying to construct a fiberglass enclosure for 2 15" car audio subs in the back of my 98 Corvette. But this projects taking forever and my $ is running out, so I thought about doing something in the meantime.

Now- heres my thinking. If I remove the cerwin vega sub from the PA enclosure, and built a sealed box to fit in the storage hole of (I calculate it can be around 2.0 cubic net with driver depending how high I make the box) my car, then it may not function too badly. The only concerns are

1) theres no folded horn so to speak anymore (however, being at the extreme rear of my car (its a coupe- with lots of cabin gain) with no back seat may prove to "horn load" the sub so to speak.

2) PA subs by their very nature do not play very low. Infact I have tried this before with 2 18" Electro-Voice EVX -180B drivers before in a ported box and no they didnt rumble like the typical car does, but they did sound very good. However- that was a ported box that was tuned rather high at almost 45 Hz, and this one I plan to do sealed, and with the car transfer function I think it may actually provide a very smooth response.

3) This is an 8 ohm sub, my car amp is rated at 1000 watts (it is a soundstream so it is brand name, not some generic POS) bridged at 4 ohms, however I find it to work best at 2 ohms bridged. Running a 8 ohm load, this amp doesnt seem to have the necessary voltage to be able to drive itself or the woofer to its max potential. However- PA subs are efficient, and maybe that will compensate for that.

Basically if somebody has done this before I'd like some input before I go doing this even though I'll probbly do it anyway.
If somebody who has put a labhorn driver in a car can chime in that might help me out some.
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Old 19th October 2003, 12:50 AM   #2
Volenti is offline Volenti  Australia
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While I havn't used that exact driver before I have used Vega subs in cars with good success (I'm an installer)

Set the sub up in the ~2cu'' enclosure like you have planned but have the driver facing either the rear of the car or facing up to the rear glass (whichever's easiest)

1) yes you will still (more or less) be horn loading the driver

2)if it performs anything like the other Vega subs I've heard before you should get a good response out of it, though more for simply "playing loud" than "booming"

3)Yes the amp probably will run out of voltage before the sub reaches max thermal power but on the flip side you'll have a very good damping factor to help control the sub.

oh, don't forget to pack the enclosure with fill...
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Old 19th October 2003, 12:59 AM   #3
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What's any of this got to do with horn loading?
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Old 19th October 2003, 02:22 AM   #4
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Quote:
Originally posted by Richard C
What's any of this got to do with horn loading?

The original design of the enclosure the woofer came in is a horn loaded design.
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Old 19th October 2003, 09:21 AM   #5
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incase you wanted to know ,im trying a 40hz horn in-car later.

www.geocities.com/sc00byd0159/40hzbasshorn.html

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Old 19th October 2003, 11:18 AM   #6
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But aren't those response predictions for a horn placed on at least one surface and operating into open-space (like a large room) and not a relatively small 'sealed' enclosure i.e a car?
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Old 19th October 2003, 01:10 PM   #7
Volenti is offline Volenti  Australia
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any horn loaded enclosure designed to operate in a car must take the existing structure of the car into account, ie; you make the internal space of the car an extension of the horn.

In well designed setups the car will actually achieve higher SPL with the front windows down (a clear sign you are actually horn loading the driver, rather than merely pressurizing the interior)

And the exact response is almost impossible to predict, since the large horn enclosure takes up so much space it changes the response in-car.
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Old 20th October 2003, 12:19 AM   #8
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Quote:
And the exact response is almost impossible to predict, since the large horn enclosure takes up so much space it changes the response in-car.
for sure

my graphs are in 0.5 pi situation.

if u want to measure the areas at various path distances from the sub in your car,go ahead

i expect that it may act like a conical type of horn a very short one if that,with crappy reflections and incorrect expansions along its way to the front windows

you could model an extension on an existing horn with the estimation of the car interior,it will be correct in some ways

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