Two JL Audio 10W3v3 drivers for a car - diyAudio
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Old 25th November 2008, 10:22 PM   #1
sploo is offline sploo  United Kingdom
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Default Two JL Audio 10W3v3 drivers for a car

I've been asked to create a box for a pair of JL Audio 10W3v3 10" sub drivers for a car.

For home use, I'd usually take two sub drivers, and put them in a sealed enclosure (of twice the volume for a single driver) and mount them opposing (to cancel out vibration).

The guy wants the unit to be as shallow as possible, so I'm planning on having them firing up, with the magnets resting on the bottom of the box (with some support around them, to reduce shear loads on the mounting flanges).

What I'm wondering is whether I should go for a single (double volume) sealed enclosure, or make a single box with two sealed chambers, one for each sub?

For car use, is any stuffing/damping material in the box recommended?
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Old 26th November 2008, 03:33 PM   #2
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There are a lot of questions I could ask to make a better suggestion. The first would be what sort of environment they will be in? (Trunk? HAtch? Truck? SUV?) the second would be why so shallow?

The bottom line is that you will get a slightly lower, in car F3 with both drivers in the same volume. You will get a slightly tighter response and few hz higher F3 with them in separate enclosures. Power handling might also be slightly higher with them in separate boxes.

You might also consider coupling them to the car. A fiberglass enclosure could be even shallower and would couple the entire enclosure to the vehicle helping a bit. Down firing could be yet another consideration to protect the cones and help load the vehicle too.
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Old 26th November 2008, 06:05 PM   #3
sploo is offline sploo  United Kingdom
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Quote:
Originally posted by musgofasa
There are a lot of questions I could ask to make a better suggestion. The first would be what sort of environment they will be in? (Trunk? HAtch? Truck? SUV?) the second would be why so shallow?

The bottom line is that you will get a slightly lower, in car F3 with both drivers in the same volume. You will get a slightly tighter response and few hz higher F3 with them in separate enclosures. Power handling might also be slightly higher with them in separate boxes.

You might also consider coupling them to the car. A fiberglass enclosure could be even shallower and would couple the entire enclosure to the vehicle helping a bit. Down firing could be yet another consideration to protect the cones and help load the vehicle too.
Many thanks for the response.

The car is a Seat Leon - a (for the UK market) mid sized hatch. I'm not sure why he wants the box so shallow - I guess so he can fit something else in the boot (that's the bit at the back, in the UK, only elephants have trunks ).

That would be a good argument for down firing I guess - it would mean the unit would be a little thicker, to raise the drivers up from the floor, but would allow stuff to be piled on top of the box without risk to the drivers. Is there any minimum distance required between the driver and floor of the trunk (other than enough to stop them being crushed)?

I've never worked with fiberglass, so it's not a route I could take at the moment. However, with the magnet on the base of the box (assuming 3/4" MDF) even an infinitely thin fiberglass enclosure would only be 2 x 3/4 (1 1/2") shallower. However, I expect some thickness of fiberglass would be required to make a strong box, so would you really gain that much?

I'm leaning towards putting two in the same volume, as that looks like a good bet.
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Old 26th November 2008, 08:31 PM   #4
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Considering it's a hatch, I would definitely put them both in the same volume. I haven't checked the specs on the W3 but I know they sound pretty decent in sealed configuration.

The main thought behind fiberglass was to use the spare tire well as the enclosure and build a "false floor". Then you can build a strong grill to go over the drivers for protection and basically use no space in the car.

Short of that, your options depend on placement. I could get a LOT of SPL out of those drivers in a hatch, but the box would be big and it sounds like this isn't the objective. If SQ is more the concern you have a lot of options. Up firing will probably give you the most crisp sound while back firing will likely produce the deepest and highest SPL. Down firing would need to be at least 1.5 to 2 inches off the floor. The excursion alone will need close to an inch and loading them much closer might choke them down a bit. Be careful making the box so shallow as to have the magnet touching the back. You do need some airspace for them. I believe they will work in 1 cu ft, but I wouldnt go that small unless they were pointed at the floor. 1.5 per sub would be better. A common chamber of 2.5 internal will work if going sealed.

Now if you want those puppies to bark with some authority, lets get into a much larger, ported box lol.

Take care,
Robert

PS remember everything depends on your goals. What kind of sound you are after will make a big difference
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Old 27th November 2008, 04:42 PM   #5
sploo is offline sploo  United Kingdom
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I don't have access to the vehicle, so I guess placing something in the spare wheel well is probably out (and I guess he probably wants to keep his spare wheel)!

It sounds like up firing is the old feasible option then, though why would it be a problem to have the magnet touching the base of the box? The magnets aren't vented.

Having now got the manual for the drivers, it recommends 17.7l (0.625 cubic feet) for sealed - quite small really. I knew the ported requirements, and this would've made a box too big for his liking, hence the move to sealed.

This would result in a dual sub enclosure of only 1.25 cubic feet, though I did play with various box sizes on BassBox Pro, and if that's to be believed, it doesn't make a huge difference in having a bigger box... which did surprise me a little.
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Old 29th November 2008, 09:05 PM   #6
DaveCan is offline DaveCan  Canada
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Here's a link
http://mobile.jlaudio.com/products_s...p?series_id=24

Dave
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Old 29th November 2008, 09:52 PM   #7
sploo is offline sploo  United Kingdom
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Thanks Dave... but that's where I'd downloaded the manual from! Good site though; plenty of info on enclosure types.
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Old 30th November 2008, 10:02 PM   #8
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Having the box fire up and being thin will work. It is a compromise, but certainly not a problem. I have used those subs in many sealed, ported, and band pass enclosures and they aren't really picky.

Good luck.
Robert
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Old 1st December 2008, 09:56 AM   #9
sploo is offline sploo  United Kingdom
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Sounds good, thanks.

I did a design over the weekend - the box will be about 80cm wide, by 40cm deep, by 19cm tall. Construction from 3/4" MDF.

It results in there being about 2cm of space between the magnets and the floor of the box. Total volume is just a little bit larger than the recommended 2 x 17.7l (plus extra space for the driver displacements).

So... should I be stuffing this with anything? I can't think internal reflections are an issue (low frequencies only) so it would surely just be a case of stuffing to make the box appear larger to the drivers. Any point?
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Old 1st December 2008, 03:31 PM   #10
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I would say no. Been building subs for too many years and in a car, unless your goal is absolute sq, I wouldn't worry about stuffing. It is subjective though. Back in the day, I would stuff my kicker boxes and notice a slight drop in F3, but only a few hz and only with lower compliance woofers. The JLs aren't likely to sound any different.

Like I said though, it is subjective so YMMV.

Good luck,
Robert
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