box w/less then recommended volume

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nyguy4u

Copper - Posts: 148

Joined: December 31, 2003

Location: New York, United States

Posted: March 27, 2004 at 10:25 PM / IP Logged

I have 3 JL 15" W3V2's that are going into a 2001 PT Cruiser. Box will be sealed..made of fiberglass, and sides..bottom.. and back of 3/4 MDF, front will be fiberglass. 80% of the MDF portion of the box is done. Here's my question.. I wasn't going to chamber off the subs, I was going to have the 3 subs in one common chamber, I was told NOT to do that. So i'm taking everyone's advice and building a chamber for each sub.

Now, if anyone knows the back of the PT, they will know it's not all that big. Looking at the specs from JL.. here's the recommendations for a sealed enclosure..

22"W x 16"H x 14.75"D ..volume 2.125ft

Now, I am very limited for space, measuring each chamber of my box, it will end up being..

16"W x 18"H x 16"D

I don't have much of a choice, I used every inch of the trunk, and that's all I can get in there. Question is, being it's not exactly to what JL says (it will be smaller then what they recommend), what will happen?. Will it sound odd in anyway?. Again.. not much of a choice for my space, so i'm hoping it will be ok. My width is the biggest problem, pretty much the width of each chamber will be the same width of the sub, but at the same time.. i'm adding approx. 2" of height and depth over of what they recommend. So i'm assuming it will balance out.

Am I right?

DYohn

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Joined: April 22, 2003

Location: Arizona, United States

Posted: March 27, 2004 at 11:18 PM / IP Logged

You're putting 3X15" JL subs in a PT Cruiser.?!? Jesus... OK, you made the first good choice about not sharing air space. These babies could destroy each other in one enclosure. With each chamber at 16X18X16, you have almost exactly 2 CUFT for each sub. Taking into account the displacement of the woofer, you are at about 1.6 to 1.7 CUFT, which is a great size for a small sealed enclosure for this driver. You will end up with a great SQ system. The only negative effect that might (and I say MIGHT) be noticable is a lack of very low bass, as a sealed enclosure this small will result in an F3 of about 35 to 40Hz and the increased dampening from the small air space will limit the woofer's excursion. I highly recomend filling the chambers 3/4 full with acoustic stuffing to increase the effective enclosure size and regain some of the lost low frequency ability. You should be fine. How are yu powering them?

DjRDifacs

Copper - Posts: 64

Joined: June 16, 2002

Location: United States

Posted: March 27, 2004 at 11:19 PM / IP Logged

you'll be alright ....but I would rocommend all three drivers sharing the same air space (if wired in parralel). Just make sure you brace well and you're good to go.

superstreet786

Silver - Posts: 339

Joined: August 12, 2003

Location: United States

Posted: March 28, 2004 at 5:40 PM / IP Logged

if your volume is less that recommended you will probably blow your sub/subs in time

---- 1996 Chevy S10 ----

1 Lightning Audio S2.600.2 Amp

2 Lightning Audio 12" Subs

1 Lightning Audio 1 Farad Cap

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DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: March 28, 2004 at 5:50 PM / IP Logged

Same air space: NO. That is foolish and can lead to all sorts of bad things like lowered SPL, blown subs, etc.. Smaller enclosure blows subs: NO, not by itself. It actually allows them to handle more power. They just won't play as low with the same efficiency as they would in a properly sized enclosure. But whay nyguy4u is proposing is actually the RIGHT SIZE sealed enclosures for these subs. Go for it. Don't forget your earplugs in the PTC.

Alpine Guy

Platinum - Posts: 2,478

Joined: October 18, 2003

Location: Canada

Posted: March 28, 2004 at 6:00 PM / IP Logged

The only draw back of less air space is that you will need to feed them more power to get the full capabilitys.

2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.

xTimx

Copper - Posts: 354

Joined: September 13, 2002

Location: Canada

Posted: March 28, 2004 at 6:27 PM / IP Logged

3 15"s in a pt cruiser...dude you ahve to post pics of when your done this project!

xTimx

nyguy4u

Copper - Posts: 148

Joined: December 31, 2003

Location: New York, United States

Posted: March 29, 2004 at 12:01 AM / IP Logged

Thanks for the replies so far guys... really really appreciate it!!

As far as the 3/4 stuffing.. do I just lay a layer of 3/4 of that stuff on the floor of each chamber and that's it??

You can be sure i'm going to post pictures of this when it's done. Should be soon too, because I want my car back on the road!!

Thanks again!!!

DjRDifacs

Copper - Posts: 64

Joined: June 16, 2002

Location: United States

Posted: March 29, 2004 at 1:49 AM / IP Logged

DYohn wrote:

Same air space: NO. That is foolish and can lead to all sorts of bad things like lowered SPL, blown subs, etc..

If a pair of drivers (or more) are wired stereo, then yes it would be foolish to share the same air space. The reason why is because music tracks tend to bounce from the left to right channel during play back, and would throw the drivers off sync with each other. Another reason why is because the left channel could sometimes be recorded louder than the right (or visa versa).

Now if they are all wired together sharing a mono output, two or more drivers will work together and act as one, delivering lower bass notes then they would in seperate chambers.

Either way will work, this is my suggestion and my experience with enclosures.

Ketel22

Silver - Posts: 976

Joined: August 23, 2003

Location: United States

Posted: March 29, 2004 at 1:54 AM / IP Logged

in theory your belief is correct, but all drivers are not exactly identical. the smallest of manufacture errors can throw the subs against each other in a shared chamber.

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