Box tuning...

[deernet 6]

So I ordered a BTL 18 today, and I think I'm going to base my enclosure off the one for the XCON optimal one thats here on the site. It says that box is tuned for 30 hz. Fi recommends tuning to 32 hz for the BTL. I don't really figure that the 2 hz will make that much of a difference, but I could be wrong.

What I'm planning on doing is putting the port on the other side of the box, so that the driver would be facing up towards the roof of the vehicle, and the port would be facing forwards, toward the front of the vehicle. My question is will putting the port on the wider side of the box, (25.25 in. vs 22 in.) put me closer or farther away from the 32 hz?

Also, I'm planning on covering the box in bed liner, like in OldSkool_08's build ( OldSkool_08's Incriminator and Sundown build. - SSA Car Audio Forum ). I thought that looked pretty badass.

[KU40 173]

I don't understand what you mean by if putting the port on the wider side of the box will affect tuning. If you keep port area and length the same, tuning won't change.

But chances are the setup will be louder with the port facing the rear rather than forwards. I'd at least experiment once you get it in.

[akrod2as 2]

You'll be changing the port area so it will affect tuning slightly.

[deernet 6]

You'll be changing the port area so it will affect tuning slightly.

Thats what I was thinking, but will making the port area bigger make the frequency its tuned for higher or lower?

[mr.sagat 10]

You'll be changing the port area so it will affect tuning slightly.

Thats what I was thinking, but will making the port area bigger make the frequency its tuned for higher or lower?

higher

[KU40 173]

You'll have to elaborate on your definition of "wider side of the box." If you're talking about the baffle being wider in the x direction as you're looking right at the box, as in height stays the same, the port area shouldn't be affected.

Either way, you can compensate to make the port area the same size. If the port will be taller, just make it less wide. So if you have a 25" tall x 4" wide port in a drawing but your box is only 20" tall, make the port 20" tall x 5" wide. Same 100 sq. inches of port either way.

[deernet 6]

OK, as per this picture, I was talking about the port being on the bottom. I think that would make the port height 23 3/4 ID instead of 22 in. ID. I've been thinking about this alot though, and that would change the whole geometry of the port. I think I'll just go with the original design and then I won't have to worry about it. I am going to put in some either 6x12" or 12x12" 3/4 plexi windows though. As per the picture, I'll be putting them on the top and bottom of the box, on opposite sides of the sub. I'll be putting double pieces of MDF on the top and bottom so that I can mount the windows flush.

I'm going to order the plexiglass from this place: eStreetPlastics - plexiglass sheet supplier

They've got 6x12" pieces for $10.69 and 12x12" pieces for $18.49 a piece.

I'm also going to get some LEDs from this place: LED Module Aluminum Housing High Power

The wide angle one is the same one that Steve Meade used in the 2x T15K Escalade build.

I've got a question though, should I use caulk on all the angles inside the box? I mean if I use wood glue on all seams, it should be pretty air tight, but some silicon caulk couldn't hurt, right? I've seen in a lot of Steve's builds he'll fiberglass the inside of enclosures, what advantages do you get from that, just a tighter seal? If I end up using the bedliner on the outside, that will be an extra layer of shit that should give some sealing properties I would think.

[KU40 173]

Putting the port on that other wall won't change any geometry of the port. I don't even know what that would mean. Anyways, as I said, you can just compensate by changing the height of the port since you're changing the width. 22 x 5 = 110 sq. inches of port. 110 / 23.75 = 4.63. Therefore, put your port on that other side where you want it and make it 23.75 x 4.63 (5/8 is close enough and can be used just fine). Length of the port stays the same.

This really isn't rocket science. Chances are you'll introduce more error into the system just by building the box than changing the port like this in the drawing stage.

[deernet 6]

Putting the port on that other wall won't change any geometry of the port. I don't even know what that would mean. Anyways, as I said, you can just compensate by changing the height of the port since you're changing the width. 22 x 5 = 110 sq. inches of port. 110 / 23.75 = 4.63. Therefore, put your port on that other side where you want it and make it 23.75 x 4.63 (5/8 is close enough and can be used just fine). Length of the port stays the same.

This really isn't rocket science. Chances are you'll introduce more error into the system just by building the box than changing the port like this in the drawing stage.

What I meant by changing the geometry is that it would make the port wider all the way back to where it goes into the main chamber. Plus, it would leave part of the brace not supporting anything. I think it will probably sound just as good doing it like the original design, I'll be facing it up, and have windows on both of the long sides.

Your probably right, that I'm thinking about it too much, I just want to make sure that its done right after I've spent so much on a sub, I want to have the box as close to perfect as I can.

Another question, I was planning on using a terminal cup. I've seen where a lot of people on here have just used bolts run through the box, but I thought the terminal cup would make it look cleaner. I think I'll either use one of the dual terminal cups or use two so that I can use one set of contacts for the LEDs. Anyone think theirs a better way to go about it?

[KU40 173]

If you have the sub facing up will you even still have the bracing in there? Seems to me if you put the sub in the middle of the topside, that would be where the brace is in that picture.

Terminal cups are ok, just be prepared to caulk on the inside hole of the cup. Those things always leak air.

[deernet 6]

If you have the sub facing up will you even still have the bracing in there? Seems to me if you put the sub in the middle of the topside, that would be where the brace is in that picture.

Terminal cups are ok, just be prepared to caulk on the inside hole of the cup. Those things always leak air.

No, I mean I'm going to build it exactly like it is in the picture, but face the enclosure so that the sub is firing towards the roof of the vehicle.