tuning a sub box?

[3G]

what do ppl mean when they say tune a sub box and how do u do it?

[97'Scort]

Depends what kind of box you're making and what kind of sound you're looking for. For all boxes, volume plays the largest role, with porting coming second. All speakers come with a recommended volume that they should be played in, and some even include a range of volumes. A smaller volume in a sealed box will have a faster, punchier response, whereas a larger box will be deeper. I'm not great at making ported boxes, especially bandpass; they take some serious work. Check the manufacturer's website for patterns. Porting will give you the best air movement, but can reduce loading on the speakers at low frequencies, causing them to "see" more power than they might like.

If you're looking to "tune" a pre-made box, your only bet is to change the amount of fill or just get a new box. You can also adjust where your sub is in your trunk by moving it back and forth: sometimes you can get a sweet spot where you get constructive interference and can give you a 2-3dB boost in the driver's seat.

[Crymson]

You know how when you blow air over wine bottles with different ammounts of water in them and get a different sounds? That's like tuning your port, by changing it's parameters to different frequencies. Different lengths and volumes will "tune" the port to different frequencies and harmonics ther-of.

[wrxer1]

A "proper" sub box is extremely important. I've heard very expensive systems sound quite sub-par.
One of my last installs, an individual put 900 clean watts into a nice focal sub, then into a store bought enclosure:thumbsdow
Only after we heard it did he request a custom box!

[3G]

Anybody running JLw7's 12 inches? whats the ideal box for these?

[97'Scort]

JL has sub box sizes on their website for all their subs, if I remember correctly. They also sell boxes that are pre-made for specific subs, especially the W7's.

[Crymson]

I remeber when i used to do this, there were lots of programs you could find online that caculated what you wanted to do. They had a majority of popular subs stat's imputed, but you could imput your own paramters. It would generate theoretical frequencies vs DB plots so you could tune the box for Max spl or for the whiteest spectrum if you wanted. I'm sorry but i can't remember the names. I'm sure a quick google of sub box design programs would give you a number of hits. They weren't the most user friendly programs, and required that you understood what the parameters of the sub meant.

[3G]

I found this online, it is only for 1, if i have 2, do I just double the size or what?

[97'Scort]

Yup. You basically make two boxes into one by putting a solid centre baffle in it.

[3G]

would it be the same if I didnt put the center baffle in it?

[97'Scort]

I wouldn't have two subs playing in the same cavity if I could avoid it. The pressure from one will load the other and vice versa, giving you decreased performance. Your box will have to be the same size regardless, just put the solid separator in the middle.

[3G]

2 last questions, would it ruin the sound quality if i make the box 7-8 inches shorter than what it suggests but keep the lengh and height the same?


Also what all do I need other than the wood and saw to build it?

[Crymson]

the dimensions aren't as important as the volume, as long as the internal volume stays the same, or stays to spec, you'll be fine with shortening one direction and lengthening the other.

[3G]

Originally posted by Crymson
the dimensions aren't as important as the volume, as long as the internal volume stays the same, or stays to spec, you'll be fine with shortening one direction and lengthening the other.

So say I take 3-4 inches off the lengh, i should add 3-4 inches to the width or height, right?

[97'Scort]

Pretty much. Just make the internal volume the same and you should be good to fly.

As for materials:

- MDF, proper thickness
- Table saw
- Jigsaw
- Carpenter's square
- Drill
- Clamps
- Router (optional, you could use the jigsaw)
- Circle templates
- Carpet or similar covering
- Elmer's spray glue
- Wood glue
- Nails & nail gun (you can use screws if you want, just try and countersink the heads)
- Staple gun
- Fibreglass insulation or similar fill (for sealed box)
- Silicone caulking

I'm going to assume a sealed box here. Measure out your sizes, use cardboard to make yourself some templates if you need to. Don't skimp on the MDF thickness as those W7's can create enough pressure to blow a low-quality box apart. After cutting all your MDF, fasten together with nails and wood glue. Make sure you use the glue, or you won't get a proper join. After that's all together and the glue cured a bit, caulk all the openings with the silicone to really make it airtight. You can put a bead of silicone around the openings for the subs as well, just let it dry before mounting the subs. This will seal around the edge of the sub when you fasten it down. Put the fill (insulation) inside the boxes, wire in the subs and mount them.

Check JL's website for the video on the proper procedure on mounting the W7's as there is a bit of a trick to it.

Plug in and enjoy!

[3G]

Originally posted by 97'Scort
Pretty much. Just make the internal volume the same and you should be good to fly.

As for materials:

- MDF, proper thickness
- Table saw
- Jigsaw
- Carpenter's square
- Drill
- Clamps
- Router (optional, you could use the jigsaw)
- Circle templates
- Carpet or similar covering
- Elmer's spray glue
- Wood glue
- Nails & nail gun (you can use screws if you want, just try and countersink the heads)
- Staple gun
- Fibreglass insulation or similar fill (for sealed box)
- Silicone caulking

I'm going to assume a sealed box here. Measure out your sizes, use cardboard to make yourself some templates if you need to. Don't skimp on the MDF thickness as those W7's can create enough pressure to blow a low-quality box apart. After cutting all your MDF, fasten together with nails and wood glue. Make sure you use the glue, or you won't get a proper join. After that's all together and the glue cured a bit, caulk all the openings with the silicone to really make it airtight. You can put a bead of silicone around the openings for the subs as well, just let it dry before mounting the subs. This will seal around the edge of the sub when you fasten it down. Put the fill (insulation) inside the boxes, wire in the subs and mount them.

Check JL's website for the video on the proper procedure on mounting the W7's as there is a bit of a trick to it.

Plug in and enjoy!


Hey thanks for the information, i appreciate it, i will be getting Totem to cut the pieces of MDF to size then I will cut the circles myself and put it together, my subs are w1's not w7 if that matters

[97'Scort]

Originally posted by 3G
Anybody running JLw7's 12 inches? whats the ideal box for these?


Originally posted by 3G
...my subs are w1's not w7 if that matters.

Heh, just going with what you gave me, bro. I should have noticed it on the schematic you gave though.

You'll still want some 3/4" at LEAST. I'm running a 10W1-4 until I get my Focal stuff in: the little JL pounds when it's tuned right! There's 1" and thicker MDF in the pre-made JL box that it came with.

[3G]

Originally posted by 97'Scort




Heh, just going with what you gave me, bro. I should have noticed it on the schematic you gave though.

You'll still want some 3/4" at LEAST. I'm running a 10W1-4 until I get my Focal stuff in: the little JL pounds when it's tuned right! There's 1" and thicker MDF in the pre-made JL box that it came with.


So if I need a box with a smaller length, do i just keep playing around with the width and height until I get a volume close to the recomended?

[97'Scort]

Yup pretty much. Just make sure you still have enough depth for the two subs. You might want to try something like this. (http://mobile.jlaudio.com/products_enclosures.php?menu=9&prod_id=328)

When doing volume calculations, make sure you use the INTERIOR dimensions, with the baffles, brackets and subs included in your calculations. Missing those can account for several litres of volume difference.