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mud
11-11-2003, 09:25 PM
Hey, I'm trying to design my first box and could use some help. (Jmac maybe? you seem to be the resident audio god from what I have read here and elsewhere. :) )

Anyway, I recently picked up a 12" MTX T8124 and a Profile Clarus CL640 (225x1) cheap from a guy who wrecked his car. The sub came in a 1 ft^3 sealed box, and that just doesn't do it for me. It doesn't go deep enough or get real loud, so I figured I would build a new ported box. However, I have been having trouble coming up with a practical design in WinISD. Whenever I get something that looks like a good transfer curve, it needs an insanely long port. Max size for the box could be as big as 4 ft^3.

Thanks in advance for any help you guys can give, and trying to get a noob like me started in the world of DIY car audio.

LoneRanger
11-12-2003, 10:54 AM
Hey, I'm trying to design my first box and could use some help. (Jmac maybe? you seem to be the resident audio god from what I have read here and elsewhere. :) )

Anyway, I recently picked up a 12" MTX T8124 and a Profile Clarus CL640 (225x1) cheap from a guy who wrecked his car. The sub came in a 1 ft^3 sealed box, and that just doesn't do it for me. It doesn't go deep enough or get real loud, so I figured I would build a new ported box. However, I have been having trouble coming up with a practical design in WinISD. Whenever I get something that looks like a good transfer curve, it needs an insanely long port. Max size for the box could be as big as 4 ft^3.

Thanks in advance for any help you guys can give, and trying to get a noob like me started in the world of DIY car audio.

http://www.eatel.net/~amptech/elecdisc/spboxnew2.htm

their calculator is a little more accurate than winISD

also try making the port have a smaller opening. By my best guess, the port shouldn't be more than 20-30 square inches for daily use. The less port area you have, the shorter the port and vice versa.

LoneRanger
11-12-2003, 10:56 AM
Hey, I'm trying to design my first box and could use some help. (Jmac maybe? you seem to be the resident audio god from what I have read here and elsewhere. :) )

Anyway, I recently picked up a 12" MTX T8124 and a Profile Clarus CL640 (225x1) cheap from a guy who wrecked his car. The sub came in a 1 ft^3 sealed box, and that just doesn't do it for me. It doesn't go deep enough or get real loud, so I figured I would build a new ported box. However, I have been having trouble coming up with a practical design in WinISD. Whenever I get something that looks like a good transfer curve, it needs an insanely long port. Max size for the box could be as big as 4 ft^3.

Thanks in advance for any help you guys can give, and trying to get a noob like me started in the world of DIY car audio.

http://www.eatel.net/~amptech/elecdisc/spboxnew2.htm

their calculator is a little more accurate than winISD

also try making the port have a smaller opening. By my best guess, the port shouldn't be more than 20-30 square inches for daily use. The less port area you have, the shorter the port and vice versa.

mud
11-12-2003, 04:53 PM
Yeah, I have read through that, but it doesn't have any calculations for port velocity, right? That's why the ports end up so big in WinISD; trying to keep port velocity below 30 fps. Or maybe there is a port velocity calculator somewhere else on the site? I have only read through about half of the topics on basic car audio electronics, so I could have missed it.

Thanks, Orion

mud
11-12-2003, 05:01 PM
Also, the sub has an EBP of 53, so it should work well sealed or ported, correct?

mud
11-12-2003, 08:39 PM
I noticed while messing around in WinISD that the MTX recommended box/port dimensions would have a port velocity of upwards of 80 ft/s with 225 watts on the low frequencies. Is there something else that factors in, or would that be close to the actual port velocity? I don't suppose MTX (or any other decent company) would recommend an enclosure that would sound bad, so there must be something I don't understand. Please enlighten me about port velocity!

LoneRanger
11-13-2003, 10:10 AM
I noticed while messing around in WinISD that the MTX recommended box/port dimensions would have a port velocity of upwards of 80 ft/s with 225 watts on the low frequencies. Is there something else that factors in, or would that be close to the actual port velocity? I don't suppose MTX (or any other decent company) would recommend an enclosure that would sound bad, so there must be something I don't understand. Please enlighten me about port velocity!

don't trust the port velocity calculations from winisd. they're rarely if ever correct. i mostly just use common sense in matters like this. 20-30sqin of port is all you'll ever need for any single-sub daily driver box. The trick is to find the greatest port area in this range that will fit in your box without too many twists and turns.

and yes, you can go either way with that driver.

mud
11-13-2003, 09:41 PM
don't trust the port velocity calculations from winisd. they're rarely if ever correct. i mostly just use common sense in matters like this. 20-30sqin of port is all you'll ever need for any single-sub daily driver box.

Excellent. Thanks!

So here is a rough design for my box:
15" x 16" x 36"
2.9 ft^3
2" x 12.5" port 31.25" long
tuned to 25 Hz

A question on the port: is 2" too narrow, or does only the area matter?
Also, do I need any bracing?

mud
11-13-2003, 09:43 PM
Here's a more helpful picture:

mud
11-15-2003, 04:39 PM
I'd like to get this started tomorrow (Sunday), so would someone please tell me if my box design looks good? Thanks

CELLERBR
11-16-2003, 07:24 AM
Yeah that looks good man i dont think 2" is too narrow i went with 2.75" X 12" for 33" port area and port velocity is a a minimum i wouldnt think 25" would be too little you should be fine! Good luck on the box just take your time and it will come out peachy.
good luck,
Ian

mud
11-16-2003, 11:12 AM
Thanks for your help guys! I'll get it started and report back whenever I finish!

ssj2xxgotenxx
12-22-2003, 01:39 AM
When porting a box is it all nessesary to put that many interior walls?

LoneRanger
12-22-2003, 04:53 AM
When porting a box is it all nessesary to put that many interior walls?

The tuning frequency dictates the number/length of walls required. For his application, yes it does.