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    Help with designing box

    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.







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    Re: Help with designing box

    Quote Originally Posted by mud
    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.



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    Re: Help with designing box

    Quote Originally Posted by mud
    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.



    "There is no 'I' in Tag Team"

    Project 'rex: Coming Soon to An Eardrum Near You

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    Re: Help with designing box

    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




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    Re: Help with designing box

    Also, the sub has an EBP of 53, so it should work well sealed or ported, correct?




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    Re: Help with designing box

    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!




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    Re: Help with designing box

    Quote Originally Posted by mud
    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.



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    Re: Help with designing box

    Quote Originally Posted by LoneRanger
    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?
    Attached Thumbnails Attached Thumbnails Help with designing box-t8124a-ported-%7E3.png  
    Last edited by mud; 11-14-2003 at 05:43 PM.




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    Re: Help with designing box

    Here's a more helpful picture:
    Attached Thumbnails Attached Thumbnails Help with designing box-t8124a-top.png  




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    Re: Help with designing box

    I'd like to get this started tomorrow (Sunday), so would someone please tell me if my box design looks good? Thanks




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    Re: Help with designing box

    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




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    Re: Help with designing box

    Thanks for your help guys! I'll get it started and report back whenever I finish!




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    Re: Help with designing box

    When porting a box is it all nessesary to put that many interior walls?




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    Re: Help with designing box

    Quote Originally Posted by ssj2xxgotenxx
    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.



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