Enclosure Size Calculation

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Sharp21

Member - Posts: 41

Joined: October 24, 2004

Posted: November 13, 2004 at 1:59 PM / IP Logged

How do I determine the optimum enclosure size for my sub? Is there a program that I can input its thiele parameters into?

Ive got a Jensen xs1212 12" sub. the document that comes with it isnt too good. it suggests 1.5ft for best response in a ported box, but the number seems kina arbitrary. Would it be better to go bigger?

Rushman

Silver - Posts: 380

Joined: September 28, 2004

Location: United States

Posted: November 13, 2004 at 2:14 PM / IP Logged

http://www.carstereo.com/help2/Articles.cfm?id=31

I find this page to be helpfull for calculating ported boxes.

http://www.carstereo.com/help2/Articles.cfm?id=5

this one might be helpfull for sealed boxes. Reply back here if you need more help or questions. Many expert people here always glad to help.

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jeffchilcott

Platinum - Posts: 2,483

Joined: April 11, 2002

Location: United States

Posted: November 13, 2004 at 2:21 PM / IP Logged

Frankly I wouldnt put a jensen sub ina 1.5 cuft ported box. Those subs couldnt handle the movement it would be alowed in a box like that. I would put it in a 1 cu ft sealed box, to try to keep it running for more then 3 months

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Sharp21

Member - Posts: 41

Joined: October 24, 2004

Posted: November 14, 2004 at 2:30 PM / IP Logged

thanks for the links.

Im gonna build a 1.5 foot ported box for the following reasons:

1. its my girlfriends car so she wont be listening too loud.

2. the subs are cheap!

its gonna be in the trunk (obviously). should i put the port onto the backside, facing into the back of the seat? or in the front, facing into the trunk?

Rushman

Silver - Posts: 380

Joined: September 28, 2004

Location: United States

Posted: November 14, 2004 at 2:56 PM / IP Logged

my best experience is to put the box as far in against the back seat as possible and aim the woofers and port holes towards the rear of the car , towards the tail lights.

99 F-one fitty

Pioneer Premier H/U

Alpine EQ

Kicker 1200 amp

4 Kicker comp 10s

6 kicker SS65.2 components

stevdart

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Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: November 14, 2004 at 9:30 PM / IP Logged

Build the box to the size best suited for the woofer. Why is it you want 1.5? Here's a link to a page that has the download link for WinISD Pro.... http://www.linearteam.dk/default.aspx?pageid=newdriver have fun!

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

uthinkuknoaudio

Silver - Posts: 760

Joined: October 08, 2004

Location: United States

Posted: November 14, 2004 at 9:39 PM / IP Logged

face it towards the tailights like rushman said...

"I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.

Search for other posts by uthinkuknoaudio

Sharp21

Member - Posts: 41

Joined: October 24, 2004

Posted: November 16, 2004 at 7:01 AM / IP Logged

Ok guys, thanks for the program. its definately a sharp learning curve!

So the box is looking more like 1.1ft. or 38.1L!

Now this program lets you "optimize your curve" which is great, if you know what you want the curve to look like! when I first input the data & hit go, the tuning frequency was 9.5hz. Is that right? Ive put it up to 38.1Hz, as that is the Vas value of my sub. Which one is right? Or should I tune it for some magical value in the middle?

Sharp21

Member - Posts: 41

Joined: October 24, 2004

Posted: November 16, 2004 at 7:02 AM / IP Logged

Oh, & one more question.

The program doesnt take into account the volume of the speaker itself or the vent correct? Should I add on 0.07ft to the box to make up for this, or just leave it as it is?

stevdart

Platinum - Posts: 5,816

Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: November 16, 2004 at 8:43 AM / IP Logged

No, the program doesn't know what size driver you have, what bracing you have, or the wall thickness of the port, so you need to add up everything in the enclosure except the air and add it to the overall volume. If the program came up with 9 Hz tuning, there was most likely something entered wrong in the parameters. Use database editing to correct any wrong parameters. When trying to find tuning frequency for a vented enclosure, the first try is usually at or just above the driver Fs....where the driver will play all frequencies that it is able to play and the port damps the freqs below Fs. Vas is part of the calculation, but is a volume measurement and not a frequency. When I looked up this sub the other day, I couldn't find anything on it to look at it for you. So experimentation might be the key here for you. Go with a sealed box unless you are absolutely sure of the driver quality and know the parameters have been carefully measured.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

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