Math question for sub enclosure
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=36404
Printed Date: May 12, 2024 at 9:21 AM
Topic: Math question for sub enclosure
Posted By: fugit
Subject: Math question for sub enclosure
Date Posted: July 29, 2004 at 12:31 PM
Ok, this may sound dumb to all you math geniuses but I really suck/hate math. I keep getting two different answers when I do some calculations from this site. https://www.diysubwoofers.org/sld/sealed1.htm I'm using the theile small parameters for an alpine type-r 1021d. I have a vb of 12.13 that I've gotten more than once. I also got 28.001 one time, but I don't know if I'm doing these right. If the 12.13 is right, then that would be .42 cuft. That seems kind of small so I'm really not sure. If anyone wants to check my work the info is here. https://iweb.alpine-usa.com/pls/admn/item_info?p_item_name=SWR-1021D&p_category=70&p_subcategory=150&p_main=10&p_more=y Should I even bother, or just go with manufacturers reccomendation? ------------- "I'm Rick James bi***, enjoy yo' self Ah Ah Ah"
Dave Chappelle as Rick James
Replies:
Posted By: Ketel22
Date Posted: July 29, 2004 at 12:38 PM
i have the dual 4 ohm version of that sub and i liked the way it sounded at about .75 cuft. but the only way you will find a box you will be satisified with is to build multipul sizes and try the sub in them.... ------------- Quad L Handyman services
Posted By: stevdart
Date Posted: July 29, 2004 at 3:48 PM
You're right, it comes up a smaller size than is recommended by the manufacturer. One, always build within the parameters set by the manufacturer. Two, use tesimonials from trusted resources (like Ketel22 above) for ideas of what has been tried and found good. The displacement of the driver is .092, so the minimum airspace your enclosure should have before mounting the speaker is 0.592 ft3. The max would be 0.892. A rule on the site you linked says that a larger box size will need a bit more power. I would tend more toward the larger half of the scale if your amp has plenty of power to drive the subs. But if your leaning more toward maybe just having enough power, tend a little toward the small side. Also, judge the size by looking at your midbass speakers. If they bang out good punch at 80 Hz, make the box a little toward the large size and set the crossover to 80 or below. But if the midbass speakers are lacking the deep punch, make the sub box a little smaller to fill that gap. When you're on the smaller side, you can add polyfil to "increase the size", too.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: fugit
Date Posted: July 29, 2004 at 4:23 PM
Thanks for yet another great answer Stevdart. I'm glad I'm not as dumb as I thought. The latter half of your post was very informative as well and I'll definately remeber that. Thanks again! ------------- "I'm Rick James bi***, enjoy yo' self Ah Ah Ah"
Dave Chappelle as Rick James
Posted By: stevdart
Date Posted: July 30, 2004 at 12:51 AM
Actually I think you're one of a few to try to tackle the math set out by the diysubwoofer guy. You may like math more than you think you do! (Certainly more than me, because I have avoided that particular page until this post...)
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: fugit
Date Posted: July 30, 2004 at 9:17 AM
No, I really don't like it. I'm a perfectionist though, and if math will make it work better I'll use it. I only use it when I have to (electronics, shooting, explosives) otherwise it makes my brain hurt.  ------------- "I'm Rick James bi***, enjoy yo' self Ah Ah Ah"
Dave Chappelle as Rick James
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