16 sub spl box

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Ravendarat

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Posted: July 11, 2007 at 2:59 PM / IP Logged

Ok so here is the deal. I am building an SPL only vehicle out of a 91 Aerostar Van. I have 16 Infinity 1250 12" subs and 4 Exile 1200.1 amps. I am not concerned with powering the system as I have a HO alt on the way and 6 brand new batteries for the back. What I am concerned with is the box design. Obviously sealed is easiest, but what do I want to do to get best results. Keep in mind that reality is a factor. I cant just do a wall thats individually chambered and port each sub, that wont fit as it needs too much surface area. Ill give you a link to the tech stats on the subs and throw me any ideas you have. My total RMS power output of these amps after being strapped will be approx 5800RMS between all drivers.

http://manuals.harman.com/INF/CAR/Boxes%20and%20Parameters/1250W.pdf

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

stevdart

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Posted: July 11, 2007 at 7:47 PM / IP Logged

4 drivers in parallel for a 1 ohm load onto each amp?

How much airspace in cubic feet do you have for net? Do you have 56 cu ft? 40 cu ft?

With these subs it looks like you will need very large port opening per set of four subs, like 148 square inches...but a very short port length, like 5". Can you design this so that you can allow four openings for ports that big?

Can you build this as four enclosures stacked? Four drivers per enclosure, each with its own amp. One port per enclosure. Large port opening but doesn't take up much volume.

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

forbidden

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Posted: July 11, 2007 at 8:10 PM / IP Logged

Build your boxes as pairs, 2 subs sharing one airspace, slot or aeroported. Ensure that all the boxes can then be bolted together internally as well.

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Ravendarat

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Location: Canada

Posted: July 11, 2007 at 11:11 PM / IP Logged

You guys are kinda on the same line as me. I figured on doing boxes in pairs. And ya Im gonna parallel 4 subs to each amp into a one ohm load, screw the damping factor. So rob you figure sharing air space in pairs will be fine? If I do that then porting wont be an issue but if I have to chamber individually then Im still screwed I think. As for total air space in the van I havent taken full measurements yet as the van wont be in my hands for another two days, but being that I plan on doing a wall and removing all seats except for the front two and the amps and batteries can all go verticle in the back I dont think over all air space will be my limiting factor

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

Ravendarat

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Location: Canada

Posted: July 13, 2007 at 4:41 PM / IP Logged

OK so I am kinda old in that all the boxes I ever build that are ported are round ports. If Im gonna do this ported I need to do slots. Can I use one side of my box as one wall for my port or do I need space between the port wall and the box wall? Also last question for ya, if I do them in pairs like Rob suggested and just do shared air space for each pair, will my port just double in size or is there a formula for that as well? Thanks guys. I get the van on Monday and start construction sometime next week so Im trying to work out all the specifics ahead of time.

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

DYohn

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Posted: July 13, 2007 at 5:26 PM / IP Logged

Yes, the outer enclosure wall can be one wall of a slot port and no, you calculate the port for the enclosure net volume, not for the number of subs it contains. More drivers means a larger port opening will be required to prevent port noise, but for an SPL system this is not of much concern.

Model those woofers in a ported (bass reflex) enclosure and play with size and port opening until you discover their max SPL configuration, or determine the resonance frequency of the van and tune the enclosures to activate it..

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Ravendarat

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Posted: July 13, 2007 at 6:03 PM / IP Logged

thanks, I dont know what the hell I was thinking with the "double the port for double the subs". Of course it makes sense to just do a strait up calculation for port size.

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

DYohn

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Posted: July 14, 2007 at 12:57 PM / IP Logged

And whatever you do, watch out for that double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, because as you know, it's a killer. 16 sub spl box -- posted image.

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Ravendarat

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Posted: July 14, 2007 at 9:56 PM / IP Logged

DYohn wrote:

And whatever you do, watch out for that double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, because as you know, it's a killer. 16 sub spl box -- posted image.

Still my favorite line I have ever read on any message board

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

Ravendarat

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Joined: February 23, 2004

Location: Canada

Posted: July 15, 2007 at 10:59 PM / IP Logged

Ok, now Im confused. I was doing my box design today and the slot port is giving me an issue. I figure that my port can be no bigger than 24x3 and the sweet spot in the vehicle seems to be in the area of 55-58 hz. When I do the math on it my port length comes up as negative. Any help on this would be appreciated.

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

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16 sub spl box

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