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View Full Version : How to reverse engineer this prefab box tuning?



Blazin_Jason
11-01-2005, 10:10 PM
Hey not sure if this is possible, but thought I would ask. I have a prefab box that I bought with 2 Type R's over a year ago used from a buddy. I was too lazy to ever build something custom so I just used it. After reading on here quite a bit, came to realize that I probably wasn't getting the sound I should be. The subs are old 1240's and I don't know what the specs are on them (other than single 4 ohm coil). My question is how can I determine what the box was tuned at? Maybe some of the box calculating programs will allow it to be reverse engineered. I figured out the box to be about 3.3cu ft and it has 4 3" diameter x 10" long aeroports. Anyway to find what frequency its at? It sounded pretty crappy. Thanks

Jason

Moe Lester
11-01-2005, 10:14 PM
I need the box's external dimensions and wood thickness. I want to make sure the airspace figure is accurate. you gave the port info that is needed so we dont need that. Subwoofer displacement will help

ruckus
11-01-2005, 10:24 PM
I need the box's external dimensions and wood thickness. I want to make sure the airspace figure is accurate. you gave the port info that is needed so we dont need that. Subwoofer displacement will help
for exact you will need this stuff but if you are acurate on size youre looking at low 40s tuning it looks like

Blazin_Jason
11-01-2005, 10:36 PM
Box dimensions are: 32" wide, 15" high, and its 18" at the bottom and angles up to 13" at the top. Hope that makes sense. Subwoofer displacement I don't know as I can't seem to find it anywhere online. Older Type R's 1240 all I know. Thanks

Jason

Edit: Forgot its 3/4 MDF

InhumanAcura
11-01-2005, 10:41 PM
how far are the back of the ports from the rear of the box right now with that angle?

Blazin_Jason
11-01-2005, 11:08 PM
http://members.shaw.ca/jason.loos/box1.jpg
http://members.shaw.ca/jason.loos/box2.jpg

ruckus
11-01-2005, 11:19 PM
thats 3.3359375 cu.ft which puts you at somewhere around 43hz tuning if i calculated correct (guessing at displacement)

Blazin_Jason
11-01-2005, 11:56 PM
Cool, thanks. That gives me a way better idea as to where its at compared to before. Thanks again.

Jason

Decado
11-02-2005, 12:03 AM
I think what inhuman acura was asking how far are the rear of the ports from the inside wall of the box that they face, which would mean how far are the ports from the bottom in your case. Do they have 4 inches from end of port to the bottom of the box? And it looks like the subs would be too close to the port openings, not exactly sure on that though, moe lester or someone else will know if they chime in here again.

Moe Lester
11-02-2005, 12:06 AM
i get around 46ish hz

dbhittin
11-02-2005, 12:16 AM
x6(45x8-8y)+5-6

dbhittin
11-02-2005, 12:17 AM
i got 43.356234

Blazin_Jason
11-02-2005, 12:18 AM
Either way this box won't be used anymore. Going to try a 2.5 cu ft sealed, seperate chambers so 1.25 each. Maybe later I will play and do something different.