# Ported box question



## spmpdr (Nov 5, 2009)

I just got my box back from the shop it looks great ,however i double there math to make sure and i cant figure out what the box is tuned to.Heres the specs:
2.75-2.80cu.ft slot port enclosure
port width:3.75"

port height:15"

port depth: 17" (the port goes into the box about9" then goes at right angles for another 8" 

What is this box tuned to? How did you figure it out ,I tried a slot port calculator but the math didnt seem right.Also the box is just a tad small for my subs (.2cuft) how will this affect sound and should I add pillow stuffing to the box?


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## 94VG30DE (Nov 28, 2007)

I have heard that you can play test tones, and around the tuning point there will be a lot of excursion, and then none at the tuning point, and then more excursion again below the tuning point (provided you don't have a subsonic filter there). Someone validate this method? It seems like it would work best with closely spaced test tones (63, 60, 57, ...)


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## spmpdr (Nov 5, 2009)

94VG30DE said:


> I have heard that you can play test tones, and around the tuning point there will be a lot of excursion, and then none at the tuning point, and then more excursion again below the tuning point (provided you don't have a subsonic filter there). Someone validate this method? It seems like it would work best with closely spaced test tones (63, 60, 57, ...)


Thanks for the info ,is there no way to figure out the frequency?


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## Volenti (Feb 17, 2010)

Is that 2.8cu.ft before or after the port displacement? I get around 48hz before and around 55hz after, I'd only add pillow stuffing if the box is too boomy for your taste (I predict much boom), since damping won't increase the apparent enclosure size worth a damn, but it will damp the boomyness considerably.


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## spmpdr (Nov 5, 2009)

That is after port displacement ,I think i will add the pillow stuffing to kill some of the boom effect.Thanks for the help ,how did you figure that out?Also the recommed tuning frquency for my subs(re audio sr 12's) is 33 hz .do to size limitations they were not able to achieve this.How will this affect the sound?


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## Volenti (Feb 17, 2010)

94VG30DE said:


> I have heard that you can play test tones, and around the tuning point there will be a lot of excursion, and then none at the tuning point, and then more excursion again below the tuning point (provided you don't have a subsonic filter there). Someone validate this method? It seems like it would work best with closely spaced test tones (63, 60, 57, ...)


This is correct, you can also hook up an ac current meter to the driver and it will have the least current draw at the tuning frequency, also lets you find the _actual_ in car tuning frequency.

[edit] sorry forgot to mention, was using bassbox pro 6 for the tuning calculations.


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## 94VG30DE (Nov 28, 2007)

Volenti said:


> This is correct, you can also hook up an ac current meter to the driver and it will have the least current draw at the tuning frequency, also lets you find the _actual_ in car tuning frequency.
> 
> [edit] sorry forgot to mention, was using bassbox pro 6 for the tuning calculations.


This is what I was getting at with the test-tone method vs the pen and paper method. You can "calculate" what the tuning frequency should be, but measuring it gives you a more accurate picture of where the Fb actually is, with all inconsistencies in the speaker/enclosure/design included. 

Actually an impedance sweep (effectively the same result as the AC meter sweep) would give the most accurate picture of tuning frequency, but not everyone has access to those. I think the Woofer Tester WT3 from Parts Express does this.


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## galacticmonkey (Apr 28, 2010)

Tuned to 45hz+ its not going to sound very good. Probably dont have bass worth a crap below 35hz.


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