Someone please help me with my box!


Bronze Member
Username: Erikdagenerik

Livermore, CA US

Post Number: 44
Registered: Aug-05
To make a long story short, I am stuck with this 12" port enclosure for my IDMax. I know in the future I will get a better box, but as of now I am just trying to make the best of out what I have. In this link lies the dimensions of my box:

I had a 10" enclosure version of this box and I had the same problem, the tuning is way too high. I know this wasn't the best solution, but I took a piece of wood and inserted it against the inside wall of the box to shorten up the port's width. I want to do the same with this box. In the outline, you'll see a dotted line box against the inside left wall. That is where I wish to stick the board to decrease the port width. The question is, how thick does the board need to be?

I don't know anything about box calculations, and I was wondering if anyone can make that calculation on how thick the board needs to be to tune the box to 35 hz or below.

I appreciate any help and once again, I know this box is a bad design, and Im just trying to make the best of it right now.

The subwoofer is a 12" IDMax 12D2. Specs are here:
Nominal Impedance (IMP) 1 / 4 ohms
DC Resistance (Re) .95 / 3.8 ohms
Resonant Frequency (Fs) 20.3Hz
Electrical "Q" (Qes) .424
Mechanical "Q" (Qms) 2.02
Total "Q" (Qts) .35
Equivalent Volume (Vas) 5.71 ft3
One Way Linear (Xmax) 24.6 mm
Cone Area (Sd) 545 cm2
Sensitivity (Spl) 88.5 dB
RMS Power Handling (Pwr) 200 to 1000
Speaker Displacement .12 ft3

Thanks for your help guys!

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 5769
Registered: May-04

"I don't know anything about box calculations"

Respectfully, then why are you trying to design a box?

Do some reading to find out where you've gone wrong or go to a shop which can either sell you the correct enclosure or fix the one you have. You are way off base with what you're trying to do.


Gold Member
Unregistered guest

Considering you are a Gold Member, why dont you help him design that box?

Silver Member
Username: Mixneffect

Orangevale, Ca. USA

Post Number: 385
Registered: Apr-05

Here are your graphs:

I configured your enclosure to go with a 3" round port instead of a rectangle port. This will be in effect for both designs/graphs. So, you will have to cover that port and install a 3" PVC type instead of it.

Your EXISTING enclosure is 1.58cf, but with driver displacement it is only 1.375cf.


Vb: 1.58cf (box volume)
Fb: 26.96 Hz (tuning Frequency)
Ql: 6.932
F3: 36.24 Hz (cutoff frequency @ 3 dB below)
Dv: 3" (port diameter)
Lv: 17.61" (port length)


The OPTIMUM ported enclosure volume for that driver is as follows:


Vb: 3.02cf (box volume)
Fb: 21.93 Hz (tuning frequency)
Ql: 6.932
F3: 27.02 Hz (cutoff frequency @ 3dB below)
Dv: 3" (port diameter)
Lv: 11.18" (port length)


I hope this helps.

Silver Member
Username: Mixneffect

Orangevale, Ca. USA

Post Number: 389
Registered: Apr-05
In other words;

Your box is okay. It would have a cutoff at 36 Hz.

You just have to cover your port and remove the port divider (if you can), because when you cover the existing port end, that little corner may act as a separate chamber and resonate at a different frequency. It may not be that big of a deal, but I am just letting you know. It may not even be an audible difference.

One more thing;

Do not use poly-fill! Poly-fill doesnt necessarily improve sound or extension in ported enclosures, as it does for sealed. Use 1/2"-3/4" carpet padding, and adhear it to the inner walls using some spray glue.

Make sure you install a 3" PVC port 11.18" long in another area.

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 5842
Registered: May-04

Gold member - I don't help because I don't have BassPro loaded as a program. I'm sure Erik appreciated your input however.
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