Best placement of port inside enclosure.

Here is a diagram of my subwoofer enclosure from a top view.. Before I start, I would like to say this is the biggest box I can construct, 1" bigger on the outside of any diameter, and the box will not fit. This box will be powering two T110D4's, using a T20001bd amplifier. This box as you can tell, is dual chamber and tuned to 33-34hz, with the subs mounted on the top surface of the enclosure pointing up, and the ports are facing towards a hole I have in the middle of my back seat originally made for skii's to be put through (1992 E36 325i bmw). 

My biggest question is, is the ports opening on the insidie of the enclosure, too close to the driver?  I would guess the distance between the opening (found on the inside of the enclosure) is like 3 inches away from the driver itself..  Would it make any difference if I were to move the subwoofer towards the left away from the opening of the driver?

2nd question would be regarding the divider in the middle of the enclosure.  Without this divider, would this enclosure still be seperated into two chambers?  In a sense, without the divider, each chamber would still have one port opening to each of their area of space (cu. ft. NET).   And if infact, this divider is needed to seperate the chambers into two (which I prefer to have two seperate chambers for SQ + safety of drivers if one blows out), should I beef it up from 0.50" to 1.25" or something maybe?

The distance is ok. We would prefer to have just a little bit more space between the port and the sub (at least an extra 2 inches) But this setup may not affect the SQ. For best results, we recommend getting those subs as close to the port as possible. This will give you better imaging on the SQ and waveform timing.

You can thicken the divider if you like, but it isn't 100% neccessary (although it wouldn't hurt). If you installed the subs properly, then their counterpressures on the divider along with the port softening the pressure will keep it ok, but you can't overdo the stiffness. Losing the divider completely changes the dynamics of the enclosure and will create a huge difference in sound. We don't recommend it. It'll create large planes on your box that could flex. The divider will act as a brace.

bellsracer wrote:

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The distance is ok. We would prefer to have just a little bit more space between the port and the sub (at least an extra 2 inches) But this setup may not affect the SQ. For best results, we recommend getting those subs as close to the port as possible. This will give you better imaging on the SQ and waveform timing.

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Thanks for your responses guys!   Regarding the port length, I calculated the port length using WinISD, so I dont think it'd be coming out wrong dimensions for it.. I got all the t/s parameters correct, put 1.5 cu. ft. per driver plus inputed the 33hz tune, and by looking at the air velocity it looks just right.  If I made the port wider I would actually have to make it longer if I did that, I dont quiete understand the physics behind that completely but it's like that everywhere I have read regarding ports..

As for the quote I specified above, would you be able to rephrase that for me a little bellsracer?  I got a bit confused in that paragraph, I read it as you were telling me to increase the distance between the port and the subwoofer but then read it as you were telling me to put them as close as possible for best SQ waveform timing.  What would be a good safe minimum distance between the port + driver?  Thanks for taking the time to reply, and I hope to hear your reply soon as i'm dying to finish the blue prints for the enclosure. 

>.<   Sorry about that. We meant to get the subs as close as possible to the port on the outside of the box. In other words, slide the subs to the left on your diagram. It won't affect the dynamics of the box itself, but it will help the imaging of the subs as the sound goes through your vehicle. If they are placed there so you can see the subs when the trunk lid is open, then it's ok. If you can, slide them to the left at least a couple inches.

Second, the hole in the BMW. Double check how big it is. It's area should be at least 80% of the area of the subs cones plus surface ports on the box. (subs cone surfaces + 44 * 80%) The trunk might act as a second box and the hole will act like a port and may change the sound from the trunk to the cabin.

Last, consider mounting an angled brace (about 8" wide on 5/8" or 3/4" MDF) under the subs that reflects the sound waves to the "left" side of your box in the diagram. draw a tic-tac-toe diagram (3x3) that divides the board into 9 parts. Drill 3" circles into it where the lines intersect. This will keep the air flowing properly in the box. The high point of the brace should go no higher than halfway to 2/3 of the height from the back of the sub to the bottom of the box. This won't affect your port dynamics but will help control the vibration and sound waves so they do not reflect back to the cone of the subs. (This can cause as much as 3% THD on the subs, depending on install)

Good Luck!