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Discussion Starter #1
I'm running infinite baffle with a pair of IB15s. The Qtc comes out to right around .7 in my 15' trunk. I don't know why but I like the sound of the lower Q setups and venting my trunk to atmosphere makes this setup sound so much nicer. It was very nice to begin with but I feel like it sounds more natural when the trunk is vented. Right now I removed the factory trunk vents and put a screen over them. It helped. Pulling the weather stripping off the trunk helped even more. This is obviously only for experimenting, the weather stripping has to go back on. So I was thinking about cutting a larger hole than needed to the outside world and using AP mat in the hole to "tune" it to my liking. Is there any reason not to do this?
 

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Sorry for going slightly O-T...but,
Have you noticed any increase of road noise, since removing your vents?
 

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Discussion Starter #3
None. I noticed that even with the trunk open and the bass fairly low, the vents were opening and closing with the bass.
 

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Discussion Starter #6
I really don't think it will make much of a difference at all.
It made a nice difference so far by creating leaks. I want something more controllable. At some point its too much since it doesn't sound the best with the trunk open. I have no idea what size to start with or if there's any math involved that can help. With the pair of 15s it does make a difference. With the single 12w6 not so much. Maybe its the vas?
 

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I wouldn't do it either.

The goal of AP aside from lowering the impedance curve is to make a much smaller enclosure appear as a larger one. And that only really works with low Q drivers. The Q of your drivers is too high to do AP.
 

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Discussion Starter #8
In a way its still making the enclosure act like a larger one assuming the cabin is larger than the trunk. There's a definite change in sound with the leaks I've created. John even talks about stuff in the trunk raising Q and why he lowered the qts of the auto version of these subs. There's no reason a larger trunk couldn't lower the Q to at least the Qts of the subs freeair or until the cabin takes over.
 

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DO IT! I love the sound of an Aperiodic sub system, but never seem to remember to buy a car with a damn trunk. Either way, it's nearly free to try and maybe you can prove some of these know-it-alls wrong. I have seen some unlikely subs work wonders AP, such as the old mid-90's CV Strokers.
 

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Go to a large open area (so reflections off garage walls, etc won't affect the results) like a parking lot and play with the trunk lid open and with the lid closed and see if there's a big difference and go from there.
 

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Discussion Starter #11
Go to a large open area (so reflections off garage walls, etc won't affect the results) like a parking lot and play with the trunk lid open and with the lid closed and see if there's a big difference and go from there.
That's what I've done. Trunk cracked is a change for the better. Trunk fully open, not so good but not terrible. Factory vents removed and weatherstripping removed, very nice bass, more natural sounding. I'm looking for a better way of controlling it besides removing weatherstripping. I was thinking about cutting a hole to house the mat and trying different thicknesses.

I'm guessing I need to use a hole that's larger than the leaks I've already created.
 

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If I was doing this, I'd cut holes in the back of the spare tire well the size of the round metal vent covers. The covers will keep water out, and you can slowly add until it's better. If you cut one too many, it's a lot less to cover back over. Here's the covers I'm talking about:

Round Aluminum Louvers
 

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the 'rule of thumb' for ap is to have the opening half the diameter (or area) of the driver(s) used. That's have to be a pretty decent sized opening to get appreciable results.

What about changing the wiring config on your drivers to change the Q? I'd give that a shot before cutting metal.
 

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When you open the trunk or open it a little bit or cut a big vent, you're just tuning the trunk--the opening is a port. The Fb or Ft (resonance frequency of the ported trunk) is very difficult to calculate by knowing the volume of the trunk and the size of the opening because the trunk is really lossy as an enclosure and it's difficult to calculate the length of the vent.

Save yourself a bunch of trouble and save your car from a bunch of cutting and measure the frequency response of the system with the trunk closed. Then measure it with the trunk open. Then, EQ the sound of the car with the trunk closed to match the curve when the trunk is open. There...done.
 
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