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Discussion Starter #1
Currently I'm running a pair of Hertz HX250d's in IB behind my backseats. I will be getting rid of these so I need a new sub stage. I'm currently seriously considering the JBL w15gti mkii. My friend, who I helped with his 13w7 IB, use to have a JBL w12gti in a ported box and at that time we put it in my car and it sounded absolutely amazing.

Due to the very large box size for porting the JBL w15gti (4.5 cu ft. +), I want to save trunk space so if I had this sub it would be in IB. It should be amazing; however, I have been modeling it on WinISD and it shows if I port the sub in a very large box, it will remain flat until about 30 Hz and peaks in the low 20s.

I am considering building it as it would be in IB, but since I already use infinite baffle, my deck and everything in the trunk is sealed so...... What would happen if I added a slot port to that baffle?

Would this make my trunk a ported enclosure?

The sub remains flat to 30Hz in a 11-16 cu ft box tuned to 21 Hz. I believe my trunk is 15.5 cu ft total so once the baffle is made it will take up some air space but it will still be within that required airspace. Even if I did put a few things in my trunk, it should not affect the sound at 30 and above.

I picked 30Hz because I can set my subsonic to either 30Hz, 20Hz, or off.

This is all without taking cabin gain into consideration. The gain in spl at 30Hz of going ported as opposed to IB would be about 5 db.





What do you guys think? Is this worth a try or just stick to straight infinite baffle?
 

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Just make it so you can close the port. I wanted to do this in my IB setup but can't figure out how without rebuilding it all, as the 15s take up nearly the entire baffle leaving little for ports. The issue is a trunk is not a box, it flexes and leaks. It really should perform like larger than it is since it is so loose, compared to a model of a real box. So you might not get the port energy you would from a tight/solid box. In my model even half the port output I would be happy as hell, I'd get flat to 20 while now it drops off at 25hz. But I've not been able to work on it and since it works great to be honest, I should work on the doors first anyway.

So will it work....I dunno. I did figure on lining the port with foam or felt and making it an 'L' to keep more trunk noise out of the cabin, but my car is not exactly quiet to start with.

I have two pyle 15s into the seat, the output is awesome for <100 total IMHO. They look similar to older free air subs, the specs were similar to AE IB15s though I'm sure they don't have the xmax and quality. But for my use they don't get much xmax and SQ is pretty good. I'd like to tell you do it, lol, but I just don't know. I figured I could just cut a hole but after I worked hard to get the install done in time I had...now I see it will not be that easy, but will still try it if I ever get some free time. But I can only fit a slot or maybe around two 4" tubes.
 

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Discussion Starter #3
Thanks. That does make sense. I did think about fiberglassing every side of the trunk to make it solid but then there would still be the trunk lid and all that work, time, and money would probably not be worth it. I guess it would sound good and be a cool project to try but I'm thinking now that the sub in IB will be plenty, maybe too much. I could always try porting it later if I could afford all of that fabrication.l
 

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These pyles are amazing IMHO, sure they are not AEs but I don't need to blow the glass out of the car either. They can overcome 4x125 on highs with a 500rms on them. So no I'm not that worried about porting it, but to get more 20Hz I sure would.

Another issue I suspect but can't find anything on really, is I have built some large ported boxes in the past. They don't seem to work like small ones. The pressure in the box is not near as high, however they do work. The subs don't stop moving when the port comes on and they don't xmax when unloaded. I suspect much of this is because the large box has the sub somewhat unloaded all the time, unlike a typical small ported everyone makes now. I was running 2cf on a 10, it was a IB tuned 10 so I had to.

Another issue is I don't care so much about the SQ if I wang on it, because that is far past my SQ range. SQ while shaking the roof just don't make no sense to me lol. Some people insist on it. I can play this fairly loud and be under .25" on the subs no problem, so when I hammer it they are very bloated in the car its way too much bottom. Sure thats good sometimes lol but messes my ears up after a bit anyway. So I don't know if the port is going to work exactly like a box, if it might depend on output levels? I don't know but I'm trying to get the FR flatter and considering the above, my reasons might be different than someone else's for trying this.

Yeah I can get 25Hz pretty good, nothing to sneeze at in my book so not complaining at all. It does 20 but since I feel it a lot and not really hear it, makes it hard to determine what level output it has by ear. 30-35 is strongest but FR is fairly flat by ear.


I don't think it would be worth making the trunk a box, you can get a lot out of IB if you work at it some. It would be easy to drop quad 15s in one or two manifolds IB, and output would have to be insane for SQ use. Even a pair of AE are something and they are not 'hammer time' subs they are SQ subs that take relatively low power. Remember that technically the looser and leakier the trunk is, the better it is for IB. Long as you don't have a giant rattle trap back there.
 
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