[kaigoss69]

So I'm no expert when it comes to IB / free-air installs, I just know that they have the potential to sound fantastic. The concept is pretty simple: Use the trunk volume as the enclosure, and install the sub(s) in a baffle between the cabin and the trunk. The main advantages of IB are a) very linear frequency response, and b) efficiency.

The few BMW installs I have seen by members SCtud, mathematics and TMR all involved the installation of a separate baffle behind the back seat, with some degree of air space between the two. All of them had ski-passes. My idea is a bit simpler, and I was wondering if anyone with experience would care to comment on the concept.

Basically, I want to bypass having to install a separate baffle, and use the back seat as the main baffle. I would just have a mounting baffle, large enough to mount the sub to and to cover the ski-pass hole, and it would be screwed directly to the back of the seat. The waves from the front of the woofer would all be forced through the ski-pass hole, while the back waves would stay in the trunk. Now I know that the back seat and rear decks do not seal completely to the cabin, but I would think that it would be enough for this concept to work. So, before I go crazy building stuff, anyone with experience care to comment? Am I crazy or could this actually work?

[artiforgs]

Could work, but if you take an example of a random woofer..
Lets take the JL 12W7, witch is a BIG woofer. With a lot of air movement.

I may be wrong, but I remember it to require aprox. 60L of ported enclosure. (per element)

And if your trunk is aprox. 400L ? I think it will be too big space, using the trunk as the enclosure..Dont think you will get any air pressure, or SPL if you want..

[kaigoss69]

A lot of the subwoofers out there can actually work well in such an environment, including the W7. In my case, I would use a woofer that I know works well, specifically the Infinity Perfect 12 VQ.

[Mr Singh]

Rule of thumb is 10x the VAS of the speaker. Check out the IB3 series drivers from Fi Car Audio.

[Slow_335i]

My brother had a very similar setup in his Lexus is300. Worked great and looked awesome!

[Mr Singh]

Originally Posted by Slow_335i

My brother had a very similar setup in his Lexus is300. Worked great and looked awesome!

Looks like an Arsenal or Chaos 12

[Slow_335i]

Originally Posted by Mr Singh

Looks like an Arsenal or Chaos 12

Na it's a FI sub, not sure on the model.

[Mr Singh]

Originally Posted by Slow_335i

Na it's a FI sub, not sure on the model.

Its an early IB3. I'm the EU Distributor for Fi Car Audio

[Slow_335i]

Originally Posted by Mr Singh

Its an early IB3. I'm the EU Distributor for Fi Car Audio

Sorry I googled what you said earlier and a JVC sub and a BOSS sub popped up. lol

[makkan00]

Kaigoss this thread may give you some idea.
Not difficult and a lot easier than fitting a sub in rear deck IMO.
Plus you have skyhole (if I am not wrong).

[808MGuy]

If not completely sealed off you could get some cancellation. That's the reason most IB setups include a separate baffle behind the back seat. I assume since your thinking about mounting to the back of the seat that you don't have fold down rear seats. If that's the case, you could probably seal up the area that leak pretty easy. A simple smoke test to see where smoke leaks into the cabin would identify that.

[kaigoss69]

Originally Posted by 808MGuy

If not completely sealed off you could get some cancellation. That's the reason most IB setups include a separate baffle behind the back seat. I assume since your thinking about mounting to the back of the seat that you don't have fold down rear seats. If that's the case, you could probably seal up the area that leak pretty easy. A simple smoke test to see where smoke leaks into the cabin would identify that.

I don't smoke!

I think the back seat is sealed fairly well, but not sure about the rear deck. We'll see, cut the ski-hole today and mad the adapter and mounting plates. Installing tomorrow, using single 12" Infinity Perfect VQ woofer.

[makkan00]

Smashing.
Looked at specs of that sub and it looks promising.
Looking forward to see photos.

[kaigoss69]

Well I've had two of them sitting in my attic collecting dust. Figured I'd just throw it in and see what happens. Not expecting it to get too loud, but Andy Wehmeyer said it's a great sub for IB. Next step will be the addition the second one. I'll build a 90 degree wedge to mount them. This will be too obtrusive on my trunk space though I think so it's just an experiment at this point. Still planning on getting a single 15.

[kaigoss69]

Ok so I got my "experimental" set-up completed. I set the Infinity sub to "high Q" with a Qts of just over 0.7. Put in some hip-hop to see what she can do. All I can say right now - with limited listening - is that it gets crazy loud, and the bass is much cleaner with much improved volume and definition in the sub-bass range.

I do have more rattles now inside the cabin (from the increased SPL) so I will have to chase those down, and I will have to get the sub better integrated with the midbass, but that should not be too difficult to accomplish.

A big so far, and I can say that my plans for installing the other 12" have been cancelled!




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[e90TiAg335i]

Awsome work so far kaigoss. What do you think of it compared to my setup? Is it more linear and/or louder?

[kaigoss69]

Originally Posted by e90TiAg335i

Awsome work so far kaigoss. What do you think of it compared to my setup? Is it more linear and/or louder?

Hey man, thanks for the props. It's too early to tell. I think we may have to settle this in person!

[e90TiAg335i]

Haha, sounds good. I've done a little more work with the alignment on the front soundstage. Last weekend I ran into a new 335 owner and his dad at the dealership. Needless to say, they both wanted to know what they need to make theirs sound like mine!

[kaigoss69]

Originally Posted by e90TiAg335i

Haha, sounds good. I've done a little more work with the alignment on the front soundstage. Last weekend I ran into a new 335 owner and his dad at the dealership. Needless to say, they both wanted to know what they need to make theirs sound like mine!

Yep, you may have to patent "stereo corner-loading".

I still think one can come close to that type of output with the right 12 in a single corner enclosure. I had modeled your two Soundsplinters against a single Ascendant Audio Havoc 12, and the theoretical output was very similar, with 1000W input, vs. your 500W.

If my budget allows, I may still try that in the future, just because I'm curious!

Have you built any more fiberglass corner enclosures, with what equipment, and how did they sound???

[mob17]

Nice work Kaigoss! Glad to know you're satisfied.

I was also considering one 15" or 2 12" in a 90 degree triangular mount. But i think one 12 should be enough.

[kaigoss69]

Originally Posted by mob17

Nice work Kaigoss! Glad to know you're satisfied.

I was also considering one 15" or 2 12" in a 90 degree triangular mount. But i think one 12 should be enough.

Mo, don't hesitate to get the 15 vs a 12! It is always better to have the surface area, since the larger sub will have to move less to make the same output. Less excursion means more defined, cleaner bass with less distortion.

[mob17]

Originally Posted by kaigoss69

Mo, don't hesitate to get the 15 vs a 12! It is always better to have the surface area, since the larger sub will have to move less to make the same output. Less excursion means more defined, cleaner bass with less distortion.

Hmmm that does sound better. The thing is for my particular choice of sub, the IB3 15 is nearly double the size and one of the requirements for me would be to be able to quickly release the sub when in need of boot space. The 15 wouldn't make that impossible, just a bit more of a headache! Also the VAS is 183L, compared to 83L for the 12. I think Mr Singh says normally 10 x the VAS is what you are looking for in terms of boot space so the 12 is already a bit high. However the qts is nearer to 0.7, which is what you or Makkan were saying works better.

If the VAS was lower I would probably get the 15 and deal with the headache of removing it when required.