[Nelson@BimmerTech]

Can you post a picture of your rear seats? Do they have armrest?

[kaigoss69]

Originally Posted by e90bmw328i

Darn it BMW for soundproofing our trunks to this extent. Thats pretty much what kaigoss' thread summarizes too. So your generalization isnt off.
If I can find a back seat rest with ski hole, I should switch mine out .

Do you have fold down seats or fixed?

[e90bmw328i]

Originally Posted by kaigoss69

Do you have fold down seats or fixed?

I do have an center armrest but the seat itself is fixed (not folding seats). From the trunk if I look at my rear seatback, there is just no opening into the cabin. Its completely flat panel.

[Nelson@BimmerTech]

Here's what i did on my E60. I also have fixed seats.

1st system:

Sealed box






2nd System, Infinite Battle








I'm a huge fan of IB. 1 would do 1 15" http://aespeakers.com/shop/sbp/sbp15/

Here's a review

http://www.diymobileaudio.com/forum/...-4-review.html

[Wongway]

Yeah, I can't deny the math and physics behind it all there. Infinite Baffle setup like that > all in our cars.

Simply put, you can do what they did, and cut.

[kaigoss69]

The SBP 15 did a great job in that application for me. Reason I went with the IDMax in the end is that the AE ran out of steam at higher volume levels. It is also a very neutral sounding sub, you will barely know it is there. For me I would have needed two of the SBPs to make me reasonably happy. However, the IDMax sounds better IMO and I am completely happy with one.

[kaigoss69]

I made a diy to cut the ski hole into the fixed rear seat, but unfortunately the pics are gone. Pretty easy though to do.

[Nelson@BimmerTech]

Originally Posted by kaigoss69

The SBP 15 did a great job in that application for me. Reason I went with the IDMax in the end is that the AE ran out of steam at higher volume levels. It is also a very neutral sounding sub, you will barely know it is there. For me I would have needed two of the SBPs to make me reasonably happy. However, the IDMax sounds better IMO and I am completely happy with one.

I totally forgot about the IDmax, GREAT sub!!!!

[skrelnik]

Originally Posted by e90bmw328i

I do have an center armrest but the seat itself is fixed (not folding seats). From the trunk if I look at my rear seatback, there is just no opening into the cabin. Its completely flat panel.

Turn the rear deck speakers into two 10 or 12 inch subs, or go with Nelsons' recommendation of cutting the ski pass.

[e90bmw328i]

Originally Posted by kaigoss69

I made a diy to cut the ski hole into the fixed rear seat, but unfortunately the pics are gone. Pretty easy though to do.

Is there any metal thing in the seat or is it made of wood?

[e90bmw328i]

Originally Posted by skrelnik

Turn the rear deck speakers into two 10 or 12 inch subs, or go with Nelsons' recommendation of cutting the ski pass.

Thats interesting. Is there enough space to mount a 10" in the rear deck?

[e90bmw328i]

Took some pics of the upper layer inside the trunk. Unless you cut holes into this (thereby compromising the integrity of the structure) there is no way to mount the woofers as rear deck.

Although i did notice a wide fairly rectangular opening which could allow lot of sound to penetrate the cabin.

[e90bmw328i]

More pics

[e90bmw328i]

Look what we have here

[kaigoss69]

Originally Posted by e90bmw328i

Took some pics of the upper layer inside the trunk. Unless you cut holes into this (thereby compromising the integrity of the structure) there is no way to mount the woofers as rear deck.

Although i did notice a wide fairly rectangular opening which could allow lot of sound to penetrate the cabin.

Mounting a sub to the rear deck is the most unobtrusive method of adding a sub to the trunk. I think Don at Unexpected Creations (6spdcoupe) in NJ has done a couple. From what I have seen, they use 10" low profile subs that are designed to add a good amount of bass to the bottom line, but a couple of those will probably not get as loud as a single 15" through the ski-pass. I'm sure it sounds great, but it is expensive. Most cost-effective way is to use the ski-pass.

[e90bmw328i]

Originally Posted by kaigoss69

Mounting a sub to the rear deck is the most unobtrusive method of adding a sub to the trunk. I think Don at Unexpected Creations (6spdcoupe) in NJ has done a couple. From what I have seen, they use 10" low profile subs that are designed to add a good amount of bass to the bottom line, but a couple of those will probably not get as loud as a single 15" through the ski-pass. I'm sure it sounds great, but it is expensive. Most cost-effective way is to use the ski-pass.

So they cut a hole in the rear deck area?

[kaigoss69]

Originally Posted by e90bmw328i

So they cut a hole in the rear deck area?

Not clear, they were very secretive about it. They may just fire through that large opening and remove some of the insulation to allow the sound waves to get through. From what I saw, it's a very expensive install, probably many fold more expensive than the ski-pass (which you can do yourself).

[Nelson@BimmerTech]

Originally Posted by kaigoss69

Mounting a sub to the rear deck is the most unobtrusive method of adding a sub to the trunk. I think Don at Unexpected Creations (6spdcoupe) in NJ has done a couple. From what I have seen, they use 10" low profile subs that are designed to add a good amount of bass to the bottom line, but a couple of those will probably not get as loud as a single 15" through the ski-pass. I'm sure it sounds great, but it is expensive. Most cost-effective way is to use the ski-pass.

He has done for than a couple more like 10...

That's what he did in his E55 and it sounds PHENOMENAL.

[Wongway]

Yes, I haven't had that done in my BMW, but I had a similar setup in one of my old cars. Most unobtrusive setup, but when custom done that way, I'm going to guess it's very expensive for the return in the E90.

Speculating here, but I would guess you'd have to remove the rear deck and cut into the sheet metal to have enough mounting depth.

Don from Unexpected Creations (6spdcoupe) would best be able to answer your questions there.

[Nelson@BimmerTech]

Originally Posted by kaigoss69

Not clear, they were very secretive about it. They may just fire through that large opening and remove some of the insulation to allow the sound waves to get through. From what I saw, it's a very expensive install, probably many fold more expensive than the ski-pass (which you can do yourself).

We've done a couple. I wouldn't say its crazy expensive. Is not for the faint-hearted..

[e90bmw328i]

Originally Posted by Nelson@BimmerTech

We've done a couple. I wouldn't say its crazy expensive. Is not for the faint-hearted..

Cutting through sheet metal is not something I would ever want to do given the safety implications and potential pain to sell the car in the future.

I think I will take Kaigoss's suggestion and cut a ski hole assuming there is no metal plate. If would be great if you can repost the pictures in your DIY . Some of the pics refreshed from google's cache but very soon they will disappear too.

Other option is to find a seat with ski hole.

[6spdcoupe]

IB is not terribly difficult but it is time consuming and can eat up some costs quickly. We use 9 ply Birch- minimum 2" thickness total for a single sub. Fitment is critical and needs to have some contours done- properly. Density is key as well as sealing off the cabin as best as possible. That said, we have had great success with both ski pass and rear deck.