would this be dangerous??

[dark_sounds]

ok u got the ski hatch... thats out...

what if i was to cut away two large squares either side of the ski hatch, does this effect the car at all? i hope this doesnt effect the strength of the car too much...

alturnativly, what if i cut away ski hatch hieght across the whole back seat so instead of 3 squares cut out,,, just one really big one....

cheers

if ur wondering why, its because of my car audio project to take place in the near future, eliminate the metal blockers and u should get slightly more bass into the cabin... and i will need access to the 2 extra batteries in the boot! which will be hidden in the slope behind the rear seats...

[dips346]

you can cut most of it away as long as you weld in a frame as strength cos if you did have a rear smack,the rear will give wat quicker

[dark_sounds]

i dont need most of it away,,, just enough to get my hands on the batteries and wiring if i need to adjust something, though mind you might be worth getting rid of the pillers so they dont resonate.

dips pm.

[Globulator]

eliminate the metal blockers and u should get slightly more bass into the cabin

If you can get the front of a
12" driver into the cabin, facing toward you, the efficiency of the bass
will be so high that you should not need that big an amp.
JBL supply several cabinet/baffle design plans with their drivers for
raising efficiency still further .

I reckon a single 12" where the ski-port is would be a good way to go,
you'll never run out of bass and you can hide it completely by flipping
up the central arm rest. (Assuming the back seat is how I imagine it).
You do not need to cut any of the bulkhead, the port area is enough.

Just be careful sealing the driver to the baffle. As far as efficiency goes,
you'll lose 1/2 the sound anyway as the speaker has a back and a front.

This calculation is based on an infinite baffle sealed box design, ported
boxes can give more bass but it is less well defined:

A bass box in the boot firing at the boot lid will lose I guess 50% of the
half left through the boot lid (bad for convertibles!) - so you get
15% left of your original total ...
(100 - 50)/2 = 50/2 = 25%
....to bounce around and go out of the bottom, back and both sides of
the boot, the remaining 5th side being the back seat which now gets
5% of the energy you started with, to start making its way through
the back seat and bulkheads. If you lose only 1/3rd you'll end up with
3.3% of your power in the car.

By facing your driver into the car therefore you are already:
50%/3.3% = 15
times the sound power ahead. This is why I don't think you need to
worry about power - 250W rms into 4ohms will blow your windows
out - and matches the JBL power handling.
It will be as loud (to you, in the car) as a 3750Watt bass box in the
boot.

[rickk]

I wouldn't mess with it...
The construction behind the back seat is specifically engineered to give the chassis stiffness there. That's exactly why you don't see many BMWs with folding rear seats. In the cars with the optional folding rearseats, the construction is specially strenghthened in another way.

So cutting it out wouldn't be great for handling or crashing.

If you DO decide to do it, I'd consider a rear strut brace of some sorts.

[Brianmoooore]

Rear seat back panel is a very important structural member of the E30 bodyshell.

[kam-325i]

I have removed only the ski hatgh panel and it did make a difference to the sound in the cabin. I would not remove any more than that...

[Cotty]

Personally I wouldnt do more than remove the ski hatch.

I punched mine out in my 316 when I had a 12" sub in the boot and it was more than enough for the sounds to come through. In fact even at low volumes the rear view mirror was unusable as it used to vibrate so much.

Still want a couple of 10's in an isobaric box in the touring . But needs to be removable

[dark_sounds]

cheers for the input guys,

was actually mainly hopeing to have access to the batteries.

the subs i like my system to have alot of bass, when needed.

from a SQ point of view, then fair enough, though i will intend on getting a 4.5-5cuft box ported to 30-35hz, and running a new RE XXX 06 .... sure there is alot of mainstream products which do a fair amount of bass, i used to run two type Rs in my system though this is nothing compared to my 3rd system i ran in my mk2 golf. anyway point is im going for streetbass or SQL, will mostly be SQ orientated with the extra kick of bass,, when needed. thats what the bass control unit is for!

but yeah batterys will be there, its un avoidable as far as my plans are concerned, im not running big power to get bass into the cabin,, running big power because i want silly bass,, at the turn of the knob.

cheers for the input anyway guys, certainly something worth considering.

though howabout a welded steel beam across the top?? corner...?? should prove enough support??

[delphini]

OK so for those of us with cabrio what are some suggestiions for a boot speaker box setup??? Is there a possibility that one might open a circular bass port that may enable sound to enter the cabin such as a port in a bass box??? In essence turning the whole boot compartment into a large box???
I'M, sure there must be a way NOT to cut the whole rear bulkhead. Iknow a fellow that had his rear bulkhead butchered before he got the auto (it was a cabrio as well) and he said that the previous owner replaced the sheetmetal removed with plywood.

[Globulator]

OK so for those of us with cabrio what are some suggestiions for a boot speaker box setup???

My setup with photos is here:
http://www.e30zone.co.uk/modules.php?na ... ic&t=33602
and details of Mr Lees too.

If you've got a big field and want to run your own rave - but don't fancy hiring all that PA gear then you might prefer something like Bootyman's setup - very much worth a look:
http://www.e30zone.co.uk/modules.php?na ... ic&t=32723

I haven't cut any metal in my setup, I use the two pre-existing holes where the speaker is mounted and fire the bass through there. The wooden baffle the speaker is mounted on is screwed to the metal with chipboard screws - use a vernier to get the screw shaft dia and drill to that, 2.5mm I think for mine. It holds very tight. I had to route out a circular channel in the wood baffle 6mm deep to give the subs roll surround room to move - or it would rattle as it hit the wood (or metal if you bolted it straight to the metal). The holes in the wood then line up with the original metal holes and you seal the gap with foam rubber.

It sounds very good but you will lose a little upper bass as you cannot 'see' the speaker directly - it's got to go through the seat metal and then the seat. You might want to fill the rear delta (trangle between the boot and seat bulkheads) with some light poly foam from a hi-fi diy store or a cheap pillow, except where the speaker is.

I'm not sure the effect of drilling extra holes in the bulkhead on the sound or the strength exactly - one or two small holes might be useful for the sound. I've proved that you certainly do not need the full 10" cutout, it works well through the two small holes there already.

The first big advantage of a bulkhead mounted cab. sub is that you can still hear the bass with the top down. With my old box in the boot the bass disappeared with the roof and motion.

The second big advantage is being able to use the boot, so you can take the cab. touring, long journeys, camping, shopping etc...