Trunk Space? IB Setup

[Threehz]

What's going on guys! So hopefully in the next week and a half I'll be driving my first E30 home. I'm a big 12volt DIYer and a bit of an audiophile. Anyhow..

I tried searching everywhere but could not find this information.. What are the measurements of the inside of the trunk on a E30. (Preferably a 91 318is heh) but I'm sure they are pretty close and I just want to get a rough idea down now. So if anyone has the inner measurement of the trunk, or the exact or relative volume that would be awesome!

So I really like the trunk of the E30, big, boxy, roomy! I would hate to sacrifice all that space. I've got two 15's in my SUV which I'm about to sell but there is no need for both in the bimmer, the thing would rattle to pieces... One should be perfect. So I'm going to do an IB setup in the trunk. Install the woofer in a single board of MDF cut to fit snugly in the trunk woofer facing front of car. This will in theory use the entire rest of the trunk as the enclosure and leave hopefully about 90% of the trunk still usable.

Anyone ever done this? I saw some people do some very shallow but wide boxes in the trunk to try and save space but I want the whole trunk left.

[StereoInstaller1]

To get decent performance out of an IB setup you need a woofer intended for the job.

Specifically, you want an Fs in the range of 28Hz, a Qts over .6 and a HUGE Vas, like 300+ liters. You also want a fairly low MMs, on your 15" you would want to see under 200 grams, but that ain't gonna happen.

I have done at least 40 E30s in IB, but all WAAAAAAAAY back in the day when these cars were new. Very few woofers (even those that claim to) work properly in an IB install these days, but back in the 80's, there were quite a few woofers out there that did.

I even had Eminence make woofers for me, they were a custom 8" that I ran in groups of 4. They sounded incredible, but I know of nothing like them on the market.

Either way, what the hell, its half a sheet of MDF, right? Might as well do it, see how it works for you.

Good luck!

Luke

[Threehz]

Surprisingly I think my subs might work perfectly for this application, they are a bit unusual. Here are their specs:
fs: 30hz
qts: .75
vas: 170 L
MMs: 185.5 g

Yeah I got two sheets that should be much bigger then the trunk's height and width left over from my last box I made.. I have a feeling it's going to pleasantly surprise me. These woofers are odd ones and continue to please me in every application I've used em in.

With an IB setup in the trunk like this, since it's such a small space technically it would act as just a large box correct? I was thinking about doing porting as these woofers love porting.

[StereoInstaller1]

See what you can find about "aperodic membranes" if SQ is your main goal.

[Threehz]

Wow really cool idea, never heard of it till now. As much as I want great SQ I'm not going to be putting a lot of money, or barely any into this. It's just instead of throwing my massive box from my SUV into the little E30 I thought that the trunk would make a perfect IB setup and I happen to have two big mdf boards left. Someday I'll build a perfect setup.

However I will likely invest a little in some sound deadening and sealing. Sound deadening the trunk in an IB setup would help by reducing the back waves right?

[StereoInstaller1]

there is so much energy coming off the back of that woofer, there just is no way to do much of anything besides actual dissipation...but I think the only bas rattle is gonna be the vents under the bumper and maybe a bit of rear deck rattle.

[Threehz]

Maybe I'll just stuff my entire trunk with polyfil! Maybe not...

Alright sounds like a plan, I'll definitely let you know how it works out.

Just as a quick question, these cars have two door speakers and two rear deck speakers which are all 5.25", are there any others?

[StereoInstaller1]

Stock tweeter location on the window, but that is it.

If you get a late model you can do a 6.5" in the doors as long as it is n't too big

[UNHCLL]

I had a friend in high school who had a 15" sub in the trunk of his E30. It sounded horrible, made lots of noise, but it was junk noise. Didn't matter how it was setup, be it IB or in a box. Ported, un-ported, different facing directions, etc. He tried it all.

You're best bet is to spend the less than $200 and buy one of StereoInstallers 10" boxes. Solid proof that size isn't the end-all-be-all of audio in an E30.

[StereoInstaller1]

Yeah, I love that 10" box...plays low, plays loud, terrific detail, fairly light, does not require much power to get adequate SPL, (I only have 140 watts RMS on mine) fits perfect, uses very little actual trunk space, you can add the amp rack and make it gorgeous...IMO, the perfect blend...but I just might be biased in my opinions....

[CabrioPunk]

Just buy Luke's Box.

[StereoInstaller1]

You guys did notice I am specifically NOT trying to sell him a box, right? I love to see others interested in audio try stuff for themselves, I think its awesome.

Ultimately I know my 10" box will do better, but (good lord I sound conceited) honestly, in the 31 years I have been a pro installer, I have never seen or heard anything that even comes close to as good a "compromise balance" as that damn 10" box. I still cannot believe you guys have bought over 200 of them just from this one forum, it just blows my mind.

[CabrioPunk]

I said it so you wouldn't need to. Your stuff speaks for itself it seems. That's the way it should be. Too much shit service and products anymore.

[StereoInstaller1]

Thanks! That is the goal, right?

[Threehz]

@UNHCLL I think your friend must have just had a bad woofer :/

I have definitely heard amazing things about your Luke-box. I don't doubt it's ability. I don't know if any of you are familiar with Toby Speakers, down in Texas this guy Toby has spent many years and perfected a series of boxes that I can say are unlike any others. They are some of the best sounding box/speaker combinations I've ever heard.

SPL is not an issue for me, I just want my music to have a balanced yet powered system pushing it. Right now my amp pushes both my 15's wired to 4ohms and I have to keep the gain pretty low or else the bass is overwhelming. In the bimmer that amp will only power one of those 15's and be wired down to 2ohms which will be an incredible change in power. I believe that extra power will not only let the sub perform a lot better but I think it will be perfect for an IB setup.

When it is done I'll sample it and let you guys know how it turns out and how I do everything (sealing, spacing, etc)

BTW I would love to buy one of your boxes and see how they are Luke, but even if I did have the money to, I'm a 12volt addict and there's nothing more fun then building audio systems and custom boxes/setups etc. I'm sure you understand me.