Subwoofer setup in a 2-door

[Major]

So I'm busy trying to figure out how best to get a subwoofer setup in my car. I've come up with a couple of ideas, some of which are from this forum.

4x 8-inch subs in the trunk
Problem with this is apparently bass still sounds as though its 'trapped' in the trunk, seeing as E30 trunks are pretty much sealed from the cabin.

Subs in the trunk, with openings in the rear deck
I've got 6x9" co-axials installed on my rear deck right now, and I was thinking, what if I remove the 6x9"s, put two big rubber grommets where they used to be, so that sound from the trunk can get through? Might look a bit uggo though.

Knock out the ski hole and 6x9"s
And put subs in the trunk.

Mount a sub directly to the ski hole
My feelings on this are that there would be issues with the sound seeing as the subs are firing straight into the cabin towards the windshield? I don't know...

Put a 8" sub mounted on the rear deck ala IB
How does this sound?

2 8" subs mounted in the rear door panels
And 2 in the trunk?

Or any combination of these.
I want loud bass, but nothing that sounds like crap. SQL, if you will. What do you guys think?

[passdanachos]

Knock out the ski hole and mount a pair of sub facing thru the seats and you will be just fine.

[Skoobeesnak]

Better solution

Or better yet get one of Luke's ass kickin custom sub mounts in this group buy. I have very happy with mine.

Subwoofer box group buy thread here:

http://www.r3vlimited.com/board/showthread.php?t=100820

[StereoInstaller1]

Since I don't think I can ship cost-effectively to SA, how about you fly me down there for a week?

No, seriously, I am going to be posting plans for this box, one of these days. If you have a decent table saw you can build one.

Luke

[joshuaaa]

hey luke, when you get around to posting up those plans.. hit me a pm with it so i can check it out maybe work something to fit my car..

thanks, josh

[Major]

Heh, that would be great Luke. I'll make a plan to build it myself, haven't tried one yet.
Was reading through the 12-volt site, and what about this?



I know that all the springs and stuff for the boot are all under the rear deck, but I'm thinking of just using some shocks on the trunklid instead, and get rid of all the junk under the deck.

Also, why only mount an 8" on the rear deck? Mine, for example, is just over 13" wide?
What sound issues are there with firing a sub straight into the rear window?

Thanks.

[passdanachos]

Also, why only mount an 8" on the rear deck? Mine, for example, is just over 13" wide?
What sound issues are there with firing a sub straight into the rear window?

Thanks.[/quote]


You can mount a pair of 8's in the rear deck but that is a lot of metal surgury. Also removing the torsion bars and replacing them with shocks is a lot harder than it sounds. I have seen them done before and it looks like crap. Having a subwoofer setup like what Luke is offering is a much easier approach and equally effective. Firing thru foam and fabric will not affect the bass significantly as you may think.

I originally had a sub box in my car, where there was a single 12" facing the ski hole and the vents were ported thru the rear speaker covers on the rear deck. It was fine and it had tons of bass.

[StereoInstaller1]

Guys, the reason I prefer to use 4 8" woofers if I do an Infinite Baffle is many sided.

First, in using woofers as a group, efficiency goes up...in regards to a group of 4, you can expect as much as 12db greater sensitivity. IB installs are incredibly inefficient...so the whole "loud" thing goes out the freaking window, because IB installs cannot handle much power. Crappy deal all the way around, basically.

Next, in terms of frequency response, you have to understand the basics of putting a woofer in a box. No matter what kind of box of what kind of speaker, you will raise the resonant frequency of the woofer. So, lets say you have a woofer with a Fs of 26Hz. Put it in a box of 1.5 cubic feet...typically, you will raise that Fs to about 45Hz, maybe 40Hz, but whatever, you will raise it substantially.

In an IB install, you basically do not raise the Fs of the woofer. So, now, you have that woofer flopping around at the Fs, making uncontrolled bass at WAY too low a frequency, far below the ideal range. Plus, since the woofer is uncontrollably flopping around, the amp has totally lost control of the cone, making more issues with achieving nice clean bass.

Another factor is transient response...8's play plenty low in an IB install, so why not go for the faster woofer? So, bigger motor area, smaller cone area, better woofer control, higher efficiency in addition to cleaner, tighter bass to me make 4 8" woofers in an IB setup the clear winner.

Don't get me wrong...all through the 80's, I did TONS of IB work, especially in BMW and MBZ...plus some god-forsaken Jaguars, too. I did 4 12" Pioneer IB woofers in a '72 Caprice with 1200 watts running them, I also did TONS of E34 installs using a woofer I spec'd out from Eminence...any way you cut it, I likely did it, including my own copy of Linear Powers dual 8" slot port IB setup using 8 10" JL IB10/4 in a 1981 Camaro...

All in all, the best bass compromise I have ever found is a single 12 in a large vented box. Happy happy sound and some trunk space left over, plus easy on the alternator and wallet.

Luke

[passdanachos]

And to add to Luke's response, the E30 is not so sealed from the cabin to the trunk as one may think. Think of this, everytime you shut either the passenger or driver 's door, the air pressure created is vented into the trunk and released thru the little black flaps on the rear sides of the car (one is where the battery is) That means there is air flowing from the cabin to the trunk. In the newer BMW cars, the windows actually open a crack automatically when you open the door and closes after you close the door.
Also for IB to work effectively you need to isolate the cabin completely from the trunk by means of fibreglass and Dynamat. In my car, to control the Fs, I use a Aperodic Membranes which essentially dampens my Subwoofer cones from going out of control.

I also completely sealed the trunk from my cabin. How do I know? When I shut my drivers door, the sunroof "pops" open for a split second! And it's a bitch to shut the trunk!


I didn't build my car for loud bass, but for sound quality and if that is what you are going for, then consider IB, but for efficiency, and loudness, go for vented box.

[Major]

I'm going to have to follow Luke's advice here. Having one 12" in a vented box sounds great, and would probably require far less surgery on my part. I'm looking for sound that has (for lack of a better word) a lot of 'wallop'. Something that smacks you in the chest.

You have this 12" setup in your car, don't you Luke? How is it set up?

Thanks for reminding about the vents that lead into the trunk nachos, forgot about those.

[passdanachos]

If you are looking for some "wallop" then you better move to a pair of 10's or better yet 12's in a vented box. Most subs now are suited for vented enclosures of less than a cubic foot ea. So a two cubic foot box will fit nicely without taking up much trunk space and you save the rear lid torsion bars. Again, fire them thru the ski hole, maybe pop a couple of hole thru the rear seat metal with a 3" hole saw, and you are golden. Vent the ports thru the rear speaker grills. You don't need rear speakers. I always pull them out or turn them off when I build my competition cars. You will get enough rear stage from the front speakers.