Subwoofer suggestions, please

ms318is · #1 (**permalink**) 11-28-2001, 10:38 AM

Good day, all!
I am going to install a sub in my '95 318is with folding rear seats, and would appreciate your suggestions on where to install for best sound and minimal space loss. BTW, I have done many installs and have no problems building very geometrically complex boxes. Thought I would get suggestions to avoid having to try several boxes!

I have a 12" and (2) 8" subs on the shelf from previous installs. I'm leaning towards using the 12" in a sealed box, about 1.2 ft3 per Stillwater's recomendations. The amp I have available is a good, solid 200 watt RMS unit so power is not an issue. My desire is accurate and clean bass at moderate levels only. No competition, no booming.
My challenge: My wife likes to use the rear of the trunk a lot, so I do not want a box across the back. Need to be able to fold at least one seat for long objects. Also need to retain spare. The ideal from a space criteria is to build a box to conform to the rear of the right rear seat and wheel well, but I am concerned about how that will sound. Anybody done this? If so, which way did you aim the driver? Second choice: Conforming to right rear corner under CD changer.
Thanks for any suggestions!

s--k · #2 (**permalink**) 11-28-2001, 12:13 PM

Use the 8s and build an enclosure on each side of the trunk (1 sub
on the pass. side fires into the trunk the other sub on the driver's
side fires into the trunk). You'll retain 90% of your trunk
space this way.

ms318is · #3 (**permalink**) 11-28-2001, 05:40 PM

Thanks! That is also a possibility with the benefit of being able to remove one if a little more trunk space is desired.

Any experiences on which way to aim the drivers in the E36? In my old car (240SX hatchback) it worked out best aiming into the corners. But that is with an expanding wedge interior...
For max space in E36, aiming straight at each other would be preferred.
Or maybe firing straight down with legs underneath (slot loading)?
Any one try either?

s--k · #4 (**permalink**) 11-28-2001, 07:33 PM

What I mentioned before and slot loading
sound really good!! Also do you need to keep
your rear fill or can you move you reafill
somewhere else?

ms318is · #5 (**permalink**) 11-29-2001, 09:27 AM

Did a little shopping last night, and the Polk Audio dx8 shows promise - only .33 ft3 enclosure! Maybe I'll buy new drivers...

I've always liked having some (very) subtle rear fill, and was planning to just leave the stock drivers. I am assuming your question was leading towards a free air in the package tray or stealth boxes?
I'm thinking free air won't be too good with the seat folded down

and have heard mixed reviews on stealth boxes. What is your opinion? If I was to move rear fills, where would they go to?

s--k · #6 (**permalink**) 11-29-2001, 11:38 AM

What I thinking for my setup was to move the rear fill on top of the
deck with some custom carpet or whatever. This will leave the rear
fill holes open which would vent more bass into my car. I also
wouldn't have to cut my rear deck. A really trick install would be
to install the rear fill on the side panels flush with the rear
seats.

JB TECHNOVIOLET · #7 (**permalink**) 11-29-2001, 03:27 PM

Although lower frequency's can be heard from a longer distance, i dont think this is the wisest move here. I wouldn't put them that far back in the trunk. I dont think you are going to be happy with the tightness of the bass. If you have a ski hole you are set, jus put your twelve there with a sealed box, and point it at the ski hole. If no ski hole, I would suggest putting the 2 8" in the back deck. Some minor cutting will be required, but you'll definitely tell the difference. Either way, let us know what happens.

Later,

Josh

Joe · #8 (**permalink**) 11-29-2001, 05:15 PM

I have 3 8" JL Audio W6's in a sealed enclosure that faces the REAR of the car. This is the best way to face the subs to get maximum sound from them. The best sound from a sub is about 6-8 feet away, and the only way to get your listening position to this point is to face the subs towards the rear of your car, that way the air can travel to the back of your car (a couple feet) and then back towards the interior of your car (a few more feet still). This puts you in the appropriate listening position.

BTW, I would question if a 200 watt RMS amp is enough power for 12" subs. I have a 600 watt RMS Precision Power a600.2 powering my trio of 8"-inch subs.

ms318is · #9 (**permalink**) 11-30-2001, 08:49 AM

I'd love to have a 600 watt amp for the subs, but my available $$$ is leading me to re-use my old equipment.
I've also found a true 200 watts RMS with a robust power supply is plenty for me. I am not into booming or hurting my ears anymore. I also lean towards acoustic suspension enclosures, which seem to work well with smaller amps (air suspension helps the driver stay in control).
I even did an install with a robust 50 watt amp driving a 12" (what she had available at the time) in a VW cabriolet and it sounded fantastic up to about 120 dB. Plenty for normal listening. She never bothered to upgrade the amp.
Remember, dB output is logarithmic to power input. To double the SPL (6dB), you need about 10x the power. So with a small amp, you only lose about 6 to 12 dB... but do have to be careful not to destroy the driver with distortion.

BTW, anyone have any 8's laying around, looking for a good home?

JB TECHNOVIOLET · #10 (**permalink**) 11-30-2001, 10:19 AM

hmmm..... ms318is, I might have two 8" for sale. But you'll have to give me a couple days to think about it. I have eight 8" Kicker Free Air that are brand new, I have already drawn out and designed a nice box to fit all eight, but in reality I dont need them, I would probably be fine with 4, but i'll have to think about it. I have a couple friends that want them, but of course they want me to give them to them. I'm not down for that

Anyway, email me if you're interested.

Later,

Josh

s--k · #11 (**permalink**) 11-30-2001, 10:36 AM

Small technical correction:

A theoretical 6db increase requires a 4-fold increase of power.
A doulbling of power theoretically increase 3 db.

JOEYP · #12 (**permalink**) 11-30-2001, 11:47 AM

2 JL audio stealth Boxe, 8 ic woofers....you cous run themo at a 2.3 ohm load, or a 1.3 if u us W6 subs.....the sound very nice..high recomendation!!!

ms318is · #13 (**permalink**) 11-30-2001, 01:50 PM

hey S--K. 4X power for 6dB? You know, that seems more in line with my personal experience, but not what I had read before... Hey, an opportunity to learn more! Thanks for the input! And I appreciate your respectful way of communicating. Nice forum!

s--k · #14 (**permalink**) 11-30-2001, 02:58 PM

Hey Ms,

Yep, it makes sense because 3 db requires doubling of power.
Double the power again (a 4 times increase now) and you get
the theoretical 6 db gain.

2 things:

1) It makes you realize how hard it is to gain DBs after a certain
point. You EXPONENTIALLY double power yet get a LINEAR SPL increase!

2) As you said before you only really need 200+ watts for a satisfactory output levels, see below:

Power DB Gained
1 watt 3 db
2 watt 6 db
4 watt 9 db
8 watt 12 db
16 watt 15 db
32 watt 18 db
64 watt 21 db
128 watt 24 db
256 watt 27 db

Now say you had 1 12" with an in car sensitivity of 100 Dbs. You can
figure out that with 256 watts of power you'd be at 127 db in car.

s--k · #15 (**permalink**) 11-30-2001, 03:04 PM

Forgot to add that it's a theoretical increase because you should be
getting a 3 db increase from doubling power IF no other components
are operating near their limits. If your sub is operating at 99% of
it's available excursion, power handling, etc.. then you won't see
a 3 db increase.

Some other factors include power compression, sound wave absorption
and cancellation in the car, your car's transfer function and too many
other variables to list!