E36 Sedan Sub Position Advice

russelljb · #1 (**permalink**) 03-03-2009, 03:07 AM

Hi fellow DTMers.

I own a 320i sedan in Australia and have been upgrading the audio.

Tonight I installed the wiring for a sub and amp and have just been playing around with where I might position my sub.

I errrrrrrr, gave myself the ski port option and the box that my sub is in fits perfectly up against the back of the rear seat with the sub facing towards the cabin through the ski port. This is the best position for me in terms of using up space in the boot. It is perfect really.

What I want to know is will this lower my potential bass as I was told it is better to face the sub towards the rear of the car, however I have seen many setups where the sub is facing through the ski port.

Advice?

Thanks,
Russ.

Duke131 · #2 (**permalink**) 03-05-2009, 03:49 PM

I'm also curious about this. Anyone?

russelljb · #3 (**permalink**) 03-08-2009, 06:31 PM

Hmmm these forums seem a little stagnant!

I am pretty happy with having the sub pointing in to the cabin through the ski-port. The box I currently have the sub in is way below the recommended volume (recommended 1.25 cubic foot and the box is only 0.7) and the angle for the back seat isn't right so there is a fair bit of gap between the opening and the actually speaker. I am soon to be getting a new box that is 1.2 cubic foot and sits against the seat.

Sounds great though!

Crispy222 · #4 (**permalink**) 03-12-2009, 11:42 PM

point the sub towards the rear and listen to the reflected sounds. It will help fill in the lower tones IMO and experience. After positioning the box facing front or rear, play with swapping the the pos (+) and neg (-) terminals. You are trying to match the wave's phase with the interior speakers.

People face it thru the hole for looks only.

Scotty89 · #5 (**permalink**) 03-22-2009, 02:31 AM

Facing the subwoofer + ports to the back of the trunk will give more bass loading - I never intended to do it myself either but after I comparing forward/backward mounting, I haven't looked back since.

Definately sounds beefier, though if you haven't insulated/padded the trunk and panels, it will cause alot more audible vibrations.

Baxy · #6 (**permalink**) 04-23-2009, 05:50 AM

hey mate just givin u my 2 cents worth, ive got my sub(15inch) located in the wheel well. just had to do a few little mods to make the box fit, but it slipped in there nicelyand sounds a treat, only bad thing is that you cant run a spare in the boot......
just a pic for ideas, its not award winning but its alright. Slammed BMW 320i Bagged on 20's.... - goulburn, AU

rf90 · #7 (**permalink**) 04-28-2009, 05:45 AM

in my opinion to get the best bass in the cabin is to have it facing through the ski port!

the further back it is the less you will hear in the cabin and the more distortion you will get from boot rattle etc, i fixed this with some sound deadening but it's still not 100%. im running 2x12 800rms each

Maz · #8 (**permalink**) 04-30-2009, 07:02 PM

At the back of the boot firing into the boot lid is definitely loudest.

Then allowing the bass to flow into the cabin.

This is called "rear loading"

edge747 · #9 (**permalink**) 05-10-2009, 09:06 PM

Face it in toward the cabin as the BMW trunk is tight as a vault. What sub/amp did you get?

E30stain · #10 (**permalink**) 08-08-2009, 10:29 PM

i did this in my old e36 323i. get a flat plywood board (15mm is indestructable) and mount the sub in it so that it faces the cabin. have the rear of the sub exposed in the boot. screw the board into the metal around the ski hole, depending on the size of the sub you might need a couple of bits of wood as spacers so it clears the ski hole edges, wont need too much. stuff some rubberised foam into the gaps to make it air tight.

That creates what i think is the clearest bass with the armrest down. can be done neater, i had some grey carpet laying around so i covered the back of the board and had the amp screwed on the back too. my 12" sub needed some sort of spacing but not much. i found using the whole boot as an enclosed box was really good especially with the bmw sound proofing under the seat and good condition boot seals. plus mounting it like i had it left almost as much boot space as what i started with. I think this only works on the sedans as the seats dont fold down.

makes for a great massage seat too!

Undrstm8ed · #11 (**permalink**) 08-14-2009, 10:44 AM

All in all just to add my $ .02 Bass frequency's themselves are recorded mono left and mono right simply because its most of what you hear below 120 cycles (hz) is NON-directional. Which is WHY you can hear it coming down the street from any direction. the higher the frequency the more omni directional and directional the sound becomes.

What your hearing between front and back loading is reflection and time dealy...

Scotty89 · #12 (**permalink**) 08-20-2009, 04:36 AM

The part you mention about directional sound from a subwoofer is true, yes. This is also because the lower frequencies have a longer wavelength, and can penetrate through objects better.

That is why you can often hear the bass/rumbling outside of clubs or home theatre rooms. Because the bass has much better ability to penetrate with lower frequencies than say a tweeter.

This does not mean that rear/bass loading from firing it backwards into the trunk, is false.

Just go out to your car, and turn your sub around. Listen for yourself. It IS noticeably heavier when firing backwards into the boot.

Many just refuse have it firing backwards because they seem to think that their subs will be seen more by people sitting in the car, or look more impressive. If you want people to see what is producing all this mad bass, go and open the trunk. How hard is it?

Also @ E30stain, I believe what you are trying to describe is an infinite baffle setup. This means that the sub will use the entire sealed boot as its enclosure.
For a 12" subwoofer, the capacity of the trunk is far far too great for the optimal performance of any typical 12" subwoofer driver. Even for a ported 12" enclosure, the entire boot is far too big.

Yes, it will give bass, and yes it will sound better than having the sub flopping around free-air, but it isn't really a way to achieve the most out of your sub.

Edit: and as for time reflection/time delay - yes the reflection is helping create the bass loading... and as for time delay, well, don't bother getting anything bigger than an 8" driver if you think that time delay is going to mess up your sound quality.

Subs need heavy cones with lots of power to move considerably more air than woofers or tweeters - because they are heavier and cannot "accelerate" or oscillate as quick, the heavier cones therefore are a lot less articulate/accurate in reproducing sound than the woofers are. That is why a 15" is not as tight/punchy as a 10" driver.

The sound delay from the sound waves traveling from the sub, to the boot lid and then back in to the cabin is negligible. Most of the time, the sound delay between the sub's sound in relation to the other speakers is caused by using a larger driver (say 15" or 18") without sufficient power to drive it, and in an oversize enclosure. That is when you will hear sound delay and booming/muddy bass.