Subwoofer Placement In Trunk

[valkyrie98]

i've got a few friends who do car audio for a living and they have in most cases fired the subs toward the rear of the vehicle so you would get a longer sound wave. but i see most here are firing the subs in to the back of the seat or through the skipass.
ive thought about taking a hole saw and putting some holes in the metal wall between the trunk and rear seat, then perforating the trunk liner that covers up the metal wall. has anyone done anything like this?

[Benny Z]

you can do that, but you will still get wave cancellation.

a lot of people "bounce" the subsonic waves off of the rear of the trunk by firing the sub towards the rear of the car. this does ok in cars with seats that divide the cabin from the trunk without a metal wall behind them...most japanese and american cars are this way. this also works well in hatchbacks.

but in our cars, firing through the ski pass is the best way to go.

thedogger has posted a link to the theory behind this several times in this forum. search for "e36 ski pass" in this forum and find the thread i started. thedogger posted the link pretty deep into that thread. i'll see if i can find it and will edit this post if i do.

*edit

[el.duderino]

It's worth noting that some amps (DLS for one) have adjustable 0-to-180 phase adjustment on the sub channel.

This allows you to minimize any cancellation effects at the listeners ear.

ANY sub box should be listened to at the driver's seat with polarity both ways to see if one sounds dramatically better.

We put a 12 in the corner of a 3-series coupe in a fiberglass enclosure onSaturday and it sounded great. Fold-down seats though.
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KX85

[exmaxima1]

thedogger has posted a link to the theory behind this several times in this forum. search for "e36 ski pass" in this forum and find the thread i started. thedogger posted the link pretty deep into that thread. i'll see if i can find it and will edit this post if i do.

The theory has a major flaw: the wavelengths depicted in the diagrams are way too short for the application. In a typical car installation the crossover point is below 80 hz. Even at 80 hz the wavelength is 14 feet (speed of sound divided by the frequency). For cancellation to occur, you look at the 1/2 wave, which would be 7 feet. At lower frequencies, the wavelengths are proportionately longer and unlikely to develop as shown in the pics.

It would take a HUGE trunk for bass cancellation to occur as depicted. I tend to agree with the dudemeister that a phase control might work wonders though.

Matthew

[valkyrie98]

something else ive noticed, on many subs you have a certain amount of undesirable noise just from cone movement. when you face the sub to the rear you wont be able to hear the cone noise. you may lose a little volume by facing it to the rear but if you have quality equipment you can simply turn up the gain a little or maybe go with a slight bass boost on your amp. i'm not a bass freak (i used to be. i once put 2 18" kickers in a crx. man that was nuts) but this is what i have done in my 325i using a single kicker cvr dvc10 and a phoenix gold amp.