Sorry if this has been done before, but is there any significant difference in SQ in the positioning of the sub box in the boot ?

In my last car (VN) I had the box (sealed)mounted up on the diff hump with the speaker facing into the boot. If I hadn't blocked off access to the hatch in the back seat with my seat covers I probably would have faced the sub into the car. So either way, does it make any noticable difference facing forwards or backwards ? And if its a big boot (such as mine) is there any gain in mounting it up hard against the back of the back of the boot - firing into alot of open space before hitting the back seats ? I've only ever used sealed boxes - I guess when you start looking at porting its a different story...
I remember one of the habibs at SCR told me once the best spot to mount them is in the corner of the boot - ie where the spare wheel usually is. Obviously this is only going to be possible with small boxes.

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Gadget man and electronics geek
THE HYENA RECORDS COMMODORE

TEAM SHIRE

Nothing is foolproof to a sufficiently talented fool.

in my sedan (about the same size as yours roughly) i've found that i prefer the subs forward firing with the box all the way forward in the boot (entering the cabin via the open armrest port). i tried rear firing and it was sloppier for me - forward is tighter, cleaner and fast.

the only problem is that i get alot of cancellation (from the rear waves bouncing off the boot lid and cancelling out the front waves - evidenced by SPL increasing with the boot lid open). to get around this i'll have to air seal the front of the box to the boot so that rear waves cant bounce back to the front. hello expanding foam

so yeah for a sedan i find forward firing / forward positioned sounds the cleanest but you miss out on SPL unless you seal the baffle to the boot, or, have fold down seats that virtually let the box become part of the cabin (like a hatchback).

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Custom SQ System

Source: Clarion DRX-9675z - Front Stage: Boston Acoustics Pro 6.5's - Centre Channel: Boston Acoustics FS50 Midrange - Ambient Satellites: Boston Acoustics 3/4" Kortec Tweeters - Processors: Audiocontrol EQT's - Subwoofers: Earthquake BR12's - Amplifiers: Kicker IX404's - Power: Stinger 1 Farad HPM Capacitor
Sounding sweet and taking it to the street

[Edited 1 time by T-Bro on 22 August 2002 at 16:56]

In my accord i will be firing them backwards, as when i tested it there was no loss of SQ (at least that was audbible to me) but there was far more bass actually in the cabin. It was still nice and tight and fast.

In the corners is probably best for SQ, i had mine in the corner until i took it out. SQ was excellent but wanted more output.

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TEAM /////ALPINE
"The probability of someone watching you is proportional to the stupidity of your action."

In my case, it made a fair bit of difference where the box was located. Right at the back was best for me.
It didn't matter a whole lot which way the sub was facing, but I have a pretty dodgy box with the port at the side. That could be the reason.
With the sub facing backwards, I got better sound by reversing polarity of the sub. That is one of the built-in functions of the HU, so I can judge the difference very easily, while sitting up front.


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Car: 1994 Commodore SS
HU: Pioneer DEH-P7450MP
fronts: Pioneer TS-C1625 splits
Rear: stock 6" dual cones powered off HU
Sub: Pioneer 10" in 35L ported box
Amps: 2x Jaycar 2x84
TEAM <insert team>

for the best SQ, you will want to mount your sub in a rear corner of the car. the reason for this is that there will be no "pockets of air" behind it and there will be none (or significantly less reverberation (ie when your boot shakes to the s**thouse).

as for front or reverse mount... whatever. if you mount your speaker backwards, then you give the box more air. (then it's just whether your sub sounds better in the greater air volume or the less...) so try it.

B1n0ry correctly noted that when you turn the sub around he had to change the polarity (or phase). this is because the speaker was firing in the opposite direction as it used to be.

this is most notable if you have to identical subs side-by-side and they are out of phase with each other (ie one has its negative and positives reversed). you will notice a distinct Loss of Bass, [I wish i could draw pictures in this text thing....]

but picture this in your mind: a perfect sine wave. now if you introduce another perfect sine wave which is exactly opposite to the first one, this cancels both waves (leaving you with a straight line). which is crap.
if both of the sine waves were going the same way then you get "double" the output. (it doesn't work out 100% this way, but you get the idea).

so B1n0ry's reverse phasing his sub, meant that he probably had some duplicated frequencies that were being played up front and by the sub (and looking at his speakers 6", and 10"s and guessing there is no high-pass filter on the fronts) meant that the front speakers and the sub were cancelling some frequencies out- instead of enhancing them. B1n0ry you did well to notice this.

mounting your sub in a rear corner will blow you away. your car will stop rattling, and become a lot clearer. the only catch is: you may want to get that box fibreglassed by a professional - it's worth it, trust me. (and they will build it so it looks like it belongs there without intruding, and won't break any of your existing panels).

the box will cost $300-500. but will be the best thing you've ever done.

i've done a number of different mountings ranging from parcel shelf, thru behind seats, to mid-boot and cornering. believe me, cornering wins hands down; every time.

regards


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pioneer headunit
Focal utopia 165w3
Phoenix Gold 15" sub
2x Alpine 1507
piii800 w/90gb vcd/mp3/dvd

quote:

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Originally posted by ellifant:
so B1n0ry's reverse phasing his sub, meant that he probably had some duplicated frequencies that were being played up front and by the sub (and looking at his speakers 6", and 10"s and guessing there is no high-pass filter on the fronts) meant that the front speakers and the sub were cancelling some frequencies out- instead of enhancing them. B1n0ry you did well to notice this.

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Well, I am using the high-pass which is built into the HU, at 80Hz (12dB/oct). But, with the sub on the wrong phase, the cancellation is much more noticable when the HP is turned off (obviously).

It's all part of the testing process we do to get the most out of our system.

Even though at the last P6 meet the demo of my sub was rather ordinary (those who heard it), a surprising amount of bass does go straight through into the cabin, provided the boot is closed and the ski-port open. (For a 10" naturally.)


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Car: 1994 Commodore SS
HU: Pioneer DEH-P7450MP
fronts: Pioneer TS-C1625 splits
Rear: stock 6" dual cones powered off HU
Sub: Pioneer 10" in 35L ported box
Amps: 2x Jaycar 2x84
TEAM <insert team>