IW STi Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
2,773 Posts
Discussion Starter #1
STI DROP IN FILTER

While doing the design work on my trunk setup, I've run into a question.....how does the direction that the sub is pointing in the trunk affect it's performance and nature.

From past experience, I'm under the impression that a sub pointed toward the rear of the trunk will give a louder, deeper "bassier" sound while pointed right at the back of the seat will be a quieter, tighter, almost muffled sounding response. Pointing up or to the side...not much experience but I would guess it would be somewhere in between.

Anyone have experience specifically with the acoustics of the WRX's trunk? I'm leaning towards a sideways facing sealed box with bandpass style enclosure around it or an upward facing sealed box with a similar configuration.

Any input? I'd love to hear what you guys with free floating boxes have found.
 

·
So Gangster It Hurts
Joined
·
3,521 Posts
This setup sounds pretty good. Not quite as good as pointing it back from the front of the trunk, but not muffled in any way, either. :p

 

·
Premium Member
Joined
·
2,802 Posts
I think the enclosure(ported or sealed) has more to do with the sound of the bass than the way it is pointing. Not sure though. Mine sounds good and loud to me. I really have nothing to compare it to though.
 

Attachments

·
Registered
Joined
·
858 Posts
each enclosure is diff.

if your enclosure isnt bolted down, just test it. around 120 hz and below, the sound should be non directional, so set your crossovers correctly...

that's why you use the biggest driver you can up front, so the sub CANNOT drag the image towards the rear or where the it is.

if you set the cross over high, say 180-250hz, see how you can start to see the image being dragged back there. then start setting the it to 150, then 120, the finally 90 or 60 and watch how the image image improves.

now if you have a tiny speakers up front, that takes more work...

hell if i can stuff a subwoofer up front, i would... ;)
 

·
Registered
Joined
·
84 Posts
Outside temperature gauge REALLY goes below 0F

It's not really an enclosure issue. The difference in performance is due to cancellation of the sound/pressure wave.

When the box is pointed toward the rear of the trunk less cancellation occurs.
 

·
Registered
Joined
·
2,773 Posts
Discussion Starter #7
If anyone has a box that is free floating in the trunk, just try it out. Pick a track, set the volume and move it around. I have done this with my past 2 cars and I noticed a significant difference in the behavior of the sound waves. This is all similar to the effects you can hear when placing a non-floor-firing sub along a wall or out in the open.

Thanks for the comments regarding the imaging effects of subwoofer frequencies.....but why the big difference between having the sub faced right up against the back of the seat vs. the waves heading back into the trunk to bounce around?? If the sound waves are immediately absorbed into the seat, you don't get the volume and 'booming' of a sub that points into a cavity that allows sound waves to move around.

I'm curious what the theory involved here is. Anyone have any good references about low frequency sound waves and travel?
 

·
Registered
Joined
·
5,261 Posts
I know exactly what you mean clone... in the Supra i tried the subs with the rear seat folded down (and the subs point towards my seat probably 6"-1' from my head... then tried it with the rear seat up, facing the hatchback and it sounded a LOT btter IMO. Its like you cant even hear the frequencies when its pointed toward you :(?

Robert~
 

·
Registered
Joined
·
2,773 Posts
Discussion Starter #9
I've just always been curious what the theory is of sound waves. Yes, at a certain frequency, you don't hear the sound, you feel it. But, until that point I'd assume subs act just like another speaker....they emit sound waves and where they are pointed, how they are reflected/absorbed and how they arrive at your ear matter.

Still looking for technical discussions like this....no luck just yet.
 

·
So Gangster It Hurts
Joined
·
3,521 Posts
Sound waves, just like water if you'll notice, bounce off some surfaces and are more or less absorbed into others. In the case of a trunk or hatch, even many low-frequency waves will be reflected back off the rear wall of the trunk and into the passenger cabin. Since most cars do not have a lot of metal between the trunk and cabin, most waves will pass right through the rear seat (up or down) and will also be transmitted via the metal chassis surrounding the car. Reflecting the waves off the rear of the car and allowing them a longer distance to travel before hitting your ear means the more frequencies can be better-reproduced before you hear them. The lower the frequency, the longer the wavelength. The more distance you give your sub to produce that wave (reflected or not) will help in the quality and sometimes magnitude of said soundwaves.

That's a gross oversimplification of a very technical idea. . . . but I hope it helps. :p
 

·
Registered
Joined
·
949 Posts
i read a post somewhere on sounddomain where a fairly extensive test was done regarding this.
the results were:
enclosure pointing towards the rear of the vehicle positioned at the rear end of the trunk produced the best results. (albeit the most impractical for using your trunk space)
the next best result was having the sub firing to the rear, but with the enclosure up against the seat back
facing the sub forward, enclosure at rear of trunk was 3rd i believe, followed by forward firing with enclosure up against seat back.
the test was monitored with some hi-tech sound eqt. so if you want the actual specs you'll have to search on sounddomain.
 

·
Registered
Joined
·
1,598 Posts
I can tell you that the object to gaining the most out of your subwoofer is to mount it so that it resonates and 'pushes' all the surrounding air in front of it.
For example, the best possible location in a trunk, theoretically, would be in the spare tire well. This is hardly a realistic option because of the sacrifice involved. In this case, you would be resonating the maximum air available in any given trunk's volume.
The best places would have to be against the rear seat with the subs facing the trunk, or from either rear corner of the trunk facing the opposite corner. This will, in most cases, enable the user to push all of the air in front of the subwoofer.
Again, my experience with this and my reason for writing is to extract every ounce of gain from the subwoofer, not necessarily the best for sound quality. But then again, if someone was concerned with ultimate sound quality, they would most likely not be mounting the subwoofer in the trunk and more likely mounting it in the open cabin. That's a whole 'nuther ballgame. :)
 
1 - 13 of 13 Posts
Top