So, my trunk doesn’t rattle

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Leif

Copper - Posts: 71

Joined: July 15, 2004

Location: United States

Posted: July 22, 2004 at 8:28 PM / IP Logged

But my windshield does!

2001 Chrysler Concorde, four RF Punch HX2's (2212) on an RF 1500BD, iso-loaded, playing through the 8x9" hole in the rear seat (arm rest down).

Is there any way in hell to keep the windshield from rattling? I mean, how do people usually deal with this issue?

Yeah, I know, some people would say "turn the volume down, moron" but not us, right? :)

///Leif

xtreamcc

Silver - Posts: 467

Joined: March 24, 2004

Location: United States

Posted: July 22, 2004 at 9:10 PM / IP Logged

face the speakers towards the rear of the trunk and use dynamat, if u dont ur winsheilds gona eventually vibrate the seal off and it'll fall out.

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Leif

Copper - Posts: 71

Joined: July 15, 2004

Location: United States

Posted: July 22, 2004 at 9:18 PM / IP Logged

XtreamCC, I'm not sure what you mean exactly, or I just don't see how that would solve the problem. In order to get as much bass inside the car as I have now, I'd have to add a tremendous amount of power to overcome what would get absorbed in the trunk.

Also, the only hole into the car is that 8x9 inch hole in the back seat (with the arm rest down). If enough air is going through there to be as loud inside the car, wouldn't that put us right back at square one, except now we'd have BOTH the trunk and windshields rattling?

xtreamcc

Silver - Posts: 467

Joined: March 24, 2004

Location: United States

Posted: July 22, 2004 at 9:34 PM / IP Logged

ok, whats happening is the bass waves are not reflecting like they should. The waves are reflecting off your windsheild (u are talking about the windshield and not the rear window, right?) which is causing a bass reflex inside the car right infront of you. Turning the speakers around would cause the reflex off the trunk, it would prevent the waves from reflecting as bad off the windsheild and shouldn't cause a drop in the bass inside the car, just some rattling in the trunk to which I suggest sound deadner be applyed. Anyway, thats my take on it, other people might have other suggestions.

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defective

Silver - Posts: 642

Joined: August 20, 2003

Location: Canada

Posted: July 22, 2004 at 11:43 PM / IP Logged

direct exposure to the inside of the car from the trunk is completely unneccisary.... and sounds like ass!!

chevyman26

Copper - Posts: 227

Joined: April 14, 2004

Location: United States

Posted: July 23, 2004 at 12:06 PM / IP Logged

In most mid-size to full size cars pointing the subs to the rear of the trunk will increase your cabin gain by as much as 2 dB and placing them at the rear of the trunk firing towards the middle is good for another 1-2 dB, depending on the size of the trunk and sub box style. I agree completely with Xtreamcc and defective. You want your wave's reflex to happen at the rear first, then come up to you. This should also help to keep the bass from "fading" to the rear. Also, as the bass is non-directional as compared to listener position, there is no need for direct exposure to the trunk area. As long as the sub has the correct amount of air to "breathe", the sound waves will travel through the car just fine.

Just try moving your box around to different positions in the trunk if possible. You don't wan't your windshield rattling around for too long as they are only held in by RTV silicone(or similar sealing adhesive) and plastic trim pieces. Probably won't fall out right away or anything, but it's not something to chance! Good luck!

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Leif

Copper - Posts: 71

Joined: July 15, 2004

Location: United States

Posted: July 23, 2004 at 12:28 PM / IP Logged

Thanks for your answer, chevyman! I don't completely understand the phenomenon of acoustics yet.

Check out this sketch:

So, my trunk doesn’t rattle -- posted image.

The subwoofer enclosure has three chambers, so it's *technically* a Quasi 6th order bandpass, but the center compartments outside port is "tuned" much higher than the subwoofer actually plays (400hz or so, and the sub is lowpassed around 80) so it's pretty much negligible.

I do get excellent bass sound up front - very warm, very full, and VERY loud. However, the windshield, mirror and ceiling (i suppose) are vibrating from the pressure.

It doesn't really make sense to move this his particular box, it was designed and built to play through that hole.

My previous car was a dodge intrepid though (basically the same car) and I didn't get anywhere near this much bass with the subwoofers playing into the trunk, as I get playing into the cabin now.

///Leif

xtreamcc

Silver - Posts: 467

Joined: March 24, 2004

Location: United States

Posted: July 23, 2004 at 7:50 PM / IP Logged

ok, well the main problem with ur setup (now that I have a visual) is that ur using a 6th order bandpass box in a midsize car. 6th order bp's are an excellent SPL box, the reson for this is that that center chamber basically contains all this bass and line drives it in that single direction.

From the appearance of the sketch it would appear that turning the box around would possibly kill your bass inside the car simply because the box is just not built to resinate bass to the rear, thusly the box itself acts as a kind of muffle. With this I can offer the solution of a)get a different box or b) attempt to move the box as far back into the trunk as possible and do as chevyman suggested and move the box around till you find a point where the resinace isn't directly on your windsheild.

"Shiny chrome when used in conjunction with bikini models is particularly effective in inducing brain deficit disorder"

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auex

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Posted: July 23, 2004 at 8:22 PM / IP Logged

Replace the window with lexan and bolts, loose the subs, or just get over it?

Also how the hell does glass rattle? If the glass truly was what was rattling (which I highly doubt your windshield is what is rattling) then you have serious problems, like your windshield falling out when driving.

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Leif

Copper - Posts: 71

Joined: July 15, 2004

Location: United States

Posted: July 23, 2004 at 10:50 PM / IP Logged

Auex, you hit the nail right on the head.

Turns out it was just the mirror rattling. Strangely enough, outside the car it sounded like the glass itself was rattling, but when I took the mirror off, it stopped.

I turned the bass all the way up, closed the windows and doors, and stood outside the car. No rattles anywhere!

XtreamCC, it's technically a 6th order box, but due to the very high tuning frequency (and large size) of the outside port, it doesn't work like a normal bandpass - the box is designed to yield flat response (within 1 dB) between 22hz and 200hz.

So basically, problem solved. I have another mirror which rattles less - gonna install it later.

As a side note, I installed a yellow top in the trunk this morning, and the lights now do not dim AT ALL. Not even a little bit.. Man, this is starting to rock :).

///Leif

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