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View Full Version : Subs MUCH louder with trunk open (mid mounted box)



djbass101
06-09-2010, 01:10 AM
I have tried to go through the forum to find a solution to my problem, and tried a couple things dealing with cancellation (stuffed my trunk full of foam just to see if it would help), and I cannot figure this one out. I have made 3 different boxes (this one I finally found the specs to what my subs want for optimal), and I don't think it is my "box" per-say that is the problem as when I pop my trunk lid (opens only maybe 2 inches or so) it is like I have awakened the gods and shakes everything. I am running 4 10" and have included a crude MSPaint drawing to maybe help.

I am wondering if they were ported to the back that would fix it, or *sigh* do I need to move the box to the trunk and fire the ports forward.

If anyone can help I would appreciate it, I have spent way too much time and have admitted defeat.

KyleBechtold
06-09-2010, 01:13 AM
it lets it breath more.. its the same effect of opening your door with it sealed forward..

budahbuddy803
06-09-2010, 01:14 AM
that drawing just confuses me. is the box in the trunk or in the back seat area?

djbass101
06-09-2010, 01:15 AM
it is in the back seat area. Opening the doors or windows doesn't help a lick, but popping trunk makes the world of difference.

djbass101
06-09-2010, 01:15 AM
the seat that is labeled is the front seats... the back seats have been removed and the box build in place

djbass101
06-09-2010, 01:16 AM
the "large opening" is just meaning that without the seats the trunk and cab are not separated by anything (seats or baffle or anything)

cthedinger
06-09-2010, 01:18 AM
Will you post some pictures up of where the box is? If its the way I think it is I know your problem.

djbass101
06-09-2010, 01:19 AM
lemme grab some pics right now for yah

goingdef
06-09-2010, 01:20 AM
If you put the enclosure in the trunk firing at the lid that would be loudest I ran a 15" T2 in the backseat just to see what it would do and it was like a had a ten.

djbass101
06-09-2010, 01:30 AM
I know the box is not pretty, but again because this is box #3 I have been trying to get something that sounds good and work on finishing after.

djbass101
06-09-2010, 01:31 AM
@goingdef - now if they are firing at the trunk, is my port facing forward (towards the cab) fine, since I cannot fire the port up with this box because of port length issues.

HO-AUDIO
06-09-2010, 01:39 AM
All the bass is getting trapped in the trunk area close the box off from the trunk and your problem should be gone

djbass101
06-09-2010, 01:44 AM
All the bass is getting trapped in the trunk area close the box off from the trunk and your problem should be gone

now when you mean close the trunk area off, are you just talking about from air (making the seal air tight between the cab and trunk), or do I need to find some fancy way of deadening the sound waves going to the trunk.

djbass101
06-09-2010, 01:52 AM
also thinking about that if giving them more air is what they need then I don't think making their usable cab airspace smaller would help.. but then again I can be wrong as I have found :(

SQ Monte
06-09-2010, 01:55 AM
It's cause you have massive cancellation/standing waves in the trunk since it's not sealed off. Seal up your rear deck and the trunk from your box and you'll be good to go.

djbass101
06-09-2010, 02:06 AM
man I hope that works, it sounds AMAZING when the trunk is opened, and horrible with it shut. Again just to verify, you are talking about sealing it from AIR, or making it airtight.. correct. (as apposed to from the reverberations/sound waves, and meaning that I can achieve this by wood and sealant/caulking) I know this sounds like a REALLY stupid question, and sorry for me being nieve, but spent 2 weeks trying to get this working good.

SQ Monte
06-09-2010, 02:10 AM
Yeah man, you're gonna have to make sure no air can get into the trunk from inside the car.

Neel
06-09-2010, 02:19 AM
block off where the backs of your rear seat use to be.

djbass101
06-09-2010, 02:21 AM
Well I will try that tomorrow night, I am going to use a combo of wood, caulk and I think I am going use "Great Stuff" foam to help with the rear deck, since I think it is the only way of making sure all the little nooks and crannies are airtight. Apparently they market the "Big gap filler" as airtight.

Again I find it strange that it feels like they don't have enough "air" and by sealing the trunk it is being counter intuitive, but at this point I am up to try anything. But then going on myself again I should hear a difference with my windows closed/open, and there is really no difference in sound, only when I pop my trunk again... releasing the air pressure I guess from in there.

djbass101
06-09-2010, 02:29 AM
Thank you Everyone!!! for their input, I have been racking my brain on this, and do not understand it enough apparently to know the problem. I think this will be the quickest easiest fix. I know most won't care but I will tell the verdict if that fixed it tomorrow night.

I am hoping and guessing it will fix it as multiple people on the thread have told me to do the same thing.

SQ Monte
06-09-2010, 02:33 AM
Well I will try that tomorrow night, I am going to use a combo of wood, caulk and I think I am going use "Great Stuff" foam to help with the rear deck, since I think it is the only way of making sure all the little nooks and crannies are airtight. Apparently they market the "Big gap filler" as airtight.

Again I find it strange that it feels like they don't have enough "air" and by sealing the trunk it is being counter intuitive, but at this point I am up to try anything. But then going on myself again I should hear a difference with my windows closed/open, and there is really no difference in sound, only when I pop my trunk again... releasing the air pressure I guess from in there.What's happening is the sound waves are cancelling each other out in the trunk and you're getting major cancellation. Seal off the trunk and that won't be an issue because all of the sound waves will be kept in the cabin area so you won't have the issue with standing waves like you are now. My boy has a 300C with 2 12" Type R's in a forward firing box and it's sealed off from the trunk and that thing bangs! The fact that your box is subs up/port forward only makes that problem more noticeable due to the front and rear waves not aligning as they should. So I can't guarantee you that your cancellation issues will be 100% solved but I will assure you it will be a noticeable improvement!

on1wheel01
06-09-2010, 11:46 PM
Wow that looks terrible. You should just wall it.

djbass101
06-10-2010, 12:46 AM
Wow that looks terrible. You should just wall it.

Funny you say that it was walled... but I found the box/airspace was WAY too big.

Yah I agree it looks horrible, but because I have rebuilt it so many times I want to make sure it sounds good first, then I will worry about aesthetics later. Going to build the box to the edge and carpet it all. :D

Wingman0121
06-10-2010, 01:00 AM
Yep seal up the trunk(backseat and reardeck) and tell us how it sounds then.

ahole-ic
06-10-2010, 01:44 AM
if I worked for memphis I would break in and steal your subs so we wouldn't be represented in that janky *** install. That looks awful and there is no way it's loud. I don't want to offend anyone but let's just be honest here.

djbass101
06-10-2010, 02:03 AM
if I worked for memphis I would break in and steal your subs so we wouldn't be represented in that janky *** install. That looks awful and there is no way it's loud. I don't want to offend anyone but let's just be honest here.

Good thing I asked you for your opinion on how stage 1 of my install looks... may not have realized at this stage it looks like crap... *looks at posts above yours* oh wait I did say it looked bad already..... and that I am going to fix this...

djbass101
06-10-2010, 03:14 AM
Anyways, the foam dried and WOW huge difference. I still get a "noticeable" gain when I pop the trunk (but not nearly as extreme as before), but I have a feeling there are some air leaks that I know of that still need more attention/foam, but I ran out until tomorrow.

Kudos on everyone who told me this was my problem, once I finish foaming I can start looking at finishing the install and making it actually look like it belongs there.

cupid6969
06-10-2010, 03:25 AM
or instead of having your ports facing forward face them to the back if your going to run a wall then go forward other than that face the back you will see a differents and sound proof your trunk for sure and if your worried about the price pick up sound ash fault underlay it sound proof really good or rock gaurd works good too

djbass101
06-10-2010, 03:45 AM
Yah that was going to be my last option if sealing my trunk didn't go well (that is facing the port to the trunk). It seems like so far the foam is doing the trick, and wow they bang. As for the wall, I was hoping to do that originally, and I did, but became way too big for these small 10" subs and they just "free aired". After looking up that 2 of the subs require 2.75cu. ft MAX, that doesn't make for much of a wall, so I ended up rebuilding the box to meet the exact specs for these subs and happy I took the time to do so.