stealth panel and sound limitation?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=80682
Printed Date: April 28, 2024 at 10:15 PM
Topic: stealth panel and sound limitation?
Posted By: intargc
Subject: stealth panel and sound limitation?
Date Posted: July 24, 2006 at 8:26 AM
I have a 2003 Audi A4. A few days ago, I had a system installed at a local shop. I had 2 12W3v3's installed along with a 500/1 amp. I originally asked for the install to look like the picture below (discluding the amp racks on the sides).
So, basically, a panel that covers the box and sits flush with the back of the trunk so that it looks like the subs are kind of built into a wall. I wanted it to look clean and just not look like I have a box just sitting back in the trunk. Nothing too fancy...
However, when I came to pick the car up, he did a sort of "stealth" panel. He didn't cut out any holes on the panel at all and it just covered up the box behind it and made it look like there was nothing there but the back of the trunk. Which, I thought might be kind of cool not being able to see the subs and it gave it a very clean appearance. The panel is mounted to the box by being drilled into 3 pieces of wood that are drilled into the the front of the sub box that are about 1" thick.
Here is my problem:
Yesterday when I was cleaning the car out, I figured I wanted to take a look at the subs. I mean, I bought them, and have yet to actually see them. I like looking at subs for some reason...
Anyway, I removed the 4 screws and pulled the panel back and looked at the subs... They're wonderful looking. I didn't put the panel back on for a while and drove my car back home. During the drive home, the bass from the subs felt A LOT more full and even seemed louder. I got curious... So, I did a little experiment...
I got my drill and pulled into a vacant parking lot. Cranked up the subs on a song with a great bass line that was consistent throughout the track. I started with the panel off. Listened for a minute, then, ran back to the trunk, drilled it back into place and went back and sat down. I noticed a clear difference. I did this like 8 times, literally... Just to make sure that I wasn't playing mind games with myself somehow. It was a lot more full sounding. It seemed to fill the cabin up more with the panel off.
So, I called the place that installed the panel. He immediately said "That would not matter. The panel is not keeping any sound from coming into the cabin". I asked "would it make the bass sound more full if it had the entire trunk to bounce around off of instead of having a thick piece of carpeted MDF directly in front of it which would cause vibration and even maybe some sort of absorbing of the sound?" and he said "Not at all". I even asked "Is it possible I just think that it's louder and I'm tricking myself into thinking that?" and he said "I'm not sure, but there should be no difference with the sound in the cabin. It will be louder in the trunk, but not in the cabin."
My question to anyone here is, does that sound right? I'm very sure the sound was more full and generally sounded like 2 12's should sound. With the panel on, the sound was a little more "tight" or muffled sounding and not as full. If I'm in some way correct, should the panel be removed completely for this sound, or would it be fine to actually have someone do it the way I wanted it originally (in the picture above) or would that muffle the sound as well?
Replies:
Posted By: xtremej
Date Posted: July 24, 2006 at 8:55 AM
Trust your ears. If that is the install you wanted and you provided them with this pic, then take it back and have it re-done. I am sure it would make a differnce on how things sound.
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Posted By: intargc
Date Posted: July 24, 2006 at 9:02 AM
xtremej wrote:
Trust your ears. If that is the install you wanted and you provided them with this pic, then take it back and have it re-done. I am sure it would make a differnce on how things sound.
I showed him the picture a few days before the actual install to see if he could do it and how much it would cost. Then, I noticed on the final receipt it said "Stealth panel"... Which, I knew wasn't what I wanted. However, when I saw it, I thought it looked good. It was clean looking. But, yeah... I showed him the picture so I could get an good estimate on how much the install would cost. I just think the installed saw "Stealth Panel" on the work order and did what he thought was a stealth panel.
When I called the installer, he said that he could cut out a large section on the panel that basically went around both subs, but that kind of defeats the purpose of that entire panel, I think... I might as well take it out all together. However, that means I just wasted $100 on a carpeted panel that does nothing.
I guess I can just turn my donut holeness on if they refuse to do it correctly... However, I feel that since I accepted the work when it was done and drove off, it's somewhat my fault as well. However, I liked how it looked... I'm just not happy with how it sounds with that panel on.
Posted By: markcars
Date Posted: July 24, 2006 at 9:10 AM
You are absolutely right in the fact that the sound in trunk will be louder without a panel/thick cover. However the shop has a point as well. The sound in the cabin would be coming directly from the rear of the speakers (as I understand the speakers are mounted on a "wall").
As extremej pointed out, do what you like best to hear. Ultimately it is your car, your money and your ears. The shop has to give you your money's worth and satisfy you since they are being paid to do so.
Can you post some pictures for us to see?
Posted By: intargc
Date Posted: July 24, 2006 at 9:15 AM
markcars wrote:
You are absolutely right in the fact that the sound in trunk will be louder without a panel/thick cover. However the shop has a point as well. The sound in the cabin would be coming directly from the rear of the speakers (as I understand the speakers are mounted on a "wall").
As extremej pointed out, do what you like best to hear. Ultimately it is your car, your money and your ears. The shop has to give you your money's worth and satisfy you since they are being paid to do so.
I'm not saying the sound in the trunk was louder. The installer said that the sound in the trunk would be louder, but not in the cabin. I'm saying it was louder in cabin as well.
The speakers aren't mounted on a wall. They're in a regular sealed inclosure with a piece of carpeted MDF drilled into the front of the box (with about 1" of space between it and the subs).
Posted By: markcars
Date Posted: July 24, 2006 at 9:25 AM
Without a panel on the front of the speaker, the front would be having no hindrance, so the sound there would surely be louder in the front of the speakers (inside the trunk). The rear of the speakers has no change therefore there shouldnt be an increase from the rear of the speakers. However, part of the reflected sound from the front(inside the trunk) finally would also reach the cabin adding to the volume. So the overall sound would feel louder in the cabin as well but not as much increase as inside the trunk.
Seems like the installer isn't talking about net result of sound, but direct sound from front and direct sound from rear of the speakers. If you look at each of your points of view, both are correct.
Posted By: intargc
Date Posted: July 24, 2006 at 9:45 AM
markcars wrote:
Without a panel on the front of the speaker, the front would be having no hindrance, so the sound there would surely be louder in the front of the speakers (inside the trunk). The rear of the speakers has no change therefore there shouldnt be an increase from the rear of the speakers. However, part of the reflected sound from the front(inside the trunk) finally would also reach the cabin adding to the volume. So the overall sound would feel louder in the cabin as well but not as much increase as inside the trunk.
Seems like the installer isn't talking about net result of sound, but direct sound from front and direct sound from rear of the speakers. If you look at each of your points of view, both are correct.
So, in other words, having a 1/4" piece of MDF attached directly in front of the subs will not cause any sound problems, muffling or anything in the cabin area?
Not to cause an argument or anything, but my question is, how come it sounds much fuller in the cabin area with the panel not in front of the speakers? The bass sounds cleaner, fuller and not as muffled with that panel off. I noticed that the actual panel rattles a lot when it's on. Could that be part of the problem?
Posted By: intargc
Date Posted: July 24, 2006 at 9:54 AM
I talked to him again and he said he's willing to cut out two circles on the panel and put the grilles on the speakers for protection. I just have to pay for the grilles, so, I guess I'm just going to do that and see how it works out...
Posted By: markcars
Date Posted: July 24, 2006 at 9:59 AM
I don't know why anyone would cover up the front of the subs. You would surely lose any sound from the front of the subs if you cover them up, especially with a 1/4 inch thick MDF. Unless you are creating a ported bandpass subwoofer box, I wonder why the front of the speaker should be covered up. Glad to hear you are getting holes cutout and grills are definitely a saver for subs. I would have destroyed my Focal Utopia 27wx sub a few weeks ago had it not been for the grill on the front, which got bent out of shape due to something I purhased from home depot. My sub got saved with the grill. I cannot afford to buy that sub again.
Posted By: intargc
Date Posted: July 24, 2006 at 10:05 AM
markcars wrote:
I don't know why anyone would cover up the front of the subs. You would surely lose any sound from the front of the subs if you cover them up, especially with a 1/4 inch thick MDF. Unless you are creating a ported bandpass subwoofer box, I wonder why the front of the speaker should be covered up. Glad to hear you are getting holes cutout and grills are definitely a saver for subs. I would have destroyed my Focal Utopia 27wx sub a few weeks ago had it not been for the grill on the front, which got bent out of shape due to something I purhased from home depot. My sub got saved with the grill. I cannot afford to buy that sub again.
He covered them up because he thought I wanted a "stealth" look. Which, I didn't... The salesman screwed that up. Even still, I've had a stealth box before and the MDF panel that was in front of it at least had large 1/2" holes drilled out around where the speaker was and then carpet laid over that...
Posted By: AZ-ss
Date Posted: July 24, 2006 at 10:55 AM
So, they installed a SOLID panel in front of the subs, charged you a hundred bucks and said that it would have no effect on sound?  WOW, thats all I can say.
That, and maybe find another shop or an installer that has a clue.
Posted By: intargc
Date Posted: July 24, 2006 at 12:37 PM
Well, it was done by HiFi Buys and I have always been very happy with the custom work they have done on my cars. They seem to be very knowledgeable and very nice all of the time. Many times (back in the days) when I tried to dabble in my own installs, I would either go up to HiFi Buys or call them and the install guys would sometimes go out of their way to help me figure out what I did wrong without me even paying them...
However, I went to a different shop this time because I moved away from the normal Hifi Buys location I used to go to.
Anyway, he said he'll cut some holes in the thing and mount the grill's on the panel. I assume I should be able to convince him to remove the 1" gap between the box and the panel and drill the panel directly to the box and then insert the subs through the panel into the box so that it gives a look as if the subs were built into the back wall of the trunk. That's what I really wanted all along...
Posted By: Flakman
Date Posted: July 24, 2006 at 1:04 PM
What I think is happening is that the distance between the subs and the back of the trunk is allowing the sound waves to come back and cause constructive interference with the sound coming from the back of the subs into the passenger compartment. It may have worked out just right in your case...if the box were built slightly differently, you might have had destructive interference where the sound waves would have been cancelling each other out causing less bass. A lot of times it is best to avoid those possibilities when designing the system...it is always nice when the box, tuning, and car all come together to allow for everything to hit your ear just right!
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The Flakman
I feel strange. I have deja vu and amnesia at the same time.
John | Manteca, CA
Posted By: AZ-ss
Date Posted: July 24, 2006 at 4:36 PM
Flakman wrote:
What I think is happening is that the distance between the subs and the back of the trunk is allowing the sound waves to come back and cause constructive interference with the sound coming from the back of the subs into the passenger compartment. It may have worked out just right in your case...if the box were built slightly differently, you might have had destructive interference where the sound waves would have been cancelling each other out causing less bass. A lot of times it is best to avoid those possibilities when designing the system...it is always nice when the box, tuning, and car all come together to allow for everything to hit your ear just right!
Uhm..... no. In this case, sound "bouncing" off the back trunk wall would have better response. It's not as complex as you are making it sound. With the panel in place, you have a dual sealed chamber bandpass box . (Sealed rear chamber, semi-sealed small front chamber) In other words, you have a bandpass box with no way for sound to vent out of it. The box designer just didn't have a clue (or materials) to correctly execute what he had in mind, and didn't bother to PAY CLOSE ATTENTION to what the owner originally wanted. (According to teh picture posted.)
Posted By: intargc
Date Posted: July 24, 2006 at 6:29 PM
[quote]With the panel in place, you have a dual sealed chamber bandpass box . (Sealed rear chamber, semi-sealed small front chamber)
In other words, you have a bandpass box with no way for sound to vent out of it. [/quote]
That's exactly what I thought as well. I mean, the panel is literally pressed up against the speakers with very very little room to breathe. While the panel is about 1" off of the speaker box, the subs mounting hardware is about 3/4" - 1" thick... So, the panel is pretty much pressed up against the mounting hardware for the subs.
They said they'll fix it up on Thursday. My question is, will this damage the subs at all while playing them? I would assume not, but I'm not so sure...
Posted By: Flakman
Date Posted: July 24, 2006 at 6:42 PM
Ahhh...didn't get the picture right in my head. Good catch AZ. ------------- The Flakman
I feel strange. I have deja vu and amnesia at the same time.
John | Manteca, CA
Posted By: AZ-ss
Date Posted: July 24, 2006 at 7:40 PM
intargc wrote:
[quote]With the panel in place, you have a dual sealed chamber bandpass box . (Sealed rear chamber, semi-sealed small front chamber)
In other words, you have a bandpass box with no way for sound to vent out of it.
That's exactly what I thought as well. I mean, the panel is literally pressed up against the speakers with very very little room to breathe. While the panel is about 1" off of the speaker box, the subs mounting hardware is about 3/4" - 1" thick... So, the panel is pretty much pressed up against the mounting hardware for the subs. They said they'll fix it up on Thursday. My question is, will this damage the subs at all while playing them? I would assume not, but I'm not so sure... [/QUOTE] If the panel is too close to the speaker, you run a chance of the surround rubbing up against the backside of the panel. If you see a white-ish ring along the top of your subs surround, it was touching the backside of the panel. In most severe cases, the surround is extremely weakend, worn through and likely tears.
Posted By: intargc
Date Posted: July 28, 2006 at 8:14 AM
Ok, so here is the outcome...
I took them the panel yesterday. I slid my hand in between the panel and the box and felt around for the speaker. There was no space between the speaker and the wall at all. You could MAYBE slide a piece of paper between the two with some wiggle room. However, I couldn't even get my pinky finger between the panel and the speaker (I have skinny fingers too!). In other words, I'm sure when I had the system turned up loud, the subs surround or speaker had to be hitting that wall a bit.
So, what they did was cut out a large rectangle section on the panel. He then put a metal mesh grill in that rectangle area and covered it with carpet so you can't see the hole or mesh grill.
However, this leaves maybe 1/4" between the speaker and the mesh part of the panel now. Is that enough room? I can slide my middle finger in between the two now. I'm just worried as I don't know how far the speaker pushes out during high volume and very low bass. I know for a fact the speakers were hitting the panel before. You could hear a sort of slappy sound during high volumes (in which I quickly turned it down). I don't hear this really anymore. But, I'm still worried. Should I adjust where that panel sits?
What I can do is get thicker pieces of wood that attach to the box. There are 3 1" thick pieces of wood that attach to the box and then the panel attaches to those. I can maybe get 1.5" blocks of wood at home depot or something. That is, if you guys think it would be a good idea... If you think I'm safe now, please let me know...
Posted By: AZ-ss
Date Posted: July 28, 2006 at 9:45 AM
Did you check the speaker for rub-marks? What kinda sub are we talking about anyhow? (brand & model) Did you voice your concerns to the shop about the surround rubbing?
Posted By: intargc
Date Posted: July 28, 2006 at 9:50 AM
2 JL Audio 12W3v3 Subs.
I looked at the subs when he took the panel off and I didn't see any marks or anything. However, I didn't get close up on them and look either.
Yes, I voiced my concerns and of course they weren't very receptive to what I said since I'm not well educated on all of this. I just kept hearing over and over "I just don't see how this panel blocked any sound..." And, yet, they wouldn't test it with and without the panel to see my point... But like 3 guys said the "I can't believe..." line and even stuff along the lines of "We've done that setup before and it didn't block out any sound" or "It sounded good to me before you left". So, I just said "Hey, maybe I just somehow mysteriously tricked myself into thinking it was better sounding. However, I've managed to trick myself and I would like it fixed regardless."
Posted By: AZ-ss
Date Posted: July 28, 2006 at 10:39 AM
Good sounding sub. It's shops like those that give me great clients. I cannot stand the "we know everything and you can't know jack" attitude. Come on people, it's car audio not neuro-surgery. From what I've seen of the W3v2 series, they do move a fair amount. You have a legitimate concern. I would give them at least a half inch of space between the rubber face of the mounting flange and the backside of the grill. How to get it done? That depends on how the grill assembly is attached to the face of the box. If you can take some detailed pics I'm sure a solution can be suggested. Should you do it? Sure. If you can look past the fact that you forked out the $$ for them to do it and you have to spend some time and get your hands dirty. OH YEAH, it also depends if you have some knowledge of power tool safety and have access to some power tools. (drill, saw and stapler)
Posted By: AZ-ss
Date Posted: July 28, 2006 at 10:42 AM
typo^ I've also played with the W3V3. (dirr!!)
Posted By: intargc
Date Posted: July 28, 2006 at 1:00 PM
Ok... I took some pictures. They're High Res, so I'll just let you go to the link below and view them. You can see what I'm talking about a bit.
You can see the pieces of MDF that he has attached to the box that the panel attaches to. They're not giving much room at all. It's pretty much flush with the speaker hardware.
I'm thinking I can find some thicker pieces of MDF to put in the place of the 3 that are already there. Another 1/2" and I'd be good. I just don't know where to get MDF from. Home Depot??
[url]https://www.totaldeanism.com/images/box/[/url]
Posted By: xtremej
Date Posted: July 28, 2006 at 1:15 PM
You don't have to use mdf. But if you want to try calling some cabinet shops or other car audio shops to see if they have any chunks laying around . I would just use pine, it will work fine and it easier to work with. Maybe buy a 2x3 and chop it up that would give them plenty of room to move around. -------------
Posted By: AZ-ss
Date Posted: July 28, 2006 at 1:16 PM
No Problem! You can probably get away with only adding 1/4 inch strips on top of the strips already mounted on you box. You can glue them in place with a quality wood glue (gorilla is good) Also, I would add a strip of carpet in between the grill and the strips that you add. This is in case the grill flexes, it's not going to rattle against the the wood. Also, if by chance you notice any ringing from the metal mesh grill against the wood border it's mounted to, run a bead of THICK glue or silicon where the wood and mesh grill meet. Good Luck!
Posted By: intargc
Date Posted: August 01, 2006 at 8:07 AM
Just wanted to thank everyone for their help.
I went to Home Depot and found 1" MDF. Had them cut 3 strips that match the site of the current ones and got some Gorilla glue. Glued them together (That stuff is messy!) and put everything back in place. Looks like it did before, but now there is plenty of space between the panel and the speakers and I'm happy.
I just don't get how the installer didn't notice this or even care about the panel being SO close to the speakers. There was about 1/8 of an inch between those speakers and the panel and he said there was "No way that there would be any sound limitation in the cabin due to the panel."
All I can say is that I know I won't be going to that HiFi Buys again. I'll just make the longer trip out to the Kennesaw (the one I always went to before) HiFi Buys next time I want custom work done. They always did everything right in that location.
Posted By: AZ-ss
Date Posted: August 01, 2006 at 2:30 PM
Awesome! If there is anything that is more frustrating than a shop doing shoddy work, it's when the shop acts like they can do no wrong and that the customer doesn't know jack. Hope you enjoy. And you should pit your system up against one of their "No way that there would be any sound limitation in the cabin due to the solid panel." (sigh) morons. Then again, maybe they know something I don't, like how to defy the laws of physics (riiight)
Posted By: intargc
Date Posted: August 01, 2006 at 2:49 PM
I just gave up on trying to convince them. I know for a fact that it sounds a lot better now. I just know I won't go back there again.
Thanks again for your help.
Posted By: stevdart
Date Posted: August 01, 2006 at 7:39 PM
Good thread! But the part about the Gorilla glue being messy...NOT! It's about the un-messiest glue you can use for wood. Did you use it right, glue on one side and spray water on the other? I use a 1" putty knife to spread the glue thin. When the glue cures in a couple hours and expands along the seam, just scrape it off with the knife. No mess.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
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