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Where are your IB subs located, in the rear deck?

I have a 2005 GTO, and am having a hard time visualizing where you have subs mounted in an IB config with the fuel tank in the way.

BTW: I'm finally getting my car to sound great, just with front components and a sub box in the trunk. No rear side speakers, and no rear deck speakers. I did do a LOT of sound treatment though.
 
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I tried 6.5" Tang Band subs in that location, and was never satisfied with them. When I treated the interior, I put CLD tiles on the rear wall, and then hung MLV over it as well. I left the 6.5" holes in the rear deck open, but put a 6.5" round, 4" thick piece of OCF in there, along with a 1/4" piece of CCF on top. So the high frequency noise of the fuel pump is blocked, but low frequencies can pass.

Then I just dropped in the Rockford P300-12 unit, and it's been great! I have it crossed over at 63hHz, and my door speakers (Hertz 6.5" mids) crossed over at 80Hz. The sound is very well balanced, and imaged out onto the hood ... and the bass is perfect. My trunk space is significantly compromised though ... which I assume you are trying to avoid?


If you happen to be somewhere near Central Texas, I'd be happy to let you listen?

These cars are definitely a pain to figure out, and I'm doubtful you'll ever be satisfied with an IB setup in the rear deck.

For those who don't know, here is what it looks like under the rear deck. This pic was taken when I still had the 6.5" Tang Band woofers in place ... and I had to trim the fuel tank strap a bit for them to clear. Yes, that large black plastic thing is the cover over the fuel tank.

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Here's what it looks like on the inside, with the seat cushions removed

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I did CLD:

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And MLV:

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And I'm still not sure an IB setup would work ... there are more holes on the sides, where the wheel wells are, which extend into the trunk area. I used these to pass signal and power cables through.

But for an IB setup, they would all have to be damped and air sealed. I don't think CLD alone (ie: Dynamat) is enough to seal it off completely.
 

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What exactly did you use to block out the fuel pump noise?
My wife had some 4" thick foam left over from a project she was doing, and I cut two circles out of it. It was white though, so I topped them with black second skin closed cell foam I had left over ... so when the rear deck cover is in place, you don't see anything through the speaker grills. The OCF and CCF combo blocks out the noise from my stock fuel pump. When I 1st put everything together, I just left the holes open, and the fuel pump noise was too much. The foam circles did the trick though, since the frequency of the fuel pump is so high.

What's with the rectangular sheet metal spot dead center in the rear fire wall? Can that be replaced with a 1.5" thick plywood baffle for a 12 or 15? Or is there something lurking there?
Yes, the fuel tank is lurking behind that panel ... scroll up and see my post above.

The fuel tank in these cars is located in the trunk.
 

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Scroll up and see the pictures I posted. Without the mounts, you can't fit any speaker in there at all, as the magnet will hit the fuel tank. I'm surprised he got 8" in there to begin with!
 

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Unless...you built a slanted baffle and used the two 8" holes as vents. You could still keep 95% of your trunk, too. Just have a baffle at a slight angle to force the sound through the rear deck?
The fuel tank is in the trunk, behind that flat panel, under the rear deck. It extends from the right to the left, taking up the entire space under the rear deck, and extends toward three rear of the car, past the 3rd brake light in the rear window.

There’s really no opportunity for a slanted baffle to vent through the rear deck.

The car is actually a Holden Monaro, rebadged as a Pontiac GTO. The story is that GM was forced to relocate the fuel tank into the trunk to meet USA regulations. Apparently the tank hung too low with the Aussie design?
 

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you could be on to something. Maybe I should try opening the holes up in the back deck.
Have you thought about building enclosures for the 8" woofers, to fit behind the rear sail panels? I think you would get more of what you're looking for by doing that, instead of trying to make an IB setup work in the rear deck.

There's a guy in Australia who printed enclosures for 9" woofers to fit that space ... He's a great guy too, and might be willing to share his 3D printer files with you? Let me know if you want his contact info.

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If you don’t mind opening them up so they can mount flush without the adapters it would probably be worth it.
There's not enough depth to flush mount anything back there. There really is no room under that rear deck.
 
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I can’t imagine the sound being able to make its way out of that little 4-4.5” grill on the side panel...and it not rattle badly.
Subwoofers work very well in that location. The sound doesn't need to make its way out of the 4.5" grill, as sub frequencies are not stopped by the trim panel.

Many guys have installed 8", 10", 12" and even 13" shallow subs in there with great results. Hendrix engineering used to make fiberglass enclosures for it even, but they stopped offering them a few years back due to such low demand (ie: limited number of GTOs on the road).
 

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How does the plastic panel not rattle tho? For that matter, I bet I could stuff some bazooka tubes in there. I’m kidding. Wait...am I? I need to do some measuring now..... that wouldn’t be a bad idea.....
You just deaden the panel.

Here's some info I found a while back, when I was researching it. This guy put 8" woofers inside MDF boxes he built for the space. I think the 3D printed designs are MUCH better, but this gives you an idea of what can be done with the space.

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Yea I saw those boxes long ago, I have that picture of the measurements saved in my phone. I never really considered that because I thought the panels would rattle.
I think as long as you treated the area appropriately, it would be fine.

For my car, I put CLD on anything which seemed to resonate ...

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.... then I followed it up with MLV inside the cavity, and CCF anywhere the trim panel made contact with the body. I actually don't have these rear speakers even hooked up, but ... all rattles and vibrations were removed from doing this. It also significantly cut down on rear tire noise coming into the cabin (due to the MLV)

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What do you mean breathe? IB is the ultimate "breather". Explain please.
He's talking about opening up the hole in the sheet metal, since it's barely large enough to allow the magnet to fit through.

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That's the fuel tank under the sub, and you can see where the magnet is making contact with the fuel tank strap.

I don't think opening up this hole will help the 8" subs ... now if opening up this hole, and printing new mounts to allow 10" subs to be mounted would work ... that's a good choice.

@KFXGUY ... Have you considered shallow 10" woofers and a new mount design to allow them to fit under the rear deck cover? I think a 10" woofer's magnet could fit through the rear deck sheet metal, without having to modify the base footprint of your adapters where they mount to the deck.
 

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I may print a 10” adapter this weekend and see what it looks like. I really don’t think it will fit. I’ll try it tho. I’m going to open up the holes anyways.
Ya, open up the holes to the limit your adapter mounting base will allow, and then try printing a 10" adapter which uses the same mounting base dimensions your 8" ones use.

Is your 3D printer large enough to print an adapter this sized?

If you get the 10" adapter to work .... let me know how much $$ for a set LOL! I'd love to get the sealed 12" box out of my trunk and reclaim the space :)
 

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You don't need a ten inch hole in the deck. Depending on how the baskets are made you might be able to get away with an 8 inch hole.
Especially with the added hight of the adapters.
A sub with neo magnets would be pretty cool too.
The issue is going to be depth. With the factory adapters, there's a depth of about 2 5/8" before making contact with the fuel tank. Some folks add a 1" spacer on top of the factory mounting adapters, to get 3 5/8" mounting depth; but in this case, KFXGUY can just print his adapters 1" taller ... although with 10" drivers, interference with the rear window now comes into play.

Here are what the factory mounts look like for the stock 6.5" subs ... very similar to what he has printed for his 8". The picture is a bit deceiving, as the rear of the mounts are a lot closer to the rear window then it seems in the pic.

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Then there's this cover which goes over the top (I added CCF as a decoupler to the bottom of mine)

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And here's what it's like when put back together

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Maybe the rear deck cover is rattling, and that's what you are hearing? Mine rattled pretty badly until I put closed cell foam on the entire underside, and that was without any speakers in the rear deck at all. It was rattling due to the sealed 12" sub I have in the trunk.
 

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Oh, and check your 3rd brake light clips. They have a tendency to crack/break, and when they do, the 3rd brake light housing rattles really badly as well. One of mine is broken, so I used butyl rope to affix it, and keep it from rattling when it's mounted in place.

The more you describe what's going on, the more I wonder if you are hearing stuff rattling, and mistaking it for distortion.
 

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the brake light.... the clips have anti rattle foam and so does the rest of it. There's no rattling..oddly...


edit..... does it with the back deck cover and brake light off too... forgot to mention that...
Ahh, ok ... I misunderstood your previous message then ...


It also sounds better wioth the back deck cover off because I think i'm getting some cancellation going on because i didnt put foam to direct the sound out. Which I knew better but I had to get the car back together. I think i'm going to put velcro on everything to take it apart faster lolololol
You don't need foam to direct sub frequencies out. It takes a lot more than that rear deck cover to stop them.

Foam is good for door speakers (ie: mids and highs), but not needed for subs and mid-bass.
 

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The woofer should be sealed to the mount you printed, and the mount should be sealed to the rear deck metal. So long as the backwave is separated from the front wave, you won't get cancellations.

I would put soaking wet bath towels on top of the fuel tank cover.
 

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thats an excellent idea.....I was over thinking it again!

The sub is sealed to the mount and the mount is sealed to the deck.
If you have a welding blanket, that wouldn't be a bad idea as well.

If the subs are sealed to the mount and the mount is sealed to the deck, then you aren't getting cancellations from the backwave. Neither the deck cover, nor the hole size in the deck, would impact this.

Or they meant to just throw in the towel?
No way! I really want him to succeed, as it means I could follow suit and do it to my GTO :) ... so long as he agrees to print me some mounts too ;)

Actually, if he succeeds, I'm sure there are plenty of guys in the LS1GTO community who would love to follow suit. I could see a kit being marketed, with a template for the plasma cutting, and then the mounts provided to bolt up 10" subs. Guys with this car have tried all sorts of things to get good sub-bass into it, and there's no real good options on the market besides dropping an enclosure into the trunk .. but then you lose the use of the trunk. There was a company who made fiberglass enclosures for the rear seat side panels, but the R&D and manufacturing of them was too costly for the demand side. These cars were only made from 2004 - 2006, and many of them aren't even on the road anymore.

I'm a musician myself, and with the sub in my trunk, I can't even fit my guitar case in there with it. I have to load my gear in the back seat when I need to transport my gear in the GTO :(
 
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This will give an idea as to what I'm talking about ... a picture is worth how many words?

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Lol he's heard that before man. 3 threads. For real.
How he ended up with the dsp.
It'll probably work better this time around though.
With all the work he is putting in I would build a shallow box beneath the deck and throw 2 jl tw10s in there.
I mean he has a printer. With the right design bass should be no problem for him really bow that I'm thinking about what can printed....hexibass.
have you looked at the pictures of what’s below the deck?

there ls no way anything can fit under there.
 

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You're just not comprehending the space. There's about 2.5" to work with, and that's at the far end. So 1.5" or so at the shallow end. In order to use it though, you'd have to cut out the 2 braces (which are the mounts for the fuel tank brace), as well as get rid of the fuel tank strap unions on top of the tank.

In this picture, you can see where I trimmer the top of the fuel tank strap union, just to get my 6.5" tang band woofers to fit .. and those have a mounting depth of less than 4". So with the factory adapter in place, and a 3.9" mounting depth driver, I still had to cut the top of the strap for it to fit. The factory adapter is about 2" or so ... which means it is less than 2" from the deck to the fuel tank strap.

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