2Cool4Skool

iTrader: (2)

This is for a 10" ported subwoofer install in the cubbyhole space behind the driver's seat. I felt this was the best compromise for performance and the most efficient use of the space available.

I measured the area with packing peanuts and was able to stuff ~2.5 cubic feet of peanuts into the area which is what is the ideal ported box size specified for my subwoofer.

materials used:

• 10" Infinity Perfect VQ subwoofer
• Subwoofer specs: mounting depth 6.5", basket displacement .072 sq feet, 11.5" x 3" port tube
• Dynamat trunk kit
• scizzors
• bright flashlight
• black silicone
• Port: flared 3" diameter tube cut to 11.5" total length
• 10 gauge speaker wire
• Glue: epoxy
• saw
• Sharpie marker
• 2 DVD cases
• 3 bags of packing peanuts from Staples (1 cubic foot each)

1) Take out everything: plastics and metal subwoofer mounting plate.
2) Plug up corner where seatbelt is mounted with dynamat and flat pieces of plastic. I used a couple DVD cases and cut them into shape.
- Fill any gaps with black silicone.



3) Plug up the other corner using Dynamat with subwoofer speaker wire poking through (I used 10g speaker wire)
-Fill gaps with lots of black silicone



4) Layed down pieces of Dynamat in 1 layer covering every square inch of the space. Conform the Dynamat to contours to maximize space and rigidity.
-I didn't measure anything. I just used small pieces of Dynamat and filled in the gaps with smaller pieces of Dynamat.
-I didn't cover over the access plate below just in case I needed access to the fuel pump (?) later on. I just Dymatted around the plate and put a piece on top of the plate leaving the mounting tabs open. Silicone was used around the plate to eliminate any air leaks.



5) Checked for light leaks by shining flashlight on the other side. Plug up leaks with black silicone.
6) "Taped" port tube into the rear corner using Dynamat on both sides & held up with a zip tie. Port is located in the rear center area porting into the other side.



7) Check for leaks with flashlight one final time and plug with black silicone.
8) Dynamat the metal subwoofer mounting plate.
9) Add fiberfill as needed. ~30% more volume using 1.5 lbs per sq ft of space. I used only .15 lbs per sq ft of space = 2.5 - .072 (woofer vol.)x .15 =
0.3642 lbs (5.83 oz.) of fiberfill. This is only to make up for the volume displacement of the subwoofer.
10) Connect the speaker wire and mount subwoofer into place. My 6.5 inch depth subwoofer barely fits after the layer of Dynamat raises up the mounting plate enough to keep the bottom of sub away from the plate below. I think the plate gives access to the fuel pump?



I'm running 460 watts rms to the sub.

I ended up using about 1/2 the Dynamat trunk kit to seal the area.

So far it sounds great. It sounds as good as my previous setup with a ported MDF box.... maybe even a bit better since there's more space. The only concern I have now is once I put the plastics back in and the glovebox door is shut, the bass from the port might get muffled a bit as its being ported into an enclosed space.

I'm thinking of drilling holes out the back of the other side of the compartment which would allow sound to go to the rear.

dcains

iTrader: (15)

That's pretty scary-looking. I can't imagine it sounds as good as a 10" in a properly-designed sealed box, but to each his own.

GreyZ

iTrader: (2)

I understand the desire for this kinda setup 100%. but this is the kindof stuff that is always shitty to find for the next owner.

dboyzalter

iTrader: (3)

Wow I thought I posted this same thing in this same thread... so confused right now

dboyzalter

iTrader: (3)

O well maybe I never hit the post reply button, pretty sure I said looks good but cant imagine It sounds as good as one in the hatch, maybe my post got deleted I was kinda being a dick bag yesterday.

I would put my $50.... 8 inch sub in its $12 enclosure in a sound off competition against any sub mounted behind the seat. Its just not a great spot.

dcains

iTrader: (15)

You can get a 10" to sound good in that location, but it has to be mounted in a proper, sealed box - not in the plate for the OEM Blose in an open enclosure.

2Cool4Skool

iTrader: (2)

OK, I know what you guys are saying but the only comments I've found on a search saying this is a bad setup are from those who haven't actually done it and listened to it. If you think about it, there are fiberglass boxes that have sounded OK & I can't imagine them being very stiff. There are people who have made a box out of the glove compartment and they say it sounds pretty good, so why wouldn't the metal subframe properly sealed be a fine subwoofer "box"? It seems plenty stiff enough.

IMO, its as simple as these 2 things:
1) sealing
2) proper internal volume for specific speaker

Anyways, after finishing it, I listened to it last night against another 10" Infinity Perfect (non VQ) mounted in a ported box also with the proper volume. My MDF ported box sounded better and not "muffled". I checked my subwoofer again and I saw there were several holes leaking air. You can see it in the pic in the front bottom. I plugged up those holes and it instantly sounded better. But my MDF box still sounded a bit better.

So to check if port blockage is causing a problem, I partially blocked my MDF box subwoofer near the port to see if there was any sound degradation. Sure enough, the bass from the MDF box did not sound as clear and my MDF box now sounded about the same as my setup.

The solution (as mentioned earlier) will be to drill some "scary" holes at the top corner where the port exits to allow for clear passage of sound waves. I'm not worried because the scary holes would not be visible after everything is put back together. There would be speaker cloth covering the plastic cutout making it look like it came from the factory.



As you can see, with the glovebox installed, it will block the port muffling the sound. So in theory, with scary holes drilled. it should sound great. I'll be doing this tonight. Your suggestions & criticisms are still welcome.

dcains

iTrader: (15)

The Z33 has been around for 13+ years now, and trust me when I say that everything you can think of has been tried/done before. If you want the sub in the stock location, you need a good, sealed box. Like this one:



Then, there's the issue of ported v. sealed. Sealed sounds better to those who want an accurate sound, ported might be louder.

dboyzalter

iTrader: (3)

Cost like $15 to make... Works for me, my amp is in that cubby behind the seat.

HRMoneyPit

I want one of those little sub boxes to install in the stock sub location....but I like go fast parts over a system in a car I never drive. The sto'clock Bose does the job

dboyzalter

iTrader: (3)

dcains

iTrader: (15)

What the OP is missing here is the basic physics of how an air-suspension speaker system works. It's really all about the enclosure, and the way his is designed, there isn't one. Be it ported or sealed, the speaker driver needs air to compress in its enclosure, thus the "air suspension". The enclosure needs to be solid, and acoustically dead. The box I constructed is made of 3/4' MDF, which is glued, screwed, caulked, and internally-braced. If you rap your knuckles on it, it feels like a solid block of concrete. So, it doesn't expand and contract as the driver moves, nor does it absorb any of the sound energy put out by the driver. You might guess it would sound much different if it was made out of cardboard from an old shoe box. The OP's enclosure isn't actually there, because the dynamat sealing the holes in that area isn't rigid, and as it moves it's absorbing energy that should be generating sound. That area also isn't sealed, anyway, and you can see one obvious opening around the seatbelt slot. Yes, it's a ported "enclosure", but a proper ported enclosure has a tuned-port, not just a random opening. The tuning of the port is determined by its size (diameter and length) and placement in the enclosure. The devil is always in the details and I'm writing this not to disparage the OP's work, only to point out there is a proper way to do things in this area, and while it may take a different amount of effort, the expense is just about as minimal.

2Cool4Skool

iTrader: (2)

That's incorrect. Look again. The seatbelt slot is sealed with 2 layers of Dynamat with pieces of DVD cases cut up plus extra silicone as I wrote earlier. It may look ugly but it works. It's just like someone else has done before. The entire cubbyhole is sealed. That's why used a flashlight to see if there are any holes as I wrote earlier.

Also, the port is cut to the recommended length. Infinity gave several box volumes and port lengths to go along with each volume. The 2.5 cubic ft is one of 3 setups given as "ideal".

If you look inside, the holes the Dynamat is covering up are not that big and will not flex in the manner you say. The "flex" is insignificant and any degradation of sound quality is so miniscule as to be imperceptible. I know because I listened to this against my properly setup MDF ported box:





The proof is how it sounds. After plugging up all the holes and freeing up some space next to the port, I put the ported box in my trunk and switched back n forth to hear how it sounds. Guess what? It sounds pretty damn good. The drums beats are tight. Bass lines are thumpy and crisp. Low bass notes got that BOOTY BOOM that only a ported setup can deliver at lower power levels. It sounds every bit as good as my ported MDF box. And while listening to my subs back n forth, I wondered what it would sound like with both of them hooked up? Damn. It's sounded so good, i'm going to take that sub out of the MDF box and put it on the other side.

But on the other side, I'll use the "turn your glovebox into a subwoofer" method as few posts down in this forum. Using the glovebox would produce even more flex than the metal subframe but its good enough for that guy (he says it sounds great), its good enough for me. The only difference is that I will be porting that glovebox. As you can see in the pic, I checked the posters claim that its about 1 cubic feet; and sure enough, 1 cubic feet of packing peanuts fit into the glovebox. This is the recommended volume for my other sub for a ported setup. I'll post it when I'm done and post another review of how it sounds.


Now, about your sealed setup, dcains. I've seen your sub box before when I was looking around for the best way to use the cubbyhole. I dismissed it right away for 2 main reasons. 1) It's a sealed design which would require more power to get the same output (that's just a fact) and sound quality. My sub is also not very efficient, (like your JL), so sealed enclosures are out for me. I've already been-there-done-that using my current sub in a sealed box and it just won't work. It would need too much power. And 2) Isn't your sub going to be firing inside the cubbyhole? I don't think a sub box firing inside an enclosed space would sound good. That would require even more power to overcome. How much power are you giving that sub? It's a nice build though. It that was my sub, I'd put it somewhere outside the cubbyhole.

dcains

iTrader: (15)

No offense, and I'm not going to argue with you, simply because you don't know what you're doing. You didn't build a box. Like I said, this has been done a million times in 13+ years, and it just doesn't work like an enclosure. You've installed a "free-air" system, just like the Blose, which is fine if that's what you want. You might like the sound, and that's fine, too.

I'll tell you how you can test it. Temporarily seal the port. Push against the driver, and of the area is completely airtight, you'll feel yourself pushing against the compressed air and the driver will spring back against the pressure. Airtight means no air leaks - even tiny ones, and a solid box. Dynamat, by definition, is compressible and flexible - that's how it absorbs energy. Let's say the enclosure behind the seats wasn't there. Could you build a box out of just Dynamat? No one sells rubber speaker boxes. Perhaps if you had used several layers of fiberglass mat and resin . . . Also been tried, BTW, with failure.

My box is vented out the OEM Blose grille:





Amp isn't very large, JL 250W mono, gain isn't even 1/2 up, and a properly-designed sealed enclosure can be very efficient. The cabin volume of a Z33 is pretty small.

jdmfetish

iTrader: (3)

OP
you would have been better off simply deadening the inside, and going infinite baffle in the stock location

and you still can

the proof in the sound is only that , well your current attempt , does not sound good

Dealsgap

Just installed this in my 08 Touring. It fit perfectly in the stock location and I think the sound is great.

goracerx

Nice, I have the 10" Infinity perfect also in a Zenbox but it rattles the glass bad enough that I think it will shatter if I crank it. I was thinking of switching to your semi free air setup but not ported. My JL is 500w though, so shouldn't be any noticeable power loss.

How did you mount it to the plate? Did you drill holes and use the same screws?
Did you Dynamat the back of the metal mounting plate?

jdmfetish

iTrader: (3)

no you will not shatter the glass ^^

goracerx

Is yours a roadster? Did you pack any cotton sound stuff in the cubby or stick on any sound deadening material to the metal divider, the upper section or the metal plate the sub screws on to?

I still haven't gone past 15 because of the glass rattle. I'm sure it could shatter but so would my ears if I cranked it. I want clean sound and don't care if anyone outside of the car can hear.

2Cool4Skool

iTrader: (2)

Right now, I mounted an Infinity Perfect 10 (non-VQ) to the right side. I drilled holes in the mounting plate and bolted the sub to the plate before installing the entire assembly over closed cell foam insulation. After the assembly has been installed, there will still be a gap on the bottom of the plate. That was filled in with silicone.


I Dynamatted the entire plate on the left side but for the right side, I used a lot less Dynamat. I've since found out that there only needs to be 30% coverage. Any more and it would just be a waste. If I had to do it again, i'd use even less Dynamat. The cross sections on the plate are not very big.

I also have another Zenclosure which I ported & for comparison purposes. Yes, it distorts the glass (460w rms) but I'm not worried about shattering the glass. But then again, I don't "crank it".

The space is approx. 5 cubic feet for the entire area, so yes, it will function as a free-air speaker which the Perfect 10 is designed to do. Keep in mind the sub's RMS is 350 watts max. But for free-air use, the power handling is reduced by 1/2 at 175 watts rms. as recommended by the manufacturer. 500 watts rms is probably too much.

================== Update ============

I tried the "building a sub box using the glovebox" method using the Infinity Perfect 10.1 and it does not work. The volume is correct at about 1 cubic foot, but there's no way the glovebox is stiff enough. I tried to add pieces of wood to the box thinking that if I decreased the cross section of flexible panels that it would be stiff enough, but it did not work.

The amp used is a 300w rms amp. The sound was really "small" and "localized". When I tried to turn up the volume, there was no comparable increase in bass volume. I tried it ported as well as sealed; and either way, it sounded horrible.

So instead, I mounted the sub to another plate and blocked off an area that's approx. 1.7 cubic feet with a 14" long 3" dia port. Instead of using pieces of DVD cases like I did before, I used wood to block off the larger areas and sealed the edges with either silicone or "CLD Tiles" (better than Dynamat).

I used an online sub calculator to get the cubic feet and port size. Different calculators will give different values. Just keep in mind that for any given sub design, there are a range of options that are available. You are not limited to the sizes from the manufacturer.

Before I go into how it sounds, keep in mind that the only way to tell if it "sounds good" is to compare the same sub in a box that already works well. I'm basing my opinions of how well this setup sounds based on a comparison between my installed sub to the ported MDF Q-Logic box shown above. I have a couple other Perfect 10s sitting around, so I can do that.

You can't tell over the internet especially if you've never heard anyone who did this. No one has done this. No one is using the BODY of the car as the enclosure itself. I've seen "false walls" made of Dynamat and plenty of people who stuff an MDF box into the space, but no one has used the BODY of the car as the enclosure.

Test track I use is Lady Gaga's Starstruck.

So right now, the right-side Infinity Perfect 10 sub sounds OK, just OK. Its much better than when it was in the glovebox. The sound is no longer "localized" but is now properly diffuse with musical bass. But for some reason it's still sounds very weak as far as SPL is concerned. It should be louder than the left sub because the Perfect 10 is much more efficient. I believe the enclosure is too big and it functioning closer to a "free-air" design. The next step will be to lower the volume of the enclosure. After lowering the vol. I will probably shorten the port to whatever pops up on the sub calculator.

I now have another box used for comparison. It's a Zenclosure 1.4 cuft ported. I just cut out the middle inside the box. On 1 side, I mounted the sub and the other side where another sub was to be mounted, I installed the port. This setup sounds even better than the 1 cu ft ported box pictured above and will be used for comparison. The bass is a noticeably deeper with the larger 1.4 cu ft.

Knowing that, I'll just lower the volume of the enclosure to approx 1.4 cu ft and shorten the port to the same size as the one on my 1.4 cu ft Zenclosure. I'll probably do this sometime this summer.

Some things I've found out:

• The body of the car in that cubbyhole is plenty stiff enough for a decent subwoofer enclosure. The left-side sounds excellent. I have since replaced the DVD cases with wood to cover the seatbelt area which is also the largest area to be covered. The rest are small sections that are covered with Dynamat or CLD Tiles. The aluminium cover over the fuel pump (directly under the sub) may be a weak point that needs stiffening as it seems to give noticeably if I put pressure on it. But since the left side sounds really good, I'll just leave that alone for now.
  
• Covering large portions of the body with Dynamat is a waste of money and adds unnecessary weight. Dynamat is only to reduce vibrations which is unrelated to most of the noise you hear. 25-30% coverage is enough. Dynamat does little to reduce noise.
  
• CLD Tiles better than Dynamat
  
• This method of using the body as the enclosure requires trial and error and is more labor intensive than using an MDF box. The space is uneven and difficult to measure with accuracy. The only way is to use packing peanuts that come in 1 cu ft bags and start with an estimate. I was lucky on the left side which I got right the first time. The right side needs adjustment.
  
• The OEM thick rubber/felt pads over the fuel pumps work very well at eliminating the whirring noise from the fuel pumps. Since the subs are covering that up, I took out the pads, cut them up and glued them in the door panels for less road noise.... better signal to noise ratio. Thick rubber and felt reduces noise, not Dynamat type material.