Measured the enclosure size behind seats

[nadaclue]

In preparation for some new 6.5" subs that I want to try out, I have been calculating the size of the factory enclosure behind the seats. What I had previously read was that they are around 10L in volume, but this seems to be off by a large amount.

What I did was remove the foam liner that is inside the enclosure, I have the 10 speaker system. I then fabricated a front piece out of cardboard and taped it onto the face of the foam liner thereby creating an exact "box" of what the enclosure behind the seat would be with the metal faceplate on. Then I filled this up through the hole in the top with sand and kept filling / vibrating until I couldn't get anymore sand into the foam liner. Then I simply dumped the sand out and measured the volume of the sand. I won't be putting the foam liner back in but will be using a dynamat type product so I felt that the slight difference in thickness, and therefore volume, of the foam versus the deadener would be negligible.

Doing this I came to a volume of 328.5 in^3, or roughly 5.4L. This is much smaller than the 10L I had assumed I had to work with, per the old standard post from GV:

"The rear Carver woofers are accommodated in the partition behind the seats. The resonance
volume is approx.10 l."

http://www.zpost.com/forums/showthread.php?t=63030

Once I calculated displacement of the sub I will be using, I was left with 4.1L of volume. Not a whole lot.

Also, the factory enclosure seems to be crudely ported into the nether world with a square cut into the top. It may be that the factory subs actually act as free-air subs, there doesn't seem to be a secondary enclosure on the other side of this hole. There's also a lot of other random holes and seams that are not sealed. This may be what is contributing to the muddy bass that is prevalent in this system.

Once I get everything built and wired up I'll put a different post up detailing what I did, but I figured knowing the actual size of the enclosure behind the seats might save some people some trouble.

[santov]

Looking forward to the results. I'm too scared to take apart anything in the rear console. I'd like to get some dynamat in there.

You doing anything with the door or kick drivers?

Take lotsa pics!

[HaiDef]

im so happy there are a few audiophiles in the z4 forum. Music brings tears to my eyes

[gferil]

OP, great job! I was wondering the same thing myself, when I read that same post you linked, my first thought was: can I really fill that small volume back there with about 5 2 liters of soda?

Anyways, looking forward to your finished project, a rear woofer upgrade is definitely in the works for me!

[elerner61]

I knew they weren't 10l !!!! (maybe the OP mean 10l combined?).

Great work, and thanks! Very interested in seeing what you do for drivers.

[antennahead]

I also thought the volume was 10L "combined", which would be closer to your measurements.

[vicj]

Originally Posted by nadaclue

In preparation for some new 6.5" subs that I want to try out, I have been calculating the size of the factory enclosure behind the seats. What I had previously read was that they are around 10L in volume, but this seems to be off by a large amount.

What I did was remove the foam liner that is inside the enclosure, I have the 10 speaker system. I then fabricated a front piece out of cardboard and taped it onto the face of the foam liner thereby creating an exact "box" of what the enclosure behind the seat would be with the metal faceplate on. Then I filled this up through the hole in the top with sand and kept filling / vibrating until I couldn't get anymore sand into the foam liner. Then I simply dumped the sand out and measured the volume of the sand. I won't be putting the foam liner back in but will be using a dynamat type product so I felt that the slight difference in thickness, and therefore volume, of the foam versus the deadener would be negligible.

Doing this I came to a volume of 328.5 in^3, or roughly 5.4L. This is much smaller than the 10L I had assumed I had to work with, per the old standard post from GV:

"The rear Carver woofers are accommodated in the partition behind the seats. The resonance
volume is approx.10 l."

http://www.zpost.com/forums/showthread.php?t=63030

Once I calculated displacement of the sub I will be using, I was left with 4.1L of volume. Not a whole lot.

Also, the factory enclosure seems to be crudely ported into the nether world with a square cut into the top. It may be that the factory subs actually act as free-air subs, there doesn't seem to be a secondary enclosure on the other side of this hole. There's also a lot of other random holes and seams that are not sealed. This may be what is contributing to the muddy bass that is prevalent in this system.

Once I get everything built and wired up I'll put a different post up detailing what I did, but I figured knowing the actual size of the enclosure behind the seats might save some people some trouble.

Hmmm. Are you absolutely SURE those "ports" at the top don't just empty into another sealed chamber?? When I shoved my boroscope up there, I could not find any way out. I test fit in a set of JL W6-v3 8-inch subs on a board and ran two hundred watts into each. Sounded GREAT...and they want about 8.9 liters each. I was going to show it all off once I got them fiberglassed in cosmetically correct. I think the output issue is that original poster is wrong about the crossover point. I believe the factory set up crosses those subs down closer to 65hz than 150.

[nadaclue]

Unfortunately I don't have a borescope, but when I stuck my hand up there I felt what I thought were the roll-over bars that are underneath the plastic covers. I assumed that meant they emptied into free air. Anybody have a decent photo of a race car with all the plastic crap pulled off in the back? I started to do it the other day and couldn't figure out how to get to the bolt located underneath the seat belt holder. Plus it was hot in the garage and I was pissed.

I actually took tomorrow off from work to do some work on the sub replacements / false trunk floor (and I needed a day off) so I'll dig into it more. I sealed all the seams and random holes 2 days ago with silicone to try and seal it up the best I could. I would be really happy if they are sealed chambers, then I could run ported and get more volume.

How far out do those JL 8's stick stick out? My first goal was to go 8", but I was worried about chamber volume and found some really intersting 6.5" subs that just came out that I wanted to play with. Once I get everything wired up, switching subs will just be a matter of switching out new wooden baffles.

Are you using the factory setup for the rest of the system? The x-over points have been something I've been wondering (and worried) about, I was contemplating making a test tone CD tonight to try and figure out where everything is crossed at.

What I need to do is just say eff it and rip all the bmw crap out and start completely from scratch.

[nadaclue]

Found this, seems to be an actual BMW document on the E85 stereo system:

http://www.unofficialbmw.com/images/...unications.pdf

They again say 10L resonance volume for the rear subs.

[vicj]

Originally Posted by nadaclue

Unfortunately I don't have a borescope, but when I stuck my hand up there I felt what I thought were the roll-over bars that are underneath the plastic covers. I assumed that meant they emptied into free air. Anybody have a decent photo of a race car with all the plastic crap pulled off in the back? I started to do it the other day and couldn't figure out how to get to the bolt located underneath the seat belt holder. Plus it was hot in the garage and I was pissed.

I actually took tomorrow off from work to do some work on the sub replacements / false trunk floor (and I needed a day off) so I'll dig into it more. I sealed all the seams and random holes 2 days ago with silicone to try and seal it up the best I could. I would be really happy if they are sealed chambers, then I could run ported and get more volume.

How far out do those JL 8's stick stick out? My first goal was to go 8", but I was worried about chamber volume and found some really intersting 6.5" subs that just came out that I wanted to play with. Once I get everything wired up, switching subs will just be a matter of switching out new wooden baffles.

Are you using the factory setup for the rest of the system? The x-over points have been something I've been wondering (and worried) about, I was contemplating making a test tone CD tonight to try and figure out where everything is crossed at.

What I need to do is just say eff it and rip all the bmw crap out and start completely from scratch.

I assume you're asking how far out in FRONT the eight inch woofers stick out? Obviously, with a three quarter inch board, then the mounting height of the woofer, there is no way to use the factory cover any longer.

I'd say a good full inch, it sticks out. I'm trying to come up with something cosmetically pleasing, and something that won't impede the seats. Unfortunately, Glassing is NOT my specialty! LOL.

[elerner61]

Originally Posted by nadaclue

Then I filled this up through the hole in the top with sand and kept filling / vibrating until I couldn't get anymore sand into the foam liner.

Resurrecting this, as I am just at the point of purchasing subs, what hole in the top did you use? From reading posts, many have said the sub enclosure is sealed. Is this not the case and it is ported into the trunk or some other cavity?

[MHeavNC]

Originally Posted by elerner61

Resurrecting this, as I am just at the point of purchasing subs, what hole in the top did you use? From reading posts, many have said the sub enclosure is sealed. Is this not the case and it is ported into the trunk or some other cavity?

They are ported to each other.. I proved this by unhooking one of the subs and playing some DJ Magic Mike.. When the bass would drop the one sub would hit, and the other would move from the air pushing from it...

[elerner61]

Hmmm that's kinda freaky. so assuming you're running a sub in each enclosure would that make it a sealed system with each sub enclosure having a capacity of roughly 5 liters plus 1/2 of the "port" running between them?

I just ordered a JL 6W3V3-4 to see if I can "custom fit" it into the stock location. Some plastic nipping of the inside of the stock grille is definitely in order. It'll be interesting to see how only one sounds (and to see if I can make it fit)

[antennahead]

Originally Posted by elerner61

Hmmm that's kinda freaky. so assuming you're running a sub in each enclosure would that make it a sealed system with each sub enclosure having a capacity of roughly 5 liters plus 1/2 of the "port" running between them?

I just ordered a JL 6W3V3-4 to see if I can "custom fit" it into the stock location. Some plastic nipping of the inside of the stock grille is definitely in order. It'll be interesting to see how only one sounds (and to see if I can make it fit)

That was my understanding as well. It's a sealed system with the opening between the two enclosures being connected, effectively making the total capacity larger to fit the volume needed by the two Carver subs. I remember reading that another Z4 owner made a new baffle and front mounted these JLs and they fit, but as you state he had to shave some of the backside of the factory grill to get it to fit properly.

[gferil]

Originally Posted by elerner61

Hmmm that's kinda freaky. so assuming you're running a sub in each enclosure would that make it a sealed system with each sub enclosure having a capacity of roughly 5 liters plus 1/2 of the "port" running between them?

I just ordered a JL 6W3V3-4 to see if I can "custom fit" it into the stock location. Some plastic nipping of the inside of the stock grille is definitely in order. It'll be interesting to see how only one sounds (and to see if I can make it fit)

Definitely keep us updated on how this turns out! I've been looking at those same drivers and using one of the small JL 2ch amps to power them, and an adjustable LOC to help level out the signal from the stock amp. I don't need mirror rattling bass but I just want some cleaner bass in the system.

[elerner61]

Originally Posted by gferil

I don't need mirror rattling bass but I just want some cleaner bass in the system.

Exactly what I'm going for. I only ordered one to check fitment and to see if one sub is enough. However, I just spent 5 minutes on the phone with JL tech support.

They said that .35 cubic feet (approximately 10 liters, total enclosure space for both subs) will be too big an enclosure for only one sub. I'd have to seal off one of the ports. They also said that one sub will probably not be enough. I commented to the guy my goal (not looking for thump in my trunk!) and he said "I'm no youngster either, but from my experience you'll want 2 of these subs."

So, my next steps are:

- Fit sub into existing enclosure(It will be really nice if I can get the stock grill to fit)
- If sub fits, close off one port and test
- Celebrate, or order one more sub.

[strokeZ]

While I fully agree about not having bone jarring mirror rattling bass - I could not find any other way to overcome road noise with the top down at 70mph and still hear decent low end. My solution was power and trunk thump. It works but I hate the idea of the extra weight so if anyone comes up with a novel solution I would be all ears (no pun intended)

[elerner61]

This is a little long, but please read. I could use some advice (at the very bottom) .

Revisiting this. As I had recounted in another thread on my system I was able to fit the JL 6.5" drivers into the sub enclosures. I kept the port between the two enclosures open, assuming the two drivers would work against each other as they are in-phase. I had the JBL MS-8 DSP controlling all 8 drivers (tweets, mids, mid-bass, subs) and was happy with how it all sounded. Early on I added some fiber fill to the sub enclosures to soften them up as I thought they sounded somewhat "metallic" at times (even though I had lined them with some Brown Bread dampening).

Over time though, I noticed that my mid-bass was lacking (somewhat common with MS-8 systems that have subs) and for the past two weeks I've reconfigured my system to not have the MS-8 control the sub (signal for sub is a split off from the mid-bass aft of the MS-8) and use the amplifier's crossovers to manage the sub to mid-bass crossover.

On the plus side, I've got my mid-bass back and the system overall sounds better. On the minus side I'm not as happy with how the subs sound now and since I no longer have any subsonic filtering (used to be controlled by the MS-8, and my amp doesn't have a subsonic filter) I've got some below 30hz "action" I may need to use a passive in-line filter to take care of.

So, here is my question: do you think having the ports open between the two sub enclosures is the right way to go? Each of the JL 6.5" subs calls for roughly a 5 liter enclosure. Keeping the ports open on the enclosures enables the compression of air between both enclosures and I'm wondering if this is not the right way to go. I'm thinking of closing off the ports to provide a more controlled environment and seeing how that works. This is my first foray into subs, I've never built and tuned an enclosure.

Thoughts?

[antennahead]

Cut a piece of plastic large enough to cover the hole, and affix it with some 3M automotive double sided peel and stick adhesive........ easily removable if it doesn't improve the sound for you.