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NEW In-Cabin Subwoofer Install Location! Pics!


Old 11-04-2004, 12:52 PM
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Default NEW In-Cabin Subwoofer Install Location! Pics!

Hi all, I found a different spot to locate an in-cabin subwoofer that takes up no useable storage space, and has zero impact on legroom.

THE SUB: JL Audio 6W0
Diameter: 6.5"
Free Air Resonance (Fs): 36.7 Hz
One-way, Linear Excursion (Xmax): 0.3 in
Effective Piston Area (Sd): 20.9 in2
Power Handling (continuous): 75W-100W
Power Handling (maximum): ~150W
Mounting Depth: 3.5 in
Mounting Hole Diameter: 5.625 in
Sealed Enclosure Volume: 0.175 ft3 (5.0 liters)
Driver Displacement: 0.019 ft3 (0.5 litres)

The sub is designed to deliver tight, low frequencies in a sealed or ported chamber. Beyond having great reviews, one of the most significant specs is the minimal volume required for the sealed chamber--about one and a half milk jugs. 5.5 liters including the driver displacement.

The only negative comments I have read are as follows (from people who have not heard them):
*A 6.5" speaker is not a subwoofer, it is a woofer. Dude, you need a 12 or 15" sub to hit low...(Mostly from guys in Camaros.) Fact: That's a myth. The frequency a speaker delivers has more to do with speaker design than to do with diameter (to a point, of course...).

*Well, no way a 6.5" sub would be loud enough
Fact 1: This could be true, depending on your needs. To make a lot of noise you need a lot of "piston" area (and displacement volume) to essentially move a lot of air. But better bass can often be achieved with a single or multiple, tight, smaller subwoofers than a single sloppy giant sub.
Fact 2: A trunk sub (or subS) needs to be loud to be heard inside the cabin. A sub in your lap does not need to be as loud as a sub in your trunk.
Fact 3: Musicality and loudness are different things entirely. If you are into sound-offs, you might take a different approach.

I had purchased a 6W0 and intended to install it in the passenger footwell ala MODIFRY or GamecockS2K/S2Kmugen, or some combination of the two. I really liked the creative use of space in these installs!

A more serious cut and paste to get a bigger sub deeper in the cabin (cut through the floor) was done by ws2000. Not for the faint of heart...


I had an aversion to cutting steel, and I really didn't want to lose ANY footspace (I have tall friends, and sometimes losing toespace is worse than losing legroom--since you can't orient your feet right unless you sit like an Egyptian...).

The passenger footwell presents a challenge because there is already a huge mechanical contraption down there...the A/C unit. So, I was going to remove the styrofoam footwedge and try to make a very creatively-shaped multichamber fiberglass box for the passenger footwell. Then I started poking around in the driver's footwell.

The place I found is actually in the driver cockpit, under the dash. It turns out there is a relatively HUGE (ah... in S2000 terms...) space up under the dash. Beyond that, there is hardly anything in the foreleg area, providing a location to build down from the dash as well.

To get an idea of the volume available sit in your car in the driving position. Now wave your hand around down by your forelegs (the part of your leg between your knee and your ankle.) See how much space is available? I'm 6' tall and can make my knees hit the dash, or the cowling uunder the steering wheel, or the wheel itself. But try as I might I cannot make my forelegs hit anything up under the dash.

Now look over at the passenger footwell. See how much of that space is occupied?

The challenge was creating a rigid shape that A) utilized the space, and B) could be put in and taken out of the space (it has to kind of be rotated up into there...)

There are two small relay blocks that need to be relocated from the right side of the steering column, but that is a piece of cake. Also I temporarily removed the black plastic footwell heater vent (revealing the magic Honda subwoofer mount hole...).

Speaker Testfit:

MAKE A PLUG (this will be the shape of the completed chamber)
I tried to make a "plug" of the space up there by spraying Great Stuff expanding foam into a plastic bag. I made a mess and completely failed. It would have been great to have the car upside down for never have a good rollover when you need one...

I ended up building a shape piece by piece with styrofoam and tape. Very laborious--tape a chunk on, test fit, look to where I could add more, tape a chunk on, test fit...and on and on and on. My girlfriend thought I was nuts (You are doing what?).

I had to be careful to not cover up the most import thing under the dash, the fusebox.

Once I had a rigid shape, I tested the volume of the tape and styrofoam monstrosity by putting it in a plastic bag and submerging in a full-to-the-brim 5 gallon bucket of water. The water that dumps out exactly represents the volume of the shape. I simply measured the volume of water it took to refill the bucket to the brim. 2.5 gallons, should be fine when I need only 1.5 gallons internally, right? (not quite, I found out later.)

Then I made a mold of the shape by putting it in a cardboard box and filling the box with expanding foam. When the foam cured I ripped the "plug" shape out of the mold.

"Plug" with Mold: The plug is in approximately the same vertical angle as installed, the whole thing is obviously angled to the right.

With the mold available, I coated it with foil, sprayed an imaginary release agent (that didn't work in the least...) and started layering with fiberglass to build a shell. After a couple of layers I took the shell out of the mold to make it easier to work with...

Folowing GamecockS2Ks lead, I cut a 2" section of 6" ABS pipe to make a rigid, flat mounting surface for the sub driver itself (He used part of a 6" PVC coupling). After a lot of test fitting I "glassed" in the pipe and continued adding layers.

This was actually a very difficult step. The chamber shape is completely ridiculously amorphous, but ends up fitting under the dash in a single orientation. The challenge here was to put the pipe in so that the final speaker orientation would be correct (i.e. slightly angled towards the cabin and not tilting one way or another.) Another challenge was basically suspending this pipe in the air using wet fiberglass...(Lots of cussing at this step.)

Fiberglass Testfit: You can see the mounting "pipe" and the attachment bolt. You can also see how I tried to shape around the fusebox.

From the Back:

Testfit from floor level: Remember your eyes will never be this low...!

Testfit from passenger angle: Actually lower than passenger eyelevel.

Testfit from left side:

This is one of the most overlooked steps in building a sub chamber. Fortunately I had read that before I got to this point...Got to get the electrons in to make the speaker work...

I added RadioShack three-way binding posts. Again, I wanted to minimize loss of volume on the inside of the chamber. I drilled two holes, threaded the posts into the holes, secured them permanently with resin. I attached 12g wire leads on the inside with spades to connect to the speaker terminals later.

It just so happens that hanging off the steering shaft carrier bearing is the perfect hole for attaching a sub. Solid steel. This is the place where the footwell heater vent attaches with a plastic plug. I used resin to secure a bracket with a nut. Later I would screw a bolt through the hole on the shaft, directly into the nut on the chamber. The heater vent I would deal with later.

Some people do this with MDF or plywood. I still was volume conscious and decided to continue with fiberglass--strength, with minimal thickness.

I formed a lip with clay, then built fiberglass over the clay lip. When, dry, I removed the clay and fiberglassed the remaining gap.

After a detour, I used Bondo to make a more finished surface for the visible part that stuck out from under the dash.

(My detour: When I did a volume check on the covered chamber I was 0.5 liter short, so I had to build an appendage to get more volume...)

I had gotten resin and bondo on the pipe surface (a smarter person might have protected it in the first place...) so I used an inverted router bit in my drill to clean it off and re-square it.

I chose a Krylon spray-on black rubber coating. I could have used vinyl I guess.

I attached the leads to the terminals and wrapped the wire in polyfill to prevent rattles. I used a small amount of silicon caulk to seal the mount (JL's are treated to resist the fumes) and screwed the speaker to the chamber.

The next few images have the brightness tweaked so we can see stuff. Please don't mind the wires, I had run temporary wires with the amp in the passenger seat for tuning. That is all cleaned up now.

From the Right:

From the Right Higher up: It just disappears at normal eye level.

From the drivers seat, below steering level: The binding posts are accessible through the removable panel.

If I get a chance I will take a picture with my feet on the pedals. It's hard to tell but the chamber does not interfere with pedal operation in any way. (I think I cannot even touch it if I try.)

It sounds very, very nice. I use an XTANT 403a three-channel amp. The sub channel outputs 100W RMS. A wonderful feature of this amp is that it has adjustable INPUT sensitivity. Alpine HUs are known to undervolt the sub OUT. I can provide a 10dB boost this to get more headroom out of the amp (it's kind of a "pre-gain.)

Modern Alpine HU's (I have the 9833) have a subwoofer output/phase control available with one push of the volume knob. Most people need to use this at its max setting of 15. I listen from around 2 (want musicality) to 12+ (want thump, or higher speeds with top down). I set the crossovers to blend with my Polk components, adjusted time correction for the sub location and away we go.

With the sub essentially in my lap, the max volume is far more than I need.

I am still doing some RTA work to make fine adjustments, but I really enjoy the sound! It made a huge difference.

The sub is barely visible and I cannot make my body contact it in any way. Aside from some cosmetic imperfections which I can take care of later, I think it came out quite nicely. You can't tell it's there from the passenger seat, which has the best angle to look at it.

There is an unquantified risk with this setup--safety. The box is well-secured so it will never end up on the pedals. But this is a solid feature IN THE COCKPIT where there was space before. The S2000 is nearly perfectly designed to protect the driver in a collision, and I have made an alteration. In a major collision the chamber could do two things: 1) Shatter my tibias to toothpicks, or 2) Absorb energy and protect me. I don't know which, but I wanted others to be aware of this in case they decide to try it. For this reason (and weight) I will probably remove it for track days. And I will try to avoid head-ons.

I took pictures during the install and fabrication (this was my first time working with fiberglass). I will post them as soon as I get them uploaded. I'm a little embarrassed that the current semi-final box has some visible imperfections. I'll try to get over that...
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Old 11-04-2004, 01:30 PM
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Wow! Pictures Pictures Pictures!

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Old 11-05-2004, 05:14 AM
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Yes pictures pictures. I want to see this.
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Old 11-08-2004, 07:24 PM
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ooo pictures please!
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Old 11-08-2004, 08:05 PM
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Old 11-08-2004, 08:34 PM
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Ok we're still waiting.... :tapsfingersontable:

Still waiting..... come on already.... DO IT!! GO AHEAD.. DO IT!! Post 'm up..

Us electronic junkies don't really care what the thing looks like, as all of us that started messing with ICE know that most of learning comes from trial and error so don't worry about what it looks like... if your new to fiberglass and working with it, SO WHAT! at least you gave it a try... most people won't even try it

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Old 11-09-2004, 01:08 PM
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Sounds interesting.

How about some pics?
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Old 11-09-2004, 08:14 PM
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I added some in-progress photos that I had on my laptop. I just pasted them into the original post.

I'll put the "finished" photos up later--they are still on my camera.

Let me know if you get red x's.

I might need some help later to make the image links more permanent--anybody got space to spare?

Thanks for your patience!
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Old 11-09-2004, 08:43 PM
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all i see are red x's... if you send them to me i'll host them
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Old 11-10-2004, 01:06 AM
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Originally Posted by ideugene,Nov 9 2004, 08:43 PM
all i see are red x's... if you send them to me i'll host them
Okay, thanks. Would you mind PMing your email?

Or else, you might be able to get them directly if you go to the link below.

I'll keep trying, but if anyone wants to look or download they can go here while we figure things out:

Subwoofer Pictures

Yahoo is making me jump through some miserable hoops to link photos...
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