Stereo Overhaul - Mild Documentation

[eduard4us]

After spending some time with the Stealthbox, I decided it wasn't going to cut it. I am keeping it in place, but it will be sitting idle unless we are roadtripping or camping and need all of the trunk space.

One sub in the trunk for most of the year. I chose a Hertz MP 300. It's a dual 4ohm 12". I heard this same sub powered by the Mobridge amp in Fraser's car this summer. I was very impressed.

This will be connected via a Neutrik Speakon connector. Connects securely and disconnects easily. I will have another mounting plate on the rear interior panel that is wired to the Stealthbox. When I need to switch subs, I just move the cable and apply the appropriate DSP tune from the head unit. One tune for the Stealthbox and three I can use with the Hertz sub (for various levels of sub output). Between the two subs, the EQ filters are a little different, the delays are slightly different, and I have some limiting on the sub channel for the JL.

The goal was to maximize enclosure volume (a touch over 1 cubic foot), while minimizing the loss of cargo space. The raised bump behind the rear seats meant an off the shelf slanted box wasn't going to work. Here's what I came up with:

The triangular space behind the sub was just enough for a right angle speakon connector (after recessing the mounting place a bit). I changed the H and W ratio a bit after taking the screenshot above. The final product is a little narrower and taller.

I did not get the angle right on the first try for the upper rear section, so I had to make a change on the fly.

I used 10-32 bolts with threaded inserts recessed into the double baffle. MDF is not a great medium for screws, especially if you have to take them out more than once or twice.

I used wood glue (with brad nails and clamping) for everything except the baffle. I used PL Premium for the final piece. Great stuff, long working time, expands a bit to fill gaps, and machines or scrapes away pretty easily. Just don't get it on yourself... takes ages to get off your skin.

The shape of the box made the final clamping setup a challenge, so a little jig was necessary.

I've never carpeted a sub enclosure before. I think it turned out pretty nice. My wife helped a lot and we watched some youtube videos to get some tips. Parts express for the carpet, 3M Super 77 for the adhesive.

Here's the Speakon connector. It twist-locks into place and exist the tunnel near the amp.

Overall impressions: It is exactly what I was hoping it would be. It sounds as impressive as it models in simulation vs the JL. About 9db in the region that matters. This is with 500w to the Hertz and 400w to the JL.

It now sounds the way I was hoping it would when I started this project. I always knew the sub was going to be the weak spot. I'm glad I didn't settle. And it'll still sounds pretty damn good when the big sub is removed. 10/10 would repeat.

That is some serious work right there!!
Way to go!

How did you find the JL stealth enclosure compared to the OEM?

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[brtd]

The Stealthbox is a huge upgrade over the BO subwoofer. No question. It just wasn't enough to scratch that itch for me.

Everyone who heard the Stealthbox was very confused when I told them it wasn't enough for me.

That is some serious work right there!!
Way to go!

How did you find the JL stealth enclosure compared to the OEM?

 

[Tye]

Great work on this. My understand is JL left a lot of room on the table with the stealth box. Did you ever consider having someone else build you an enclosure in the stock location that could use either a 10tw3 or better sub? If one was willing to put the amp under the rear seat vs on the box, I wonder if there is enough space behind the stock panel to build a larger box.

 

[BlarneyStoned]

@brtd did you have any issues mounting the amp to the stealthbox? I'm working on my install this weekend and did a test fit but my side panel would not go back in because the amp was sticking too far out. It sticks out because at the top right mounting hole the nutsert in back does not have any space to go into and sticks out. Before I go modifying the mounting plate I was hoping I'm just doing something wrong.

Edit: Think I got it figured out, I'll have to drill different holes in the mounting plate to get the amp low enough for the nutserts to fall into the top part of the recess a bit more.

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