DIY: 560SL Rear Side Panel Speaker Enclosures - PeachParts Mercedes-Benz Forum

donbryce · #1 06-27-2009, 08:44 AM

I've been planning this for years, and finally finished putting a pair of 5 1/2" 2-ways in the rear side panels of my SL. I have the 'kinderseat', so floor mounting isn't an option, although I could see putting shallow mounts in the fold-down part....but then I'd have the same problem with floor mounting, which is luggage on top of the speakers. We only use the SL on trips, and that is when I want to both hear the tunes, and have enough space to store our stuff.

Another issue was the irregular shape, contours, of the back side panels. The only available spot is in the triangular area just aft of the wheel wells, and that spot is where the shape makes flat grilles difficult to seat flush. My solution is to do the grilles separate from the speaker mounting boards....but I digress, so on to the DIY.

First steps, of course, were to remove both side panels and examine the layout of what Mercedes stuffed inside those cavities. The passenger side is all wiring harness, so I had to unplug and move some wiring around to clear away the 'sweet spot'.

The driver side is more complicated, because of the 2 big electrical boxes, which are the SRS system voltage converter (large box) and the sensor (small box). In the picture, I show the first attempt to re-arrange these. Unfortunately, after I finished the job and did a test drive, the placement of the large box interfered with the seat belt retractor. I had to disassemble and go back in with a different arrangement....I'll have pictures next post on this.

Anyway, when the areas were cleared away, I spent considerable time making the patterns for the enclosures from cardboard. These were then traced to aluminum sheet, about 1.3mm thick, then cut out with snips and an air tool.

donbryce · #2 06-27-2009, 09:01 AM

As the pictures show, the SRS boxes were moved inside the cavity behind the inner steel panel welded to the wheel well, basically putting the small box on the outer wall with double sided tape (no room to screw it to anything), and the big one sort of where the small one was originally. As I said, this is the only way I could see to allow the seatbelt to operate freely.

I then cut the openings for the speakers, first in the cardboard, then the aluminum (jigsaw), and shaped the aluminum to the enclosures. The critical dimensions for the openings are the depth of the speaker magnets to the wheel wells, and getting them as high as possible.

I made 2 inner pieces as well to complete as near an enclosure as I could. All the aluminum pieces are fastened with sheet metal screws to facilitate easy removal and replacement, which I figure was at least 1/2 dozen times per side to get an exact fit.

donbryce · #3 06-27-2009, 09:09 AM

Continuing on, I then mounted the panels and taped a marker to the cutouts to find the matching centerpoint for the grilles on the side panels. You can just make out the dot on the passenger side panel in the third picture.

I had a problem with the panel on the driver side, which was worn away under the top hatch lever. Someone must have put the lever on in the wrong position and chewed up the vinyl opening and closing the top lid. Luckily, the best spot for the speaker was right over the bad spot on the panel.

This last pic is a bit out of order, as it was taken after I had removed the plastic from the panel and cut the vinyl just prior to wrapping it around for the grill opening...detailed in the next post.

donbryce · #4 06-27-2009, 09:26 AM

I used a nifty little tool recently acquired, a 1 1/4" wood/plastic cutting blade in my air tool to cut out the plastic panel from the backside without touching the vinyl. This was very tricky, as 1 bad cut through to the vinyl on the edge of the opening would ruin the panel. The rough edge was smoothed out with a carbide burr, using a piece of scrap to protect the vinyl.

I then used contact cement to glue the cut vinyl over the openings. The idea here is to produce a stock looking grille, what Mercedes might have done if their engineers had spent as much effort on a sound system in 1986 as they spent on the SRS or other electronics.

At this point, I moved to the woodshop and cut 1/2" plywood to back the mounting of the speakers to the aluminum panels. The first go-round is shown in the last picture, which is the plywood mounted to the backside of the aluminum with double sided carpet tape. After I test mounted the speakers to the frontside of the aluminum, I realized that I'd miscalculated the distance from the tweeter to the inside of the grilles. I had about 1" of space, so decided to make up 2 more plywood pieces to attach to the front of the aluminum and shaped like a wedge to angle the speakers up.

This worked beautifully, and got the speakers angled upward and centered in the openings.

donbryce · #5 06-27-2009, 09:31 AM

Picture 1 is of the driver side panel, outside, and picture 2 is the passenger side panel, inside view. The last 3 show the finished panels and the passenger side speaker in place. Note that the fourth picture was taken before I realized the the SRS boxes needed to be repositioned.

donbryce · #6 06-27-2009, 09:54 AM

One last shot of the driver side speaker in place, and finally, the finished product. A few notes here that aren't in the pictures:

- I used some left over 6"X9" grilles to cut the material for the openings. These were carefully contoured to match the panels at the spot where they mount. Several trips to the store to buy grey paint to match the vinyl later (very, very hard to get a match), and the grilles were contact cemented to the backside of the panels.

- I stuck a pin through the grille holes to get the distance from the tweeter to the grille, and used a hammer to move the aluminum in until there was clearance. No biggie with 5 1/2" speakers, but I wanted to make sure there would be no rattles at high volume.

- The finishing touch is a 1/8" chrome strip (trim tape) around the edge of the openings. I think these look very much like what MB might have done back in the day.

I've done a couple of road tests with the top down, and even driving these off the Blaupunkt head unit, I can actually hear the music at highway speed. The sound is way better at city driving speeds though, and I'd expect a vast improvement if the top was up, or if I had a windscreen (building one of these is another project that I'm definately considering).

Well, this was a lot of work, about 3 1/2 days (OK, I'm retired, and should be working on the house according to SWMBO), but I'm very happy with the end result. I just installed new front dash speakers (4" JL Audio TR400CXI), and have an Infinity Basslink en route for delivery Monday. Today it's out to the garage to fix the Blaupunkt head unit that doesn't want to eject the CD, install the CD changer in the trunk, and put the Thummer in.

GSMITH · #7 06-27-2009, 11:35 AM

Don you do some of the nicest work I've seen.
Looks better than what the factory would have done.

I hope you decide to do the door pods so I can steal your design.

Let us know how the basslink works in the trunk.

dingo joe · #8 01-04-2010, 08:17 PM

A mid winter bump for Don's great thread. What nice work...

donbryce · #9 01-30-2011, 10:42 AM

I had a PM from a fellow member with some questions, so here are the answers for anyone interested.

1) on the inside of the enclosure, I see some black tape. Did you seal all the seams with tape?

No, just over the wiring, to make it neater and keep the wire harness out of the way when removing and putting the speaker baffle in during construction.

2) I also saw some foam padding. Was that only at the edges in contact with wiring or did you use it throughout?

The foam is sticky-back insulation (window draft) tape, about 3/8" wide I think, from the hardware store to fill the irregular gaps where the baffle edge sits against the bodywork. The idea is to seal the air in back of the speaker, in the 'box' or enclosure, from the front, like it would be when mounted on a package shelf or a box. Otherwise, the sound waves from the back will cancel those from the front of the cone. Silicone caulk or something like it would work better, but too messy.

3) Finally, how exactly did you apply the chrome trim? was it wrapped around the inner edge of the circle cut-out with the mesh grill THEN applied with contact cement to the inside of the panel?

The chrome trim comes in a roll and is shaped like a 'U' or 'C' along it's length designed to clip on the edge of a metal panel. I got it at an auto supply place. It has it's own cement IIRC inside the 'C'. If you cut it just right, the ends will meet with no gap and from a short distance it looks like a solid circle. The trim goes on first, then the grille is cemented to the backside, being careful to shape it to the contours and get a tight fit against the part of the trim that rolls around the edge of the hole on the inside.