Restoration of a Sonochorde Senior Reproducer
How Well Can a 90+ Year Old Look and Sing?
I wanted to have one of these great-looking speakers the first time I saw one. They aren't rare or valuable at all, but the styling really caught my eye. The trouble is that 90+ years of exposure seems to cause some trauma. The beautiful fabric that covers the front of this speaker is very thin and fragile. The base is also prone to growing some rust - the rust on this one is rather minor. I've seen many that are far worse than this...
While there was some rust all around the base, the most important feature of the speaker was still intact: the gold "Sonochorde" decal on the back of the speaker. The intact label on the back is the primary reason that I chose to purchase this speaker instead of others I saw. It would be relatively straight forward to remove the rust and with an intact decal, it would look as close to new as possible when I was finished with it.
The easiest part of the disassembly process was to remove the base. It is held to the speaker enclosure with a single bolt that is accessible through a hole in the felt at the bottom of the base. Once removed, the clam-shell base just separates into two halves. The felt from the bottom was just folded in toward the inside where the two pieced of the base join. This felt was worn through in spots, had absorbed some kind of liquid in the past that resulted in rust and was just plain dirty and falling apart. I carefully removed this and tucked it aside to keep as an original part.
The next step was to begin removing the rust. The bottom half of the base was in pretty good shape, just minor spots here and there. I didn't bother much with these since none of it would be visible with the completed speaker. I sanded the heavy stuff off and sealed the rest to keep the air out with some clear lacquer. Since I was unable to find a felt color that matched the replacement fabric that I found (more on this below), I chose a dark brown felt for the base of the speaker. I cut it to size and used a few drops of Elmers glue to hold the felt in place and just fit the top and bottom parts of the base together to hold the felt while the glue dried. I glued opposite edges two at a time, so it took four different applications of glue to put it all together without getting wrinkles in the material. Below is a picture with the top and bottom, and left and right sides glued. Up next were one of the diagonal pairs.
After the bottom was done, I used a fine grain (220 or 330 grit) sanding sponge to begin smoothing out the top of the base. Surprisingly, the damage to the underlying metal was much less than I expected. Most of the uneven contour was old paint that had bubbled up with the rust. Once removed, there was really very little pitting of the metal itself. After stripping the rust and simultaneously trying to preserve as much of the original paint as possible, I gave the base a light coat of clear lacquer to seal it and prevent any further rust from growing. In the few places where the pitting from the rust was deeper, I added a few more coats of lacquer. A light sanding afterward resulted in a finish that was nice and smooth. All metal surfaces, inside and out, were sanded to remove the rust and then cleaned and coated with clear lacquer to help prevent the rust from returning.
Then came the really hard part: finding a paint color that matched the original. This is why I didn't want to completely strip all of the paint. I wanted to have something of the original color so I could match to a new color. I looked high and low for MONTHS before I found something that I was satisfied with. I stopped in at every hardward store, every craft shop, and any other place that might carry paints that could be applied with a spray gun or can. Nothing seemed to match well. I even tried working with lighter and darker shades of spray paint and applying them together. I sprayed the lighter coat first and then while it was still wet, applied a spritzing of the darker color with the hope that they would blend a little bit. They did, but not as nicely as I had hoped. Airbrush paints were even more difficult to find a match and I was less interested in mixing my own colors. Finally, I found a new color on the shelf at the local Michael's craft store one day: Design Master #719 Dark Chocolate paint in satin finish. It is almost a PERFECT match. In direct sunlight, it is just a pinch on the dark side, but the difference is VERY subtle. With indoor lighting, there is no visible difference at all. One or two coats of my new paint and a lacquer layer on top was all that was needed. During reassembly, please note that the cut out for the speaker cord goes in the BACK of the speaker, not the front. This makes the metal pinch the cord so it doesn't damage the inner workings if the cord gets tugged.
After finding such a nice match, I began to work on the rest of metal. The two halves of the upper speaker came apart in clam-shell fashion as well. These two parts were a little more stuck together since they form a rather tight compression fit. There was a little lip at the bottom of the speaker where some of the metal was bent out away from the rest of the speaker. I used a flat bladed screwdriver as a lever between the bent part of the speaker and the bolt that goes into the bottom to hold it all together. This turned out to be the magic step that made it come apart.
So here are the two halves of the speaker itself. What a mess or rust, dust, dirt, and debris. Luckily, this all cleaned up pretty easily as well. The fabric for the speaker just really sits in a little groove and easily lifted right out. The speaker itself, though, presented a little more trouble. The speaker driver itself is made from a very thin wood veneer material. A dust cloth cleaned this off to allow closer inspection.
A thorough scrubbing with a sanding sponge removed all of the rust once the fabric was out of the way. I retained the original felt squares that sit at each vertext of the design and the felt ring that keeps the wooden speaker cone from rattling against the metal case. I sanded down the rust, inspected carefully to make sure it was all gone, and then sealed the raw metal with a coat of lacquer. The felt pieces were then reinstalled with a little dab of Elmer's Glue.
This little nut with a screw in it caused some issues with further disassembly. The paint surface on the disk obviously needed to be redone, but first this metal cap needed to be removed from the driver. The set screw was rather tight, and once removed allowed the nut to wiggle around, but it still wouldn't come off othe metal post in the center. This metal post looks like it was snipped off with wire cutters after the speaker was assembled. The cut left a bur on the post that prevented it from fitting through the hole in the center of the nut. A little work with a fine metal file removed the bur, and I was able to remove the driver from the housing. The brass nut fits with another piece of metal on the inside of the driver cone that, once unscrewed, allowed me to separate the metal pieces from the wooden driver. What a lot of work for such small parts!
All of the metal was sanded and repainted and then reassembled. Below is the back side of the speaker and the preserved decal after the rest of the metal had received a fresh coat of Dark Chocolate paint. A carefully trimmed piece of blue painter's tape protected the name decal during painting. A quick coat of clear lacquer over everything, inside and out, helps to protect the paint. Put a plastic bag over the electro-magnet mechanism of the driver motor before painting anything.
So, half of the work was done: The rust was removed and the paint was fixed.
Arguably one of the most eye-catching features of this speaker is the fabric grill cloth. I am not entirely sure what kind of fabric it is - some have indicated it is a raw silk. Whatever its origin, is is VERY light weight material. If you hold it up to the light, you can see through it, but it is thick enough to hide the surface of the driver behind it.
Not knowing what I was getting into, I began taking this apart as well. It turns out that its construction was more simple than I thought. The fabric is really nothing more than a single piece of rectangular fabric that measures 43.5 inches long by 8 inches wide with a hem sewn into each of the longer sides. The hem takes up 1/2 inch on each side, so the total amount of fabric that you need is 43.5 inches long by 9 inches wide. The two short ends of the rectangle were then sewn together (leaving both hems open) and a string is threaded through the loop created by the hem on each long edge of the fabric. Reconstructing this part turned out to be easier than I thought!
The REAL trick was finding a replacement fabric that would work well. You need to match both the color and the weight of the fabric. Of these two, the weight of the fabric turns out to be the more important dimension to pay attention to (and the hardest to match). If the fabric you choose is too heavy (thick), you won't be able to bunch the fabric up tightly enough in the center. I made of few of these that didn't work out so well before I found a lighter fabric that would allow me to pull the center loop closed tightly enough that the hem was hidden under the button that goes at the center of the fabric. If you are having a hard time finding an appropriate color fabric, you can always start with a lighter color maroon or burgundy and use some RIT fabric dye to daken the color a bit. It won't turn pink into a dark rich color, but the black dye will darken a maroon so that it more closely matches the original color.
So, just cut your fabric, lay it out and pin back the sides to make the hem, run it through a sewing machine and you are half way there. When this step is done, just fold it over, sew a new seam, and thread the string through.
Make sure that your edges are EXACTLY parallel to one another when you sew the fabric. If there are minor variations in the width of your fabric, they will result in puckers in the final speaker that won't look right. I made three of these before I was able to get the fabric to lay flat without puckers... Practice, practice, practice...
Tie a saftety pin at the end of the string to make it easier to thread the string through your hem. You want to use a pretty heavy string here, because you'll need to pull it VERY tightly in order to duplicate the pleats of the original fabric.
When you are finished, just loop the fabric over the metal hoop and insert the fabric into the frame again. If you are lucky, your seam where the two ends of your rectangle were joined will disappear into one of the pleats. All that is left is the little hole for the speaker adjustment rod. I used a razor knife to open part of the seam where the two ends of the rectangle were joined together.
Here it is after about a dozen hours of work, a new-fabric covered cord from JackPine Radio, and months and months of looking for the right fabric and paint color. I'm still not 100% thrilled with the fabric choice (it is still too thick to pleat properly) and when I find something that is thinner and a closer color match, I'll replace the it. In the mean time, it looks much nicer than it did before...