This past summer I bought two 371 systems, both in pretty rotten shape. I’m going to do a total restoration on both of them in the coming months. I will keep one system and the other will be sold to some die hard Acoustic Control Corp gear head who wants a brand new 371. For each system everything will be photo documented and I’ll include the system’s entire story, schematics, owner’s manual, photos, parts invoices, etc. in a 3 ring binder (I’m doing this for all my restoration amp projects).

First, the handles get totally cleaned up and re-painted. I did the handles for all my amps and cabinets at the same time. Gawd, did this take a lot of elbow grease, paint remover, wire brushing and an entire f-ing weekend. But they look spectacular now. And, I will take more care when rebuilding these systems than the factory did as they rushed them through the assembly line.

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Then Misty and I get a look and a good sniff at the first 301 cabinet. It is ratty, smelly, rusted, banged up and dirty as hell.

The Cerwin Vega C-187 is wrecked, so it’s getting a new cone. I cleaned and protected the voice coil gap in the magnet with tape before I started scraping. This also took quite a while but it’s done and looks great. By the way, Goo Gone is great stuff.

The 301 cabinet gets torn down to it’s raw state. I also removed the blue Formica panel, polished it with a random orbital machine, #3 polish and a waxed it with a microfiber cloth. Then wrapped it in cling wrap so it would stay nice and pretty until I’m ready to re-apply it. This cabinet will get a full sanding, flat black paint on the entire interior, new Tolex on the exterior and brand new hardware all around.

And now I am ready to start sanding, wrapping, glueing, screwing, bolting, wiring and soldering. Unfortunately, I forgot to include the fresh grill covers and the brand new white T molding in this photo.

The bottom of this cabinet has taken a real beating throughout it’s life. It must have been through hundreds of gigs and there are probably some amazing stories behind all this wear and tear. The pervious owner said he bought it used from a store in Nashville. Thats one busy musical town for sure.

Even though I’ve never tackled something like this before I’m willing to take a shot at it (I’m no carpenter, I’m a musician and an electronics gear head). Anyway, I guess it’s just a labor of love.

Minwax wood filler (aka Bondo) is applied to all the mashed up edges. I filled in every little ding, scrape or chipped screw hole. After it dries, the areas are sanded and another layer of Bondo is applied. This stuff is great and dries as hard as a rock (no wonder they use it in auto body shops). BTW, the brick is holding down a small delaminated section of plywood while the wood glue is drying.
For those of you who might not notice, this photo is of the bottom of the cabinet. The top is in perfect condition. If I had to design a new cabinet like this, I would make the bottom out of something indestructible and add nylon glides to protect the finish.

And here it is, fully sanded down. Although it still appears rough, if you shut your eyes and run your hand along the edges, they feel very smooth and they blend right into the plywood.

Although the dado joints in the bottom of the cabinet are still strong, aluminum angle brackets were fabricated and installed on either side to add even more strength. These ought to hold for another 40 years. 

After hours and hours of power sanding, scraping, fabricating and bolting, the cabinet is ready for internal paint and external Tolex. A factory worker hit the interior with some black spray paint but it must have been a Friday afternoon because (s)he missed some areas and over-sprayed others. So, I sanded every internal surface, every bump and every edge to a nice smooth finish and then wiped the whole cabinet down both inside and out. It’s now perfectly clean.

From the rear view, I’ve painted the speaker baffle and it’s interior. Some might ask “why bother?”. The answer is that I’m restoring this cabinet to “better than new condition” simply because I want to own the best Acoustic 301 bass cabinet on the planet. Alternately, this whole system might be sold to some well deserving Acoustic gear head, as mentioned above.

Anyway, all of the areas that are going to be covered by Tolex are left with raw, exposed wood. Note the protruding wood staples on the center back panel. Nothing I can do about them.

Here is a front view. Even the bolt holes were painted (with a Q-Tip). When that Cerwin Vega woofer is in there loudly barking from all the 370’s raw power, the acoustic waves are going to slide out of this cabinet in perfect harmony. Notice the painted interior of the amp cabinet. I couldn’t just paint the speaker cabinet interior and neglect the amp cabinet, could I?

And now the 370 head appears, it’s cabinet covered in new Tolex and the front and back panels have been cleaned and shined. There are new corners, new feet, new screws, new bolts, new volume and tone knobs and a freshly re-painted handle, all ready for assembly.

Tada! Good as new (even smells new). The amp’s got a new 15 foot, flexible, grounded power cord and a new 6 foot, 12 gage speaker cable with Neutrik connectors. I also disconnected the Death Capacitor so nobody’s going to come to a shocking conclusion. I bought this amp in the summer of 2013 and had not even bothered to plug it in and try it out. Today I did just that. I hit the power, and as is typical with these powerful acoustic amps, I got a nice, loud “THUD” (caused by the rapid charging of the output AC coupling capacitor), followed by the blissful sound of the strings of my Fender Strat (I don’t own a bass guitar at the moment). I was ready to replace all the capacitors but the amp is clean and quiet. So, I’m going to go get me a bass guitar and wail away for a while. I’m playing through my other 301 cabinet that has yet to be restored. And no, these photos have not been retouched in any way.

​I’d like to point out one funny but subtle detail. Notice the position of the volume control is set for “2”. This amp is so loud that any setting higher than “2” will cause cracks to appear in the house’s foundation. I know the Acoustic guys are probably laughing because being “LOUD” is the single most common thing that people notice about these amps. I imagine that if I cranked it all the way up to “10”, I could probably force a change in the weather in northern New Jersey, ha! 

Now, a brief interlude before I cover the 301 speaker cabinet with Tolex.

When I purchased the 301 cabinet, I conversed with the seller via email. The last thing I wrote to him was this: “As for testing it, I’ll take your word that the speaker works and doesn’t have any buzz due to past overloads, damaged cone, spider, surround, etc., right?”. And his reply: “Speaker is in great shape. I hate letting this thing go”.

Nice! And as you saw from the sniff test photo above, the speaker is wrecked. Now, I could have brought it back and got my money back. But, he claimed that “it sounded nice and smooth” but he never had the volume above “3”. At this level, it is quite possible that the speaker sounded fine. Any higher and it would have been obvious how bad it was. And, he never had the back access panel off so I’m giving him the benefit of the doubt. Anyhow, after briefly feeling like I’d been duped (let the buyer beware), I decided to keep it and turn it into an opportunity to really bring something back to life. And so, this restoration story has some real highs and lows to be told. I’m learning a lot from the process and all is good.

Here is a close up of the damaged surround (the “surround” is made of foam rubber and it breaks up and dissolves after about 15 years). And take a look at the wrinkled cone. The wrinkles are caused by asymmetrical flexing of the cone. This flexing is due to the damaged surround not being able to support the cone equally around it’s circumference. Also notice the black spray paint seemingly fired off at random. That bugs me but will be a thing of the past when I get done with it.

Here is the over-heated voice coil. The whitish discoloration is from too many late night overloads probably dating back to the 1970’s.

This is what the new voice coil looks like for comparison. I’ll mount and glue this cone and coil into the speaker frame after the 301 cabinet is done. Notice the dual set of lead-in wires on the old cone. I’ve never seen this before. The new one has very thick single wires. Nice!

Getting started on the application of Tolex to the 301 cabinet. I laid out a 4×8 sheet of masonite on top of plywood for a work surface.

A back view of the 301, about 25% into the process, starting with the bottom. Inside the woofer enclosure you can see the glint of a few staple heads. Impossible to get paint on them. Will anybody other than me even care?

Cutting all the Tolex out of the bolt holes. All in all, 46 holes had to be cleared including the holes for the foot cups, both sides of the back panel, casters, 1/4″ jack and a single rubber foot.

The top and bottom for the 301 are done. Now the right side gets Tolex. It was quite a job for two of us to get this piece on and wrapped around some of the edges. Thanks to my wife Kathy (an awesome artist who’s work will make an appearance later on in this project). One per weekend day is enough for me. Whew!

The Tolex is wrapped and glued on all the openings, both front and back. I’ll work on and glue the complicated seams and 45˚ corners after the large surface dries. And darn it all, as I’m sure you’ve noticed, those pesky wood staples jump right out when using the cameras flash.

The glue that is being used is True-Glu from Mojotone.com. This is great stuff. Instead of spraying it on from a can (and having to use a respirator), this stuff is applied with a paint brush. It has the consistency of skim milk and if you’re not careful, it will splatter all over the place. Using a brush gives you more control as to where you want the glue. It’s applied just like contact cement by spreading it on both surfaces and waiting until it partially dries. Then you press the materials together and use a roller to make sure there are no air bubbles and a heat gun to set the Tolex around all the hard edges. I’ve been worrying what would happen if I screwed up something. So, I did an experiment where I glued some Tolex to a piece of wood and let it sit overnight. Then I peeled it off (with great effort), put fresh glue on top of the old dried stuff and it held just as well. So, if I every had to re-do a piece, I know that I don’t have to sand down the whole area and first.

 Notice that all the inside corners and edges are painted black so that any mismatching edge of Tolex doesn’t reveal bare wood. I’ll have to go over it one more time with a fine paint brush after the glue dries.

I found myself listening to Close to the Edge by Yes as I worked on the cabinet yesterday. It brought me right back to the 70’s. Right back to guitars, amps and electronic projects that got me started in the world of music, live sound and lighting. Ah, those were the days. And it’s seems that I’m reliving them now.

Ok, back to the project:

A 5 foot sheet of Tolex is cut and marked for glue areas. The cabinet has blue tape for masking and to identify points for positioning the material. It takes two people to put these large panels on. One to hold the Tolex and one to wrap it and roller it. Thanks to my friend Phil (an awesome guitar player) who took time out of his weekend to help me. Yep, those are his feet off to the right of the photo.

Once the sides are fixed and dried, the corners are done. They are complicated and require patience.

White T-molding is installed. I used a heat gun to soften up the 90˚ inside corners and a hammer to pound the molding flat. Then most of the hardware was installed including the casters, corners, handles, speaker grill attachment pads and foot cups. Thanks to Pirk (search on this forum) for the new foot cups. They are perfect. 

Cerwin Vega C-187 assembly, ready for re-cone work.

The cone is set in the frame and temporary shims are installed inside the voice-coil to keep it centered. The spider and surround are glued to the frame. I won’t need the edge mounts since the woofer will lay in front of the baffle. However, they are perfect for applying pressure to the glued surfaces. A heavy board was laid on top of the woofer for a couple of hours to get a firm attachment of the surround to the frame. Wax paper prevents the edge mounts from soaking up glue and getting stuck.

A mid-day inspection by Jasmine before I was allowed to proceed. She really get’s into her work. What about those ripples in the Tolex? Nope. It’s the grain of the plywood telegraphing through the Tolex. Nothing I can do about it. Suffice to say that the Tolex is as tight as a drum, all over this cabinet.

Like the tribal details? Thanks to my artistic wife, Kathy. This was tedious work and took most of the day to sketch and paint. I know, nobody’s going to see them. But, this artwork is there to enhance the flow of acoustic waves through the system.

Now for a first test of the woofer before battening down the hatches. This thing is a monster. It weighs around 35lbs. And, it sounded quite nice just sitting there in free air. Notice that I doubled up on the connections and used 12 gage copper cable. You can never have too much conductivity when driving a woofer this big.

Woofer installed. It then seemed obvious that the art work looks like sound waves emanating outwards. I didn’t foresee this fortuitous result.

And now the completed Acoustic 371 system makes her debut. I’m going to enjoy playing through this baby. And I’ve got a couple of ideas to non-destructively (so that it retains it’s original configuration) increase it’s frequency range to satisfy today’s 5 and 6 string instruments, including my Chapman Stick. I’ll reveal those ideas in a forthcoming thread.

Some of you may have noticed that the kick plate is absent. Well, it’s at the shop down the street getting bent at a 45˚ angle. I just couldn’t do it with my vice. Once I re-install it, I will re-attach the manufacturer’s serial number plate.

Roll credits:

Materials used for this restoration project:
Tolex, Tru-Glue, chrome corners:  Mojotone.com
Speaker re-cone kit for CV C-187:  SoundSpeakerRepair.com (they make great kits, ask for Rich)
Bolts, black (of which there were many) – BMBfasteners.com
Speaker clamps, black, metal:  Usspeaker.com (stock #: G0790)
Casters:  Grainger.com (item #: 4X696, Rigid Plate Caster, 176 lb., 3″ diameter)
Aluminum kick plate:  Onlinemetals.com (stock #: 5052 or 6061)
White T-molding:  T-molding.com (stock #: T-WHT-81)
Foot cups, black plastic:  Pirk (search this forum)
370 volume and tone control knobs:  Newark.com (SKU #: 29C0178, Mfgr Pn. PC1F2B)
Mortite caulking cord for sealing the speaker and cabinet cover:  Frostking.com
George Grexa is also an excellent source of genuine acoustic materials: acousticbassusa.com

And so we come to the end of the project. Thank you for following along with me, it’s been a blast. I bet that I hold the record for most edits of a thread, ha! Now I have to get going on my other 371 before I forget all the tricks I’ve learned.

Peace,
Doug

Fade to black.

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