Cabs 101

First let me say that the methods I use in cabinet building will yield excellent results. Thats not to say that my way is the “only” way to build cabinets. Therefore, I don’t want to debate these issues.

lloyd green

Lloyd with My Cabs in Studio Two. Photo by Bob Knight.

Dovetailed joints are acceptable as are bisquited or spline jointed methods of construction. I think the fingerjoint or box joint is easier to fine tune when used with an amp chassis. All my cabinets are fingerjointed pine, using modern glues. I use a “floating” type baffle in all my cabs. To ilustrate a “floating baffle”, just look at a ’65 Twin Reverb. The birch plywood baffle is held in place by cleats and is essentially floating/hanging in the cabinet. I think this allows the baffle to flow with the speaker and resonate with the cab. Look at a ’70’s model Super Reverb and will notice the baffle is let into the sides of the cabinet and the grill is removable, leaving the baffle intact. Perhaps for production reasons this method was adopted, they also started using pressboard or particel board, these did last and screws would not hold. I think these cabinets sound muddy. I can’t tell you how many of these I’ve replaced, evidently other musicians feel the same way.

Tolex can be applied with a variety of adhesives, I choose to use a waterbased contact cement. Apply the adhesive to the tolex and the cabinet, I use a hair dryer to improve tact. This method yields excellent results with no bubbles or voids. As far as cutting the tolex at the corners, its takes lots of practice to make precise cuts. I like the way the tolex was cut on the old Fender amps and thats the method I prefer. I do build cabinets that require on long piece of tolex to wrap the whole cabinet, this does prevent the seams from showing on the top of the cabinet but does require twice as much work, these joints get corner cuts that have 45 degree angles and must be very precise, also the tolex tends to lose its tack/get cold and won’t stick very well because of the time lost between having to make so many corner cuts before folding the tolex inside the cab.

Rick Johnson Cabinets

The use of plywood for the body of cabinet is common practice among large companies. I only use #2 common pine, with small tight knotts. This is acceptable, any loose knotts will eventually loosen up and vibrate. This is annoying. I do watch my rough cuts and try to avoid the knotts especially where the joints and profile are concerned. Cutting through a pine knott with a router cab be dangerous. I like an “open back” cab design for the steel guitar. These cabinets have an upper and lower rear panel. I think the 15″ speaker is hard to beat for the steel guitar. I have built “closed back” cabinets for use with 12″ speakers, these have four 2″ ports in the baffle. This seems to improve the bass response for the smaller speaker. The size of a good steel guitar speaker cabinet can range from as small as 18x18x9 to as large as 20x22x10.5 I like to taper the sides of each speaker cabinet to help project the sound a little. Most players use Black Widow or JBL’s in their cabs.

Cabinet restoration is another topic that I would like to address. If you have a clean amp/speaker cabinet that has no loose joints no gashes or tears in it and has not been painted but just doesn’t shine and sparkle like a new one, leave it alone. You will lose a lot of resale value by trying to improve its looks. I suggest making a new repro cabinet and keep the old cab intact in case you ever sell it. I have seen so many older tweed style cabinets that have aged gracefully only to have someone try and improve their condition by trying to sand and varnish over top of the original surface. Its hard to beat the look of an old tweed amp. I had a guy send me a ’65 Super Reverb cabinet for restoration once.
Rick Johnson CabinetsWhen it came, I was in total agreement with him. The baffle was split, the bottom of the cab was split, the speaker stud screws were broke off. When I took the baffle out the cabinet almost folded up. The fingerjoints were totally gone. I began by removing the tolex and then I took a hammer and knocked the joints apart, removing the bottom board and reglued everything and clamped it back up. The next day I carefully removed the old hyde glue and re-tolexed it and made a new baffleand new rear panels for it. This was labor intensive but this never hurt the value of the amp, think about it?

This process improved the value of this amp, the tube chart was intact and the reverb tank covered most of the bottom, I put the original hardware back on it and used “aged” repro grillcloth. When the customer gets his amp back, he just needs to leave the cover of it for a few months and allow some dust to gather on it, then will have a sweet original looking amp. It will be hard to tell that it was restored.

Class dismissed.
Rick Johnson