G12T75 SPEAKER CABINET
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Back in 2005 or 2006 I got frustrated with speakers sounding harsh in this cabinet. I had tried adding fiberglass stuffing but that didn't help. At the same time I had noticed that open backed cabinets sounded pretty good with other Celestion style speakers I had and so I decided to cut an opening in the back of this cabinet. After some reading, I decided to make the open back area the same size as the cone area of the 12" speaker (about 78 cm2), so I cut a 6" x 13" rectangular hole. I have never regretted cutting open the back - it improved the sound a lot. Since then I have built several of the AX84 1x12 cabinets which sound much better because the dimensions were carefully designed, and it made me realize that this cabinet was just too small to be a sealed box. Sounds good open-backed though!
I also bought one of the Weber Beam Blockers and use that now instead of my home built ones pictured below. When I mic the cabinet, I put the mic right at the edge of the beam blocker and it sounds great. This cabinet still has the Celestion G12T75 speaker in it and has gotten tons of use in the last 8 years. Mostly I use it with my Agile LP style guitar with the GFS Mean 90 pickups, which are a humbucker-sized P90. Sounds great clean, with overdrive, or with heavy distortion. I also sometimes use it with my Epi Les Paul (humbuckers), although just for fun I play the AX84 1x12 cabinet more with the Epi.
This speaker cabinet was built from birch plywood using finger joints on the corners. I love the way the "stripes" look on the corners, but plywood is a bit difficult to work with. The surface ply is too thin to allow you to easily sand out defects or glue marks. Oh well, while not perfect up close, it looks great at 3 feet away or more. The finish was a wipe-on antique maple stain from MinWax followed by about 5 coats of polyurethane spar varnish, wet-sanding between coats. The final coat was wet-sanded up to 1500 grit and then hand rubbed using automotive rubbing and polishing compounds to a gloss finish.
The finger joints were done with a router template made from the Stot’s router template guide (not sure if it is still available). This is an inexpensive way to get into dovetails, finger joints, etc., and is very flexible. The more careful you are, the better the results.
As of 2/16/04, the cabinet is loaded with a Celestion G12-T75 speaker. This speaker is billed as the stock Marshall replacement speaker and it has the right vibe. However, it was initially very shrill and gave you ear fatigue fairly quickly. As a temporary fix I added a 5 x 9 inch felt-covered oval wood block to the grill to block some of the shrillness from the center of the cone. This is also known as a "beam blocker", sold by WeberVST. Apparently a lot of guitarists have done this sort of thing in the past (like SRV, who used duck tape on his speaker grills in front of the center of the speaker cone for example) . As noted at the top of this page, after cutting a hole in the back of the cabinet and putting in the Weber beam blocker I have been pretty happy with this cabinet with the G12-T75.
Close-up of treble blocker on speaker grill made from
5 x 9 inch wood oval covered with black felt.
