Sunday, July 26, 2009
How to fit a Weber alnico speaker into a Champion 600 with a JJ 6V6
The original owner of this Champion 600 decided to move to a larger amp . I'd put so much time into the mods that I decided to buy it from him to try a few things he hadn't been quite ready to spring for himself. The first was to try a couple Weber 6" alnico speakers. If you'd like to see the index of mods I've done on this little amp, it's here. This is the back of the amp with the "early breakup" smooth cone alnico speaker installed:
Notice the nice bit of clearance between the magnet and the JJ Tesla 6V6. In a stock Champion 600 cabinet the big magnet on the Weber Alnico barely fits if you have a larger bottle 6V6 like the JJ in there. To get the clearance I moved the baffleboard over.
The baffleboard that is in there already has a bit of play. If you unscrew it you can slide it to the left and remount it. That'll give you just enough space to get the speaker in without it touching the tube. Here's the front of the amp with the new Weber installed:
It's easy to see the shifted speaker because I've also removed the grill cloth. The original cloth is so thick that it causes some farting out on low notes. It made a good bit of difference to get rid of it. I plan to find something appropriate to replace it with once my speaker experiments are done.
The stock baffleboard won't shift quite as far as you see in the photo above. It was close enough but I wanted to have a healthy bit of space between the speaker magnet and the power tube so I cut the baffleboard down by a half an inch and slid it over even further. You can get away with this because the TV style front actually covers a good bit of the baffleboad. I used silver sharpie so the cut and drill markings would be clear in the picture:
I marked off one half inch from the right edge and marker centers for new mounting holes a half inch to the left of the originals. That's about 13mm for people sensible enough to be on the metric system.
Here's the baffleboard cut down to size and with the new mounting holes drilled out.
If you do this yourself it's important to note that this view is from the FRONT of the baffleboard. If you do the same thing looking at the back you'll move the speaker in the wrong direction!
Currently on hand I have the stock Champion 600 speaker, a Jensen Mod and two Webers (early and late breakup). I'll post frequency response and sensitivity comparisons in the next round.