With a power output of only 6W Fender Champs and Vibro Champs aren't really suitable for gigging, but they're ideal for playing at home and they're also brilliant for recording because they won't overload your microphones. But most users regard the speakers as the weak link.
Champs were always budget models, and the stock 8" speakers gave a compressed and boxy lo-fi tone. They get flustered when pushed and the bass is lightweight. Sourcing suitable 8" drivers is tricky because Champs and Vibro Champs are designed to drive 4 Ohm rather than regular 8 and 16 Ohm speakers, but you can get replacements from Jensen and Weber.
After some research I decided to swap my 8" speaker with a 10", and ordered a Weber Sig 10-S (www.tedweber.com). On older amps the speaker baffle was screwed into position so it was easy to remove and replace, but the chipboard baffles in later cabinets, like mine, are slotted, pinned and glued into routed channels in the cab itself and the speaker cloth is stapled to a false front that's 1/2" thick. I removed the front, peeled back the vinyl at the base of the cabinet then sawed down the baffle at each side leaving about 1" clear of the sides. Then I carefully tapped out the bottom section and filled the slot with Ronseal wood filler.
To make a new baffle I bought a 12mm plywood offcut from my local DIY store (they even cut it to size). The new baffle was placed on top of the side pieces left from the original baffle then, after drilling two pilot holes through the baffle and side pieces on each side, I temporarily screwed the baffle in place with the amplifier section fitted.
I placed my Weber speaker inside the cabinet and established the position where the speaker cleared the valves and transformers. To achieve this I had to place it slightly off centre. With this new position marked I cut out a circular hole out of the baffle with a jigsaw and sprayed it – and the rest of the exposed wood and filler – matt black.
After bolting the Weber to the baffle I removed the staples securing the original speaker cloth and transferred it onto the new baffle using a staple gun. Lastly I fitted the baffle, screwing it in place from the inside, and connected the speaker.
If you only do one mod to your Champ, change the speaker. The improvement was extreme. For the first time ever my Champ actually had bottom end and it sounded like a real amp rather than a practice amp. It was significantly louder, with sweeter highs and no nasty speaker rasp.
Blackface Champs don't do heavy gain stuff, but single coils will provoke them into a throaty overdrive when you max out the volume. Fortunately the clean and semi-dirty tones are very fine, the tremolo is lush and they respond well to overdrive pedals. Remember however that electricity is dangerous stuff so refer mods to a qualified technician if you are in any doubt.