In a recent post http://www.banjohangout.org/topic/222060 I described the replacement of the 5 inch speaker in a small battery powered 2 watt Roland Microcube amplifier with a 6 inch Weber Signature speaker with a ceramic magnet. That turned out so well that I did a similar speaker replacement on a battery operated Vox DA5 5 watt amplifier yesterday.
Here's a picture of the DA5 from the Vox web site http://www.voxamps.com/da5/ This model has been discontinued but is still available on eBay and in some stores for about $140. I was very lucky to get a demo model from Guitar center for $60 and there were some on eBay recently were in the $100 to $140 range.
This is a very nice sounding small amplifier with lots of good reviews online, but like many small low power amplifiers it could benefit from a larger speaker to develop the sound more fully. The cabinet is just large enough to accept an 8 inch speaker and a quick Google search will turn up quite a few posts with pictures of similar upgrades, like this one;
http://www.tdpri.com/forum/amp-central-station/164941-vox-da-5-replacement-speaker.html
I used an 8 inch 8 Ohm 15 watt Weber Signature smooth cone speaker with an Alnico magnet for the upgrade, available directly from Ted Weber at https://taweber.powweb.com/weber/ (look under Signature series AlNiCo Signature 8) for $35 + shipping. I've used a few 10 and 12 inch Signature series speakers in small extension cabinets connected to low wattage amplifiers before and have been quite happy with the quality.
It was a very easy upgrade as these things go, the most time consuming part was cutting the larger hole in the front panel to fit the larger speaker correctly. I replaced the black rubber feet with steel feet that match the front grille, and added a 2 inch sound hole in each side of the amp with screened sound hole covers (as used on resonator guitars). Those side hole increase the sound a bit but mostly I wanted the amplifier to look unique.
Here are some pictures;
Vox DA5 disassembled with original 6 inch speaker. Just unscrew the screws and battery holder, disconnect the speaker, and carefully removed the electronics.
Here's a side-by-side comparison of the Vox 6 inch and Weber 8 inch speakers
Here's how I enlarged the speaker hole by using a power drill to make small holes all around, after which I used a chisel, rasp and sandpaper to clean up the hole. I could have used a small saber saw but it's hard to free-hand a smooth circle and the particle board is easy to work with after the small holes were drilled into it.
Same hole smoothed up. I painted the exposed wood edges black before mounting the speaker
Here's a shot of one of the small sound holes in the side of the cabinet
Because the 8 inch speaker is so large the top edge of it sits behind the solid panel along the top face of the amp, which blocks a portion of the cone. So after the speaker hole was enlarged I used a round cutting wheel on a power drill to cut a notch into the floor of the cabinet so the speaker would sit about 1/2 inch lower. This isn't really necessary but it did make the speaker fit into the new hole better.
This shows how the speaker sits in the notch.
Here's how the new speaker fits the cabinet. The metal feet aren't very noticeable in the picture but they match the silver color of the front grille and side sound hole screens
And here's the finished amplifier, which looks the same as before the upgrade except for the screened sound hole cover in the side of the amp.
The amp looks a little dusty in that last photo but it looks like new after it was cleaned up and it sounds very good for a small low power portable amplifier. This one will be going away to college with my son next fall and I may need to get another one for myself.
JP