Of course, this very inexpensive little amp is intended primarily as only a practice amp but I do play through it 1-2 hours per day and the tone (or lack thereof) was becoming grating. A flat, unfocused cardboard box sound to my ears. So I decided to see what, if anything, could be done about that. I don't have sound measuring equipment so the results I report here are only my subjective listening impressions. I was playing a Guild Starfire II Newark Street reissue, with a fresh set of D'Addario EXL170. I opened the cabinet up and discovered a very cheap looking, no-name driver and an empty box. No surprise given the retail price of this unit. While in there I did some rough measurements and calculated the internal volume to be about 27 liters (after allowing for driver displacement) or just shy of 1 cu.ft. Using Speaker Builder Pro, I modeled a number of different drivers from different manufacturers and at different price points. As expected for a small, sealed enclosure like this, they all showed a gradual roll off of the low end beginning at about 100Hz. Some of the more expensive drivers (e.g. Faital) showed slightly better low end extension but IMO not enough to warrant the substantially increased cost. I finally settled on the Celestion BL10-100X BL10-100X Immediately upon unboxing it, I could see that there was going to be some improvement somewhere. This driver weighs about twice as much as the OEM that was in there. When it was wired in, that proved to be true. Not to exaggerate but it seemed like an order of magnitude improvement. That was confirmed after a few hours of break in. The notes were now focused, round and full of harmonics like never before. Although this is a 4R amp into an 8R driver, I wasn't concerned about loss of volume (I only use it for practice anyway) but there didn't appear to be much loss, possibly because the notes were now musical and not some sort of "blat". Likewise, although I can't measure it, there seemed to be a bit more low end extension, possibly just because those low notes are more defined now. I had read many times that stuffing can improve the response of a sealed enclosure, so I decided to give that a try also. Acousta-Stuf isn't available locally and the shipping cost would have been prohibitive so I just went to my local home building supply and they had R14 fibreglass house insulation available in individual batts 48" x 16". Once home, one of those weighed in at 450g or about 1 lb. Recommendations on the net for the amount of stuffing were all over the map from 0.5 lb per cu. ft. up to 1.5 lb per cu. ft. I tried various amounts within that range and finally settled on about 300g or about 2/3 lb. Again, a noticeable positive improvement. I have been able to remove all traces of "boxiness" or hollowness, without constricting the tonal response. The amp now does a reasonable job of reproducing what I dial in from my guitar. I can get a nice tight, dry growl (without the horrid Scrambler) or I can get a more open "blooming" response. Again, it's just my ears but the E(4th) has very pleasant extension (given the limitations of the box size) that wasn't there (or heard) before. I was going to replace the power supply capacitors because in my experience of messing around with power supplies in DIY audio amps, DVD transports and DACs, higher quality caps can make a big difference in bass response. I don't know if that's true in a bass guitar amplifier. In any case, the amp is designed and built in such a way that in order to get the power supply caps out, one would have to remove at least the transformer and possibly take the entire board off the chassis, which would involve removing all knobs and jacks from the front panel. I'll leave that for another day, if at all. The bottom line is that I am more than pleased with the results. It is by no means a world class amp but it's now very listenable and enjoyable. I use the amp only for practice but I would not be embarrassed (volume or tone wise) to take it into very small venues (coffee house, etc.) to accompany a singer or melody instrument soloist, where the amp wouldn't have to compete with a full kit drummer or a lot of electric instruments. My costs were $109CAD (incl shipping and taxes) for the Celestion driver and $2.75CAD for the fibreglass stuffing. As always, your ears may hear differently than mine.