You mean a concave bottom!!! I have never tried this myself, but apparantly peavey speakers arn't very good (cheap end) A friend of mine said that he put a good quality speaker in his 'solo' and it made the world of difference(apparently) I used one for years busking, It was a good workhorse. On the downside, the 12v power input plug wears very quick and can let you down just when you dont need it.