How close are they to the wall? Most ported enclosure designs require some "clean air" behind them for a specific distance, something like 8~10", but changing that distance can also be used to tweak how the speaker sounds. Cutting the distance down usually kills some of the bass, while pulling it out further "opens up" the bass response. I was surprised at how much difference it made with some speakers I finished last summer. Having the port too close to the wall killed the base, and made the speaker sound "flat", while having it 10" away opened it up. Of course YMMV, and speakers have a mystique all their own.