Brightness is relative. I think B&W speakers ARE bright, and they DO lack low bass - IN COMPARISON TO MANY MODERN STUDIO MONITORS OR CHEAP CONSUMER SPEAKERS. I have a pair of B&W 800d speakers which are bi-amped. Each speaker is running two Classe CAM-600 monoblocks. The room has been extensively treated, and was even tuned by a professional acoustician. YES, these speakers are bright, and sub-bass is not super powerful. HOWEVER... The quality of the speakers is VERY good. They are incredibly accurate sounding - and VERY VERY tight. Transient sounds and quick bursts are never lost in muddiness or lack of detail. These are super super high quality speakers, that sometimes for me have a less-than-ideal frequency response.
On certain types of recordings, this bright sound with little sub-bass is really nice (especially on naturally darker recordings - a lot of classical and/or jazz).
On other types of recordings (rock/pop/r&b, etc), this bright sound with little sub-bass can be obnoxious - sounding harsh, and weak in the low end - especially at loud volumes.
There are ways to address the issue... For example, if your speakers are in the middle of a room, and you want more bass, just push them up against a wall. If you STILL want more bass, push them into the corners of the room. This will DRASTICALLY increase the overall bass energy you hear. Also, in an anechoic environment, the speakers may tend to sound brighter - so treating all of the near reflection points can actually make the speakers even more harsh sounding... but then at least you're not hearing a lot of comb filtering which would result in a less accurate representation of the original audio signal... My speakers sound best to me (at least in this semi-anechoic listening environment) with some EQ - rolling off the high frequencies gradually above 1k, and then a huge low frequency boost. The problem with this, is the EQ has side-effects of it's own... and doesn't sound super natural... it sounds "processed". I have a huge amount of money invested in this system, and I wish I was more satisfied with the overall frequency response of these speakers... I've debated selling them, but I'm not sure I want to deal with the issue right now. I have compared them extensively with other speakers I have though, and these are my opinions based on that.
Unfortunately, most "mixes" are done on small studio speakers... so playing back on a system without a similar curve will result in a sound that is less-than-ideal. In a perfect world, all mixing engineers would use the exact same speaker... and high end speakers could just be a "better" version of that... but the world doesn't work that way. If something was mixed on Yamaha NS-10 speakers with a subwoofer, probably the best listening experience will also be had on a pair of Yamaha NS-10 speakers with a subwoofer. Flame away if you think I'm wrong... I'm always willing to learn, but this has been my experience so far in the last few decades I've been involved in music production.
http://www.htguide.com/forum/showthread.php?14609-Are-B-amp-W-speakers-bright/page4
