I built a pair of Adire Audio Kit 281 ported towers a few years ago, and have always really loved them. The bass is impressive, and they are very warm…
Recently I've been listening to other speakers, and come to realize that the inexpensive but good tweeters are lacking in the upper registers.
I was hoping there might be a similar but better performing tweeter that I could replace the Audaxs with. If I can do that economically, it may be worth it. If not, I'm looking at upgrading to a nice pair of near field monitors.
I setup my PMC DB1 monitors on top of the 281s for a quick test, and was blown away at the difference. The DB1s are a bit bright for my taste, but the 281s really mask a lot of detail and presence (10kHz and up). The sound stage really suffers.
I'm afraid there's an inherent flaw in the design of your 281 kit. And I think that there's no simple fix for it, such as replacing the tweeter.
The problem is using 8" woofers in a 2-way design with a tweeter that cannot go lower than 2200 Hz. Most, if not all, 8" woofers cannot go that high, and certainly the Audax AV8 should not. The frequency response curve provided by Audax suggests they are going into breakup as low as 700-800 Hz. From that curve, I'm guessing that I would not want to listen to them above 1000 Hz.
Most drivers loose significant off-axis performance as the sound wavelength gets about the same length as the diameter of the cone. For an 8" cone that roughly corresponds to about 1600 Hz. That's only an estimate, some off-axis frequency response measurements would eliminate the guessing. So well below the crossover point of your speakers, the woofers may be projecting sound in a narrow beam rather than dispersing it widely. That could easily explain why you thought their sound stage suffers.
The 281 probably does bass very well, as you had mentioned. But the upper midrange, roughly 1000 to 2000 Hz, probably suffers. That might also explain why you thought the DB1 speakers sounded bright. If you're used to the 281s, any speaker that lacks the "hole in the upper midrange" could indeed sound bright in comparison.
Most good designs that I've seen using 8" woofers are 3-way speakers, with a crossover point from woofer to mid well below 1000 Hz.
