Tweeter frequency band to widen sweetspot

[quorzar]

Hello,
long story short: I have a DIY open baffle (Tangband 1772 and 2 Eminence Alpha 15 per speaker) and today I received a pair of Revel F208. The biggest difference is the much much wider sweetspot of the F208.

My question is now: If I add a 3rd way to the system in form of a tweeter, what must be the frequency band, especially in the bottom crossover point, to widen the sweetspot. Im clear that I never get the same as the F208, but what is a good starting point?

TY

QUO

 

[gene_stl]

It looks like you would want to find a tweeter that could come down to about 3K above which the 1772 has a wiggly response curve.
It also would be fairly beamy at the frequency too so you could come down lower. The coles tweeter might be a good match or other 20mm tweeter.