Why ScanSpeak tweeters aren't the same
Copyright 2009 Troels Gravesen
       

"The dealer told me the 9500 and 9700 can work fine from the same crossover....".
This is an all too common statement I read from mails coming in. Sorry to tell the statement is wrong. Actually very much wrong.
It's probably not easy to make a living from selling drivers and if the dealer had said no, he'd probably not sell any tweeter that day....DIY dealers actually live on the assumption that it is easy to make a crossover, which it is not. I've seen complete phantasy crossovers written on the back of the invoice for some extremely expensive crossover components.... Sorry, I get carried away...

The 9700 tweeter features "symmetric drive", i.e. copper plating of the center polepiece and it has cavities routed into the top poleplate too. Due to symmetric drive, the 9700 will have a rising frequency response towards higher frequences as can be seen below.

Sept. 2009: 9900 tweeter now included in study. Read below.

Above the 9500, 9700 and 9900 on the same baffle (SP95 front panel). It will look different on another baffle or with another position on the baffle, but it doesn't change the fact that there are significant differences in frequency response of the two drivers. The 9500 is the more sensitive tweeter of the three. So, how will it look if we apply the same crossover to the two tweeters? See below.

Above the 9500, 9700 and 9900 from same 3rd order crossover (3k/3rd order LR). Quite some difference, actually 3-5 dB at 5-10 kHz.

Above the 9500, 9700 and 9900 targeting the same SPL around 90 dB. As can be seen from the schematics, there are major differences in crossover component values to render the same response. The 9700 response is slightly equalised by the input series coil. Due to the flat impedance of the 9700 this rising response cannot be handled by the more common RC-circuit across tweeter terminals.

So, don't take that nonsense that these tweeters are interchangeable. They're certainly not.