Super tweeter for FullRange Driver


I have a pair of Audio Nirvana 15in Alinco Classics that I just got done getting into cabinets. After some listening impressions, I've realized I cant live with the high frequency response these things put out by themselves. They only go to about 15k hz. and it's made music lose its sparkle and sense of space and spacial cues. I was thinking of buying a pair of Fostek T90As and pointing them at the ceiling for a more even dispersion and better integration with the Audio Nirvana driver. My main question is what  capacitor volume would you suggest? Where in the frequency response would you crossover to the tweeter? Would wiring the 8ohm tweeter and the 8ohm Audio Nirvana in parallel make me need to change my amp(Audio Note Kit 1 300b Set) from 8ohm to 4ohms? Any other brands of tweeters recommended for a fullrange driver that is around 96bd efficent? Sorry for all the questions, incredibly new to trying to implement crossovers with full rangers. If this sounds like a bad idea. Please speak up. 
akwilson501
I appreciate the feedback from everybody. Why I would love to try both the magnats and the enigmacoustics, I'm going to work with some fostex t90a's at first to see if I like what they add. If so, I will upgrade at somepoint, so thanks for the advice on those. I'm trying to cross my tweeter over around 15khz, wouldn't a .33uf capacitor be ideal, in a 1st order filter? Considering the 106 db on the fostex, and the 96db for the fullrange.
ENIGM Acoustics Sopranino electrostatic supertweeter

Never seen these before. Wow! killer load for an amp, like most esl’s in the highs.
https://www.stereophile.com/images/614EnSopfig1.jpg

"Sopranino’s magnitude increases with decreasing frequency. However, with the 8kHz filter setting, there is a very high inductive phase angle between 7 and 12kHz, a region where the impedance magnitude drops to less than 2 ohms. This makes the Sopranino very difficult to drive at this setting"
Cheers George
  • Werner Jagusch autotransformers:
https://www.ebay.ca/itm/Autotransformer-fur-Hornspeaker-Altec-JBL-Klipsch-Crossover/223950366633?hash=item34247b67a9:g:gTsAAOSwqOdd3PKr

Makes super tweeter load very mild for amplifier.
For example if  you use Fostex T90a and you need align it with speaker sensitivity 97dB.
You connect T90a to -9dB tap. The super tweeter load that see an amplifier is 64 Ohm.
You must put HP filter before autotransformer. You can use potentiometer in parallel to  autotransformer input for adjust cut off frequency.
akwilson501 wrote:

"I’m trying to cross my tweeter over around 15khz, wouldn’t a .33uf capacitor be ideal, in a 1st order filter? Considering the 106 db on the fostex, and the 96db for the fullrange...

"3uf and 1.5uf seem as little high doesn’t it."

By all means go with whatever works! You may well be right.

My thinking was this: The T90A’s contribution will all be going into the reverberant field, and its radiation pattern is fairly narrow so that on-axis 106 dB doesn’t apply. What does apply is the power response - that is, the sum of the driver’s output across all angles. So when you eyeball the factory curves, the off-axis curves are more representative of what the T90A’s contribution will be:

https://www.madisoundspeakerstore.com/bullet-tweeters/fostex-t90a-top-mount-horn-super-tweeter/

Mentally average the 30 degree and 60 degree curves and imo THAT is a reasonable approximation of what you’re starting out with.

Duke