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
Hey everyone, thanks for the help, the community has came together wonderfully for me as usual. I am just getting around to adding the Fostek supertweeters to the Audio Nirvana 15in. I ended up going with a .33uf capacitor with an lpad to attenuate the volume of the tweeter. It pairs up wonderfully with the driver and does exactly what I wanted it to. Really opened up the sound stage and added extra detail to everything. Music is much smoother and bass seems more realistic as well. Everything just flows better now. Couldnt recommend more. I will be saving up for some better tweeters at somepoint, for now I'm satisfied. 
Hi @akwilson501 ,

What kind of capacitor do you use?
The capacitor quality and jumper wire quality is very import too.
I prefer paper in oil capacitors for smother sound.

Regards,
Alex.
I don't think this tweeters have enough sensitivity (93dB) for Omega Super 3 high output monitors (97.5dB).
I use Fostex T90A and it is incredibly good. Very detailed, natural and smooth. 

I bought Fostex t90a supertweeters for my Altec 604E 1.5 years ago.

Since most people use these tweeters with a 1st order filter, so I used with a 1st order filter. Moreover, it was technically simple. I had quality Audio Note Cu 1uf copacitors and autotransformers that make it easy to adjust the volume of super tweeters.

The effect of the supertweeters was very positive. More detailed, refined sound, more air and 3D soundstage.

But over time, I began to come to the conclusion, that the high frequencies are still a little lacking, and if I increase the volume of the super tweeters, the upper mids become too bright.

Then I remembered what my friend Sergey ( an experience DIY speaker builder) said that for supertweeters it is advisable to use filters of the 3rd or 4th order. (For example, the Harbath Hl5 has a supertweeter connected by the 3rd order.)

I thought that such a filter would allow me to raise the high friquencies without climbing to the upper mids.

I contacted Sergey for advices and began to build a filter. I used 2 pairs of capacitors that I had: 1uf Audio Note Cu and MultiCap RTX.

The coils were calculated by the online calculator Bessel filter of the 4th order. I bought cheap coils at madisoundspeakerstore.com. First, I set the filter to 12K Hertz, but then I got a small dip in the frequency response in the region of 10-12K. So I decided to rebuilt the filter to 10K hertz.

The 4th order filter greatly weakens the output of super-tweeters, so I had to abandon the autotransformer and connect directly through the Dell 0.5 Ohm resistor, as Sergey advised.

It is too early to draw final conclusions. The parts have not passed break in and I do not listen to it for so long enough. In addition, Sergey advised to shunt the 1uf capacitors with small polyester capacitors.

But the impressions are as follows:

The upper middle is less bright, but cleaner, smoother, more detailed. Vocals, saxophone sound clear, without distortion typical for a 1st order filter (when the tweeter and supertweeter are played in parallel in this frequency range). The chorus sounds smoother and cleaner without mud or squeals.

The focus of the instruments is sharper, the soundstage is more transparent.

There are many more upper high frequencies. A lot more details of cymbals, brushes and so on. Flutes, violins have more overtones. More air and better presence effect.