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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
mijostyn's avatar
mijostyn
8,570 posts
 
Duke, I think the L pad or resistor goes in series in front of the capacitor and driver. No?
Ribbon tweeters are mini line sources. They do not send energy up or down. In other words their vertical dispersion stinks. Their horizontal dispersion depends on the width of the driver. The narrower it is the greater is the horizontal dispersion. I would think these characteristics would make a ribbon tweeter excellent for an ambient driver. In thinking about it I would aim it at the opposite side wall just in front of the listening position. This would send the sound off the side wall into the rear wall then on to the opposite side wall before getting to the listener, the longest path. 
mijostyn's avatar
mijostyn
8,570 posts
 
George, you would be the guy to buy Hill Plasmatronics. Mesmerized by the purple light. Turn on that gas!
mijostyn's avatar
mijostyn
8,570 posts
 
Those tweeters are banned from import to the US. Ozone factories. The Hills avoided this by using Helium to create the plasma. Thus my comment about the gas. The Hills were awful by the way. I helped set a demo pair up. Must have been 1978 or so. The plasma tweeter worked fine if you like point source speakers but the rest of the speaker was terrible not to mention having huge helium tanks and being butt ugly. They did not last long.
alexberger
916 posts
 
In my case adding T90a tweeters didn't change tonal balance too much
but made sound much more refined.
Not just added air, soundstage and high frequency extension (as was expected), 
but also made better separation, more realistic tone of instruments, better bass definition and texture, better soundstage layering.
Thank a lot to @zipost who convinced me to try Fostex super-tweeters.

audiokinesis
2,740 posts
 
mijostyn wrote: "Duke, I think the L pad or resistor goes in series in front of the capacitor and driver. No?"

If the input power levels are low then you can probably get away with placing the L-pad in front of the capacitor, but you LOSE the L-pad’s feature of not shifting the crossover point. This is because the impedance of the load that the capacitor "sees" is no longer constant as you turn the knob on the L-pad.  At high power levels, you run the risk of cooking the L-pad because it's seeing a full-range signal from the amp. 

The L-pad is designed to go just in front of the tweeter, where it maintains an 8-ohm load regardless of how much attenuation is cranked in so the crossover point doesn’t change. Also in this location, it is protected by the crossover capacitor.

Duke
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