Saurav I dont think youll have much problems withan xover at 3khz because of the system its going to be used in. IIRC your only using a SET at about 5watts or something to drive the mid/ tweet array. I doubt with that much/little power your really going to run into any danger. But it wouldnt hurt to be on the safe side.
Well, it's as much to protect the amp as the ribbon. I don't think my amp will be too happy with a DC short circuit. But you're right, the amp cannot produce enough power to blow the ribbon. Clipping is a concern, but there again, I don't think the rest of my system has enough gain to drive my amp into clipping, and I'd hope that a SET would clip/compress relatively gracefully.
XO and Power Rating
The following information may be helpful (text copied from http://www.wagner.net.au/pae/Ventura/RibbonTweeter.htm)
* * Power Rating Cautions for the JP3.0 Ribbon Tweeter
The JP3.0 Ribbon tweeter is different to a conventional annular coil driver dome tweeter in its electronic characteristics and should to be treated with extra care because of the fragile and sensitive low mass diaphragm and also its impedance matching transformer. Applied power to the ribbon should be limited by careful crossover design for your particular application as this ribbon has a built in transformer with a primary impedance 0.2 ohms DC!. This can in effect short circuit an amplifier below the frequencies of 200Hz. Thus a high order crossover is used. Also, because of the ribbons low mass diaphragm, they are susceptible to low frequency damage below 1Khz and are therefore best operated at frequencies above about 3Khz. SSS recommends a 3rd order filter (18dB) between 3.7K to 9Khz. Also, the higher the crossover frequency the higher the system power will be too.
* * Crossover Filters for the JP3.0 Ribbon Tweeter.
Because of the JP3.0 ribbon tweeters' wide bandwidth to 40Khz the crossover type is very important. Only use high grade, high quality capacitors and non inductive resistors. WARNING; If a simple 6dB/octave filter (single capacitor in series with the ribbon) is used below frequencies of 5Khz then low frequencies may damage the ribbon diaphragm! A 6db/Filter, single capacitor should only be used above 8Khz as in a super tweeter type speaker system (suggest a 2.2uf /400V metallized poly as a maximum value, see SCR2.2). For lower crossover frequencies in the range from 3KHz to 8KHz the ribbon requires a minimum of a 2nd order 12dB/oct or better a 3rd order 18db/octave high pass filter design. See below for a design which SSS has developed specifically for the JP3.0 ribbon tweeter for general applications, as tested. It is a 3rd order crossover (18dB) at 7.5KHz developed to optimize power handling and frequency response maintaining high quality and wide bandwidth for this very impressive ribbon tweeter. The resistor matching attenuator is about -4dB making the JP3.0 suitable for use with a driver array of about 92dB efficiency, adjustments here may be required. Use only premium quality components for best results. You will enjoy the open colourless sound of these premium drivers.
Regards,
The following information may be helpful (text copied from http://www.wagner.net.au/pae/Ventura/RibbonTweeter.htm)
* * Power Rating Cautions for the JP3.0 Ribbon Tweeter
The JP3.0 Ribbon tweeter is different to a conventional annular coil driver dome tweeter in its electronic characteristics and should to be treated with extra care because of the fragile and sensitive low mass diaphragm and also its impedance matching transformer. Applied power to the ribbon should be limited by careful crossover design for your particular application as this ribbon has a built in transformer with a primary impedance 0.2 ohms DC!. This can in effect short circuit an amplifier below the frequencies of 200Hz. Thus a high order crossover is used. Also, because of the ribbons low mass diaphragm, they are susceptible to low frequency damage below 1Khz and are therefore best operated at frequencies above about 3Khz. SSS recommends a 3rd order filter (18dB) between 3.7K to 9Khz. Also, the higher the crossover frequency the higher the system power will be too.
* * Crossover Filters for the JP3.0 Ribbon Tweeter.
Because of the JP3.0 ribbon tweeters' wide bandwidth to 40Khz the crossover type is very important. Only use high grade, high quality capacitors and non inductive resistors. WARNING; If a simple 6dB/octave filter (single capacitor in series with the ribbon) is used below frequencies of 5Khz then low frequencies may damage the ribbon diaphragm! A 6db/Filter, single capacitor should only be used above 8Khz as in a super tweeter type speaker system (suggest a 2.2uf /400V metallized poly as a maximum value, see SCR2.2). For lower crossover frequencies in the range from 3KHz to 8KHz the ribbon requires a minimum of a 2nd order 12dB/oct or better a 3rd order 18db/octave high pass filter design. See below for a design which SSS has developed specifically for the JP3.0 ribbon tweeter for general applications, as tested. It is a 3rd order crossover (18dB) at 7.5KHz developed to optimize power handling and frequency response maintaining high quality and wide bandwidth for this very impressive ribbon tweeter. The resistor matching attenuator is about -4dB making the JP3.0 suitable for use with a driver array of about 92dB efficiency, adjustments here may be required. Use only premium quality components for best results. You will enjoy the open colourless sound of these premium drivers.
Regards,
I have a passive XO between the midrange and the tweeter. If your system is all active, I believe you need to put a cap between the amp's output and the ribbon tweeter. Make sure the cap is large enough to not skew the frequency/phase response in the region the tweeter is being used, but not so large that damaging low frequencies (like the 200Hz mentioned above) can make it to the tweeter, in case someone accidentally sends a full-range signal to the tweeter. So I dunno... if your active XO is at 3500Hz, add a cap that'll block stuff below 1000Hz, or something like that.
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