Guest " " Posted July 20, 2007 Share Posted July 20, 2007 "People using the polyswitch arrangement with very high power are blowing tweeters pretty frequently." tell me about it...I'm talking 60 anniversary editions arriving with blown tweeters. Quote Link to comment Share on other sites More sharing options...
Klipsch Employees Trey Cannon Posted July 21, 2007 Klipsch Employees Share Posted July 21, 2007 As we no longer use zenors in any passive product we build now, I can not preform your test. Nor do I have time to waste on 40 year old network design. You boys have fun now, ya hear. Man Trey, that was harsh. The Old Man would have put you over his knee for that one! My old man would tell you to buy a new one. Quote Link to comment Share on other sites More sharing options...
Dflip Posted July 21, 2007 Share Posted July 21, 2007 I guess I'm just inquisitive, when somebody tells me something that I don't believe I have to find where they got there information from and occasionally find the errors in either their or my logic. Bob sounded like he posed a question that did not make sense, I would want to find out if he was right. Then again, that's me. Quote Link to comment Share on other sites More sharing options...
djk Posted July 21, 2007 Share Posted July 21, 2007 "IF the amp is providing more than 5.8 V, the amp output resistance will have to dissipate any voltage over the 5.8 V mark... It may not be a short, but it is darn close to it." Technically, this is not correct. A zener requires a ballast to work properly. For DC this is usually a resistor. For AC it may be a resistor or a reactive component. A reactive component is better because it dissipates negligible power. The crossover capacitor serves as a reactive ballast. In the HIPs I saw in a trade show in 1989, Klipsch switched to a higher voltage zener (after the BeCu flat lead K77 came out), it allows about 3dB more output before clamping. A square wave is a sine wave with all its odd harmonics added out to infinity. In practice it looks pretty square after the 29th harmonic. The 3rd harmonic of 6Khz (the crossover point) is 18Khz, most people can't hear that. The reason the zeners sound bad is the discharge of the non-linear capacitance from the series back-to-back connection when the waveform crosses zero due to the high frequencies involved. Using one zener with a 0.001µF cap in parallel, inside a bridge made with four Schottky diodes, will work better and cost less. "Instead, I suggest using the parallel combination of a RXE-90 / 200 Ohm 25 Watt resistor in series with the positive leg of the tweeter." Technically, this is not correct. A PolySwitch has a hold current, a trip current, and a maximum rated current for a time-to-trip. The RXE090 is rated at 0.9A hold, 1.8A trip, and 7.2 seconds time-to-trip at 4.5A .Draw a curve from 0.9A forever, to 1.8A at about 2 minutes, to 7.2seconds at 4.5A, that's what this device is rated at. The RXE050 has a trip point of 1A, and will pass 2.5A for 4 seconds, about all you can expect from a 1" voice coil on a tweeter. A network higher than 6dB needs a load, or it can burn up. When the PolySwitch opens (or the tweeter burns), the network will look close to a dead short at some frequency. I recommend using a 211-2 automotive lightbulb in series with a 3R3 15W resistor to be place in parallel with the PolySwitch. This will load the network when the Polyswitch opens, drop the volume a small but noticeable amount, and provide over 10dB of attenuation if severe overdrive continues. Quote Link to comment Share on other sites More sharing options...
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