Marvel Posted September 13, 2019 Share Posted September 13, 2019 @Chief bonehead Roy... I've picked up some MWM cabs w/K43 woofers in them. Do you think I can power them safely with a Crown amp only rated for 4 or 8 ohm loads? Not at home but in a small venue setting. Thanks Quote Link to comment Share on other sites More sharing options...
Chris A Posted September 13, 2019 Share Posted September 13, 2019 Bruce, here's an input impedance plot for an MCM1900, which crosses at 350 Hz from the MWM (K-43 woofers) to the MSSM (in four-way operation): Chris Quote Link to comment Share on other sites More sharing options...
Marvel Posted September 13, 2019 Author Share Posted September 13, 2019 Everyone has said this would be fine and those plots seem to agree. I guess I won't sweat it. Not like I need to be straining the amp anyway. It won't be at rock concert levels. My quest has always been the older literature for the K-43 shows them as 8 ohm speakers, but they definitely are not. Thanks Chris Quote Link to comment Share on other sites More sharing options...
Chris A Posted September 13, 2019 Share Posted September 13, 2019 IIRC, the K-43s are wired in parallel in the MWMs. The Thiele-Small parameters for the K-43 on the forum is showing a 6-ohm nominal input impedance. That would otherwise make the MWM input impedance 3 ohms--nominal. But the Z-magnitude plot above shows a higher minimum than the nominal calculated value from T-S parameters. I like to see Z plots, not "nominal" values, which to me have no meaning. The concept of impedance implies a function that changes with frequency--not a "nominal" singular value. If you look at the complex plane impedance of a 1980s-era Klipschorn (from the Richard Heyser Audio magazine review in 1986), it shows that "nominal" has no real meaning for the Khorn: I was encouraged to see that the MCM1900 Zin plot was much better behaved. If you've had older Khorns or La Scalas, I would be a lot more worried about amplifier stability under high loads with them (using the supplied passive crossovers). Tri-amping Khorns/La Scalas, or biamping MWMs and some other HF horn and compression driver would typically increase stability over passive network crossed loudspeakers. Chris 1 Quote Link to comment Share on other sites More sharing options...
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