Pete B Posted July 16, 2018 Report Share Posted July 16, 2018 I measured the input impedance of the AR-11 drivers many years ago. Recently remeasured the midrange and decided to take a look at the crossover frequency response in simulation for each of the switch positions. I used the AR inductor values including DC resistance and estimated the NPE midrange cap ESR at .1 ohms, the simulator allows these values to be included in the component model but I decided to show it for the caps and not for the inductor: S1, red, is the 0 dB or max output switch position, it is not very flat and there is peaking in the network response around 3KHz. Curve S2, yellow, is the -3dB position and shows a reasonably flat response. S3, black, is the -6dB position with a very flat response and quite a bit of droop below 1 KHz. I thought that the -6dB position sounded best but would have preferred something between -6 and -3dB. S4, brown, shows the response of the AR-3a network set to the dot position, the .8 ohm series resistance is the .5 ohm resistor with .3 ohms added for ESR of the large wax box capacitor. This was my estimate and I found a value of .27 ohms in the AR-3a restoration manual - close enough. The impedance curve shows the input impedance of the midrange driver alone which is important since it loads the crossover network. Quote Link to comment Share on other sites More sharing options...
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.