[John L Stewart]

Over in thread IBM 1953 Phil said-

** How so ??

Impedance plots are best done with a slow sine wave sweep while feeding the
speaker from a high impedance ( 600ohms plus) source.



..... Phil



Not sure how the thread got over there but-

PV Speaker Test Hookup

For the speaker impedance test run I used an HP 200CD (600 ohm) as the audio source. Connected that thru a Hammond 1700 Series OPT so that there was a conversion from 2500 ohms to 16 ohms. Then another 150R straight into the 16 ohm box, much as Phil suggested.

All done with the speaker box outside (open field) in order to avoid reflections. Can’t afford & don’t need an anechoic chamber, long as it don’t rain.

The results were stored with the Pico Technology ADC216 Virtual Instrument set to Peak mode. Very time consuming. I think with a good audio noise source one could set up the equipment & let it run to completion.

Long ago I did quite a few tests with a mike on a stand, altho not calibrated. Seems to me there is a method using three mikes wherein one doesn’t need any of them calibrated. These daze with the digital TE it is possible to do a couple of runs & subtract out a lot of the errors. But I sure didn’t need all that!

"You can lead a horticulture but you can't make her think."

Cheers to all John