Vintage RARE ISOPHON 4" tweeter driver loudspeaker 643-14 from Germany

Description

FULLY TESTED!
Nice vintage
Tweeter speaker driver
made in Germany by Isophon. Official size is 4 inches. Cross holes measurement is 4 3/8"(diagonal c/c fixation hole measurement). This driver is a tweeter and recommended capacitor to use is 10uf 25Volt Non polar for optimal result. Don't use loud without capacitor. These drivers were often used in stereo furniture hifi combo and speaker boxes. Output power rated is unknown but this format could be up to 40 watts with proper capacitor. Coil resistance measurement is 5 ohms so it is most probably a 6 ohm (common in Germany) to 8 ohm impedance driver. Tested with a low power PA amplifier and
sound is great with no anomaly noticed. Only 2 in hand from the same source.
FULLY TESTED
All my Speaker drivers are tested with music at the proper impedance setting using a multiple impedance output PA amplifier from radio shack and a FLAC music player on AUX. My criteria is simple, to hear a nice clean sound with no distortion or scratchy sound due to defective voice coil or impurities accumulated on magnet, or due to any cone issues. The type of sound a driver delivers is not considered in the analyse as there are many types of sound depending of many construction aspect (IE: less bass/treble) and it's uses. One of the photos with listing may show the driver under test (if there are wires connected).
SP185