Driver unit : PM6 driver, earliest type
This alnico unit is mounted on the older Acousta enclosures.
Early PM2 driver
Look for "PM2" embossed in the upper left corner.
Tiny screws (red arrow) are for adjusting the horn to the driver frame.
This old PM2 requires a special horn. Modern PM2's are common, so I look for the "PM2" stamp to avoid mis-matching. The black rubber surround is not a Lowther original. It is made by Kawaguchi Audio in Japan.
Driver unit : PM4
I bought this PM4 with no enclosure five years ago, and mounted it in Kawaguchi's cabinet. (left photo).
I removed the original center diffusor and replaced it with Kawaguchi's aluminum alloy pencil type to enjoy direct sound. It brings the sound's focal point five meters in front of the enclosure
The stock PM4 diffusor is the plaster ball type shown in previous pages.