Mobius Band needed a PA for our three part harmony vocals.

We purchased this Overeem column PA system new in 1974.

The PA was built by Hans Overeem of Sydney. Sadly, the company is no longer in business.

The system comprised a 6 channel mono mixer, and two powered speaker boxes, rated at 100WRMS each.

Each box had four Rola Plessy 12UX50 speakers, rated at 50WRMS each. These original Rola Plessey speakers are now becoming sought after in their own right!

Rather than waste the two Plessey speakers, I cut the old boxes in half, installed the removed speaker and added a tweeter horn for use as a stereo speaker system.
In 2001, we replaced the columns with a more modern looking boxes. We replaced one of the Plessy speakers with a horn and installed a three-way crossover system. Thus we had a horn, two mid range speakers and one speaker for the bass frequencies.
It had an unusual architecture (for the time), in that the amplifier was built into the back of the box and it had power-in and power-out connections on the amp so that additional speaker boxes could be "daisy chained" together to keep expanding.

In the late 70's, we put the mono mixer aside, and began using a stereo mixer to enable us to pan the three vocals.

It sounded terrific.
It STILL sounds terrific!