Some Temporal Differences

When PZM theory first appeared in the 1970s, most mic manufacturers ignored the idea. But certain adventurous engineers began to experiment with various configurations, especially in recording setups where the hemispherical PZM elements were custom-mounted to plexiglass plates. PZMs also began to be ensemble-flown over bands, orchestras, and choirs.

The author - Anthony McLean Live Sound! International Magazine's editor A fine mug shot

Crown (yes, the amplifier company) secured PZM design rights. And back in the early 1980s, I rented some Crown PZMs for theatrical reinforcement. Due to inexperience, my first PZM applications were less than pristine. But when used with bandpass filtering (below 200Hz) to reduce the LF rumble of footfalls, they were the best theatrical footmics I had tried to that time.

But not all PZM designs are Crown-built. Such non-Crown designs are usually referenced as “boundary” mics. I discovered this when a colleague told me that Radio Shack supplied $39 PZMs with a 1/4" connector.

The Radio Shack (ie, Realistic) PZM claims a frequency response of 20Hz-18kHz (no 3dB down points published). More importantly, it is actually a transformer balanced at 600 ohms and easily converted into something you can use.

Simply remove the 1/4" connector about 10" from the transducer and rewire (solder) with your favorite flavor of XLR with the shield connected to Pin1, the tip to Pin2 and the sleeve to Pin3. (Editor’s note: Save the molded connector/cable for future adapter fodder.)

So I Modified A Pair

And here’s what’s happened. In those days I was attempting Tel-Arc-style (Re: relatively mic-minimalist) digital recordings, first using a Sony PCM rig and later Panasonic DATs.

Most times I used expensive German stereo mics costing 30 to 40 times more than these Radio Shack PZMs, but I never worked a remote recording gig without my modified Realistic PZMs and always took them to reinforcement gigs, as well.

They were great for ambience and strategic area micing. And more than once, they collected the majority of the recorded sonic information. Their imaging and presence are excellent. Longer LF waves, however, are somewhat elusive to the approximately 4.8 x 5.5" PZM boundary plate. (Remember, LF displays relatively longer wavelengths.) Still, I never leave for any gig without a couple of these.

Because PZMs are not visually distracting, they can solve mic placement problems that other mics can’t, but there’s more than sight lines and logistics to PZM applications. Allied uses are as ambient mics for live MDMs, assisted listening systems and distent leaning systems.

For sound reinforcement, PZMs are especially effective as OH cymbal mics, inside the piano, and as theatrical mics, to capture vocal presence when actors\singers blocking results in performance towards the upstage voids. While mic placement is usually the key element in reproducing the sound, the key to successfully using these PZMs onstage is strategic equalization. You’ll just have to work this one out.

Power Issues

The colleague who originally steered me towards the Realistic PZMs claims premium AA batteries work well. For my purposes, I almost always use two Radio Shack (#23-469) batteries. The increased voltage of these batteries seems to maximize the Realistic PZM’s SPL capabilities. However, under no circumstances would I attempt to utilize the 2,000 hours of battery life listed in the Radio Shack spec sheet.