This month we take a look at the Bartlett TM125 boundary microphone. The TM125 is designed by Bruce Bartlett and Steve Mills who have a combined 57 years of engineering experience at Shure and Crown International.
Drawing on that experience, the Bartlett TM125 is a rugged design that is free from phase cancellation and comb filtering. It has a wide frequency response and is ideal for recording choirs, opera, plays, musicals, solo recitals, small classical-music ensembles and audio for video.
A super-cardioid polar pattern helps gain-before-feedback and provides excellent isolation from sounds behind the microphone including audiences or a pit orchestra.
The TM125 is designed to be floor mounted at the edge of a stage to pick up actors in dramas or musicals. It also excels at picking up footwork of dance groups or players in sports venues.
Housed in a rugged steel chassis, the TM125 can withstand being stood upon and the black finish will help the microphone remain inconspicuous on stage.
What is a Boundary Mic?
Boundary microphones are very different to most mics, they have a very small diaphragm that is usually mounted on a surface plate, which is then mounted on a wall, floor or other large flat surface.
You may have heard of boundary mics referred to as a PZM mic (Pressure Zone Microphone), PZM is a variant of a boundary where the mic capsule is placed just above the surface plate.
If placed correctly, the design of boundary mics prevent phase cancellation. When a more traditional microphone is placed on a stand in the middle of the room, it first receives the direct signal followed by the reflected signal from walls and floors at a slight delay. This is more of a problem when longer distances are involved and comb filtering can occur. The comb filtering and add colouration.
Another benefit of the design is that when placed on a fixed surface boundary, such as a wall, there is a sensitivity boost of 6dB.