CB Mods
Premium Member
A radial ERS fixture has the lamp enter the reflector housing along a radius of the ellipse as opposed to an axial fixture where the lamp enters the reflector on axis of the ellipse. The radial fixture was a long time standard, though the reflector is less efficient than an axial reflector. The most popular radial ERS was probably the Altman Cat#360-6x9, pictured below.
Radial ERS fixtures are also occasionally called "top loaders" due to the positioning of the lamp cap.

The reason that the lamp had to enter the reflector off axis is because incandescent lamps of the period had a "burn position" specified by the manufacturer, due to the way the large and heavy filament was supported. Lamps used in ERSs were "BU30," meaning "Base Up, +/- 30° ". Thus when the fixture was hanging above and pointing down toward the stage, the lamp ends up more or less vertical. Until the advent of T/H lamps and fixtures to take advantage of their properties (one of which was the ability to burn in any position), all ERS fixtures were radial until about 1970. With the axial Altman 360Q having been introduced in 1974, the 360 line was discontinued around 1991.
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Resident Curmudgeon
Senior Team
Premium Member
Re: Radial ERS

I'm not sure this definition is accurate, as an ellipse has no radius (but two axes).

Also, one member has pointed out that this is a slang term for what he and everyone else in NYC referred to as Incandescent ERS, as they fell out of favor once the T/H lamp came in.
Those units are Altman 360's, (not 360Q's). Normally known in the rental business as "incandescents", as opposed to "Axials". I must confess, it seems like "radial" for an ERS is a Control Booth term! ...
I first heard the term "radial" used by Larry Scheoneman, owner of DesignLab Chicago, in the mid 1980s. ...
I think Larry made it up. Maybe it's a Chicago thing.

In New York, we call them "incandescents".

(For any of you that are lucky enough to own the classic roadhouse crew tee shirt: "We don't care how they do it in New York", sorry. New York is where the thing was invented!)


As I said, I first heard the term "radial" from the Owner of DesignLab Chicago around 1984. Anyone know of usage of the moniker "radial" before 1984? Larry doesn't remember where or when he first heard it.
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Well-Known Member
Premium Member
Fight Leukemia
Re: Radial ERS

Another quibble on the blurb. It may be fair to say that the Altman was the most popular in the US. However, Strand Lekos were once designed with the same base-up/filament-down lamp housing, and used to be very popular in other countries; so popular that the term Leko and ERS are often considered synonymous.

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