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Ningbo Alctron Electronics Co., Ltd. RM-10

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Specifications

Mic Type	Bidirectional Ribbon Microphone
Polar Pattern(s)	Bidirectional
Pricing & Availability
MSRP
Street
Availability	Still Made
Physical Characteristics
Weight	496g / 17.50oz
Length	175mm / 6.89''
Diameter	37mm / 1.46''
Interface(s)	3-pin XLR male (1)
Electrical Characteristics
Impedance	600 Ω
Max SPL	148 dB
Self-noise	18.0 dB(A)
Transducer Characteristics
Type	Ribbon
Ribbon length	35mm
Ribbon width	5mm
Ribbon thickness	2.5 microns

Frequency Chart(s)

Frequency Response - Bidirectional

Description

The HRM-10 is a bidirectional ribbon microphone modeled after the Royer R-121. It is made in China and sold by Alctron to numerous US and European rebadgers, who sell identical mics under their own names. See the Nady RSM-3 and the t.bone RB100.

The ribbon element measures 5mm by 35mm, and is 2.5mm thick. These specs are similar to the R-121; the ribbon in the R-121 is slightly longer at ~44mm.

The mic’s quoted frequency response (30-15k) also matches the Royer mic.

The HRM-10 and its clones seem to be plagued by “sagging ribbon” syndrome more than other designs. This may be due to shipping damage or to poor quality control at the factory, or a combination.

Michael Joly of Oktavamod has supplied a method for diagnosing a sagging ribbon: connect the mic to a preamp and monitor it via headphones. Hold the mic so the ribbon element is parallel to the floor, and then rotate it 180° to flop the ribbon top-for-bottom. If you hear a transient — a clank or thunking noise — it is likely due to a severely under-tensioned and sagging ribbon.

Some users have successfully retensioned ribbons, but the fragile nature of microns-thick aluminum requires care and rewards experience. See sidebar links to mod and repair service providers.

Alctron has modified this mic since its original release. The early runs of the HRM-10, like the R-121, offset the ribbon toward one side of the headbasket. This gives the mic two distinct sounds (front vs. back) and provides higher SPL capability on one side, making the mic useful for louder applications at the cost of symmetrical response (which means the mics are less suitable for use as the “side” channel in Mid-Side applications).

Subsequent runs of this mic have utilized a centered ribbon placement.

The Ningbo Alctron Electronics Co., Ltd. RM-10 is also known as: HRM10, RM-10.