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Mods for the RM-10

  • OktavaModOktavaMod
    Michael Joly’s “premium” mod for the Alctron HRM-10 and clones includes surgery to remove the headbasket slats covering the ribbon, to reduce reflections and ringing. The ribbon tension is corrected, and the transformer is upgraded to a Lundahl to reduce distortion and improve HF response.

Ningbo Alctron Electronics Co., Ltd. RM-10

Pricing & Availability

  • MSRP: n/a

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RM-10 Documentation

BidirectionalNingbo Alctron Electronics Co., Ltd. RM-10

Bidirectional Ribbon Microphone

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.

Specifications

Frequency Response - BidirectionalClick Graph to Compare!
RM-10 Bidirectional Frequency Response Chart
Pickup Patterns Pads & Filters
Bidirectional (2 mV/Pa; 30 - 15,000 Hz)
Ribbon Construction Impedance SPL/Noise
35mm x 5mm pure aluminum ribbon, 2.5 microns thick 600 Ohms (Low) Max SPL: 148 dB
Self-noise: 18.0 dB(A)
Weight Length Max Diameter Interface(s)
496g (17.50oz) 175mm (6.89'') 37mm (1.46'')
  • 3-pin XLR male (1)
Power Specifications

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