Infinity L-EMIM
The L-EMIM is one of Infinity's planar magnetic transducers. It is the "entry-level" version of the company's EMIM (Electromagnetic Induction Midrange) driver, and a direct sibling to the more famous EMIT tweeter. It's a component, not a complete speaker. It turns up in the hands of restorers working on Infinity's Reference Standard (IRS) systems, where it served as the midrange. The IRS flagship was first shown at CES in 1980. The L-EMIM was one of the earlier EMIM transducers, conceived, in Infinity's own telling, to deliver pure, low-mass, high-accuracy midrange reproduction.
Mechanically, the L-EMIM is a thin polymer film diaphragm with a printed aluminum voice coil, suspended in a magnetic field from a ceramic magnet array. A parts surplus listing gives the magnetic structure as an 11 oz. ceramic magnet, a stamped aluminum voice coil with 2.5 ohm DC resistance, and a diaphragm measuring 1.5" x 2.5". The same listing calls the L-EMIM "the midrange version of the EMIT tweeter" and recommends a 1000 Hz second-order crossover. Sensitivity is listed at 89 dB @ 2.83 V/1M, with dimensions of 4" x 2.75" x 1.25" (flange 4.25" x 3"). A forum post adds that the L-EMIM is the same driver as the standard EMIM, but with a different mounting flange and lower impedance. No exact impedance figure is documented.
Owners are split on the L-EMIM. One listener calls it smooth, detailed, and better than most cone midranges he's heard. Another finds it harsh, with a resonance around 3 kHz, and replaced his with a Morel dome mid. Everyone agrees on the fragility. The foam surround rots out and the diaphragm sags, and the diaphragm is easily damaged by excessive volume or amp clipping. A matched pair of NOS drivers sold on eBay for $149.99 plus shipping, and the seller noted the foam surrounds were still soft. That is the exception, not the rule. A period review noted that the new EMIM driver offered a substantial reduction in diaphragm resonances and breakup modes, with more than 12 dB greater dynamic range than previous versions Audio (April 1995, p.66).
The record on the L-EMIM is thin in a few places. No production years, no original price, and no power handling figure are documented. The frequency range is contested. Infinity's own historical overview says the L-EMIM handled midrange from around 100 Hz up to about 4 kHz, while the parts dealer lists 600 Hz - 25 kHz. The driver was a midrange in the IRS Beta, so the manufacturer's figure is the more credible one.
Known specs, as documented:
- Planar magnetic (electromagnetic induction) transducer
- Thin polymer film diaphragm with printed aluminum voice coil
- 11 oz. ceramic magnet structure
- Stamped aluminum voice coil, 2.5 ohm DC resistance
- Diaphragm: 1.5" x 2.5"
- Sensitivity: 89 dB @ 2.83 V / 1M
- Dimensions: 4" x 2.75" x 1.25" (flange 4.25" x 3")
- Recommended crossover: 1000 Hz, 2nd order
- Used as midrange in the Infinity IRS Beta
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