Monday, May 25, 2015

Rode NTR - A New Bi-directional Active Ribbon Studio Mic

The Rode NTR ($799) is an active, bi-directional ribbon microphone that surpasses vintage designs primarily because of it's sensitivity (-30.5 dB re 1V/Pa (30mV @ 94dB SPL) ± 2dB @ 1kHz) and tone. In side by side comparisons with Rode's NT1 studio condenser mic, the NTR was 3 dB more sensitive. That surprised me!

Your father's or grandfather's ribbon microphone required so much mic preamp gain that increased noise floor was inevitable. How did they manage back then? Really good mic preamps, usually with a special transformer on the input to step up the voltage, and placement of the mic itself. Plus, early "hi-fi" systems didn't have anywhere near as much bandwidth as a 24-bit recording (or even an mp3). 

How much ribbon you are moving also figures into the formula. That can be achieved by the length of the ribbon or how many ribbons were used in one mic. The Beyer M160 and RCA 77 series ribbon mics grabbed some extra sensitivity by having two ribbons. Think about it. You basically have a relatively fragile strip of aluminum floating in a magnetic field. A sound happens, the ribbon moves sympathetically and that movement within the magnetic field generates a small voltage. 

A lot of "magic" was invested in the early ribbon mics. The thickness of the ribbon was and still is important. The Rode NTR ribbon has a thickness of 1.8 microns. 

Each ribbon is run through a crimping mill that imparts a pattern on the aluminum. The crimp is a "special recipe." This is done to provide the ribbon with some structure to strengthen it and allow it to be tensioned properly. 

Longer ribbons generate more voltage, but longer ribbons are more fragile. The ribbon must be stretched to achieve a linear frequency response. As any ribbon mic ages, the ribbon material will sag and change the response. According to Rode Marketing Manager Scott Emerton, "Our engineers spent a lot of time optimising the ‘crimp’ of the ribbon to minimise any slack being introduced. Also there’s a multi-stage tension and relaxing process for each ribbon as it’s placed in its motor which increases that life."

Addendum: Rode covers you with one new ribbon for free. They also warranty the NTR for a year and for ten years if you register the mic at

Here's an image of the crimping and tensioning jig with a new ribbon spanning across the gap and held in place by the two brass blocks. For a motion picture of this procedure, here's a YouTube link.