RCA 44-BX
Eight and a half pounds of polished black and chromium. Its look became the visual shorthand for a radio studio.
Overview
The RCA 44-BX is a ribbon velocity microphone, built in the United States and sold into broadcast and recording studios as a high-fidelity pickup for both music and speech. It was the third model in a three-model series - the 44A, 44B, and 44BX, per Vintage King - and by the time it reached the catalog it had been refined into something close to an icon. One video description calls it perhaps the single most recognizable ribbon microphone in the world. That's not pure hype. The chrome grille of the 44 series showed up in so many period photographs that it became shorthand for a radio studio itself.
Owners describe the sound in the same terms over and over. Chuck Levin's and the Warm Audio blog call the 44BX renowned for powerful bass, a pronounced proximity effect, lush mids, and a tamed top end. Retro Gear Shop's listing copy calls the tone smooth, warm, and velvety, and singles out its handling of sibilance and its strength on vocals. MetroSonic notes the very smooth character that is typical of a ribbon microphone generally. None of that is measured data. It is what people who have used the thing keep saying, and the sources agree with each other.
The numbers that survive are sparse. The polar pattern is bidirectional - a figure-eight, per the Museum of Microphones and Vintage King - so the 44-BX hears equally well from front and back and rejects the sides. Output impedance is tapped at 50 or 250 ohms according to the Museum of Microphones. Output level is quoted as −55 dbm in the page's own metadata, attributed to Audio (November 1948), while the Museum of Microphones lists −49 VU. The two figures come from different measurement conventions and neither is corroborated by a second source, so treat either as approximate. A measured frequency-response graph exists, but no numeric response value has been captured in the available documentation.
Key Features
Bidirectional Figure-Eight Element
The ribbon element sits in a bidirectional pattern: maximum output directly in front of and behind the microphone, minimum at the sides. That is the defining behavior of a velocity microphone, and it makes the 44-BX a different tool from a cardioid. For a single announcer at a desk, the mic can be worked from either side. For a pair of performers facing each other across it, one microphone does the work of two. It also picks up the room behind the talent as much as the talent, which is why the 44 series ended up so closely tied to controlled studio spaces.
Sensitive Ribbon Free from Cavity and Diaphragm Resonance
RCA's own catalog copy, quoted in the main article, made specific claims for the ribbon element: sensitive, and free from cavity or diaphragm resonance and pressure doubling. Those are engineering claims, not listening impressions, and they describe the appeal of the ribbon topology in general - no resonant cavity coloring the midrange, no pressure buildup at the diaphragm. Whether the 44-BX achieved that ideal perfectly is not documented, but it is the design intent RCA sold.
Voice/Music Response Adjustment
The 44-BX carried a response adjustment to suit either vocal or musical pickup, again per RCA's catalog copy. It answers the proximity effect the mic is famous for. Close on a vocal, a ribbon's bass rises sharply, and the voice setting compensates. Owners treat the switch as part of the instrument. A broadcast voice sound and a full-range music pickup are two settings on the same body.
Alnico Magnet Variants
At least some 44-BX units carry Alnico magnets. A Gearspace poster raised the question of how Alnico and non-Alnico versions differ sonically, and no answer was captured in the available material. Magnet type should be treated as a variable between individual examples, not a settled specification, and it's worth asking before assuming any two 44-BXs sound alike.
Historical Context
Production years are uncertain. The Museum of Microphones gives 1940-1957. A Warm Audio comparison video states 1932-1955. Neither is corroborated by a second source, and the two ranges disagree at both ends. What is clear is that the 44 series was a staple of broadcast and recording studios from the moment ribbon microphones arrived in the 1930s, per AEA Ribbon Mics, and that the 44-BX was used for music and dialog recording from the outset according to MetroSonic. Chuck Levin's notes its use by crooners, band leaders, drummers, upright bassists, and producers.
The 44-BX's reputation outlived its production. In the late 1990s and early 2000s, Audio Engineering Associates began re-creating the design as the R44C and later the R44CNG Centennial edition. AEA describes the R44C as a replica of the most famous microphone in the world - the RCA 44BX. Warm Audio's WA-44 is billed as a faithful reissue of the legendary RCA 44BX, and the AEA A440 pairs a replica of the 44BX element with a built-in amplifier.
Collectibility & Value
Surviving 44-BX microphones are old enough that originality is the exception. One seller's listing notes that the grille may not be original to the mic, and observes that a microphone around eighty years old has inevitably had things changed and fixed over its lifetime. Serial numbers turn up in the low hundreds and up into the C-prefix range - #451, #1017, and #C1914 have all been observed on listings - which suggests a long and varied production run even if the exact dates remain murky.
Servicing is a real part of ownership. Retro Gear Shop describes a unit serviced as needed by Stephen Sank, considered a leading expert on servicing old RCA mics, with a new ribbon installed. Re-ribboning is the standard repair for these microphones and appears often enough in the record that buyers should assume any working example has had one, or will need one. Bruce Swedien's 1993 collector profile of serial no. 1073 lists the original cost as less than $200, though the year and currency behind that figure are not stated.
Current market pricing is not reliably documented. No exact RCA 44-BX listings were live at the time of research, and the only price figure captured - a $3.92 listing on an aggregator - is plainly a placeholder attached to what appears to be a reproduction. Any 44-BX purchase is a specialist transaction: verify the ribbon, ask about the magnet, and expect to pay for condition rather than for a documented market rate.
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