Reslo Timeline – when were which mics made?

The Reslo microphone lineup from around 1967

Reslo, a.k.a. Reslo (Sound) Ltd., a.k.a. Reslosound, was a British manufacturing company who made audio equipment and produced A LOT of microphones between about 1937 and 1978. In just 40 years they went from making primitive carbon button style mics through ribbons to modern looking electrets and handheld dynamics. In the middle were the ribbons that we associate with the brand, including the RB and CR models used by a well-known beat band from Liverpool. 🙂

Reslo mics are by far the most popular brand that we see in for service at the Xaudia workshop, and I probably work on a hundred or more Reslo mics each year. The RB model is the commonest, making up perhaps 90% of those that come in for repair or for our popular Beeb (BBC) upgrades.

Although we have good documentation for many of these microphones, most of the original manuals and promotional material are undated, so we have to work a bit harder to find dates for Reslo products.

I have attempted to summarise when the Reslo models were made by trawling through numerous old magazines, looking for advertisements and reviews. The nice thing about magazines is that the issues usually have dates, which gives us a snapshot of which microphones were available at that point in time. Wireless World and HiFi Yearbook proved especially helpful.* The results are in the spreadsheet below – we may have missed a year or two either side, but these dates are broadly accurate to the best of my knowledge. Information before about 1960 is scarce and should be considered less reliable than that for later models, and we have almost nothing from the wartime years from 1939 to 1945. Additional documents may come to light in the future which can expand our time line. Let’s hope so!

Timeline for Reslo microphone models. Click it for the full size PDF version.

The earliest models appeared around 1937 and include the LC, a carbon mic, and two dynamics, the PR** and PMD. By 1946, with a world war in between, these three models have vanished and the VMC dynamic mic has appeared.

We can see that the RV ribbon microphone was available from around 1949 through to the mid 1950s, when it was superseded by the hugely successful RB and related models (including the SR1 and VR), which were in production until 1973. The end-address CR model (which is really just an RB in a different shell) was launched around 1959 and received a face-lift in 1965 to become the CR2. Amazingly, the VMC and VMC2 dynamic microphones were in production right up to 1968, by which point these heavy paper cone dynamics were very old technology and sonically no match for an imported shiny new Shure or Neumann!

In hindsight, 1973 looks like a year of revolution at Reslosound, with many of the old models, including the RB and CR series, being retried. Several new dynamic models were launched, along with a new logo and even an electret condenser for the first time. The only ribbon microphone left in the 1974 line-up was the MR1, which used a repackaged RB motor with a smaller transformer. I surmise that they were trying to modernise their range to compete with imported mics from Germany and the USA.

Hello John, got a new logo?

But it didn’t work. Sadly, by 1978 Reslo had ceased to exist.

*World Radio History website is an invaluable resource for searching old audio publications.

** They later recycled the PR name for the Pencil Ribbon which appeared around 1962.

Thanks to Sam Fitzgerald Kay and Marco van der Hoeven for their help in compiling this information.

RCA microphone MI numbers and catalogs

You may have noticed that many RCA microphones have (at least) two names. Generally they have a model number with one or two letters before or after the number, for example 44BX or KU3A. But all RCA products also have an MI number, which is short for Master Item.* The MI number is usually four or five digits and may or may not be followed by a letter, and may contain extra information such as minor improvements or a different finish. A major change might involve a whole new number For example a shiny black and chrome RCA 77D is MI-4045-E and the improved 77DX is MI-4045-F. However the broadcast grey version of the 77DX was considered sufficiently different to become MI-11006-C.

I took a little tour through some old RCA product catalogues and attempted to correlate the microphones’ common names with their MI numbers, and track any minor revisions across the years.

The full document can be downloaded here as a PDF.

The 1930s saw a rapid development in ribbon microphone technology but documentation from that era is hard to find. (That is a big hint – if you have any old RCA catalogs then please share them widely). We have a 44A manual from 1933, and by 1936 the early PB series and related microphones were already being phased out, with only PB90 left in the catalog The longevity of the 44B/BX and 77D/DX models is notable but expected, with each being in production for around 20 years. Other models appear only fleetingly – the 77B and C models appear only in 1948, and the B1 and C1 only in 1950. Some models such as the SK-50 and KU2 do not appear in any of these documents.

From 1968 onwards RCA introduced a new look, retiring the old red meatball logo in favour of a three letter graphic with a modern stylised font.

RCA logos – from 1000logos.net

If you have any further information or dated documents to help improve this work then please get in touch. Thank you.

* I have seen MI called Master Index in places, but the RCA catalogs call it Master Item, so let’s go with that!

** British spelling. RCA use the American English “catalogs”