Sennheiser LABOR W MD4 Noise-Cancelling Microphone.

Following on from my posts about the LABOR W MD7 and the MD21, here is another gem from the early years of Sennheiser.  Released in 1951, the MD4 is an unusual looking, handheld, noise-cancelling, dynamic microphone designed to suppress feedback and ambient noise.

Sennheiser LABOR W MD4 Noise-Cancelling Microphone.
Sennheiser LABOR W MD4 Noise-Cancelling Microphone. Back view
Back view.

So How Does It Work?

The MD4 is side addressed. Sound can enter through the openings on either side of the capsule. When the user is speaking in close proximity to the front of the microphone their voice is strongly reproduced and very little sound is entering at the back of the diaphram. On the other hand, unwanted sound arriving at the microphone from further away, and in particular at the sides, will enter front and  back simultaneously. Bearing in mind that the back of the diaphragm is 180 degrees out of phase with the front, these sounds will be cancelled in varying degrees. This capsule design achieved a considerable degree of off-axis rejection, making it much less likely to pick up unwanted sound from PA loudspeakers or other sources.

Outside of the military and commercial aviation, the MD4 was the first purpose designed, dynamic, noise-cancelling microphone that I can think of, on sale for domestic use.

N.B. Sadly the original Grosse Tuchel connector has gone missing but at some point I will replace it. For now it works fine direct wired.

Sennheiser LABOR W MD4 Noise-Cancelling Microphone.

In a market previously dominated by feedback-prone omnis, the MD4 gained considerable popularity for use in public address and continued in production until 1973. Although initially intended for use with speech the MD4 also found favour as a vocal mic.

Here is the legendary Sonny Boy Williamson II pictured at a folk/blues festival in Germany in 1963. 

Sonny Boy Williamson II pictured at a folk/blues festival in Germany in 1963. 
Sonny Boy Williamson II pictured at a folk/blues festival in Germany in 1963. 

So what does it sound like? 

Here is a Voice Recording Demonstrating the Noise-Cancelling properties of the MD4

CLICK HERE to listen.

And now for something completely different ………….

Close-Mic’d Guitar Amp

CLICK HERE to listen.

N.B.   In the context of a live gig the noise-cancelling properties of the MD4 will provide considerable isolation from other performers.

Below is some technical information on the MD4 from the 1953 LABOR W catalogue.

Microphones featured in the 1953 LAOR W Catalogue. Page 1
Microphones featured in the 1953 LAOR W Catalogue. Page 2

English Translation 

Moving coil microphones

Moving coil microphones have two major advantages over other types of microphones:

  • They are robust and insensitive to weather influences.
  • Due to their low source resistance, they can be easily connected via lines of several 100 metres.

Moving coil microphone MD 2

Universally usable microphone for particularly rough operation. Well suited as a table microphone because of its elegant shape in combination with a table base. Frequency range 50-10,000 Hz. Sensitivity approx. 0.1 mV/ub at 200 . Dimensions: 54 Ø x 120mm. Table base available as an accessory.

Moving coil microphone MD 21

Thanks to a new design and modern production methods, we have succeeded in creating a high-quality universal microphone that, despite its low price, is top class. Frequency range 50-15,000 Hz. Sensitivity 0.20 mV. Dimensions: 120 x 46 x 46 mm. An elegant table base is available as an accessory.

Stand microphone MD 3   

Very popular as a stage microphone because of its barely visible input stage. The high-quality moving coil element housed in the base ensures high transmission quality. Frequency range 30-10,000 Hz. Sensitivity approx. 0.08 .V ub and 200 Ω. Spherical polar pattern. Dimensions: base 170 mm Ø, 60 mm high, tube 900-1 500 mm long.

Stand microphone MD 3 Studio

In a frequency range of 30 to 15,000 Hz, it has an effective treble boost from around 6,000 Hz. Externally, it can only be distinguished from the MD 3 by the form of the input stage.

MD 3 and MD 3 Studio are supplied with an attachable Plexiglass panel, which gives the microphones a slight directivity.

Probe measurement microphone MD 3 M

The extremely small sound absorption of only 8 mm Ø does not cause any distortions in the sound field. Therefore particularly suitable for many acoustic measurements. Frequency response 50-10,000 Hz + 2.5 db.

Moving coil microphones (page 2)

Table microphone MD 3 T

A particularly elegant table microphone for first-class transmission of speech and music. Base plate can be unscrewed and has a thread suitable for mounting on a photographic tripod. Balanced frequency range 50 -10,000 Hz. Sensitivity 0.08 mV/ub at 200 Ω. Omnidirectional polar pattern. Dimensions: ball 60 mm Ø, plate 70 mm Ø, projection 450 mm.

Hand microphone MD 4

The MD4 has proven to be excellent for all voice transmissions where there is a risk of acoustic feedback. Through particularly effective compensation, any sound coming from a greater distance is very strongly suppressed. The MD4 is therefore just as suitable for transmissions from very noisy rooms. Frequency range 50-10,000 Hz. Internal resistance 200Ω. Voltage emitted during normal discussion 4mV. Dimensions: case 60 mm Ø, length 180 mm, weight 380 g. – The MD4 is available with a talk switch and also in a switchable high-impedance version.

Hand microphone MD 42

Field of application like MD4; but is end addressed. Frequency range 200-10,000 Hz. Internal resistance 200Ω. Voltage emitted during normal discussion 2.5 mV. Dimensions 47mm Ø. Length 120 mm, weight approx. 135 g.

Moving coil microphone MD 5

Universally usable microphone in a favourable price range. Can be used as a hand, table or tripod microphone. Excellent reproduction, especially for voice transmission. Available in low and high resistance, with and without a switch. Sensitivity approx. 0.25 mV/ub or 7mV/ub. Dimensions: 86 x 65 x 52 mm.

Speech microphone MD 7

Particularly good speech intelligibility due to emphasis on high frequencies. Therefore recommended for announcement and dictation systems. The soft rubber housing makes the MD7 insensitive to rough use. Available in low-impedance and high-impedance versions. Dimensions: 76 x 48 x 48 mm.

Microphone Accessories

Tripods, flexible necks, table bases, cables, couplings in various designs available.


Conclusion

Throughout the decade following the establishment of LABOR W in June 1945 Fritz Sennheiser and his colleagues at Laboratorium Wennebostal worked hard producing a range of innovative microphones for a variety of purposes, aimed at different sectors of the market. They offered microphones for the home, the office, the stage, journalism and TV and sound studios. As we can see from the catalogue above they demonstrated a remarkable degree of ingenuity, technical expertise and creativity. These are characteristics which distinguish the Sennheiser brand to this day.

Credits

Many thanks to my old school friend Alan Marchant for kindly donating this fascinating microphone. Alan is owner of The Vintage Wireless Co in Manchester at 174 Cross St, Sale M33 7AQ. His shop is an amazing Aladdin’s cave of ancient wirelesses, car radios, gramophones and phonographs. Well worth a visit!

Thanks also to Keith Thompson for sparing the time to record the tasty blues guitar clips.

And thanks to Hazel Hanson for the English translation of the LABOR W Catalogue.

Beyerdynamic MPR 210  (Horizontal Line Array)

Anecdote

A few years ago I was employed to operate sound for a big charity fund raising event at a posh London hotel. The guest speaker on this occasion was a senior member of the British Royal Family who was a patron of the charity. After dinner HRH arrived on stage to deliver her speech. The microphone supplied by the event company was a good old Shure SM58! The Princess positioned herself about 2 feet from the microphone and spoke in a very quiet and suitably regal tone. Throughout the speech she continuously turned her head from side to side without ever once actually addressing the microphone! Meanwhile, back at the sound desk, I had run out of gain, and was desperately tweaking EQ and compression in a fruitless search for level. The system was flat out!  Anyhow, at the end of the speech the audience applauded politely, even though I’m sure that most of them never heard a word of it! As the Princess turned to leave the stage, and before I had chance to grab the gain control, the somewhat inebriated TV host, who was compèring the show, leaped forward and grabbed the mic shouting “THAAAANK YOU VERY MUCH”!!!!!!!!!!!!!!

Anyone who has worked in event and conference sound for a few years will almost certainly have their own similar experience to relate!

So what could be the solution to this common problem?

A few weeks ago, out of curiosity, I purchased a Beyerdynamic MPR 210, a horizontal line array microphone specifically designed for use in conference venues and lecture theatres.

Beyerdynamic MPR210W
Beyerdynamic MPR210W Rear view showing output sensitivity control

Having tested it both in the studio and with a PA in a large conference venue I can honestly say that it does exactly what it says on the tin, and may well be the solution we have been seeking!

Here below is the Beyerdynamic MPR210 Manual and tech spec.

The information sheet below also covers the Classis RM30 which is Beyerdynamic’s vertical line array.

So what does it sound like dealing with a problematic speaker?

CLICK HERE to find out!

Conclusion

The current list price for the MPR210 from UK distributer Polar Audio is £746.41. This might seem like a lot of money for a desktop microphone. However, if you are in the business of conferences /events and lectures, this could be the perfect tool for the job!

P.S.

If you are curious to know more about line array microphones, a while ago I penned a post about my experiments with a homemade vertical line array. https://martinmitchellsmicrophones.wordpress.com/2016/11/03/experimental-line-array-microphone/  

MB – UNITRA TONSIL MDO 23 (Circa 1975-80s)

Between 1973 and ‘75 German microphone manufacturer MB Electronic (today known as MBHO) designed a range of quality microphones that were licensed to Polish state owned electronics company UNITRA TONSIL.

Back in May 2020 I wrote a post about the UNITRA Tonsil MCU-53, an excellent cardioid condenser. Now, (from the same stable) here is the MDO 23, a slender, omnidirectional, studio dynamic.

MB UNITRA TONSIL MDO 23

So What is it Good For ?

The thing I have always liked about omnidirectional dynamic microphones is the absence of proximity effect coupled with the ability to handle high SPLs. This makes them perfect for close-micing loud guitar amps without having to mess around EQing unwanted boominess caused by proximity effect. I have often used a Sennheiser MD21 on rock ’n’ roll theatre shows for this purpose.

Omni dynamics also make excellent speech mics and are very often used in TV and radio for interviews. Once again the absence of proximity effect is useful, allowing a good deal of freedom of movement without significantly affecting the frequency response.

Picking up sound from 360 degrees, Omnis are also just the job when it comes to capturing ‘atmosphere’.

CLICK HERE to hear a range of sound sources recorded with the MB UNITRA TONSIL MDO 23

Technical Specifications

MB UNITRA TONSIL MDO-23
MB UNITRA TONSIL MDO-23

Frequency Response graph

MB UNITRA TONSIL MDO-23  FREQUENCY RESPONSE GRAPH
MB UNITRA TONSIL MDO-23  Grill

Standard 3 pin small Tuchel  connector

MB UNITRA TONSIL MDO-23  Tuchel Connector

Conclusion

Having scoured the internet for information about this microphone I have come to the conclusion that it is somewhat rare! Apart from a couple of photographs, the tech spec and frequency response graph pictured above were pretty much all I could find. Sadly, it would appear that company records of this period have long since vanished in the mists of time.

In common with the MCU-53 I wrote about previously, this microphone has been generously sent to me by a friend in Poland, Adam Wilma. It is a serious quality professional microphone with a myriad of uses, and a very welcome addition to the Polish section of my collection. So thanks once again Adam!

Martin Mitchell Polish Microphone Collection

UNITRA Tonsil MCU-53

Acel GM-17B

MB UNITRA Tonsil MDO-23

The Ronette ‘CORONATION 53’ Crystal Microphone

What is a Crystal Microphone.

When pressure is applied to a crystal of Rochelle salt (sodium potassium tartrate tetrahydrate), causing it to flex, a tiny electrical charge is induced on its surfaces which is proportionate to the amount of pressure applied. Below is a simple diagram illustrating how this piezoelectric property is utilised in a crystal microphone.      

As sound waves cause movement of the diaphragm, varying pressure is applied to the crystal. The electrical signal thereby created can then be amplified to produce audio.

Rochelle salt is fragile and susceptible to damp and the passage of time has not been kind. These days it is becoming increasingly difficult to find crystal microphones that are still in working order. Even though later crystal microphones used ceramic materials such as lead zirconate and barium titanate which were somewhat more durable than Rochelle salt, the stock of working crystal microphones has been steadily dwindling. In the 60’s with the arrival of cheap, reliable, dynamic and electret-type condensers the crystal microphone was quickly superseded. 

During the 1950’s home tape recording became a popular hobby, and there was a super-abundance of budget machines aimed at the amateur recordist. Although some of the more upmarket models came with a dynamic microphone, most of these tape recorders were supplied with a cheap and cheerful crystal microphone…………… Which brings us to the Ronette ‘CORONATION 53’

CLICK LINK BELOW TO LISTEN.

The ‘CORONATION 53’ is a high impedance microphone and comes with a standard 1/4inch balanced jack.

To record my voiceover on the video I used an inline Hosa MIT-129 50k Ohms- 200 Ohm transformer which enables connection to an XLR mic input.

Ronette CORONATION 53 Advert and Tech Spec

Not perhaps the flattest frequency response graph, but nevertheless a bargain for the princely sum of 52 shillings! (20 shillings to the pound in 1953). Based on the Ronette 088-u7 ‘Soundball’ already in production, Ronette spared absolutely no expense in creating the ‘CORONATION.53’. A quick mod to the plastic moulding to create a short handle, and the words ‘CORONATION.53’ in small raised letters on the ball. Job done!  

Conclusion

BBC TV live coverage of the Coronation launched mass television viewing in the UK. Demand was so great that electrical shops everywhere sold out of TVs. Unlike today, the British royal family were at a high point of post-war popularity. Amidst all this flag-waving and razzmatazz Ronette saw a marketing opportunity. However, even in 1953, I really can’t imagine many people rushing out to buy a cheap, plastic, crystal microphone just because it called itself the ‘CORONATION 53’!

Ronette CORONATION 53 crystal microphone

Today they are somewhat rare. Until I bought this one I had never seen one before. However, in fairness to Ronette it does sound a lot better than I thought it would, and might still come in handy for something!

Ronette CORONATION 53 crystal microphone

And it is very shiny!

The Faulkner Phased Array. Another Useful Stereo Microphone Technique.

The Faulkner Phased Array with Extinct Audio BM9s

The Faulkner Phased Array was invented circa 1980 by British Classical engineer Tony Faulkner.

To improve the realism of his recordings, Faulkner sought to gain a better sense of ‘space’ and ambience. Somewhat dissatisfied with co-incident microphone techniques, Faulkner experimented with spaced microphones until he arrived at an array which not only gave excellent positionality, but also captured those elusive qualities of openness.

In common with the ORTF Array and the Jecklin Disc, Faulkner’s technique also exploits the inter-aural time difference between the human ears, which allows our brains to calculate the precise location of sounds. The Faulkner Phased Array uses 2 figure-of-eight microphones mounted in parallel, facing straight forward and spaced 20cm apart. Since the microphones are not splayed, this means that they can be placed somewhat further away from the subject, without detracting from the balance. It also means that in a further back position they can be used to record at head height rather than up in the air. In live concert recordings there are sometimes practical reasons why microphones can’t be placed close to the performers. In this situation the Faulkner Array may provide the perfect solution.

Recording in concert halls and churches where there is sometimes rather too much reverberation, another benefit of this array is that the dead zones of the figure-of-eight microphones are pointing straight out to the sides. This greatly reduces unwanted reflections and thereby improves the clarity and ‘presence’ of the subject.

I recently used the Extinct Audio BM9 matched pair pictured above in the reverberant acoustic of Cheltenham’s splendid Pittville Pump Room.

This recording features dynamic 17 year old violinist Isaac Williams, winner of the Audience Vote in this year’s Gloucestershire Young Musician of The Year. He is accompanied by pianist John Wright.

(N.B. The other microphones on the stand are not part of this recording.)

CLICK HERE to listen to the dramatic opening bars of Saint-Saëns’s Danse Macabre

Conclusion

At a time when engineers seem to be very much obsessed with close mic-ing everything that moves, it is refreshing to find a stereo microphone technique which encourages recording from a more natural perspective.

P.S.

If you are interested in more detail, I have just come across this fascinating article by Tony Faulkner himself writing in Hi-Fi News magazine in July 1981.

STC 4035 Omnidirectional Dynamic (Circa 1953)

STC4035

Designed in the early 1950’s and used extensively by the BBC, the STC4035 replaced the STC4017C which had been in service since 1938. Throughout the 50’s and 60’s the 4035, along with its Bakelite cousin the STC4032, were amongst the BBC’s primary outside broadcasting microphones. Apart from the casing and switching on the 4032 these two microphones were identical. Although both models had the same very effective wind resistant fine mesh grill, in the event of very high wind or rain the 4001.A. windshield could be added.

STC4032 and STC4035 with 4001 windshield
STC4035 with 4001A windshield
STC4017 compared to STC4035

The 4035 was much lighter and smaller than the old 4017, and although it was essentially omnidirectional there was some directionality at high frequencies.

Here is a full description and technical specification.

Below is a pricelist from the late 50’s.

N.B. In today’s money £18.10.0 would be around £520.00.

At the BBC the 4035 was used for a very wide range of tasks.

Big Ben

In the mid 50’s an STC4035 with a modified connector/mounting attachment was installed directly beneath ‘Big Ben’ in the Elizabeth Tower at Westminster. This was connected to BBC Broadcasting House and used to broadcast ‘live’ the world famous clock chimes of this huge, iconic bell. My Dad (along with the rest of the British population) always used to set his watch by the BBC chimes.

Horse Racing

In order to capture the exciting thunder of horses’ hooves and all the thrills and spills of the race, BBC Manchester Radio OBs used to place a 4035 in every jump for the Grand National.

Wimbledon.

1962. Interesting arrangement of two STC4035s with windshields.
(Photo IET Archives)

They were also used as general effects mics at many other sporting, and outdoor events, very often used to pick up atmosphere and the sound of the crowd.

Perfect for Political Speeches

British Prime Minister Harold Macmillan in 1957 (Photo BBC)
STC Dual stand for 4035

STC Dual stand.

ITV arrived in the mid-1950’s and also found plenty of use for the mighty 4035!

STC4035 in Grampian Parabolic Reflector
1967 Coltishall Airshow AngliaTV:  STC 4035 in a Grampian Parabolic Reflector. (Photo Dave Taylor).

I love the look of dedicated concentration, trying to focus the dish on high speed aircraft using only headphones!

STC4035 connection socket

The 4035 connection socket is the same as most STC microphones and requires the 4069A plug (which is still widely available).  Interesting to see the screw heads in this picture. These can be undone to separate the upper and lower halves of the microphone for repair. Normally they are covered with hard wax.

So……. What does it sound like?  CLICK HERE for audio clip.

Conclusion

If there was a competition for the world’s most boring looking, least stylish microphone, the STC4035 would definitely be in the running, with its dull grey/black finish and uninteresting shape. Also, unfortunately, unlike the ‘Apple and Biscuit’ STC4021 or ‘The Stick’ STC4037, the poor old 4035 doesn’t even have an amusing nickname! However, good looks aren’t everything and if you are simply looking for a robust ‘workhorse’ microphone with a reputation for being completely reliable, even in the most adverse conditions, then the STC4035 is definitely worth considering!

Electro-Voice RE20 Cardioid Dynamic 1968- present day.

Electro-Voice RE20.

Picking up the RE20 for the first time the expression ‘built like a tank’ immediately springs to mind. Weighing in at 1lb 10oz everything about this microphone is heavy and solid. Able to operate in conditions of extreme temperature and humidity the RE20 can also handle pretty much unlimited SPL. If I was commissioned to record an erupting volcano, or maybe a nuclear explosion from close quarters this is the microphone I would choose! In addition it also has a wide, flat frequency response, uniform cardioid polar pattern and excellent transient response all of which allows the RE20 to compete with the very best of studio condensers.    

Here below is the manufacturer’s Technical Data and Service Sheet for the RE20 

Short History Lesson.

At the tail end of the 1950’s Lou Burroughs, co-founder of Electro-Voice announced that the company was to move away from the manufacture of condensers and ribbons and concentrate on producing dynamic microphones. He believed that condensers and ribbons were too fragile and temperamental and that dynamic microphones were superior in every way. He declared ‘These are the microphones of the future’.

Throughout the 1960’s Electro-Voice developed a series of quality dynamic microphones based on their famous Variable-D design, starting with the EV664 ‘The Buchanan Hammer’ and culminating in 1968 in the now legendary RE20. The advertising clip below for the EV666 illustrates how the Variable-D design uses phase cancellation to reduce unwanted pickup from the rear of the microphone and thereby ‘create a uniform cardioid pattern at all frequencies.’ The most obvious practical advantage is that ‘proximity effect’ is pretty much eliminated. This allows the user to address the microphone from very close quarters without any unnatural rise in bass frequencies.

Electro-Voice Variable 'D'

Right from the start the RE20 proved to be an enormous hit with radio stations, recording studios, PA companies and performers. The RE20 was used for lead vocal on two albums by Stevie Wonder, ‘Talking Book’ in 1972 and ‘Innervisions’ 1973. Producer Robert Margouleff said that the RE20 helped achieve a “close, intimate sound”.  Tracks such as ‘Superstition’ and ‘You Are the Sunshine of My Life’ are outstanding classics of popular music.

Stevie Wonder with EV RE20

Impervious to Popping.

Another important feature of the RE20 worth mentioning here is the internal ‘pop’ filter. Every entrance to this mic is protected by a barrier of thick foam.  I can think of no other microphone like it! For singers, actors and broadcasters who are prone to ‘popping’ or sibilance the RE20 is the solution to the problem. Even from a distance of ½ an inch it is almost impossible to make it ‘pop’!

Electro-Voice RE20 Grill

Here is me being silly just to illustrate the point. 

Soooo…. In Conclusion.

Apart from close up recordings of plosive tongue twisters what else is the RE20 good for? Over the years it has been used for many things. Apart from broadcasting and vocals it has gained a considerable reputation on kick drum, guitar (electric and acoustic) bass (electric and upright) and brass instruments of all shapes and sizes. To be honest it is one of those very rare microphones that will sound great on almost anything!

CLICK HERE for recording with Tenor and Baritone Sax and Kick

Electro-Voice RE20 with Case
Electro-Voice RE20 Case
Image

MERRY MICROPHONES TO ALL 2021 !

Microtech Gefell PM860 Handheld Cardioid Condenser (Circa 1986)

History Lesson

In 1943, following the bombing of the Neumann factory in Berlin, Georg Neumann, along with technical director Erich Kühnast and around 20 staff, moved production 300km away to Gefell, a small town in Thuringia. This new facility, set up in an old textile mill, became known as Georg Neumann & Co/Gefell.

At the end of the war, in addition to Gefell, Neumann set up a new factory in Heilbronn making batteries, before returning to Berlin to set up Georg Neumann GmbH (today owned by Sennheiser). Meanwhile, the original staff in Gefell continued making high quality microphones. Gefell was now in the GDR and, with the building of the Berlin wall in 1961, all links between East and West were severed. In 1972 the Gefell factory was taken into public ownership by the East German government. The company was renamed VEB Mikrofontechnik Gefell.

And here’s where it gets interesting……….     

During the Soviet the era the company formed important research links with RFZ (GDR radio and TV) and the NIFKI institut (for film and TV) in Moscow. This meant that the company could share the very latest developments in Soviet technology. During this period the team at Mikrofontechnik Gefell worked on a number of significant projects, financed by the GDR government. These included the development of high powered lasers, solid-state microphone amplifiers, and the production of chromium plated ceramic diaphragms under high pressure.

Eventually, with the collapse of communism and the fall of the Berlin wall in 1989, Georg Neumann claimed back the Gefell factory. When the technical staff from Berlin started looking at the microphones produced in Gefell they were shocked to find technology more advanced than anything found in the West!

Mikrofontechnik Gefell PM860
Mikrofontechnik Gefell PM860   Showing Bass roll-off and 10db pad switches

Back in 1986 when Mikrofontechnik Gefell designed the PM860, high quality handheld condensers were something of a rarity. The chrome plated ceramic capsule with its spring shock mounting was cutting edge technology. Even today the capsule design of this microphone remains unusual and distinctive.

Mikrofontechnik Gefell PM860   Chrome plated ceramic capsule with its spring shock mounting.
Mikrofontechnik Gefell PM860   Chrome plated ceramic capsule with its spring shock mounting.

The grill basket is also sophisticated, being made up of several layers of fine wire mesh, providing excellent wind screening and blast protection.

Mikrofontechnik Gefell PM860   Grill

The quality of the PM860 is such that in 2010 Microtech Gefell chose to reissue it. The ‘look’ and specification of the new model is exactly the same as the original, with the exception of the power supply which is now 48v phantom on an XLR, instead of having a separate power unit with a multi-pin connector.

For comparison

Here is the Tech Spec for the original version

And this is the more recent version 

New ones are still available from several outlets for around £1500. Considering that for the same money you could purchase 15 Shure SM58s, the PM860 is definitely a microphone for the discerning professional performer!

So What Does It Sound Like? 

CLICK HERE for short voice comparison with Neumann U87i

CLICK HERE for vocal track.

In Conclusion

High quality microphone production has continued at Gefell uninterrupted since Neumann & co first arrived in 1943. Although today the name of Neumann no longer appears on the company products the tradition of excellence continues. Microtech Gefell is owned and run by descendants of the original staff and Gefell microphones are widely recognised as being amongst the finest available anywhere.

P.S.

Here is a Learning Experience!

Microtech Gefell PM860

When my lovely PM860 arrived from my usual supplier (ebay), I plugged it in straight away. However, I was horrified by the sound that assailed my ears! My voice was accompanied by a dreadful cacophony of cracking, whistling, rustling and similar unwelcome noise! My immediate impulse was to send it straight back to the seller. However, once I had calmed down and given it some thought, it occurred to me that even if I sent it to Microtech Gefell for servicing it would still have cost me a lot less than a new one. So that was what I planned to do.

Meanwhile a couple of weeks went by. The microphone was sitting on my desk in my warm dry living room. I plugged it in again and was surprised to find that most of the noise had disappeared! At this point it dawned on me that the most likely cause of the problem was damp. Perhaps in transit, or maybe it had previously been stored somewhere damp. Anyhow, I placed several bags of silica gel in the case with it and left it a few more days. When I next plugged it in the noise had gone completely and it sounded GREAT! So my new plan is to simply carry on using it and to keep it stored in suitably dry conditions. RESULT!

The MEMS Microphone. The Biggest Selling Microphone Ever!

History lesson

If we go back 100 years or more, every telephone on the planet transmitted speech via a carbon microphone. This was a small container of carbon granules polarised by a low voltage and having a diaphragm at the front. As the diaphragm vibrated, the granules were subjected to varying pressure causing small changes in the voltage. This signal passed through a transformer and went off down the telephone line to be picked up by the receiving phone. Carbon microphones continued to be used in telephones all way up to the 1980s. Millions upon millions of carbon microphones were in daily use right across the world! The audio quality was a bit shit to say the least, with plenty of crackling and unwanted noise, BUT……. speech was intelligible, they were dirt cheap to manufacture AND they were utterly reliable over many years of use.                                                                             

End of history lesson.

Scroll forward to the present day.

Exit the carbon mic, enter the MEMS mic. Today, mobile phones, laptops, tablets and other portable communication devices are everywhere. Most of these devices contain at least one MEMS microphone. Recent sales figures from US manufacturer Knowles Acoustics show sales for their SiSonic silicon based MEMS microphones in excess of 1 billion units!! 1 Billion units!! That is a lot of undercover microphones.

So What Is a MEMS microphone?

Knowles SiSonic MEMS microphone SPU0410LR5H-QB

A MEMS microphone is manufactured using micro-electromechanical systems processing techniques. These microphones are etched into a semi-conductive silicon wafer. A pressure-sensitive moveable membrane (diaphragm) is etched behind a stationary perforated backplate. The perforated stationary plate and the diaphragm act together to form a capacitor (similar in design to a condenser microphone). The MEMS mic is designed to be mounted on a circuit board along with preamp and other application specific components.

MEMS microphone motor

Sketch of a MEMS microphone motor (not to scale). The diaphragm has a thickness of 1 µm, the gap between the backplate and the diaphragm is 4 µm, the diameter of the perforations in the backplate is 10 µm, and the thickness of the backplate is 2 µm. The distance across the motor from support post to support post is 590 µm. Sketch courtesy of Knowles Electronics.

Just like the carbon mics of the last century these MEMS microphones are extremely cheap to produce and are highly reliable. However, what is very different is the audio quality. The Knowles SiSonic MEMS microphone pictured above has a near flat frequency response from 100Hz to 10kHz which is pretty good for such a tiny, inexpensive, microphone. (<£1)

Knowles SPU0410LR5H-QB MEMS mic frequency response 100-10kHz

But what is really mind blowing is the Ultrasonic response!

The graph continues on up to 80kHz !!! (and beyond)

Knowles SPU0410LR5H-QB MEMS mic frequency response 10kHz-80kHz

This brings me to my current project Ultrasonic Recording,

This MEMS microphone is perfect for recording the activity of bats, amphibians, crickets and other wildlife whose calls are in the ultrasonic range high above our rather limited human hearing.

AudioMoth https://www.openacousticdevices.info/ is a miniature recording device currently being developed to record and collect data on the activities of a variety of wildlife. The latest version of AudioMoth uses the Knowles SPU0410LR5H-QB MEMS microphone featured above. 

Open Acoustic Devices AudioMoth

So what does it sound like?

CLICK HERE to hear ‘BATS with Guitar’ (Yes, you heard right! )

N.B. The BATS have been slowed down to bring them within the range of human hearing

Conclusion

Hidden away out of sight on a circuit board inside a mobile phone or a laptop or some other electronic device the MEMS microphone is never going to gain any awards for stylish good looks. Even though its audio quality is amazing (considering its price) it isn’t about to replace the Neumann U87 in the recording studio! Nevertheless it is an extremely versatile tool that will be with us for many years to come and is without doubt the biggest selling microphone ever.