The Parabolic Microphone.

In the Beginning.

The notion of using a parabolic reflector to pick up sounds from afar has been around for many years.

With the advent of aerial warfare in the First World War, the British military started developing acoustical devices to provide early warning of incoming enemy aircraft. The first ‘sound mirror’ was erected in Maidstone in April 1915. During the 1930s, in the run-up to World War 2, a number of these enormous concrete parabolic reflectors appeared along the South coast of England and at other strategic locations. The largest of these structures could detect aircraft at a distance of 25 miles. However, the whole project was abruptly abandoned in 1938 with the invention of Radar!

WW1 30ft Sound Mirror

The listening ‘trumpet’ seen on this dish could be rotated to find the strongest signal. This would enable the listener in the control room beneath the dish to calculate the direction of the incoming aircraft. The information could then be relayed to anti-aircraft batteries.

Parabolic Ears

A ‘stereo’ device like this could be used to pick up activity in enemy positions and provide early warning of attack. (That is if you could hear anything above the sound of your mates laughing their heads off!)

The Parabolic Microphone

In the post war years with the rise of television and the increasing popularity natural history broadcasts on both wireless and TV, sound recordists were quick to adopt the parabolic microphone i.e. an omni or a cardioid microphone, mounted facing inwards, at the central focal point of a portable parabolic dish.


Parabolic MIcrophone

The author recording birds in the trees down at the bottom of the garden.  CLICK HERE to share in the joy!

A parabolic reflector has one significant advantage over other sound pick-up devices: it is a noiseless acoustic amplifier. The frequency response and polar pattern are a function of the size of the dish used. The enormous concrete military dishes of the 1930’s were often 30ft in diameter or more, enabling them to detect the lowest frequencies of an aircraft engine over huge distances. For the modern wildlife recordist a somewhat smaller portable dish is something of a compromise! For a narrow forward beam of 10 degrees a 60cm diameter dish gives around 14db (x5) gain to frequencies above 500Hz. A 1m dish will give 20db (x10) gain to frequencies above 300Hz. The forward gain of a reflector is defined as the difference in output level between a microphone which is reflector-mounted compared to the same microphone unmounted. Even with a modest sized reflector, the on-axis sound of the chosen subject is greatly magnified without adding any of the hiss and hum associated with electronic amplification. However, given the narrow beam characteristics of the dish, one thing that the recordist should bear in mind is that if the subject moves off axis the tonal quality of the sound will change. This can be difficult if for instance the subject is moving around in a group of birds. For that reason I would suggest that the parabolic dish is at its best when recording an isolated single subject.

Frequency/ Directional Response Plot for a typical parabolic reflector for wildlife recordingParabolic Dish Frequency plot

Using an unmounted microphone there are many wildlife recording situations in which it is simply not possible for the sound recordist to get close enough to achieve a good signal to noise ratio. As you creep up with your microphone the subject simply flies off or runs away! ……..Or in the case of dangerous wild animals it may be the sound recordist who does the running! The parabolic dish enables the sound recordist to record from a safe distance without risk of disturbing the subject or getting eaten!

One of the most common problems with wildlife recording is that quite often the perfect recording opportunity comes up without warning. Animals and birds are not predictable. Hence, my minimalist, rapid response kit, illustrated below is light, portable and very fast to set up. I can be in record in a matter of seconds!

The Parabolic Microphone. Minimalist Wildlife Sound Recording Kit

  • Extremely light weight, flexible, 50cm plastic parabolic dish available from new UK company innercore
  • Aluminium handle on the back which can also be screwed on to a tripod
  • Simple microphone mount marked at the focal point.
  • HMN Sound MicroLav. N.B. to prevent wind noise a Rycote Furry windshield is recommended. (Not pictured.)
  • M-Audio MicroTrack II set to record in mono at 96kHz 24bit.
  • M-Audio in-ear headphones with industrial ear defenders over the top for isolation.

Walking by a local lake the other day I came across a small flock of Canada geese about 40ft away quietly pottering about on the grassy bank. Suddenly one of them started squawking/honking. I started recording and within a few seconds it flew high into the air and passed straight over my head. On the recording the strange creaking sound of the bird’s wings and the movement of air can be clearly heard. It sounds close up, even though the bird is at least 30ft above me. It then flies round the lake and lands back with the others and carries on honking very loudly. Definitely not a bird you would want to get close to! Would probably make a good guard dog!                                                                           CLICK HERE to take a listen.

Other Uses for the Parabolic Microphone.

When listening to sporting coverage on radio or TV you may have enjoyed the additional excitement of hearing the ball striking the bat or the racket. You may hear the close-up thunder of the horse’s hooves in a race or the grunts and shouts of a rugby scrum and…… Not a microphone in sight!

In Conclusion.

My purpose in writing this post has not been to advertise the merits of a particular set of equipment but merely to suggest some of the possibilities and fun to be had recording sound using a parabolic dish.

6 TODAY! Blog Birthday Party!

Blog Birthday Party 2018

I started my blog today in 2012.  Some of the guys are having a party to celebrate!

In April 2012 I had the princely average of 3 views a day. So far today (3pm) there have been 154 views!  In all 135,256 since I started!  Many thanks to all my visitors.

P.S. It turns out that microphones don’t eat cake……… so I might just have to eat it all myself!

Mélodium 76A 1960’s / 70’s

Looking like a cross between a Van Gogh Sunflower and a pepper pot, the Mélodium 76a is a shining gem of chrome and aluminium. A classic of French design!

Melodium 76A Front Grill

In the 1960’s Mélodium developed a variety of modular parts and accessories to give their range of microphones greater versatility and customers more options.

The basic 76A microphone (head) came with a choice of 10 ohms or 200 ohms impedance.

Melodium 76A Head

The mic could be used plugged straight into the cable. (Great for harmonica players!)

If required this handy plug-in transformer converts the 76A from 200 ohms to Hi-Z.

Melodium 76A Transformer

There was also a choice of handles.

Melodium 76A Detachable handle

Melodium 76A with 314 Handle

In this 1970’s Mélodium Catalogue (below) the technical details of the microphones are presented along with a full range of parts and accessories, including goosenecks, tall stands, short stands, table stands and a large selection of adapters, switches and transformers. It is a very comprehensive selection, to cover every possible application.

CLICK Here for MelodiumCatalog

Sadly these days it is hard to find much information about Mélodium. Even in its heyday the company was little known outside of the French speaking world. By the end of the 1970’s Mélodium were no longer in business. Probably wiped out by the superior German and American competition.

Melodium 76A

Finally

Having finished re-soldering all of the joints in my eBay ‘bargain’, I just need to plug it in and find out what it sounds like!

CLICK HERE for Sound clip of Voice and Blackbird in the garden.

Mélodium 76A 1960’s / 70’s Construction Kit!

Mélodium 76A Construction Kit

When the previous owner mentioned in the description that there were ‘a few wiring issues’ with this vintage French PA microphone he wasn’t kidding! (It looked perfect enough in the eBay photograph!)

Was that why it was so cheap, and no one else bid? Hmmm…….

So now for a bit of fun wiring it back together!

I’ll report back if it by some miracle it works!!

P.S.  Just to make things a little more exciting Mélodium have their own plugs and sockets that only fit Mélodium microphones. They are made so that the pins can be moved about in various configurations up to 5 pins! This 431 socket will be 3 pin…… when I get them in the right holes!

Melodium 431 plug

P.P.S  Just noticed that there should be a rubber gland inside the knurled ring at the top!

The Viking(s). Extinct Audio’s BM9 Matched Stereo Pair…… Following on from my post in January.

The danger in buying an Extinct Audio BM9 ribbon microphone is that very soon you will want a stereo pair! When Stewart Tavener at Extinct offered to lend me a second one to ‘try’ he knew exactly what would happen! ( Yorkshire cunning!)  It didn’t take long before I hit the PayPal button. So I now have a beautiful matched pair!

Extinct Audio BM9 Matched Stereo Pair

The mics are coincidentally mounted, vertically one above the other and set at 90 degrees. (Classic Blumlein) I have used Rycote InVision 044901 Universal Shock Mounts as these make it really fast and easy to position the mics. They also provide the best possible isolation, and there is no chance of the mics falling out! The magnets in these microphones are seriously heavy and would make a considerable impression landing on the performer’s head!

The recording clip below of saxophone virtuoso Lydia Kenny would present a considerable challenge for any pair of microphones. The dynamic range is huge. It is packed with fine detail of tone and texture, from the delicate phrasing of the piano accompaniment to the rapid articulation of the blistering runs on the saxophone at full volume. The way that the acoustics of the hall support the music is also very subtle.

Having worked a great deal with jazz and rock ‘n’ roll over the years I had never previously been a fan of classical saxophone, but this excerpt from Lydia’s performance of ‘Fantasie’ by Jules Demersseman is quite simply an irresistible tour de force of 19th century technique and musicality. Demersseman was a friend of the inventor Adolphe Sax and the piece was published by Sax.

Pittville Pump Room in Cheltenham (UK) had its heyday in the mid-19th century and its spacious acoustic and glorious Regency architecture is the perfect setting for this recording. The Extinct Audio BM9 crossed stereo pair flown below the chandelier also look very cool!!

CLICK ON PIC  to listen

 Lydia Kenny Alto Saxophone accompanied by Damian Kenny Piano.
Lydia Kenny Saxophone with Damian Kenny Piano

Lydia Kenny is the winner of Gloucestershire Young Musician of the Year 2018

The STC4001B Acoustic Baffle for the STC4021 (Apple & Biscuit) circa 1935.

The very first post that I wrote for this blog back in 2012 was about the STC4021 (Apple & Biscuit). Still one of my favourite microphones.  I even made a YouTube video to go with it! In the course of the video I mentioned the STC4001B Acoustic Baffle. According to the STC brochure this could be purchased to modify the frequency response and directionality of the microphone. These days the 4001B Acoustic Baffle is very hard to find. So imagine my surprise when a brand new old stock 4001B (still in the box) appeared on eBay. 

So I thought I had better ‘Buy it now‘ and make another video to celebrate the occasion!

 

THE VIKING, EXTINCT AUDIO’S BM9 RIBBON MICROPHONE 2018.

The English county of Yorkshire has a long and illustrious history of steel manufacturing and precision engineering. Based in York, Extinct Audio are an enthusiastic new company offering beautiful, high quality, hand-built ribbon microphones.                                                                                                                            .The Viking Extinct Audio's BM9. The Box...The Viking Extinct Audio's BM9.

Although the design and styling of The Viking, Extinct Audio’s BM9 pays tribute to the legendary Danish ribbon microphones of the 1950’s and 60’s, it has a unique British character and tone all of its own. The transformers are hand wound at the workshop in York and the ribbons are individually fitted and tuned by Dr Stewart Tavener who has more than a decade of experience restoring and repairing 1,000s of vintage ribbon microphones. The Viking also features an extremely strong magnetic field, giving high output and low noise.

The Viking Extinct Audio's BM9..The Viking Extinct Audio's BM9. Back view.

My own microphone collection divides up into 4 distinct categories:-

  1. Microphones with historic significance or a special place in the development of audio technology; e.g. Marconi-Reisz, STC4017.
  2. Microphones which are good for particular purposes; e.g. AKG D112, Sennheiser e945.
  3. ‘Oooo shiny!’ Microphones purchased for no good reason other than they look cool! (Though occasionally they turn out to be useful!) E.g. Electro-Voice EV664, EV644.
  4. Serious workhorse microphones that will produce fantastic results in a wide range of situations; e.g. AKG C414, Oktava MK-012.

I must confess that when I opened that gorgeous wooden Viking box my instinctive reaction was category 3……. ‘Oooo shiny!’ The nickel finish on these mics is superb. They really look and feel great.

Over the last few weeks I have had a number of recording opportunities to try out The Viking on a range of acoustic instruments. Here below are links to a selection of sound clips from these sessions.

CLICK ON EACH to listen.

  1. Vocal and Tenor Saxophone. Peter Gill and Edi May.
    Peter Gill Vocal
  2. National Steel Guitar and Vocal. Pete Atkin.Pete Atkin. National Steel Guitar and vocal
  3. Anglo Saxon Lyre. Andrew Glover-Whitley.Anglo Saxon Lyre Andrew Glover-Whitley
  4. Chinese Walking Stick Flute. Andrew Glover-Whitley.Andrew Glover-Whitley Chinese Flute Walking Stick
  5. Breton Bombard. Andrew Glover-Whitley. (blowing this thing can lead to burst blood vessels!)Andrew Glover-Whitley. Breton Bombard in Bflat
  6. Rock Flute. Andrew Glover-Whitley.Andrew Glover-Whitley Rock Flute
  7. Tenor Saxophone. Edi May.Edi May Tenor Sax

In Conclusion. 

The Viking, Extinct Audio’s BM9 is a superb, hand built, ribbon microphone, in the finest tradition of Yorkshire craftsmanship and engineering.  It produces an extraordinary level of fine detail. The low end is rich and full. It is a joy to work with and has definitely joined category 4 in my collection……… though I still can’t help going ‘Oooo shiny’ every time I open the lid of the box!

For more information about Extinct Audio visit: – https://www.extinctaudio.co.uk/microphones/

P.S.  Buying a Stereo pair was inevitable!

Extinct Audio BM9s. My custom Stereo Mount under construction

Custom mount under construction. using a pair of Rycote Universal Shock Mounts.