Category Archives: Microphone techniques Ancient & Modern

AKG C747 More Than Just A Podium Conference Mic.

AKG C747

First introduced in 1987 the AKG C747 was originally designed for ‘unobtrusive speech applications when mounted on a podium or lectern, or for teleconferencing activities’.  From this somewhat uninspiring start, these days the C747 is widely acknowledged as one of the most versatile microphones AKG ever produced!

Just a glance at the tech spec tells you that this was not a microphone simply doomed to deliver the Chairman’s annual report!

  • Smooth frequency response from 30Hz -18kHz.
  • Rapid transient response produced by tiny, low-mass, capsule.
  • Tight hypercardioid polar pattern, giving excellent separation.
  • SPL rating of 133db.
  • AKG C747 Frequency Response GraphAKG C747 Polar Pattern

It didn’t take engineers long to realise that this neat, pencil sized miniature shotgun microphone has many uses away from the conference hall!

AKG C747 Matched Pair

I recently acquired a well-matched pair of old C747s and it occurred to me that although advertised as having some ‘shotgun’ characteristics, these neat little condensers do in fact behave pretty much the same as any other hypercardioid microphone.  I therefore wondered how they would get on as a crossed stereo pair.  I have seen them occasionally used like that in a conference speech setup, but never recording a large symphony orchestra! (Frequently used as spot mics but certainly not as the main pair!)  So here goes …………

CLICK HERE for Symphony Orchestra sound clip.

The mics were crossed at 65 degrees (at the capsules) and positioned on a tall stand about a metre behind the conductor. N.B. To get the full effect of this recording you need to download it in full resolution and play it on speakers at the sort of volume that will really annoy your neighbours!

AKG C747 Crossed pair at 65 degrees

Here below are the Tech specs for both the AKG C747 and the current model the C747 11.  It is interesting to note that in the C747 11 literature various instrumental applications are also illustrated. (guitar, saxophone, snare, drum) The newer model also has a slightly different frequency response, more tailored towards speech. Either way these are fabulous, unobtrusive, little mics that will blend seamlessly into almost any situation!

C747-manual

AKG_C747_Service_Documentation

AKG_C747V11_Manual

AKG_C747V11_Polar_Patterns

AKG_C747V11_Cutsheet

N.B.  The Hi-Pass filter on these mics is hidden away in the XLR plug (also containing the mic preamp) I included this last photo because, in conversation with the previous owner, he told me that he never realised that the 747 had a hi-pass switch!! When working close up he ‘Always found them a bit too bassy ‘ !

AKG C747 Hi-pass filter

 

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Oktava MK-012 Matched Pair. My favourite Stereo Microphone Techniques.

If you are looking for a small diaphragm condenser microphone that will add extra sparkle to your high end, more presence to your mids, and greater weight to your bass………… then the Oktava MK-012 is definitely not for you!! However, if you are looking for an accurate microphone which simply reproduces what it hears, then the Oktava MK-012 is definitely worth considering.

Oktava Mk012 Matched stereo pair.

I bought a matched stereo pair about 10 years ago (direct from Oktava) and they have earned me more money than any other mics I own! I have used them on hundreds of live shows for many different purposes, including drum overheads, hi-hat, Latin percussion, grand piano, acoustic instruments, and as ambient mics. However, it is on classical music recording that they really excel. I have used them in a variety of stereo configurations and in each case they provide a clean accurate account of the performance, capturing the finest nuances of timbre and texture.

Here below are my favourite stereo microphone techniques illustrated with the Oktava Mk-012s  

These microphones have not been ‘modified’ in any way and the recordings linked below have not been EQ’d or processed. Although the streaming quality is reasonably good, for more detailed listening most of the tracks can be downloaded off Soundcloud in their original full resolution wav format.

Oktava MK012 Crossed Pair at 90 degrees

Near-coincident X-Y crossed pair at 90 degrees gives a phase-coherent stereo image with excellent positionality. The angle between the mics can be altered to suit the width of the subject and the relative distance of the mic placement. Particularly useful for chamber music and small ensembles. Cardioid or hyper-cardioid capsules can be used.

Oktava do now make a dedicated figure of eight capsule. In which case a pair of those would be another option.

CLICK HERE for sound clip of wind quintet.

N.B. The shock mounts are Rycote InVision  INV-7   and (below with piggyback clips)


Oktava MK012 M-S pair

M-S pair using the Oktava figure of eight adapter which utilises 2 cardioid capsules back to back, in opposite phase. The Mid mic can be cardioid, hyper-cardioid or omni. As with the X-Y array, the M-S pair produce an accurate phase-coherent image. Works exceedingly well on wide subjects such as orchestras and choirs, particularly when the mic position needs to be close to the performers. Has the additional advantage that the relative levels of the mics can be manipulated in post-production. (Reducing the level of the Mid mic and raising the Side channels widens the image. Increasing the Mid and lowering the Sides ends in Mono!)

CLICK HERE for sound clip of male voice choir with brass.


Oktava MK012 ORTF Pair

ORTF pair. Cardioid capsules set at 55 degrees and spaced 17 cm apart. Emulating the inter-aural time differences between our ears this configuration produces a detailed but somewhat more diffuse stereo image than the previous examples. This array produces a good sense of depth and perspective. Many engineers argue that ORTF pairs give a more ‘musical’ sound. (?) Excellent for choirs and orchestras.

CLICK HERE for orchestral sound clip


Oktava MK012 Jecklin Disc

The Jecklin Disc takes the principles of the ORTF pair one step further and introduces a foam and fur covered 12”disc between the microphone ‘ears’, emulating the reflective, and shading characteristics of the human head. This array utilises a spaced pair of omni capsules angled slightly outwards. The Jecklin disc with a pair of MK-012s produces a remarkable sense of ‘being there’. Excellent in situations where, along with the performance, you want to capture the acoustics of a great sounding hall or church. Good with subjects of any size and can be positioned at a distance without losing ‘presence’.

CLICK HERE for sound clip of violin concerto

CLICK HERE for sound clip of choral concert

CLICK HERE for sound clip of A Cappella singers in small church

 Anecdote

Some years ago whilst recording a live performance of Monteverdi Vespers, I was somewhat taken aback at the start of the concert by the following occurrence. As the choir processed in from the back of the church, they suddenly started singing!! Arrgh! With almost any other array this would have been a recording disaster. As it was, the pick-up of the Jecklin disc with its MK-012 omnis is pretty much the same from behind! The choir processed down the length of the church and filed past on either side of the mic stand and took their positions in front still singing! Sounded great!


Response graphs

One thing I particularly liked about my MK-012s when they arrived, was the inclusion of individual printouts of the response characteristics of each of the 6 capsules. Below is the printout comparing the matched frequency response of the 2 cardioid capsules, complete with handwritten details!

Oktava MK012 Frequency Plot for individual cardioid capsules.

Tech Spec for Oktava MK012

Oktava MK012 Wooden Box

P.S.

Having provided a neat wooden box it is commendable that Oktava didn’t waste money on fancy, glossy, printing on the packaging! No hype, no bullshit, no celebrity endorsements, just a great sounding pair of mics !

Oktava MK012 Fancy Packaging

Shure 430 ‘Commando’ Controlled Magnetic / Controlled Reluctance Microphone (Circa 1957)

Shure Model 430 CommandoShure 430 Commando grill

The Controlled Reluctance microphone (aka Controlled Magnetic) was developed by Shure during World War 2 to fulfil the need for a battle announce microphone that could operate reliably at extremes of temperature and humidity. (Subsequently also perfect for Korea and Vietnam!)

Although the Controlled Reluctance design was in some respects similar to a conventional dynamic in other ways it was significantly different.

The 2 diagrams below illustrate the differences.

  • DYNAMIC MICROPHONEDynamic-moving-coil-diagram
  • CONTROLLED RELUCTANCE/MAGNETIC MICROPHONE (2 slightly different versions)Controlled Reluctance Microphone Sectional Diagram

Here, in response to an email enquiry, is an explanation from Shure of the working of this microphone

On 3 May 2017 15:06, “Shure Europe” <support@shure.eu> wrote:

Response By Email (Michael P) (05/03/2017 09:06 AM)

Controlled reluctance is a variation of a dynamic mic.  The controlled reluctance mic diaphragm connects to a small lever made from ferrous material.  The other end of this lever is positioned inside of a stationary coil of wire.  Surrounding the coil of wire is a stationary magnet.  As the ferrous lever is moved by the mic diaphragm, the lever disturbs the magnet field.  This induces an AC signal (the audio signal) in the coil of wire.

Answer Link: Difference between controlled reluctance and controlled magnetic

This type of mic was originally designed for military applications.

Michael Pettersen

Shure Historian

 


2 pin Ampenol Connector

If you buy a 430 make sure it comes with one of these as 2 pin Amphenol connectors are hard to find.

The CR/CM elements have a high output (making them suitable for transmission over large distances) and require no additional transformer. They are therefore cheaper to manufacture than a conventional dynamic.

After WW2 Shure introduced several models for the civilian market, including the famous Green Bullet (still popular with harmonica players to this day). These were mostly budget PA mics intended for speech applications such as paging and announcements. Whilst not being particularly noted for high quality audio, their main selling points were cheapness and reliability. It is therefore not hard to see why these sturdy, affordable mics soon found favour with musicians and singers.

Apart from being highly profitable, Shure’s military communications contracts had the additional spin-off of enhancing a lasting reputation for reliability. Indeed, the company have often boasted that all of their products are tested to military standards (MILSPEC).  Even though the Model 430 was made for the civilian, domestic market it nevertheless trades on its military heritage with the name ‘Commando’ and it’s distinctive, camouflage green head!

Shure 430 Commando head

Data Sheet for the Shure Commando series.:-     us_pro_415_ug

Shure Microphones  :-  1957 Catalogue

 430 Commando Original Box

So what does it sound like?  CLICK HERE for a short clip of spoken word and Blues Harmonica.

 

Dynamic Microphones for Classical Recording?!

Oktava MD-186 ORTF pair

In the late 1950’s Electro-Voice ceased production of both ribbon and condenser microphones. In an article in his series ‘MICROPHONE FACTS for the operating engineer’ Electro-Voice founder Lou Burroughs explained the decision and presented reasons why dynamic microphones were, in every way, superior. The feeling at Electro-Voice was that ribbons and condensers were too fragile and prone to failure and that dynamics were solid and reliable and sounded better. Towards the end of the article (referring to dynamics) Burroughs declares that ‘These are the microphones of the future’.

Today, although dynamic mics are still revered for their robustness and ability to handle high SPLs they are not generally considered to be sonically superior to all other microphones! Indeed, I can’t imagine many engineers taking a pair of dynamics out to record an orchestral concert of classical music instead of their usual selection of condensers and ribbons.

Compared to condensers Burroughs claimed that dynamics have a ‘smoother high frequency response’ and so, here (by way of an experiment) are a  couple  of clips from an orchestral concert I recorded recently using a pair of Soviet Era, Russian, Oktava MD186 dynamics! I was simply curious to see if Lou Burroughs maybe had a point?

CLICK HERE for End of Beethoven’s Fifth

CLICK HERE for Mozart Piano Concerto

Oktava MD-186 ORTF pair 2

Electro-Voice EV642, 643, & 644 Cardiline Microphones , (circa)1960

Ever since the advent of the ‘Talkies’ sound technicians have struggled to pick up speech in motion pictures with sufficient clarity. For many years the problem of getting the microphone close enough to the performers without it being in the camera shot was a constant challenge!  On the other hand if the mic was too far away the sound was often ruined by the pickup of unwanted surrounding noise.

Seeking to address this problem, in October 1959 Wayne A. Beaverson of Electro-Voice filed for a patent on a new type of directional microphone which could be successfully operated at a distance from the sound source.  At low frequencies this microphone exhibits the directional characteristics of a cardioid mic, with excellent rear rejection. As the frequency response rises it becomes a line mic with considerable attenuation of unwanted sound from the sides. Thus the new ‘Cardiline’ design provides excellent directivity right across its operating frequency range.

Electro-Voice Patent for Unidirectional Microphone 1963

The success of the new microphone was such that in 1963 Electro-Voice received an Academy Awards “Oscar” for the development of the model 642 Cardiline, The award, in part, read “To Electro-Voice for a highly directional dynamic line microphone… capable of picking up sound in situations where a microphone cannot be placed close to the sound source and where unwanted sounds are to be discriminated against.”

Although the Academy Award went to the 642, the microphone drawn and described in the original patent application was in fact its close cousin the EV644. At this point you might be wondering about the 643?  Well ……… The 643 was pretty much the same as the 642 except in one significant detail ……… it was just over 7 feet long!  All three of these mics were of the Cardiline pattern but they were aimed (excuse the pun) at different areas of the market. As we know, the 642 was tailored very much for the film and TV industry and came with an elastic mount for attaching to a boom.

EV642 Advert 1963

EV643  Advert

Electro-Voice_643 Advert

electrovoice_643_2

Although extravagant claims are made for the mighty 643 in the advert above, I suspect that this mic was in fact quite awkward and unwieldy to use (even sighting along the barrel!!) It is certainly hard to find any fond recollections of it. I came across one report from some poor sod who once spent an afternoon standing on the roof of a football stadium trying to follow the ball round the field!! Anyone who has ever operated a theatre follow spot will appreciate just how ludicrous that must have been!

Which leaves the 644. (My latest eBay bargain!)

electro-voice-ev644

Designed for use on stage, in theatres, auditoriums and churches,  the EV644 Sound Spot came with a microphone stand mounting and was finished in classic Electro-Voice chrome. You could also buy it with a dull matt paint finish,(non-reflective under lighting), but why do that when the chrome version just looks so rock’n’roll cool !

Allied Catalogue 1960

List Price $110. A bargain at $64.68 ! (Not cheap in 1960!)

ev644-back-end ev644-body-and-stand-mountev644-end-grillev644-original-box-insideev644-original-box

CLICK HERE for Voice recording at a distance of 12ft

CLICK HERE for Glockenspiel Recording

In Conclusion

The 1963 patent shown above acknowledges a number of earlier inventions relating to directional microphones. In particular the patents of Harry Olson dating back to 1939. However, the earlier inventions, (mostly involving complex arrangements of multiple tubes of differing lengths), were awkward and cumbersome. In contrast, Beaverson’s Cardiline microphone, using a single multi-path tube feeding a single cardioid capsule, was an uncomplicated work of genius. It was both effective and easy to use.

To this day the elements of Beaverson’s patent can to be seen in shotgun microphones all over the world.

Below are the Techincal Specification Sheets for all 3 microphones.

Electro-Voice 642 Spec Sheet

Electro-Voice 643 Tech Spec.

Electro-Voice 644 Tech Spec

Experimental Line Array Microphone

making-line-array-mount

Improvising the mount for a 4 Element Line Array Microphone.

line-array-microphone

My basic 4 Element Line Array Microphone.  (Using 4 x Omnidirectional Karma K-Micro Silver Bullets)

shure-m268-front-panel

A handy little pre-amp for my line array. A Shure M268 4 x channel Mono Microphone Mixer. Surprisingly clean-sounding for its age!

Line array theory has been around since the 1930’s. In the 50’s and 60’s basic line arrays were very popular in the form of the column loudspeaker commonly used for PA. These days we are used to seeing massive line array speaker systems flown above the stage at festivals and concerts.

On the other hand the line array microphone is a rare breed and the few that are around, such as the impressive Microtech Gefell KEM970, tend to be expensive. The KEM970 is around £10,000.

In common with the shotgun microphone, the line array is a phase-reactive device. Unlike the shotgun where the on-axis position is down the length of the interference tube, with the line array the on-axis position is side-on at 90 degrees to the vertical column. Sound arriving at 90 degrees will be in phase at all of the capsules. The electrical output from each capsule will be identical and therefore additive. Sound arriving off-axis will suffer varying degrees of phase cancellation, depending on the frequency and the angle of incidence.

The polar pattern of a line array microphone is therefore wide in the horizontal plane and narrow in the vertical, getting narrower with rising frequency. This enables the mic to pick up over longer distances whilst rejecting mid and high frequency sound arriving off axis ( ie below and above.)

N.B.The longer the array (ie the more elements in the line) the lower the frequency at which it starts to be effective.

line-array-microphone-polar-pattern

Polar Plot at 1kHz

Below about 400Hz my 4 element model becomes increasingly omni-directional.  In this respect it is once again  similar to a shotgun.

Over the next few months I am planning a number of experiments to explore how this array will behave and to see what practical applications I can find for it!  I’ll report back…………..

.

ASTON ORIGIN (2016)

It is not often that I buy anything simply on the strength of the advertising, but in the case of the Aston Origin that is exactly what I did! In fact worse than that I bought two! Aston Origin Out of Box As a rule when you make this kind of impulse purchase, the goods arrive and you are doomed to disappointment. However, on this occasion it turns out that Aston microphones are as good in real life as they look on paper and on the website! Every aspect of the product has been carefully considered and designed from the ground up, everything from the unique flexible grill to the eco-friendly packaging.

At the present time the myriad of competitors  in this price range are mostly derivatives of older designs, often vaguely resembling particular vintage Neumann or AKG models. Aston Microphones have launched into this rather tired and jaded market place with product that is radically different.

Designed and built in the UK the Aston Origin not only has eccentric good looks, but it also boasts a distinctive ‘British’ sound. A sound shaped by a panel of 33 well known UK producers and recording professionals, who listened to every element of the audio chain, and by a lengthy process of elimination, chose the very best sounding components. For the full story and technical specifications visit: – http://www.astonmics.com/

The stand mounting options are either the very classy custom Rycote InVision shock mount (left) or simply screwing the mic straight on to the stand.(right)

The stand mounting options are either the very classy custom Rycote InVision shock mount (left) or simply screwing the mic straight on to the stand.(right)

My only criticism of screwing the mic straight on to the stand is that whilst this is quick and easy, it is not always possible to manoeuvre the mic into exactly the right place.

Below is my homemade rotating knuckle joint which allows the mic to be moved into any position whilst screwed directly to the stand.     It is made from the top piece of an old camera tripod. Using Milliput (which sets rock hard) I glued a 3/8 inch thread adapter into the base.  Then over the screw which would normally hold the camera, I glued a 3/8 inch stand adapter to hold the mic. The ball-joint, which can rotate in any direction, is fixed by screwing down the chrome locking ring.

Rotating Knuckle Joint for Aston Origin

So What Does It Sound Like?

CLICK HERE for Rain Stick transient response test

CLICK HERE for Saxophone.

CLICK HERE for Piano and Orchestra

Neumann U87Ai  v  Aston Origin CLICK HERE

Neumann U87AiAston Origin grill

N.B.

The Neumann U87Ai is 8 x the price of the Aston Origin!

Here are my Aston Origins used to record Vocals, Guitars and Harmonica on the title track of Steve Ashley’s new album ‘Another Day’.