Monthly Archives: February 2016

How to take apart an AKG D2000 or a D170

Recently I noticed a thread on a well known web forum which specialises in disseminating misinformation on a range of gear. In this erudite discourse it was suggested that these ‘inexpensive’ old AKG dynamics were not made to last and that they couldn’t be taken apart or repaired by the user. This is of course complete bollocks!

Simply peel off the name strip from around the grill ( taking care to save it to put back on afterwards.)  The top half of the grill can then be easily unscrewed. If necessary the element can be gently pulled out from it’s rubber mounting. At the other end a single screw holds the XLR in place.

The AKG D170E  pictured below has been taken apart to clean and replace the disintegrated old foam inside the grill.

AKG D170E Dismantle 1AKG D170E Dismantle 2

N.B.

It is also worth noting that when they were new these ‘inexpensive’ old microphones cost more than a week’s wages for the average musician!

AKG dynamics from the 1970’s were well designed, solidly engineered and intended to last. This one is nearly 40 years old and still sounds as good as the day it left the factory!

AKG Catalogue 1978

AKG_Mics_1978_part1

AKG_Mics_1978_Part_2

AKGD170 Bass Drum Application

Apart from being mainly designed for heavy rock vocals I was interested to note that the AKGD170 is also recommended for Bass Drum ‘ (where other microphones sound too ‘bassy’ and muddy)’……………… So with that in mind I recently took it out on some live rock’n’roll gigs and was very pleased with the tight, punchy sound it produces. If more low end is required it also responds very well to additional EQ.

CLICK HERE for AKGD170 Bass Drum Clip

Electro-Voice Rags To Riches. T45 Noise-Cancelling Microphone (1944)

In 1942 after America entered World War 2, the US military estimated that only 20% of radio communications in combat were successful. Failure in the other 80% was mainly due to the voice of the radio operator being drowned out by the surrounding cacophony of war. Like no other conflict before, success on the battlefield relied on communications. Spotting a gap in the market Al Khan and Ed Burrows, the owners of Electro-Voice, came up with a brilliantly simple, ingenious and cost effective solution to this problem. Electro-Voice T45 Box

Electro-Voice T45 Instructions 1944

Electro-Voice T45 Instructions P2Even in 1942 the single button carbon microphone was a piece of old fashioned tried and tested technology, having been in use in telephones since the tail end of the previous century. Although the audio quality of the T45 is little better than it’s telephonic predecessors it is extremely reliable and very robust. It also has a high output making it ideal for long distance communication. Even if the microphone gets wet you can simply dry it out (as per the instructions above) and it will carry on working! However, the really clever part of this design utilises 2 small holes of equal size on the front and back of the mic.Electro-Voice T45 Back hole.Electro-Voice T45 Front Hole

These allow the surrounding noise to enter the microphone on both sides of the diaphragm. The sound striking the back of the diaphragm is 180 degrees out of phase with the sound at the front. This causes a very impressive cancellation of the unwanted noise whilst the speaker’s voice, which is less than a 1/4 of an inch from the front opening, dominates the transmission.

In terms of manufacturing costs it would be hard to produce a cheaper microphone.  A carbon button is a very small tin of glorified coal dust (carbon granules) with a simple diaphragm attached.  A bit of wire and some lightweight plastic fittings and that is it! Pure genius !Electro-Voice T45 Noise-cancelling Microphone

After some initial military skepticism the product was thoroughly tested and a first order came through to Khan and Burrows  for 100,000 units! The T45 was soon taken up by all branches of America’s armed forces and  the success rate of combat communications rose to 90%.

Rags to Riches.

Prior to World War 2 Electro-Voice was a small struggling company, with 20 employees, manufacturing a handful of dynamic and velocity microphones per week. By the latter part of the war Electro-Voice had 500 employees working in 3 shifts  producing more than 2,000 T45 microphones a day! After WW2 it was also adopted by commercial aviation and remained in service for several decades.  The T45 was also used on the Mercury, Gemini and Skylab space missions.

Over the entire production run more than a million were produced placing the T45  among the highest selling microphones ever made.

During the war many small firms went out of business due to a shortage of manpower and materials, but for those involved in the war effort fortunes were to be made. In 1946 Electro-Voice moved into an impressive new factory at Buchanan Michigan where they continued to manufacture  innovative and exciting audio products  for the next 60 years.

 

Footnote 

Circuit for powering a carbon microphone.  Circuit for powering Carbon Microphones.