Harry the Head - modification to condenser mics

The AKG D99C is a binaural dummy head microphone, often known as 'Harry the Head' or just plain Harry. Like me, Harry was born in the 1970s and still looks good for his age, albeit with a slightly fuzzy finish (which presumably is to reduce reflections). Inside his head there are two rather basic dynamic microphone which point upwards towards the vents in his ears.Harry may look good but many of his kind sound disappointing and the sensitivity is low. My own D99C sounded particularly poor with a lack of low end response and a sort of crunchy mid range. 

Harry the Head, or AKG99C to his friends

And so here is an easy way to improve the sound and sensitivity - fitting two small omnidirectional condenser mics inside will make Harry much more useable. What is more, this modification is completely reversible. You can go back to the former crunchy lo-fi tones or retain the vintage value for a collector in the future. 

Audio Technica ES945. Remove the grills and mounting nuts

For the upgrade I used two Audio-Technica ES945* boundary condenser microphones, which can be found used for reasonable prices (I paid £33 each on ebay) and I made up two short and skinny XLR cables. You will also need some needle-nose pliers and a screwdriver.  Let's go!

Microphones, cable and aluminium strain relief 

Carefully peel off the base of the head, using a scalpel if needed to remove the glue. You can see two screws that secure the cable strain relief. Undo these. Remove the two circlips which hold the microphones in place. Then pull out the whole assembly of cables and two dynamic microphones.

End view of the AKG dynamic mics.

Undo the three small screws that hold the grill of the boundary mic in place and remove the grill. Also take of the big nut and rubber mounts if they are still attached. The mic is a little too narrow in diameter and I put a layer of heat string around it, but you could use some tape here. This stops the mic from rattling and moving around.

Then fit the cables and push the microphones into the holes in the head. You will notice that the mics are at 90 degrees to the ear-holes.

New mic with shrink sleeve and XLR cable attached.

The next thing to note is that the position of the microphones is critical to the sound. If you push them too deep past the ear vents then the microphone is essentially blocked and sounds tinny and horrible. But too gar below the vent it will sound hollow. I placed them by ear (sorry for the pun), listening as I moved the mics up and down, and settling for an optimum position. just below the ear vent.

Approximate position of the microphone inside Harry's head.

Once the mics are in position, thread the cables through the channels in the bottom of the head. You can replace the cable clamp if you wish, although that will require unsoldering the cables. (I used a hacksaw here to liberate the cables!). Then stick the base of the mic back on and the job is done. Now it is time to go out and record something.

Routing of the XLR wires under Harry

Personally I think that the AKG D99c, with it's cubist styling, is the best looking binaural head microphone, although the Neumann KU100 at £6800 GBP must surely be a better microphone!  

Whether binaural recordings sound better or worse than spaced pairs or every other kind of stereo recording is a discussion for another day. 

* I am sure that other models of boundary mics would work here just as well or better. I can imagine using a couple of Oktava MK012s with omni capsules, or even a pair of 451s if you want to stay with the AKG brand. Perhaps we should consider Harry to be a microphone holder, rather than just a microphone.

Here is the German language manual for Harry, along with a translation (by google, sorry).

You can read more about Harry at Vintage Microphone World.

Update 26 August - this post has been called 'Sacrilege' by Heinbach... "I call sacrilege. The grainy tone of Harry is part of its Charm."