ECHO project - ESMA-3D

ECHO project - ESMA-3D

Although Michael Williams published the original concept for the Equal Segment Microphone Array 3D (ESMA-3D) in 1991, Dr. Hyunkook Lee optimized this setup in 2016 using the MARRS ICTD/ICLD-based localization model and augmented it with height channels for 3D recording.

But let's hear what Hyunkook says about it:

"The ESMA design concept requires: (i) the subtended angle between microphones in each stereophonic segment to match the base angle between the corresponding loudspeakers in reproduction, and (ii) the stereophonic recording angle (SRA) to match the base angle. For example, in an octagonal layout, the microphone subtended angle, loudspeaker base angle, and SRA are all 45°, while in a quadraphonic layout, they are 90°. However, the octagonal ESMA still provides good imaging across L, C, and R in a Dolby Atmos 7.1.4 loudspeaker layout. The 55 cm microphone spacing ensures sufficient decorrelation for spatial impression."

[source]

Unfortunately, this setup cannot be "budget-rebuilt" with commonly available materials. Especially there are no budget versions of a sub cardioid available; as far as we know.  We are sorry! The issues lie with the levers of the long arms on which the rapid adapters, microphone clamps, and microphones reside.

Ultimately, it all comes down to a metal disc with eight 3/8-inch holes drilled at 45-degree angles to one another.
This isn't really a problem for a good metalworking shop, but in areas where 3/8-inch (BS) isn't the standard, it can be quite a challenge. Please note the flat, milled circular areas around each whole, this gives the rods a larger contact surface and allows them to bear more weight. 
Please note, the shown metal disk is still a prototype, but it shall give you an idea. We recommend to have an additional whole on the top-side also. So you can screw in another rod and fix additional things. 

When it's all setup correctly it looks like this. At least, if you use the same gear as we did. Otherwise your mileage may vary.

If you are interested in setting up your own ESMA-3D microphone array, please find the tutorial and the shopping list. As always, they are sold as seen, with no guarantees or warranties. You will use them on your own risk. 

If you're recording with two recorders, angle them slightly upward. To do this, you may find the article about "Versatile foam from packaging" interesting.

And there are some audio samples available. 

• ECHO_ESMA-3D_AmbisonicStudio.mp3   (~ 25 MB)
• ECHO_ESMA-3D_AmbisonicStudio_7.1.4.zip   (as *.zip ~ 890 MB)
• ECHO_ESMA-3D_AmbisonicStudio_binaural.wav  (~183 MB)

Please be careful because there is a very loud noise coming at about 7:00. :-)

In case you would like to have the original sound files, feel free to ask for access to a download page via our contact page