OCT - Optmial Cardioid Triangle

OCT - Optmial Cardioid Triangle

This setup has been invented by Dr. Guenther Theile and Dr. Helmut Wittek (CEO of Schoeps).

This is not a "pure" OCT setup, but we chose it anyway to show you some extensions too.
First, let's look at the pair held together with rubber bands. The upper microphones are "omnis." More about this a little bit below.
The microphones under the omnis are hyper-cardioid, which are necessary for an OCT setup. The microphone in the middle is a cardioid microphone, and its capsule is positioned eight centimeters in front of the axis between the hypercardioids.

Now, look to the left of the system. There are additional cardioid microphones pointing toward the rear and in the opposite direction of the front cardioid microphone.
The two rear cardioid microphones are 30 cm apart.

As mentioned earlier, we will discuss the purpose of the omnis.
Omnis perform much better than hyper-cardioids do at low frequencies. This is part of their designs and not a failure. 
However, there are two major advantages here:

1. The two omnis add solid bass to the soundscape, making the sound and listener's impression more natural.
2. Another advantage is that blending the hyper-cardioids and the omnis allows you to shape the resulting pattern. To do so, check that their diaphragms are in the same position. You can fix this in post-production, but it's much easier and faster to do it before recording.

When using the Zoom F8n (Pro), we usually mount it on a camera tripod. This puts it in a comfortable position and makes it easier to check the levels.
You can also see our "4-channel multicore" system here. We actually "borrowed" it from the lighting guys. It's usually used for distributing DMX channels over a 4-channel core with RJ 49 connectors. But why not use it for sound purposes as well?
Just make sure you use a CAT 6e cable with a solid shielding.
The CAT 6e has cores with a large enough diameter so that high frequencies won't be dampened too much. 
Of course, any other CAT cable that you know of from computers will work fine. However, you may experience an audible dampening of the high frequencies.

The important thing about OCT systems is the relation between the distance of the hyper-cardioid microphones and the recording angle:

A simple rule of thumb is:
OCT: 90 cm = 90°. As the distance decreases, the recording angle increases and vice versa.

The OCT setup has evolved through several stages over time.
First, two rear cardioids were added (as already discussed). Then, some microphones were added that pointed straight up. This topic would require another article and some interesting photographs.  Stay tuned!
We'll link it here, once it has been finished.