OCT-Surround

OCT-Surround

OCT Surround is an extension of the OCT microphone system. 

The OCT-Surround is an OCT microphone system with two backward-pointing cardioids. Due to their characteristics, they effectively suppress sounds from the front.
With this system, one can simply push the record button to achieve a natural-sounding 5.0 setup for any 5.x setup. 
Adding two omnis and placing them as far apart as possible will also provide nice bass reproduction and allow you to derive an LFE signal from them.

If you have an eight-channel recorder, you can use an additional channel for a "geophone" to capture very low frequencies.

On the picture below you see the OCT-Surround setup.

The two cardioids pointing to the back are what make this setup interesting. They transform a regular OCT setup into an OCT-Surround setup. The usual distance between the front OCT system and the surround microphones is 40 cm, and the distance between the two surround cardioids should be 20 cm wider than the distance between the hyper-cardioids in the front but no more than 100 cm.

As you can see, we are using two XLR-to-RJ49 DMX splitters to collect signals via two four-channel multicores. This is for convenience only. It will work with regular XLR cables too.

You should not only experiment with the distances between the microphone-pairs, but also with the distance and angle of the surround-microphones. Let your ears be the judge. There is a lot to be discovered.

If you have neither hyper- nor super-cardioid microphone on hand ...

... you are not lost. You have to change a few things and consider this.

First thing is, the cardioid in the front have to be moved a little bit more into the front. It must reside 12 cm in front, instead of the former 8 cm.

There are some more details to consider, but have a look at the article about the OCT -Optimal Cardioid Triangle and scroll to the end to find these details.