Please, is it possible to decompose a directional pattern of the 1st order to an omni and a fig. eight component? For example:
1st order Cardiod = 0.5 x (1st order omni + 1st order fig. eight)?
Yes, very easily.
Three of the four first-order B-format channels (X, Y and Z) are figure-8s. One of them (W) is an omni.
And with a beamformer plugin, you can create any combination of them and output any first-order microphone directivity pattern, including sub-cardioid, cardioid, super-cardioid and hyper-cardioid. As many you want, in any combination. Pointed in any directions that you want. Simultaneously.
And all of them are equal to or better than any of the world-class mono mics.
Directional patterns of 2nd order look complicated. Is there an easy way to decompose it to the components?
They are not decomposable - they are the second-order spherical harmonics, just as the first-order channels are the first-order spherical harmonics.
The second-order B-format channels are combinable with each other and with the first order channels to produce patterns like the second-order cardioid and hyper-cardioid directivity patterns you can see on our web site:
www.core-sound.com/OctoMic/2.phpAnd there are many more, including ones with very, very low side- and back-lobe levels, and very tight directivity.
I would like to ask if an ambisonic mic generally behaves as an ordinary mic - the more directional pattern, the less sensitivity for bass?
No. What you're hearing may be an artifact of the plugin. Or an interaction of the room's bass response and the directivity pattern.
OctoMic goes down to around 30 Hz @ -2 dB. That's for everything OctoMic records.
Has an ambisonic mic a proximity effect when recording close to a source and decoding to the directional patterns?
There's no proximity effect if the target directivity is a B-format channel. There will be a proximity effect if the target is a combination of the channels. In that way it's pretty much the same as mono mics.
And the last question. I'm curious about the artificial simulation of a spacing between the microphones. Len is sharing the recordings of his ambisonic mic and a pair of a regular mics in ortf. I wanted to generate ortf from Len's ambisonic mic and compare it with regular pair. Len is recommending Compass plugin. Unfortunately, I was not able to set it up correctly. Has anyone done it? (Ha ha, if this works, it would completely change our hobby. Maybe we will be pleasantly surprised one day)
Spaced arrays with first-order directivity patterns can be decoded from a single ambisonic mic - not very well with a first-order ambisonic mic, and somewhat better with the first-order components of a high-quality second-order ambisonic mic. The process uses plane wave decomposition, which - as I understand it - works only at first-order.
The Harpex plug-in provides for it, but I'm not satisfied with its results.
That said, it's easy to do all of the ORTF arrays (and other spaced arrays) with OctoMic. In fact, you get the world's best behaved (and IMO sounding) ORTF, ORTF-surround and ORTF-3D arrays. How? Use multiple OctoMics.
For the ORTF-surround and -3D arrays each of the OctoMics plays the role of between two and six mono mics. All of the pointing angles are set in post. And the OctoMics give better results than the mono mics.
See the photos below.