Topic: Oktava 4-D ambient 'soundfield' mic

[RichT]

Just found this for sale on German eBay: http://oktava-shop.com/view_prod.php?id=194
http://www.ebay.de/itm/Oktava-4-D-ambient-microphone-/190604350869?pt=DE_Elektronik_Computer_Audio_Hi_Fi_Mikrofone&hash=item2c60e79595#ht_1553wt_1150

Same as 4x MK-012 and you can also change the capsules. 

The capsules don't look quite as close together as other soundfield style mics, so the imaging may not be quite as good.  But those Oktava mics are decent

[NOLAfishwater]

nice find. looks interesting

[Colin Liston]

Someone buy one!

[notlance]

It appears this mic has been available for a few years now, but there is very little information about it that I could find.

The big question is does it come with any software to "decode" the output?  Perhaps you could use some of the software written for other Ambisonics mics, but such sw would not adjust for the particular capsules and spacing used in this mic.

Really the price is not too bad, especially if this mic can be plugged directly into 4 mic pre-amps without having to buy any additional adapters or cables.

[Gutbucket]

I've seen photos of that mic for a couple years or so.

It's more like a Schoeps DMS setup than a tetrahedral ambisonic mic.  Think full horizontal plane Mid Side with independant control over mic patern and angle.  Once converted to B-format, standard ambisonic decoding would work for the horizontal plane.  The key is in converting the 4 raw mic feeds to B-format.

Oops, scratch that. I posted before looking at it.

Just checked the listing and this is not the mic I was thinking of, I'd forgoten about this adaptation.  This one is tetrahedral and would operate as a full sphere ambisonic mic including height information.  The one I was thinking of uses the same capsules but the four are arranged like a cross in the same plane, facing the four cardinal directions.   

This one would also need the raw microphone feeds (called A-format, unusable in that format) converted to either 4-channel B-format (the universal ambisonic format) or directly to virtual microphone outputs (single mic, stereo pair, or any number of coincident 1st order mic patterns) via software.  There are freeware VSTs and comand line softwares that can do that, but better implementations do sophistcated things like attempting to correct for the distance between capsules and equalizing the response for each based on response measurements.  To use this correctly requires a disposition to do a lot of research and geek tweaking to get the requied software together and even more to compensate for the capsules not being as coincident as the better known ambisonic mics.  So unless this comes with software that does that, you'd need to have access to measuring equipment and be prepared to spend a good bit time and effort turning yourself into a tetrahedral mic expert in order to get this to work well.

And as Rich observed, the capsule spacing seems large, which agravates the compensation issues.  But, if the price is right, it could be an interesting project for a mic experimenter.

[ero3030]

3 to 4 months wait time to be built

[Colin Liston]

3 to 4 months wait time to be built

And you have to pay up front.

[F.O.Bean]

Still looks interesting

[John Willett]

Just found this for sale on German eBay: http://oktava-shop.com/view_prod.php?id=194
http://www.ebay.de/itm/Oktava-4-D-ambient-microphone-/190604350869?pt=DE_Elektronik_Computer_Audio_Hi_Fi_Mikrofone&hash=item2c60e79595#ht_1553wt_1150

Same as 4x MK-012 and you can also change the capsules. 

The capsules don't look quite as close together as other soundfield style mics, so the imaging may not be quite as good.  But those Oktava mics are decent

Interesting, but looks as if they don't understand the Soundfield principle very well.

Certainly the option of having omni, cardioid or hyper-cardioid heads indicates this.

Also, the capsules appear to be mounted in flexible rubber - this means that their relationship with each other will not be constant as they are free to move slightly.

It looks as if someone has decided to copy the Soundfield SPS200 without fully understanding the principles of the soundfield microphone.

[Nick's Picks]

this thing has been around for a good 5 years.   but finding info about it is like finding a clear picture of bigfoot.

[Church-Audio]

this thing has been around for a good 5 years.   but finding info about it is like finding a clear picture of bigfoot.

Actually not that hard 

[Gutbucket]

With the capsules that far apart they should call it the Bigfoot.. or the Sasquatcher.

John is on it as a copy of of the SPS200 and the absurdity of using omni capsules for typical ambisonic music recording use.  There are systems which use arrays of omnis, but the capsules need to be farther apart to work well.  I did see one about this size using omni hydrophones for underwater ambisonic tracking FWIW, but that's not about fidelity.  I don't know why anyone would choose to use anything but the cardioids for typical ambient or music recording use, though hypers might technically work as long as the matrix compensation was designed specifically for them... it might make sense if their hypers have less pattern variation off-axis than the cardioids.

Not sure that the capsule mounts are flexible, which would be a stupid design move as John mentions.  I assumed they were metal triangles with the corners bent upwards where they screw together.

[John Willett]

The original Soundfield actually used wide-cardioid capsules.

[Nick's Picks]

yup, all the caps on the ST250 are sub-card

[Gutbucket]

I've wondered why, and never found a good answer.  Anyone know?

It seems counter productive in generating too much omni (W) component compared to fig-8 (X/Y/Z) components, which then has to be compensated in the matrixing by reducing W gain substantially.  Maybe something to do with the tight physical arrangement of capsules adversly effecting the cardiod pattern?