Just a short comment during a trip:
It is IMO not true that the Octomic is “the only second-order mic
being offered commercially”.
You have to add (at least) the Eigenmike and the ZM-1 microphones:
https://en.m.wikipedia.org/wiki/List_of_Ambisonic_hardware
Both microphones might have their own shortcomings - but will be a
very good choice for at least some people.
Said this I have recommended to test the Octomic elsewhere....
Best regards
Stefan
P.S.: It is next to known that VR people would crave for a
good-sounding 3rd order (main) mike.
Could this be a commercial opportunity?
- - - - - - - -
Citando Len Moskowitz <[email protected]>:
When selecting an ambisonic microphone, I'll suggest a few things
you should look and listen for.
All of the older Soundfield microphones (all other than the SPS200)
used hardware to apply their calibrations. Each microphone was
individually measured and a calibration correction was built into
the hardware processor.
As the microphones aged, they fell out of calibration. To restore
their performance, you had to send the microphone and the processor
back to Soundfield for re-calibration. This was expensive, and
ideally had to be done every two or three years. When Soundfield
went through multiple changes of owndership, the knowledge to
re-calibrate (and even to initially calibrate) was lost.
With the introduction of our TetraMic in late 2006, the hardware
was no longer needed. We calibrated each and every TetraMic
individually and provided a calibration file that was applied with
an A- to B-format encoder plugin.
Soundfield later came out with their SPS200. Instead of providing
individual calibration files for each SPS200, they initially matched
all the capsules at the factory to the same standard, and then
provided a single generic calibration correction that they expected
would work for all SPS200s. It turns out that as the capsules on the
SPS200s aged, a single generic calibration file couldn't possibly
work for all of them. And they never offered a re-calibration
service. Eventually, based on what we've measured, they lost the
ability to even match the capsules correctly initially at the
factory - eachone is very different than the next.
The result of using a single generic calibration correction file is
that they can't correct for a lot of things. One of them is
divergence at low frequencies. So what they did was to cut off the
SPS200's low frequency response at around 90 Hz. The Sennheiser
Ambeo takes the same approach, and it also has a 90 Hz low frequency
cutoff. The new Rode mic (as of yet unreleased) seems to follow the
same approach.
And of course, as the capsules age, even if they were well-matched
from the factory (which SPS200s are not now, but Ambeos seem to be),
after two or three years, they will not be.
Neither Soundfield (now owned by Rode) nor Sennheiser offers
re-calibration services.
SPS200 and Ambeo are first-order tetrahedral array microphones.
TetraMic is Core Sound's first-order microphone. It is probably the
best-selling first-order microphone in the world. Each one is
individually calibrated. Re-calibration is recommended every two to
three years. Low frequency response goes down to below 30 Hz. (We've
calibrated them on special order down to 10 Hz.) It's calibration is
tuned to sound like a DPA 4003.
First-order tetrahedral arrays are good for some things, but
they're weak at others. If properly calibrated, its pickup patterns
are better than pretty much any mono mic. But its listening sweet
spot is only about the size of a human head. Outside of that you'll
start to hear some loss of localization cues. Its localization cues
are not particularly strong, which is why the VR industry tends to
use them for ambience, but supplements them with spot mics for
stronger localization cues.
Second-order ambisonic mics have a much, much larger sweet spot,
and much, much stronger localization cues. They can synthesize
second-order pickup patterns that have much more directional
selectivity, rejecting much more sound from unwanted directions.
That let's you get at least twice as far from the sound source as a
mono mic without losing directional selectivity. (Mono mics are
limited to first-order pickup patterns; they can't do second-order
patterns.)
Our OctoMic is the only second-order mic being offered
commercially. It's priced only a little higher than an Ambeo. We
suggest that you have a look and a listen.
Len Moskowitz ([email protected])
Core Sound LLC
www.core-sound.com[1]
Home of OctoMic and TetraMic
Ligações:
---------
[1] http://www.core-sound.com
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