Marinos Koutsomichalis wrote
@ John
> The maths
> W =3D Front + Back cardioid
> X and Y, will depend on how you orientate the mic. But will be:--
> Front - Back cardioid
> The Fig8 mic
"this is exactly my point - I do not think you will get the same results as=
you would with 4 cardiods even if you do the right math - it may be right i=
n
theory, but the theory makes some assumptions"
Sorry if you got the impression I was saying a Schoeps Double MS rig was
going to sound the same as a Soundfield Mic.
Very far from it, which was in a way my reason to say (well I thought I'd
said) . If you like the qualities of a Double MS rig but want a B-format
signal, because of it's post production potential, then it is quite easy to=
convert DSM to B-format.
"take for example the XY vs MS paradigm, in theory you can just convert
between the two,"
Well you can, so long as one is talking for example of taking a digital
recording in XY form & Sum & differencing the 2 tracks into MS. It will be=
perfect. You could convert back to XY & the result will be indential, it
would pass a "null" test.
You could if you wish convert back & forth many times.
"However in actual practice if you record in the first place with a MS mic=
and you compare it with a XY pair converted to MS, you will not get the sam=
e
results. "
Absolutely, no doubt about that at all, IMO.
MS, Double MS, Blumline pair & sound-field type mic arrays are all
"Coincident" mic techniques. The ideal is all mics are in the same physical=
place.
This is impossible, so at higher frequencies the minimum spacing possible
starts to introduce significant errors.
How audibly significant these errors are will be influenced by the mic
technique you used, the source material & your priorities & tastes.
A technique like XY depends quite heavily on the idea the off axis response=
of the mic, tends to perfection.
Eg a "perfect" cardioid would be 6db down in level at 90deg off axis, and
infinity dB down at 180deg. All frequencies will attenuate by the same
amount.
Again such a mic does not exist, even mics that have well regarded off axis=
response, still sound way better on axis.
What this means to me, from a practical point of view, is where I want a
stereo recording with maximum sound quality & image stability for sounds
coming from the median plain (centre), MS makes a lot of sense.
If say I'm recording orchestral music where the client wants the 1st & 2nd=
strings (placed L&R) to sound great but don't care so much about the perc =
&
wind inst, dead centre. Well then XY has loads to offer.
But back to the "maths" point, every mic array will have it's qualities. If=
you want to convert from 1 supposedly coincident technique to another you=
can preserve those qualities whilst converting to another format, with the=
right fomula.
JL
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