Since shotguns become omni's in the low frequencies


Is this true of the cards and hypers as well?

Is this true of the cards and hypers as well?

No. While pressure gradient microphones like cardioid and hypers do exhibit a "proximity effect" where bass is boosted at close working distances, their directivity is not frequency dependent. They develop their directivity on the pressure differences caused by sound waves arriving at both the front and back of the diaphram. Shotguns use a line-gradient principal with a pressure transducer (an omni capsule) located at the bottom of a tuned interferenece tube. Sound waves enter the tube through the front and at the various ports on the tube. Those coming from the front are in phase with the portion of the same sound wave entering through a side port. But sounds arriving from the sides and rear enter the tubes from the ports and from the front at slightly different times so there's a phase difference between the portion of the wave from the side port and the portion from the front port. As these two portions of the sound wave travel through the tube to the diaphram they interact with each other inside the tuned tube and cancel each other out. Since it is the wave interactions inside the tuned tube that does the work they are dependent on the frequency of the sound and the dimensions of tube, just like the tone of an organ pipe is dependent on its dimensions. Off-axis high and mid frequencies are affected much more than are low frequencies from the same directions because low frequency wavelengths are too long to be affected very much by the tube. As a result off-axis mids and highs are supressed while lows from all directions reach the diaphram undiminished.

...That software sounds interesting, but I'm not sure exactly what it does, or what advantages it offers. Could I use that software with the Sony ECM-MS957? ...

It is a plugin that works within most audio applications, and some video applications. Basically it takes two channels of audio, recorded as mid and side, and converts it to left and right stereo. In the process, it lets you vary the mix between mid and side, to achieve more of a "wide" stereo ambiance, or a more "narrow" ambiance.

It can also do the reverse transformation - extract mid and side information from a left/right recording. Finally, it does the equivalent of sticking two instances of the plugin in a row - encoding L/R stereo as mid/side, adjusting the mid/side balance, then re-encoding it back to L/R. So starting with a conventional L/R stereo recording you can modify the apparent spatial distribution.

It will work with any mid/side mike or any L/R stereo mike. You might need to invert the phase of one channel, but that is easy to do.

...
That software sounds interesting, but I'm not sure exactly what it does, or what advantages it offers. Could I use that software with the Sony ECM-MS957? Can anyone tell me if the specs on this mic are good or not? I really do want to find out if the Sony is worth buying and whether it can provide the type of M-S recording that can be manipulated to bring out the sounds and degree of stereo separation that I want to emphasize (this is the advantage of M-S as I understand it). Please advise!!
...


While the Sony mic uses the M/S principle to achieve its stereo output, it decodes the signals internally and so its output is conventional L/R stereo. AFAIK you don't have access to the original mid and side signals coming off the individual mic capsules. That means the post recording manipulation that's possible when recording the "raw" mid and side signals is no longer available.

It can also do the reverse transformation - extract mid and side information from a left/right recording. Finally, it does the equivalent of sticking two instances of the plugin in a row - encoding L/R stereo as mid/side, adjusting the mid/side balance, then re-encoding it back to L/R. So starting with a conventional L/R stereo recording you can modify the apparent spatial distribution.


It can take an X/Y recording and convert it to M-S,
so that you can work with it as you normally would
work with an M-S recording? I'd be curious to
hear what some others here have to say about
this. I guess we don't need M-S mic's anymore.

While the Sony mic uses the M/S principle to achieve its stereo output, it decodes the signals internally and so its output is conventional L/R stereo. AFAIK you don't have access to the original mid and side signals coming off the individual mic capsules. That means the post recording manipulation that's possible when recording the "raw" mid and side signals is no longer available.

Except if you use that program that Gian
recommended ... maybe. For some reason
I feel a bit skeptical about it but I don't
really know.

Except if you use that program that Gian
recommended ... maybe. For some reason
I feel a bit skeptical about it but I don't
really know.
Because the stereo L/R pair is derived from a mid/side signal matrix it can also go the other way.

Mid = (L+R)/2
Side = (L-R)/2

Because the stereo L/R pair is derived from a mid/side signal matrix it can also go the other way.

Mid = (L+R)/2
Side = (L-R)/2
Exactly.

If you've ever encoded an MP3 using the joint stereo mode, you've used a type of M/S encoding. See here: http://harmsy.freeuk.com/mostync/

The concern with, say the Sony mike or the AT 835ST in L/R mode, is that they don't do a straight transform between M-S and L-R: they apply multipliers to give the narrow or wide field effects. (It would be nice to know what these multipliers are...) So you'd have to do some tweaking to reconstruct the exact, original M-S inputs. However, since the MSED plugin is doing two symmetrical transforms, you can still use it to tweak "spatialization" of an incoming L-R signal, even if you don't know how that signal was constructed from the original M-S. You're basically applying differences.

...[The plugin Gian mentioned]...can take an X/Y recording and convert it to M-S,
so that you can work with it as you normally would
work with an M-S recording?...I guess we don't need M-S mic's anymore.Well, a single point M/S mic would still be a more convenient way to get M/S signals then fiddling to set up an X/Y pair and then deconsrtucting the recording. Plus,the mid and side signals you might extract from any given X/Y pair recording will be different sounding than the corresponding mid and side signals you'd get from any given M/S mic, because different mics are still different mics. However, that doesn't mean that I might not prefer the ultimate result from M/S reprocessing the recordings from my X/Y'd AT3031s over the result from an AT835ST. I don't have an AT835ST to play with, but I just tried the MS encorder plugin on one of my AT3031 pair recordings and I like it a lot. I had been contemplating getting the 835ST but now I don't know....

Well, a single point M/S mic would still be a more convenient way to get M/S signals then fiddling to set up an X/Y pair and then deconsrtucting the recording. Plus,the mid and side signals you might extract from any given X/Y pair recording will be different sounding than the corresponding mid and side signals you'd get from any given M/S mic, because different mics are still different mics. However, that doesn't mean that I might not prefer the ultimate result from M/S reprocessing the recordings from my X/Y'd AT3031s over the result from an AT835ST. I don't have an AT835ST to play with, but I just tried the MS encorder plugin on one of my AT3031 pair recordings and I like it a lot. I had been contemplating getting the 835ST but now I don't know....

The Waves S1 plugin gives you the same image manipulation tools normally associated with M/S using a conventional stereo input. It'll also decode M/S inputs to stereo but doesn't work the other way around.

Exactly.
The concern with, say the Sony mike or the AT 835ST in L/R mode, is that they don't do a straight transform between M-S and L-R: they apply multipliers to give the narrow or wide field effects. (It would be nice to know what these multipliers are...) So you'd have to do some tweaking to reconstruct the exact, original M-S inputs. However, since the MSED plugin is doing two symmetrical transforms, you can still use it to tweak "spatialization" of an incoming L-R signal, even if you don't know how that signal was constructed from the original M-S. You're basically applying differences.

Thanks Gian. You've explained things in a way that's easy for me to understand. So after reading this, I conclude that considering the high cost of M-S mics, and my need for an internal battery, I'm going to buy a AT825 stereo mic (AA battery and lightweight). If I want to try to get M-S audio, I'll use that piece of software to manipulate the recordings and obtain it. After reading the posts, the AT825 seems to have fewer noise issues than the Rode NT4, and is half the weight. The Sony would be decent perhaps, but it seems that pros doing use it. That seems to be a revealing fact on its performance.

Any opinions about my decision before I go out to buy? Thanks for the rental idea, but at $45 per day, its not worth it for me to rent and I don't know what I'm listening for yet. I'm going to make my decision based on those finely-tuned & experienced ears of the people who know

Here's a thought: get some video you like (maybe a clip from a movie) with stereo sound, drop it into your NLE and use the MSED plugin to fiddle with it. That will give you an idea of what is possible.

For example, copy the stereo tracks. Use the plugin on the original tracks in "inline" mode to drop the gain on the mid and leave only the sides. Use the plugin on the copy in "encode" mode, gain up the mid and kill the side to extract only the center channel. Mix all the tracks together. Experiment with panning the center channel back and forth. You should be able to do stuff like moving only the dialogue from left to right, while the background sound stays put. It's no substitute for actually having a bunch of different mikes, but you can have some fun, and learn some stuff.

BTW, several other of the free VST plugins at that site are nice too--a real time frequency distribution display, a mono to quasi-stereo processor, etc.

Yeah, that's the question alright.

In this case, how "line" is line, how "shotgun" is shotgun? Within what looks to be the interference tube of a short shotgun, there's the figure-8 capsule, which must be in the slotted section of the tube, plus the mid capsule... so how much interference tube is left to provide side cancellation to the mid capsule? Does the mid-mic have the (hollow sounding) characterstics of a shotgun when used indoors?

I'm looking for a single-housing M-S mic for primary use indoors. With what I can afford there are really only two I'm aware of, the AT835ST and the Shure VP88. However, I don't know anyone who has either one, nor a retailer in this area, so I'm very interested in Gian Pablo's experience of the AT.

Well there is the Neumann RSM 191 (you will be really upset after hearing it to know you can't afford it). You can get a lot of work done with the 835ST.

I have a review of both in my archive.

Regards,

Ty Ford

Ty, although you found the LF roll off patterns of the ATs interesting I gather that you liked the overall sound of the VP88 better. Is that right?

Well there is the Neumann RSM 191 (you will be really upset after hearing it to know you can't afford it). You can get a lot of work done with the 835ST.

I have a review of both in my archive.

Regards,

Ty Ford

Ty, thanks for the advice. I *have* employed a sound engineer who has the RSM 191, it is an awesome mic that I would love to use all the time, but no, I can't afford to purchase one!

I'll check out your reviews.

Ty, although you found the LF roll off patterns of the ATs interesting I gather that you liked the overall sound of the VP88 better. Is that right?

Well the problem is I didn't review them at the same time so I can't respond directly in a A/B sort of way.

I do remember that the wider settings of the VP88 resulted in noticeably more noise (presumably from the gain being turned up on the side capsule.)

Regards,

Ty