soundfield mic for stereo application

[fafalio]

considering ambisonics for stereo application vs classica stereo application with two mics...
there are some disadvantages:
i can make only coincident stereo recording
there are some advantages:
i can choose in post angle, polar pattern, and so on.

but th question is another...i m studying how soundfield works..
but in stereo does it capture sound in a different way against a classical concident stereo tecniques? which are the differences sonically speaking or are the same (i repeat, considering only stereo)?

thanks alessandro.

[Gutbucket]

On a conceptual basis, it may help to think of an ambisonic microphone as essentially an extension of mid/side microphone technique, but with considerably more flexibility. In contrast to typical M/S mic technique, an ambisonic mic extends the region of useful decoded mic angles from a relatively small region of usable horizontal angles to the full 3-d sphere. It also un-links the relationship between the decoded pickup pattern and the decoded mic angle, allowing the user to vary one without changing the other.

The primary limitations are the restriction to coincident stereo techniques which you note, and determining if the sonic/timbrel qualities of the particular ambisonic microphone you are considering suit your needs and taste. If the flavor suits you, the biggest constraint is the restriction to coincident patterns.

In the practical world, how perfect the virtual microphone patterns are depends on the construction of the microphone and its decoding algorithm. The consistency of the pattern begins breaks down above a certain high frequency due to the impossibility of having the capsules truly coincident, but the same happens for M/S arrays. However, the decoded patterns can be more accurate across the mid and lowest frequencies than the stereo patterns using two coincident mics (M/S or stereo).

As a single microphone without a preferred direction, its certainly easy to set-up once you determine the correct location, and quite enlightening to play around with the decoding options after you get back to the studio. However, just like traditional stereo microphone techniques, there is usually only a small range of patterns and angles that are actually appropriate for any given recording. It does make finding that particular combination easier.. as long as it's a coincident one.

[Baithak]

Gutbucket : thanks for your answer. I have been struggling with whether to get into the Soundfield mic or not - especially with the high entry cost - and went to AES this year to buy the 350 portable solution, only to find out that they are coming out with a newer version early next year.

Now I am hoping that I can snag a second hand one to try before buying new :-)

Baithak

[Plush]

May I add that the better the acoustic the better the result with Soundfield. I guess that's just like what happens with any other mic.
Soundfield's strong suit is Blumlein mic technique using crossed figure of eight mics.

The Soundfield is at its best in a stone room with good reverberation. One would suspect this result already with a crossed figure-of-eight microphone.

The Soundfield has excellent bass and it is equalized to be flat. In this respect it is different than using two figure eight mics where the bass rolls off substantially. The final polar patterns of the Soundfield are more exact in every way than the equivelent separate mics since the pattern is "derived" from the multiple capsules in the mic head. The Soundfield mic presents the best "in phase" coincident available.

Soundfield is not a universal microphone. However, it is an outstanding mic and when an ensemble is suitable to be picked up by a coincident set-up, the Soundfield is the best available solution.

[fafalio]

about the possibility to choose omni...i don't find the motivation in a coincident approach..
what is the reason?
thanks Alessandro.

[jnorman]

allesandro - you might also consider the core sound tetramic, as a more affordable way to try out this kind of system.

[Plush]

Originally Posted by fafalio

about the possibility to choose omni...i don't find the motivation in a coincident approach..
what is the reason?
thanks Alessandro.

Since the Soundfield mic can also be used as a mono mic, that is where one might choose to use it in omni pattern.


Sent from my iPhone using Gearslutz

[fafalio]

thanks to all,
considering williams table and considering ambisonics can make only coincident, i suppose they work well in particular configuration as cardioid/super, while in omni, as plush say, as mono mic, in opencardioid i think it is not usable. i think they can be very good in figure of eight.
but to try all in post production i think it would be very interesting
some one know how soundfield sps200 sounds in the low frequecies? are low frequencies thin or full?

about tetramic...some people say they are noise and unbalanced connection. So perhaps soundfiled is a solution more expensive but i think more usable.

Alessandro.

[aracu]

"The Soundfield has excellent bass and it is equalized to be flat. In this respect it is different than using two figure eight mics where the bass rolls off substantially."

This is considered by some to be a weakness of the system, that a
compensating eq is a built in part of it.

[jnorman]

allesandro - here is a link to a review of the tetramic by paul hodges for ambisonic.info website. in the results and conclusions section, he includes a discussion of self noise of the system, and also includes some sample recordings. it might be worth a read...

Ambisonic Info | Core Sound TetraMic

[Tom McC]

Originally Posted by aracu

"The Soundfield has excellent bass and it is equalized to be flat. In this respect it is different than using two figure eight mics where the bass rolls off substantially."

This is considered by some to be a weakness of the system, that a
compensating eq is a built in part of it.

The individual capsules of the original Soundfield mic have been reported* to be of the subcardioid characteristic, with polar response "V = 0.667 + 0.334.cosX".

The starting bass response should thus be expected to fairly respectable, and require only relatively modest amounts of subsequent equalization to attain omni flat?

* Kenneth Farrar, 1977, Soundfield Microphone, AMS Calrec technical paper.

[Gutbucket]

The bass response is quite flat on these types of mics. I run a Tetramic and the bass is deep, nearly like that of a pressure omni, far less roll-off than a fig-8 or cardioid, but since the mic uses cardioid capsules instead of a true pressure omni capsule to derive the omni component, that bottom octave flat response makes the mic more suseptable to wind, rumble and handling noise.

My main issue with it is the restriction to coincident patterns. I often run omni outriggers with it so I can at least compare or possibly also use some of that A-B time based information. Within the decoding software, perhaps not suprisingly I most often end up with an X/Y stereo pair that is somewhere between fig-8 and cardioid, with a mic angle around 100-120 degrees. Besides the pattern and mic angle, the decoding controlsI find most useful are the ability to tweak rotation and elevation of the virtual pair and the focus control, which used in moderation can help emphasise forward prescence and the direct sound.

[leddy]

Originally Posted by Gutbucket

The bass response is quite flat on these types of mics. I run a Tetramic and the bass is deep, nearly like that of a pressure omni, far less roll-off than a fig-8 or cardioid, but since the mic uses cardioid capsules instead of a true pressure omni capsule to derive the omni component, that bottom octave flat response makes the mic more suseptable to wind, rumble and handling noise.

My main issue with it is the restriction to coincident patterns. I often run omni outriggers with it so I can at least compare or possibly also use some of that A-B time based information. Within the decoding software, perhaps not suprisingly I most often end up with an X/Y stereo pair that is somewhere between fig-8 and cardioid, with a mic angle around 100-120 degrees. Besides the pattern and mic angle, the decoding controlsI find most useful are the ability to tweak rotation and elevation of the virtual pair and the focus control, which used in moderation can help emphasise forward prescence and the direct sound.

I also have a Tetramic, and this info is spot on. I usually end up adjusting the pattern to something around hypercardioids around 100 degrees.

I do find the flat, extended bass to be more of a hurt than a help. Rumble, wind, etc., and the need for EQ to roll it off...

[Fragula]

Missed this thread as I've just remembered my password (after about 18 months!)

I don't see the "can make only coincident stereo recording" thing as a disadvantage, More "the whole point" really. (and it can make all sorts of other recordings, but accepted that for most end-user playback it ends up as stereo.

I don't find the bottom lacking, or the top.. I roll them off when decoding, and compress to varying degrees, as at the end of the line its usually gonna go through a home system that doesn't sound great.

Example. (On my Calrec (Not AMS-Calrec) Mk.IIIa, which I'm told is one of only 3 pre-production mics to leave the factory - has a higher noise floor than the AMS-Calrec Mk.IVs, and certainly the MK.V which is currently produced) Is just a bloke playing nylon guitar and singing in a room. Warts and all, no dubs.

06 House (Of Hopes And Dreams) 20100910 T2 S2496 FLAC by Ambisonix on SoundCloud - Create, record and share your sounds for free

[Plush]

Hello Fragula,

LUVED the recording, the space and the voice. Strong MOve!

[JEGG]

Originally Posted by fafalio

about the possibility to choose omni...i don't find the motivation in a coincident approach..
what is the reason?
thanks Alessandro.

MS with an omni mid is extraordinarily useful in some situations. (And from a purely conceptual basis, you are using the two "pure" mic designs.)

I used MS arrays exclusively for quite a few years, and really got a feel for the pattern of the center mic.

If you add the cost of a good omni (or 2), a hypercardioid, a figure 8, and a cardioid, you've got quite a chunk of the SF system paid for, plus you'd have the added flexibility and precision that such a system offers.

Some SF users also employ additional mic's on occasion, often omni flanks, and less often, spots.

Think of it as a very sophisticated MS system.

[davidvaldes]

Fragula, your recording sounds excellent! I like the song, the singing, the guitar playing, the recording... everything!

Would you be so kind and post a photo (if you have one) of the mic position with respect to the singer/player?

Regards.

[JEGG]

Originally Posted by davidvaldes

Fragula, your recording sounds excellent! I like the song, the singing, the guitar playing, the recording... everything!

Would you be so kind and post a photo (if you have one) of the mic position with respect to the singer/player?

Regards.

And, Fragula, if you don't have a photo please describe how things were positioned, and absolutely everything else that we'd like to hear about.

A very impressive recording, but then everybody knows that after listening.....

I would never have thought about making the recording Frgula did with the SF system-I wouldn't associate the technique with the genre.

I was sooo totally wrong about that. Thanks for that, Fragula.

[Baithak]

Dear Fragula :

Thank you for sharing. This is pretty much the evidence I was looking for before taking the plunge on the new ST450 that Soundfield plans to release sometime in March.

Baithak

[JEGG]

Originally Posted by leddy

I also have a Tetramic, and this info is spot on. I usually end up adjusting the pattern to something around hypercardioids around 100 degrees.

Of the many anecdotal comments I see, whether the Tetramic or an SF, it seems that many end up using them as a virtual Blumlein pair, or a crossed pair of hypercardioids for the various circumstances they encounter. (Though that does cover a wide variety of coincident mic'ing possibilities.)

I'm not sure that there's any significance to that, I just find it interesting. I would be interested in more reports from users. And those SF/Tetramic users with experience in MS and have 2 figure 8's, an 8 and a hypercardioid, and an 8 and a cardioid-what are the real world contrasts in terms of stereo image and pragmatic issues, such as set up and post mixing/processing, etc.?

And thanks to Gutbucket for his report on these issues.

Like leddy it seems you also are using something similar to hypercardioids-between figure 8 and cardioid.

For both Gutbucket and leddy, virtual angles of 100-120 degrees would be considered quite wide for "real" 8's and hypercardioids-but it seems to work for you and many others. Any comment on that would be welcome.

Are either of you using spots or flanks as well?

[Plush]

As a Soundfield freak I notice a better crossed figure of eight (Blumlein) with the SPS 422B than a self arranged non Soundfield set-up.
Also bass is substantially better with the Soundfield mic than standard figure eight mics.


Also the other reason to use Soundfield is to be able to simultaneously record a 4 channel B format version. Then one can steer and post-produce the stereo picture with software after the recording.

[Fragula]

Thank you all for the kind words. Some of which I've passed on to the Cameron.

I'm afraid I don't have any photos.. The CM4050 has a fairly high noise floor, and the performer quite quiet but -very- dynamic, so the mic is relatively close. I've used it at 30-odd feet for loud bands. (Monkjack springs to mind - I don't know if they have the promo online at the moment)

With Cameron it was perhaps 4 or 5 foot in front of him, with the height between the top of the guitar and the performer's chin. He sings to the right of the mic, and the sound from the guitar project to the right, but it is all done in a single take.

A little additional reverb was needed to get the right feel, though perhaps in a larger and more reflective space I wouldn't consider it desirable.

This, incidentally, was the first recording, take 1, that we did. A "test piece" to see how the setup worked. I'm quite pleased with it, and we will be recording it properly in a nice unrendered stone mill building in the wild hills of Wales when the warm weather comes. The 4050 is about 30 years old, and doesn't like the cold or damp.

Some compression was needed, and limitation of the bandwidth, in order that it sound reasonable on my "domestic reference" rig. (a $50 midi system with a pair of Auratone's) The "full fat" recording sounds fantastic (though slightly noisy) on the main monitors, but no good for normal home consumption. We will probably get the final recordings mastered Hafod, which is only a few miles away, and has a good mastering specialist in Donal Whelan. (cos I'm hopeless at mastering, and don't have a good room for it)

The idea was inspired by.. Well I listen to a lot of old stuff.. Stuff recorded with a carbon mic in the middle of a room.. and have been studying that as a way of working. Get a good sound in the room. Slam in a DC-Daylight Omni, pair of ribbons, or the Calrec, snooze while the artists play and tweak gently afterwards..

It's a "keeping it real" philosophy. Though there is no reason not to use a soundfield mic as a normal mono omni/cardoid/whatever, or as a "pair" of whatever. (two sub cardoids on that decode of "House".

I wouldn't hesitate to grab one of the new ones, and find the notion of the Tetramic interesting too, but as I'm mostly-retired now, no longer in it for the money, and so I'm cautious with my funds, the Calrec being a lucky buy on eBay when I was still working regularly.. (as I have a bunch of conventional Keith Ming built Calrecs in my locker already, and swear by certain models (but at others;-))

My other thought was, and probably still is, to use a particular nice omni, and do a trad mono recording.. Been listening to some old stuff. "Come Wander With Me".. Aweful-fi, but gorgeous anyway. Now where can I get a big ole carbon mic? ;->

[leddy]

Originally Posted by JEGG

Are either of you using spots or flanks as well?

I've used spots with the Tetramic. I have not been able to use the decoding software inside of a DAW (like Reaper, Cubase, etc.). They say it can be done. I have not put the time in to debug it. I decode in the stand-alone program then import into Cubase to mix with spots. Not ideal work-flow, but I don't work much anyway.

[richgilb]

Originally Posted by JEGG

Of the many anecdotal comments I see, whether the Tetramic or an SF, it seems that many end up using them as a virtual Blumlein pair, or a crossed pair of hypercardioids for the various circumstances they encounter. (Though that does cover a wide variety of coincident mic'ing possibilities.)

I'm not sure that there's any significance to that, I just find it interesting. I would be interested in more reports from users.

I use my Soundfield SPS200 as a yardstick for what the room sounds like and this influences what other mics I choose, if any, to supplement it. And this normally results in the Soundfield being used as a cardioid pair, the width being usefully adjustable later on.

[leddy]

Originally Posted by JEGG

Like leddy it seems you also are using something similar to hypercardioids-between figure 8 and cardioid.

I would correct that to be something between hyper and fig 8.

My approach is to shoot for Blumlein, and back off the rear lobe/change the angle as needed if the room or placement causes issues. I recorded a jazz group a few weeks ago and Blumlein happened to work great.

[teadloquor]

I've been using a Soundfield 422 since I started recording in 1997 with some very rewarding results. I've made over 50 commercial classical CDs during this time. It's a beautiful piece of kit.

I'm now sadly going to be selling my Soundfield because of a change in circumstances. I shall miss the flexibility. One thing I've always found is that it is critical to experiment with the Soundfield's position - even a few cm shift in the position can be used to bring the sound better into focus, or take a little more of the space, whichever is needed.

[JEGG]

Thanks to all the users who have shared details of their experience.

If richgilb and leddy are still reading-I'd still be interested in those large angles,>100-120 degrees, using patterns that have an out of polarity tails-something akin to hypercardioids and figure 8's. (Though richgilb's last post put this into a somewhat different context.)

Theory would make me cautious, but it would really depend on where your sources are, and no reason not to do so if it sounds good and there's no a preponderance of out of polarity material in it. (My own preference tends to go that direction, anyway.) There is a stereo technique, "Stereo 180, which is hypercardioids with an included angle of 135 dgrees with a spacing of around 2 inches. I've used that in a couple of problem scenarios and it has saved the day.

Anyway, evidently no one is experiencing difficulty with these wide angle. True? Your stereograph looks OK?

Leddy-somewhere recently I think you posted an example of a recording done in a club with a virtual or real Blumlein pair. You didn't seem to have any problems with bothersome noise from the rear-rather it simply sounded live and in a club. (This all assuming I'm recollecting correctly.)

Are you, like Plush, finding Blumlein sorts of things more pleasing in terms of pattern with the Tetramic than with MKH30's-or any other figure 8 mic?

[leddy]

Originally Posted by JEGG

Leddy-somewhere recently I think you posted an example of a recording done in a club with a virtual or real Blumlein pair. You didn't seem to have any problems with bothersome noise from the rear-rather it simply sounded live and in a club. (This all assuming I'm recollecting correctly.)

The sample was the Tetramic (with a spot mic on the bass). It was a club, but it was a listening audience for the most part. Rare these days, unless you are in a big-city jazz club. As I recall though it was not quite Blumlein. It was closer to hypers, probably around 110-120 degrees. The Tetramic was a little too close to the stage for Blumlein.

Originally Posted by JEGG

Are you, like Plush, finding Blumlein sorts of things more pleasing in terms of pattern with the Tetramic than with MKH30's-or any other figure 8 mic?

I'm certainly nowhere near Plush's league, but I do like Blumlein. A lot. I have not really had the chance to do a fair comparison between my Tetramic and my MKH30's, other than screwing around at home with some instruments. The nice thing about the Tetramic is the compact size, and no fussing with mounting two mics. The thing is practially invisible, and the imaging is spectacular.

The only thing I can say about comparing them at this point is that the Tetramic is supposedly EQ'd flat accross a really wide range. Everything I record seems to have some extreme low and high that I have to cut to sound natural. I don't know if the Soundfield is the same or not. The Sennheisers usually sound right without any EQ, and they have less noise.

[John Willett]

Originally Posted by leddy

The only thing I can say about comparing them at this point is that the Tetramic is supposedly EQ'd flat accross a really wide range. Everything I record seems to have some extreme low and high that I have to cut to sound natural. I don't know if the Soundfield is the same or not.

The Tetramic. has four unbalanced electret capsules and is unbalanced down the cables - it's balanced at the XLRs.

The Soundfield SPS200 has true condenser capsules (made by MBHO) and is balanced from the mic.

Soundfield have recently upgraded the software for the SPS200 (EG: you can now convert to B-format); so, if you have one, download the latest version.

The SPS200 is larger.

[leddy]

Originally Posted by John Willett

The Tetramic. has four unbalanced electret capsules and is unbalanced down the cables - it's balanced at the XLRs.

The Soundfield SPS200 has true condenser capsules (made by MBHO) and is balanced from the mic.

Soundfield have recently upgraded the software for the SPS200 (EG: you can now convert to B-format); so, if you have one, download the latest version.

The SPS200 is larger.

John, have you compared using the Soundfiled or Tetramic (assuming decoding to fig 8's at 90 degrees) with using a traditional Blumlein pair (like the MKH30's)?