Topic: Marshalls USB stereo mic

[Javier Cinakowski]

man, this guy knows his shit.

Thanks.....

[Nick's Picks]

great reading!!!

recently, I started making my XY recordings wider, more like the 110-130deg depending on how tight  I am to the source.  the closer I get, the wider the XY becomes.

I still find 90deg to be the "go to" though, and if things sound really nice from my location then I just go for crossed 8's instead of cards.  that usually produces the sound I like over loudspeakers.

monitoring w/headphones is useless...as is mixing w/them.  but thats me.

[bobbygeeWOW]

Something would have to be occurring all the way to either side of the recording position (i.e. not the left or right of the stage if there is one, but at 9:00 or 3:00 from the microphones' "point of view" which is normally some distance back from the stage) in order to reach the left or right limit of the stereo image in your playback system.

No direct sound ever reaches most two-microphone stereo recording setups from 90 degrees to either side or even close to that. As a result, the stereo image for the direct sound, in playback, is bunched up toward the center--it tends to be pretty strongly mono.

Okay I've heard what yer talking about here and not really found an ideal way to fix it. Here's my two morning coffee assisted cents:

Assuming a 90 degree mic angle (whether coincident or not..) with the mics roughly pointing directly at PA stacks on either side of the stage: Direct music sound hits the mics right on-axis. The off-axis sound that extends beyond the 90 degree PA source consists of ambient room sounds of various types (music reverb, audience, etc). While I think this does squash the stereo image of the music towards the centre, it also creates an interesting (and pleasing!) sense of space in terms of that ambient room sound in the resulting recording.

If I move the mics forward, say onstage with acoustic instrument sources, any instruments outside that 90 degree spread lose their directional imaging; presumably due to the the pressure component and they sound like they are coming from "everywhere", with no fixed place in the stereo image. That's not pleasing to me, though it could work if was intended as some sort of specific keyboard wash effect..

So ultimately I accept the music being squashed towards the center somewhat and basically make sure that no direct sound will source from beyond the on-axis spread of my mics. The result is that the sound of the room itself fills in the outside of the stereo image, and I'm generally happy with the resultant sort of live concert effect. Might be why I like wider speaker placement in playback..

Blumlein is psycho-acoustically pretty much a different universe for my little head, though I also keep the direct music sources within the 90 degree spread.

The question that remains though is whether a wider image of the music itself can be created using stereo mic techniques! This isn't a studio close-mic'ed pan hard-right artificial recording environment!

[DSatz]

bobbygeeWOW, the real-world sound angle picked up by a pair of cardioids can very well extend beyond the main axis of either microphone--or it may not, depending on the angle and spacing between them. That's the whole point of finding out the "stereophonic recording angle" for a particular type of setup before you make a recording. You can't see what range of angles will be localizable during playback simply by looking at where your mikes are pointing; that's a total misconception, but it eludes a lot of people.

Please think about this and/or try it out by making some test recordings: The wider you angle your microphones apart, the more they will discriminate smaller angles of left-right location, and the narrower will be the total angle which they can pick up and span between the two loudspeakers in playback. That's the basic relationship which I'm trying to get people to pay attention to. As the angle between your microphones increases, the SRA decreases and vice versa.

You need to choose a setup whose SRA roughly matches the angular range of actual sound sources which you hope to include in your stereo image during playback. With a 90-degree X/Y cardioid setup, the pickup will extend about 45 degrees to either side of both of your microphones' main axes. That's considerably wider than most people seem to realize--from your message, you seemed to think that it was only half that angle! And it is much wider than most people need most of the time for music recording. That's why I look askance at 90 degrees as some kind of default for cardioids. I'd much rather see people choose, say, 120 degrees, then adjust from there as needed.

--best regards

[poorlyconditioned]

bobbygeeWOW, the real-world sound angle picked up by a pair of cardioids can very well extend beyond the main axis of either microphone--or it may not, depending on the angle and spacing between them. That's the whole point of finding out the "stereophonic recording angle" for a particular type of setup before you make a recording. You can't see what range of angles will be localizable during playback simply by looking at where your mikes are pointing; that's a total misconception, but it eludes a lot of people.

Please think about this and/or try it out by making some test recordings: The wider you angle your microphones apart, the more they will discriminate smaller angles of left-right location, and the narrower will be the total angle which they can pick up and span between the two loudspeakers in playback. That's the basic relationship which I'm trying to get people to pay attention to. As the angle between your microphones increases, the SRA decreases and vice versa.

You need to choose a setup whose SRA roughly matches the angular range of actual sound sources which you hope to include in your stereo image during playback. With a 90-degree X/Y cardioid setup, the pickup will extend about 45 degrees to either side of both of your microphones' main axes. That's considerably wider than most people seem to realize--from your message, you seemed to think that it was only half that angle! And it is much wider than most people need most of the time for music recording. That's why I look askance at 90 degrees as some kind of default for cardioids. I'd much rather see people choose, say, 120 degrees, then adjust from there as needed.

--best regards

Great post.  But I need coffee!  I've had two cups already.  Umm.  I'll get back to this after I finish the pot.  lol.
  Richard

[bobbygeeWOW]

Hmm, Dave, interesting concept..  my observations above are based on what I noticed from my own recordings - using near coincident methods, which introduce time delays to assist with the stereo image and to me sound generally more musically interesting. If not more precise.. From past readings I understand that DIN (20 cm at 90 degrees) has a usable SRA of 100 degrees while interestingly ORTF (17cm at 110 degrees) has a smaller SRA of 95 degrees despite the wider mic angle. This is why ideally with DIN I generally aim towards the outside sound sources (leaving a coupla degree buffer) and with ORTF I aim a coupla degrees to the outside of the outermost sound sources (hopefully enough).

Though to be truthful real life considerations force me to adapt to circumstance; seating location, gear portability, venue shape and size, convenience, crowd enthusiasm, etc often affect placement and config more than anything....

I thought XY relied on off-axis attenuation to create level differences in the sound; which leads to creation of the stereo image ala "-16 db on the right sounds like 30 degrees to the right" sort of stuff, much like a pan knob. Widening the mic angle would increase the off-axis attenuation to a given direction I guess, thus exagerating the level differences and hence, the imaging... 

...which means that the effect of rearward rejection comes into play at some point, thus reducing the usable recording angle or SRA as you call it....

Just found courtesy of DPA:


I marked XY, ORTF, DIN for reference. This certainly does show that cardioid mics with 0 cm spacing and 90 degree mic angle will give a 180 degree total recording angle, and as the mic angle increases (or the mic spacing increases!), the recording angle decreases. Hence your assertion (or Prof. Michael Williams?) that increased mic angle exagerates stereo image placement becomes completely clear in this light, as each sound source's placement has a bigger relative chunk of the overall image. Cool.

I suppose there is a way to quantify this effect.. also, what is the relationship between SRA and speaker angle? You stated above that moving speakers to 180 degrees to listen to 90 degree XY recordings would optimize the stereo effect. Does this apply for other mic techniques?

Thanks for sparking the speculation, much appreciated!

*Edit for retarded grammar.

[poorlyconditioned]

OK, three cups of coffee now and increasing.

Can any of you point to a document (eg., where that DPA figure came from) that describes this?

In the DPA figure, what are the labels on each line?  Is that angle outside the microphone position?

Suppose I want to record an auditory scene +-45 degrees in front of me.  That is, I want to get something in front, but reject the stuff (eg., crowd) at the sides.  How should I aim the mics?  One school of thought says to angle them either DIN or ORTF.  They will pick up from the sides, so maybe you want to have a narrower mic angle, like 60 degrees between the mics.  In this case, they will pick up less from the sides, but there will be overemphasis of the center.  You will reject the sides, but the signal will be more "mono".

The only way I can see to fix this problem is to get more directional mics, like hypers or even shotguns.  Then you will be able to get both a balanced contribution accross the front, and reject the sides.

Are you saying we should put a wider angle, like 120 degrees, between the mics?  I don't get that part.

  Richard

[rowjimmy]

Interesting discussion. I'll have to reread it in the morning. It's too late in the day for me to follow it all. I did have this to add:

The main thing is how this mic sounds, and how high sound pressure levels it will tolerate .
  Richard

"The MXL.007 USB also has a maximum SPL (Sound Pressure Level) rating of 137 dB"

[DSatz]

bobbygeeWOW, everything that you said in your first two paragraphs is consonant with what I'm trying to say here, including the part about adapting to real-world circumstances. (I feel that no apology is ever necessary for doing that, by the way; it's a positive accomplishment when it works.)

To me, the graph which you copied from DPA's Web site looks very much as if it was derived from Michael Williams' work, and his book "Microphone Arrays for Stereo and Multichannel Sound Recording" is my primary point of reference, so we're definitely talking the same language. Another good source is the Web site http://www.hauptmikrofon.de/ (which is in English despite its German domain).

poorlyconditioned, if what you're asking about is the single-digit numbers in the circles along the curved lines in the DPA graph--those are indicators of another aspect of a mike setup which can influence one's choice of angle, directional pattern and possibly spacing: the maximum value of "angular distortion" which will occur for that particular setup.

"Angular distortion" is the discrepancy, in degrees, between where a sound was actually coming from when the recording was made versus where it will seem to be coming from when the recording is played back over loudspeakers in a hypothetical "typical" listening configuration (normally an equilateral triangle with the speakers and the listener in its corners).

"Maximum" angular distortion simply means "the worst-case value." All other things being equal (as they say), it's nice when this number is lower rather than higher. I'm being vague on purpose because some listeners are far more sensitive to this than others, and vary greatly in the esthetic value (if any) which they place on it.

I know some musicians--string players and singers especially--who listen almost exclusively for tone (timbre); as long as there's any sense of spatiality in the recording at all, they're satisfied with the stereo aspect, and they truly don't care whether particular sound sources can be localized or not. To some people localization is a meaningless parlor trick and to others it's a bedrock virtue. Go figure.

By the way, I hope it's clear that any one graph like the one in bobbygeeWOW's message above can be valid only for one directional pattern--in this case, cardioid. The same angles and distances between a pair of wide cardioid or supercardioid or figure-8 microphones would produce very different sets of relationships and very different graphs as a result. If you want the lowest angular distortion, consider Blumlein stereo recording but be sure to watch out for that setup's narrow SRA of only ±45°!

--best regards

[poorlyconditioned]

bobbygeeWOW, everything that you said in your first two paragraphs is consonant with what I'm trying to say here, including the part about adapting to real-world circumstances. (I feel that no apology is ever necessary for doing that, by the way; it's a positive accomplishment when it works.)

To me, the graph which you copied from DPA's Web site looks very much as if it was derived from Michael Williams' work, and his book "Microphone Arrays for Stereo and Multichannel Sound Recording" is my primary point of reference, so we're definitely talking the same language. Another good source is the Web site http://www.hauptmikrofon.de/ (which is in English despite its German domain).

poorlyconditioned, if what you're asking about is the single-digit numbers in the circles along the curved lines in the DPA graph--those are indicators of another aspect of a mike setup which can influence one's choice of angle, directional pattern and possibly spacing: the maximum value of "angular distortion" which will occur for that particular setup.

"Angular distortion" is the discrepancy, in degrees, between where a sound was actually coming from when the recording was made versus where it will seem to be coming from when the recording is played back over loudspeakers in a hypothetical "typical" listening configuration (normally an equilateral triangle with the speakers and the listener in its corners).

"Maximum" angular distortion simply means "the worst-case value." All other things being equal (as they say), it's nice when this number is lower rather than higher. I'm being vague on purpose because some listeners are far more sensitive to this than others, and vary greatly in the esthetic value (if any) which they place on it.

I know some musicians--string players and singers especially--who listen almost exclusively for tone (timbre); as long as there's any sense of spatiality in the recording at all, they're satisfied with the stereo aspect, and they truly don't care whether particular sound sources can be localized or not. To some people localization is a meaningless parlor trick and to others it's a bedrock virtue. Go figure.

By the way, I hope it's clear that any one graph like the one in bobbygeeWOW's message above can be valid only for one directional pattern--in this case, cardioid. The same angles and distances between a pair of wide cardioid or supercardioid or figure-8 microphones would produce very different sets of relationships and very different graphs as a result. If you want the lowest angular distortion, consider Blumlein stereo recording but be sure to watch out for that setup's narrow SRA of only ±45°!

--best regards

I just went to that website.  There was a broken! link to an AES 2002 file.  Do you have a working link (or can you Email me the PDF).  I'd actually like to read the full paper on this topic.  I can't make much sense of the webpages.

Modified to add: OK I just found some documents here:  http://www.hauptmikrofon.de/wfs.htm

  Richard

[bobbygeeWOW]

Hey Richard, here ya go:

http://www.dpamicrophones.com/Images/DM03547.pdf

With respect to rejecting more side and rear sound sources, you might also want to check out some interesting experiments Moke was doing with parallel cardioids and a Jeklin disk baffle in hopes of increasing perceived stereophonic information. Not sure where that thread is, but he had samples up.

Of course I know absolutely nothing.    But I think the key bit I picked up here thanks to David is that counterintuitively, the recording angle decreases as you increase yer cardioid XY angle past 90 degrees. So if that's the case, stage lip you would want 90 degree XY angle to get the full +-90 degree recording angle, and as you move back you increase the XY angle to reduce the recording angle in accordance with your position... up until you get hole-in-the-middle problems. It works similarly with near coincident configs like DIN and friends but with different relationships since mic spacing introduces timing into the stereo imaging. Makes me realize I need a NOS bar.

-Cheers!

[ArchivalAudio]

hey
this is a great thread
and great points
but has anyone tried out the MXL USB.007 ?

it seems like it could be a fairly cool mic and an inexpensive way for newbie laptoip taper top get started...


I usually run 110° ORTF
I like the wider image that I can get from it as opposed to 90° XY
but I would say that XY at a wider angle opens the image up...especially spaced

any how thanx for all the input and discussion
and cool images too!

but I digress

anyone test the MXL?

Nick?



some one should take it for a test drive...

peace
-- Ian