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Gear / Technical Help => Microphones & Setup => Topic started by: TheJez on November 26, 2025, 05:47:56 AM
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Hi everyone,
Just for fun & experimenting, I consider trying to create a side mic by putting my two Core Sound Cardioid Stealthy mics back-to-back. The mics are joined to a 3.5mm stereo mini-jack, so common ground at the sleeve, left=tip, right=ring (or vice versa, don't know for sure).
My mid mic will be an SP-CMC-4U mic with XLR connector.
Unfortunately I don't have a multitrack recorder. I do have a Tascam FR-AV2 (2x XLR/TRS in, mini-jack in) and an Edirol R09-HR (mini-jack in).
My plan is to record to Core Sounds into the Edirol, then afterwards in DAW, invert the phase of one channel and sum them to a single side channel. The mid channel would be recorded by the Tascam. Then, afterwards, sync the mid and side and do the m/s stuff to play with the stereo image.
Especially needing two recorders and having to sync afterwards isn't very convenient for my intended setup. Ideally I'd somehow want to connect the two Core Sound's to a single input of the Tascam. Would it be possible to connect left and right to pin 1 & 2 of an XLR connector to establish this? Or am I missing something then (e.g. the phase inversion)? If so, how could this be fixed? Any thoughts and suggestions would be appreciated!
I can't/don't want to spend much money on this experiment, so buying a multitrack recorder or getting a true figure-8 mic for this is not an option, but buying a female mini-jack and an XLR connector and do some soldering is not a problem, as long as I don't have to cut-up the existing wiring of the Core Sound's. I'd like to achieve the best possible results with my far from ideal set of equipment at hand.
Thanks!
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assuming you can power them via an external bb, you could make a cable that goes minijack -> xlr and combine the 2 mics into 1 channel. pin 1 = ground, pin 2 = left pin 3 = right. It still won't be a figure 8, but it might be interesting to try.
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assuming you can power them via an external bb, you could make a cable that goes minijack -> xlr and combine the 2 mics into 1 channel. pin 1 = ground, pin 2 = left pin 3 = right. It still won't be a figure 8, but it might be interesting to try.
Thanks grawk for responding/confirming.
Yes, I have bb for the core sound mics! I was thinking the same wiring but mixed up the pin numbers and was in doubt about the correct phase. Now I'm thinking of it: Let's say left mic is pointing left, mic right pointing right. If a positive wave arrives from left to right, it will generate a positive voltage on pin 2, and a -more or less- equally negative voltage on pin 3 (or vice versa). The recorder records the delta between the two and Bob's your uncle :-)
Sounds good, I will give it a try when my SP-CMC-4U arrives and I get an XLR connector...
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The side channel definitely won’t sound like a figure 8 but it may process down close enough.
Back in the day when I was first playing with midside I used an at stereo mic as a figure 8
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The side channel definitely won’t sound like a figure 8 but it may process down close enough.
Back in the day when I was first playing with midside I used an at stereo mic as a figure 8
Yeah, I know it won't be perfect... I thought it may be an interesting experiment to try once I have my new SP mics...
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I will warn you that the logical end to the midside journey is a schoeps double mid side rig ;)
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I will warn you that the logical end to the midside journey is a schoeps double mid side rig ;)
Haha, I probably can’t afford that! I don’t even dare to check it out… :)
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Why would you want to pick up more side noise? The point of having cardioid mics is to not record much of that.
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Why would you want to pick up more side noise? The point of having cardioid mics is to not record much of that.
If this is a serious question, there's a microphone technique called "Mid-Side" which is mathematically equivalent to XY, but instead of 2 mics each 45 degrees off the center axis, one of the mics is on the center axis, and the other is a figure 8 microphone that captures the "side", + on the left and - on the right. You combine the side signal with the mid to get the left channel, and the inverse of the side channel with the mid to get the right channel, which you can then control in post to vary the perceived width. There's a LOT of writing about this technique.
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Huh, seems like a lot of complication to make for a worse recording, at least for what I want in a live recording. I try to get the annoying crowd on the sides of me completely out of my recordings.
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Huh, seems like a lot of complication to make for a worse recording, at least for what I want in a live recording. I try to get the annoying crowd on the sides of me completely out of my recordings.
(I'm not an expert on this, so I may be talking nonsense, but I'll give it a try:)
Yes, so do I... However, somewhere in the past I was unfortunately forced to record some shows with a single (cardioid) mic. Although I managed to get very decent recordings without much of the annoying crowd, the recordings sounded rather dull. Although I really hate people near me discussing the latest office gossips during a show (and they really have to shout to make themselves heard), the mono-recording made me appreciate the sense of spaciousness of a two-mic recording. At a typical rock show the sound coming out of the PA's left and right is usually about the same. There, the sense of spaciousness is provided by the reverb of the venue, and yes, by the people making noise (hopefully not too much relative to the music you want to record) around you. With a classic X/Y setup, the balance between the sound coming from the front and the sound left/right of you is fixed at recording time. When doing a mid/side recording, you can change this balance in post production.
I have no immediate intention to start doing M/S recording during shows that I matter much about, but I am a bit intrigued by this recording technique and would like to experiment with it without directly spending much on the equipment. A figure-8 mic as side-mic is what would be needed to do this properly, but I don't have one laying around. However, putting two cardioid mics back-to-back construct a more or less similar signal.
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Huh, seems like a lot of complication to make for a worse recording, at least for what I want in a live recording. I try to get the annoying crowd on the sides of me completely out of my recordings.
Then you shouldn’t try it.
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Huh, seems like a lot of complication to make for a worse recording, at least for what I want in a live recording. I try to get the annoying crowd on the sides of me completely out of my recordings.
(I'm not an expert on this, so I may be talking nonsense, but I'll give it a try:)
Yes, so do I... However, somewhere in the past I was unfortunately forced to record some shows with a single (cardioid) mic. Although I managed to get very decent recordings without much of the annoying crowd, the recordings sounded rather dull. Although I really hate people near me discussing the latest office gossips during a show (and they really have to shout to make themselves heard), the mono-recording made me appreciate the sense of spaciousness of a two-mic recording. At a typical rock show the sound coming out of the PA's left and right is usually about the same. There, the sense of spaciousness is provided by the reverb of the venue, and yes, by the people making noise (hopefully not too much relative to the music you want to record) around you. With a classic X/Y setup, the balance between the sound coming from the front and the sound left/right of you is fixed at recording time. When doing a mid/side recording, you can change this balance in post production.
I have no immediate intention to start doing M/S recording during shows that I matter much about, but I am a bit intrigued by this recording technique and would like to experiment with it without directly spending much on the equipment. A figure-8 mic as side-mic is what would be needed to do this properly, but I don't have one laying around. However, putting two cardioid mics back-to-back construct a more or less similar signal.
Yeah, it might be interesting to try, but if you really are wanting to recreate the ambiance of the room, wouldn't it be easier just to use two binaural mics?
I agree that mono recordings generally sound a bit dull, and I like there to be some significant difference in the two channels.
I'm a fan of the sound of the Core Sound cardioids and have used them for years. But I don't generally point them both straight forward. I'm typically pretty close to the front of the room, not dead center, but a bit to one side or the other, roughly equidistant of between the band and the PA on that side. Then I try to point one mic at the band and the other at the PA.
That way I get a somewhat different mix in each channel, with the main difference being that more vocals are in the channel with the mic pointing at the PA. Sometimes there is a significant volume difference between the two channels, but that's really easy to balance in any music editing software.
I know my method isn't common, as I've never heard of anyone else doing this, but my recordings generally turn out great (to my ears anyway), and I've received lots of compliments on my recordings over the years.
If you're interested in hearing any of them, there are a few on archive.org, some on TTD, and lots on DIME. All made with CSC or other small cardioid mics. If you need help to find any, just send me a message.
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At a typical rock show the sound coming out of the PA's left and right is usually about the same.
Almost all of the shows I go to are mixed in stereo.
In my mind, one of the conveniences of MS is that it is an easy low-profile set-up.
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Your biggest challenge is going to be how to mount the mics so that the side mics are oriented exactly 180 degrees from each other as close as possible and that the mid mic is 90 degrees perpendicular to it.
This is one of those scenarios (unlike other stereo arrangements that are a little more forgiving of a few degrees of inconsistency) where if the mics move AT ALL it will drastically change the sound of the results.
The other challenge you face is not having enough clock synced channels. Using two recorders from different brands and decades is probably not going to work out very well but, hey, stranger things have happened.
Give it a shot. Experimentation is fun. Like many, I learn by doing.
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Your biggest challenge is going to be how to mount the mics so that the side mics are oriented exactly 180 degrees from each other as close as possible and that the mid mic is 90 degrees perpendicular to it.
This is one of those scenarios (unlike other stereo arrangements that are a little more forgiving of a few degrees of inconsistency) where if the mics move AT ALL it will drastically change the sound of the results.
The other challenge you face is not having enough clock synced channels. Using two recorders from different brands and decades is probably not going to work out very well but, hey, stranger things have happened.
Give it a shot. Experimentation is fun. Like many, I learn by doing.
Yes, that's my primary goal. "Just for fun & experimenting" was my first sentence in this thread :-). Usually I tape stealth, using a similar setup as robgronotte: Rather close to the PA (so any unwanted audience noise is relatively quiet compared to the music), one mic pointing to PA, the other more towards the band, getting a different sound on each channel to create some 'spaciousness'. Pointing out the sensitivity for mic movement is much appreciated. M/S seems indeed less suitable for body-worn setups. I will try to wire the two cardioid mics into one channel so I can record M and S on one recorder, preventing sync issues.
Thanks all for your feedback, this is much appreciated! I'm looking forward to getting my soldering iron out and do some experimenting :yahoo:
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At a typical rock show the sound coming out of the PA's left and right is usually about the same.
Almost all of the shows I go to are mixed in stereo.
In my mind, one of the conveniences of MS is that it is an easy low-profile set-up.
What kinds of bands / venues do you generally go to? I've almost never noticed any shows I attend having stereo mixed PAs, and it sounds like a terrible idea for any show where some of the audience will be far out to one side so they wouldn't be hearing all of the music.
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Mostly smaller venues where basically everyone is reasonably close. Jazz, rock, some stuff like The Wood Brothers or Charlie Parr (Americana, I suppose?). I think ~ 99% are in stereo. Many of the venues have really nice systems and arrays, as they are incorporated as foundations and receive some measure of public support. I went to a famous venue in Brussels and they had an enormous Switchcraft board. I am chatting with the FOH and he proudly tells me he could individually mic an orchestra into that monster. I asked him how often he gets orchestras in there and he admits he's never used more than 15 or so channels. I arched an eyebrow and he said they had funds to spend before the end of the fiscal year. "Hey! We're ready for anything now!"
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Mostly smaller venues where basically everyone is reasonably close. Jazz, rock, some stuff like The Wood Brothers or Charlie Parr (Americana, I suppose?). I think ~ 99% are in stereo. Many of the venues have really nice systems and arrays, as they are incorporated as foundations and receive some measure of public support. I went to a famous venue in Brussels and they had an enormous Switchcraft board. I am chatting with the FOH and he proudly tells me he could individually mic an orchestra into that monster. I asked him how often he gets orchestras in there and he admits he's never used more than 15 or so channels. I arched an eyebrow and he said they had funds to spend before the end of the fiscal year. "Hey! We're ready for anything now!"
I go to mostly small venues myself as well, but still there are always some people close to the wall on one side, and if the shows were mixed in stereo, those people would be hearing maybe 80% of one channel and it would sound bad. I'm pretty sure I would notice, because once (long ago) I was in the front right up against the PA on one side, and I immediately realized that I could hear the guitarist on my side very loud and could barely hear the other guitarist at all. It sounded awful, and I reluctantly moved somewhat back and closer to the middle.
But this was the venue I went to the most often, and I almost always was very close to one PA, and I had never noticed that happening before. It wasn't even like that for the two opening acts at that show, so I figured either it was a mistake or it was a special request by the band.
In the last few years I've gone to over 200 shows per year, and I believe only one of those times did I notice that I might not be hearing everything through the PA closer to me. And even that was not nearly as significant as the show I described above.
Maybe venues / sound engineers do things very differently in Europe than they do in the US?
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I think so. FOH guys here are startled to learn that many shows in the US aren't stereo. Like I said, a lot of these places get some extra funding, so they have nice arrays and whatnot.
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In most rooms a stereo mix doesn’t give most attendees a good experience. The music in the room will still be in stereo, it’s just from ambience and stage volume combining with the pa.
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Yeah, it might be interesting to try, but if you really are wanting to recreate the ambiance of the room, wouldn't it be easier just to use two binaural mics?
I agree that mono recordings generally sound a bit dull, and I like there to be some significant difference in the two channels.
I'm a fan of the sound of the Core Sound cardioids and have used them for years. But I don't generally point them both straight forward. I'm typically pretty close to the front of the room, not dead center, but a bit to one side or the other, roughly equidistant of between the band and the PA on that side. Then I try to point one mic at the band and the other at the PA.
That way I get a somewhat different mix in each channel, with the main difference being that more vocals are in the channel with the mic pointing at the PA. Sometimes there is a significant volume difference between the two channels, but that's really easy to balance in any music editing software.
I know my method isn't common, as I've never heard of anyone else doing this, but my recordings generally turn out great (to my ears anyway), and I've received lots of compliments on my recordings over the years.
If you're interested in hearing any of them, there are a few on archive.org, some on TTD, and lots on DIME. All made with CSC or other small cardioid mics. If you need help to find any, just send me a message.
I tried it once in 1997 when the tapers section in the back of the room was both full and filled with unfriendly/unhelpful tapers. Hilariously (to me) not one of those other audience tapes has been posted on archive, although Dr Mike Frasca posted his patch of the board feed in 2017.
https://archive.org/details/moe1997-03-15-flac16 (https://archive.org/details/moe1997-03-15-flac16)
My recording could probably benefit from a remix, using my impending improved "reversible mix" technique where i plan to roll phase 90 degrees on the "side" channel to avoid bass buildup on one side and cancellation on the other (depending on the level of correlation)
See the current thread here with notes to other discussions https://taperssection.com/index.php?topic=208572
A few of the signals coming from a typical stage are in stereo, such as guitar with Ping-Pong delay, keyboards, and overhead mics. Even drums can be pan-potted into a stereo mix - it doesn't have to be the full width of the pan-pot either, it can be spread across the relative center zone of the panner.
If the bulk of the mix is in mono, but a few things are in stereo, it can give a good effect without depriving off-center audience members of the ability to hear parts of the music.
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Huh, seems like a lot of complication to make for a worse recording, at least for what I want in a live recording. I try to get the annoying crowd on the sides of me completely out of my recordings.
You've got a lot to learn.
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The hardware modifications are complicated, so why not just record x/y @ 90* with the cards you have, decode from stereo to raw mid-side, then back to stereo with the desired m/s ratio. I believe there are dsp plug-ins that will allow you to process stereo> m/s> stereo in one step.
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The hardware modifications are complicated, so why not just record x/y @ 90* with the cards you have, decode from stereo to raw mid-side, then back to stereo with the desired m/s ratio. I believe there are dsp plug-ins that will allow you to process stereo> m/s> stereo in one step.
Unless the mics have very even off-axis response, X/Y and M/S are not likely to be directly convertible.
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Huh, seems like a lot of complication to make for a worse recording, at least for what I want in a live recording. I try to get the annoying crowd on the sides of me completely out of my recordings.
You've got a lot to learn.
It's been working for me for 30 years, no need to learn something far more difficult and complicated when I get better results than almost anyone who uses much more expensive equipment.
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The hardware modifications are complicated, so why not just record x/y @ 90* with the cards you have, decode from stereo to raw mid-side, then back to stereo with the desired m/s ratio. I believe there are dsp plug-ins that will allow you to process stereo> m/s> stereo in one step.
Unless the mics have very even off-axis response, X/Y and M/S are not likely to be directly convertible.
This.
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It's been working for me for 30 years, no need to learn something far more difficult and complicated when I get better results than almost anyone who uses much more expensive equipment.
With that kind of talent what are you doing wasting your time on here? Surely your skills must be in high demand.
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With that kind of talent what are you doing wasting your time on here? Surely your skills must be in high demand.
or at least your ego
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It's been working for me for 30 years, no need to learn something far more difficult and complicated when I get better results than almost anyone who uses much more expensive equipment.
With that kind of talent what are you doing wasting your time on here? Surely your skills must be in high demand.
Obviously I'm here to help the OP, who seems like a good guy, unlike some people around here.
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It's been working for me for 30 years, no need to learn something far more difficult and complicated when I get better results than almost anyone who uses much more expensive equipment.
With that kind of talent what are you doing wasting your time on here? Surely your skills must be in high demand.
Obviously I'm here to help the OP, who seems like a good guy, unlike some people around here.
your judgement is impeccable.
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It's been working for me for 30 years, no need to learn something far more difficult and complicated when I get better results than almost anyone who uses much more expensive equipment.
With that kind of talent what are you doing wasting your time on here? Surely your skills must be in high demand.
Obviously I'm here to help the OP, who seems like a good guy, unlike some people around here.
your judgement is impeccable.
Do you think a guy who entered the conversation just to make insults is likely a good one?
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By telling him it’s bad to experiment?
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TheJez, it is a very nice experiment. For example, Octava does a similar thing. From the link you can see that it is not entirely critical to have a certain distance between the capsules.
https://www.oktava-shop.com/MK-012-100-Series-modular-system/Capsules/MK-012-figure-of-eight-adaptor.html?language=en
With the opposite connection of two cards to one output, I can think of only one small thing. I am not sure, it's possible that the impedance in the output of mics will increase. Also, double the current from the BB will probably be needed. But I hope there will be no obstacles in this. Maybe someone who understands electricity might explain us.
What I read here on the forum and I hope I remember it well. The advantage of M/S is that the good fig 8 has an accurate unchanging polar pattern for most frequencies. We can get a more accurate stereo image compared to not top mics in XY. It's also a good combo for a shotgun. The shotguns are not suitable for good stereo image, but it can make a good mid signal for a main sound source. And the side signal can record the precise fig 8.
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TheJez, it is a very nice experiment. For example, Octava does a similar thing. From the link you can see that it is not entirely critical to have a certain distance between the capsules.
https://www.oktava-shop.com/MK-012-100-Series-modular-system/Capsules/MK-012-figure-of-eight-adaptor.html?language=en
With the opposite connection of two cards to one output, I can think of only one small thing. I am not sure, it's possible that the impedance in the output of mics will increase. Also, double the current from the BB will probably be needed. But I hope there will be no obstacles in this. Maybe someone who understands electricity might explain us.
What I read here on the forum and I hope I remember it well. The advantage of M/S is that the good fig 8 has an accurate unchanging polar pattern for most frequencies. We can get a more accurate stereo image compared to not top mics in XY. It's also a good combo for a shotgun. The shotguns are not suitable for good stereo image, but it can make a good mid signal for a main sound source. And the side signal can record the precise fig 8.
Another good thing about mid-side (though not necessarily exclusive to mid-side, to be clear) is that the mid mic will be directly on axis with the sound source and most mics have their best frequency response for the on-axis sounds.
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Thanks all for your support on this experiment. I've learned a lot already by just reading your replies. I've created a nice 'stand' to mount the two CSC's from a few childhood Lego parts, see attachment. Diaphraghm distance is about 4cm, just below 2". I hope that's ok for a faked side mic. These mics are very unsensitive/quite noisy, so I need to figure out a good/loud enough setup for testing. I was thinking about passing trains or something.
First need to get an XLR connector and a mini-jack female connector to wire things up...
I was surprised to see how much emotions this thread evoked. Please be respectful to each other. This experiment is just for the fun of it. :cheers:
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Rigged up like this it's a similar distance as the AKG 522 XY stereo mic that I have. I've used it as a side mic in an impromptu mid side setup with a front facing cardioid a couple of times (you can adjust the included angle between the stereo capsules by turning a screw on the housing which moves the capsules inside mechanically from 90, 120, 150, 180 degree angles). It should work fairly well even though that much separation isn't ideal from a math standpoint.
Extra points for the Lego mount.
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Just came across this thread. It can work, but..
There are a few ways to go about it, which I'll go into below. But regardless of how its done a fundamental issue will be how well the two cardioids used to produce the Side channel match each other in frequency response, level and phase. The closer that match, or the closer those aspects can be made to match before summing them to produce the Side channel, the better everything else is going to work. There are ways of getting that match close enough even if it isn't, but you will need to determine how far you want to go to achieve that.
The easiest and most flexible way of doing this will be to record the three mics to three separate channels, then produce the Side channel afterward on the computer. Not only will that not require any custom wiring or connectors, but it will allow you to improve the match between the two cardioids if required. If the two cardioid signals match perfectly (unlikely), all you'll need to do is invert polarity on the right-facing one and sum them together to produce the Side channel. If they don't, you be able to compensate for the mis-match to some extent, determine the extent of the mismatch, and determine how well this is capable of working, to determine if its worth pursuing.
^
That method of recording all three mics separately requires a multichannel recorder to produce a stereo mid/side recording. Would be a good application of the three channels of a Mixpre3. But even if you don't have a multichannel recorder available, you can use a two channel recorder to do initial testing to determine how feasible it will be in practice and if it makes sense to pursue further. In the best case you may be able to use a two channel recorder (more on how you can do that in a following post)..
First, best to do an initial check of the match of the two cardioids and their sum to fig-8, which you do using a two channel recorder. Couple ways to do that.. try both!
Method A (simpler, more clear immediate result)
1) Place the two cardioids as close together as possible, pointing the same direction. I'd actually tape them together, just don't cover the side vents. Record each microphone to a separate channel as usual - you can use a two channel recorder for this if a multichannel recorder is not available. Produce a steady tone or noise on your phone and place that directly in front of the recording rig. Record some of that noise using identical gain for each of the two channels.
2) Transfer the recording to the computer. Flip polarity on one channel (normally the right one, but doesn't matter in this case). Sum the two to mono. Place the faders for both channels at 0db gain and listen to the noise. Slowly move one of the two faders.. move it up, move it down.. Search for the point where you achieve maximum cancellation of the noise that was being produced by the phone. You wont achieve total cancellation, but you do want to fine the point where the cancellation is strongest and the noise is quietest. Once you find that, note the difference in gain between the two faders. If the mics are perfectly matched, both faders will have the same position. If they aren't you'll know know which is more sensitive than the other, and by how much. At that point if you mute either channel the noise should increase significantly, but with both unmuted, the noise should be as quiet as possible. Once that's done, you'll always apply that difference in gain between the two cardioid channels which will get summed to produce the mono Side signal. More on additional ways of improving the match in a later post..
Method B (closer to the required end result)
1) Take your 180 degree angled cardioid rig outside away from reflective surfaces so as to emulate an anechoic space as much as possible. Record each mic to a separate channel as usual - you can use a two channel recorder for this if a multichannel recorder is not available. Produce a steady tone or noise on your phone and place that directly in front of the recording rig, 90 degrees off axis from both of the cardioids, and centered between them. Record some of that noise using identical gain for each of the two channels.
2) Same as before. The cancellation you are able to achieve will be significantly less, but go through the process again and see how good you can get it. Difference in gain should be the same as in method A.
Okay, let's assume the match between the two cardioids is good and you are able to achieve good cancellation using the same level of both channels with no other adjustments. That's great. It means it may work practicality without too much post work, and means you may even be able to use a two channel recorder with balanced inputs along with some creative wiring in place of a multichannel recorder.
Regardless if you end up using this for actual recording and the particulars of how you end up go about doing it, the ability to achieve a decent fig-8 null is going to be a key indicator of probable success and can be loosely confirmed via these tests. You can do them without any additional equipment, and if they work out, things are promising moving ahead..
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Backing up to try and clarify a few comments about stereo - through the PA, in the room, via mic configs and our recordings.
The sound of any live performance, as heard in the space in which it was performed, is always multi-dimensional. Even if reinforced from a single speaker PA, even if there is no PA and only a single singer standing alone on stage, the sound as heard in the performance space is multi-dimensional. We can choose to capture that multi-dimensional complexity with varying degrees of dimensional "freedom" by way of additional recording channels.
2-channels can be used to very usefully capture and reproduce part of that multidimensionality. "Stereo" is a somewhat loaded word, used to mean different things. The type of "stereo" that a two channel of PA provides is generally not the same as the type of "stereo" that reproduction over two speakers or head-phones provide. Usually there is much less "close your eyes and you can still point at the particular instrument" type of imaging through a "stereo PA", because that type of stereo would only work for audience members sitting in the center. But other stereo aspects which convey a different kind of dimensionality can be used that work across a widely-distributed audience. Certain sounds can be dynamically panned around with movement heard from everywhere, sources can be "spatially enhanced" with chorus, delay, or what have you. Mostly conveying "stereo effects" rather than static image positions. Yeah, there may be a little static panning, say of drums, but not much.
If we record using only a single channel we flatten that complexity down to mono. Take the example of a single close mic'd SBD channel. Lets say a single vocal mic. The mic is placed close to the singer to pickup only the direct vocal as much as possible. Anything other than the vocal which also gets picked up is also there in that channel, but will be flattened to mono, "mixed in" along with the vocal. To reduce that as much as possible a directional microphone is placed very close to the singer which helps minimize the pickup of everything else, which is about as isolated as that single channel of vocal can practically get.
If you record that SBD feed you pretty much get just that vocal. But if you record using a single microphone from a position farther away, say out in the audience, even a very directional microphone pointed directly at the singer is going to pickup not just the sound emitted directly from the singer themself but also the multi-dimensional sound of the singer's voice exciting the acoustics of the room. If there are any other sources of sound in addition, onstage, audience members, whatever, they get included as well.. and it all gets flattened to mono. We cant totally eliminate pickup of the sound of the audience members and the sound of the vocal bouncing around the room. We can only arrange things to maximize pickup of the direct-sound coming from the singer, and minimize the pickup of everything else as much as possible.
Ok so instead of one microphone say we use two and point them both directly at the singer. Since both are pointed directly at the singer there is not any additional "audience and room sound" than there was before when using a single microphone. Our primary goal is maximization of the singer over everything else, so we don't want to point the second microphone elsewhere. Instead we keep both pointed at the singer and introduce use some space between the two microphones. We now captures an additionally aspect of dimensionality. The room and audience stuff pretty much remains at the same level as before* but isn't mashed in with the vocal as much. It's instead spread out more. This type of stereo is somewhat more akin to "PA stereo" than typical home playback stereo. When we want as much clarity and focus on the primary source as possible it makes for a quite reasonable approach. Increasing the spacing between a stereo pair of mics setup with very little, even no angle between them to achieve reasonably good sounding stereo playback is the essence of the Improved Point At Stacks microphone technique, and leans on stereo aspects other than static level differences between channels, somewhat similar to how stereo PA mixing works.
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Just came across this thread. It can work, but..
Method A (simpler, more clear immediate result)
1) Place the two cardioids as close together as possible, pointing the same direction. I'd actually tape them together, just don't cover the side vents. Record each microphone to a separate channel as usual - you can use a two channel recorder for this if a multichannel recorder is not available. Produce a steady tone or noise on your phone and place that directly in front of the recording rig. Record some of that noise using identical gain for each of the two channels.
2) Transfer the recording to the computer. Flip polarity on one channel (normally the right one, but doesn't matter in this case). Sum the two to mono. Place the faders for both channels at 0db gain and listen to the noise. Slowly move one of the two faders.. move it up, move it down.. Search for the point where you achieve maximum cancellation of the noise that was being produced by the phone. You wont achieve total cancellation, but you do want to fine the point where the cancellation is strongest and the noise is quietest. Once you find that, note the difference in gain between the two faders. If the mics are perfectly matched, both faders will have the same position. If they aren't you'll know know which is more sensitive than the other, and by how much. At that point if you mute either channel the noise should increase significantly, but with both unmuted, the noise should be as quiet as possible. Once that's done, you'll always apply that difference in gain between the two cardioid channels which will get summed to produce the mono Side signal. More on additional ways of improving the match in a later post..
ss if you end up using this for actual recording and the particulars of how you end up go about doing it, the ability to achieve a decent fig-8 null is going to be a key indicator of probable success and can be loosely confirmed via these tests. You can do them without any additional equipment, and if they work out, things are promising moving ahead..
Thanks Gutbucket for pointing out this important key to success, and for proving such clear instructions.
As I don't have a multitrack recorder, my only feasible way to go is to electrically sum the channels to turn it into a mono channel, then connecting the mid microphone as 'the other channel'. I do realize that the CSS's would have to match well to get acceptable results with this setup, so I gave your Method A a go...
I've created two test tracks: One with a 1kHz beep (1 second beep, one second silence, repeat), one with white noise, and played these through my stereo set. I've put the two CSS's together with a tiny elastic band. (The CSS's are so tiny that it is almost impossible to tape them together without covering the vent holes). I put them close (about 7") to the speaker and played & recorded the test tracks at the highest volume allowed without getting complaint from the neighbors (to minimize influence from ambient noise).
When doing the trick described in step 2 (after normalizing the recordings), after applying a -0.3dB attenuation to one of the channels:
- I got the beeps down from ~-3dB to ~-18dB VU level
- I got the white noise down from ~-3dB to ~-12dB VU level
This is the best volume reduction I could achieve, which would mean the CSS's sensitivity would about 0.3dB apart.This doesn't sound too bad for using the electrical sum of the two, right? I don't have much choice anyway :(. Or would you think this difference in sensitivity is already disastrous when doing electrical summing?
While processing the results of the test track recordings I did notice once again how incredibly noisy these mics are. (Especially since I now can compare with the SP-CMC-4's and the Clippy's I recently got.) I've made so many great loud concert recordings with them over the past decades, but result with lower volume recordings is simply not good.
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Getting somewhere!
Okay, let's make a few assumptions: Let's assume the only difference between the two mics is that slight difference in sensitivity, frequency response and phase response are identical, and we somehow achieve perfect geometry. In that case, flipping polarity of one channel and summing the two will produce a slightly lopsided fig-8 pattern. The null plane will skew toward the less sensitive mic side somewhat. You essentially create a pattern somewhere between fig-8 and hypercardioid, pointing in the direction of the more sensitive mic.
If you were to further increase the level difference between channels, say by incrementally reducing the gain of the less sensitive mic, the null plane will continue to shift further toward the less sensitive side and become more cone-like as the pattern morphs through supercardioid and eventually to cardioid once the less sensitive mic contributes nothing.
How asymmetric is the resulting fig-8 pattern? You might try putting the two mics together facing opposite directions as described in method B and set things up so as to be able to monitor through closed headphones while recording or in rec/pause. Listen while moving a constant noise source around the the mics (as mentioned above, it will probably help to do this outside where there are few reflections and little room reverberation). Doesn't have to be very loud, but the headphones or in-ears need to isolate well. While moving the noise source around the mics listen for the drop off in sensitivity which defines the null-plane. In that way you'll be able to determine how far off-center it lies.
The more off center it is, the farther the stereo image will be panned over toward the more sensitive side when using the sum as Side channel in a Mid/Side recording. If its close enough to center the difference in sensitivity may not matter much.
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I don't have much choice anyway :(
Actually you do.. or might, depending on the gear you have at hand. Even if the plan is to differentially sum the to mic signals to a single channel at the balanced input to the recorder, there is still a way you can adjust levels prior to that summing so as to produce a more symmetric fig-8 pattern.
You just need to use preamp that features separate gain adjustments for each channel. You can then match levels by carefully tweaking the separate gains, and lock them down so they can't be changed. I've done it myself using a CA-UGLY (which features independent channel gain adjustment trimmer pots). In that case I was recording two back-to-back cardioids to two channels of a DR2d. Recording both channels would have allowed for adjustment of levels afterward if needed, but I was using the CA-UGLY to power the two cardioids anyway, so it made sense to get the levels matched prior to the signal reaching the recorder. More details on that if interested. It works but may be fiddly dialing it in as perfectly as possible.
After getting the pattern as symmetrical as possible using the channel gains of the preamp, you'd then switch over from inputting both channels to the recorder to summing them into a single differential balanced input channel instead, freeing the other recorder input for the Mid microphone. Just need to make sure the preamp gains are fully locked down afterward so they don't get changed after that.
To differentially sum into a single balanced recording channel, connect the signal output ground/common from the preamp to pin 1 of the balanced input on the recorder, the left-facing mic + signal to pin 2 and right-facing mic + signal to pin 3. You'll then be recording a symmetrical "fig-8-ish" pattern to a single channel of the recorder.
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Another important detail is the geometry of this thing. More on that later.
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if you look at this as an exercise in understanding what is going on with mid-side processing., it's a great idea. If you look at this as a way to make pleasing recordings, it's a lot of pain for a worse result.
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^ Probably. Fun to discuss and mess around with at least.. and might actually work well enough to prove useful.
I got close to this in figuring out a way to run a Naiant X8 fig-8 as the Side mic in a four channel stealth setup into an unbalanced recorder years ago. I did have the advantage of the Naiant X8, which consists of two back-to-back unbalanced electret cardioids in a single housing, already having its geometry and channel matching worked out. While the X8 is primarily intended as a low cost balanced output fig-8, it can also serve as two separate unbalanced back-to-back cardioids. So I powered the individual capsules separately using the two channels of the CA-UGLY and recorded the unbalanced outputs into separate channels of a DR2d for initial tests. That worked. The next step would have been differentially summing the outputs of the preamp to record the Side channel to a single unbalanced channel. That should have worked fine, but didn't take it farther for other reasons.
Intention was turning the center chest-mounted omni of my 4 channel LRCB torso baffled stealth setup into a Mid/Side stereo pair. The X8 was hung around my neck upside-down, resting just above the center chest-mounted omni. Problem was not so much the unbalanced Side channel scheme but not having sufficient channels to do what I really wanted. Being restricted to four unbalanced channels with the DR2d, I didn't want to give up the existing rear facing omni channel, and running both would have required two DR2d along with syncing in post. Too much hassle. If I'd had six channels available in a pocketable recorder I would have gone forward with it and eventually rigged it up so that the rear-facing omni formed a second Mid/Side pair using the other X8 I have on hand, along with trying a few alternate configurations.
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I don't have much choice anyway :(
Actually you do.. or might, depending on the gear you have at hand.
My gearbox is rather limited. No pre-amp, no multitrack recorder. Just a very limited set of mics, a stereo recorder (FR-AV2), a soldering iron, near zero budget and some curiosity. I feel a bit like MacGyver here. :bigsmile:
It's been very educational so far already, even without having to heat-up the soldering iron yet! When I get near the electronics shop, I'll get the XLR-connector to start wiring things up!
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if you look at this as an exercise in understanding what is going on with mid-side processing., it's a great idea. If you look at this as a way to make pleasing recordings, it's a lot of pain for a worse result.
I certainly don't plan to use this as a replacement for my normal concert taping! Unless I'm blown away with the results of this experiment, which is rather unlikely. :laugh:
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Even if no one actually ends up doing it I think this discussion about how one might produce a DIY fig-8 pattern, along with exploration of the challenges involved and how they might be addressed, makes for a good TS thread. It makes for a good exploration of the fundamentals involved. Actually doing it with the explicit goal of useful recording will probably only suit someone who finds this stuff fun to mess around with and is sufficiently motivated, willing to do the initial setup calibration tests and the needed post recording work that's required to get it to work well.. which ideally means having an extra recording channel available. Despite lacking that extra channel, TheJez seems sufficiently intrigued to give it a go, and may be fortunate if the mics he's using work well enough without additional corrections. So hope remains in addition to the theoretical discussion.
If the primary goal were a high-quality Mid/Side recording rig at reasonable cost, I'd take a serious look at the Rycote BD-10 (fig-8) which I think go for around $800. It seems a proper fig 8. Or to play around with the idea at significantly less cost, the X8 remains available from Naiant at a small fraction of that price. Anther path of reason is a dedicated Mid/Side microphone. I was about to try the BD-10 myself a few years ago when ready to move on from the X8, but went with an integrated Mid/Side mic instead (AT BP4029, about the same cost new as BD-10), which fit my open recording requirements and was available a significantly less cost second-hand from another TS member. I've yet to actually incorporate any Mid/Side stuff into my stealth setups, but thinking about ways I might do that has been a driver for some of my more imaginative fig-8 riggings.
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Okay.. back to producing a fig-8 using two back to back cardioids. Regardless of actually doing it for real or not. Conceptually it works. Getting it to work well practically and minimizing the hassle in doing so is the challenge.
We've talked about how a fig-8 pattern needs symmetry and a sufficiently deep center plane null, and how achieving that requires a good enough match between the two microphone outputs prior to summing them to a single channel. We've also experimentally determined that the mics TheJez is using might match close enough, which is fortunate since he's going to need to sum them into a single recorded channel prior to recording due to the restrictions on channel count. If he were instead recording them to two separate channels, additional things could be done to get the level, frequency and phase responses to match as closely as possible. A "matching EQ" type plugin might work really well for that. Place the two mics immediately next to each together as in Method A. Record something, then use one channel as the target and have the matching EQ adjust the other channel to match. Save those settings. Then put the mics in the intended back-to-back configuration and make the desired recording. Make sure not to accidentally swap mics or mic channels, and apply the matching EQ using that saved setting each time prior to the polarity flip and summing. Use the resulting Side channel in the conversion from Mid/Side to L/R.
^ The same method can be used to improve the match of any pair where the response of the two mics differ somewhat. It can improve the stereo recording quality that is achieved from a lesser quality pair of mics. If the two mics sound audibly different, best to match the less good sounding mic to the better sounding one.
A close match is always good for any stereo technique, but is more important in some cases than others. In this case its particularly important, because otherwise the shape and symmetry of the virtual fig-8 pattern that results from the sum will suffer spatial distortion. This is very similar to optimizing an ambisonic mic, where all four of capsules must match very closely in order for the virtual polar patterns that result from conversion of the raw A-format output from the microphone to ambisonic B-format WXYZ or directly to L/R stereo, to accurately reflect the desired polar patterns. Using that analogy, the raw output from the two cardioids is analogous to A-format from the ambisonic mic, and the Side channel which results from the post summing is analogous to the Y channel of B-format. Mid/Side is analogous to B format, which is then converted to L/R stereo.
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A close match between channels isn't the only requirement. Another is the physical geometry of the arrangement of the two mics. Here's a question I don't yet have a good answer for: How close together do the two back to back cardioids really need to be?
Conceptually-
The closer together, the more consistent the resulting pattern at all frequencies. Spacing between them will cause the fig-8 pattern to begin to break down above some frequency. The center null plane remains but the smooth fig-8 pattern pattern begins to go multi-lobe and spiky instead of forming a smooth two-lobe 8 shaped pattern. Does that matter? Maybe not so much at the highest frequencies where our directional hearing albitites aren't particularly astute. The polarity inversion and Mid/Side matrixing will make whatever complex pattern that occurs up there behave symmetrically at least. It may end up being more pseudo-stereo up there than a reflection of accurate image positioning, but that probably doesn't really matter as long as it sounds good. There are different kinds of stereo as discussed earlier in the thread, perhaps that kind of more "PA like stereo" up top is good enough. We can't achieve perfect coincidence, but only need to get it close enough. How close does it need to be?
Practically-
Is the two inch spacing as achieved by TheJez's Lego mount (+T) close enough? I don't know. I do know that the outside dimension of the Naiant X8 which uses two back-to-back cardioid elements to form a fig-8 measures 34mm (1.33"), so the center-to-center spacing between it's diaphragms is slightly less than that. I used Naiant X8 as a Side channel mic for years and was quite happy with it, although I always used that Mid/Side pair in arrays that included additional mics - a less demanding application than a single Mid/Side pair intended to be used on its own would be. Two inches looks to be about the size of the Oktava MK-012 fig-8 adapter (https://www.oktavausa.com/mics/product/mk-012-small-diaphragm-figure-8-adapter/) which combines two cardioid capsules to produce a fig-8. I've not used that, but I think EmRR has and might be able to comment on it when used as Side channel.
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Let's back up a bit. This is can be simpler than it seems. Think of TheFez's back-to-back cardioid arrangement as an X/Y pair.. because that's essentially what it is..
[snip..] why not just record x/y @ 90* with the cards you have, decode from stereo to raw mid-side, then back to stereo with the desired m/s ratio. I believe there are dsp plug-ins that will allow you to process stereo> m/s> stereo in one step.
Sure you can do that. If you don't change the ratio of Mid to Side, what comes in goes out, and is essentially how vinyl record recording and playback and FM stereo transmission along with other things work. We can take L/R stereo and convert it to sum/difference, then convert it back again. The difference signal is equivalent to the Side channel of a Mid/Side pair.
Things may get more complicated if we alter the ratio (level balance) between the Sum and Difference (Mid and Side) channels before converting back to L/R again. It's then no longer a fully lossless conversion, and errors begin to accumulate.. from non-perfect coincidence, from a more extreme change of ratio.. and need to be listened for. This is where the cautions morst and grawk mention about converting L/R to M/S and back come into play.
For any X/Y pair, the level of the difference signal varies with choice of polar pattern and X/Y angle. Opening up the X/Y angle to 180 degrees, along with using a more directional pickup pattern, maximizes the difference signal as much as possible. TheFez's back-to-back cardioid arrangement can be thought of as an X/Y pair which has been optimized for this particular role, from which the Mid content will be discarded, leaving only the Side channel information.
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Thank you for a very nice discussion. Also thanks to Gutbucket for the contributions—we completely forgot that it’s necessary to make sure the capsules are matched. If they have different sensitivities, it might be possible to solve it by adding a resistor to the more sensitive output. But that would be tailored to a specific preamp. Because the required resistor value is depended on the microphone’s output impedance and the preamp’s input impedance.
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A "matching EQ" type plugin might work really well for that.
Thanks for the tip! I could use this to verify how much the mics match (or mismatch) (or even to correct a mismatch...if I would have a recorder with more than two tracks :( )
Unfortunately, long working days prevent me from making speedy progress with this experiment.
So far for all the (very interesting and educational) theory; I finally got the the XLR connector and soldered the two signal lines (left and right) to the appropriate pins of the balanced input of the recorder! (and ground of course to the remaining pin :) ). I walked around my living with my poor-man's mid/side mic and a few sound sources here and there (tv, stereo set) and a good isolating headphone connected to the recorder to monitor the result. It didn't sound bad at all and I had the impression that playing with the m/s balance on the recorder made a noticable difference in the spaciousness of the sound. So far so good. I do think (again) that the noise of the CoreSound mics might be the biggest spoilsport for this experiment...
Next step will be finding some nice spots to put the setup in practise. Hopefully the upcoming vacation period will provide some oppertunities and time. I'm thinking about the local ice rink full of screaming and shouting kids, the railway with passing trains, things like that. We'll see, I'll keep you posted! Thanks again to all for your support, especially Gutbucket! This is greatly appreciated.
Merry Christmas to all!
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Right on. Let me know how the test recordings work out once you can make a few more.
A "matching EQ" type plugin might work really well for that.
Thanks for the tip! I could use this to verify how much the mics match (or mismatch) or even to correct a mismatch...
Yes, use of a good matching EQ routine to more closely align the response of two mis-matched mics that will be employed as a stereo pair is likely to improve the quality of a lot of recordings made with cheap mics! I've long intended to start a thread here at TS about doing just that, but never got around to it.. so here it is!
Many tapers already EQ each channel to best effect by ear as needed. This matching EQ technique would not eliminate the usefulness of doing that in more subtle ways for specific recordings as required. Rather, it would be a base-line correction that would be applied to all recordings made with that particular pair of mics, prior to other post work. In addition to matching frequency response it would also correct for differences in sensitivity.. so no need to run slightly different gains on the recorder to compensate for one mic being slightly hotter. The initial response measurement of pink noise with the mics placed parallel and immediately next to each other need only be done once. Likewise the matching routine only need be run once on those noise files and the resulting compensating EQ curve saved. Then just apply that curve each time, and be careful not to mix up the two mics or which channel each is assigned to.
[edit- To be clear, this is in no way intended to substitute for using properly matched high-quality stereo microphone pairs, yet should make for better-quality stereo recordings made using not-so-high-quality mis-matched mics.]