Phase issues using M-S (Blumlein pair) for drum overheads

[rim]

Hello all! Haven't posted much recently but I still lurk every so often.

 

I have recently bought a pair of Cascade Fatheads (ribbon figure 8 mics) and finally trying them in an M-S configuration for drum overheads. When I analyze the output of the overheads with Waves PAZ Position, I see a lot of Anti-Phase occurring throughout the track - almost as much/as loud(?) as in the normal stereo range.

 

I have the mic pair positioned as referenced in this link: http://www.cascademicrophones.com/BrochureFinal_16.pdf

i.e., the Mid is pointed towards the center of the sound source and the Side is at a 90 degree so it's pointed towards the side, and both are pointed at a 45 degree angle toward the source (the document's diagrams explains it better).

 

So I'm using the Waves S1 Stereo Imager to convert the M-S signal to a stereo signal. I create an Aux stereo track with S1 Stereo Imager as the plugin (it's set to receive M-S input and L-R output) and I've set up this track input to bus 13-14. I then set the output of the Mid track to bus 13-14 and pan it full Left and the output of the Side track to bus 13-14 and pan that full Right. When I view the PAZ Position, I see a lot in the Anti-Phase. Though it sounds OK to me, I haven't heard it without Anti-Phase so I really don't have anything to compare it with.

 

Since this is also my first time using the S1, I also tried to convert the M-S signal manually. I pan the Mid Center, I pan the Side hard Left, I create a new Audio track and I copy the Side track, invert its phase and pan it hard Right. When I look at PAZ Position, I'm getting the same Anti-Phase output like with the S1 so I'm either doing both right or both wrong but I'm getting consistent results.

 

So I'm starting to wonder whether I'm doing something really wrong or is this normal for an M-S recording? I think I read in the link above that the Mid should be a cardiod pattern so I replaced the Fathead in the Mid position with an AKG 414 in cardiod mode but I still saw similar Anti-Phase.

 

I'm running ProTools 6.4 on a Windows XP SP2 PC if that makes a difference.

 

Oh, the room the drums are in is just your standard 8x6 with 7 foot ceilings. Basically, a room in my basement. I did place the drums at an angle (so the drummer's back is toward a corner of the room) and near the middle of the room to prevent phase issues but it doesn't seem to help. I have a "column" of acoustic foam (a sheet of acoustic foam rolled into a column) in the corner and a blanket on top of it since the column doesn't go all the way up to the ceiling but it doesn't seem to help much either.

 

Anyone have suggestions?

 

Rim

[Phil O'Keefe]

I don't have time to check that link right now, but let's get something cleared up before the discussion goes too far... are you trying to run through a M-S decoder?

 

If you're using two figure 8 mikes, crossed at 90 degrees, it is a Blumlein pair, not Mid-Side.

 

http://www.eqmag.com/article/blumlein-pair-stereo/jul-07/29600

 

http://www.eqmag.com/article/mid-side-recording/Jun-07/28990

 

 

Gotta run - I'll check back later.

[Phil O'Keefe]

IOW, you don't need to use that M-S plug in when running a Blumlein pair! Just pan the two mikes L/R. Adjust width as desired.

[Lee Knight]

IOW, you don't need to use that M-S plug in when running a Blumlein pair! Just pan the two mikes L/R. Adjust width as desired.

 

Yeah. Two totally different techniques. The decoder is giving you that phase weirdness. MS relies on flipping polarity of a multed figure 8 mic signal along with an additional cardiod mic as the "front" mic.

 

The Blumlein technique requires TWO figure 8 mics positioned in an X config. Point the crosshairs of the X at your center target. No decoding required or desired. Just pan the two mics out and you've got a Blumlein pair. No phase weirdness at all.

 

Lose the decoder and you're set.

[MrJoshua]

Note: the following is my own opinion and, like usual, is quite possibly wrong.

 

Haven't we had a discussion like this before? While it isn't technically correct to use two figure-8 mics as a mid-side pair, it can be done. The benefit to using a cardioid as the mid mic is just the rear sound rejection. Think about it based on the job of the mic. (Also, the original poster did mention that he had started using a cardioid 414 as his mid mic after reading that the mid should be cardioid.)

 

The job of the mid mic is to capture a mono image of the source. If you're in a small room, or if you're trying to reduce crowd noise at a show, etc, then using a cardioid mic for this is a great idea due to the rear rejection. If you're in an environment where the noise coming into the back of the mic won't have a significant impact on the recording, then using a figure-8 mic to capture a mono image of the source will work.

 

But like I said before, that doesn't change the fact that a true mid-side pair has a cardioid center (a point that I think I failed to convey the last time this came up). Just because it isn't textbook-correct to use two figure-8 mics doesn't mean it won't sound good, though. I use a pair of Fathead mics as a mid-side to record drums all the time, and so far nobody has gotten too upset with me except for a few people on the Internet...

 

I mean, honestly, it's just like recording anything else. Use the mic or combination of mics in whatever configuration sounds good to you. Is it good to know the definitions of terms like mid-side and what you're supposed to do to use them? Absolutely. But it's even better to understand why they do what they do, so you know which rules can be broken to achieve different results.

 

I spent a lot of time thinking about this after I got reamed for it last time, haha.

[Lee Knight]

Yeah but...

 

The cardioid, or fig. 8 "a", for that matter in an MS config is the front mic. With a Blumlein, the 2 mics are treated identically. So you could of course create an MS with 2 fig 8's but you'd have to point, pan, and process them very differently.

[MrJoshua]

 

Yeah but... The cardioid, or fig. 8 "a", for that matter in an MS config is the front mic. With a Blumlein, the 2 mics are treated identically. So you could of course create an MS with 2 fig 8's but you'd have to point, pan, and process them very differently.

 

 

True, but in the original post, it sounds like he has the mics pointed, panned, and processed as a mid-side pair, both with a figure-8 as a mid and later with a cardioid 414 as the mid. If he has the mics set up and aimed as a mid-side pair, panning them as a Blumlein pair won't do much good and will probably sound kind of odd.

[Lee Knight]

Hmmm. I admit, I didn't read the whole post initially. It looks like he is setting up an MS.

 

OK, so... wouldn't you see a lot of out of phase information on a scope with MS? That's what you're doing in MS, flipping polarity. So what happens when you collapse to mono? You should be able to pan the side mics into mono and have it cancel completely, hearing only the front mic at that point.

 

Does the phasing issue visually go away when collapsed to mono? And does it sound weird or just look weird?

[Lee Knight]

BTW, ever consider just going Blumlein for your OH's? It sounds great with those Fatheads.

[rim]

Ok, so I'm still confused what I'm trying to do.

 

I ordered this stereo pac which states includes a Blumlein bar (so I assumed how they have it configured is a Blumlein pair)

http://cascademicrophones.com/cascade_1.html

Here's the image only:

 

And then the other link, the PDF file, says "HOW TO USE OUR

MICROPHONES" and the next session is "A Guide to

Recording in MS".

 

So that's why I'm thinking I set up the mics as a Blumlein pair but I'm recording M-S. Clearly I'm confused.

 

I will definitely try panning the "Mid" hard left and the "Side" hard right and see how that sounds.

 

So what is the difference between Blumlein pair and M-S on the recording process (outside of how to "process" them for playback)? Is it just that M-S should be using cardioid as the Mid? Or is it also that if I'm using a pair of figure 8 in Blumlein pair, they should be aimed so both mics are equally diagonal to the source, unlike M-S where the bottom (Mid) mic is pointed directly at the source and the top (Side) mic is perpendicular to the source?

 

Don't know if I'm explained that well. Let's say pointing a mic directly at the source is 0 degrees. In an M-S, the Mid is at 0 degrees and the Side is at 90 degrees. I believe that is correct. So, is the Blumlein pair supposed to be that the bottom mic is 45 degrees to the left and the top mic is 45 degrees to the right of the source? I guess that would make sense that you'd then pan each mic left and right.

[MrJoshua]

You have it right - the difference is how you aim the mics.

[Phil O'Keefe]

True, but in the original post, it sounds like he has the mics pointed, panned, and processed as a mid-side pair,

 

Actually, this part of the OP is what had me a bit baffled:

 

the Mid is pointed towards the center of the sound source and the Side is at a 90 degree so it's pointed towards the side,

 

Sounds like a M-S setup, but...

 

and both are pointed at a 45 degree angle toward the source.

 

That, plus the fact that he is using dual Fig 8 mikes, certainly sounds like Blumlein.

 

So which is it? Is he "aiming" the 'side' mic 90 degrees relative to the sound source (IOW, with the null point of the figure 8 mic pointing towards the sound source, and the pickup lobes aimed to the sides) as with a M-S configuration, or are both mikes pointed 45 degrees towards the source, as in a Blumlein pair?

 

He's describing both as far as I can tell from the first post - thus my request for clarification.

 

If you have a pair of figure 8's, and want to use them as drum overheads, I would recommend forgoing the "modified" M-S idea (again, a "true" M-S pair uses a cardioid and a bi-directional) and just run them as a Blumlein pair. Both methods (M-S / Blumlein) should collapse to mono nearly equally as well. The major difference would be the amount of "room" you'll pick up, with the Blumlein offering a touch more than a true M-S setup. Of course, if you're experimenting with a fig 8 as the "mid" mic, you'll get just as much ambiance with the "M-S" pair.

[MrJoshua]

Actually, this part of the OP is what had me a bit baffled: the Mid is pointed towards the center of the sound source and the Side is at a 90 degree so it's pointed towards the side, Sounds like a M-S setup, but... and both are pointed at a 45 degree angle toward the source. That, plus the fact that he is using dual Fig 8 mikes, certainly sounds like Blumlein. So which is it? Is he "aiming" the 'side' mic 90 degrees relative to the sound source (IOW, with the null point of the figure 8 mic pointing towards the sound source, and the pickup lobes aimed to the sides) as with a M-S configuration, or are both mikes pointed 45 degrees towards the source, as in a Blumlein pair? He's describing both as far as I can tell from the first post - thus my request for clarification. If you have a pair of figure 8's, and want to use them as drum overheads, I would recommend forgoing the "modified" M-S idea (again, a "true" M-S pair uses a cardioid and a bi-directional) and just run them as a Blumlein pair. Both methods (M-S / Blumlein) should collapse to mono nearly equally as well. The major difference would be the amount of "room" you'll pick up, with the Blumlein offering a touch more than a true M-S setup. Of course, if you're experimenting with a fig 8 as the "mid" mic, you'll get just as much ambiance with the "M-S" pair.

 

I believe the "both are pointed at a 45-degree angle toward the source" comes from the booklet that Cascade includes with the Fathead II Blumlein pack, where they say that for ideal mid-side recording, the mics should be located above and in front of the source, such they they are angled down at 45 degrees in order for the mid mic to point at the source. So it's a vertical angle, referring to the height of the microphones. The mid mic is still pointed straight at the source, with the side mic 90-degrees off-axis, but now the axis is at a 45-degree angle up from the source.

 

This is one of those things that's easy to describe with a diagram and hard to describe with text.

[Lee Knight]

I would suggest you go straight Blumlein for your overheads. No decoder, no front mic, no side, just an even X. I've done it with the exact setup you have, the bar, the Fatheads, and it sounds great. Just point the spot in between the two mics at the snare. You're not pointing a capsule directly at your target, you're pointing the middle if the X at it. So you could go just over the drummer's head, pointing down at the snare. If you can center the snare and kick in that crossed pair you're good. Probably a little to his left from behind so you're getting the floor tom in the picture. Angled so the rest of the kit splays evenly into the mic pair.

[rim]

Ah, ok, I believe I have it now. I'll clarify so I don't confuse anyone else.

 

How I had it set up is in M-S configuration but with a pair of figure 8 (a "modified M-S"). The 45 degree I mentioned originally is, as MrJoshua pointed out, is the side view angle.

 

Lemme try some ASCII "art" to try and make things more clear.

 

Side view of the mic stand where the mics are attached to:

source

(the boom of the mic stand is leaning towards the source at 45 degrees)

 

Furthermore,

 

Top view of the a pair of figure 8 mics in a modified M-S config:

s

o

u +

r

c

e

 

Top view of the pair of figure 8 mics in a Blumlein pair config:

s

o

u x

r

c

e

 

I will definitely record the drums again as a Blumlein pair and see how that sounds.

 

Thanks everyone!

[rim]

Tried Blumlein pair last night and only got occasional phase issues so it is much improved. Unfortunately, my room is still too small and my drumming is still not up to par.

 

Thanks for all the help!

 

Rim

[MrJoshua]

Tried Blumlein pair last night and only got occasional phase issues so it is much improved. Unfortunately, my room is still too small and my drumming is still not up to par. Thanks for all the help! Rim

 

Tiny room with bad drumming? Are you sure you're not me?

[rim]

Tiny room with bad drumming? Are you sure you're not me?

 

Heh. If I really was you, I would've known how to Blumlein, instead of MSing my Blumlein (or was I Blumleining my MS)?

 

I better stop before I confuse myself again.

[Phil O'Keefe]

So what is the difference between Blumlein pair and M-S on the recording process (outside of how to "process" them for playback)? Is it just that M-S should be using cardioid as the Mid? Or is it also that if I'm using a pair of figure 8 in Blumlein pair, they should be aimed so both mics are equally diagonal to the source, unlike M-S where the bottom (Mid) mic is pointed directly at the source and the top (Side) mic is perpendicular to the source?

 

Correct on all points. When using a Blumlein pair, both mikes should be aimed 45 degrees from the center of the source. With M-S, the center mic should be aimed directly at the source, while the side mic should be aimed perpendicularly.

 

Here's a pic of two of my mikes, set up as a Blumlein pair. Both are figure 8 ribbons, like your Cascades:

 

 

And here's a picture of two of my other mikes, set up as a M-S pair. The top mic is set to a figure 8 polar pattern, and the bottom is a fixed cardioid mic:

 

 

In both cases, the camera is the "sound source" - IOW, the mics are oriented correctly, assuming the camera position represents the location of the sound source.

[haze015]

shouldn't be having phase issues with M/S, the whole idea is the Side mic is cancelled out when summing to Mono.

 

And the patent for M/S is actually using two Figure of 8 mics, but it really doesn't matter what you use for the Mid mic.

[Weasel9992]

....not to mention that in MS the Mid mic is generally cardiod, sometimes omni, NOT figure-eight. That's the reason you were getting all kinds of phase irregularities with the decoder. You had it set up as blumlein and had the pair pointed the wrong way.

 

Frank

[MrJoshua]

 

....not to mention that in MS the Mid mic is generally cardiod, sometimes omni, NOT figure-eight. That's the reason you were getting all kinds of phase irregularities with the decoder. You had it set up as blumlein and had the pair pointed the wrong way. Frank

 

 

OK, I'm sorry, but how could using a figure-8 center mic instead of an omni (which you seem to indicate is acceptable) possibly cause phase irregularities?

[haze015]

....not to mention that in MS the Mid mic is generally cardiod, sometimes omni, NOT figure-eight. That's the reason you were getting all kinds of phase irregularities with the decoder. You had it set up as blumlein and had the pair pointed the wrong way. Frank

 

 

 

blumlein used two figure of 8 mics when he came up with M/S......

[The*Ataris]

Kind of off topic, but probably not deserving of another thread...

 

...anyone ever use an MS pair on a vocal track? Could that sound really cool on a more open sounding song? I've never actually head of someone trying this.

[UstadKhanAli]

I have not tried that myself for a single vocal.