How does diaphragm size/polar pattern relate to mic applications?

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dafduc,

Sorry, I was at the AES show when you posted and your question slipped in under the radar.

For those of you not familiar with a Leslie, it uses a rotating horn for the the high end. There's only one rotating horn on top (the other end of the arm is a counter balance). There's also a rotating baffle for the low end speaker.

Probably the widest "swirl" would be a couple of mics placed 90° apart, one pointing towards the louvers on one side, and the other pointed at the louvers on an adjacent side, both mics about a foot away from the cabinet. Some people also use a 421 or similar dynamic to mic the bottom speaker and mix it on with the horn tracks.

But like anything else, it depends on how the Leslie is supposed to fit in with the other tracks. If it's not the featured instrument, use a 57 on one side, aimed at the louvers and be done with it.

If you're recording Booker T., mic everything you can think of, even putting a mic on the keyboard to capture keyclicks and any singing along - you don't hafta use them in the final mix.
 
Originally posted by Bigus Dickus
Harvey,

You touched on grand pianos several times, but never really got that in depth on them. To give you a bit of background, I want to make recordings of my grand in my home. It's in a fairly small and dead room, and this is the only instrument I intend on recording in the foreseeable future.

If I have indeed understood things, then I should be looking for a small diaphragm condensor or dynamic microphone for accuracy instead of coloration (that larger diaphragms give), and a fairly low self noise to catch intimate passages adequately. I also gather that I should be looking for an omni-directional or wide cardioid pattern. And, I should probably look for a pair (matched if possible) for stereo recording.


Yes, those mic patterns are usually the best choices for people in your situation (i.e., small, non-treated room, home recording, small budget, and not a lot of previous mic placement/acoustic treatment knowledge). That wasn't meant as a putdown, BTW. You have the advantage of time, compared to studio recordings, where the clock becomes very important.

Stereo piano recordings are usually the most natural sounding, as far as recording techniques, but it's also possible to do an artificial stereo recording that duplicates the emotional impact of a stereo recording, without using recognized stereo techniques (like recording from underneath the piano for the low notes, and from above for the treble).

I'll stop here and ask a question: there was a list of possible microphones given a few pages back, and you gave some general comments on those (and I've made a note of that list). In my case, I don't have the luxury of having multiple microphones to play with looking for the sound I want, or a convienient way of purchasing on trial different mics to audition. Instead, I'll have to make the best informed decision I can, and hope that the mic pair I purchase is satisfactory. Could you give any suggestions for a specific mic? If you only had one shot at recording a grand (not in a concert hall, mind you), and could only choose one mic model and hope for the best, what mic would you choose?

I can't really answer that without hearing the actual room and the actual piano. My first concern woulld be the actual acoustics of the room, and then I would be concerned about the evenness of the tone of the piano.

Am I hearing any peaks or dips in the sound as you play while I walk around the room? Do I need to put up some packing blankets or move furniture around? Is the piano thin or full in different ranges? Is it bright or mellow?

As far as mics, I'd be more concerned about acoustics and placement than I would be about the choice of microphones. Most 1/2" condenser mics are pretty similar, so whichever mics were fairly flat, and low noise, would be the ones I'd bring. I'd also bring a pair of the Behringer ECM8000s, just on the chance they MIGHT work well, since $70 for a pair is kinda a no-brainer.

Now, about placement. As I said the room is fairly small and dead (and could easily be made 'more dead' if that would indeed be helpful). From reading your wonderful advice, it would seem that an X/Y pair (or perhaps even near-coincident) a couple of feet to the side of a high-stick lid would be a good place to start with placement... if the room was nice. Mine is not. Perhaps bringing the mics closer (under the open lid) to record in their near-field would help to reduce the effects of room modes and odd wall reflections.

Yes, no, maybe. You have the luxury of time. Try everything you can think of. As I said, my first concern would be the effects of room modes and odd wall reflections, and I would try to eliminate them (or reduce them) as much as possible. Once those are tamed, then it would be time for experimenting with mic placements.

Which brings me to my second line of questions. I've heard several people speak of good results with wide spaced micing under the lid of a piano. Wouldn't that cause phasing problems? I'm not really interested in mono compatibility (since this will be primarily for friends and family), but I want to avoid as many complications as possible. Would an X/Y setup under the lid have trouble with a balanced frequency response, especially considering that some strings might be in the near-field while more distant ones would not? It would seem for that omnis might be better suited than cardioid...

Yes, no, maybe - see paragraph above. First, fix the room, then understand the instrument (and the way it radiates sound), then choose the best location to capture the desired sound. Usually, my motto is, "The worse the room, the closer the mics".

I suppose the bottom line questions is: If you were attempting to record a grand in such a room, where would you start? I know that mic placement plays a role in mic choice as well, so that makes it that much more difficult for me. I think you understand what I'm after... the crucial part is choosing a mic pair that is workable, and I can play with placement ad infinitum (but starting suggestions are nice).

All the above suggestions would be the way I would approach recording a strange piano in a strange location. But if it's a paying gig, I would bring almost every damn mic I had that I think just might sound good. That's not an viable option for you. What's your budget for mics? Is the piano bright or dark? What kinda music? What registers will the bulk of the playing be in, and how does the piano sound in those registers? How much is the room altering the sound? Without a better handle on those questions, I can't help much more on your situation.
 
dafduc said:
Thank you, Harvey!

So the 421 would be about a foot away, too?
Yeah, about that, and pretty low to the floor.

The great thing about Leslies is the sound. The bad thing about Leslies is the mechanical noise when you get too close.
 
Wow, I didn't expect a reply so fast (nor do I expect to be so lucky again)! Though you may have thought your answers were vague, they've already helped tremendously in just confirming that I wasn't completely in the dark anymore. Feeling more confident that I do actually understand a bit of what you have taught, I will be less timid in trying things.

To fill in a few of the holes:

Harvey Gerst said:
[What's your budget for mics?
I'd be willing to spend a couple of hundred on mics, maybe ~$300 maximum.

Is the piano bright or dark? What kinda music? What registers will the bulk of the playing be in, and how does the piano sound in those registers?
There is a Sibelius piece that covers practically the entire range, within a couple of notes of either extreme. I also want to record a Listz etude that covers most of the range as well. The piano is a Baldwin artisan, and has a wonderful sound from about 400Hz down. It gets a bit metallic sounding around 2000Hz, but I'm suspicious that it may be the room as much as the instrument. From ~5000Hz up it's pretty smooth again. As far as musical style, the Liszt etude is both beautiful and very dynamic, as is the Sibelius piece. Both have some very soft, and some rather powerful sections. I'm naturally a heavy player as well, and tend to lean towards that style. However, I also want to include a nice Chopin prelude or two.

How much is the room altering the sound?
That's difficult for me to say, because I've never heard the instrument in any other setting. My guess is that most if not all of the mid/high range thinness and metallic sound is due to the room. I'm doing some research on what kind of damping might help.

Without a better handle on those questions, I can't help much more on your situation.
You've already helped more than you could imagine. I was lost just three days ago... now I have an idea of where I am headed. I will scour the mic forum a bit more, and see what condensor mics people are pleased with that have low noise and fairly flat freq. response. The most important thing is knowing that the mic purchase isn't going to make or break the recording (sure, I'm sure there is a perfect mic for me, but it sounds like there are many that will give satisfactory results). And as you said, I have all the time in the world to play with placement, and you've given valuable insight on what to try as starting points. If it takes a year to find the "sweet spot" then I'll just be that much better rehearsed when the serious recording comes. More than that, I now will understand when I move a mic around why the sound changes like it does. Nothing wrong with trial and error, as long as it isn't completely in the dark... IMO. :)
 
Hadn't seen this in a while...

Bump before we lose this one in the mists of time...
 
How to make your own multi-pattern microphone

While this thread is near the top, I thought this might be a nice addition, in that it will help many people understand exactly how multi-pattern condenser microphones work.

We are going to make a multipattern mic. You can either actually try this, or just follow the thought process.

You will need two similar sounding cardioid microphnes, the closer the match, the better. If they are side address (like a B1 or MXL990), even better, but a pair pf SM-57s will work fine.

Position them so that one capsule faces forward, while the other capsule is above the first and faces backward (exactly 180°). With side address mics, you can use two stands and position one of the mics upside down over the first mic, with the top of the screens almost touching. Just remember one of the mics shold be facing forward, and one facing backwards.

The forward facing cardioid mic represents the front diaphragm in a multi-pattern mic. The rear facing cardioid mic represents the back diaphragm in a multi-pattern mic.

Bring each mic into a separate channel on the board and set the pan controls on each channel to straight up, with no eq, so that both channels are identical. Bring up the level of just the forward facing mic - keep the rear facing mic turned off. That's exactly what happens when you choose the cardioid pattern in a multi-pattern mic; they shut off the rear diaphragm, just as you have the rear cardioid shut off.

Now start to bring up the rear facing cardioid slowly while you listen to the sound change. Think about what is happening. A cardioid picks up whatever is in front of it, and then tapers off as you approach the rear of the mic. But now, the second mic is picking up the sound from the rear, and then tapers off as you approach the front.

What's happening is that the cardioid pattern is starting to balloon in back as you bring up the rear mic level. When you get to the point where the levels are equal, congratulations, you've just made an omni mic out of two cardioids. As you moved the slider for the rear mic up, you went from cardioid to wide cardioid to omni.

OK, bring the rear mic's slider all the way down, and hit the polarity switch for the rear mic. You're now back to cardioid (only the front facing mic is heard).

Since the rear mic is now reversed polarity, it's gonna act in a subtractive way, taking away some of the sound from the front facing cardioid mic. OK, lets start raising the level of the rear facing mic. Remember, with it off, we're actually starting at the cardioid pattern again (front facing mic only is on). Let's start bringing up the rear facing mic again and try to imagine what is happening to the polar patterns.

The first place any change appears is in the rear (dead center), and at the right angle points. A small lobe starts to appear behind the cardioid pattern and the sides of the cardioid pattern shrink in size. Why? because sounds from the side are hitting both diaphragms and cancelling out a little.

As you bring the level up, the back lobe directly to the rear starts to get bigger and bigger, while the front pattern begins to shrink in width, due to the cacellations mentioned above. Imagine the patterns are like a balloon that you squeeze in the middle. At first the sides kinda shrink till you finally wind up with what looks like the number "8" - two smaller perfect circles. At that point, any sounds coming in from the exact right or left side should cancel out since both mics are hearing it equally, but reversed.

Starting with the cardioid pattern, by raising the slider on the rear microphone (with the polarity reversed), you've gone from cardioid to a narrow cardioid, a hyper-cardioid, a super-cardioid, and finally to a figure 8 pattern.

So, is there a little guy inside a multi-pattern mic woking a little mixer? Yeah, kinda, except they do it with the polarizing voltage on the rear diaphragm, raising, lowering, and and the electronic equivilant of reversing it.

To get cardioid, they just use the front diaphragm. For omni, they turn on the back diaphragm full and add it to the front diaphragm. For figure 8, the reverse the polarity of the back diaphragm and add it to the front pattern.

Every other pattern variation is made by just raising and lowering the level of the back diaphragm with the polarity normal (for all patterns between cardioid and omni), and reversing the back diaphragm's polarity (for all patterns between cardioid and figure 8).

So, do multi-pattern mics make a little more sense now?
 
Re: How to make your own multi-pattern microphone

Harvey Gerst said:

So, do multi-pattern mics make a little more sense now?
Yes, very clear. I never thought of it that way before. Next question, can you substitute using 2 cardios instead of purchasing a multipattern mic in a pinch? A little more work, maybe a bit more variability? Thoughts?


SoMm
 
Yes, actually, you can substitute a couple of cardioids, but the spacing won't get you as accurate patterns as two diaphragms located on the same center line and only a few millimeters apart. You'll also get some phase problems up high (the exact frequencies will depend on the diaphragm size and the distance apart). Some people will hear a slight problem, most people won't. Smaller cardioids work better for this.

That was actually the idea I came up with which eventually resulted in the CAD E-200; use a pair of 1/2" cardioids, back to back, and combine them like a standard multipattern condenser mics. In the original design, I used a pair of matched YASU cardioid capsules, but Equitek decided to go with the Primo cardioid capsules instead, which I always thought was a mistake.

The two diaphragms in a dual-diaphragm multi-pattern mic also interact, since there are holes in the backplate, which are used to create the delay network (and that creates the cardioid pattern).

The whole idea of how to use both diaphragms in a condenser mic to create different patterns is really interesting.
 
BasPer,

I didn't say it was a new concept. The design that eventually became the CAD E-200 I started working on in 1987, as I recall, and I first showed it at the 1987 or '88 AES show in New York. It was called "The Mic" and it created a great deal of interest as the first multipatterm mic under $1,000 (actually, the suggested list price was $399).

And this is hardly a "mighty thread"; just a very big thread that I hope new recordists will find interesting and informative.
 
(And I could probably have dressed my link in better words, because I did in no way mean to imply anything about the CAD E-200. :))
 
"Mighty" or not, I can honestly say that I've learned far more about recording from this thread than from any other single source I've ever seen. It has helped me choose AND use my mics in a way that is much better and more controlled than I could ever have imagined.

Harvey, just by posting what you've posted, you've done wonders for the sound on ALL of my recordings. If I thought you had time for it, I'd love to mail you a CD containing only two cuts; one BH, and one AH . The difference is phenomenal. Thanks again.




(BH="Before Harvey", AH="After Harvey") Just in case anyone was wondering....
 
Chris, I'd love to hear those recordings.

BTW, I wound up using a Behringer ECM8000 to record an upright bass in a bluegrass group and the results were wonderful.

No big setup either, just pointed the ECM8000 straight up towards the ceiling about 3 feet off the ground, positioned about a foot away from the bass, so that the mic came up to the neck/body joint, just to the right of the bridge. I had positioned it there since he was the leader of the group and it was intended to be a talkback mic so we could communicate.

I had planned to take his bass direct at a later session, but it turned out so well for bass, that I just used it in the final track.

Ya just never know. :D

BasPer, no problem. The idea of using dual cardioids was from Neumann's original patents in 1936. I happened to be reading some old AES articles in 1987 and I thought to myself, "Hmmmm, this should also work with just a couple of these new small electret cardioid capsules." and the idea was born.
 
Harvey Gerst said:
Chris, I'd love to hear those recordings.

If you want to PM me your snailmail address, I'll send 'em right out. The difference is amazing.

BTW, I wound up using a Behringer ECM8000 to record an upright bass in a bluegrass group and the results were wonderful.

No big setup either, just pointed the ECM8000 straight up towards the ceiling about 3 feet off the ground, positioned about a foot away from the bass, so that the mic came up to the neck/body joint, just to the right of the bridge. I had positioned it there since he was the leader of the group and it was intended to be a talkback mic so we could communicate.

I had planned to take his bass direct at a later session, but it turned out so well for bass, that I just used it in the final track.

Ya just never know. :D



That's VERY true. I've used the ECM8000 a time or two for the Double Bass as a "supporting solo mic" which only gets faded in during upper register passages. Due to the "thick" color it gets on my bass, it's too much for a whole track, but it works beautifully to fatten up the high stuff. For Bluegrass, the position you describe would be great because it would pick up both the pitch of the notes AND the percussive slap that's needed to drive the rhythm section. If I ever do a 'grass session, I'll try that. :)
 
"He didn't bump you, he didn't hit you. He rubbed you. And rubbin', son, is racin'."

Well, rubbin' may be racin', but this is bumpin'....
 
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