R/E/P > Klaus Heyne's Mic Lab

Is There A 'Correct' Approach To Recording Acoustic Instruments?

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Hi everyone, I would like to challenge a couple of things about recording the acoustic piano, and invite comments.

Most people seem to place their microphones close to the strings.  This will give a different sound from what someone hears standing in front of the piano.  I can see why rock musicians do this as they want a tinkling sound rather than a real piano, and I can see why people do it in a concert hall to filter out other sounds.  But it seems to be the preference for recording classical piano in a studio too, which is paradoxical.  If the sound next to the hammers is superior to the sound a listener experiences then the piano manufacturer has surely failed.  (However, it may just be an inescapable fact of science that piano sounds lose something as they blur together in the air)  Or perhaps microphones just aren?t good enough to pick up the nuances from a distance?  

Even with two or three mics inside a piano I don?t see how you can possibly get an even dynamic across the whole range.  Some strings will be a dozen times further from the mic than others (Although much of the sound comes from the sound board, the sound is stronger near the string).  The use of directional mics will surely exacerbate this.

Cardioids seem to be almost universal but for solo piano there is no need to filter out other sounds so an omni placed a few feet from the piano would seem better.  

I profess no expertise and would be delighted to hear the experts? comments.

Yannick Willox:
Ultimately it depends on the music-pianist-piano-hall combination.

I agree 100% with your view: they have been building piano's for about 200 years, to sound good 90deg sideways, at a distance, and with the audience often sitting lower than the soundboard.

We are lucky to have one 'magical' chamber music/piano solo hall (concert hall of the Royal Conservatory in Brussels). It is a mid size shoebox (660 seats), with the back of the hall curved, probably a bit higher than it is wide. All wooden construction, with a glass ceiling (daylight !). It was constructed around 1870-80.

Whatever we do, wherever we go, there is no way to get a piano sound as good as here (even when the instrument itself is in fact superior): in this hall the 'audience' approach works great. The mic will be on axis, from 1m to 3-4m from the instrument, distance and height depending on the music and pianist. (and directivity of the M mic - yes we always do this in MS). On axis means the mic is at 90deg to the piano, and aimed almost exactly at where the curb starts at the right hand side. Height can be as low as the soundboard to 2.5m up.

But, then we get into different conditions, eg a large chamber, with 1/2 Bechstein, built in 1910. All of a sudden, there is a mic inside the instrument, and a AB couple 2m out. In this case it was the most convincing piano sound.

The point is, a piano is big. It radiates sound in all directions. Some engineers solve this by putting mics all around the instrument, which seems valid but does not work for me. Either you get enough distance to get more of the sound of the piano (which comes back as room sound) -which means a great sounding room- or you try to fake it. While not ideal, we regularly have cases where the latter approach gives better results than the former. You can' win them all ...

What I would like to challenge is the use of LD mics, or any condenser mic for that matter: for me the attack is never clean, always artificial (compared to the real thing). A good ribbon like the SF12 seems to solve a lot.

Unfortunately, a Blumlein approach does not work at all in our magical hall. We are waiting for a cardioid or omni SF1 !

Gunnar Hellquist:
Very good answer from Yannick.

I agree with most of what he says (not that it makes any difference, me beeing a rather beginner in this). You need to look at all the factors, from instrument to room to music to select the best (or even least bad) position for the mics.

I do believe though that true pressure condensor omnis can do a great job on a piano, say DPA 4003 or perhaps Microtech Gefell M296. Have not really loved any usage of cardoids though for classical music.


Barry Hufker:
To me the difference between close micing and "audience" micing is "bloom."  Acoustic instruments were meant to project their sound.  For me, there is a point where the sound become full -- and that is at a distance from the instrument.

The piano lid has one purpose -- to radiate the sound into the audience.  For me, the lid is optional, depending on the music, player, etc.  


I find the most useful rule is stay at least one characteristic dimension away from the instrument to make sure acoustic mixing of all freqs radiated by the various parts of the soundboard has occurred most completely. In the piano, the characteristic dimension is the long dimension of the sound board, some 2-3m in a concert grand.

This is also a useful guide when miking an acoustic guitar. If one examines sound intensity plots of the radiation of soundboards, you can see that in some places and for some frequencies, sound energy is actually travelling back into the soundboard. Placing mikes there will make a very ugly sound.

Close miking of pianos and guitars is a very silly idea in general, and I can often hear the lumpiest, most unattractive results from such practices. One hears only resonant, narrow frequency radiation from just under the mike and this is always dissappointing. Listen to jazz piano recordings when there is a rare couple of octave "run", and you will be able to tell above which hammers the mics are, the notes stick out like ....

The other fact that has great influence on the sound is the volume of the playing. Most jazz and pop piano technique and music rarely gets above mp or mf at the most. This means close miking is more tolerable. For most classical performances on concert instruments the playing is often above f and sometimes fff.

I recorded a CD recently of the Bach Busoni Chaconne and other VERY LOUD piano playing. For this you need to be at least 3m away or it's a disaster on many fronts.


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