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Soundboard and mic placement question

  • 1.  Soundboard and mic placement question

    Registered Piano Technician
    Posted 11-03-2017 23:16
    I recently read a thread on mic placement in a piano, (being tuned), that repeatedly mentioned positioning the mic relative to certain points on the string for best results. OK, using a point on the string as a reference is one thing, but believing that the string itself is being miced is wrong. That is not how sound works in a piano and is why I am posting this question here. 

    The soundboard in a piano takes the vibrations from the strings, via the bridge and, for lack of a better word, amplifies those vibrations into audible sound that we can hear. The sound coming directly off the strings would be almost inaudible if it were not for the soundboard increasing the amplitude of those vibrations and pushing them into the air for our ears to capture. In short, the sound we hear from the piano is coming from the soundboard and not directly from the strings themselves. 

    Most engineers mic a piano based on a combination of trial and error and experience on what works best. And ultimately that's probably the best way to approach micing a piano for music recording. 

    That said: Has anyone ever experimented with Chladni patterns on a piano soundboard to visualize the standing waves and find out where the nodes and null points are for different notes? I think this information might be valuable for mic placement in recording but, more importantly for us, in mic placement for optimum results in ETD tuning's. Especially when the ETD is having difficulty picking up the desired partials of certain notes, which is the real focus of my question here.

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    Geoff Sykes, RPT
    Los Angeles CA
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  • 2.  RE: Soundboard and mic placement question

    Posted 11-03-2017 23:45
    Chladni Patterns make great youtube demonstrations, but is a useless tool for making piano soundboards. IMHO. 

    As to mic position, I'll answer by just rephrasing your question.

    "Is it worth the time to de-string a piano, remove the plate, put sand on it, and test for chladni patterns. Then put it all back together again, in order to determine optimum mic positions?"


    -chris

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    I have a piano in my Nuclear Fallout Shelter, and my competitors don't. How silly is that?

    chernobieffpiano.com
    865-986-7720
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  • 3.  RE: Soundboard and mic placement question

    Posted 11-03-2017 23:47
    I can share my absolute complete knowledge of this subject. Earth works has two mics attached to a rod that sets on each side of the rim. For optimum results place each mic approx 2-3” behind the dampers....one at low tenor and one at treble break.Both mics should be 2-3 “ above the strings. I think each mic is omi directional. The sound is amazing. That’s ALL I know except sound people tell me this system is the best......$3000.00.

    Sent from my iPhone




  • 4.  RE: Soundboard and mic placement question

    Registered Piano Technician
    Posted 11-04-2017 01:59
    I have a collections of mediocre to decent mics.  When I tuned for a customer with money to burn and several excellent mics I negotiated to tune and voice his piano in exchange for testing my mics against his.

    His $3000 mics did sound better than my $200 mics, but not by much.  What we did figure out was that (IMHO) exact mic placement wasn't as important as having more than two mics on the piano.  We used one above each of the musician's shoulders, two over the bridge, two nearer the rear of the piano and one or two for "room ambience".  I like one under the piano (adds warmth).  Then in a mix you can turn each mic off or mix it in as needed.  Each mic added its own qualities and none were as good as all.

    It is my belief that more mics sound better than trying to find "magic spots".

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    Blaine Hebert
    Duarte CA
    626-795-5170
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  • 5.  RE: Soundboard and mic placement question

    Registered Piano Technician
    Posted 11-04-2017 11:00
    ​Geoff,
    There is a point missing from this discussion. Unless I missed a post, there is no mention about mic placement given the acoustic surroundings. Close micing (sp?) is certainly required in a noisy condition, such as a nightclub. Under those conditions, as previously mention, multiple microphones placed near the piano is necessary to reduce ambient noise from the room. Recording studio micing of solo piano is best configured with multiple microphones at least three feet away from the piano. 
    Roger
    ​​

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    Roger Gable
    Gable Piano
    Everett WA
    425-252-5000
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  • 6.  RE: Soundboard and mic placement question

    Registered Piano Technician
    Posted 11-04-2017 11:41

    Geoff,

     

    Having done sound reinforcement and also worked in piano recording sessions, I can tell you that the soundboard patterns really aren't the point. Once you are a few inches away from the board the sound waves are mixing in the air and, while you can get spots where there are cancellations in the air (which I demonstrated in a simple way in a South Bay chapter meeting last month) but these come primarily from sound reflections interacting.  I feel that is mainly what causes dead spots when using a tuning device – a particular frequency is being cancelled by reflected sound, or the device is being overloaded by a different frequency that is being reinforced, masking the one you need.

     

    My computer mixes the sound from 2 microphones for the tuning software, and I have noticed a decided decrease in the amount of moving around I have to do during tunings compared to the old computer and iPaq devices. The Windows 10 hardware spec calls for 2 mics and software that does noise and echo cancellation to give better speech recognition and such, however I found that I have to turn off that processing for tuning – it screws up music recording, but works well for voice.  So all advanced features turned off, good old Cybertuner for Windows really 'hears' nicely.

     

    Sound reinforcement needs the mics fairly close, and I concur that the (rather expensive) Earthworks piano mic set that Thomas mentioned is great for this. But for a natural sounding recording, the mics need to be outside the piano to get a blend of sound. If the engineers are amenable to a little advice from the tuner (it's not always appreciated!) I usually suggest that they also get the sound from under the piano to mix with what comes out the top.  This has always given really great results!

     

    Don Mannino

     






  • 7.  RE: Soundboard and mic placement question

    Registered Piano Technician
    Posted 11-04-2017 12:12
    Don --

    Thanks for understanding my question. My background is audio. I was a recording engineer in studios for over to 25 years. I understand how distance and reflection, even the room itself can play a part in how a piano is miced. Your comments on how cancellations can occur in air, and can affect how our EDT can sometimes have trouble picking up the partials it needs to do its job are what I'm curious about. My thoughts were that by having a theoretical map of how the soundboard is reacting to the vibrations being induced into it might be helpful in finding those spots where that dead zone can be discovered and avoided. But, after reading your post I realize that once you get more than about a wavelength away from the soundboard everything starts combining and reflecting and those mapped patterns become pretty meaningless. I guess just moving the device around to find the usable spots is still the only way.  I'm sorry I missed your class. Wanna come do it for us?

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    Geoff Sykes, RPT
    Los Angeles CA
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  • 8.  RE: Soundboard and mic placement question

    Registered Piano Technician
    Posted 11-04-2017 12:24
    I learned from Jim Coleman Sr. that those cancellation nodes are not experienced by us because out ears are 6" apart. Move your etd 6" to get a clear signal.

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    Larry Messerly, RPT
    Bringing Harmony to Homes
    www.lacrossepianotuning.com
    ljmesserly@gmail.com
    928-899-7292
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  • 9.  RE: Soundboard and mic placement question

    Posted 11-07-2017 09:44
    There was a study a while back on modal analysis of soundboards done by Fazioli.
    Interesting pictures. But, brush up on your calculus to fully understand it.






    ------------------------------
    I have a piano in my Nuclear Fallout Shelter, and my competitors don't. How silly is that?

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 10.  RE: Soundboard and mic placement question

    Registered Piano Technician
    Posted 11-07-2017 10:49
    This was exactly what I was wanting to see. I didn't mean that anyone should actually take on this experiment. It had to have already been done by some manufacturer. This is it. I think I may know of one more source, which I'll investigate and post when I find it. Do you have any idea what the colors represent? They're not defined that I can see.

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    Geoff Sykes, RPT
    Los Angeles CA
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  • 11.  RE: Soundboard and mic placement question

    Registered Piano Technician
    Posted 11-07-2017 12:14
    All-
    Another great resource is-
    The Physics of Musical Instruments
    Amazon remove preview
    The Physics of Musical Instruments
    While the history of musical instruments is nearly as old as civilisation itself, the science of acoustics is quite recent. By understanding the physical basis of how instruments are used to make music, one hopes ultimately to be able to give physical criteria to distinguish a fine instrument fro...
    View this on Amazon >


    I had the privilege of attending a seminar by Tom Rossing on pianos.

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    David Brown
    Dallas TX
    214-288-9413
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