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 Post subject: Some tips on recording your yidaki
PostPosted: 07.09.2012, 03:18 
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Joined: 04.07.2011, 00:04
Posts: 59
Location: West Virginia, USA
After a long and frustrating journey, I have finally solved my recording problems. And to help all of you, I will describe what I learned so that you can make better recordings of your playing.

NOTE: Be sure to wear some quality headphones while viewing the videos below in order to get the most out of the audio experience. Headphones eliminate all of the artifact associated with sound reflections within a room and therefore give you a much clearer sound.

THE PROBLEM

My first recordings sounded terrible. (No sarcastic remarks about my playing, please! :lol: ) Though the microphone was only 12 inches from the bell, the recording sounded like I was playing in some distant room. The bass was overpowering and you could hear only one note no matter what other notes I played. Details of the harmonics and subtle sounds were lost.

The problem was not my recording equipment. The problem was the recording environment. You can have a million-dollar microphone, but if your recording "studio" has poor acoustics then the microphone is worthless. And therein was my problem: very poor room acoustics.

If you learn anything from this post, let it be this:

If you are going to invest time and money in recording, then first and foremost invest in improving your room acoustics. Then even a cheap microphone will work well.

How do you improve your room's acoustics?

ROOM ACOUSTICS

This is a very complicated topic, but I will try to distill the answer into a couple of short paragraphs.

My problem was that sound waves were bouncing all over the room and then combining in ways that negatively affected sound quality. Some sound waves cancelled out each other, resulting in a loss of sound (nulls) in certain frequencies. Some waves added together to form very loud and overpowering sounds (peaks) at other frequencies. Some sound waves kept bouncing back and forth for so long that they muffled subsequent notes and everything seemed to blend together and sound like all the notes were being played at one pitch, particularly in the bass frequencies. (This latter problem is called “one note bass.”)

Also, using two or more microphones (as in a stereo pair) also complicates the recording process. Having more than one microphone can degrade sound quality because sound waves can arrive at each microphone slightly out of phase, causing interference wave patterns. The distant sound that I was getting, like I was in another room, is called “comb filtering” and is caused by using two microphones improperly.

Here is a youtube video that illustrates the negative effects of comb filtering (ignore all of the computer software tech talk and focus on the sounds):
http://www.youtube.com/watch?v=2QPAFJyVb7U

THE SOLUTION

So what is the solution? The solution is to stop sound waves from bouncing all over the room. It’s that simple.

How do you stop sound waves from bouncing all over the room? Unless you can remodel your room, the only other practical way is to place a few sound absorption panels at key reflection points in the room.

Where to place the panels? It’s like playing 3-dimensional billiards – if you can bounce a ball from your yidaki to the microphone via the walls, then those bounce point on the walls are where you should place the acoustic panels. (This is called “treating the first reflection points.”) Don’t forget about the first reflection points on the ceiling as well. You can also treat secondary (2- bounce) reflection points if you have the inclination and resources.

Since the yidaki plays at such low frequencies, you’ll also want some “bass traps” in the corners of the room. Bass traps are acoustic panels capable of absorbing very low frequencies that pass straight through typical acoustic absorption panels.

If you have hardwood floors, or other highly-reflective surfaces in your recording area, then you definitely should take measures to absorb sound reflections. Throw down some padded carpet and put up some acoustic panels.

Here is some great information from the company Real Traps that describes how to reduce room reflections:
http://www.realtraps.com/rfz.htm
http://www.realtraps.com/art_room-setup.htm

DIY ACOUSTIC PANELS

You can find instructions on how to make inexpensive "do it yourself" acoustic panels and bass traps if your search online, particularly in the home recording forums and on youtube. I made 4 bass traps and 4 acoustic panels for about US $100.

Here's the method that I used:
http://www.youtube.com/watch?v=EdFQ4LOpCMk

If you decide to use rock wool in your DIY acoustic panels, be sure to get the AFB (Acoustic/Fire Batts) and not the regular home insulation batts. Rockboard 80 mineral wool is dense enough for use in bass traps. I doubled it and made 4-inch thick bass traps. Take a look at the sound absorption coefficeints of the different absorption materials before you make a decision as to which you will use in your panels.

For instance, 2-inch thick Rockboard 80 is 8 pounds per cubic foot, and its sound absorption coefficeints are as follows:
0.43 at 125 Hz
0.90 at 500 Hz
0.97 at 1,000 Hz
0.90 at 4,000 Hz

You should cover your acoustic panels with a loosely-woven fabric like burlap that is acoustically-transparent. You don't want to turn an absorption panel into a reflector by using a tightly-woven cloth. If you have a sound-pressure level (SPL) meter (Radio Shack $50) you can actually measure the sound absorption coefficients of your finished panels by measuring the decibels in front of, and behind, your panels at various frequencies (using mono-frequency audio test tones that are available online).

SPL Meter
http://www.radioshack.com/product/index.jsp?productId=12680845

Audio Test Tones (wear hearing protection when playing loudly!)
http://www.mediacollege.com/audio/tone/download/

DIFFUSERS

Besides absorption, you can also treat a room with sound diffusers, at a greatly increased cost. The following is a great informational video from the company Real Traps that should be viewed by anyone who wants to improve room acoustics:

http://www.youtube.com/watch?v=4nzmBhkR4JQ&noredirect=1

MICROPHONES

If you plan to use more than one microphone for recording, it would be best if you spent some time researching the different recording patterns of microphones and their placement to avoid problems like comb filtering. For instance, omni microphones are not really appropriate for close-proximity multi-mic recording. I use two cardioid microphones to reduce pick-up of scattered sound from behind, and arrange them in an XY configuration to reduce comb filtering effects.

FORMAL ACOUSTICAL ANALYSIS

If you really want to get into the details of recording, you should download an application like Room Equalizer Wizard (REW) to formally analyze your room’s acoustical response. I did, and here a spectral graph of my room before I installed the acoustic panels. Ideally, you would want to see a horizontal line (like the black line below, which is the soundcard calibration file), indicating a flat frequency response across the spectrum. But here you can see dozens of peaks and deep nulls that result from sound wave interference patterns and comb filtering that ruin my recordings. (The curve drops off at either end of the spectrum because of the hardware frequency limits of the recording microphone.) Note that most of these nulls are over 25dB deep, which is not insignificant!!

Image

THE END RESULT

Here is a photo of my home recording “studio” with some DIY acoustic panels and bass traps in place. Instead of treating the first reflection points, I just surrounded the recording area with acoustics panels in order to block sound reflections. There are actually 8 panels that I use for recording.

The resulting sound is clear and crisp, and I am hearing details on my recordings that I had never heard before. Similar acoustic treatment of your computer space will enable you to hear your recordings played back with the utmost clarity.

PROBLEM FIXED! :D

Now I just have to get over my shyness and post some recordings online.

Image

_________________
I toot in your general direction!
Harry


Last edited by harrym on 26.09.2012, 06:17, edited 1 time in total.

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 Post subject: Re: Some tips on recording your yidaki
PostPosted: 10.09.2012, 13:26 
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Joined: 17.03.2006, 21:22
Posts: 1002
Location: Zurich, Switzerland
Hi Harry

that looks very impressive indeed! And thanks for making the effort typing it down so that we all can profit from it. This is certainly helpful! All I need now are some quality headphones to watch the videos. Mine at home are REALLY bad!

Do you have a room analysis picture after the installation of the panels for comparison? That would be really interesting.

How are you getting along with those Dhalinybuy sticks?

Cheers
Christian


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 Post subject: Re: Some tips on recording your yidaki
PostPosted: 12.09.2012, 00:50 
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Joined: 04.07.2011, 00:04
Posts: 59
Location: West Virginia, USA
I've been trying to solve my recording issues, and traveling a lot. Now it's whitewater kayaking season, so later this autumn I'll get back into practicing regularly again.

Always keeping an eye on your inventory for any new and wonderful sticks! (:

Here are a couple of "before" and "after" spectral graphs.

BEFORE: Here is a "waterfall" plot of the bass frequencies (15 to 200 Hz), showing frequency versus amplitude versus time. You can see that the lower frequencies (< 50 Hz) are still "ringing" out past 300 msec. This means that the previous note is still echoing when the subsequent note starts, resulting in really muddy notes that all blend together.
Image


AFTER: Bass traps absorb the "ringing" sounds, which makes the bass frequencies sound more crisp. One note stops before the subsequent note starts. The notes are therefore more distinct. There is still a deep null at about 90 Hz that I can't seem to fix. I am not sure if this a transmission problem (of the test signal used to generate this spectral graph) or a true problem of wave interference. My subwoofer/main speaker handoff is right around 80 Hz, so this may be an artifact.
Image

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Harry


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 Post subject: Re: Some tips on recording your yidaki
PostPosted: 29.12.2012, 14:37 
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Joined: 04.07.2011, 00:04
Posts: 59
Location: West Virginia, USA
Recently I had a discussion with someone about recording, who stated that it was the microphone that was important, not the room's acoustics. He stated that he was worked in recording studios throughout his career, and he knew this for a fact.

But actually... The fact that he had worked in recording studios throughout his career was, in fact, proof that room acoustics were more important.

If the room acoustics were not important, then there wouldn't be recording studios. (:

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Harry


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 Post subject: Re: Some tips on recording your yidaki
PostPosted: 29.07.2014, 16:01 
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Joined: 20.06.2014, 15:18
Posts: 16
Im glad to read this. Afterplaying for a few months, I recorded myself on my flip video camera. I sounded terrible!! The recording sounded totally different to me than it sounds to my ears when Im playing, especially in a small room or against a wall.

I was about to just give up, I had thought I was sounding good, but the recording said I sounded horrible. So, 2 guys across the street work lift weights most days in the garage,,,, I got my didge , and went and played for them. I said to please be brutally honest,, does it sound like sh&*?? they said no it sounds cool, and they had heard me jamming on my porch and liked it.

On the recording it seemed to record vibrations but not notes,,, mayber this will help

thanks
Steve


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