Topic: Microphones compared in terms of frequency response

[Nicola Fankhauser]

Hello fellow tapers

I have put my new Edirol R-09 to productive use and taped seven shows with it. I must say I am very pleased with its internal microphones. Since the beginning however it was clear to me that I would need to get external microphones to really get the best quality one could expect from audience recordings.

The last few weeks I also gathered samples from various microphone types and got very confused: There are a lot of different makes, and comparisons are nearly impossible because of different PA mixes, room characteristics, recording positions etc.

However today I think I can explain now also graphically why I personally don't like the sound of certain microphones. It's foremost about frequency response: If it's not linear, lacking in heights, you see repeating patterns etc., IMO also other things (that are less easy to measure, for me anyway) are not what they should be.

I put together some frequency-graphs of samples I gathered and published them here: http://variant.ch/phpwiki/WikiBlog/2007-08-07

Please, when comparing these diagrams, keep in mind that:

1. this is totally unscientific
2. the sources are lossless if not specified otherwise
3. the sources are from wildly different venues, recording positions, bands etc.
4. the mics compared range in price from $100 to $2000
5. this is not meant to bash any microphones.

if you'd like to see other mics compared, please send me some of the best, non-eq'd lossless sample you have (whole songs only please) and I'll include them.

have fun!
nicola

[guysonic]

I agree that looking at frequency plot is good introduction to what might be heard using a particular mic set.  However, in audio, specifications are just the tip of the iceberg in needed information to really know about what is going to be heard with a piece of gear.  Frequency also varies with angle from the source GREATLY with directional types, and the least with omni types, with true-pressure omni (a special type of omni) having the least frequency response variation with soundsource angle.  So just seeing on-axis mic frequency plot is showing only part of the response for most mic types.  And then there's PHASE over frequency that NOBODY talks about, but has much to do with characteristic mic coloration.

There are two issues with mics, frequency response+response off-axis, and how the mics are being arrayed.  Both these define the characteristic sound with some characteristics varying with venue stage width and PA speaker content and position of the mic from various sound sources.  Obviously, there's a lot of variables that define what to expect with mics so your quest for hard mic qualities from frequency graph is most difficult if not impossible to define.

Most all microphones over half inch diameter diaphragms and NON-true pressure omni type mics (directional) have physical mechanisms that get in the way of having truly flat 'uncolored' frequency response even if directly on-axis to the sound source. 

Fortunately, most recordists have come to like coloration depending on microphone model/type and how mics are being arrayed and type of recording purpose.

My personal tact in mics I make and use is to eliminate coloration (on and off axis) and use just one type of array with using small .25" true-pressure omini capsules arrayed on a special designed HRTF baffle, or a real persons head forward of the ears about 2 finger width distance from front edge of each ear.
The capsules (are special modified electret types) have ruler flat frequency (no coloration/smooth phase) from 5 cycles to >23,000 cycles with mostly smooth extended frequency bandwidth beyond 40,000 cycles like some Earthwork omni mics.

These specially manufactured tiny capsules used in true HRTF array has advantages so all recordings regardless of live physical circumstances of a venue/session will always record exactly what is heard live at the mic position in a 'virtual reality' stereo-surround imaging mode. Most mics/arrays will rarely record exactly what is heard, but mostly 'interpret' with coloration all live sound sources.  Again, most tapers have learned to love the colorations and interpretation of particular mics in certain array formations.

As you might suspect, listening to recordings made by a particular microphone used in a particular array is the only sure way to have chance of knowing what to expect.  AND it takes many, many recordings done with any particular mic/array in different circumstances to know anything at all as even a Radio Shack mic set can sound fabulous under special conditions, but not in many instances (for sure) so you have to have MANY recording examples. 

As you are finding out, it is difficult if not impossible to find sufficient number of recording examples of different microphones and array use for comparison, but this is what it takes to maybe know before purchasing a particular set of mics.  Unfortunately, most mic manufacturers have too few or no recording examples with notes on how the mic was arrayed and other details of the session for comparison purposes.
 
I tend to be different with many hundreds of examples posted with full notes on gear.  Further discussion of a particular HRTF array method I use and sample recording done over 22 years of using these mics at:
www.sonicstudios.com/multitrk.htm for simple 1-page discussion
www.sonicstudios.com/mp3.htm for ambient/sound designer sample recordings
www.sonicstudios.com/mp3_2slp.htm for recording session/live performance sample recording using these mics and array.