Hello fellow audio enthusiasts. The purpose
of this test is to allow others to evaluate wireless transceiver lavalier
gear. If you would like to participate in the test, please send me the
following information with your sample audio file:
A. Name transceiver manufacturer and model
B Name microphone manufacturer and model
C. Describe the environment (distance, etc)
D. Describe recording setting (as 44.1Khz, 128Kbps)
E. Avoid sound processing if possible (EQ, compression, noise gating, etc)
Please keep the file short, 30 seconds of audio
is about right. You may wish to use the above text for your sample file. If
your sample illustrates a deficiency or shortcoming of the sample file,
please include an unbiased fair statement of the problem. These are
quickie "raw" tests - I wasn't concerned with plosives, silibants, wind noise,
etc. The primary focus was to baseline indoor tests and compare the
audio to a long-range outdoor "as-is" environment. I welcome you to
EMAIL me your sample audio files for inclusion here as well as
post
your comments and feedback on the dvxuser forum thread here
Test 0 (baseline):
A. Direct connect, without wireless tranmitter/receiver
B. Heil PR40 microphone
C. Close proximity, office studio (possible computer fan at 3 feet)
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP 3 file
Test 0.25 (baseline):
A. Direct connect, without wireless tranmitter/receiver
B. Octava MK012A microphone with hypercardoid head
C. Close proximity, office studio (possible computer fan at 3 feet)
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP 3 file
Test 0.5:
A. Sennheiser G2 wireless transmitter/receiver
B. Heil PR40 microphone
C. Close proximity, indoor, 518Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP3 file
Test 1:
A. Sennheiser G2 wireless transmitter/receiver
B. Sennheiser ME4 microphone
C. Close proximity, indoor, 518Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP3 file
Test 2:
A. Sennheiser G2 wireless transmitter/receiver
B. Sennheiser ME2 microphone
C. Close proximity, indoor, 518Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP3 file
Test 3:
A. Sennheiser G2 wireless transmitter/receiver
B. Countryman E6 microphone
C. Close proximity, indoor, 518Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP3 file
Test 4:
A. Sennheiser G2 wireless transmitter/receiver
B. Countryman E6 microphone
C. 150 yards transceiver spacing, outdoor/5-10 knot wind, 518Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP3 file
Test 5:
A. Sennheiser G2 wireless transmitter/receiver
B. Countryman E6 microphone
C. 300 yards transceiver spacing, outdoor/5-10 knot wind, 518Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing *** Test fails - too much
interference at this frequency/transceiver spacing
Test 6:
A. Sennheiser G2 wireless transmitter/receiver
B. Countryman E6 microphone
C. 300 yards transceiver spacing, outdoor/5-10 knot wind, 66Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP3 file
Test 7
A. Sennheiser G2 wireless transmitter/receiver
B. Countryman E6 microphone
C. 150 yards transceiver spacing, outdoor/5-10 knot wind, 66Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP3 file
Test 8:
A. Sennheiser G2 wireless transmitter, EW600 wired diversity receiver
B. Countryman E6 microphone
C. 300 yards transceiver spacing, outdoor/5-10 knot wind, 715Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP3 file
Test 9:
A. Sennheiser G2 wireless transmitter, EW600 wired diversity receiver
B. Countryman E6 microphone
C. 300 yards transceiver spacing, outdoor/5-10 knot wind, 510Mhz
D. 44.1Khz, 128Kbps, MP3
E. No audio processing MP3 file
Test 10:
Courtesy ScoobySounds
A: Micron Tram TR50 wireless transceiver
B: Microphones: Sennheiser MK416 (2 ea), Schoeps CCM41, Tram TR50,
Sony ECM77B, Rode NT2a, generic dynamic
C: Close proximity, indoor with computer fan @ 3 feet, open window near
street noise
D: 44.1Khz, 128Kbps, MP3 (MP3 re-recorded via Internet)
E. Unknown processing, apparently all mics connected via mixer
Michael Nistler on dvinfo.net, MoonLitNite on dvxuser.com
the MP3 sampling rate for your mic tests is too
low, and there is rather obvious MP3 compression
distortion present in EVERY mic sample.
I've been developing New Media projects for the past 15 years now, and am
quite skilled at sound and video compression. For MP3 audio compression
there is a simple formula to follow to determine the LOWEST sampling rate to
use.
Sound Frequency in Hz / 500 = Kbit data rate per channel
...So a mono recording made at 44.1 KHz, would require a data rate of 88
Kbits per second. A 44.1 KHz stereo recording like the mic samples you have
posted on your "Wireless Transceiver Lavalier Testing" web page would
require 176 Kbits per second to produce a pretty much distortion free MP3
file. Depending on the audio source, you can usually round these numbers
down to the next common data rate, so 88 Kbits could be rounded down to 80
Kbits, and 176 Kbits could be rounded down to 160. So I suggest
for any future samples, you specify that the user provide:
44.1 KHz mono audio, encoded at 80 ( or 96 ) Kbits per second
44.1 KHz stereo audio, encoded at 160 ( or 192 ) Kbits per second
I am planning on doing a mic test myself some time in March, and will send
you my results when they are complete. ( mainly a few Lavs, and a few pencil
condensor mics )
Guy McLoughlin, Toronto, Ontario
Hello Guy,
Thanks for the note. Yes, if the purpose of my testing was to focus on
compression aspects of wireless audio, I would agree with your assessment.
In fact, if we were doing A-B tests, I certainly wouldn't use 16 bit sound
using an MP3 format at all. However, as I mentioned, the purpose of the test
was primarily to compare transceiver frequencies and distances using various
gear - the recording rate (and even microphone) type was of secondary
importance. I'll enclose your thoughts the webpage along with this reply,
and I look forward to your contribution.
