At 4:52 PM +0000 2/20/09, Bruce wrote:
>Thanks for the file post Tom as I have been very interested in how
>the PMD661 works. I worked on the file a little to try to normalize
>the Tic Tocs and applied a rumble filter. With this done, the middle
>recording, the PMD661 is actually lower noise by 2-4dB. It seems the
>PMD661 has better low frequency response.
Hi Bruce--
As you infer, using normalization on the lowest frequencies or on the
clock ticks to match playback levels tends to assume that all of the
recorders' pres are "flat." The Hz response differences in Tom's
samples are pretty dramatic, though we usually detect differences
when the recording chains are used. I find it possible to match
levels for these purposes by ear. I play them on several monitor
systems and concentrate on matching overall "impact." I can hear
subtleties in sound elements that come and go across the edits
joining the test segments better than listening within the clips.
As for the greater low-end response of the 661, we've observed that
Hi-MD recorders have less low-end response (under 100Hz) compared to
many recorders. The LS-10 seems to also have lower response compared
to the 661. The ringing resonance around 250 Hz in the PMD661 and
LS-10's samples is curious in that its not in the Hi-MD sample. Tom
and I corresponded and it seems the he exercised excellent control
over background sounds and took the best snippets from long takes.
Its possible that the comparison would be a little easier to judge if
the clock was moved closer. The room is quite 'live." Term-wise, as
per the subject of this discussion, recorders have "input noise" and
mics have "self-noise."
>
>I have a suggestion for future tests. If we want to test a new unit's
>noise level, wouldn't it be best to terminate the input with a 150
>ohm resister with the gains normalized first with a reference signal
>at the input?
Collecting reliable input noise measurements is very useful for
seeing the "tiers" of mic pre performance that are available. Here's
an example:
Let's say I've done my homework and have determined that my planned
rig will have a pair of very low-noise mics for recording ambience in
quiet locations. With some guidance, I can tell by looking at
Raimunds' chart http://www.avisoft.com/recordertests.htm, that
there's a crop of recorders measured at -118 dBU and below that are
not going to be well-suited for my purpose. Now I'm down to a more
manageable list.
When it comes to the next tier "up" of lower-cost recorders (-120 dBu
to -126 dBu), its tempting to think I can rely on the numbers to
determine if the noise added by the recorder's pre will be acceptable
or not. We have experiences that suggest this is probably not the
case for my demanding gear requirements.
Within the last 12 months, I was one of the recordists who became
encouraged by Raimund's input noise measurement of the LS-10 at
-121dBu, only 3 dBu noisier than respected Hi-MD units. Some
recordists bought LS-10's and favorable verbal accounts began to
trickle in. Then some concerns began to creep in. Vicki Powys
eventually conducted some comparison tests with low noise mics and we
learned, as Tom's test confirms, that the input noise of the LS-10 is
quite warm and is considerably more audible than one would expect.
With more side-by-side comparison testing, we discovered an imbalance
in the stereo channels in Vicki's LS-10 (which might be in Tom's
recent sample as well?).
The number of relevant comparison tests on the newest recorders is
quite limited (most testers use noisy mcs and/or low pre gain). As a
result, we are forced to recommend the Fostex FR2-LE because its
still the only, known, lower-cost recorder with pres quiet enough for
mics with the lowest self-noise ratings. Beginners on a tighter
budget should be able to make a good first-investment. As they are
usually making several quality compromises we can only guess about
the expected performance of certain gear combinations without actual
performance comparisons to refer to. We've discovered both dogs and
diamonds in rough by not making assumptions.
>The recording can then be graphed by frequency and
>amplitude in a program like Adobe Audition. When a mic is added it
>seems we are testing the microphone noise level more than the unit.
>Any microphone should have much higher noise level than any descent
>input amplifier. The noise of a variable test environment and
>variable set-up sounds would greatly effect the test results from
>person to person, and over time. Maybe I am missing the point of
>these tic toc tests? I realize they have value and are helpful but I
>really want to know the noise performance of a unit in numbers and
>graphs, rather than listening to different effects of mic noise, when
>making a purchasing decision.
I don't think any of the recorders in Tom's test have pres that are
"clean" enough to be completely inaudible behind NT1-A's self-noise.
In this case, and many, one is judging which recorder's input noise
is more acceptable and eventually, "acceptable enough." Its great
when one can include a more universally praised standard like a 744T
in the same test, but one can also make this cross-comparison using
other tests like, http://tinyurl.com/2ejuob
A good way to make initial investments that we have often discussed
is to do the research, narrow it down to a best guess _system_ and
then buy the gear from dealer that will allow it to be returned if it
doesn't meet one's needs. Oryoki has made a list:
http://tinyurl.com/b6985l This way, one will get tangible results and
gain a much better sense of other options to pursue.
Tests and measurement charts will not help the person who has bought
a recorder before knowing which mics, powering, and stereo array will
be used. This practice used to be a tad more common it seems to me.
Perhaps our discussions about not accepting the vague claims of
salespeople and manufacturer literature is having some positive
effect. Rob D.
>
>Bruce Rutkoski
>www.natureguystudio.com
>
>--- In
><naturerecordists%40yahoogroups.com>
>"tk7859" <> wrote:
>>
>> Hi Rob and the Group
>>
>> I ran the tests this morning and have sent you direct some WAV
>files.
>> I did two sets of tests; the first with the pre-amp gain turned to
>> maximum and a second series with the gain at 80% For a quick
>> comparison I have put together a compilation of 10 second snippets
>> from the 100% gain recordings out of each of the three machines The
>> quietest (LS-10) is first and the loudest (MZ-NH1) last. Other than
>> being converted to mp3 the recordings are "as recorded"
>>
>> I don't think a lot can be deduced from this until the levels have
>> been equalised. However, the Marantz 661 seems to be good.
>>
>> The mp3 of the compilation is in the files section
>>
>> compLS66NH.mp3
>>
>> Cheers
>>
>> TomR
>>
>
>
>
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