On 18/08/2010, at 4:08 PM, Rob Danielson wrote:
>
> Hi Paul--
>
> I trust you are hearing something that's important. I want to hear it
> too. Can you describe the differences in pre performance in terms of
> specific, audio qualities? As you well know, comparative
> "preciseness" and "clarity" can stem from a number of traits. Tests
> can be tuned to foreground them.
Rob,
Sorry, I can't be more precise. I sold my HDP2 at the time I purchased th=
e SD722, and the impression of clarity and spaciousness was based on early =
impressions. It's about 4 months since I used the HDP2 and I don't trust m=
y auditory memory sufficiently to expand beyond those impressions. As Raimu=
nd said it could be placebo effect, but I definitely wasn't expecting the i=
mprovement I heard.
> Its my understanding that with a test like this one, mic self-noise
> _remains_ the predominant factor. The "transparent" pres allow the
> mics to shine through in nearly full glory. But, understandings
> evolve
The tik tests are predominantly about self-noise however I believe the meth=
odology is highly flawed even for this purpose.
The main concerns relate to non-repeatability of the "tik" test signal. Thi=
s should be apparent to anyone who has looked closely a sonogram of one of =
these tests. Due to the mechanical nature of the sound source and imperfect=
ion of the mechanism a sequence of tiks will have non-identical spectral co=
ntent. In Emil's comparison you can see the spectral content of the tiks va=
ries across each clip, and none of the clips have a tik sequence which is i=
dentical. This is problematic if you want to make comparisons of the tonal=
character or each preamp, as you have no fixed point of reference.
The non-repeatability has a flow on effect for level matching. There is no =
clear reference level, and matching by ear works to minimise any perceived=
difference between clips, regardless of actual difference. Again this is a=
pparent in Emil's test - when using the steady 200hz tone that was present =
in all 4 clips as a reference it was clear that the clips for Recorder A we=
re set roughly 1.2dB lower than those for Recorder B. Rectifying this cha=
nged the perception of which recorder had higher levels of self noise. When=
you are comparing two recorders that have a theoretical difference of 0.25=
dB in a-weighted microphone/preamp noise (based on the geometrical addition=
of a-weighted preamp EIN and microphone noise output for a 8dB/20mV/Pa mic=
attached to DR-680 and SD702) 1.2dB makes a real difference to how you ass=
ess the relative order of these preamps.
Something like a common reference tone played at the start of each test rec=
ording -- -40dB, 1khz sine or similar -- would at least allow accurate lev=
el matching between various setups with-in a specific set of tests and remo=
ve the arbitrary gain changes resulting from perceptual matching from the e=
quation. It's worth remembering that EIN is calculated from the measured l=
evel of the recorded noise plus the actual gain of the preamp, so to be re=
ally worthwhile these tik tests should account for actual difference in pre=
amp gain only. So no perceptual matching allowed! Sorry ;)
> I have no prejudice except that if a piece of equipment truly
> produces important differences, we should be able to readily hear
> them. There are many details to account for in a comparison test like
> Emil has made and I'm pretty confident that his test conditions
> present ample opportunity for several kinds of difference to surface.
Even in these test there are clear differences - comparing clip 2 and 4 the=
re a greater emphasis on sub-200hz in clip 4 for example.
cheers
Paul
> I often sense phenomena that seem palpable that I can't adequately
> describe. When I narrow my focus, my goal is to hear it, to dis-cover
> it, if I can. If I can't, I can't. The opportunity usually resurfaces
> if there is some _thing_ to it. Rob D.
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