(Thomas A) wrote:

(Nousaine) wrote in message
news:1KlWa.36390$uu5.4253@sccrnsc04...
(Thomas A) wrote:

....some snip.....

some more snip...

Where the "best scorers"
allowed to repeat the experiments in the main experiment?

This did not appear to be part of the protocol for any but subject analysis
was
common.

My experience with blindtests is that results do vary among subjects.
I made a test where the CD players where not level-matched (something
just below 0.5 dB difference). Two persons, including myself, could
verify a difference in blindtest in my home setup (bass-rich music, no
test signals used), whereas two other persons were unable to do it.
Thus a retest with the best-scorers in a test is something which might
be desirable.

In a situation like this with 2 of 4 persons scoring significantly it's likely
that the overall score would be significant as well.

It was typical for analysis to be conducted on a subject by subject basis to
find significant individual scores. In tests where the overall result was null
there did not appear to be cases where individually positive scores were
covered by totals.

I have offered Retests in most of my personally conducted experiments. In these
I have experienced exactly one subject who asked to extend the number of trials
in an experiment, one who retook a test at my request and one who accepted an
opportunity for retest.

This covers perhaps a dozen formal tests and several dozen subjects.

Many
questions but they may be relevant when making a meta-analysis.

In addition, have any of the experiments used test signals in the LF
range (around 15-20 Hz) and high-capable subwoofers (120 dB SPL @ 20
Hz)?

No. But there are no commercially available subwoofers that will do 120+ dB
at
2 meters in a real room. I've tested dozens and dozens and the only ones
with
this capability are custom.

Agree that commercial subs with +120 dB in room is hard to find.


I've just curious since the tests from the Swedish
Audio-Technical Society frequently identifies amplfiers than roll of
in the low end using blind tests.

The typical half power point for my stock of a dozen power amplifiers is 6
Hz.
I've not seen the SATS data though.

Have you ever tested yourself? You have a quite bass-capable system if
I remember correctly. You would need music with very deep and
high-quality bass, or test-tones, and perhaps a setup as described in
the link (a reference amp).

I've measured the frequency response of the amplifiers and, yes, my subwoofer
will produce 120 dB + SPL from 12 to 62 Hz with less than 10% distortion.

Perhaps not surprisingly it takes a 5000 watt capable amplifier to make these
SPL levels but I've never felt 'cheated of bass' when the system is driven with
2 channels of a 250 wpc stereo amplifier with ordinary programs, some of which
have frequency content below 10 Hz.

The reference amp used by SATS have during
many years has been NAD 208. Other amps rated good is e.g. Rotel
RB1090. I am not sure at the moment which ones that were rated
"not-so-good", but I can look it up. The method they use is a
"before-and-after" test.

http://www.sonicdesign.se/amptest.htm


It might not be said to be an
audible difference since the difference is percieved as a difference
in vibrations in the body. I think I mentioned this before.

Basically you have to have the woofer displacement/ amp power to start. I
haven't conducted a formal test about this but I'm guessing that speaker
displacement is a bigger issue than amplifier bandwidth. IOW I'm guessing that
most modern SS amplifiers have low frequency bandwidth to cover modern programs
and that the basic limiting factor is the subwoofer transducer(s).

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