Re: Yamaha Processor (was - Ferstler Shows Up Briefly)

Arny Krueger wrote:

> Anybody who tests equipment with a true random noise signal
> is sort of condemning themselves to an old-fashioned,
> out-dated kind of test. But it can be better than nothing,
> by far.

It has its uses, and is but one of several tests that can be
used to evaluate gear, particularly speakers. (It also comes
in handy when evaluating surround processors, needless to
say.)

One thing it can do is allow for comparison testing by ear,
again with speakers. That is, one can set up a pair of
speakers close together, feed them mono pink noise, and then
use the balance control to AB them. Doing this by ear will
quickly do three things:

1. It will show that even very good speakers, displaced
slightly in space, will have spectral balance differences at
the listening position that may be surprising. Indeed, even
the most subtle differences between speaker performance
(between supposedly identical speakers) will be easily
audible with a pink noise test signal. Switch to musical
source material and they may sound identical, but pink noise
will highlight those subtle differences emphatically. Hence,
pink noise is the equivalent of a good test pattern with
video.

2. If one of two speakers is defective (problematic or
inoperable driver) doing a pink-noise AB comparison will
highlight the problem immediately. It is a good test tool
for someone who does not have test gear and who wants to
know quickly if one of their speakers has a problem.

3. If power response is what matters most to an individual a
pink noise source, along with a good RTA, will do a fine job
of evaluating that aspect of speaker performance, at least
if the testing/listening room is decent and one has an RTA
with a continuous averaging feature. That allows one to move
the microphone slowly to get an average over a given amount
of space.

Yes, I know these days the emphasis (even with supposedly
knowledgeable enthusiasts and reviewers) is on the
direct-field, first-arrival signal getting to the listener.
(Thereby locking them into a sweet-spot listening position
for satisfactory performance.) There is a certain irony
here, because decades ago reviewers already felt this way,
and then along came guys like Villchur and Allison, and a
few others, and the concept of power response gained a lot
of support. This is perhaps why the old Acoustic Research
outfit managed to do so well for over a decade.

Unfortunately, most systems have problems delivering the
power-response goods, so many manufacturers went back to the
direct-field philosophy in order to rationalize the
limitations of their speakers. Today, many reviewers have
embraced the old view of the importance of the
first-arrival, direct-field signal, even though one does not
need to think much about it to realize that power response
eclipses the impact of the direct field in normal rooms even
with fairly conventional speakers.

I continue to believe that it is the total power response
that will matter most when it comes to the ability of a
speaker to simulate live music with good, "purist"
recordings. To get really good power response and spectral
balance at the listening position in most home-listening
rooms one needs a speaker with the widest broadband
radiation pattern possible.

Actually, my last sentence introduces us to another very
important aspect of loudspeaker performance. Mark Davis
showed a couple of decades back that the wide-angle,
full-bandwidth radiation pattern of a system is also
critical, and together those two (radiation pattern and
power response) are way, way, way more important than the
first-arrival, direct-field signal dealt with by various
gating measuring devices.

And pink noise, working with a good RTA, is a good way to
evaluate the power response. And one can also do a good job
of measuring the radiation pattern with an RTA and pink
noise, provided the job is done anechoically. Outdoors does
just fine.

So pink noise has its uses, and those uses are important.

Howard Ferstler
.

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