Re: Comb Material [revisited]



Hi Vince;

You can hear a difference.  I can hear a difference.  And LOTS of other
folks can hear a difference.

The participants in the test done a couple years back could hear a
difference, too - but couldn't reliably ID which was which, and so this was
ruled out by some (but not by me).  BTW they used a resonant harp player,
which of course minimizes differences, as my own test (below) proves, and
for measurement, used only the ears of the audience.

The biggest difference in sound will be with players that are not as
resonant.  Beginners will hear a lot of difference between wood, plastic,
and such.  Advanced players minimize differences.  We can hear it in our own
ears, but it's doggone hard to tell on Memorex, especially thru a Bullet and
overdriven amp.

I've done oscilloscope measurements with a D Lee Oskar (plastic) and Eb
Blues Harp (because I don't have matching keys in the different materials).
I used a mic about 2 feet from the harps.  When played nonresonantly, the
waveforms of the two harmonicas were "night and day" different, and the
audible sound was quite different as well.  When played resonantly, there
was negligible difference in the observable waveform (almost pure sine wave)
and in the audible sound, which was roughly ~+20 dB louder than my
"nonresonant" sample according to my 'scope (Goldstar OS7020).  When played
resonantly AND with resonantly cupped hands, there was no discernable
difference in the waveform - it was a virtually perfect sine wave.  Resonant
hands added another ~+6 dB in volume.  I didn't test nonresonant embouchure
and resonant hands as a combination, as I just wanted to compare waveforms
and internal resonance (and I doubt I could actually do it - for me, they
come as a package).

Was this difference due to wood vs plastic?  To be perfectly honest, my test
only proved that an Eb blues harp produces a noticeably different waveform
than a D Lee Oskar under nonresonant conditions, and that these differences
vanish under resonant conditions.

To MY ear, the blues harp sounded more "woody" than the Lee Oskar, which had
a more "plasticky" sound, but that's just my opinion, based largely on 50
years' experience playing wood bodied harps, and about 25 playing plastic.
I would also say that in my opinion the difference in key (a semitone) had
little if anything to do with the difference in waveform.

If someone wants to set up a test using one common set of reed plates mated
to combs of different materials (Marine Band wood, some sort of plastic
comb, metal comb, and maybe something else just for laughs), I'd be happy to
run this again, using both resonant and beginning harp players.  Or better
yet, we could set up a test jig, with a vacuum cleaner and a straw directing
a column of air toward one particular hole in the harp - but NOT touching it
(if it touches, the resonance will probably choke the reed).

And rather than just having the audience rate the materials, why not use a
mic and oscilloscope to provide graphic evidence?  Or we could do both.

So I have a question - can we use the same Hohner reed plates (i.e. MS) on
combs of different compositions?  If so, we can easily set up a test that
measures *only* comb materials, and display the results on an oscilloscope.
I'm going to see if I can use my digital camera to capture the respective
waveforms, which we could upload to the net.

Maybe we can set this up for the LARHA?  What'cha think, guys?  We need one
set of reed plates, and several combs of different materials.  We may need
to sand, grind, or machine them to the same dimensions.  We also need a test
jig that will "play" just one note on our test harp, and allow for rapid
exchanges of reed plates (like maybe some spring clamps - which I have - I
use them when tuning my harps).  I'll provide a good mic and 'scope.

BTW I'm an electrical engineer.  When we test, we ALWAYS use a 'scope.  It
turns up things that ears don't.

http://www.billhouse.com/songs/YouAreSoBeautiful.mp3
- -IronMan Mike Curtis Band  http://www.ironmancurtis.com *Southland Blues
Magazine http://www.SouthlandBlues.com


From: <vince@xxxxxxxxxxxxxxxx>

> I would like to know what REAL research has been done on the difference in
> comb material (if any). I'm aware that this was tested somehow in the past
> but am very concerned. Most importantly, how was this testing done?
>
> I'm wondering cause I sat down in Memphis w/ friend and harp customizer
Tim
> Northcutt this weekend. After a few hours of him giving me lesson on first
> position we studied comb material. Tim had 4 harps there - a Special 20
> (plastic comb), Marine Band (pear wood comb), Special 20 (synthetic marble
> comb) and a Marine Band (machined acrylic comb). All harps were the same
> key. After playing the exact same single sound on each harp we learned
that
> they all still sounded much alike but the fullness in sound was different
w/
> each comb. To note that the order of the fullest sound from fullest to
> thinnest was just like this
>
> 1- Clear Acrylic Comb- Man this comb makes a difference (go ahead and
> disagree)
>
> 2- Wood Comb- Just a tinny bit fuller than the plastic, but thinner than
the
> acrylic comb
>
> 3- Plastic- very close to the synth marble, maybe a little thinner than
the
> MB - Note: This harp o course has SP 20 plates so that may be different
> itself)
>
> 4- Synth Marble- was really good and not far from the plastic
>
> I know I'm going to get a lot of people to disagree (cause of past
studies).
> I will admit I had a beer or two that night but I will honestly tell you
> "I'M NOT DEAF, I KNOW WHAT I HEAR". I noticed a difference in the sound
> coming from each harp when nothing was different other than the combs.
> Though I agree w/ Tim that the covers make a lot more difference than the
> comb but who is honestly saying that they can't hear a bit of difference?
> Was any of the past tests done by ear or digital?
>
>
> PS: If only the price of Clear Acrylic would go down, lol. These things
> ROCK!!!
>
>
> Vince Cheney
>
> The Blues Site - http://thebluessite.com
> Winemaker's World - http://winemakersworld.com





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