Re: [Harp-L] re:What Cover-Plates Don't Do

[Jonathan Ross <jross38@xxxxxxxxxxx>]

> I am NOT being snarky, but have you experimented with this regarding measurement?  There have been a couple of threads recently where theory has been applied to what can/can't happen with a harmonica, but I am unaware of even any anecdotal evidence describing this in the real world.

The best evidence has been the attempted tests on comb materials.  No other attempts at real testing have been made public.  I have not tested any of this beyond listening trials.  They are not capable of proving anything, except giving a hint.


> I readily admit to trying to measure some of these things but with limited expertise in using tools.  

Frequency analysis can be useful, but different readings can have multiple causes.  I am sure Vern would have more to say on this, but just because a difference is notes by a machine doesn't mean it would be noted in practice by listeners or players, for instance.


> The changes in volume were the most obvious, but the sound pictures were different too.  I used a stock A Crossover and rotated between stock MB, XO, and SP20 covers.  This was for my own amusement, so I didn't fret recording things or logging pictures of the frequency responses, etc.  There are SO many variables to consider that at its most basic interest, regardless of the how, I can personally conclude that open XO style covers are my favorite.  MB covers that are opened would work too.  

Lots of variables come into play.  Perhaps the most important one is the player.  I feel confident in saying that no matter how hard you try, if you know the covers are different you will play differently.  I would eliminate either the player entirely or blind test everything--where you can't tell which covers are being used.

> While I felt SP20 covers felt more comfortable and besolid, the sound I was hearing when playing was warmer and less present at both the same playing pressure and volumes.  


I have a brass combed MB which I love.  I often feel that it sounds different from a similar one with a composit comb.  But, when I listen closely to the two and try to ignore feel issues, the timbre is unchanged.  Granted we are discussing covers not combs, but the point is that my ears can be fooled into hearing what they want to, and I have to work hard to try and get around that. I would suggest that may be the case here.

However, if changes in timbre because of cover shape, material or the like can be tested and found to exist, that would be interesting.  However, the hard part then would be to figure out why, since there are at present no reasons in theory as to why that would be the case.  But I certainly encourage more testing--I would love an someone who actually works in acoustics to get involved.


JR Ross