Re: [Harp-L] Chromatic cover lids modification
If many buyers think, as you do, that openings in back of a harmonica have a perceptible effect on loudness, the manufacturers will cater to those beliefs, whether or not they are true. Hohner has actually claimed that different types of wood used for combs produce perceptible differences in tone! Manufacturer's, in an effort to differentiate their harmonicas from those of the competitors, will often make claims that are not fully justified by acoustics. A common ploy is to exaggerate some minuscule effect.
Hearing is a very subjective sense. Listeners will report hearing what they expect to hear. It requires testing under very carefully controlled conditions to avoid these subjective effects. Knowing whether the opening in back is larger or smaller will affect what you think you hear.
Human hearing is logarithmic. Sound level is measured in decibels. An agreement is made on a reference level of sound pressure that is barely perceptible to the "average" person. Then the db level of a sound is ten times the logarithm of the ratio of the sound pressure to that reference. A human can barely detect a sound level change of 3 db where the level is suddenly changed....as in an A/B test of hi-fi speakers. Yet a 3 db increase is a doubling of the sound pressure! If you listen to a sound in a room, then go to lunch and come back to the room to hear the same sound at a different level, it takes a very much larger difference to be perceptible.
Any slight change in the opening will have only a small % change in the level and will be imperceptible to your ear.
However, it is your harmonica and your ears. If you do not find my arguments persuasive and you want to cut or bend open those covers and rejoice at the increase loudness, have at it.
On Jan 13, 2011, at 6:19 PM, Denny Noreikas wrote:
> That is interesting. I wonder why the new trend in diatonic harmonicas is a more
> open back? They do seem louder to me but are also more susceptible to denting.
> I'm confused.
> On Jan 13, 2011, at 7:03 PM, Vern wrote:
>> The curling in of the cover plates does not perceptibly suppress the sound. I once blocked off more than half of the opening in the back of a harp with an aluminum plate. There was no perceptible difference in the sound as measured on my sound-level meter. When you cup a harp in your hands, there is hardly any effect until your hands are almost closed.
>> Opening up the Velvet Voice covers would be a waste of your time.
>> On Jan 12, 2011, at 5:27 PM, Denny Noreikas wrote:
>>> All this recent talk about which Chromatics to buy got me thinking about trying the
>>> Chromatic again for playing Blues. I have 2 key of C's, a Hohner CX-12 and a Hering
>>> Velvet Voice 48. The CX-12 is too shrill for me compared to the Velvet Voice. I like the
>>> rich smooth sound of the Velvet Voice. However, the top and bottom cover plates on the
>>> Velvet Voice curled around toward the comb in the back of the harp which narrows the
>>> back opening suppressing the sound. I am sure this is by design.
>>> The CX-12 has a very large opening in the back. Can the cover plates on the Velvet
>>> Voice be filed down with a Dremel tool or similar device to open up the back? I am not
>>> a customizer nor do I want to screw-up a perfectly good harp.
>>> Any help would be appreciated.
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