I just don't get it !!

[zvigrunb]

I'm trying to wrap my head around the science of this...

I got a new Hering chrom (Yey!! ) that I had to open from the start.
Too many valves rattling and buzzing - Probably sat a long time on the store shelf.

Opened, I noticed all reed are pointing in the same direction.
What I'm used to see are blow reeds riveted towards the mouthpiece, draw reeds, reversed orientation, riveted towards the rear.
So each blow/draw pair have two reeds in opposite directions.

I thought this was a must - that air MUST flow over reed, from base to tip, in order for it to vibrate and sound.
That's why when you blow/draw the oppsoite reed will not sound - cause it can't move when against breath - only with it.
The same I thought for valves - the open with breath in the direction they're glued.
It just won't work the other way around.

Or so I thought...

Now this Hering, although blows are on the inside, draws on the outside,
but all with the bases up front, tips towards the back.
So...how in tarnation does the darn thing work??

When I blow a hole I expect to hear both reeds and on draw to hear nothing.
The fact that reeds are mounted on both plate sides - That's only a practical thing.
Or is that what actualy defines the function of the reed? Not it's mounted direction?

Can anyone explain the dynamics of how this works - I'm very interested

[John Broecker]

Hello, Svi.

We hope you are happy & healthy.

When we blow on a reed under the reed plate,
it goes through the reed slot, to make the sound.

When we draw on a reed above the reed plate,
it goes through the reed slot, to make the sound.

The position of the reed rivet or reed screw
(front or back of the comb) has no effect on
the sound (as far as I know).

There have been a few harmonica brands that
have made reed plates' slots in a left-to-right
reed placement, instead of front-to-back, or
all front or all back placements.

The reeds must go through the reed slots to
make sounds.

Above (draw) or below (blow) the reed plates
is the only requirement for reed sound production
on a harmonica.

The first mass-produced harmonicas (circa 1830)
had no covers, no comb, only reed plates and reeds.
But, the position above or below the reed plates
determined the sound produced, in combination with
exhale or inhale breaths.

I had a problem with a Hering Master Solo diatonic
harp, many years ago. It had bee delivered to my door
by the postman, who had it in his sack, in below freezing
temperatures.

The Master Solo has valves on the first 5 holes of the harp.
I had buzzing on those reeds. When I removed the covers,
I saw that all of holes 1-5  valved were curled upward, away
from the reed plates.

The cold temperature had curled the valves. I didn't know
what to do, so  I left the harp on a shelf, covers removed,
overnight.

By the morning, the room temperature had straightened
the valves, and the harp played beautifully.

Best Regards, Stay Healthy

John Broecker
Sussex, Wisconsin, USA

[zvigrunb]

The valves I saw were simply stiff and brittle.

Going back to original question -
Still, there is a symmetry that SHOUD cause both reeds to act together.
The breath flows over both in the same direction.
If I turn the harp upside down, we can relate to the blows as now being on top,
and draws "under" the plate - What i'm saying is, it seems the breath flows evenly over both plate sides,
so both reeds should work.

Still can't understand how one stays mute

[John Broecker]

We can't exhale and inhale on the reeds
at the same time.

When we activate the exhale reeds, we won't
get an inhale sound with the exhale reed.

When we activate the inhale reeds, we won't
get an exhale reed sound with the inhale reed.

Best Regards, Stay Healthy

JB

[kvanbael]

I'm trying to wrap my head around the science of this...

The fact that reeds are mounted on both plate sides - That's only a practical thing.
Or is that what actualy defines the function of the reed? Not it's mounted direction?

Great question. The physics of harmonicas is not so easy.
Blow reeds MUST be on the outside of the reed plate, where draw reeds MUST be on the inside of the reed plate. Their direction of mounting is less important (*).

Air is not like a projectile that can only travel in a straight path. Air is a flowing gas that can easily take any corner. It just wants to go from a higher pressure space to a lower pressure space. As you blow (draw) in hole, over-(under-)pressure will build up in the air chamber. Eventually the pressure from the inside (outside) will force the reed gap to open. (the reed on the other side of the plate will only close up more). As the gap opens, flow will increase, resolving the pressure difference. Due to a combination of reed elasticity and Bernoulli's law the reed will close again. As the reed travels back (overshooting its rest position, due to inertia), the reed moves into its reed-plate-slot and the air-flow is obstructed. This will allow the pressure difference to build up again and the whole cycle can repeats, hundreds of times per second. That is... if the system is allowed to resonate...

(*) Previous paragraph only explains how the vibration begins. To keep it vibrating, we need a self-enforcing static air wave inside the air-chamber matching the frequency of the reed. That is essential for the air pressure to fluctuate around the gap opening which feeds energy into the reed. (Without this fluctuation, the reed might just find an average gap to allow a steady airflow. I suspect the reeds are oriented with gap near the back of the air chamber to help such a wave to form inside the air chamber (Actually your mouth is part of that chamber, which is why the player has such an impact on the sound).

[zvigrunb]

Thanks John and kvanbael,
Greatly explained!

And I always thought it's the air direction over and in-line with the reed.
So much for conventional thinking

[zvigrunb]

The valves I saw were simply stiff and brittle.

Going back to original question -
Still, there is a symmetry that SHOUD cause both reeds to act together.
The breath flows over both in the same direction.
If I turn the harp upside down, we can relate to the blows as now being on top,
and draws "under" the plate - What i'm saying is, it seems the breath flows evenly over both plate sides,
so both reeds should work.

Still can't understand how one stays mute

Don't know why on earth I thought the plates are center mouth...
Being on both sides of the comb air must flow THROUGH the slots, not over them.

[Danny G]

Still can't understand how one stays mute

Keeping one reed silent is the function of the windsaver valve, it works like a check VALVE it only allows one way flow

[Grizzly]

Then why, if you remove the windsavers, don't you hear both reeds at once?

Tom

[Danny G]

I don't play half valved so this is just opinion but draw bending a note on a half valved chromatic would cause the blow reed to vibrate in the slot. Reed vibration creates sound so there must be overtones created similar to a diatonic.

[John Broecker]

Valved or un-valved, you will never hear both harmonica reeds
(blow and draw in the same chamber) at the same time.

The direction of the performer's breath is either exhale
or inhale. We can't breathe in and out at the same time
in a harmonica chamber.

This is an observation.

If an acoustical, scientific answer is needed, ask a physicist.

Best Regards, Stay Healthy.

JB

[Danny G]

Hole 1 on a C harmonica has a blow C reed and a draw D reed. The draw D is the higher pitched sound and the blow C is the lower pitched sound. When you play a bend on non-valved harmonica the lower pitched reed moves more than the higher one because the airflow across the higher reed slows and the lower reed vibrates in sympathy. So if you hear a C#/Db created by bending you hear both reeds

 

[Gnarly He Man]

Valved or un-valved, you will never hear both harmonica reeds
(blow and draw in the same chamber) at the same time.

On an unvalved harmonica, the blow and draw reeds both vibrate but you only hear the opposing reed when you change your embouchure to enable a bend.
And at a certain point, the opposing reed is louder than the sounding reed.

[TomN]

On an unvalved harmonica, the blow and draw reeds both vibrate but you only hear the opposing reed when you change your embouchure to enable a bend.
And at a certain point, the opposing reed is louder than the sounding reed.

Now I am confused - I thought that bending is more about changing the resonant chamber....
If opposing is reed is necessary then bending on a valved harp would be impossible

[Danny G]

Okay Gary, I thought you heard both because the first reed to vibrate prior to the bend vibrated before the overdrawn one.
I must have misunderstood, thanks for setting me straight.

Tom, you can bend a valved chrome but it's the single non-valved reed that bends

[Otter]

It's interesting, it seems like Hering copied a lot of things from the old wood-combed Hohner 16s (straight tuning, rivets towards the mouthpiece end, U-channel slide assembly, mouthpiece shape etc), and kept all of those details even on more modern styled instruments and on the 12 Holes.