Hypothetical Multi-Reed Chamber Interaction

[WoozleHarmonicas]

Before I go too far down this rabbit hole, I wanted to run a few hypotheticals past the group, just to see if my hypothesis is correct…
Someone here might be able to confirm my suspicious so I don’t have to go ahead and design and print a device that would allow me to test it.

Both of these hypotheticals are going to be based on a modified hole #4 on a C harmonica.

#1 - Sub30 style with a valve and an x-reed, but also an extra-extra useless reed…

• Blow: G3 with Zero Gap (chokes)
  Blow: C4 with normal gap.
  Draw: B3 with Zero Gap (chokes)
  Draw: D4 valved

(I would imagine that a typical Sub30 would have a Bb3 as the x-reed? I’m drafting this up from memory, so I’m not sure if that’s right or not. In this version, I’m stuck with a B3-draw, so I’m hoping that would still work…)

My assumption is that when you blow into this chamber, the C4-blow will sound, while the zero-gapped G3-blow will choke. As the D4 is valved, it is effectively nonexistent, allowing you to blow bend the C4-blow down towards a B with a little help of the zero-gapped B3-draw reed. An overblow is not possible, as the valved blow bend will happen instead.

When you draw on this chamber, the valved D4-draw reed should sound, and the zero-gapped B3-draw would remain choked. You could bend the D4-draw reed down to D with the help of the sympathetic C4-blow, while the zero gapped G3-blow won’t be activated at all. An overdraw is impossible, and the D4 is already the highest reed in the chamber.

In summary, it would behave something like a Sub30 style harmonica chamber (C4-blow, valved D4-draw, x-reed B-draw), and the additional G3-blow would do nothing. No overblow or overdraw.

If I’m wrong, I suspect the issue would be that the C4-blow bend would only be a half-step bend, halted from going any further by the zero-gapped B3-draw reed.

#2 - A “normal” Hole #4, with draw bend and overblow.

• Blow: C4 with normal gap.
  Blow: C4 with Zero Gap (chokes)
  Draw: D4 valved
  Draw: D4 with Zero Gap (chokes)

When you blow in this chamber, the C4-blow sounds, while the zero-gapped C4-blow chokes. The valved D4-draw is eliminated, and the zero-gapped D4-draw does nothing. If you attempt an over-blow, the zero-gapped D4-draw can activate in reverse to create a D#4.

When you draw on this chamber, the valved D4-draw reed sounds, while the zero-gapped D4 is choked. The D4-draw can be bent down to Db4 with the assistance of BOTH C4-blow reeds. An overdraw is impossible.

In summary, this chamber “should” work just about exactly like a standard 4th hole a C harmonica.

If I’m wrong, I suspect that the overblow might not occur if the D4-draw is zero-gapped, resulting in a blow-bend of the C4-blow reed instead. Or it might just not been at all because the zero-gapped C4 will further repel the bend. It’s also possible that on the draw, the extra zero-gapped C4-blow and D4-draw will activate sympathetically, resulting in a very airy draw note that is very difficult to bend.


If anyone is able to review my work here and let me know if my assumptions are correct, it may lead me to make some different choices before attempting the prototype I’m exploring.
Let me know where I’m wrong! I’m often wrong, so I won’t feel bad to hear it!

[Brendan]

Someone here might be able to confirm my suspicious so I don’t have to go ahead and design and print a device that would allow me to test it

I don't see why that's needed...? Why not just take the slide assembly off a chromatic, tune and gap the reeds to your desired setup/s, put your mouth over the exposed comb on the relevant place, then "suck it and see".

Since you customise harps (so presumably can retune reeds quickly), testing your ideas should only take 5-10 minutes. Doing experiments yourself is fun and the most instructive way to gain solid knowledge

(BTW AFAIK Idea #1 has a mismatch between the listed notes and the text below, so it's hard to assess).

[WoozleHarmonicas]

Thanks, Ill double check the text there.

You're right, I can probably test it on a standard chromatic rather than building something. I get way too excited about building things sometimes! Lol

[WoozleHarmonicas]

(BTW AFAIK Idea #1 has a mismatch between the listed notes and the text below, so it's hard to assess).

Yep. I had some extra flats in there. I was working from a sketch with a whole bunch of options, and was editing the idea as I was writing it out. (Oie) i corrected the original post.

I'm going to quickly modify a few holes on a chromatic, as you suggested, and test how the four reeds interact there. We'll see how it goes!

[dominico]

Hey Rob!

This is a very timely discussion, I am also working on my first x-reed project and was going to make a post with some similar questions.

Because you have 4 reeds in the chamber and you are planning on making a Sub-30 style harmonica, are you repurposing a chromatic? I had started a similar project on an EastTop T10-40, but now since getting my hands on a few Trochilus I switched over to building it on that platform, since getting rid of the slide will make that thing basically slightly larger than a diatonic. If you are using the same or similar platform maybe there are some opportunities to collaborate.

For Sub30 style interactions I'm thinking of sealing off that fourth reed completely, perhaps with an overplate.
Blow 4a: C <- valved to only allow blow airflow
Draw 4a: D <- valved to only allow draw airflow
Blow 4b: Sealed off completely so no airflow can pass
Draw 4b: A <- valved to only allow blow airflow

This allows blow to bend from C down to Bb, and draw bends as it normally does from D to Db.

That said, I also thought about keeping the 4th reed around and making it work more like an XB-40 style, where the draw bend could bend independently of whatever the active blow note is.
In this example you would have
Blow 4a: C <- valved to only allow blow airflow
Draw 4a: D <- valved to only allow draw airflow
Blow 4b: B <- valved to only allow draw airflow
Draw 4b: A <- valved to only allow blow airflow

This would allow blow to bend from C down to Bb, and allow draw to bend from D down to C.

I really like the idea of being able to control the depth of the draw and blow bends independently (even though it means I would have to retune a bunch more reeds)

though I'm wondering if I'm inviting a bunch of airflow / resonance problems to solve by having 4 interactive reeds in a chamber instead of just three.

I have some

[WoozleHarmonicas]

Hello Dominick!

Because you have 4 reeds in the chamber and you are planning on making a Sub-30 style harmonica, are you repurposing a chromatic? I had started a similar project on an EastTop T10-40, but now since getting my hands on a few Trochilus I switched over to building it on that platform, since getting rid of the slide will make that thing basically slightly larger than a diatonic. If you are using the same or similar platform maybe there are some opportunities to collaborate.

I actually was actually originally working on a fully 3D printed design that would encorporate three plates from diatonic harmonicas, in order to keep the form factor similar to a standard diatonic. However, the Trochilus platform intrigues me as well, and I realized that I can get a lot more experimentation done using that platform. If I settle upon reed configurations that achieve what I’m after, then I can look at “shrinking” it down.

I really like the idea of being able to control the depth of the draw and blow bends independently (even though it means I would have to retune a bunch more reeds)

I am trying to preserve the standard sympathetic bends and overflows in one reed configuration, while allowing the player to access Sub30 style sympathetic bends of the opposite reed as well. Hence the two configurations I was outlining in my original post.

As Brendan suggested, I’m going to mock up the two holes I’m imagining using a chromatic but without the mouthpiece, and see if this is going to achieve what I’m after. I’m skeptical that my initial assumptions are correct. It seems like there are a few areas where I should expect odd reed interactions, or degradation in performance.

[Brendan]

Dominick's note and valving suggestions are good.

Just to clarify, for valving of the x-reeds you'll need over-valves (valves on the same side as the reed, lifted off it by an over-valve plate).

The only way to avoid 4 valves per chamber is to have two valves set between the mouth and the reeds, as in Rick Epping's clever comb design for the XB-40.

A few years ago I designed a twin front-valve system for double diatonics, to play in a similar way to the XB-40. You can see/hear it in this demo, from about 9:00

X-Reed UniBender
https://youtu.be/xK_wXODAQ0Y?si=GPGTEiCYU2uem4KY

[WoozleHarmonicas]

The only way to avoid 4 valves per chamber is to have two valves set between the mouth and the reeds, as in Rick Epping's clever comb design for the XB-40.

Bingo! I knew there was something I was missing there, and I think this was it!

[Brendan]

Robert wrote:

I am trying to preserve the standard sympathetic bends and overflows in one reed configuration, while allowing the player to access Sub30 style sympathetic bends of the opposite reed as well. Hence the two configurations I was outlining in my original post.

Hah! It sounds as if you are aiming for exactly the same goal as I describe in this thread:

viewtopic.php?f=7&t=906

I thought it was only me who'd be interested in such an unusual harmonica, but it sounds as if you (and perhaps Dom too) are as well. Good luck! If you have anything like my experience, you'll find it's both fascinating and frustrating in equal measure.

So far I'm two years in on this project, and it's not over yet. Once I started on this quest, I discovered that there's an amazing number of different ways in which it can be fully or partially achieved. But in my experience, most of them have some flaw that's stopped me pursuing them further.

To date I've created about 25 wildly different, often crazy looking prototypes that all work to one extent or another. At some stage I plan on explaining them in a video series, but at present am still too much focussed on trying to attain that elusive goal of what would be to me "the perfect harmonica".

Have fun on the journey

[Brendan]

Adding to the valving discussion: I thinking I was being too adamant about the need for OverValves. If the x-reeds are set with zero or slightly negative gap they shouldn't sound in normal play.

But in my experience of making these types of harp, I generally find on certain bends I start to get interference from the x-reeds. For reliability and peace of mind that's led me to automatically install OverValves on this type of harp.

For your tests, try initially without them to check the playability. You can add them later if you decide they're needed.