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  • #11795
    David I Am
    Participant

    I think you are saying that your test could also be interpreted to imply this, but I’m not sure what “this” is.

    The hypothesis would be that the presence of the bladder itself decreases the ability of the sharp sounding of the reed, that wouldn’t be true with the hard chest.

    I include this as a measure of ‘I’m not ignoring a possibility’ but I really don’t think it is the case. If the lack of a bladder also avoided the symptom I don’t think they’d have put the bladder in there.

    This little youtube video demonstrates some of the effects of sequences of pressure on the suzuki B24.

    I think its telling how too much pressure (or too little) makes the sounding unreliable. I didn’t get it to happen in the video but not-sounding while starting to blow with the valve open is another thing that will happen.

    The bladder no doubt makes the playing easier – by enabling more air with less pressure – widening the range-of-what-works. Even with that said, its a good bit trickier to play than my other M-37 melodion.

    And uses a LOT of air.

    David

    #11793
    David I Am
    Participant

    I think the why its desirable is that without the bladder, the big bass reeds have trouble reliably sounding – if I open the valve THEN blow, its difficult to get the reed to sound with good attack. If I pressurize the chest THEN open the valve, the reed sounds reliably.

    I think that is indicative of one of two things.

    – a charged bladder is necessary for reliable sounding because of initial puff volume
    – a discharged bladder will stop reliable sounding because it lowers the speed of pressure rise

    But if we combine that with the other data point that I’ve heard (though not personally experimented with)

    – these bass melodicas don’t work well without bladders

    it would tend to cancel out the second option leaving only the first.

    Seem logical?

    #11789
    David I Am
    Participant

    Okay, here’s the sequence of events.

    1. the aperture is closed. There is a pressure differential between the air distribution chest and the reed, but no air is moving. There is a static air pressure across the chest.

    2. the aperture opens. No air has moved, but there is now a path for it to flow.

    3. A front forms as the air immediately adjacent starts moving into the opening rushing towards the lower pressure.

    4. the air next to the initial air moves to follow the previous air, advancing the front and diminishing it somewhat, expanding radially from the opening.

    5. the air next to the next air moves to follow the previous air, advancing the front and diminishing it somewhat, expanding radially from the opening.

    6. within milliseconds the front has moved across the entire chest, impacting first the diaphram, then the long walls, and finally the short walls and right up the mouthpiece to the source of the air pressure.

    At this point consider, you have a pressure gradient – on the outside of the reed is atmospheric – there’s a differential across the reed block – then a somewhat smooth gradient of increasing pressure that could be measured all the way from the reed block to the pressure source. This pressure gradient will exist so long as there is flow, based on the viscosity of the air.

    In a rigid chest, the large opening of the bass reed will allow a drop in the pressure – too much air rushing out too fast per the size of the chest, with the viscosity of the air involved the pressure will drop too low in the chest to continue to deliver enough impact air to the reed to make it start sounding. You’ll get a puff, a momentary pause, and then the fronts will have propagated up and dynamic flow conditions will set up the volume.

    In an elastic diaphram chest, when that front impacts the diaphram it allows the diaphram to tighten – to maintain the pressure in front of near at near that of the elastic tension of the diaphram provides – proving a a much shorter path – from across the shortest way of the chest – to provide fill air in the critical initial milliseconds of a valve opening, while the worst of the pressure gradient is in place.

    This may be somewhat unintuitive because of the high speeds involved – I just typed all these paragraphs literally describing what takes places in the time it takes me to strike a single letter. 🙂

    It may help to think of it like with water which is more obviously viscous – water buffer chests/tanks are used for exactly this purpose in applications where they need a surge-blast of water all at once – such as a commercial dishwashing machine. A pressure tank is colocated with the washing machine and connected with thick pipes to its outlet. the smaller inlet and outlet are both at the bottom – it may or may not have a diaphragm, but it will have pressurized air – a bubble at the top of the tank. When the valves snap open on the dishwasher, rather than depending on the pressure gradient driving all the way back to the main water heater, instead the water rushes down the pipe from the pressure tank. It can’t provide more than 20 or so gallons of water at any one surge – but it doesn’t need to. While the machine uses the surge of water it slurped in, the smaller inlet is busily recharging the tank – just like the mouth of the player is recharging the chest diaphragm of the melodica far slower than the rush of air when a valve opens.

    #11783
    David I Am
    Participant

    I don’t think you’re considering Viscosity Antonio! In the milliseconds of note valve open/attack, if the air has to move from further away than it would were it pushed by the bladder, it wouldn’t get there in time.

    I suspect this is a really dynamic effect – its not visually visible to human eye, you probably could get more of an idea what’s going on if you took high speed footage of how the part of the bladder closest to the opening momentarily dips as the note opens – supplying more air volume to the opening than the pressure front alone would permit…

    #11781
    David I Am
    Participant

    As I have one of these B24’s, I thought I’d weigh in.

    The thing I think the bladder does is a sort of capacitor for air – a capacitor or ‘tank’ in a circuit can be used to supply surges of current that otherwise would incur losses (proportional to its current) as it travels through wires and connections.

    So what the bladders does is like a capacitor increases the supply of charge to rush into an inductor, increases the supply of air immediately available to rush into the opening, sounding the reed.

    I have a tendency to stop blowing between notes on my alto/soprano melodicas as a form of expression while playing them – it alters the attack form in some way that my brain likes to play with. Or maybe its left over from trumpet playing. Anyway. When I play the B24 with that pressure dropping technique the bladder isn’t charged and the notes (especially the low ones) on the B24 won’t sound! Every time I pick the thing up I have to remind myself to maintain a steady pressure rather than relaxing it. And even then its a touch tricky.

    #10964
    David I Am
    Participant

    At the risk of being obvious… disassemble and find the part that isn’t seated/is leaking. You’re probably dealing with an old cracked seal – either on the wind chest or one or more of the valves.

    If no matter how hard you blow you don’t hear a whisper of a note, its probably the seal around the chest. I haven’t had that particular model in pieces yet, but my experience with other models indicates its likely a two-part plastic chest with a rubber gasket around the outside edge. Replacing this gasket would be my first attempt. Making sure that the plastic internals aren’t actually cracked while I’m in there. If they’re cracked, you could use some silicon caulk to seal it I suspect.

    If it still leaked, I’d have to see about the key valve seals.

    #10923
    David I Am
    Participant

    This is the clavietta topic

    Enjoy. Many good pictures.

    #10827
    David I Am
    Participant
    #10149
    David I Am
    Participant

    I think it might be worthwhile to consider in a fluid dynamics sense that the bladder is what provides the proximate gust of air that permits the attack it DOES have to actually happen.

    When that big valve/reed clearance opens, the air must rush through – if there’s no spring-loaded proximate air reservoir to dump, it would start swinging much more slowly.

    This is synchronous with how the attack is so gentle if you don’t build pressure before you hit the key. Effectively you could say that is the effect you get without the bladder under tension.

    A not dissimilar effect as the air tank on the trailer of a big rig, that provides a gust of air in close proximity to the brake actuators when needed, so that the truck can maintain control better. Or any pneumatic system with storage bladders/tanks close to the point of use, so that the working fluid can fill the gap without needing to chain-release all the way back to the main source with the accompanying velocity-related drag and pressure drop.

    #10097
    David I Am
    Participant

    regarding disassembling the melodion? No, its not glued. Its probably just a bit stuck together with pressure and rubber gasket and maybe a little spit, uh, ‘condensation’, shall we say.

    I haven’t taken my B24 apart, but I’m willing to to help you be more confident about how it goes together.

    Expect information in the next day or two.

    #10095
    David I Am
    Participant

    I guess you could adjust the curve/gap of the reeds to see if you can get a better attack pattern. I would be intensely interested in what you learn about the way the gap and curve affects the attack of the notes. Its a fairly rare player who even tunes his own melodicas much less adjust the gap and curve, hence the rarity of good information on it – but I’m one player who has tuned a good bit. The curve and gap adjustment is bound to be tricky for the low notes – the relationship between reed mass, gap, air velocity and column pressure. Proceed methodically, take pictures if you can, you have my attention at least.

    #10093
    David I Am
    Participant

    I think this is an effect of just the reeds being so massive and big so that they can make the deep sound they make.

    Think about pressure vs. pressing a note. On a normal pitch melodica, its not unusual to get a degree of expression to your notes by bringing the air pressure up when you wish to play a note. It is very natural to use the breath this way. This makes the attack of the note sound just a bit softer. There isn’t a particularly noticeable delay, but if you compare your technique when playing staccato, you’ll find you’re getting a sharper start on the sound by bring the pressure up first then releasing it with a sharp keypress.

    I too have noticed the lack of attack when playing the Melodion B24 – but find I can address it with steady pressure and sharp engagement of the key. The sudden air pressure burst when the key starts the reed vibrating quickly. Its literally a variation in your breath control against keying patterns.

    I think you’ll find that getting sharp attack on the low notes of an accordion is easier with faster actuation of the valves and firm pressure against the bellows – big reeds simply require more and sharper air pressure to sound quickly.

    David

    #9797
    David I Am
    Participant

    Right, relax, its okay. You can do this. Melodica is a simple instrument, and they aren’t difficult to disassemble.

    You’re going to likely need a small screwdriver and a medium screwdriver. technically ‘0.5’ ‘1’ and ‘2’ Phillips drivers will usually fit all the various screws.

    Get yourself a magnet to hold screws, it’ll come in handy. My favorite is a clump of those bucky balls magnet toys.

    First, remove the case screws. These may be at the end caps – such as the suzuki melodion – or they may be straight into the case in recessed holes as on many generics, the hohner, and the yamaha pianica.

    Once you separate the innards from the outards, you’ll find more screws to undo.

    Melodicas have a sound chamber in which there are several plates with reeds on them. You will need to open this compartment, revealing the reeds. Be gentle as you open this up, there will be a gasket around the edges (probably) to ensure there is no air leakage. You’ll be wanting to reuse this!

    Inside you will find more screws holding the plates down. STOP. I can’t imagine that there will be any need to remove the sound plates from the melodica. That said, they are fastened down with screws (usually quite tightly) and have some more gasketry going on underneath. be careful.

    Once its open, clean gently and mildly. You can run water over it, but don’t get excited with lots of soap or wiping – these tiny metal reeds vibrate to make your sound. If you bend them, they won’t work! Shake the most of the water off and let it dry thoroughly in your dishrack or sommat, then reverse your disassembly procedure to assemble it. Attach mouthpiece and VOILA! Pure sweet sounds of happiness!

    Keep tootin, you can do this thing!

    David

    #9774
    David I Am
    Participant

    I know what you are speaking of, I too have experienced this effect with various melodicas. (though I don’t remember specifically if my P37D has particularly exhibited this problem) – my suzuki melodion has for sure though.

    So you get this situation where the internals of the instrument are saturated with condensation and water/salivations are clogging up the close tolerance of the reeds.

    I have taken a few tacts to attenuate this problem.

    1. as I learned is super important with the bass melodion, don’t bother with tonguing, it messes with the attack of the notes anyway, probably because of pressure propagation against the size of the large reeds. I too come from horn playing and have tried to use breath control for some expression, but I think this is actually more of a trap.

    2. stick it in your mouth. Like, half an inch or so – so there’s a ‘pool’ of saliva that can form against your lips without running down inside the instrument. Sure, you’ll swallow between verses or something anyway – but anything you can do to keep it from getting excessively mucky down there will help significantly.

    3. whack it. Having inspected the internals and found condensation beading on everything, I noticed I could dislodge the moisture by increasing gravity – ‘slinging’ it off to to say. What this amounts to is whacking it end-downwards on my knee when I start noticing tone interference, as a centrifuge is not readily available. I bring it down on my thigh above my knee sharply while pushing my leg up (in a seated position). The idea is that this slings the fluids down towards the bottom of the melodica – which I can then attempt to clear with the spit valve. I also do this before putting it away. When particularly annoyed I wack it towards a side too. It seems to address the worst of the problem and the notes sound more clearly.

    Lastly, a proposal – what if we designed a mouthpiece with a spit collector – like a vacuum dust collection bin, effectively – only providing a place for excess salivations to collect rather than going down in the instrument? It would have its own valve on the bottom of it for lubricating the band room floor. 😉

    Keep tootin,

    David

    #9645
    David I Am
    Participant

    I had this exact thing happen and replaced it with an order from https://www.yamaha24x7.com/#/

    You have to create yourself an account but its free and then you can order parts. Here’s what my confirmation email looked like in part:

    Thank you for your recent purchase with us. Your Yamaha order is on it’s way.

    Your order details are:
    Order Summary :
    Order # 100284933
    Purchase Order # –
    Subtotal:
    $ 17.14
    Shipping and Handling:
    $ 7.95
    Tax:
    $ 1.29
    Grand Total:
    $ 26.38
    # PRODUCT DESCRIPTION LIST PRICE QUANTITY AMOUNT STATUS
    1 W4110210
    REED PLATE (HIGH) P-37D

    $17.14 1 $17.14 Shipped

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