Distorted sound bassoon tone chamber

[Pierre]

Hello,
I have an issue with my Scandalli SuperIV accordion. The sound of the bassoon in the tone chamber sounds some what distorted (a tad like a broken loudspeaker) at higher volume.
The reed blocks seems tightly fixed and wax and nail fixation looks good.
The outside of the tone chamber is in metal and sealed and glued so it us difficult to look if something is wrong inside.

Maybe this is a natural distortion or maybe the reeds are loose even if the wax looks good?

Any thoughts?
Thanks
Pierre

 

[debra]

Even though the wax looks good reed plates may still be a bit loose. The nail fixation prevents the reed plates from falling out, which makes it even harder to notice when reed plates are loose.
However, if the distortion happens just with some of the very lowest notes (white keys) in the L register it is possible that the reeds are hitting the bellows frame. And when the reed blocks are coming too close together the lowest notes (black keys) in the L register may be hitting the other reed block. I have seen both defects on other accordions. The first problem can be fixed by making a cutout in the bellows frame. The second problem cannot be fixed. Sadly both problems are design flaws that are quite common in accordions with cassotto.

 

[boxplayer4000]

Pierre,
Is the distortion more noticeable on the push or pull of the bellows, or the 'black' or 'white' notes? You may have to remove the reed blocks and sound it on tuning table to see/hear what the reeds are up to.

 

[Pierre]

Pierre,
Is the distortion more noticeable on the push or pull of the bellows, or the 'black' or 'white' notes? You may have to remove the reed blocks and sound it on tuning table to see/hear what the reeds are up to.

Even though the wax looks good reed plates may still be a bit loose. The nail fixation prevents the reed plates from falling out, which makes it even harder to notice when reed plates are loose.
However, if the distortion happens just with some of the very lowest notes (white keys) in the L register it is possible that the reeds are hitting the bellows frame. And when the reed blocks are coming too close together the lowest notes (black keys) in the L register may be hitting the other reed block. I have seen both defects on other accordions. The first problem can be fixed by making a cutout in the bellows frame. The second problem cannot be fixed. Sadly both problems are design flaws that are quite common in accordions with cassotto.

Even though the wax looks good reed plates may still be a bit loose. The nail fixation prevents the reed plates from falling out, which makes it even harder to notice when reed plates are loose.
However, if the distortion happens just with some of the very lowest notes (white keys) in the L register it is possible that the reeds are hitting the bellows frame. And when the reed blocks are coming too close together the lowest notes (black keys) in the L register may be hitting the other reed block. I have seen both defects on other accordions. The first problem can be fixed by making a cutout in the bellows frame. The second problem cannot be fixed. Sadly both problems are design flaws that are quite common in accordions with cassotto.

Hi Debra,
Thanks for your reply.
I intend to rewax the reed blocks but I’m still looking for good leathers like I had a few years ago from L Bompezzo. Unfortunately I can’t get in touch anymore nor had I an answer from Carini. I found adresses in France and Sweden but the quality was too bad…
Time to visit Castelfidardo me think!

This distortion problem seems to be more severe when I play chords in the lower medium and much less when playing solo notes.
Now I just noticed that some reeds could be better voiced, maybe to close to choking mode?
So now it seems to me that it could be the interaction between some notes that could amplifie the distorted sounds?

Now I also noticed that while knocking on the back of the cassotto (stainless steel plate) it seems to knock against some inner (wooden?) part. Could this possibly create bad sounds?

Thanks and greetings,
Pierre

 

[Pierre]

Pierre,
Is the distortion more noticeable on the push or pull of the bellows, or the 'black' or 'white' notes? You may have to remove the reed blocks and sound it on tuning table to see/hear what the reeds are up to.

Hi,
Thanks for your reply.
Indeed it seems a little less with the black notes.
(inside reed block) Maybe it fits a little better to the reed plate than the outer one but not sure.

There’s only a slight difference (a little better) when pushing the bellows.
As this problem is more noticeable when playing chords I don’t hear problems on my tuning bellow.
Greetings,
Pierre

 

[debra]

...
There’s only a slight difference (a little better) when pushing the bellows.
As this problem is more noticeable when playing chords I don’t hear problems on my tuning bellow.
Greetings,
Pierre

Aha! When the sound is better when pushing the bellows this is a stronger hint that it's a problem of loose reed plates.
When you push the air goes from inside to outside. The air pressure therefore pushes the reed plates against the reed blocks and then the distortion caused by loose reed plates disappears.
As for getting parts like wax and leathers I don't know whether Letizia (Bompezzo) is still in business but Carini definitely is. You can create an account on their website and order what you want. You then get a "pro-forma invoice" that you can pay and then they send what you ordered. I did this long before my first visit to Castelfidardo. When you do visit Castelfidardo they have one person at Carini who speaks a bit of English to help out the foreigners, but it is better if you can communicate in Italian.

 

[boxplayer4000]

Pierre,
It's quite difficult to identify any definite cause of your problem without actually seeing or hearing the instrument.

You say: "As this problem is more noticeable when playing chords I don’t hear problems on my tuning bellow."

When playing chords, especially on the larger, lower notes, a lot of air is used and the bellows air pressure is lower. When the pressure is lower the leather valves which should be "closed' by the air pressure may not be be closing properly. This then causes the reed opposite to not function correctly. Leather valves not functioning properly on the larger, lower notes is not uncommon and can be quite hard to deal with. I suspect on your quality instrument metal string assisters are already being used to address this problem. The problem is further complicated because with the reedblock on the the test-table bellows the air flow direction is reversed (ie. the outer reed is played by opening the test bellows, instead of the other way around when it is in place in the accordion). This is a situation where we can only probably rely on close observation to see that the valves close properly, stay closed and don't 'flutter'.

 

[Pierre]

Aha! When the sound is better when pushing the bellows this is a stronger hint that it's a problem of loose reed plates.
When you push the air goes from inside to outside. The air pressure therefore pushes the reed plates against the reed blocks and then the distortion caused by loose reed plates disappears.
As for getting parts like wax and leathers I don't know whether Letizia (Bompezzo) is still in business but Carini definitely is. You can create an account on their website and order what you want. You then get a "pro-forma invoice" that you can pay and then they send what you ordered. I did this long before my first visit to Castelfidardo. When you do visit Castelfidardo they have one person at Carini who speaks a bit of English to help out the foreigners, but it is better if you can communicate in Italian.

The strange thing is that the distortion occurs with some chords and when using the notes of those chords in other combinations the sound is not distorted.
Could this be a question of frequencies causing or amplifying vibrations of the (loose) reed plates?
(I think I’ll rewax a few of the offending notes to see if it solves the problem. (mostely situated in the 2nd octave.)

Thanks for the information about Carini.
Curious about the quality.

Pierre

 

[Pierre]

Pierre,
It's quite difficult to identify any definite cause of your problem without actually seeing or hearing the instrument.

You say: "As this problem is more noticeable when playing chords I don’t hear problems on my tuning bellow."

When playing chords, especially on the larger, lower notes, a lot of air is used and the bellows air pressure is lower. When the pressure is lower the leather valves which should be "closed' by the air pressure may not be be closing properly. This then causes the reed opposite to not function correctly. Leather valves not functioning properly on the larger, lower notes is not uncommon and can be quite hard to deal with. I suspect on your quality instrument metal string assisters are already being used to address this problem. The problem is further complicated because with the reedblock on the the test-table bellows the air flow direction is reversed (ie. the outer reed is played by opening the test bellows, instead of the other way around when it is in place in the accordion). This is a situation where we can only probably rely on close observation to see that the valves close properly, stay closed and don't 'flutter'.

Thanks for your reply.
The problem is mostely situated in the second octave (first one is ok)
According to Debra it could be some loose reed plates as leathers and springs are new and well seated. I even changed the leathers and voicing of the notes in the problematic octave several times.
I noticed the distorted sounds occurs in combination of notes.
I’ll rewax a few of the reed plates to see if it solves the problem.

 

[debra]

When you hear a "distortion" i some chords, but not in single notes, it may be a resonance somewhere in the accordion, possible also in the grille. A first suggestion to eliminate this as a problem is to remove the grille and play the chords again. If the distortion is gone then it was the grille that caused it. If the distortion is still there you have to look further. You can try to temporarily put tape on things that may vibrate: register sliders, register switches, and perhaps check inside for anything that may also vibrate.
The bad news is that the source of an unwanted vibration can be very hard to find...

 

[dak]

The bad news is that an unwanted vibration can be very hard to find...

Some permanently vibrating device like an electric razor can be touched to the instrument (possibly with something like an eraser to transfer vibrations without buzzing locally). Having a permanent buzz can make localization easier than something that only occurs during play.

 

[boxplayer4000]

dak: I like your vibrating source suggestion. In the days when analogue generated sounds predominated I went through a stage of making my own P.A. speaker systems. A variable frequency sound generator was used to 'sweep' the speaker cabinets to locate resonance peaks so that adjustments could be made to ventilation holes to eliminate (or minimise) the peaks; a process not unrelated to the possibilities of resonance in the accordion at the head of this thread.

 

[Perogie]

If you don't have an electric razor maybe you have a single neighbor lady nearby?

Sorry couldn't resist.