Are there disadvantages to installing condenser mics to the inside of the accordion?

[Alan Polivka]

The original question was "Are there disadvantages to installing condenser mics to the inside of the accordion?"

If you have electret condenser microphones under the grill, there is an unexpected problem that I discovered, but you will probably not experience this unless you have a very compact accordion with little spacing between the pallets and the grill. Any microphone has a maximum sound level before it will distort. Typically, this is around 120 dB SPL (sound pressure level), but it might be somewhat higher or lower. Now 120 db is deafening, at the human pain limit. So no worries, your accordion is not that loud, right? You might be wrong about this, from the microphone's point of view. If it was possible to place your ear right next to and in between the pallets while playing, it could sound very loud indeed. Since SPL decreases with the cube of the distance, pull your ear away only a few inches, and the sound level becomes more comfortable. But right at the pallets, where the sound comes out, it could be very loud.

I had a Limex microphone system installed in my compact CBA once, but there was so little space behind the grill that the installer arranged the 10 electret condenser capsules (which were on short wire stubs) so they were nestled between the pallets, almost touching the faceplate. For a few years, I presumed my amp was not very good, because it never sounded good to me. Then I was researching microphones once and read a comment that electret microphones were notorious for distorting at high SPLs. So, I soon determined that was the problem. If I removed the grill, and using foam blocks and tape, positioned it and the microphones out an inch or so away, then it sounded just fine through the amp.

Most of you can ignore this story, unless you have a very compact accordion, as most instruments will have adequate space behind the grill for the microphones.

I no longer use the Limex microphones. I replaced them with my own design using tiny solid-state MEMS microphones (the type found in cell phones). There are some available that are high-fidelity with low noise and the ability to handle high SPLs. They are small enough that they can be adequately spaced away from the pallets in a compact accordion. I think they sound good, with no distortion.

Electret condenser mics are available with different maximum SPL tolerances. Definitely choose ones that tolerate high SPL for use in an accordion. You can also wrap them in foam or cloth to attenuate the SPL they encounter, in order to avoid overloading them.

 

[JerryPH]

One issue with putting electret condenser mics inside an accordion (inside the bellows) is that most (but not all) electret condenser mics are pressure-sensitive. This results in a shift in in DC bias on the output when bellows direction is changed. Some amplifiers can tolerate that but many cannot. Reducing the decoupling capacitance reduces the duration of the transient bias shift, but also reduces the depth of bass passed on to the amplifier. Another solution is to find an electret condenser mic that is not pressure sensitive. Some Sennheisers are not.

I've once quickly looked at this. The few manufacturers that talk about pressures (near none do), discuss pressures wjere shifts can begin to affect the DC output in the 150kpa range and higher. A quick google places 150kpa at 21psi... I don't know about other accordions, but the chances of me compressing the internal accordion to that level is slim to none, so for me, thats not something that I would be concerned about. I *imagine* that the internal pressures never exceed 2-3 PSI or even less at normal playing levels and possibly 10psi or or less at full volumes of most acoustic acordions. During soft passages, I bet that falls well under 2 PSI.

For the accordion, I think that this is a moot point, but definitely a factor where the pressures are higher.

 

[Walker]

I don't know, but I think I would simply rather have nice external mics that are chosen to enhance the natural tones that are emitted and 'matured' outside the accordion. Also you can't 'step back' from the internal mics like you can with an external mic, so you are loosing some control of the nuances in the performance situation and the musical interactions with your fellow musicians. Sure you can play quieter, but have you noticed how many singers using mics often vary the distance of the mic from their mouth to give different effects...

Just my 2 cents.​

 

[JerryPH]

There is a plus and a minus to everything.

External mics introduce more room ambience/noise, are more difficult to control and for some people, can interfere with the visuals while making of a video. Of course, it is impossible to stroll and be heard amplified without internal mics.

Me, I am definitely OK with either, but my experience with internal mics was limited until I got the Beltuna and I am very surprised at the quality of the results that I got. Less worries about outside sounds or room acoustics, less to setup and so forth.

 

[Ventura]

to achieve vocalist proximity effect with an accordion, you would
need to mount something like a huge Victrola horn as an extension
of the microphone to capture then focus a wide area
of your accordion sound funnelled at the single point sweetspot
of the Microphone

the Vocalist can easily do that with lips, changes in intensity and
timbre, and small off-axis misdirection (like when whistling) but
a large accordion cannot really be "aimed"

close mic placement either in or on the accordion allow for,
provided you have really sensitive, high quality reeds, great
capture of relative dynamic bellows attack, and therefore
great variation of timbre as well

it is true the Sennheiser's are very resistant to pressure distortion.. if you
look at one physically you will immediately notice the difference in physical
design, with a protected diaphram and limited access point that builds in
an off-angle baffle much l;ike a tiny version of a folded reflex speaker cabinet

on the other end of the spectrum, physically wide diaphrams as used in the
Shure Green Bullet are better able to capture the naturally wider Bass frequencies
which are dimesionally large waves to begin with, and which i prefer to mount
inside the left side bass chamber as has been discussed in past threads

the biggest negative of the internal bellows location, is simply that if you
EVER are on stage with other microphones picking up ANY portion
of your sound, there will be cancellation from the soundwaves being
in opposite polarity

for this reason, i consider internal bellows Mic placement design unacceptable

sidebar: for those of you who are new to the idea of cancellation, first think of
a simple sine-wave that goes 180 degrees above then 180 degrees below the
centerline of zero (the ground plane)

now realize this is why Speakers are mounted inside cabinets

visualize a bare naked speaker sitting on a table and wired to
an amp.. the soundwaves being emitted from the BACKSIDE of the
speaker cone are OPPOSITE waveforms to the ones coming out the front

and so you hear almost nothing.. volume is impossible.. easy to blow
a speaker that is poorly baffled because of this phenomena
(you keep turning it up to get it louder until it fries)

for most people. most diverse situations and uses, the internal
under the grill mount is the best overall choice, unless (like me)
you don't mind strapping a mic chamber OVER the grill, which is
better (sonically) for many reasons

while it is pleasant to imagine an accordion quartet sitting on a
classy well sprung stage in front of 1000 completely silent, waiting fans
sitting in theater upholstered seating with soft curtains and carpeted aisles,
the truth is you will be playing on mostly noisy stages competing with crowd
noise as well as stage noise and seldom will you be using Acoustic
Microphones of your personal choice mounted on high quality stands with
vibration isolating mounts

 

[kimric]

Having designed a accordion mic system awhile back we ran into a few issues.
Condenser mics are not really happy with the air pressure changes inside the instrument, this can cause distortion and eventual failure in some cases.
We did have problems with distortion at higher volumes in some cases and we had to select mics that could handle 127db ( the test instrument we used could if pushed peg the db meter at 127 2" from the grill) the mics would do a odd chatter on the higher octave end of the keyboard or some of the Tex-Mex players. I made a sort of dense felt boot to fit over the affected mic in this case.

The placement issue was what we really focused on since that was a problem with most mics. The board is the size of a matchbook and the mics are on flexible shielded wires that can be cut to length before being soldered to the board. I am able to slightly bend the key arms to ket the mic between them in extreme cases (vintage 20's instruments).

The issue I find is that not a lot of people solder these days so the harmonix system does well in this regard ,but I tend to still shorten and clean up wires on these after install.

 

[SteveBox]

It is near impossible for an accordion to get anywhere near those sound levels. Think pro car audio with a 2,000 watt audio system… that’s what I had in a previous car, could only hit 118db and that was LOUD. For comparison, an airplane jet engine at take-off from 6 feet away generates 140db

This was in response to my theory that the sound right next to a pallet could be as high as 120 db or more (painfully loud). As an experiment, I removed the grill on my smaller two-reed CBA, placed a sound pressure meter right on top of the pallets, then played a SINGLE note with high bellows pressure. I got a reading of 122.8 dbA. With more than one note, I got 124 dbA, Normal loud playing gave readings of about 110 dbA. My Limex mics, which I had a theory might be overloading, were placed even closer to the pallet faceplate than my meter could be. The photo shows the meter displaying the maximum reading that it recorded with a single note.

So, microphones right under the grill do have to operate in a very loud environment. The closer they are to the pallets, the louder the sound will be. It is advantageous that it is so loud, provided the microphones can handle it, because this means you can get more amplification from your PA speakers before you experience feedback.

(This is a cheap meter, not a pro instrument. The specs claim it is accurate within +/- 1.5 dbA.)

 

[Alan Polivka]

I've once quickly looked at this. The few manufacturers that talk about pressures (near none do), discuss pressures wjere shifts can begin to affect the DC output in the 150kpa range and higher. A quick google places 150kpa at 21psi... I don't know about other accordions, but the chances of me compressing the internal accordion to that level is slim to none, so for me, thats not something that I would be concerned about. I *imagine* that the internal pressures never exceed 2-3 PSI or even less at normal playing levels and possibly 10psi or or less at full volumes of most acoustic acordions. During soft passages, I bet that falls well under 2 PSI.

For the accordion, I think that this is a moot point, but definitely a factor where the pressures are higher.

I've installed a lot of electret condensor mics in accordions and I can assure you that the change in bellows pressure when changing directions of bellows can indeed cause significant bias shifts in many models of electret condensor mics (when they're installed inside the bellows). If you don't believe me, try it yourself and see with a few different models of electret condensor mics. This is not a problem when the mics are installed outside the bellows, only when installed inside, which is the subject of this thread.

 

[Alan Polivka]

I don't know, but I think I would simply rather have nice external mics that are chosen to enhance the natural tones that are emitted and 'matured' outside the accordion. Also you can't 'step back' from the internal mics like you can with an external mic, so you are loosing some control of the nuances in the performance situation and the musical interactions with your fellow musicians. Sure you can play quieter, but have you noticed how many singers using mics often vary the distance of the mic from their mouth to give different effects...

Just my 2 cents.​

Indeed many accordionists use an external mic for the reasons you mention. Joey Miskulin (the top accordionist in this country IMHO) has played into an external mic every time I've seen him perform live. Recording engineers who are experienced at recording accordions usually use this approach as well, not the accordion's built-in mics. While some (electret condensor) mics built into an accordion have gotten very good in the past few decades, they are used primarily for the convenience of not having to maintain the proper distance from an external mic throughout a performance. David Lange has a nice YouTube video about the mics he uses for recording accordion.

 

[Alan Polivka]

to achieve vocalist proximity effect with an accordion, you would
need to mount something like a huge Victrola horn as an extension
of the microphone to capture then focus a wide area
of your accordion sound funnelled at the single point sweetspot
of the Microphone

the Vocalist can easily do that with lips, changes in intensity and
timbre, and small off-axis misdirection (like when whistling) but
a large accordion cannot really be "aimed"

close mic placement either in or on the accordion allow for,
provided you have really sensitive, high quality reeds, great
capture of relative dynamic bellows attack, and therefore
great variation of timbre as well

it is true the Sennheiser's are very resistant to pressure distortion.. if you
look at one physically you will immediately notice the difference in physical
design, with a protected diaphram and limited access point that builds in
an off-angle baffle much l;ike a tiny version of a folded reflex speaker cabinet

on the other end of the spectrum, physically wide diaphrams as used in the
Shure Green Bullet are better able to capture the naturally wider Bass frequencies
which are dimesionally large waves to begin with, and which i prefer to mount
inside the left side bass chamber as has been discussed in past threads

the biggest negative of the internal bellows location, is simply that if you
EVER are on stage with other microphones picking up ANY portion
of your sound, there will be cancellation from the soundwaves being
in opposite polarity

for this reason, i consider internal bellows Mic placement design unacceptable

sidebar: for those of you who are new to the idea of cancellation, first think of
a simple sine-wave that goes 180 degrees above then 180 degrees below the
centerline of zero (the ground plane)

now realize this is why Speakers are mounted inside cabinets

visualize a bare naked speaker sitting on a table and wired to
an amp.. the soundwaves being emitted from the BACKSIDE of the
speaker cone are OPPOSITE waveforms to the ones coming out the front

and so you hear almost nothing.. volume is impossible.. easy to blow
a speaker that is poorly baffled because of this phenomena
(you keep turning it up to get it louder until it fries)

for most people. most diverse situations and uses, the internal
under the grill mount is the best overall choice, unless (like me)
you don't mind strapping a mic chamber OVER the grill, which is
better (sonically) for many reasons

while it is pleasant to imagine an accordion quartet sitting on a
classy well sprung stage in front of 1000 completely silent, waiting fans
sitting in theater upholstered seating with soft curtains and carpeted aisles,
the truth is you will be playing on mostly noisy stages competing with crowd
noise as well as stage noise and seldom will you be using Acoustic
Microphones of your personal choice mounted on high quality stands with
vibration isolating mounts

Keep in mind that total cancelation only occurs when two different amplified signal levels (e.g., from the internal bellows mic and from an external mic - whether under the grill or not) are the exact same amplitude and exactly 180 degrees out of phase. The greater the deviation from that exact phase and amplitude condition, the less cancelation occurs. In most practical performance scenarios, no appreciable cancelation occurs. If it were a significant problem, you'd have similar issues any time a band has more than one microphone on a stage.
Some accordions have the right-hand mics installed under the grill and the left-hand mic inside the bellows and results can be good. Some people prefer that method. That gives the deeper bass response of an internal mic at the same time as a more natural independently controllable sound on the right hand. Yes, the sounds outside the bellows are 180 degrees out of phase with those inside the bellows. But, if one of your key objectives is to obtain the deepest basses, you can use this approach and apply a small amount of high-pass filtering (EQ) to the right hand mics and significant low-pass filtering to the left-hand mics. That EQ will minimize the potential for cancelation.
I'm not saying this is the only way to get deep amplified bass - it's just one method that has been used on many accordions with good results. It was particularly popular back in the days of crystal mics that didn't have such good bass response.
Alternatively, you can have the bass mics outside of the bellows and just apply more bass-boosting EQ. That approach is probably more common these days since decent low-cost EQ is more readily available in gig scenarios and it provides more separation between the left-hand signal and the right-hand signal for more independent control of relative volume.
With all of that said, I do concur that some degree of phase cancelation is one of the drawbacks of mixing internal and external mics.

 

[JerryPH]

...the change in bellows pressure when changing directions of bellows can indeed cause significant bias shifts in many models of electret condensor mics (when they're installed inside the bellows). If you don't believe me, try it yourself and see with a few different models of electret condensor mics

Once I start playing around I'd like to test and see this for sure.
Does it manifest as choking, distortion or frequency shifts that are audible?

I know that Hohner (back in the 60's and 70's) placed dynamic capsules in their accordions (in the bellows area, as you saw by my pics above) but those never lasted very long. I was toying with the idea of placing a cheap... as in under a 1/2"... condensor mic in there and powering it via the mixer's 48-volt phantom power.

 

[Alan Polivka]

Once I start playing around I'd like to test and see this for sure.
Does it manifest as choking, distortion or frequency shifts that are audible?

I know that Hohner (back in the 60's and 70's) placed dynamic capsules in their accordions (in the bellows area, as you saw by my pics above) but those never lasted very long. I was toying with the idea of placing a cheap... as in under a 1/2"... condensor mic in there and powering it via the mixer's 48-volt phantom power.

The big problem is that the large DC shifts cause some amplifiers to do strange things because they're not designed to handle that. Different amplifier designs react differently. One amplifier I tested, for example, would just briefly go silent when I changed bellows direction, until the DC level (on the amplifier side of the decoupling capacitor) got back within the the amp's tolerance (you could say that the overall effect was like temporary choking). Another amplifier made really loud crackling sounds when I changed bellows direction. Yet another amplifier wasn't bothered at all by the transient shifts in DC level. If the bias gets too far away from nominal operating level (on the mic element side of the decoupling capacitor), the signal will be clipped on either positive or negative portions of each cycle, depending upon the bellows direction. It would not cause a frequency shift - I can tell you that not from what I saw, but because (being an electrical engineer) I understand enough about how these mics work to know that wouldn't happen.
Regarding dynamic capsules, there is a guy who will suspend one of them (with elastic) inside the bellows of a concertina and the sound is very good. I have one of his elements (probably a Shure) and want to try it on an accordion, but unfortunately, there is not enough room inside the bellows of a typical accordion for the type of element he uses.

 

[Dingo40]

Waaay back, I heard people say accordions are very tricky to amplify correctly . Now I'm getting some idea of what they may have meant!
Phew!

 

[Ffingers]

I realise that this topic was about installing mikes inside the instrument, but I have always been impressed by the sound engineering for Alexandr Hrustevich:

https://www.youtube.com/@Hrustevich

 

[JerryPH]

I realise that this topic was about installing mikes inside the instrument, but I have always been impressed by the sound engineering for Alexandr Hrustevich:

His sound is excellent, no doubt!

When I went to see Alexander Sevastian (www.youtube.com/watch?v=P5JE6s9FeGc), he actually had a 3 mic placement, ones very close to his accordion in the center (top/down) of his accordion and the mics were perhaps 6-12 inches away from the accordion. Sound was pure and amazing and the 3rd mic was just for speaking purposes and was on a boom arm and was pushed away when he started playing.

Honestly, debating on which system is best is pretty much a waste of breath because both internal and external mics can provide equally amazing results. The one advantage that I can think of is that mics installed on the accordion can permit the player more movement where as external mics placed on mic stands pretty much mean that this player is stationary and if they playing with other musicians in certain environments means they are susceptible to feedback.

Hrustevich, of course also doesn't just play with one setup, he likely has a very good sound engineer helping and uses what is needed to get the best sound possible, and that setup changes:

4-mics setup:


1-mic setup:


You are right... he always sounds good!

 

[McSqueeze]

Hey Terry, with pleasure. The only 2 things to watch for are to not place the mic on anything that can transmit a lot of vibrations in to the mic and to be super careful of air leaks. Because the mic is contained within the "bellows area" it captures the left and right hands easily enough even with large bellows like on my Morino VI N.

A picture is worth a thousand words... lol:

Factory original. This dead mic was replaced with a mic cabsule from another mic


Remove the factory mic. This rubber part came from Hohner. If possible I would suggest a little DIY and creating something similar:


This is the mic capsule from a mic I had laying around:


Once installed:


From the factory, there is a plug that is air-tight and that the factory connector/cable clamps on to:


You would need to drill in to the area that is accessible inside the case or drill from under the grill in to the inner case to pass the wire in and use a bit of good silicone to seal the hole on both sides and then drill a hole in the grill to which you could attach the plug to. Since you are talking MONO, a single 1/4" female mono plug is all that gets placed on the accordion.

To get it working on an amp this is all that you would need, however the output is low if you want to record from this, so an external pre-amp makes all the difference. There are a ton of options out there, but I use this and it works great!:





Hope that helps some!

Hi Jerry, I see you have the mike capsule attached to the extreme treble end of the reed blocks. Is that because of space limitations, and in that position does it pick up the full treble range from high to low? Cheers John.

 

[JerryPH]

Hey John,
The location was chosen by Hohner and the backup mic is in the same area but on the bass side. Both of those mics pickup evenly and clearly not just from the lowest to highest notes on the treble but on the bass side as well. Now there are likely 2 reasons it works as well as it does… first the bass side on this accordion is nicely matched volume-wise to the treble and the second reason is that the bellows on this accordion are huge and that makes all for one nice resonance chamber for the sound.

It’s only downside *for me* is the lack of a possibility for a stereo setup, which honestly while gigging in public is no big thing, but when making recordings at home, I cannot do a stereo recording unless I go to my mics mounted on microphone stands (And I have 3 options in that department, cheap, medium and expensive mics).

 

[Tor]

Interesting that the pressure change has such an effect, given the limits Jerry found. For a 16"x7" bellows, you're looking 112 square inches, or about ..27psi with 30lbs on the bellows. Total pressure change is probably less than 2/3psi.

 

[Alan Polivka]

Interesting that the pressure change has such an effect, given the limits Jerry found. For a 16"x7" bellows, you're looking 112 square inches, or about ..27psi with 30lbs on the bellows. Total pressure change is probably less than 2/3psi.

Most analog electret and MEMS microphones have sensitivity between 5 mV/Pa to 18 mV/Pa.

Jerry's estimate of 0.27 psi = 1,862 Pa

At 10 mV/Pa, for example, that 0.27 psi would create 18.62 V, if it weren't limited to something less than the supply voltage used to power the mic element.

Other types of mics are also sensitive to pressure ... that's how they detect sound. But electret condensor mics have lower frequency response than other commonly used microphones. So, the issue inside bellows can be resolved by limiting the low frequency response of the electret condensor mic with the appropriate choice of decoupling capacitor between it and the amplifier.

 

[Alan Polivka]

Most analog electret and MEMS microphones have sensitivity between 5 mV/Pa to 18 mV/Pa.

Jerry's estimate of 0.27 psi = 1,862 Pa

At 10 mV/Pa, for example, that 0.27 psi would create 18.62 V, if it weren't limited to something less than the supply voltage used to power the mic element.

Other types of mics are also sensitive to pressure ... that's how they detect sound. But electret condensor mics have lower frequency response than other commonly used microphones. So, the issue inside bellows can be resolved by limiting the low frequency response of the electret condensor mic with the appropriate choice of decoupling capacitor between it and the amplifier.

However, a far better solution (than trying to solve it with the decoupling capacity) is to simply choose an electret condensor mic element with low frequency cutoff in the range of about 30 Hz or higher. That will reduce the amount of bias shift at the mic element itself during a quick change in bellows pressure, lessening the chance of putting the mic into temporary limiting.