Accordion microphones. In serie or parallel or ........

Thread Starter

CeesJolmers

Joined Jan 16, 2018
2
Good Morning from The Netherlands.
I have a lot of very small electret microphones and I would like some of them to build them in my accordion.
Six on the treble- and four on the bass-site.
I wonder if I have soldering them in serie or parallel ( or maybe serie-parallel ).
I'm very interested in Your reactions.
Cees Jolmers, Leewuarden - The Netherlands
 

DickCappels

Joined Aug 21, 2008
6,091
You could connect a small number of them in parallel. There might be a point at which you have to decrease the load resistance to keep the JFETS in the electret microphones in their linear region, in which case the gains of the mircophones will be reduced.

Why so many microphones?

The gain dropoff (if too many microphones are connected) can be avoided by using active circuitry, like a summing amplifier, to mix the outputs.

Edit: Typo
 
Last edited:

Hymie

Joined Mar 30, 2018
741
Good Morning from The Netherlands.
I have a lot of very small electret microphones and I would like some of them to build them in my accordion.
Six on the treble- and four on the bass-site.
I wonder if I have soldering them in serie or parallel ( or maybe serie-parallel ).
I'm very interested in Your reactions.
Cees Jolmers, Leewuarden - The Netherlands
If you wire the microphones in series you will have no overall control of the response from each microphone – which makes up the sound from the accordion.

If each microphone is wired conventionally into a mixer, you will have ample control over the sound produced by the instrument – allowing you select the amount of bass, mid and treble produced.

I would think 3 or 4 microphones (correctly located) would give adequate tonal control of the amplified output. Bear in mind that electret microphones are very sensitive, which might lead to distortion if they are not operating within their linear range (i.e. the sound level is too high for the microphone to operate correctly).

I would recommend you experiment with 3 microphones located to pick up bass, mid and treble – with a simple circuit allowing you to control the output of each microphone pick-up.
 

Thread Starter

CeesJolmers

Joined Jan 16, 2018
2
Hello Dick,

Thanks for Your reaction!!!
Why so many microphones, You asked?
Well, I bought some years ago in a dump-store a huge lot of old cell-phone supplies with ear-phones and small, 6 mm.,
electret microphones, so I can experiment by de number on my breadboard.
The toneblock on the treble-side is 40 cm, so I thought I use 5 or 6 microphones for picking-up the high-, mid-
and low tones.
The bass tones on the left are quit low and loud, toneblock 30 cm, so I thought 3- or 4 must be enough mike's.
But the numbers on the right and left are pure my own "fantasy".
I think that I'm going for three microphones parallel on the right- and two on the left side.
The signal is goïng to a belt-pack, a small portable transmitter and my amplifier receives the transmitted accordion signal.
The last weeks I studied a lot of pre-amps ( for electret-/condensor mikes ) and I'm goïng to build two
pre-amps ( left and right ) with separated loudness- / tone control, as simple as possible, maybe a few
transistors or op-amps, but there is less information on the internet about serie or parallel, so I'm glad
with Your reaction.
So that's my accordion-project-story; at this moment in a pre-stadium, Dick.

Best regards from The Netherlands,
Cees Jolmers.
 

DickCappels

Joined Aug 21, 2008
6,091
The microphones are basically sound pressure level modulated current sources. Putting them in series would likely result in one dominating control of the current and the other just taking as much current as the other could get, as Hymie implied in post #3.

The microphones for which I have seen datasheets show a tolerance of ±2 db, which is probably fine for some uses. If you run into difficulty getting the right tone balance a little active circuitry should solve the problem.
 

MisterBill2

Joined Jan 23, 2018
4,856
The only application that I have seen for series connected microphone elements was for a noise-cancelling setup in a mobile radio microphone a while back. It did work, but the package was heavy by present microphone standards. And those were dynamic elements, not electret. Probablymultiple microphones in fairly close proximity, as you describe, will result in some interesting cancellation effects.
 

RonSpark

Joined Jul 29, 2018
2
Hello Cees , have the same idea. Tried a 3 set of adafruit max 4465 , integrated mic and amps in a row. Will not work up till now, to sensitive and very sceeqy sound.
The idea of three or four in a row on the melody side of a accordeon is ok. It is available in a pro version ( expensive about €400) Mt-06-m from musictech-midi.it. My next try will be a single mic amp ( conrad 197688) and three electret capsules.
How to connect.... series? Do you have an update on your experiments?
 

MisterBill2

Joined Jan 23, 2018
4,856
Not in series! use an audio rated op-amp as a summing amplifier, to combine the inputs from each microphone. OR, you can use a simple passive mixer, with a resistor in series with the output of each electret microphone. You might even get away with using that as the power supply as well, but it might not work out that way. At any rate, you will need to provide a voltage to power each electret element, don't ignore that. Inside an accordion the sound level is quite loud, quite probably overloading the microphones. What might be worth trying is several of those earphone elements used as microphones. I know that they do work as a transducer in both directions, current to sound and sound to current, and that they are made for higher sound levels. You could put three or four in series because they are low resistance devices.
 
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