weslie, please answer a question: will such loudspeaker (as I've used) short-circuit if the movement of the diaphragm be hardly constrained, or the voice-coil glued to the magnet?
sound has nothing to do with it. It is the "frequency in the wire" - not sound pressure wave that counts.
Frequency delivered from the sound card should independently be delivered to the amplifier circuit build in the speaker without any chances for any feedback leakage.
Power supply: the transformer 220V to 12V AC should be connected to Graetz bridge rectifier using 4 diodes and than to pi filter made from minimum 2 capacitors (in old times electrolytic.)
But Chinese uses some tricks to make it cheaper.
So what happened:
At the particular frequency of the sound the load presented to the transformer or to the all three transformers powering 3 sets of amplifiers with 6 speakers from the same outlet
in its parameters presented value making the transformer going to SRF = Self Resonant Frequency
In the picture #1let's calculate some values using a SRF calculator:
if the inductive reactance was: 696 mH and capacitive reactance was 9.7uF than frequency of SRF= 61.1Hz
and in USA frequency of power grid is 60Hz.
calculatoratoz.com/en/self-resonance-frequency-calculator/Another example using equation:
A transformer primary is a coil, and the opposition induced in that coil can be calculated.
If the winding in the coil is 500′ of AWG #22 copper wire, the wire has a resistance of approximately
8 Ω. If the coil has an inductance of
0.5 H=500mH, the inductive reactance and total impedance are calculated as follows:
look at
picture #2For you to know and understand
How impedance affects wire that has 8 Ohm of pure resistance of copper : If the wire is not wound into a coil, the resistance of the wire alone is 8 Ω. Because a coil has a higher impedance than a wire, the total impedance when the wire is wound into a coil is 188.7 Ω at 60 Hz. The current capacity in the wire alone is about 23.6 times higher than the current capacity through the coil because of
the increased impedance from the inductive reactance of the coil.
The comparison of the coil and the straight conductor shows how a transformer primary can be connected to a source and act to limit the current.
The four factors that determine or control the inductance of a coil are :
the cross-section of the core,
the number of turns,
the type of the core,
and the length of the coil. So Aleks- try to connect 8 Ohm wire into 220V DC and it will blow or your 15A fuse will blow.
And now:try to make primary winding of the transformer from the same 8 Ohm wire that becomes 188 Ohm in form of a coil.
If that winding in this transformer at that frequency is not in the frequency of self resonance you can use this transformer.
However if you take the 3 of transformers under very specific load( at the particular frequency of the sound)
all of them have their primary winding connected in parallel - they may fall into self resonance as impedance is dynamically dependent .
-it means is frequency sensitive
one more factor that may be important :
In civilized Western World of Europe frequency of the grid is 50Hz.
if we have dynamically changing load on the transformer and in Russia this frequency drifts we may also get effect of selfresonance.
of the transformer.
-in picture #1 you see SRF=61.1Hz. So that is 1.1Hz more than in USA(60Hz) That little drift may cause problem here.
Russia during soviet union had constant every day frequency drift in all countries under soviet terror.
Russia of today is likely third world country with GDP likely lower than in Papula New Guinea
and Uganda or some other African countries.
Everything there is worse than it was during Soviet time and Putin is hunted by international court in Hague
like Muammar Muhammad Abu Minyar al-Gaddafi or Saddam Husein .
opinion expressed is my own.Wesley
