50 ohm speaker unique
fuzzzy,
Modern electronic device designs do not match the power output stage impedance to the load impedance. The output stage is treated as a voltage source with sufficient current capability to provide the required output power. Impedance matching per se is not the issue. If the efficiency of the new 22 Ohm speaker is the same as the old 50 Ohm speaker, then you need to supply a current of SQRT((50/22)) times the current required by the old 50 Ohm speaker to get the same maximum output. This means that the total resistance (including the speaker resistance) must be 50XSQRT((22/50)) = 50 X .6633 = 33.2 Ohms (an additional series resistance of 11.2 Ohms). Before proceding, you need to answer the following 2 questions:
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Will the output stage will be damaged by the lower resistance load?
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Is the output stage capable of supplying enough output current to give the same maximum output as with the 50 Ohm load without distortion due to current limiting?
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If the answer to the 1st question is "Yes", or if the answer to the 2nd question is "NO", then you have no choice but to add a 28 Ohm serieas resistance, resulting in 50 Ohms total, and be satisfied with a lower maximum power output.
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If the efiicency of the new speaker is not the same as the old speaker, then you will need to adjust the series resistor accordingly, to compensate for the different efficiency.
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Before purchasing the new speaker, I would try loading the output stage with a variable resistor load and determine the load resistance at which the output stage starts to current limit.
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If the device is battery operated, then using the 11.2 Ohm series resistor will result in a higher battery drain.
Regards,
Kral