Driving acoustic transducers with commercial audio power amplifiers

[m_t_c]

Hi all

I want to drive 16-channel low frequency acoustic transducer array using commercially available audio power amplifiers. The input impedance of single transducer varies from 500 Ohm to 700 Ohm at 8KHz. The two commercially available 16 channel models i searched are "D1650 Digital Multi-Channel Amplifier" from Russound and "PA 16 MK2 Multi channel Amplifier" from Storm Audio.

As these power amplifiers are designed for audio speakers which have very low input resistance (4 or 8 ohm usually), will these amplifiers be able to drive 500 ohm impedance acoustic transducers? If yes, what will be the possible limitations in terms of output power delivered to load? Kindly help me in this regard.

Thanks

 

[KlausST]

Hi,

Higher impedance means less current. Usually it's more difficult to drive high current.
Thus it should be relaxed.

But if you want to be sure you should consult the datasheet or the manufacturer.

Klaus

 

[FvM]

The answer depends on the required transducer power. Expect that the amplifiers have almost load independent output voltage, respectively you only get about 1/100 of rated power at the given transducer impedance. If that's not sufficient you either need audio transformers or a dedicated high voltage amplifier.

 

[m_t_c]

Expect that the amplifiers have almost load independent output voltage, respectively you only get about 1/100 of rated power at the given transducer impedance.

Hi
If we take example of D1650 PA, it has specifications of 50W across 8 Ohm load i.e. around 20 Vrms across 8 Ohm load. 1/100 of rated power means 0.5W across 500 Ohm load i.e. 15.8 Vrms across 500 Ohm impedance transducer. Am i correct in my calculations?

 

[Audioguru]

Please post a link to or the datasheet of your unusually high impedance audio transducers.

Hi
If we take example of D1650 PA, it has specifications of 50W across 8 Ohm load i.e. around 20 Vrms across 8 Ohm load. 1/100 of rated power means 0.5W across 500 Ohm load i.e. 15.8 Vrms across 500 Ohm impedance transducer. Am i correct in my calculations?

No. the 20V from the amplifier does not decrease, it stays at 20V. Then the power in a 500 ohm transducer will be 0.8W.
But the spec's do not say the distortion produced at full power. it might be clipping like crazy with a squarewave output of only 15V.

Usually the impedance of an audio speaker changes with frequency since an 8 ohm speaker might be 70 ohms at its low frequency resonance and its inductance causes its impedance to rise at high audio frequencies.