If you send a 20hz sine wave to a driver a frequency response of 60hz - 3khz, where does the energy go?
20HZ will be fed into your frequency selective source the 'energy' will not be used as energy needs a load to disperse and there is no load.
Assuming you mean Power for energy.
Assuming you mean Power for energy.
The electrical energy is lost as unusable heat energy rather than being converted into usable sound energy.
As above was said.
But in the realworld, it depends on what the 60 Hz means in the spec and what are the other parameters of this driver and how it is used.
If this driver used in an adequate vented box tuned to 20 Hz, then even this low of frequency can be usable with it.
Or even in sealed box + EQ and/or room boost but the max SPL would be more limited than with the vented box.
But in the realworld, it depends on what the 60 Hz means in the spec and what are the other parameters of this driver and how it is used.
If this driver used in an adequate vented box tuned to 20 Hz, then even this low of frequency can be usable with it.
Or even in sealed box + EQ and/or room boost but the max SPL would be more limited than with the vented box.
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Please correct me if I’m wrong but most of the energy in dynamic drivers anyway (regardless of frequency etc) gets dissipated as heat. To answer specifically what I believe your question is, in the case of supplying much lower frequencies than as per the specs you will still get audio/sound… it’ll just be very quiet.
Because you need 4x the displacement for every half octave, 20hz (which is between half and a fourth of 60hz) will only play a fourth or an eighth as loud as it would at 20 hz. And with fletcher munson effects (humans hear lower frequencies softer (dbA) at the same db) it’s not going to be audible honestly, even though the driver will be moving.
In general there are two restrictions/caps - one is excursion/displacement, and the other is power handling and thermals. Small drivers don’t have much surface area, and you’ll likely run out of displacement much sooner than you’ll hit power handling if you’re feeding music (and not a pure sine wave).
(Ps as @YSDR mentioned you can get “more” bass from the overall system with good tunings, but your impedance rises/power input drops at tuning frequencies so you’re actually supplying less power… before the port gets unloaded and you then end up supplying more than before.)
Because you need 4x the displacement for every half octave, 20hz (which is between half and a fourth of 60hz) will only play a fourth or an eighth as loud as it would at 20 hz. And with fletcher munson effects (humans hear lower frequencies softer (dbA) at the same db) it’s not going to be audible honestly, even though the driver will be moving.
In general there are two restrictions/caps - one is excursion/displacement, and the other is power handling and thermals. Small drivers don’t have much surface area, and you’ll likely run out of displacement much sooner than you’ll hit power handling if you’re feeding music (and not a pure sine wave).
(Ps as @YSDR mentioned you can get “more” bass from the overall system with good tunings, but your impedance rises/power input drops at tuning frequencies so you’re actually supplying less power… before the port gets unloaded and you then end up supplying more than before.)
The impedance of the speaker is the load, so yes there is definitely something there to dissipate/adsorb energy.
Because the speaker's response (frequency response) has rolled off above 20Hz its efficiency for converting input electrical energy to acoustic output will be very low. So what will happen is that something like 99.9% of the electrical input energy will be dissipated as heat, with a very small amount being converted to acoustic energy (a pressure wave).
And the mechanical energy carried by the pressure wave will ultimately be converted into low temperature heat.
OP:
You might like to grab some driver data from Dayton Audio and plug them into XSim or VituixCAD. In XSim, examine the transfer function. and the frequency response for a 6 to 8" woofer.
You'll see that while the electrical power will remain flat-ish, the acoustic power is not. That difference is caused by a loss of efficiency, which is essentially what the frequency plot tells you. The efficiency (conversion from electrical to acoustic) is usually pretty low, only 2% or less maybe. It just drops even further as you go down in frequency which, so long as we aren't Xmax limited we can take to mean more heat.
Since the driver is already operating at such low efficiencies however, going from 98% loss to 99% loss may not make a big temperature difference.
You might like to grab some driver data from Dayton Audio and plug them into XSim or VituixCAD. In XSim, examine the transfer function. and the frequency response for a 6 to 8" woofer.
You'll see that while the electrical power will remain flat-ish, the acoustic power is not. That difference is caused by a loss of efficiency, which is essentially what the frequency plot tells you. The efficiency (conversion from electrical to acoustic) is usually pretty low, only 2% or less maybe. It just drops even further as you go down in frequency which, so long as we aren't Xmax limited we can take to mean more heat.
Since the driver is already operating at such low efficiencies however, going from 98% loss to 99% loss may not make a big temperature difference.
Not necessarily, as the impedance is partly reactive.
However to take your original question more literally, it will produce 20Hz.. it's just not going to do it at the same level as 60Hz as has been mentioned.