To avoid the possibility of amplitude distortion it is best to load an amplifier with a resistance of about the same value as what the amplifier is designed for.
So a resistance of roughly 8 ohms can be connected in series with the low impedance loop.
The resistance has a beneficial effect - it levels the frequency response. It allows more turns to be used in the loop without loss at the higher audio frequencies.
The loop thinks it is being fed from a constant current source with an internal resistance of 8 ohms. This is considerably higher than the impedance of the loop itself even when it has several turns. It is this constant current characteristic which maintains the frequency response.
The amplifier is also happy because it thinks it is driving an 8 ohm loudspeaker.
The smaller the room area to be covered, the greater the number of turns allowed. The number of turns can be increased until the loop impedance is several ohms at the higher audio frequencies, say 4 ohms at 6 kHz if the amplifier has been designed for an 8 ohm loudspeaker. But it is very non-critical.
The loop impedance is that of its inductance which can be calculated prior to installation. or measured afterwards.
Reasonable hi-fidelity can be expected.
But performance ultimately depends on the sensitivity of the pick-up receiver and on the level of noise, interference and 50-60 Hz mains hum and its harmonics.