Driver unit's
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Driver unit |
A driver unit is a part of a horn loudspeaker, which are often used on sport
fields etc.
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Horn loudspeaker. The driver unit is mounted on the rear of the horn. This horn is 63 cm in diameter. |
The efficiency of a horn loudspeaker is much higher than other loudspeakers.
The best driver unit I have here (brand: Adastra, model: 952.207) has a
efficiency of 112.5 dB/Watt/meter when it is mounted on a horn.
The unit dB/Watt/meter will say; you put in 1 Watt of power into the speaker,
and measure at 1 meter distance the sound pressure in dB.
Normal home loudspeakers have a efficiency of 80 to 95 dB/Watt/meter.
Larger speakers can reach 100 to 105 dB/Watt/meter
A difference of 10 dB is equal to 10 times in power.
20 dB is 100 times in power, 30 dB is 1000 times in power.
So, a speaker with a efficiency of 82.5 dB/Watt/meter needs 1000 times more
input power compared to a driver-unit of 112.5 dB/Watt/meter for producing the
same sound pressure.
For maximal sensitivity remove the driver-unit from the horn, and hold the
unit to your ear.
The sound quality of a driver unit is very good.
Mounted on a horn the sound quality will decrease, the horn has not much bass
respons.
For a good bass response the horn must have huge diameter and length.
With the driver unit mounted on the horn, a good loudspeaker reception is possible with crystal receivers.
Connected to my receiver set 3 the living room is
filled with background music from a local station. (120 kW station at 17km
distance).
Connected (via a audio transformer) to my receiver set 1 the sound can outdoor be heard over a distance of
more than 30 meter.
De impedance of a driver unit is often 16 Ohm, this is much to little for
connecting direct to a crystal receiver.
So we must use a audio transformer , which transforms a
high input impedance to 16 Ohm.