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A driver unit is a part of a hornloudspeaker, which are often
used on sportfields etc.
The driver unit is mounted on the rear of the horn.
This horn is 63 cm in diameter.
The efficiency of a hornloudspeaker is much higher than other
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 wil say; you put in 1 Watt of power into the speaker, and measure at 1 meter distance the soundpressure 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 inputpower compared to a driver-unit of 112.5 dB/Watt/meter for producing the same soundpressure.
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 soundquality wil decrease, the horn has not much bass respons.
For a good bass respons the horn must have huge diameter and lenght.
With the driver unit mounted on the horn, a good loudspeaker reception is possible with crystal receivers.
Connected to my receiver set 3 the
livingroom 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 audiotransformer , which transforms a high input impedance to 16 Ohm.
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