From: John Woodgate
Newsgroups: sci.electronics.design
Subject: Re: Loudspeaker and microcontroller
Date: Thu, 24 Oct 2002 19:11:31 +0100
Organization: JMWA Electronics Consultancy
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Reply-To: John Woodgate
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I read in sci.electronics.design that john jardine
wrote (in <871568ec.0210240918.63df3a68@pos
ting.google.com>) about 'Loudspeaker and microcontroller', on Thu, 24
Oct 2002:
> Which
>would give in turn a max of about 3/4watt and 1.5watts, which is still
>not a lot.
Yes it is. Remember that the 'loudness' of an audio signal roughly
correlates with its r.m.s. voltage, and audio programme signals have a
peak to r.m.s. ratio of 12 to 20 dB (4 to 10 times). But tone signals
don't! A typical (lowish) loudspeaker sensitivity is 85 dB SPL at 1
metre with 1 W input. Anywhere inside a normal room, the 1 m figure
applies everywhere, due to 'room reinforcement' - reflections and
reverberation. To be loud enough to hear clearly, a tone signal needs to
be only about 75 dB SPL, which is produced by that loudspeaker with only
100 mW input.
> The best way to up the power is to go for increasing the amp supply
>voltage to say 24V, use a standard 8ohm speaker and feed the audio
>amp from the PIC, via a volume control (max 8watts).
That would be very loud indeed, 94 dB SPL.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
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