From: John Woodgate
Subject: Re: Loudspeaker and microcontroller
Date: Thu, 24 Oct 2002 19:11:31 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Thu, 24 Oct 2002 20:32:30 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
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
>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
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