linux-kernel - Re: PC speaker

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Message-ID: <466FB758.1020104@aitel.hist.no>
Date:	Wed, 13 Jun 2007 11:22:32 +0200
From:	Helge Hafting <helge.hafting@...el.hist.no>
To:	Jan Engelhardt <jengelh@...putergmbh.de>
CC:	David Schwartz <davids@...master.com>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Re: PC speaker

Jan Engelhardt wrote:
> Since you can set the x86's crystals frequency from 1193182 to 18 Hz
> (PIT_TICK_RATE / 1 to PIT_TICK_RATE / 65535) [*], you can never really
> bust it. But even then, what would a speaker do it was constanly given
> +5V? (I _suppose_ the other level is 0V, not -5V -- makes for easy 
> design.) That's IMO just like a sound file with volume(x) = 1, nothing 
> spectacular if you ask me.
>   

I guess a motherboard don't provide enough current to
burn out that speaker.

But generally, speakers that handle some maximum
alternating current *will* burn out if you give them
the same amount DC.  This becasue speakers
are designed to handle AC - some of the energy is dissipated
as sound waves, some as an alternating magnetic field,
some has heat. And the speaker moves, so moving
air helps cooling it.

A speaker getting DC converts all that current into heat only,
and it stands still so no extra cooling.  So it burns out.

Helge Hafting

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