[HacktionLab] 12 volt calculator

kriptick kriptick at riseup.net
Mon Apr 11 16:24:16 UTC 2011


Prob very handy although at the moment, the calculator part doesn't actually
do anything on my (likely broken) browser. I'm not too up on current PA
stuff but one thing I do know is that we live in a very imperfect world.
Anyone else ever noticed this? ;-) Amplifiers never convert all the ingoing
power to output power and how much is lost depends on their class.
http://en.wikipedia.org/wiki/Class_C_amplifier#Class_B
Traditional class B can never be better than ~78% but class D can be well
into the 90s so maybe have a control for class or else directly type in any
stated efficiency given by manufacturer? Or am I years out of date & just
about all PA stuff is class D? If you want to get picky then you could have
a music/speech control as harsh rave music is almost continuously loud
whereas speech is much more peaky with significant lulls so would prob
consume something like 3 times less power though I'm sure there are figures
for this somewhere? Also seems to me you shouldn't dis 24V gear as being
inappropriate as, to my mind 24V should be significantly more efficient as
well as capable of far higher output power than 12V.
The other thing that should be emphasised in the text is that low voltage
systems need to have all power & spkr cables as short as poss & seriously
fat - I squared R etc. Not easy I know these days when scrap copper is a
fiver a kilo. Many activisty people I've spoken to think 12V is mostly about
safety & assume low voltage means you can use skinny wires whereas you 
should really be using welder cable.
hth


----- Original Message ----- 
From: "Mike Harris" <mike at mbharris.co.uk>
To: <hacktionlab at lists.aktivix.org>
Sent: Thursday, April 07, 2011 3:41 PM
Subject: [HacktionLab] 12 volt calculator


> Hey All,
>
> Some friends were asking me the other day about 12 volt stuff: basically
> how many batteries would they need to run their mobile amp for X hours
> for a little rave up.
>
> I've been asked it before and started to explain it, but thought it'd be
> better on a web page, so I put together the following article, featuring
> some javascript calculators.
>
> I submit it to the hacktionlab list for peer-review and any comments,
> additions, corrections, etc, much appreciated:
>
> http://mbharris.co.uk/12-volt-sound-system-battery-calculator/
>
> I could move the text content to the wiki if that made it more open....
>
> Cheers,
>
> Mike.
>
> -- 
> Mike Harris
> w: http://mbharris.co.uk
> t: +44 7811 671 893
> 0: http://mbharris.co.uk/keys/pgp.html
>
>
> _______________________________________________
> HacktionLab mailing list
> HacktionLab at lists.aktivix.org
> https://lists.aktivix.org/mailman/listinfo/hacktionlab




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