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Richard - 29 May 2005 22:29 GMT

A bit off topic, but I have a question about speakers:
I made a little sound kit for my son but its a bit quiet. It has a 0.3W 8
ohm speaker on it. If I were to make an amp kit (Maplins do a 7W and a 30W,
what sort of speaker should I use? The amp kit says 15W into 4 ohm, if I buy
two car speakers from Maplin does it matter about the ohm rating? Maplin do
a 4" and 5" (p.382 of the cat. if anyone has one) pair that are rated power
wise but it doesn't say the ohm rating. Does this matter?

Thanks in advance
Richard

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Mother - 29 May 2005 23:25 GMT

>A bit off topic, but I have a question about speakers:
>I made a little sound kit for my son but its a bit quiet. It has a 0.3W 8
[quoted text clipped - 3 lines]
>a 4" and 5" (p.382 of the cat. if anyone has one) pair that are rated power
>wise but it doesn't say the ohm rating. Does this matter?

Erm, this posting seems odd, partly because you're sort of
demonstrating you know what you're doing by building Maplin kits (and
well done too, this is about the only thing which is going to keep
electronics alive IMO). But then you're asking something to do with
Ohm's Law...??? :-)

Anyway, I've got a little calc on my site which can help in these
matters:

http://www.101fc.net/

Right at the very bottom of the main page.

Keep building those little kits BTW, I've been doing them for nearly
40 years with one excuse or another... I still can't resist those
cheap 5 quid kits, even knowing that I can get the components
individually for around 20p :-)

RIP Practical Wireless Magazine

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Richard - 30 May 2005 09:07 GMT

Thanks for the reply. The sound kit is a darth vader voice voive changer I
got from Australia and I have adapted it to sound like a dalek. I assume you
treat speakers the same as resistors as in series or parallel?
Richard

>>A bit off topic, but I have a question about speakers:
>>I made a little sound kit for my son but its a bit quiet. It has a 0.3W 8
[quoted text clipped - 27 lines]
>
> RIP Practical Wireless Magazine

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Mother - 30 May 2005 20:56 GMT

>Thanks for the reply. The sound kit is a darth vader voice voive changer I
>got from Australia and I have adapted it to sound like a dalek.

Crumbs, I made something similar many (too many) years ago.
Like I said, RIP Practical Wireless Magazine...
Oh the joy of the 555 timing chip :-)

>I assume you treat speakers the same as resistors as in series or parallel?

I seriously wouldn't bother to worry too much IIWY, as there's not
enough power output to compensate for. One other option for you would
be to buy some computer speakers from a computer fair or jumble -
around 50p should do it.

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Dave Liquorice - 29 May 2005 23:36 GMT

> The amp kit says 15W into 4 ohm, if I buy two car speakers from
> Maplin does it matter about the ohm rating?

It's not critical at these sort of power levels. Hang a 4 ohm speaker
off an amp designed for 8, the amp will just run a bit warmer than it
should. Hang 8 of an amp designed for 4 it just won't go as loud
before clipping.

Signature

Cheers new5pam@howhill.com
Dave. pam is missing e-mail

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