OT - speakers

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

On Sun, 29 May 2005 21:29:07 GMT, "Richard" <[email protected]>
wrote:

>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?

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

On Sun, 29 May 2005 21:29:07 GMT, Richard wrote:

> 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.

--
Cheers [email protected]
Dave. pam is missing e-mail

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


"Mother" <"@ {m} @"@101fc.net> wrote in message
news:[email protected]...
> On Sun, 29 May 2005 21:29:07 GMT, "Richard" <[email protected]>
> wrote:
>
>>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?
>
> 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
>

On Mon, 30 May 2005 08:07:09 GMT, "Richard" <[email protected]>
wrote:

>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.