LM386 to 3.2 ohm speaker?

[Father Haskell]

Building small guitar practice amp. Available junk box parts include
several 4" 3.2 ohm speakers culled from a 1984 vintage cassette
boom box. Since the schemos I've seen all call for 8 ohm speakers,
should I expect these speakers to sound like crap, or will they
likely
sound okay?

 

[Brian Gregory [UK]]

"Father Haskell" <fatherhaskell@yahoo.com> wrote in message
news:49701d37-8952-40df-869d-19411a93db7a@k15g2000vbd.googlegroups.com...

Building small guitar practice amp. Available junk box parts include
several 4" 3.2 ohm speakers culled from a 1984 vintage cassette
boom box. Since the schemos I've seen all call for 8 ohm speakers,
should I expect these speakers to sound like crap, or will they
likely
sound okay?

The main problem would be the possibility of the LM386 overheating and
dieing.

You could put two speakers in series to get 6.4 ohm which would be somewhat
better.

You should also increase the output coupling capacitor to match the reduced
impedance of the loudspeaker if you want to keep the bass response the same
as in the design intended for an 8 ohm speaker.

--

Brian Gregory. (In the UK)
ng@bgdsv.co.uk
To email me remove the letter vee.

 

[Father Haskell]

On Apr 25, 2:44 pm, "Brian Gregory [UK]" <n...@bgdsv.co.uk> wrote:

"Father Haskell" <fatherhask...@yahoo.com> wrote in message

news:49701d37-8952-40df-869d-19411a93db7a@k15g2000vbd.googlegroups.com...

Building small guitar practice amp.  Available junk box parts include
several 4" 3.2 ohm speakers culled from a 1984 vintage cassette
boom box.  Since the schemos I've seen all call for 8 ohm speakers,
should I expect these speakers to sound like crap, or will they
likely
sound okay?

The main problem would be the possibility of the LM386 overheating and
dieing.

You could put two speakers in series to get 6.4 ohm which would be somewhat
better.

Which is what I've done, and it works well. The IC doesn't even
get detectably warm, even at full gain. A two speaker cab just
plain looks cooler. I wish I had four, so I could build a miniature
"Marshall" stack.

You should also increase the output coupling capacitor to match the reduced
impedance of the loudspeaker if you want to keep the bass response the same
as in the design intended for an 8 ohm speaker.

Current setup (220 uF output cap) does sound a bit thin, with
definite
cutoff of the all-important bass frequencies. Thanks for the tip.

 

[Brian Gregory [UK]]

"Father Haskell" <fatherhaskell@yahoo.com> wrote in message
news:21197147-daa3-45b5-8263-201be9cf4730@k15g2000vbd.googlegroups.com...

Current setup (220 uF output cap) does sound a bit thin, with definite
cutoff of the all-important bass frequencies. Thanks for the tip.

Yes 220uF is about 8 ohm impedance at 90Hz.

Depending on the speakers and their mounting you might try anything up to
around 1000uF and see if you can hear an improvement.

--

Brian Gregory. (In the UK)
ng@bgdsv.co.uk
To email me remove the letter vee.