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Old 17th August 2016, 05:33 AM   #1
Pauld35 is offline Pauld35  New Zealand
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Default basic speaker impedance question help needed

hello,

i have a 15w solidstate amp manufactured with no output transformer.
its has a 16 ohm speaker factory.
im wanting to connect 6ohm speaker, can i just buy an 8ohm transformer rated for 15w min and connect it between the amp and speaker to get 14ohms, which is pretty close to what i need?

thanks
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Old 17th August 2016, 06:18 AM   #2
Pafi is offline Pafi  Hungary
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No. No such thing like "8 ohm transformer". You can use transformer, to be more specific an autotransformer, but it doesnt work like this. A transformer doesnt add impedance. It multiplies impedance by the square of turns ratio. But Im not sure if you really need this...

you can buy a modern amplifier module cheaper than a good transformer.
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Old 17th August 2016, 06:19 AM   #3
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No, that is not how transformers work. If you just want to raise the impedance seen by the amp output, you could add a 10 ohm resistor, 10 Watts or better power rating, in series with your 6 ohm speaker (but you will be wasting most of your amp's power output). What that resistor will do to the damping of your speaker is a different story. Listen to it and see if it sounds acceptable - some speakers are less finicky than others. If this is a stereo amp, you need two resistors, one in series with each speaker.

You could also try driving your 6 ohm speaker directly. Most amps will drive lower impedances, at the cost of a little more distortion. Cranking up the volume, however, WILL overload the amplifier, so be careful. Do not turn the volume control more than 30-40%. Mark that on the amp faceplate.

Last edited by SamAnytime; 17th August 2016 at 06:21 AM.
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Old 17th August 2016, 06:30 AM   #4
Pauld35 is offline Pauld35  New Zealand
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so maybe just put a resistor on the volume pot so no one can cook it, cheers
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Old 17th August 2016, 06:33 AM   #5
Mooly is offline Mooly  United Kingdom
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What is the make of amplifier ? In practice there may not be much of a problem just using your new speakers directly.
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Old 17th August 2016, 07:33 AM   #6
Pauld35 is offline Pauld35  New Zealand
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Quote:
Originally Posted by Mooly View Post
What is the make of amplifier ? In practice there may not be much of a problem just using your new speakers directly.
hello its thorn solid state radio, pnp i think,
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Old 17th August 2016, 07:40 AM   #7
Mooly is offline Mooly  United Kingdom
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That is an oldie

I'd bet you would be just fine using your replacement speaker direct. You will probably find the new speaker more efficient and so that will mitigate against it drawing more current. Try it.
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Old 17th August 2016, 08:27 AM   #8
JMFahey is offline JMFahey  Argentina
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First and foremost, WHICH amp do you have?
Brand and model.

Its quite unusual, to say the least, that an SS amp is designed for 16 ohms, with the very rare exceptions of a couple weird English Hi Fi amps from the mid 60s.
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Old 17th August 2016, 08:56 AM   #9
JMFahey is offline JMFahey  Argentina
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Oh, now I see, you answered while I was writing.
I seem to have hit the nail in the head: old, weird British and probably using germanium.

1) what happened to the original speaker? It could probably be reconed to original spec, specially in the UK, somebody might have a suitable 16 ohms voice coil stashed somewhere.

2) second best, I think the speaker is mounted to the front top panel, behind that grill cloth, would be to remove said speaker panel and make a new one, with two 8 ohms speakers in series.

Best of both worlds: 16 ohms and better speakers.

3) wild plan: IF you are in the UK, some dealer might still have a dusty moldy 16 ohms speaker in his basement or even some shelf, ask a couple.

Does Wilmslow Audio still exist?
They used to be the speaker kings.
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Old 17th August 2016, 08:57 AM   #10
Pauld35 is offline Pauld35  New Zealand
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hello. its thorn solid state radio,made in nz, will be copied from the English. pnp i think, i posted a picture. it is from the 60's
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