KanoMaster22
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Speaker Wattage and Resistance Questions

Tue Sep 25, 2018 4:54 pm

Just a quick question. If a tutorial says use a 8 ohm 1 watt speaker does it matter if I use a speaker under these numbers? For example would it matter if I used a 2 ohm 0.6 watt speaker.

Thanks,
Louis P

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Burngate
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Re: Speaker Wattage and Resistance Questions

Tue Sep 25, 2018 5:46 pm

If the amplifier driving it is designed for no less than 8 ohms, then it may well die if you connect a 2 ohm speaker.
If the amplifier doesn't die, then it may well kill the speaker.

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FTrevorGowen
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Re: Speaker Wattage and Resistance Questions

Tue Sep 25, 2018 6:15 pm

Burngate wrote:
Tue Sep 25, 2018 5:46 pm
If the amplifier driving it is designed for no less than 8 ohms, then it may well die if you connect a 2 ohm speaker.
If the amplifier doesn't die, then it may well kill the speaker.
+1
Possible solutions:
Use four of the 2 ohm speakers in series if you have them (total resistance 8 ohms, if the amp is delivering 1W that's 0.25 per speaker - but whether a "good" sound/volume exists is another matter)
Use a 5.6 ohm 1W resistor in series with the 2ohm speaker - but don't expect much volume ....
Trev.
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LTolledo
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Re: Speaker Wattage and Resistance Questions

Wed Sep 26, 2018 11:36 am

KanoMaster22 wrote: For example would it matter if I used a 2 ohm 0.6 watt speaker.
KABOOOM! It will kill the speaker at full volume! But will probably survive if you keep the volume 25% and below. And dont expect good sound quality...

You might be tempted (and probably itching already ;) ) to try.... but do it at your own risk..... :!:
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

KanoMaster22
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 6:02 am

Thanks for the help everyone. What would happen if I used a 16 ohm 0.5W speaker?

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rpdom
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 7:09 am

KanoMaster22 wrote:
Fri Sep 28, 2018 6:02 am
Thanks for the help everyone. What would happen if I used a 16 ohm 0.5W speaker?
That would be safe, but it would be quieter than the 8 Ohm speaker.

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Burngate
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 8:16 am

Amplifiers, like a lot of things, are voltage sources - they attempt to give a constant voltage whatever the load, up until too much current kills something.

It might be worth your while learning about Ohm's law - that's about volts, amps and resistance and how they relate to each other.
Also, how volts and amps relate to power.

Two equations: V = I * R and P = V * I

Obviously, V stands for Volts and voltage, P stands for power in Watts, and R is resistance in Ohms, but why on earth is I used for current in Amps? - if you find out please let me know!

jahboater
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 8:48 am

rpdom wrote:
Fri Sep 28, 2018 7:09 am
KanoMaster22 wrote:
Fri Sep 28, 2018 6:02 am
Thanks for the help everyone. What would happen if I used a 16 ohm 0.5W speaker?
That would be safe, but it would be quieter than the 8 Ohm speaker.
Yes.
It would be 3db quieter which you may not hear.
(That is, the power would go down by half - which may be a good thing if your amp is > 0.5W).

Adding resistors or using multiple speakers in series will affect the sound quality (damping factor) but again, my guess is you wont hear the difference.

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Mortimer
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 9:17 am

Is it worthwhile mentioning that a speaker is not 8 Ohms 'resistance' (or 2 Ohms or whatever), it is 'impedance'. Series connection of speakers of the same type will in all likelihood work in the way suggested, but different speakers might not. The Impedance figures are at a specific frequency, usually 400Hz. The Impedance characteristics away from 400Hz could vary quite significantly, hence why speaker cross-over design is quite difficult and considered to be an 'art' by some.

As already stated, going higher in impedance (16 Ohms) means a reduction in speaker sensitivity, i.e. it's response to a particular peak to peak Voltage level of the driving signal, and hence the safer direction to go in.

jahboater
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 10:04 am

Mortimer wrote:
Fri Sep 28, 2018 9:17 am
The Impedance figures are at a specific frequency, usually 400Hz. The Impedance characteristics away from 400Hz could vary quite significantly, hence why speaker cross-over design is quite difficult and considered to be an 'art' by some.
Yes indeed.
See these graphs ...
https://www.google.co.uk/imgres?imgurl= ... AHoECAcQBg

There will be no crossover in these little speakers, so I guess its just inductance and resistance.

The simple notional 8ohms / 16ohms is probably good enough for the basic discussion above ...

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Paeryn
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 11:53 am

Burngate wrote:
Fri Sep 28, 2018 8:16 am
but why on earth is I used for current in Amps? - if you find out please let me know!
I is what Ampère used for Current Intensity (Intensité de courant). Here in the UK we originally used C but we had swapped over to using I by the turn of the 20th century.
She who travels light — forgot something.

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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 1:47 pm

Paeryn wrote:
Fri Sep 28, 2018 11:53 am
Burngate wrote:
Fri Sep 28, 2018 8:16 am
but why on earth is I used for current in Amps? - if you find out please let me know!
I is what Ampère used for Current Intensity (Intensité de courant). Here in the UK we originally used C but we had swapped over to using I by the turn of the 20th century.
And the use of "i" for current is why, in electrical and electronic engineering, the square root of -1 is "j".

ejolson
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 4:29 pm

Burngate wrote:
Fri Sep 28, 2018 8:16 am
Amplifiers, like a lot of things, are voltage sources - they attempt to give a constant voltage whatever the load, up until too much current kills something.
What you say is true if the amplifier output stage uses transistors but not true if vacuum tubes are used. For tubes a two ohm impedance represents less load than eight and is subsequently easier to drive.

KanoMaster22
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 4:46 pm

Thank you again everyone! I understand how to speakers work a lot better know.

Thanks,
LouisP

jahboater
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Re: Speaker Wattage and Resistance Questions

Fri Sep 28, 2018 6:59 pm

ejolson wrote:
Fri Sep 28, 2018 4:29 pm
Burngate wrote:
Fri Sep 28, 2018 8:16 am
Amplifiers, like a lot of things, are voltage sources - they attempt to give a constant voltage whatever the load, up until too much current kills something.
What you say is true if the amplifier output stage uses transistors but not true if vacuum tubes are used. For tubes a two ohm impedance represents less load than eight and is subsequently easier to drive.
They usually have an output transformer, so can easily match any impedance the designer chooses.
Sometimes there is a choice - via "taps" into the transformer.

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