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Post subject: Re: Speaker ohms -is higher or lower ohms better?
Posted: Tue Oct 21, 2014 7:09 pm
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omar59 wrote:
http://www.prestonelectronics.com/audio/Impedance.htm


He says in big bold capital letters ADDING SPEAKERS DECREASES THE TOTAL OHMS IMPEDANCE.

What he should say is ADDING SPEAKERS IN PARALELL DECREASES THE TOTAL IMPEDANCE, ADDING SPEAKERS IN SERIES INCREASES THE TOTAL IMPEDANCE.

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Post subject: Re: Speaker ohms -is higher or lower ohms better?
Posted: Tue Oct 21, 2014 8:35 pm
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GilgaFrank wrote:
omar59 wrote:
http://www.prestonelectronics.com/audio/Impedance.htm


He says in big bold capital letters ADDING SPEAKERS DECREASES THE TOTAL OHMS IMPEDANCE.

What he should say is ADDING SPEAKERS IN PARALELL DECREASES THE TOTAL IMPEDANCE, ADDING SPEAKERS IN SERIES INCREASES THE TOTAL IMPEDANCE.

This is getting spooky...

I mean, if more than two guys said this, wouldn't you consider them bad ohm-men?


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Post subject: Re: Speaker ohms -is higher or lower ohms better?
Posted: Wed Oct 22, 2014 12:57 am
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Highline wrote:
I mean, if more than two guys said this, wouldn't you consider them bad ohm-men?


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Post subject: Re: Speaker ohms -is higher or lower ohms better?
Posted: Wed Oct 22, 2014 10:36 am
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arth1 wrote:
(Ohm, not "ohms". You don't say Fahrenheits either. //grammarnazi)
Yes and no. A 50W 4Ω amp with a 50W 4Ω speaker will sound exactly as loud as a 50W 8Ω amp with a 50W 8Ω speaker.
However, if you put the "wrong" impedance speaker on an amp, it can sound weaker - or louder. Before it burns up the output stage of your amp, that is.


I am not an audio engineer, but based on transmission line theory, I find it hard to understand how the above could be true.

The power delivered to the load on any impedance-matched transmission line is inversely proportional to the characteristic impedance of the line. So, all other things being equal, and assuming all impedances are matched, a lower impedance should provide more power to the speakers.

Also, since maximum power is delivered to the load when all impedances are matched, I find it hard to understand how a speaker could sound louder with an impedance mismatch - how can you drive a speaker harder with less power?

Admittedly, four octaves seems like a lot of bandwidth to try to maintain a constant impedance over.

We don't say "Fahrenheits" because it is the name of the scale, not the units. The units of the Fahrenheit scale are degrees.

arth1 wrote:
Epynomous units do not get an s in plural.

10 Watt, not Watts
10 Ohm, not Ohms
10 Volt, not Volts
10 Becquerel - not Becquerels
10 Kelvin - not Kelvins
10 Hertz - not Hertzes
10 Siemens - not Siemenses

Maybe in your neck of the woods, but here in 'murica, we follow a different convention. They are not pluralized if they are part of a compound modifier, such as when stating a spec: "Dan999 needs an 8-ohm cable." But the ones that don't end in s do get pluralized with an s otherwise: "Dan999 needs a cable with an impedance of eight ohms." The one that ends in z doesn't get an s at all, it hertz my head just to think about adding an s to that. :wink: (Yes, I edited that last sentence.)

Also, eponymous or not, we do not capitalize the first letter when writing the name of the unit, e.g. "ten volts". However, the first letter is capitalized when it is used as the unit abbreviation, e.g. "10 V".

Al 87 wrote:
Hi Matt

Well now we are getting into the nitty gritty of grammar lol. I think if it's a reference to the man, ie Ohm's Law then it would probably be Ohm's.

If were talking plural units then ohms is good. As we also use microohm, megohm etc
maybe that's where differences emerge in various parts of the world regarding the use of the "s"?

:wink:

.. Al
+1, Al. And I have always found "maths" an interesting description. :wink:

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Post subject: Re: Speaker ohms -is higher or lower ohms better?
Posted: Wed Oct 22, 2014 1:27 pm
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spacewolf wrote:
The power delivered to the load on any impedance-matched transmission line is inversely proportional to the characteristic impedance of the line. So, all other things being equal, and assuming all impedances are matched, a lower impedance should provide more power to the speakers
Actually, at low frequencies, I will concede this point. You can probably get an excellent approximation with P = IV.

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Post subject: Re: Speaker ohms -is higher or lower ohms better?
Posted: Wed Oct 22, 2014 5:36 pm
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So how does this translate to any sonic differences? Little more speaker compression or speaker distortion? 4 ohm(s) being a little hotter than 16? Or is it just the wrong measure for any sonic difference? Other measures (freq range etc..) being a better way to list differences in speaker performance. Kinda like the way you can't always tell the hotness of a pickup by the DC resistance, although many people use this as a measure for output.

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Post subject: Re: Speaker ohms -is higher or lower ohms better?
Posted: Wed Oct 22, 2014 6:42 pm
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Deluxe Matt wrote:
So how does this translate to any sonic differences? Little more speaker compression or speaker distortion? 4 ohm(s) being a little hotter than 16? Or is it just the wrong measure for any sonic difference? Other measures (freq range etc..) being a better way to list differences in speaker performance. Kinda like the way you can't always tell the hotness of a pickup by the DC resistance, although many people use this as a measure for output.
Actually, I don't know. Whatever happened to BlueSkyBill? That guy builds amps for a living, he could probably give us definitive answers.

However, I think the punch line is just to make sure you impedance match everything.

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Post subject: Re: Speaker ohms -is higher or lower ohms better?
Posted: Wed Oct 22, 2014 11:07 pm
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spacewolf wrote:
spacewolf wrote:
The power delivered to the load on any impedance-matched transmission line is inversely proportional to the characteristic impedance of the line. So, all other things being equal, and assuming all impedances are matched, a lower impedance should provide more power to the speakers
Actually, at low frequencies, I will concede this point. You can probably get an excellent approximation with P = IV.


You are not dealing with any single frequency when it comes to instrument amplifiers, thus the impedance is often mismatched no matter the speaker nominal rating anyway. And, yes the impedance rating of amp is done with a fixed resistance, not a speaker. So, in an instrument amp, a lower or higher impedance than rated load, will result in less power from the amp, as that power never develops to begin with except with a "matched" impedance.

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Last edited by shimmilou on Wed Oct 22, 2014 11:11 pm, edited 1 time in total.

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Post subject: Re: Speaker ohms -is higher or lower ohms better?
Posted: Wed Oct 22, 2014 11:10 pm
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spacewolf wrote:
Deluxe Matt wrote:
So how does this translate to any sonic differences? Little more speaker compression or speaker distortion? 4 ohm(s) being a little hotter than 16? Or is it just the wrong measure for any sonic difference? Other measures (freq range etc..) being a better way to list differences in speaker performance. Kinda like the way you can't always tell the hotness of a pickup by the DC resistance, although many people use this as a measure for output.
Actually, I don't know. Whatever happened to BlueSkyBill? That guy builds amps for a living, he could probably give us definitive answers.

However, I think the punch line is just to make sure you impedance match everything.


I think that this was answered before. Speaker/amp impedance really means nothing as far as sound, it is about getting power from the amp. So, matched impedance for the most power from amp. All else being equal, a 4 ohm 50 watt amp will sound the same as an 8 ohm 50 watt amp.

Impedance matching in a tube amplifier is very misundurstood, and you will not damage your amp or speakers are mismatched within a 2 to 1 ratio, high or low. Impedance matching is simply about getting the most power from the amp, no more.

The real danger lies in using too high an impedance load for a tube amp. At some point the impedance is too high to provide enough counter-EMF, and the result can be a blown OT and/or tubes as well as other damage. An open circuit, i.e. no speaker connected, is the worst case scenario. Shorting the output of a tube amp will actually protect the amp from damage when used with no speaker, as evidenced by the use of shorting jacks on the output of many tube amps. This is also a clue that a lower impedance speaker than rated will not harm your amp. :idea:

And no, bluesky636 did not build amps for a living, he was an engineer and he put together a couple of amp kits (one not done well either), and modified a couple more amps.

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