

05052006, 12:44 AM

#2

In Runtime
Join Date: Apr 2006
Posts: 220

Re: stereo ohms?
By definition from Ohm's Law, a device has a resistance of one ohm if a voltage of one volt causes a current of one ampere to flow (R = V/I). Alternatively and equivalently, a device that dissipates one watt of power with one ampere of current flowing through it has a resistance of one ohm (R = P / I 2).
Since 1990, the ohm has been maintained internationally using the quantum Hall effect, where a conventional value is used for the 'vonKlitzing constant', fixed by the 18th General Conference on Weights and Measures as R{K90} = 25812.807 Ω.
The complex quantity impedance is a generalisation of resistance. Its real part is resistance and its imaginary part is reactance. Impedance, resistance and reactance all have units of ohms.
The symbol for the ohm is the Greek capital letter omega (Ω). If the Greek letter cannot be used, the word ohm is used instead. The various guides for the use of the International System of Units do not explicitly forbid the elision of the final "o" of some SI prefixes, although there is nothing in them to suggest that it is allowable, either. As a result, one is just about as likely to see "kilohm", "kiloohm" and even "kiloohm", and the same holds true for hecto, micro, nano, pico, femto, atto, zepto, and yocto. The only other SI unit to suffer from this kind of orthographic uncertainty is the ampere. In the particular case of the ohm, one even sees the "a" prefixes lose that vowel: hence megohm and gigohm. Higher prefixes are rarely used with ohm. In the other direction, milliohms (or millohms) are seen where the resistance of cables, etc., are measured.
Units of ohms, kilohms (103 Ω) and megohms (106 Ω) are used in electronic design documentation. On schematic diagrams kilohms are abbreviated "K" and megohms are abbreviated "M". Thus, 33 kilohms would be rendered as 33K, and 5.1 megohms would be 5.1M. Values less than 1K are rendered without any symbol following the number, so 680 ohms would simply be shown as 680. This does not cause confusion, because the numeric value is placed next to a schematic symbol for a resistor, and the resistor is usually identified by a reference designator, R, plus a numeric part, e.g., R12.
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05052006, 12:48 AM

#3

Golden Master
Join Date: Apr 2005
Posts: 16,073

Re: stereo ohms?
oh yeah, i fully understand that lol
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05052006, 12:51 AM

#4

In Runtime
Join Date: Apr 2006
Posts: 220

Re: stereo ohms?
LOL I am actually being a smart ass, I have no freaking clue either, LOL
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The night I laid my eyes on you, Felt everything around me move, Got nervous when you looked my way, But you knew all the words to say, And your love slowly moved right in, All this time, oh my love, where you been, Mi, Amore Don't you know, My love I want you so,
Sugar, You make my soul complete, Rapture tastes so sweet.



05052006, 12:53 AM

#5

Golden Master
Join Date: Apr 2005
Posts: 16,073

Re: stereo ohms?
hahaha, why doesnt that surprise me lol
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05052006, 01:01 AM

#6

Daemon Poster
Join Date: Sep 2004
Posts: 1,321

Re: stereo ohms?
http://www.audioallies.com/GetFeatur...ture=Impedance
I beleive this explains what you want. I don't feel like reading the whole thing, but yeah, I've been wondering the same thing. I might check it out tommarow. Too tired now :P
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05052006, 01:05 AM

#7

Golden Master
Join Date: Apr 2005
Posts: 16,073

Re: stereo ohms?
they dont beeive in paragraphs lol, thanks dude
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05052006, 01:08 AM

#8

Golden Master
Join Date: Apr 2005
Posts: 16,073

Re: stereo ohms?
Quote:
The resistance to the flow of an electric current in a circuit measured in ohms. Impedance is what restrains the flow an electric current making it more difficult for the current to move through a circuit. Impedance is similar to a dam in a river. If the river is a circuit (to be a true circuit the river would need to run in a complete circle) then the water is the electric current. The water flows freely when there are no obstructions to resist the flow. The dam in the river resists the flow of water. By fully opening the dam there is no resistance. The further closed the dam becomes, the more difficult it is for the water to flow.
A dam of 1 ohm would have very little resistance (although a dam's resistance to water is not measured in ohms, impedance is and so ohms will be used for this example). As the dam's resistance to the water's flow, it's impedance, increases to 2 ohms it becomes more difficult for the water to flow. Similarly, as the dam's impedance grows to 4 ohms and then 8 ohms and beyond it becomes more and more difficult for the water to flow. In an electric current, low impedance lets more current flow.
A well designed amplifier with a strong power supply will double the amount of power in watts that it sends to a speaker with each halving of impedance. For instance, an amplifier might send 100 watts to a speaker with an 8ohm impedance. When the impedance is halved to 4 ohms that amplifier would send out 200 watts of power. In the real world, few amplifiers are actually able to double their power output as impedance halves due to limitations on their power supply and design. Additionally, few amplifiers are able to put out power for any significant length of time with impedances of 3 ohms or less (the amplifier must be able to supply huge amounts of power as the impedance decreases below 4 ohms  in fact, many receivers cannot operate below 6 or even 8 ohms).
When shopping for speakers, you will see figures stating the nominal impedance of a speaker (most speakers have a nominal impedance of between 4 and 8 ohms). This is the speaker's average resistance to the flow of current through the circuit going from the amplifier into the speaker and back to the amplifier. However, this figure is only the average impedance rating across all frequencies into which the speaker produces output. In reality, the impedance may drop at some points to 2 or 3 ohms and may reach 40, 50 or even 60 ohms at other frequencies. For this reason, it is beneficial to have a strong amplifier able to produce large amounts of power down into small impedance loads.
Generally, receivers should be mated with speakers having a nominal impedance of 8 ohms or so while separate amplifiers may be used with speakers with nominal impedances of 4 ohms or so. A speaker with an 8 ohm nominal impedance will not generally have as low a minimum impedance as a speaker with a lower nominal impedance such as a 4 ohm speaker. The most important impedance rating to be aware of is that used with speakers. You may also see impedance ratings for speaker wire and other types of wire. In most cases thicker, heavier gauge wire (such as 10 or 12 gauge) will have a lower impedance and allow more current to flow through. In essence, lower impedance means lower resistance allowing more power to pass through while higher impedance restricts power thus restricting the amount of current able to flow in a circuit.

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05052006, 01:15 AM

#9

Daemon Poster
Join Date: Mar 2005
Posts: 1,144

Re: stereo ohms?
Ohms is resistance, The higher the ohms, more resistance.
If you have an Amplifier that is rated at a 100watts @4 ohms, Your Amp will supply the full 100 watts..
An amplifier designed to put out 100 watts into 8 ohms will put out 200 watts into 4 ohms.
The amp produces 100 watts at 4 ohms. When the resistances is increased to 16 ohms, four times what it was rated, the amplifier produces one fourth as many watts.
If you have a 500 watt Amp rated at 8 ohms, Your getting 500 watts. If the Ohms (resistance) is lowered to 4, theoretically you should get 1000watts.
Its simply resistance....
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05052006, 01:20 AM

#10

Golden Master
Join Date: Apr 2005
Posts: 16,073

Re: stereo ohms?
so...
a 100watt at 4ohms is full power. but 100watts at 8ohms gives me 50watts per 4ohms? then technicly i still get all the wattage?
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