#1
HI, im wandering what ohms are (in a guitar speaker/ head) and how they effect sound or tone. thanks!
#3
Ohms is a measurement of resistance to the flow of electrical current. Amps are designed to work properly with a particular range of ohms. Just follow the rules as specified and don't worry about how it affects tone, because that isn't an issue.
#4
Quote by fly135
Ohms is a measurement of resistance to the flow of electrical current. Amps are designed to work properly with a particular range of ohms. Just follow the rules as specified and don't worry about how it affects tone, because that isn't an issue.

+1 All you need to be familiar with is basic math; like knowing when one number is the same as the other. If the two numbers are the same you're ok, if they're not that's bayad.
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#5
regarding guitar amps, though, assuming you're talking about speaker outputs, ohms refer to impedance. it's resistance plus reactance, or something like that. Basically because music is frequency based (ac, in other words). I'd explain more but that's more or less the limit of my understanding.

EDIT: yeah match the impedances unless you know what you're doing or unless the manual specifically tells you what mismatch is ok.
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Last edited by Dave_Mc at Jun 16, 2010,
#6
V=IR therefore R=V/I

Where V is volts, I is current, and R is resistance (Measured in Ohms)
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#7
Quote by kingpenguin
V=IR therefore R=V/I

Where V is volts, I is current, and R is resistance (Measured in Ohms)



I've got an exam on this shit tomorrow and I'm on UG!


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#8
Quote by Dave_Mc
regarding guitar amps, though, assuming you're talking about speaker outputs, ohms refer to impedance. it's resistance plus reactance, or something like that. Basically because music is frequency based (ac, in other words). I'd explain more but that's more or less the limit of my understanding.

EDIT: yeah match the impedances unless you know what you're doing or unless the manual specifically tells you what mismatch is ok.


resistance,reactance,inductance.

resistance refers to direct current impedance refers to alternating current.

in terms of tone it has no measurable effect

if you have a 1 x 12 cab at 16 ohm (ala peavey valveking) and wanted to connect a additional 12 inch 16 ohm speaker, you would select the 8 ohm setting on the selector switch at the back of the amp. mismatching the impedance could cause damage to the power amplifier circuits.
Last edited by ibanezgod1973 at Jun 16, 2010,
#9
Quote by ibanezgod1973
resistance,reactance,inductance.

resistance refers to direct current impedance refers to alternating current.
.


aye, exactly

it's not resistance, in other words. There's a whole pile of guff with imaginary numbers n stuff. that's about where i stopped reading
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Quote by K33nbl4d3
I'll have to put the Classic T models on my to-try list. Shame the finish options there are Anachronism Gold, Nuclear Waste and Aged Clown, because in principle the plaintop is right up my alley.

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Presumably because the CCF (Combined Corksniffing Forces) of MLP and Gibson forums would rise up against them, plunging the land into war.

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Et tu, br00tz?
#10
Quote by Tedward
I've got an exam on this shit tomorrow and I'm on UG!


FFFUUUUUUUUUUUUUUUUUU

Just draw the damn triangle.


...............E

..........I.........R


Cover the variable you want to find and the other two will show you the equation.

For example, if you want E, cover it. You're left with IR, so multiply them.

Or if you cover I, you're left with E/R. Simple.

Then when you remember that Power P = EI you can derive every most other basic electrical equations from it.

Z for impedance is a bit different, but I won't go into that.
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#11
well actually finding current, resistance, voltage, I'm good at that.


Dynamics, Kinematics, Circular Acceleration and Force, Gravitational Escape Velocities... that's the hard part.


Thanks though.

#12
^i programed that stuff in my graphing calculator. i sucked at math and physics, but i went to school for computer science, and i can program it into a calculator, woohoo for cheating!

but, as been touched on here, there is many definitions or ways to think about impedance/resistance. if you just care about the basics, then just know the resistance 'resists' the flow of electrons, much the way a hairball clogs a pipe.

if you want to better understand what is happening with your amplifier then you have to get much more specific. you have to understand that the impedance your cab provides is a variable resistance and changes... alot... sympathetically to a bunch of different things. and you must also get around your head that impedance is not something that is measured very accurately for a rating (impedance ratings don't give much insight into what is going on between a head and a cab).

start with squit's link, then go to
http://en.wikipedia.org/wiki/Electrical_impedance
http://en.wikipedia.org/wiki/Loudspeaker_measurement

you can spend a few weeks on wikipedia trying to get your head around how all that works.
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#13
holy crap, thats alot... its hard to understand. does it effect wattage? i notaced on some bass amps, the higher the ohms the less wattage....?
#14
It will affect wattage. SS amps are very tolerance about using a higher ohm load than specified. If you do, then you will reduce the output wattage. In general with a amp you get the most watts using the lowest ohm load allowed by the manufacturer.

Tube amps are not tolerant and you should use only what the manufacturer says, unless you like to push things and accept the possible consequeneces.
#15
Just to nit pick. With speaker loads the ohm value is not resistance at all, it's impedance. Impedance is the sum of resistance (impedance to DC) and reactance (impedance to AC - which is also dependent on frequency).
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#16
A mismatch isn't necessarily bad. Some amps specify a minimum ohm rating.
For example my sons bass head has one input. It's minimum is 4 ohms. There's a table on the back that shows output at 8 ohms and 16 ohms.

The cabs rating (or combined rating for multiple cabs) can never be lower than the heads, or bad things will happen.

If you mismatch is the other way - cab higher than head, and it's within reason (not a crazy mismatch) ex. a 16 ohm cab into a 8 ohm head, will most likely be ok. What happens in that situation is the amp/cab won't run at peak efficiency - and you'll lose a bit of your max volume. Unless you dime the amp, you probably won't notice.

But if you're unsure, check with the manufacturer.