Difference between Ohms?

[Oceano]

Could somebody please explain to me the difference between 4Ohms, 8Ohms, and 16Ohms when it comes to speakers in a cab and amp heads? I've never had a "real" amp so I have no idea what any of that stuff means in reference to musical equipment.

Thanks

 

[FuseG4]

Re: Difference between Ohms?

The oms is the electrical resistance the speaker presents to the amplifier. with no resistance or "impedance" the amp works too hard and stuff breaks. Matching impedance is important to the life of the amp.

An amp with a 16 ohm out wants to see 16 ohms. If you feed it 8, you run the risk of damaging your amp.

With tube amps, it seems to be OK to say, us an amp with an 8 ohm out into a 16 ohm speaker load. it just reduces the power of the amp and may not sound great in all cases.

Someone in here will chime in with the technical aspects of this stuff but the above is the more important stuff.

 

[Oceano]

Re: Difference between Ohms?

The oms is the electrical resistance the speaker presents to the amplifier. with no resistance or "impedance" the amp works too hard and stuff breaks. Matching impedance is important to the life of the amp.

An amp with a 16 ohm out wants to see 16 ohms. If you feed it 8, you run the risk of damaging your amp.

With tube amps, it seems to be OK to say, us an amp with an 8 ohm out into a 16 ohm speaker load. it just reduces the power of the amp and may not sound great in all cases.

Someone in here will chime in with the technical aspects of this stuff but the above is the more important stuff.

So the bigger the number the less power the amp is using? What about amps that have a switch on the back? does that affect the tone?

 

[woemoejack]

Re: Difference between Ohms?

yes, basically what Fuse said. always try to match the ohms between the amp and cab. there shouldnt be any tone difference when using a different ohm output on the amp. if you have to be mismatched, always have the smaller number on the amp side. NEVER run a 8 ohm amp into anything less than 8 ohm cab. you could damage your output transformer and power tubes. I think I am correct for the most part, the amp gurus should be by shortly to clean up my mess if not...

 

[FuseG4]

Re: Difference between Ohms?

If I set my amp to 8 ohms and play into my 16ohm greenback, it definitely sounds more muffled. It's not a setting i'd ever use.

 

[woemoejack]

Re: Difference between Ohms?

If I set my amp to 8 ohms and play into my 16ohm greenback, it definitely sounds more muffled. It's not a setting i'd ever use.

Yeah, what I meant was that using the 16 ohm output into a 16 ohm cab wouldnt sound different than matching the 8 ohm output to an 8 ohm cab. I agree that mismatching ohm loads will affect tone, I just cant exlain it in the mechanical sense.

 

[crguti]

Re: Difference between Ohms?

Two or more speakers in a cabinet may be wired in parallel (lowering the impedance) or in series (increasing the impedance). If you use parallel conection you use large impedance speakers. If you use series connection you use low impedance speakers.
So, that's why you have differents impedances.

 

[Baltar]

Re: Difference between Ohms?

on ac devices such as speakers, there is a difference between resistance 'r' (dc) and
impedance 'z' (ac). a speaker has a different z at every freuqency, which is again
different to it's dc resistance. the 4,8,16 ohm readings are more or less an averaged z.
solid state amps do offer more power on lower- z speakers, but you must'nt get below
der specifications, otherwise they die very fast. tube amps are designed for a specific
load, which you shouldn't mismatch in any direction too much. That's why they often
provide several jacks or a selector switch.
there are a several reason's why '''different ohms sound different'''. eg the damping
factor of amps changes with the impedance. if you compare a speaker model, which is
produced in two different z ratings, you will notice in it's specs, that also the inductance
changes, the T changes and therefor it's tonal reproduction ... etc.
if you are wiring speakers in series, you can add their impedance. if you switch them
in parallel, you can calc it that way (embed wiki pic, hope that's ok) ..

cheers, B

 

[Oceano]

Re: Difference between Ohms?

Two or more speakers in a cabinet may be wired in parallel (lowering the impedance) or in series (increasing the impedance). If you use parallel conection you use large impedance speakers. If you use series connection you use low impedance speakers.
So, that's why you have differents impedances.

Is there a difference in tone between running them in parallel or in series?

 

[Oceano]

Re: Difference between Ohms?

on ac devices such as speakers, there is a difference between resistance 'r' (dc) and
impedance 'z' (ac). a speaker has a different z at every freuqency, which is again
different to it's dc resistance. the 4,8,16 ohm readings are more or less an averaged z.
solid state amps do offer more power on lower- z speakers, but you must'nt get below
der specifications, otherwise they die very fast. tube amps are designed for a specific
load, which you shouldn't mismatch in any direction too much. That's why they often
provide several jacks or a selector switch.
there are a several reason's why '''different ohms sound different'''. eg the damping
factor of amps changes with the impedance. if you compare a speaker model, which is
produced in two different z ratings, you will notice in it's specs, that also the inductance
changes, the T changes and therefor it's tonal reproduction ... etc.
if you are wiring speakers in series, you can add their impedance. if you switch them
in parallel, you can calc it that way (embed wiki pic, hope that's ok) ..

cheers, B

I can't read the equation too well, but I think I get it. If you run 2 8Ohm speakers in series their combined impedance would be 16Ohm, but If you ran them parallel they would be 4Ohms. Is that right?

Also, are you saying that if you bought two of the same model speaker at two different Impedance they would sound different from each other on their own?

 

[crguti]

Re: Difference between Ohms?

Is there a difference in tone between running them in parallel or in series?

There is something called the effect of "back emf" that is generated by the other speaker. In series connection, the movement of one cone can generate a voltage that affects the other speaker, whereas in parallel connection each speaker is connected to the same amp output terminals (same voltage) and is therefore only at the mercy of its damping factor. So, yes there will be a difference in tone. IMO, it will be noticed only if you play very loud.

 

[Oceano]

Re: Difference between Ohms?

There is something called the effect of "back emf" that is generated by the other speaker. In series connection, the movement of one cone can generate a voltage that affects the other speaker, whereas in parallel connection each speaker is connected to the same amp output terminals (same voltage) and is therefore only at the mercy of its damping factor. So, yes there will be a difference in tone. IMO, it will be noticed only if you play very loud.

So parallel is better if you play loud, right? That means that the speaker voltage effect thing is bad? Sorry if that's a stupid question lol.

 

[crguti]

Re: Difference between Ohms?

So parallel is better if you play loud, right? That means that the speaker voltage effect thing is bad? Sorry if that's a stupid question lol.

In hi-fi speaker/cabinet design is usually used the parallel connection. Guitar speaker/cab is another story, specially when you use a tube amp.
Some people likes to connect their speakers in series to smooth out the response. Choose what it sounds better for you.

 

[Baltar]

Re: Difference between Ohms?

I can't read the equation too well

ok, so they block unwanted linking. if you right click on it, and choos view image, you should be able to see it (at least when using firefox)

If you run 2 8Ohm speakers in series their combined impedance would be 16Ohm, but If you ran them parallel they would be 4Ohms. Is that right?

yes

Also, are you saying that if you bought two of the same model speaker at two different Impedance they would sound different from each other on their own?

yeah, there is a slight difference. but you normally don't need to worry about it

Choose what it sounds better for you.

amen

 

[Chickenwings]

Re: Difference between Ohms?

In most cases the default standard for guitar speakers in 8ohms. And the most common wirings for speaker boxes is this:
1 speaker = 8
2 speakers = 4ohms (2x8 ohm speakers in parallel)
4 speakers = 8 ohms (series/parallel) - which is like two paris of series speakers, wired in parallel. 1 pair=16 wired with another pair in parallel gives you 8 ohms.
8 speakers usually means 2 quad boxes. Your amp will be wired to plug the cabs in separately, so some run two 8 ohm quads in parallel at 4 ohms total, and some run two cabs in series at 16.
Many bass cabinets run at 4 ohms, but that is bass amps....
There are exceptions, but the above are the most common wirings/impedances.
your amp should have the recommended impedance written on the back next to the speaker jacks.

 

[Oceano]

Re: Difference between Ohms?

In most cases the default standard for guitar speakers in 8ohms. And the most common wirings for speaker boxes is this:
1 speaker = 8
2 speakers = 4ohms (2x8 ohm speakers in parallel)
4 speakers = 8 ohms (series/parallel) - which is like two paris of series speakers, wired in parallel. 1 pair=16 wired with another pair in parallel gives you 8 ohms.
8 speakers usually means 2 quad boxes. Your amp will be wired to plug the cabs in separately, so some run two 8 ohm quads in parallel at 4 ohms total, and some run two cabs in series at 16.
Many bass cabinets run at 4 ohms, but that is bass amps....
There are exceptions, but the above are the most common wirings/impedances.
your amp should have the recommended impedance written on the back next to the speaker jacks.

Thanks. Now I know if I buy a speaker and don't know what amp it will got to necessarily, I should be fine getting an 8 ohm one.