M
mixsit
Well-known member
Forgot 'shunt.
...going for more rum now.
...going for more rum now.
M
mcmetal
New member
I don't know the technical reasons behind eveything.I just remember that years ago i had a Fender halfstack with a 8 ohm Fender cab.I also had a another cheap SHS cab over at my bass players house that was 4 ohms.I always kept my ohm setting on the amp at 8 ohms to match the Fender cab at home but when i went to his place to jam i would set the amp to 4 ohms to match my SHS cab.
Once i forgot to set my amp to 4 ohms when i was at his place and my amp was starting to cut out and it just wasn't powering the cab properly.I switched it to the 4ohm setting to match the cab and i was fine.We were at a decent volume so maybe the increased volume was putting more demand on the amp.Luckily i didn't damage my head.Like i said i don't know if it was a power thing or a transistor thing or what.All i know is it wasn't working!
Once we got a rehearsal space i used both cabs together.Tha cabs were daisy chained together.I went into my Fender cab then out of the Fender to the SHS.That should've meant i had the cabs running in series which put my total ohms at 12 ohms.I set my ohms on the amp to 8 ohms and it sounded o.k. but it sounded better and more powerful with the amp set to 4 ohms.
Hopefully some of this mumbo jumbo helps the OP.
Once i forgot to set my amp to 4 ohms when i was at his place and my amp was starting to cut out and it just wasn't powering the cab properly.I switched it to the 4ohm setting to match the cab and i was fine.We were at a decent volume so maybe the increased volume was putting more demand on the amp.Luckily i didn't damage my head.Like i said i don't know if it was a power thing or a transistor thing or what.All i know is it wasn't working!
Once we got a rehearsal space i used both cabs together.Tha cabs were daisy chained together.I went into my Fender cab then out of the Fender to the SHS.That should've meant i had the cabs running in series which put my total ohms at 12 ohms.I set my ohms on the amp to 8 ohms and it sounded o.k. but it sounded better and more powerful with the amp set to 4 ohms.
Hopefully some of this mumbo jumbo helps the OP.
Lt. Bob
Spread the Daf!
no, if you daisy chain cabs like that you're running them in parallel. an 8 ohm cab and a 4 ohm can in parallel would give a load of 2.6 ohms? Something like that.
Anyway .... the extra jack in a Fender cab is a parallel jack, not series.
guitaristic
prophet of Dave
Ohms have always blown my mind...idk why, i guess I just suck at comprehending this stuff. 
Although, in my case, it's more having to do with passive speakers/power amps.
Although, in my case, it's more having to do with passive speakers/power amps.
S
stevieb
Just another guy, really.
I got confused like that, once. Wandered into the wrong 'ouse, thought I was 'ohm, but I wasn't.
Lt. Bob
Spread the Daf!
ohms are generally pretty easy.
NOTE ..The following is for explanation and visualization purposes and isn't meant to be a technological primer so I won't try to use exactly the proper terminology. It's just to help non-electronics guys to visualize what's going on:
Parallel means just that ..... all the wires to the speakers simply parallel each other. So if you burn out one speaker .... the others will keep working. Think of it like star grounding. You go from the starting point (the jack) and run two wires to each and every speaker. So each speaker has it's own individual connection to the jack. In practice they usually just run 2 wires from the jack to one speaker and then another two wires from that speaker to the next and so on. But the effect is the same ..... each speaker has its' own path to the jack. So you have a separate circuit for each and every speaker.
And series means just that also. The electricity goes in series from one speaker to the next. If you burn out a speaker ALL of them quit working because the juice goes thru each speaker before continuing to the next and if any part of the circuit is interrupted, the circuit is broken for all. So you have one wire from the jack going to say, the (+) terminal of a speaker, and the juice HAS to go thru that speaker before passing to the next speaker. Then a single wire goes from that speakers' (-) to the (+) of the next speaker and so on.
The other wire from the jack goes to the (-) of the last speaker in the series. So the juice goes thru each and every speaker before returning to the jack making all the voice coils and wires one single circuit.
IF we assume that all the speakers in a cab are the same impedance then calculating the final load is easy as pie.
In parallel circuits you take the impedance of a single speaker and divide it by the number of speakers. So if a cab has four 16ohm speakers, you would take 16ohms ..... divide it by four and you get a final load of 4 ohms.
In series .... you take the impedance of the speakers and add them up. So if you had four 4 ohm speakers in a cab ....... in series that would add up to a final load of 16 ohms.
When there's an extra jack on a cab it's virtually always in parallel so if you have an 8 ohm can and daisy chain a second 8 ohm cab, you have a parallel circuit with two 8 ohm elements so 8 ohms divided by two equals a total load of 4 ohms.
When speakers aren't the same impedance it gets more complicated. Well, not in series. If you take an 8 ohm and 4 ohm speaker in series you still add them up so you'd have a 12 ohm total.
But if you take an 8ohm can and a 4 ohm can in parallel, as in the example mcmetal gave above, you end up with a 2.6 ohm load or thereabouts.
warning ..... math ahead
To figure out the load of mismatched impedances in parallel you that the inverse of the loads ... add them and divide the fraction.
So an 8 ohm load and a 4 ohm load would be 1/8 plus 1/4 which equals 3/8 and then 8 divided by 3 is 2.66 final load.
Lastly ...... some cabs use a series/parallel wiring.
So lets say we have a cab with four 8ohm speakers in it and we want to end up with a final load of 8 ohms. Neither way of wiring can do that so we use a combination of the two. You take 2 speakers in the cab and wire them in series with each other giving a load of 16 ohms. And you'd do the same with the other two speakers. Now you have two sets of speaker/circuits in the same cab, each having a total of 16 ohms. You treat those as separate circuits and run those two circuits in parallel with each other. Two 16 ohm speaker/circuits in parallel gives a final load of 8 ohms.
NOTE ..The following is for explanation and visualization purposes and isn't meant to be a technological primer so I won't try to use exactly the proper terminology. It's just to help non-electronics guys to visualize what's going on:
Parallel means just that ..... all the wires to the speakers simply parallel each other. So if you burn out one speaker .... the others will keep working. Think of it like star grounding. You go from the starting point (the jack) and run two wires to each and every speaker. So each speaker has it's own individual connection to the jack. In practice they usually just run 2 wires from the jack to one speaker and then another two wires from that speaker to the next and so on. But the effect is the same ..... each speaker has its' own path to the jack. So you have a separate circuit for each and every speaker.
And series means just that also. The electricity goes in series from one speaker to the next. If you burn out a speaker ALL of them quit working because the juice goes thru each speaker before continuing to the next and if any part of the circuit is interrupted, the circuit is broken for all. So you have one wire from the jack going to say, the (+) terminal of a speaker, and the juice HAS to go thru that speaker before passing to the next speaker. Then a single wire goes from that speakers' (-) to the (+) of the next speaker and so on.
The other wire from the jack goes to the (-) of the last speaker in the series. So the juice goes thru each and every speaker before returning to the jack making all the voice coils and wires one single circuit.
IF we assume that all the speakers in a cab are the same impedance then calculating the final load is easy as pie.
In parallel circuits you take the impedance of a single speaker and divide it by the number of speakers. So if a cab has four 16ohm speakers, you would take 16ohms ..... divide it by four and you get a final load of 4 ohms.
In series .... you take the impedance of the speakers and add them up. So if you had four 4 ohm speakers in a cab ....... in series that would add up to a final load of 16 ohms.
When there's an extra jack on a cab it's virtually always in parallel so if you have an 8 ohm can and daisy chain a second 8 ohm cab, you have a parallel circuit with two 8 ohm elements so 8 ohms divided by two equals a total load of 4 ohms.
When speakers aren't the same impedance it gets more complicated. Well, not in series. If you take an 8 ohm and 4 ohm speaker in series you still add them up so you'd have a 12 ohm total.
But if you take an 8ohm can and a 4 ohm can in parallel, as in the example mcmetal gave above, you end up with a 2.6 ohm load or thereabouts.
warning ..... math ahead
To figure out the load of mismatched impedances in parallel you that the inverse of the loads ... add them and divide the fraction.
So an 8 ohm load and a 4 ohm load would be 1/8 plus 1/4 which equals 3/8 and then 8 divided by 3 is 2.66 final load.
Lastly ...... some cabs use a series/parallel wiring.
So lets say we have a cab with four 8ohm speakers in it and we want to end up with a final load of 8 ohms. Neither way of wiring can do that so we use a combination of the two. You take 2 speakers in the cab and wire them in series with each other giving a load of 16 ohms. And you'd do the same with the other two speakers. Now you have two sets of speaker/circuits in the same cab, each having a total of 16 ohms. You treat those as separate circuits and run those two circuits in parallel with each other. Two 16 ohm speaker/circuits in parallel gives a final load of 8 ohms.
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M
moresound
Loud Sun Studios
T
theD1CKENS
*insert clever title here
Fixed that for ya.
Thanks
Bob, thanks for dumbing it down for me. Bookmarked. Don't have to worry about any of that stuff right now, with being able to match it all up, but I have another head that may give me trouble, if I ever go back to solid state
snow lizard
Dedicated Slacker
"Resistance is futile"
- The Borg
Amplifiers are governed by the speaker load. Zero resistance (ohms) equals no government. Anarchy. Your amp will try to output enough power to achieve arc welding. A good arc welder will probably have some kind of thermal relay that shuts pretty much everything except the fan off when it exceeds its duty cycle. Once the temperatures fall to something in the normal range the welding machine will work again. I'm not sure if guitar amps work in the same way. A lot of them might simply fry themselves. Not a lot of amps can handle a 2 ohm load for this reason. Works the amp harder than it was designed for.
Bass amps are sometimes rated differently for power output depending on speaker load. Might say something like 260 watts at 8 ohms, 400 watts at 4 ohms. It doesn't change the way the amp does anything, it just means less speaker resistance is louder.
As for a 5 watt amp feeding a 200 watt cab, generally not a problem. For something like a home stereo setup, this could be more of a problem. The 5 watt amp is likely to distort if pushed to the rails. A badly distorting amp could cause the voice coils to rub. This could ruin the speaker whereas an amp pushing more power will get louder and stay clean. No rub. Speakers can handle the power. Everything's fine.
This could get more interesting going the other way. A 2,000 watt PA amp feeding a 5 watt speaker, let's say. More power is more likely to create more "speaker excursion". For the sake of experimentation, try to get yourself a Ludwig Black Beauty snare drum. Put fresh heads on it. Coated Ambassador batter head and a Hazy Ambassador snare side would be a good combination. The drum should be able to produce wonderful tone with this setup even when tuned fairly low. The batter head is more likely to have a short lifespan tuned low, but it should sound something like a freaking cannon if you hit it hard enough.
One hit is all you need for the experiment.
What we're trying to achieve here is maximum speaker excursion by increasing the power output of the amp and decreasing the power handling capability of the speaker. So if this speaker is normally able to travel 1/8 inches or so, perhaps we can get it to travel several feet in this way. With an array of these things you might be able to have speaker cone races.
Going back to the guitar amp idea, 5 watts feeding a 200 watt cab isn't so much of a problem in terms of damaging anything. Everything should work. Thing is, the speakers might not become "involved" as much as they're capable. Something like a 25 watt Celestion hooked up to the Valve Jr. would be a different story. The 200 watt cab would probably be a lot cleaner whereas the 25 watt cab would be more eager to distort if that's the sort of thing you're going for.
- The Borg
Amplifiers are governed by the speaker load. Zero resistance (ohms) equals no government. Anarchy. Your amp will try to output enough power to achieve arc welding. A good arc welder will probably have some kind of thermal relay that shuts pretty much everything except the fan off when it exceeds its duty cycle. Once the temperatures fall to something in the normal range the welding machine will work again. I'm not sure if guitar amps work in the same way. A lot of them might simply fry themselves. Not a lot of amps can handle a 2 ohm load for this reason. Works the amp harder than it was designed for.
Bass amps are sometimes rated differently for power output depending on speaker load. Might say something like 260 watts at 8 ohms, 400 watts at 4 ohms. It doesn't change the way the amp does anything, it just means less speaker resistance is louder.
As for a 5 watt amp feeding a 200 watt cab, generally not a problem. For something like a home stereo setup, this could be more of a problem. The 5 watt amp is likely to distort if pushed to the rails. A badly distorting amp could cause the voice coils to rub. This could ruin the speaker whereas an amp pushing more power will get louder and stay clean. No rub. Speakers can handle the power. Everything's fine.
This could get more interesting going the other way. A 2,000 watt PA amp feeding a 5 watt speaker, let's say. More power is more likely to create more "speaker excursion". For the sake of experimentation, try to get yourself a Ludwig Black Beauty snare drum. Put fresh heads on it. Coated Ambassador batter head and a Hazy Ambassador snare side would be a good combination. The drum should be able to produce wonderful tone with this setup even when tuned fairly low. The batter head is more likely to have a short lifespan tuned low, but it should sound something like a freaking cannon if you hit it hard enough.
One hit is all you need for the experiment.
What we're trying to achieve here is maximum speaker excursion by increasing the power output of the amp and decreasing the power handling capability of the speaker. So if this speaker is normally able to travel 1/8 inches or so, perhaps we can get it to travel several feet in this way. With an array of these things you might be able to have speaker cone races.
Going back to the guitar amp idea, 5 watts feeding a 200 watt cab isn't so much of a problem in terms of damaging anything. Everything should work. Thing is, the speakers might not become "involved" as much as they're capable. Something like a 25 watt Celestion hooked up to the Valve Jr. would be a different story. The 200 watt cab would probably be a lot cleaner whereas the 25 watt cab would be more eager to distort if that's the sort of thing you're going for.
bouldersoundguy
Well-known member
To clarify, when talking about speakers the term is impedance, not resistance. Resistance if for DC and impedance is for AC.
Lt. Bob
Spread the Daf!
no they don't work the same since it's not just temperature related. But many amps now do have protection circuitry to keep them from being damaged in these situations.
ALL amps do this ..... not just bass amps .... all amps ... hi-fi ... guitar ....... whatever.
no ...... if an amp's clipping (not just distorting), it's a very high energy output. High enough to burn out a voice coil. Especially tweeters since they have lighter wire and are easier to burn out. It has absolutely nothing at all to do with making the voice coil 'rub'. Rubbing voice coils are usually caused by excessive excursion which can make the voice coil 'bottom out', thus crumpling it and making it rub. Or conceivably if it goes far enough forward it can damage the area where it's glued to the cone and thus becomes misalighned.
But low powered amps distorting do not cause voice coils to rub. And a 5 watt guitar amp into a 200 watt guitar cab isn't gonna hurt it no matter how high you run it since running guitar amps flat out is often a part of the desired sound. It's usually highly compressed and guitar speakers are meant to handle that sort of distortion. Where this can be a factor is driving solid state amps into studio monitors or running an underpowered PA amp into PA speakers ..... the parts of those speakers most at risk would be the horns/tweeters although the woofer could be damaged also.
more power does cause greater excursion .... no 'likely' about it. But a 2000 watt amp into a 5 watt speaker will pretty much burn out the voice coil as soon as you hit it with any significant signal.
not sure how this has anything to do with impedance of speakers.
yes, guitar speakers add to the sound and many people feel that it's best to have one that's rated somewhere around the same as the power that it gets hit with so it'll be in its' sweet spot.
Others prefer to have a lotta headroom.
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snow lizard
Dedicated Slacker
Lt. Bob said:
That would be disappointing. My idea is to hit the thing with enough power and a fast enough transient to physically launch the cone across the room. How fast does copper melt?
Lt. Bob said:
It has nothing to do with impedance of speakers. I was talking about destroying speakers. With style.
Lt. Bob
Spread the Daf!
cavedog101
Well-known member
Good explain'n Bob.
One thing I'll add. When using unmatched impedance cabinets....even though there will be a combined value for them together, the cabinet with the lowest initial impedance will get most of the action. Electricity, no matter what its form, will seek the path of least resistance every time.
One thing I'll add. When using unmatched impedance cabinets....even though there will be a combined value for them together, the cabinet with the lowest initial impedance will get most of the action. Electricity, no matter what its form, will seek the path of least resistance every time.
Lt. Bob
Spread the Daf!
YES!! ..... this is an important factor that people will overlook.
Let's say you decide to use two mismatched speakers in a 2X12 cab, one at 4 ohms and the other at 8ohms. BOTH of them are rated for the same power. The one with the lower impedence will get significantly more power so you end up mostly hearing it. Also, in a bass rig what can happen is you keep turning it up because you don't feel like you're getting two speakers worth of volume, and so you can end up overdriving the louder of the two speakers and even possibly damage it because you're trying to get that other speaker up in volume.
T
theD1CKENS
*insert clever title here
that's a scary thought. I'm going to assume that, since the speakers in my cab are stock from the factory, they would all take the same load
...but then there's a stereo input(@16 ohms, I think) which makes me wonder
also, this is a hella useful thread. I'm really considering trying to launch a speaker across the yard, now
bouldersoundguy
Well-known member
If you change "are rated for the same power" to "have the same sensitivity" I'll agree. Power ratings alone don't really say how loud a speaker gets.
Lt. Bob
Spread the Daf!
well ..... true enough ..... I was trying to stay simple but hell ...... let's go ahead and get into it.
Boulder makes another very important point. Speakers can have dramatically different sensitivities; putting out more or less volume with the same amount of power. If one speaker is 10db louder at the same wattage ... it'll have double the perceived volume.
So if one speaker is 10db more efficient it'll be perceived as twice as loud. In the example we're talking about ..... if the 8ohm speaker is also 10db louder for the same input. ..... even though it's not drawing as much power it may well sound as loud or louder than the 4 ohm speaker. And actually, the two speakers can interact too, affecting each others' response curve.
So both sensitivity and impedence are important when mixing and matching speakers.
Personally, when using multiple drivers I prefer to have everything match but there does seem to be a group of amp builders who like to use mismatched speakers to get the tone of each.