# 4 or 16 ohms....which is better?



## GTmaker (Apr 24, 2006)

HI Folks
I'm going to rewire a 2 speaker cabinet I have.
Both speakers are 8 ohms.... so I can go parallel 4 ohms or series 16 ohms.

My amp has 4 , 8 , 16 ohm outputs.

Are there any advantages to the speakers going 4 or 16 ..?
Does the amp prefer 4 or 16 to run more efficiently?

Any insight on this matter would be appreciated.

G.


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## jb welder (Sep 14, 2010)

The amp will run the same if the cab is connected to the correct output.
There should not be any advantage or disadvantage to either impedance.
However, in the future, if you want to use it along with another cab, 16 is probably the better option. If it's 4 ohms and used in combination with another cab, the impedance of the combination will be less than 4 ohms. Most amps don't want that.


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## Guest (Jul 3, 2015)

maybe put a switch on the cab as well?
flip from 4 to 16 when necessary.


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## Budda (May 29, 2007)

If your cab is wired to 4 ohms, then I *think* any head should be a safe mismatch for it. I COULD BE WRONG!

I'm rewiring my new cab today from 16 to 4 because my head can't run 16.


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## Guest (Jul 3, 2015)

sorry to go off on a tangent here.
I'm picking up a 412 cab tomorrow to pair up 
with my traynor 1/4 horse. here's my question.
I've read somewhere that 'lamp wire' can be used
as an alternative to speaker cable. I'd like to have a 
few feet extra to connect my amp to the cab. thoughts?


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## mhammer (Nov 30, 2007)

Sure. 16-gauge "zip cord" is fine. I suppose the "magical" properties of cable materials start to emerge, the longer the cable. But if it's only going from the input jack in the cab, to the speakers, that 18" won't change very much, as long as it's a nice thick wire.

Keep in mind that the wire's electrical resistance is a function of both thickness, and distance. So, if an amp head expects to see 4 ohms at the cab, and the wire between the head and cab is long enough to add another 3 ohms, the amp is not seeing 4 ohms. Keep 'em thick and short, and you'll be fine.


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## bluzfish (Mar 12, 2011)

Mark is correct here. However, you always have to be careful of running the cable too close to a powerful source of noise potential such as in hamstrung's oscillating body as indicated in the picture you posted.


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## keto (May 23, 2006)

Budda said:


> If your cab is wired to 4 ohms, then I *think* any head should be a safe mismatch for it. I COULD BE WRONG!
> 
> I'm rewiring my new cab today from 16 to 4 because my head can't run 16.


It's a generalization, but you have it backwards methinks. I always think of it as 'head goes into' as a math problem. 4 (or 8. Anways, the head) 'goes into' 16 (or 8) but not vice versa - a 16 ohm head doesnt want to see an 8 or 4 ohm cab.

So, I think you're better off at 16 if it's an 8 ohm head, but if it's a 4 ohm head then yeah you want to wire it up for 4 for max efficiency/best match.


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## WCGill (Mar 27, 2009)

keto said:


> It's a generalization, but you have it backwards methinks. I always think of it as 'head goes into' as a math problem. 4 (or 8. Anways, the head) 'goes into' 16 (or 8) but not vice versa - a 16 ohm head doesnt want to see an 8 or 4 ohm cab.
> 
> So, I think you're better off at 16 if it's an 8 ohm head, but if it's a 4 ohm head then yeah you want to wire it up for 4 for max efficiency/best match.


Gosh we've been through this so much. A 100% mismatch isn't a big deal for a tube amp. Generally, a lower load is better for an amp if there must be a mismatch. IE, 4 ohm cab into the 8 ohm output, or 8 ohm cab into the 16 ohm output.


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## hollowbody (Jan 15, 2008)

I would wire it 16 ohms, because then you could always add another 16 ohm cab in parallel and get an 8 ohm load. You can't add a 4 ohm cab in parallel because 2 ohm is waaaay to low for anything other than a Super Reverb or Bassman.


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## greco (Jul 15, 2007)

laristotle said:


> sorry to go off on a tangent here.
> I'm picking up a 412 cab tomorrow to pair up
> with my traynor 1/4 horse. here's my question.
> I've read somewhere that 'lamp wire' can be used
> ...


@laristotle,

I have a very nice speaker cable that I made with Neutrik plugs. IIRC it is about 10 feet long and is either 14 or 16 gauge "proper" speaker wire with twisted pair wires. I was doing a stereo cab thing at home for fun and made some long speaker cables to do this. I can make it shorter for you (or not) and it is a gift. 

Let me know. 

BTW...Is this the 412 cab you were playing through at Gerry's Jam? Sweet cab!...sounded huge. Where is it from...it just seemed to appear of of the blue and I never asked you about it.

@G...Sorry about the slight derail of your thread. However, you have a lot of informative comments/responses.

Cheers

Dave


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## nonreverb (Sep 19, 2006)

As stated there's no difference if the output transformer is matched to the speaker impedance. Where 16 ohms has an advantage is where you're running a long cable. As Mhammer points out, the longer the speaker cable, the more impedance is inserted into the circuit. The remedy for that in the past was to set up amps to run 16 ohm.
Adding 2 ohms to a 16 ohm circuit creates 12.5% mismatch at the amp.....adding 2 ohms to a 4 ohm system adds 50% mismatch....not good.


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## Budda (May 29, 2007)

keto said:


> It's a generalization, but you have it backwards methinks. I always think of it as 'head goes into' as a math problem. 4 (or 8. Anways, the head) 'goes into' 16 (or 8) but not vice versa - a 16 ohm head doesnt want to see an 8 or 4 ohm cab.
> 
> So, I think you're better off at 16 if it's an 8 ohm head, but if it's a 4 ohm head then yeah you want to wire it up for 4 for max efficiency/best match.


I need maximum efficiency in this scenario though.


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## greco (Jul 15, 2007)

nonreverb said:


> Adding 2 ohms to a 16 ohm circuit creates 12.5% mismatch at the amp.....adding 2 ohms to a 4 ohm system adds 50% mismatch....not good.


Please don't think I am arguing with you. I just need to better understand this concept.

All this time, I thought/understood that 100% mismatch was "OK" 
100%, to me, was going from 4 ohms to 8 ohms, 8 to 16 (and reverse of this) 
4 to 16 (and reverse) is more than 100% and not acceptable/advised.

Now I am totally lost and confused by what you are saying.

Could you please help me by explaining this in more detail.

Thanks

Dave


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## nonreverb (Sep 19, 2006)

Ok....here's the general rule regarding amps and loads....this is the simple explanation. 

Tube power amp: You generally DO NOT want to plug a higher impedance speaker into what the amp is rated for. Too high an impedance and the flyback voltage can blow a hole in the winding....good bye to the output transformer. Too low isn't ideal either but it's stressing the tubes more than anything.

Solid state amp: Current output is proportional. If it wants to see 8 ohms, anything 8 ohms or more will not affect it whatsoever except that the power will diminish based on how high the impedance. Go beyond it's minimum rating and all bets are off. Either the thermal shutdown will kick in or you'll blow the output transistors as they're trying to sync to much current and overheat.






greco said:


> Please don't think I am arguing with you. I just need to better understand this concept.
> 
> All this time, I thought/understood that 100% mismatch was "OK"
> 100%, to me, was going from 4 ohms to 8 ohms, 8 to 16 (and reverse of this)
> ...


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## Guest (Jul 4, 2015)

greco said:


> BTW...Is this the 412 cab you were playing through at Gerry's Jam? Sweet cab!...sounded huge. Where is it from...it just seemed to appear of of the blue and I never asked you about it
> 
> Cheers
> 
> Dave


Yes it is. I'll ask Gerry about it's provenance.
And yes, I'd like to take you up on your speaker cable offer.
Will pm.


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## jb welder (Sep 14, 2010)

WCGill said:


> A 100% mismatch isn't a big deal for a tube amp. Generally, a lower load is better for an amp if there must be a mismatch. IE, 4 ohm cab into the 8 ohm output, or 8 ohm cab into the 16 ohm output.


I see you are speaking specifically of tube amps, but I don't think the OP said whether it's tube or SS. For a Solid state amp, *NEVER *go below the minimum load spec.




greco said:


> Please don't think I am arguing with you. I just need to better understand this concept.


Dave, I'm not sure which part on nonreverbs post you don't follow, but he was talking about the added series resistance a long cable can add to the load impedance. (ex. a long cable that adds 2ohms to a 16ohm load is an _extra_ 12.5% mismatch, that same cable adds much more % mismatch if the load is only 4ohms)


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## greco (Jul 15, 2007)

jb welder said:


> Dave, I'm not sure which part on nonreverbs post you don't follow, but *he was talking about the added series resistance a long cable can add to the load impedance. (ex. a long cable that adds 2ohms to a 16ohm load is an extra 12.5% mismatch*, that same cable adds much more % mismatch if the load is only 4ohms)


ZOOOOM...right over my aging, bald head!!!!...LOL :sSig_DOH::sEm_oops:

I get it all now...Thanks! 

Makes total sense.

*Just to add something constructive and of possible interest to his thread (after my royal screw up), I measured my 10.5 foot speaker cable (14 gauge wire) and it is .6 ohms. *

Cheers

Dave


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## GTmaker (Apr 24, 2006)

greco said:


> ZOOOOM...right over my aging, bald head!!!!...LOL :sSig_DOH::sEm_oops:
> 
> I get it all now...Thanks!
> Makes total sense.
> ...


Have another burger Dave and you'll feel better in the morning...
G.

can some one please comment on the speaker side of things...
Is there an efficiency thing happening ( sounds better) at either 4 ohms or 16 ohms for (2) 8 ohm speakers?


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## notjoeaverage (Oct 6, 2008)

In the documentation for my Lil' Night Train 2W head it states using a 16 ohm cab it has 2w output, but an 8 ohm cab output drops to 1.5W.

I also remember seeing a device that is used in place of an attenuator to lower output/volume by changing from the ohms you run at. I think it was on the Phaez website.

Found it

http://www.phaezamp.com/ampshop/en/21-brink-4-8

http://www.phaezamp.com/ampshop/en/15-brink-79


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## GTmaker (Apr 24, 2006)

notjoeaverage said:


> In the documentation for my Lil' Night Train 2W head it states using a 16 ohm cab it has 2w output, but an 8 ohm cab output drops to 1.5W.
> I also remember seeing a device that is used in place of an attenuator to lower output/volume by changing from the ohms you run at. I think it was on the Phaez website.
> Found it
> http://www.phaezamp.com/ampshop/en/21-brink-4-8
> http://www.phaezamp.com/ampshop/en/15-brink-79


thanks for the reply and information..
below is a typical PA power amp chart..

2ohms
2750W 
 4ohms
3000W 
8ohms
1800W 
4ohms; Bridge
5500W
8ohms; Bridge
6000W




my question is ...
Why is it that we never talk about guitar amps 
with regards to the power that they put out in relation to the ohms of the speakers attached?

G.


 


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## greco (Jul 15, 2007)

GTmaker said:


> my question is ...
> Why is it that we never talk about guitar amps
> with regards to the *power* *that they put out* in relation to the ohms of the speakers attached?
> 
> G.


Do you equate "power" with "volume/*loudness*"? 

Just want to clarify.

This might interest you (from another forum):

There is no direct relation between impedance and *loudness*. Nor is there a standard for control settings. you can line up a row of 50 watt amplifiers and set all of their volume controls to 5, and they will not all play at the same loudness. SO saying something like "A 50 watt amplifier at 4 Ohms with a 4 Ohm speaker and the volume set at 5 is louder than a 50 watt amplifier at 8 Ohms with a 8 Ohm speaker and the volume set at 5 is." is not true, and is really not very meaningful.

*Tube amps and solid state amps do behave differently. *Tube amps come with specified output impedances, and you need to match the speaker impedance to that for most efficient power transfer. So a 50 watt tube amp sits there , and a 4 ohm speaker connected to its 4 ohm output would sound exactly the same as an 8 ohm speaker connected to its 8 ohm output. ASSUMING the two speakers were otherwise identical. Of course that identical-ness never happens in real life.

Solid state amps put the most power into the lowest impedance. SO again ASSUMING the speakers are otherwise identical, an 8 ohm speaker will draw 1/2 the power from an amp as a 4 ohm speaker. This does NOT result in half as loud, it only results in a *small 3db drop in volume*.

You cannot ignore the preamp in all this. SOme amplifiers have more sensitive preamps than others. That means that one amp can be louder at 4 than another amp is at 6. And in fact a 30 watt amp can be louder at 4 than a 60 watt amp at 6. The difference shows up when both amps are maxed, then the 60 watt amp would be 3db louder than the 30 watt amp, ASSUMING all else is the same.

G..... Sorry, but I'm really not following what you are driving at here...I'm getting lost with "power", "efficiency', "sounds better", etc.

Cheers

Dave


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## GTmaker (Apr 24, 2006)

LEt me explain it this way Dave...

There is a reason some folks buy 5 watt amps and some folks prefer 100 watt amps..just trying to point out that power (watts) does matter.
Im not talking volume but straight power output.

HEre is my observation and question.... with everything I have read so far ..
my tube amp has 4 ohm, 8 ohm and 16 ohm outputs...
As it stands now, I do believe that each of those outputs will have different watt ratings assuming all else is equal.
to be even more specific .... 2 X 8 ohms speakers connected in parallel to the 4 ohm output will have a different watts output from the amp
compared to the same 2 speakers connected in series to the 16 ohm output of the same amp.
First of all I have no idea what the actual watts outputs are in my example ( that's why I'm asking the question )
and second, I do believe that a 40 watt output is different then a 20 watt output from an amp.

G.


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## bluzfish (Mar 12, 2011)

greco said:


> Do you equate "power" with "volume/*loudness*"?
> 
> Just want to clarify.
> 
> ...


Actually, the bolded section explains everything quite nicely.The tubes on one side of the output transformer always see the same load provided the correct speaker load is connected to the correct transformer tap on the other side of the transformer. In a SS amp, the output transistors will produce more power with less resistance as long as the load is within the range they are designed for.

In both cases, the total number of speakers with the same resistance and load will receive the same total power but each speaker will receive a share of the total power divided by how many speakers are attached. More speakers will sound louder though by virtue of the increased cone area moving more air, not due to an increase in power. All speakers in the system must be of identical specs for this to be true though.

So for the question of whether it's better to use a cabinet or combination of cabinets with a 16 ohm load or one with a 4 ohm load, the answer is that a tube amp doesn't care as long as the correct output transformer tap is used on the speaker side. That's because the amp only sees it's side of the output transformer which totally isolates it from the actual speaker load.


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## High/Deaf (Aug 19, 2009)

I'll come at it from another way.

Speakers, by nature, are low impedance. They want to see a fairly low voltage to absorb the correct power. A 20V signal across an 8 ohm speaker will produce 50W at the speaker (Vsquared/R; 20*20/8 = 50) and the speaker would see 2.5A through it (V/R; 20/8 = 2.5). So 20V and 2.5A is a nice output for a speaker to see.

Transistor amps, by nature work this way. They can produce 20, 30, even 40V (and 2, 3, 5A) at their output so they do not need an interface (transformer) between them and the speaker. Because of this DIRECT connection with no OP transformer, the amp always produces the same voltage at the output. So that 20V amp would produce 50W across an 8 ohm speaker. If you connected a 16 ohm speaker, half the current would be drawn (20/16 instead of 20/8) and half the power would be produced. If you put a 4 ohm speaker across, the current would be double to 5A and the power would be doubled. IF the power transformer can produce enough current to the output transistors and the output transistors can supply enough current to the speaker without burning up. That's why you can keep lowering the load impedance of a transistor amp and get more power, to the point it will fail or thermally shut down. The minimum impedance on the amp specifies that point. (You can run a lower impedance than advised, as long as you don't run it too hard. You have to stay within the current limitations of the power supply and output devices of the amp).

Tube amps to do not work like this. Tube amps are, by nature, high voltage low current devices. If someone made a few hundred ohm speaker, that could perhaps be hooked directly to a tube amp. But with low impedance, high current speakers, we need to transform the output of tube amp from highV/lowI to lowV/highI. That's what the op transformer does. 

Now unlike a direct transistor output, where the voltage is always the same and the speaker will be louder as you lower the impedance and draw more current. Tube amps have impedance taps that vary the voltage / current ratio to match the different loads. So all things ideal (in a mathematical world), the 8 ohm tap would be producing 20V to give you 50W across that 8 ohms. The 16 ohm tap would be producing a higher voltage that across a 16 ohm speaker would still produce 50 W (Your homework is to do the math, I think its the root of P/R = V). The 4 ohm output would produce a lower voltage that across a 4 ohm speaker would still produce 50 W. 

Because tube amps are high voltage, a mismatch (especially too high an impedance, approaching an approaching an open circuit) can cause very high voltage swings and back-eddies because the tubes aren't being loaded enough (or asked to draw enough current). The other side is too low a load will cause the tubes to overwork and try to produce more electron emissions at the voltage it is operating at.

Because of the requirement of an output transformer and the nature of a tube amp, the output taps allow the user to extract the correct amount of power out of the amp to different loads without stressing it. A slight mismatch is OK, but too much can cause trouble.


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## greco (Jul 15, 2007)

GTmaker said:


> > There is a reason some folks buy 5 watt amps and some folks prefer 100 watt amps..just trying to point out that power (watts) does matter.
> > Im not talking volume but straight power output.


The folks preferring the 100 watt amps either want cleaner headroom/less distortion at lower volumes (e.g., jazz players) OR more volume. 



> HEre is my observation and question.... with everything I have read so far ..
> my tube amp has 4 ohm, 8 ohm and 16 ohm outputs...
> *As it stands now, I do believe that each of those outputs will have different watt ratings assuming all else is equal.*
> to be even more specific .... 2 X 8 ohms speakers connected in parallel to the 4 ohm output will have a different watts output from the amp
> ...


The parts I have bolded is where I think your belief is incorrect.

If you are not interested in/talking about volume, in what way is a 40 watt output different than a 20 watt output...apart from the obvious 20 watts difference in output? 

This might be of interest to you:
http://www.gmarts.org/index.php?go=216


Cheers

Dave


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## GTmaker (Apr 24, 2006)

fron the internet so it must be true...
G.

*How do I calculate Amplifier Output?*
The calculation for figuring out how much is fairly straightforward, and pretty much what I would expect it to be. Since ohms measure resistance, the more ohms, the less output from the amplifier. Conversely, the less ohms, the more output from the amplifier.
Since the amp is rated at a specific amount of ohms (i.e. 100 watts @ 4 ohms), a different amount of ohms will produce a different output. Two 8 ohms speakers wire in series (16 ohms total) would cause the amp to produce 25 watts to each speaker.
Amplifier Output = Amplifier Watts x (Amplifier Rated at Ohms / Speaker Chain Ohms)
Amplifier Output = 100 watts x (4 ohms / 16 ohms)
Amplifier Output = 100 watts x 1/4
Amplifier Output = 25 watts​ An amplifier designed to put out 100 watts into 8 ohms will put out 200 watts into 4 ohms. Two 8 ohms speakers wired in parallel (4 ohms total) would cause the amplifier to produce 200 watts.
200 watts = 100 watts x (8 ohms / 4 ohms)​ The amp produces 100 watts at 4 ohms. When the resistance is increased to 16 ohms, four times what it was rated, the amplifier produces one fourth as many watts.


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## greco (Jul 15, 2007)

GTmaker said:


> fron the internet so it must be true...
> G.
> 
> *How do I calculate Amplifier Output?*
> ...


Now ask yourself if this applies to tube amps.

Cheers

Dave


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## bluzfish (Mar 12, 2011)

That would be correct for a solid state type power output. A tube amplifier always sees only the consistent load on it's side of the output transformer, assuming there is no speaker mismatch on the taps on the speaker side of the transformer..


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## jb welder (Sep 14, 2010)

As the other guys pointed out, the quotes about different power into different load impedances are all about solid state amps.
Notice that their power specs are always stated at a particular load impedance. With other loads, the power output of the amp changes.
Tube amps with impedance switches (or different impedance jacks like your amp) have this feature for the exact reason of giving you full power into various load impedances. There is no advantage of using the 16ohm jack over the 4ohm jack as long as you match the load.
Solid state amps do not use output transformers, this is why they do not offer switches to allow full power into various loads. With big PA type SS amps, they sometimes offer different versions of the same amp, because of this problem. So for example, an amp that puts out 1000W per side into 4 ohms, or a different version of the amp that gives 1000W per side into 2 ohms.

All that said, this _is_ the internet. If you look hard enough, you will probably find someone who says a tube amp using the 4ohm output to a 4 ohm cab sounds better/worse than the 16ohm output to the 16ohm cab.
Ignore them :smile-new:.


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## Budda (May 29, 2007)

Hey GTmaker, might you have 2x 1ft speaker wire extra on hand? Im two short for my PPC412 and go past guelph on my way to practice tuesday. Cheers! (I have asked around locally a bit).


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## greco (Jul 15, 2007)

@budda...If you can't arrange to get the wires from GTmaker for whatever reason, I can make them up for you and meet you at the same Tim's where we met when you sold me your Agile LP...do you remember that location?

Do you need connectors (as per pic below) on each end of the wires?









Let me know.

Cheers

Dave


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## Budda (May 29, 2007)

Thanks Dave! My coworker is supposed to bring some to work for me tomorrow. If he forgets (and I will know at 5am haha) I'll PM you.


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## allthumbs56 (Jul 24, 2006)

jb welder said:


> All that said, this _is_ the internet. If you look hard enough, you will probably find someone who says a tube amp using the 4ohm output to a 4 ohm cab sounds better/worse than the 16ohm output to the 16ohm cab.
> Ignore them :smile-new:.


Resistance is futile :acigar:


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## bluzfish (Mar 12, 2011)

allthumbs56 said:


> Resistance is futile :acigar:


 







.


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## BMW-KTM (Apr 7, 2015)

Just interjecting for the sake of clarification:

FYI,
"Impedance" refers to alternating current only.
In DC power (like the kind of current a guitar amp speaker sees) it is referred to as a "load" or "resistance".

Carry on.


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## greco (Jul 15, 2007)

BMW-KTM said:


> Just interjecting for the sake of clarification:
> 
> FYI,
> "Impedance" refers to alternating current only.
> ...


Doesn't a guitar speaker see AC and not DC? 
Hence the concept "impedance matching" of the output transformer to the speaker.

DC resistance measurement of a speaker is an *estimate of the impedance *and is used because it is easy to measure with a basic meter and because measuring actual impedance takes special measurement equipment and varies with frequency. 

Please help me/correct me if i'm wrong here.

Cheers

Dave


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## BMW-KTM (Apr 7, 2015)

Technically I suppose but it's not like 110V - 60 cycle AC.
It's more like an oscillating DC current.
That may seem to some like splitting hairs but the notion has merit.
Speaker voltage, amperage and frequencies are constantly in a complicated flux of change.
Plus there are frequencies, voltages and current overlapping with one another.
You don't get a zap from touching the bare wires of a speaker lead.
I've touched guitar amp wires and felt nothing. I would imagine a high powered P/A amplifier might provide a little tingle but nothing near a wall outlet.
That's partially due to lower overall wattages but it's also due to the fact it's not a true AC current in the normal sense.
In any case, impedance is not a term applicable to guitar amp speakers although I'm sure there are some people who would disagree.
There is no end to argument in discussions like this.


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## WCGill (Mar 27, 2009)

Speakers are not amenable to DC. It's AC.


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## bluzfish (Mar 12, 2011)

WCGill said:


> Speakers are not amenable to DC. It's AC.


Ha, ha, I can attest to that! When I was a kid, I used to destroy any old electronic stuff I could find to find out how it worked. One day I was fooling around with a
1930s console radio when I happened to touch both speaker terminals. The unexpected shock blew me backwards onto my bed and I lay there contemplating how to move my limbs for several seconds. That experience is forever forged in my memory. Oh, I've had other experiences with the power of electricity over the years but I guess you never forget your first.


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## greco (Jul 15, 2007)

BMW-KTM said:


> Technically I suppose but it's not like 110V - 60 cycle AC.
> It's more like an oscillating DC current.
> That may seem to some like splitting hairs but the notion has merit.
> Speaker voltage, amperage and frequencies are constantly in a complicated flux of change.
> ...


I don't want to argue, only to understand. 

Electronics is one of my hobbies, in that I enjoy reading the theory and trying to understand it...that takes a huge effort. I also build small projects at the level of a kid in Grade 8 or so. For me, the most enjoyable projects are guitar wiring/rewiring and doing basic electronics stuff for others.

Can you point me to a reference that explains _"oscillating DC current"_ and why _"impedance is not a term applicable to guitar amp speakers" 

_Thanks

Dave


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## BMW-KTM (Apr 7, 2015)

I stand corrected.
My apologies.
I was basing my comments on knowledge gained from older musicians who taught me.
I did a little research and learned I have been in error on this all along.
I'm still a little confused about the lack of shock value but I'll get over it eventually.
I guess you still can teach an old dog a new trick.
Enjoy it while you can.


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## High/Deaf (Aug 19, 2009)

BMW-KTM said:


> Technically I suppose but it's not like 110V - 60 cycle AC.
> *It's more like an oscillating DC current.*
> That may seem to some like splitting hairs but the notion has merit.
> Speaker voltage, amperage and frequencies are constantly in a complicated flux of change.
> ...


That is the definition of AC. Only voltage/current that is not changing (think of a flat line on an oscilloscope) is considered DC. AC can be combined (or appear on top of) a DC voltage in the form of ripple. So the AC is shifted up or down in total voltage and doesn't go back and forth across 0V. 

A speaker only makes noise with an AC signal. A DC supply will push or pull the cone once applied (depending on polarity) but won't return the cone until removed. I've used a 9V battery to test devices this way.

So the output of an amp is AC. Just because it's not a steady 60 Hz doesn't disqualify it from being AC. The fact you don't feel it is because the voltage is too low and your bodies impedance is too high. Touch speaker outputs to your tongue (like a 9V battery you don't feel through your fingers), you'll feel it. 

Also, distributed PA systems like hospitals, schools, etc. use a 70V power amp output (using a transformer) to drive long speaker cables and multiple speakers (using transformers at the speaker to drop the voltage again). You touch one of those with your fingers and you feel that. It's around 50% of AC line voltage and is certainly enough to drive some current through your high-impedance fingers. Don't touch that to your tongue!


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## jb welder (Sep 14, 2010)

greco said:


> DC resistance measurement of a speaker is an *estimate of the impedance *and is used because it is easy to measure with a basic meter and because measuring actual impedance takes special measurement equipment and varies with frequency.


Correct, and the resistance we measure will read a bit lower than the actual impedance.

As far as the idea of oscillating DC, it's a way of thinking about AC. But you would need a positive and negative supply as AC is voltage moving above and below zero.
With signals that are different frequencies and overlapping and modulating and even distorting each other, it's still AC, but would be considered a complex waveform (as opposed to 120V 60Hz simple sine wave AC power).


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## High/Deaf (Aug 19, 2009)

Actually, AC doesn't have to modulate above/below 0V, it can be offset with a DC voltage. 

A car battery charger will put out 14V DC, but you can measure AC riding on top of that (if it's a good charger, should be in millivolts). Although the battery acts like a big cap, the charger can still induce some AC at 60 Hz. So you could see your DC sitting at 14, but varying between 13.9 and 14.1 V on an oscilloscope. That would be 200mV p-p of AC ripple on a 14V DC supply. AC really only means the voltage/current is alternating and not complete steady-state, as DC is.


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## GTmaker (Apr 24, 2006)

I have 2 x 8 ohm speakers so I can hook them up parallel = 4 ohms or series = 16 ohms.

Can someone please tell me if the speakers give a damme as to which option I choose.
Does one option produce anything different then the other option as far as the speakers is concerned?

please answer first then you may continue your AC/DC modulating / offset / inducing / oscilloscope voltage / lick the terminals current thingy.

G.


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## greco (Jul 15, 2007)

GTmaker said:


> I have 2 x 8 ohm speakers so I can hook them up parallel = 4 ohms or series = 16 ohms.
> 
> Can someone please tell me *if the speakers give a damme* as to which option I choose.


That will depend on the personality profile of each speaker. 



> Does one option produce anything different then the other option as far as the speakers is concerned?


No. I thought this had been established earlier in the thread.

Cheers

Dave


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## GTmaker (Apr 24, 2006)

greco said:


> That will depend on the personality profile of each speaker.
> No. I thought this had been established earlier in the thread.
> Cheers
> Dave


I have no idea what the individual personality of a speaker has anything to do with the question
of running the speaker at 4 ohms instead of 16 ohms.

Also...once you get thru all 47 responses so far...best I can gather is that it makes no different at all to the amp or to the speakers.
I have no idea why I think this but there has to be a reason that 4ohms and 16 ohms resistance exists.
If there way NO and I mean NO difference at all...why aren't all speakers just made with the same ohms reading.?
Why bother making 4, 8, 16 ohms speakers? After all, there is no difference.

About the amps...if an amp can handle a 4 , 8 , 16 ohm load, how is it possible that each one of these settings
have the exact same response from the amp.

G.


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## bluzfish (Mar 12, 2011)

Different amp transformer taps make the amp more versatile for using different combinations of speakers. I.E. if my amp only accepts an 8 ohm speaker load, what would I do if I want to connect two 8 ohm speakers instead of just one?


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## greco (Jul 15, 2007)

> I have no idea what the individual personality of a speaker has anything to do with the question of running the speaker at 4 ohms instead of 16 ohms.


It was a joke on "if the speakers give a damn"




> Also...once you get thru all 47 responses so far...best I can gather is that it makes no different at all to the amp or to the speakers.
> I have no idea why I think this but there has to be a reason that 4ohms and 16 ohms resistance exists.
> If there way NO and I mean NO difference at all...why aren't all speakers just made with the same ohms reading.?
> Why bother making 4, 8, 16 ohms speakers? After all, there is no difference.
> ...



I think you will find that 4, 8, 16 ohm speakers exist based on their various applications through time (and possibly the ease of combining speakers) and that these three impedances have become somewhat of a "standard"..there are speakers of other impedance values also..e.g., 32 ohms.

Read this for more info:
http://peavey.com/forum/viewtopic.php?t=22191

Cheers

Dave


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## Guest (Jul 11, 2015)

GTmaker said:


> I have no idea what the* individual personality* of a speaker has anything to
> do with the question of running the speaker at 4 ohms instead of 16 ohms.


probably depends on how your guitar playing sounds through them. lol.


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## greco (Jul 15, 2007)

laristotle said:


> probably depends on how your guitar playing sounds through them. lol.


There is nothing worse than unhappy speakers with low self-esteem!


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## bluzfish (Mar 12, 2011)

greco said:


> There is nothing worse than unhappy speakers with low self-esteem!



Agreed!! Especially when they play all the wrong notes.


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## greco (Jul 15, 2007)

bluzfish said:


> Agreed!! Especially when they play all the wrong notes.


Now you are diagnostically into full blown clinical depression!


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## GTmaker (Apr 24, 2006)

bluzfish said:


> Agreed!! Especially when they play all the wrong notes.



I have sold ( dumped ) plenty of guitars and amps for consistently playing wrong notes.

G.


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## Jimmy_D (Jul 4, 2009)

impedance selector switch?


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## gtrguy (Jul 6, 2006)

GTmaker said:


> I have 2 x 8 ohm speakers so I can hook them up parallel = 4 ohms or series = 16 ohms.
> 
> Can someone please tell me if the speakers give a damme as to which option I choose.
> Does one option produce anything different then the other option as far as the speakers is concerned?
> ...


The one advantage of having the speakers in parallel is in case of failure- if one of the speakers goes open the other speaker will still be loading the output of the amp. If the speakers are in series and one of them goes open the amp is seeing no load at all- not a good scenario for a tube amp.


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