Funny. I'm a real EE and was going to stay out of it except for posting about waiting for an electrician to show up. He does this sort of stuff day in, day out.
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Why 2 ohms is not a good idea..
- Thread starter chicago_mike
- Start date
Maybe he meant it as sarcasm....
'cept maybe those who can't detect sarcasm?....
LOL!! (just joking BTW)
- Feb 16, 2008
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- John K Custom Basses
Bob Lee (QSC)
In case you missed it, I work for QSC Audio!
- Jul 3, 2001
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- Former Technical Communications Developer, QSC Audio
With a 2Ω loudpseaker load, your cable would have to have over 0.3 ohms of resistance to waste 25% of the power the amp puts out. That's really a lot of resistance for any normal length of speaker cable. I'd shoot for no more than 0.1Ω in a speaker cable into a 2Ω load; consider that even a 3-ft cable of 14 AWG copper would have a total resistance of only 0.015Ω, and it's clear that it's not necessary to use 10-gauge wire with lengths longer than a foot.
Are you talking about the power transformer? Presumably, if the amp is rated for 2Ω operation, the transformer can handle the demand of normal audio operation. Your data are too vague to have any meaning.
Me likes big wire but none of that so big you can't carry it.
I used 12 gage SJ Cable with Speakons for my PA Cables and routinely run 6x15's at 2 ohms per side from my QSC RMX 2450 and I use 100' Cables. Now I pretty much only crank the Drums and Vocals in the PA and let the Guitar/Bass Rigs crank from the stage with a little of them in the PA for a braoder spectrum.
I have not noticed any toatsy cables or weak PA. For outside Gigs I make the Drums sound like a loud V Twin Thundering.
For Monitors I only run Vocals through them.
For outside Gigs concerning power I use two 300' 10 gage extension cords pulling from two seperate circuits and run the band off them (when I need that many feet) with no troubles so far.
For my Bass Rig I got a little carried away. I have a Preamp/Poweramp setup. I have a 20 foot 10 Gage SO Cord that goes into a 4 gang Box with an Industrial Grade Surge Pretection/RFI EMI supression in it. I go from there to a 10' 12 gage SO cord into a female twistlock, to male twistlock then splitting to two 14 gage IEC Cables. Both IEC Cables go into the one male twistlock, one goes to my Preamp and the other to my Poweramp. I do not allways use the 20' 4 gang box if I do not need the extra footage but it comes in handy some times.
Now from my Poweramp to my Speaker Cabs I use a 1 1/2' 12 gage SO Cable to my top Cab and a 2' 12 gage SO Cable to my bottom Cab.
I used 12 gage SJ Cable with Speakons for my PA Cables and routinely run 6x15's at 2 ohms per side from my QSC RMX 2450 and I use 100' Cables. Now I pretty much only crank the Drums and Vocals in the PA and let the Guitar/Bass Rigs crank from the stage with a little of them in the PA for a braoder spectrum.
I have not noticed any toatsy cables or weak PA. For outside Gigs I make the Drums sound like a loud V Twin Thundering.
For Monitors I only run Vocals through them.
For outside Gigs concerning power I use two 300' 10 gage extension cords pulling from two seperate circuits and run the band off them (when I need that many feet) with no troubles so far.
For my Bass Rig I got a little carried away. I have a Preamp/Poweramp setup. I have a 20 foot 10 Gage SO Cord that goes into a 4 gang Box with an Industrial Grade Surge Pretection/RFI EMI supression in it. I go from there to a 10' 12 gage SO cord into a female twistlock, to male twistlock then splitting to two 14 gage IEC Cables. Both IEC Cables go into the one male twistlock, one goes to my Preamp and the other to my Poweramp. I do not allways use the 20' 4 gang box if I do not need the extra footage but it comes in handy some times.
Now from my Poweramp to my Speaker Cabs I use a 1 1/2' 12 gage SO Cable to my top Cab and a 2' 12 gage SO Cable to my bottom Cab.
Man, the hysterics of the anti 2ohm crowd never cease to amaze me - funny thing: I've probably played several hundred gigs @ 2 ohms, and have only burnt down a couple of venues, hahaha...
What a load of crappola - some of the things in the OP are truly laughable...
- georgestrings
What a load of crappola - some of the things in the OP are truly laughable...
- georgestrings
- Feb 16, 2008
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- John K Custom Basses
i run my SVT's at 2 ohms all the time. never had a problem or lack of power. IMO, this is nonsense.
sniff sniff...... Do I smell TROLL Here?
Mike
I was wondering what that smell was!
nonsense? A few EE's from the military will disagree. I did say safely. But look how many speakers are now used at 2 ohms. look how much power each speaker gets..not much.
Start from the power supply and test va. I love my sm900 but its an old one wich is inferiorly designed. Theres a reason why they get super hot even at an 8 ohm total load.
Start from the power supply and test va. I love my sm900 but its an old one wich is inferiorly designed. Theres a reason why they get super hot even at an 8 ohm total load.
- Dec 18, 2000
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So on the basis of one particular faulty sample/example you expound on an almost disconnected level, and ignore every bit that's been posted since your first "joke"?
Truly you are Rip Van Winkle and then some.
Truly you are Rip Van Winkle and then some.
Obviously the original poster was a troll*... an ignorant troll with poor communication skills to match the ignorance........ You can take the "ignorant in the classic sense, or the Missouri sense ("acting ignorant"...).
But, in any case....... a few points.
yes, heavier wire would be a good plan with a 2 ohm load....... and a speakon connector for higher power usage.
As far as the wire size vs the impedance, it is as mentioned, a matter of proportion.... A given wire size/length will waste exactly the same proportion of the total power at any power level with a speaker of any given impedance.
For those worried about the wire size in the cabinet, think of the wire size in the speaker! The voice coil tends to be wound with wire that is closer to the size of ONE STRAND of the thinnest wire used in the cabinet..... most wire has at least 7 strands. The wire in the cabinet may total up to 0.05 ohm, the 2 ohm speaker is probably 1.6 ohms resistance, with the rest made up of "back EMF" and inductance.
Any competently designed amp will be able to handle loads probably to half the rated impedance or so.... so a 2 ohm amp can deal with a load of 1 to 1.5 ohm without suffering electrical problems, and can be shorted without damage. neither of those is a good plan, but they shouldn't damage the amp.
Similarly, the speaker can handle whatever it is rated at, so that isn't an issue either (other than thermal vs x-damage issues).
As for wire, 18 ga wire is almost 8 ohms per 1000 feet. So a 6 foot speaker cable , which is 12 foot of wire, has a resistance of around 12/1000 of 8 ohms, or not quite 0.1 ohm. That means it will waste 1/21 of the total power delivered into 2.1 ohms, or at 1200W, about 57 watts.... You would want to consider a heavier cable.
14 ga cable, which is widely available at the local Lowe's or Home Depot in the states, has about 2.5 ohms per 1000 feet, so 6 foot of it is about 0.03 ohm..... at 1200W it will waste only about 18 watts, which is probably very reasonable, since you cannot use a continuous 1200W anyway..
Considering that the AVERAGE power you actually USE , even at full volume thrash, is probably only around 400 to 600W with a 1200W amp, the issues are much less serious.
For the most part, I'd consider the original poster to be a troll, and the concerns raised are not OF concern for any decent amp.
It IS a reminder to use thicker speaker wire, to avoid losing too much power.
* Since a classic troll never comes back after posting something inflammatory, I see that the O.P may not actually fit the description. But I'll stand by the rest, ignorance shows, and part of the post is totally undecipherable.
edited to add missing zero in "1000". Thanks Bob......
But, in any case....... a few points.
yes, heavier wire would be a good plan with a 2 ohm load....... and a speakon connector for higher power usage.
As far as the wire size vs the impedance, it is as mentioned, a matter of proportion.... A given wire size/length will waste exactly the same proportion of the total power at any power level with a speaker of any given impedance.
For those worried about the wire size in the cabinet, think of the wire size in the speaker! The voice coil tends to be wound with wire that is closer to the size of ONE STRAND of the thinnest wire used in the cabinet..... most wire has at least 7 strands. The wire in the cabinet may total up to 0.05 ohm, the 2 ohm speaker is probably 1.6 ohms resistance, with the rest made up of "back EMF" and inductance.
Any competently designed amp will be able to handle loads probably to half the rated impedance or so.... so a 2 ohm amp can deal with a load of 1 to 1.5 ohm without suffering electrical problems, and can be shorted without damage. neither of those is a good plan, but they shouldn't damage the amp.
Similarly, the speaker can handle whatever it is rated at, so that isn't an issue either (other than thermal vs x-damage issues).
As for wire, 18 ga wire is almost 8 ohms per 1000 feet. So a 6 foot speaker cable , which is 12 foot of wire, has a resistance of around 12/1000 of 8 ohms, or not quite 0.1 ohm. That means it will waste 1/21 of the total power delivered into 2.1 ohms, or at 1200W, about 57 watts.... You would want to consider a heavier cable.
14 ga cable, which is widely available at the local Lowe's or Home Depot in the states, has about 2.5 ohms per 1000 feet, so 6 foot of it is about 0.03 ohm..... at 1200W it will waste only about 18 watts, which is probably very reasonable, since you cannot use a continuous 1200W anyway..
Considering that the AVERAGE power you actually USE , even at full volume thrash, is probably only around 400 to 600W with a 1200W amp, the issues are much less serious.
For the most part, I'd consider the original poster to be a troll, and the concerns raised are not OF concern for any decent amp.
It IS a reminder to use thicker speaker wire, to avoid losing too much power.
* Since a classic troll never comes back after posting something inflammatory, I see that the O.P may not actually fit the description. But I'll stand by the rest, ignorance shows, and part of the post is totally undecipherable.
edited to add missing zero in "1000". Thanks Bob......
Yeah, it appears to be more trolling than sheer ignorance...
I never could understand how some people have nothing better to do than to troll a forum - truly pathetic, IMO...
- georgestrings
I never could understand how some people have nothing better to do than to troll a forum - truly pathetic, IMO...
- georgestrings
Yes, but each internal wire run only powers one or two speakers. A typical 4x10 has 4 inside conductors for a series/parallel connection. It's plenty, really.
Pretty sure he was kidding.Just how far do you expect your amp to fall, anyway?
Mine runs cool and easy into 4ohms, cranked, all day long. Most likely yours needs to be rebiased, a common maintenance point for older SWR amps. And/or you have it in a too-small box, restricting it's(admittedly poorly designed) ventilation.
This would be a more interesting post if you weren't off by a factor of 20.
Lets look at the specs for Mogami W3103 11 gauge cable here:
http://www.mogamicable.com/Bulk/micr_cables/speaker_cab/speaker2.html
The DC resistance of this cable is 0.0015 ohms/foot. Lets round your 3 foot cable up to 10 feet, for a resistance of a whopping 0.015 ohms. Modeling your speaker as a 2 ohm resistor, the voltage divider circuit would result in:
The cable dissipating 0.74% of the power the amplifier is delivering, or earth shattering 8.9 watts if your amp is delivering 1200 watts. For the curious, the fraction of the output power dissipated by the cable would is:
Rcable/(Rcable + Rspeaker)
Obviously, things could get very ugly if you try using an instrument cable, or even a 1/4" jack at these currents.
As for your saftey concerns:
A 1200 Watt RMS signal into a 2 ohm load works out to a 50V RMS signal. I wouldn't lick the cable's conductor, but its quite unlikely to injure an adult. And if you short the speaker output into anything, your amp's shutdown circuit should trip.
If you disagree with my analysis I'd certainly like to see how you arrived at your figures.
EDIT: Fell for a troll again. When will I learn?
Lets look at the specs for Mogami W3103 11 gauge cable here:
http://www.mogamicable.com/Bulk/micr_cables/speaker_cab/speaker2.html
The DC resistance of this cable is 0.0015 ohms/foot. Lets round your 3 foot cable up to 10 feet, for a resistance of a whopping 0.015 ohms. Modeling your speaker as a 2 ohm resistor, the voltage divider circuit would result in:
The cable dissipating 0.74% of the power the amplifier is delivering, or earth shattering 8.9 watts if your amp is delivering 1200 watts. For the curious, the fraction of the output power dissipated by the cable would is:
Rcable/(Rcable + Rspeaker)
Obviously, things could get very ugly if you try using an instrument cable, or even a 1/4" jack at these currents.
As for your saftey concerns:
A 1200 Watt RMS signal into a 2 ohm load works out to a 50V RMS signal. I wouldn't lick the cable's conductor, but its quite unlikely to injure an adult. And if you short the speaker output into anything, your amp's shutdown circuit should trip.
If you disagree with my analysis I'd certainly like to see how you arrived at your figures.
EDIT: Fell for a troll again. When will I learn?
