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3 ohm load on a 2 ohm stable stereo

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=48688
Printed Date: October 31, 2024 at 6:15 PM


Topic: 3 ohm load on a 2 ohm stable stereo

Posted By: eiknujrac
Subject: 3 ohm load on a 2 ohm stable stereo
Date Posted: January 26, 2005 at 9:14 PM

I have an amp that is 2 ohm stable STEREO. From what i have read, you cannot run a 2 ohm mono load, as each channel "sees" half of the resistance. So does this mean that I cannot run a dual 6 ohm voice coil sub parrallel bridged? If so, would my only other option be to run it at 12 ohms? Or could i hook up each voice coil to a channel?



Replies:

Posted By: uthinkuknoaudio
Date Posted: January 26, 2005 at 9:18 PM
your amp is 2 ohm stable, but it can play 3 ohms as well. It will play it also with a lesser amount of distortion that it would at 2 ohms. (That is assuming that besides being 2 ohm stable you can run the amp at 4 ohms)...

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"I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.




Posted By: eiknujrac
Date Posted: January 26, 2005 at 9:30 PM
I know, but from what I have been told, a 2 ohm stable stereo amp, cannot push a 2ohm load mono, because each channel sees half the load. Is this true? If so, if i bridged the 3 ohm load, would this not show a 1.5 ohm load to each channel which is below the 2 ohm stable floor? Is there any other option other than running the DVC 6 ohm sub at 12 ohms?




Posted By: haemphyst
Date Posted: January 26, 2005 at 9:49 PM
Dual 6 ohm voice coils in parallel is 3 ohms, bridged to the amp is 1.5 ohms per channel. it is POSSIBLE your amp MAY run this load, but I would not push it. 1.5 ohm is outside the safe operating area of that amp... uthink thinks...

But wait, is it a Nakamichi?

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."




Posted By: eiknujrac
Date Posted: January 26, 2005 at 9:57 PM

No

Power Acoustik 1600.2 (I know, I know, but again, it was given to me)





Posted By: eiknujrac
Date Posted: January 26, 2005 at 11:47 PM

I guess what im asking is, is it possible to hook up each voice coil to a different channel?

If i do this, i assume both the channels would need the same signal, and my amp doesnt have a mono switch. Could I modify the RCA in any way to run a mono signal?





Posted By: eiknujrac
Date Posted: January 26, 2005 at 11:56 PM
And what would happen if i ran the 3 ohm load, would the amp just get really hot?




Posted By: audifive
Date Posted: January 27, 2005 at 12:15 AM
you can fry the amp running it under the ohm load its supposed to go.  but from what i have seen... 4 ohm speakers can be from 3 to 5 ohm when tested with a meter.  run the voice coils paralell and test with a meter for resitance.  if it is over 3, then in my opinion go for it but i keep the gain down to a reasonable level.  i wouldnt worry about it.  by the way, when you test the speaker for resistance, dont have it upsidedown or any other way but facaing up or out, cuz it can give an innaccurate readout.  if you start to blow fuses or the amp stops from getting hot, then rewire it or hook it up the other way.  or get a different amp.  i just noticed that it was a power acoustic so be careful.  but their amps arent as bad as people think from what i have seen.  i have installed several PA amps with no prob.  In my experience, i have troubleshot more high end systems because of faulty equipment than i have power akoustik stuff.  Be careful with their subs though do not put them in anything with a port cuz it WILL get damaged.  other than that, i guess its time to shut up.




Posted By: haemphyst
Date Posted: January 27, 2005 at 12:16 AM
It might, it might not run at all, it might fry the amp... seeing as it is a Power Acoustik amp, prolly any combination of the above... Not the greatest of gear - along the lines of Audiobahn... Otherwise, your option is 6 ohms per channel, wire in series and bridged OR run one channel to each voice coil and leave the amp in stereo. Same difference. Your amp would make a little more than half it's 4 ohm rating i.e. rated 400 wpc @ 4 ohms, it would now make probably 300 wpc @ 6 ohms. I don't know that amp, so look it up in you owners' manual.


     ::::EDIT:::::

DO NOT USE A DC RESISTANCE AS A BASIS FOR DETERMINING IF A LOAD IS SAFE FOR AN AMPLIFIER! A speaker is a complex load, and it WILL NOT behave the same in operation. audifive, that is bad information, and potentially dangerous to someone ELSE's gear.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."




Posted By: damn-im-good
Date Posted: January 27, 2005 at 2:21 AM

Has anyone tried running a phoenix gold qx 500.1 at 1 ohm, cuz it says it's only 2 ohm stable. But could it still handle running at 1 ohm?

Thanx, Austin



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Alpine CDA-9831, two 12" JLw3's running off of Phoenix gold 500.1 monoblock and 90.2 for speakers!




Posted By: eiknujrac
Date Posted: January 27, 2005 at 2:12 PM

Thanks for the help guys, thats why I love this site





Posted By: audeogod
Date Posted: January 27, 2005 at 8:09 PM

This is in response to the DC resistance comment.  DC resistance is just what it says it is.  A resistance that you can measure.  Speakers are rated for impedances, which is similar to resistance, but impedance takes into account what frequencies the voice coil is subjected to.  The higher the frequency goes, the higher the impedance gets,  but the lower the frequency goes, then the lower the impedance becomes.  A speaker is not a resistor, whose resistance does not change with frequency.  It's more like an inductor(the coil is).  The speaker manufacturer selects(creates) a coil that has a certain inductive property depending on what type of speaker they are making, and that property allows it to operate at a particular frequency range and maintain an overall 4 ohm load(if it's rated at 4 ohms that is, I know yours were rated at 3 ohms).  Inductors also have a DC resistance, but that is only in a powered down state and that's why you shouldn't use measured ohm loads to tell if it's safe to use.  The measured ohm load may be close to the actual impedance but since the impedance is what the resistance of the coil is while the speaker is playing, and that figure is CONSTANTLY changing based on the frequencies it is playing, then it won't always be the measured amount of ohms. See?? 

So to say that a speaker is 4 ohms, well, that is...uh...shall we say...an average that a speaker will be during play mode if it's being played at the proper frequency range.  It can go up or down from that average.  I don't like to use the word "average" to describe the impedance, cause it can go way above or way below the rating based on frequencies fed to it, and of course the impedance could stay there for extended periods of time if the frequencies do not change. 

I think that could possibly be another good good reason to make sure you have good crossovers when using subs or speakers on amps that you are pushing to their minimum ohm load capacities.  Cause the overall impedance may not be what the amp can handle safely even though the speaker's measured DC resistance was, and playing it too long like that I think might possibly damage the amp.  Remember, low frequencies create lower impedances.  So if you are using cheap no name subs or subs of a quesionable reputation, then the frequency range may not be as low as you would like(regardless of what they said it was on the box) and of course the amp cannot tell what the frequency range of the speaker is, so it just sends all of them(whatever is not filtered by a good crossover that is) and the impedance varies accordingly, and therefore may not remain at a safe level.  That's one reason I like using the 4 ohm rating of the amp instead of trying to squeeze every watt out of it at 2 ohms.  It gives it a margin of error above and below the impedance it is running at.  If my amp is stable at 2 ohms, but I run it at 4, then when impedance dips down to like 2.5 or so,  it will be fine.   

Also, even though speaker voice coils say they respond to a certain frequency range does not mean that the speaker isn't getting those frequencies that is can't respond to.  They are still there, and they still create heat, but cause no cone movement to help dissipate that heat, so it build up heat and ruins speakers over time.  That's another reason for a good crossover. 

One thing is for sure.  If a speaker is getting frequencies it shouldn't play, then impedances won't be right, and either the speaker, or the amp will die eventually as a result.  I hope everyone here has the common sense to use a crossover on subs, but you wouldn't believe the number of people I've seen just hook them straight up, not comprehending even the slightest thing about impedances.  So long as it pounds hard, then that's fine by them.

Also, hope I didn't stray from the subject too far here.



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audeogod

92 Chevrolet Cheyenne 1/2 ton truck
Pioneer DEH-41
Eclipse 2-way coaxial 4x6's in dash
Eclipse 3-way coaxial 6 1/2's in doors(cut to fit)
Pioneer GM-X332 amp bridged to Kicker 8" sub




Posted By: eiknujrac
Date Posted: January 27, 2005 at 8:41 PM

Awesome explanation -

Another reason i love this site.

I like it when people take the time to explain what they mean, and not just say "hey it wont work like that" or "you cant do that"

I appreciate the time you took to write that.





Posted By: audeogod
Date Posted: January 27, 2005 at 9:18 PM

You're welcome.  And I didn't mean to make you think this is a serious problem just waiting to happen or that the amp or speaker will fry in a second if the impedances are off somewhat.  Depending on how far off they are, it may last a while, but die in the end, and because it lasted for...say...6 months or a year...then people can't figure it out and think that it was something else that killed it when it finally goes. 

I started out talking about impedances and safety for the amp, but this conversation led to crossovers instead.  Really, when you think of impedances, you have to consider frequencies and crossover points because these things directly affect the impedance and safe operating range of the amp.  That's why it was so long. 



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audeogod

92 Chevrolet Cheyenne 1/2 ton truck
Pioneer DEH-41
Eclipse 2-way coaxial 4x6's in dash
Eclipse 3-way coaxial 6 1/2's in doors(cut to fit)
Pioneer GM-X332 amp bridged to Kicker 8" sub





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