3 ohm load on a 2 ohm stable stereo

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

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.

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.

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.