Low impedance?

[Fi-brations 10+ year member]

What are the advantages and disadvantages of using one amp for two subs at 0.5ohms vs. using 2 amps for two subs at 1ohm? Are there any problems with running an amp at 0.5ohms even if the amp is half ohm stable? Would I have noticeable distortion or would it be too small to hear? Would it put more stress on my electrical system/amp(s)/subs? I read something about subwoofers sounding louder with less wattage at higher ohms vs more wattage at lower impedance. What do u guys think? I'm looking to run 1500watts to each of my Fi Qs which have dual two ohm voice coils so I can wire two 1500 watt amps to them at 1 ohm or I could run them with one amp that does 3k watts at 0.5 ohms, this will be in the future not anytime soon

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[R34P3R 10+ year member]

Dropping an amp to .5 ohm will generate more heat in the amp, which will shorten its lifespan, will have more distortion than if run at 1ohm, and will put a higher strain on your electrical system because it demands more power. Running two separate amps, you will have to run wires for both, will have to match the gains on each amp, and will also cause a major strain on your electrical.

 

[mylows10 5,000+ posts]

this is true ,but most systems will have box rise ,so if the amp will work at .5 ohms, after box rise it will be around 2-4.so it will be fine.you still need to upgrade the electrical and the distortion you prolly wont even be able to notice unless you turn it up really really loud

 

[ahole-ic]

this is true ,but most systems will have box rise ,so if the amp will work at .5 ohms, after box rise it will be around 2-4.so it will be fine.you still need to upgrade the electrical and the distortion you prolly wont even be able to notice unless you turn it up really really loud

Common mistake. Impedence rises AND drops. This is why wiring below recommended is dangerous. With music, certain frequencies can cause impedence to be as little as 1/4 of nominal. So don't count on impedence rise if you're not burping 1 frequency.

 

[mylows10 5,000+ posts]

never have heard of the impedance going any lower in a box only rising,even when just playing music.i know most of the impedance rise happens during deep bass notes and less when not,but also consider who plays there music full tilt always,where it would really make the difference,no one. i'm just sayin

 

[Germ305 10+ year member]

Someone explain Box rise to me...I've always heard it here on the forums...Never really grasped what it did.

 

[ahole-ic]

never have heard of the impedance going any lower in a box only rising,even when just playing music.i know most of the impedance rise happens during deep bass notes and less when not,but also consider who plays there music full tilt always,where it would really make the difference,no one. i'm just sayin

You've heard of it now. I'm enlightening you.

 

[ahole-ic]

Someone explain Box rise to me...I've always heard it here on the forums...Never really grasped what it did.

The impedence of the woofer is effected by the inductance of the coil at different frequencies. at the box's peak rise will be the highest. Everywhere else it drops below nominal or slightly rises.

 

[Fi-brations 10+ year member]

Dropping an amp to .5 ohm will generate more heat in the amp, which will shorten its lifespan, will have more distortion than if run at 1ohm, and will put a higher strain on your electrical system because it demands more power. Running two separate amps, you will have to run wires for both, will have to match the gains on each amp, and will also cause a major strain on your electrical.

So u r saying that either way will have its own large effect on the electrical, so if I could find an one amp that gives 3k watts at 2ohms

The amp would last longer and put less strain on the electrical even if it is still giving the same wattage? R there many choices of amps that would have a true rating of close to 3k watts at 2 ohms? Would that be cost effective or would it be more reasonable to do one of the first two mentioned methods? What do ppl who run large amounts of wattage usually have an impedance of? Thanks

 

[Crapalier 10+ year member]

You've got to look at the actual specs... Fi rates their dual 2 at 1.4ohm.. If you wire up 2 of those in parallel you're gonna get a .35 ohm load... that's a lot to ask out of an amp for daily!

Music is dynamic, so any daily load of less then rated is dangerous... If you are playing music and not test tones, I'd strongly suggest not going to a lower impedance than rated.

 

[globalminds_ent 10+ year member]

audiopipe 3k does 3kw at 2 ohms and is only 2 ohm stable

 

[globalminds_ent 10+ year member]

better quality amps can handle under 1 daily hell I had a power acoustic on Half ohm daily for months before I sold it and the cheapest half ohm stable amp out is the lanzar opti200d $250 onlinecarstereo so if u wanna be safe and thinkin of runnin 2krms there u go

 

[hispls 5,000+ posts]

1/2 ohm is always more strain on the amp and most amps are not terribly efficient at that impedence. The real benefit if you're willing to take the risk is having only 1 amp instead of 2 and squeezing that little bit extra power out of what you have. Also any given amp will most definitely sound better at higher impedence. That's not to say an amp that's 2 ohm stable at 2 ohms will sound any better than a different amp that's 1 ohm stable at 1 ohm. That's apples to oranges.

Impedence of a speaker system depends on a lot of factors (not just inductance of the coil). Just a woofer in an anechoic chamber is a pretty complex circuit (though impedence is more or less a bell curve around FS). Add box, port, and cabin effects and it's even more complex. In fact, odds are your amp will only actually "see" rated/nominal impedence at 2 frequencies.