Running 6 ohms on 8 ohm speaker?? - AVS Forum
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post #1 of 14 Old 09-04-2008, 07:43 PM - Thread Starter
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I have speakers rated for 8 ohms but my reciever will only let me select between 4-6-16 ohm output....will I damage the speakers running them at 4 or 6?? I dont really understand the whole ohm thing so if there is an "Ohms for Dummies" that someone can point me to that would be awesome....after they answer the question that is, lol.

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post #2 of 14 Old 09-04-2008, 07:47 PM
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yea, you "should" be fine setting it at 6. the speaker will pull what it needs. by setting it at 6 you allow it to go down to 6 ohms. which in theory will put it running 8 ohm stable. its not an ideal setup, but it may be fine. just dont set it higher than 8.
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post #3 of 14 Old 09-04-2008, 07:54 PM
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Quote:
Originally Posted by USMCGrunt0307 View Post

I have speakers rated for 8 ohms but my reciever will only let me select between 4-6-16 ohm output....will I damage the speakers running them at 4 or 6?? I dont really understand the whole ohm thing so if there is an "Ohms for Dummies" that someone can point me to that would be awesome....after they answer the question that is, lol.

The "ohm" setting is present to protect the receiver. When the speaker's impedance (ohms) decreases, the receiver has to supply more current to produce the same power output. When you select the lower impedance setting, you're essentially engaging a protection circuit which will limit the current output. This is done to prevent the power supply, thus you will not damage your speakers by setting the impedance too low. You may have problems with your receiver if you set it too high.
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post #4 of 14 Old 09-05-2008, 03:37 AM
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If I may, I also have the same situation. All 8-ohm Infinity Primus, but my AVR only has settings for:

A: Main = 4-ohms, Center & Surround = 6-ohms
B: Main, Center & Surround = 8-ohms

Which would be a better choice? From what cjm7c said, I believe it's better to go with A?

Thanks!

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post #5 of 14 Old 09-05-2008, 05:17 AM
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Quote:
Originally Posted by blued888 View Post

If I may, I also have the same situation. All 8-ohm Infinity Primus, but my AVR only has settings for:

A: Main = 4-ohms, Center & Surround = 6-ohms
B: Main, Center & Surround = 8-ohms

Which would be a better choice? From what cjm7c said, I believe it's better to go with A?

Thanks!

You'd want to go with B
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post #6 of 14 Old 09-05-2008, 07:10 AM
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Originally Posted by jzoz01 View Post

You'd want to go with B

Still B even though the P362s are known to dip down to 4-ohms? Thanks!

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post #7 of 14 Old 09-05-2008, 07:27 AM
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Quote:
Originally Posted by blued888 View Post

If I may, I also have the same situation. All 8-ohm Infinity Primus, but my AVR only has settings for:

A: Main = 4-ohms, Center & Surround = 6-ohms
B: Main, Center & Surround = 8-ohms

Which would be a better choice? From what cjm7c said, I believe it's better to go with A?

Thanks!

Definitely B. If your speakers were all 4 ohm nominal, then you would want to select the lower impedance setting.
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post #8 of 14 Old 09-05-2008, 07:30 AM
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Alright, thanks guys! Appreciate it.

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post #9 of 14 Old 09-05-2008, 08:06 AM - Thread Starter
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Im wanting to protect my reciever seeing as I just bought it and it would be more costly to replace it then the speakers....so lemme get this straight....it takes more "effort" on the recievers part to drive a lower ohmed speaker? So...what happens if I choose to drive an 8 ohm speaker at 10 or 12 ohms instead of the 8 that the speaker was intended to run at? Damage to any equipment? Degradation of sound quality?

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post #10 of 14 Old 09-05-2008, 10:19 AM
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Quote:
Originally Posted by USMCGrunt0307 View Post

Im wanting to protect my reciever seeing as I just bought it and it would be more costly to replace it then the speakers....so lemme get this straight....it takes more "effort" on the recievers part to drive a lower ohmed speaker? So...what happens if I choose to drive an 8 ohm speaker at 10 or 12 ohms instead of the 8 that the speaker was intended to run at? Damage to any equipment? Degradation of sound quality?

"Ohm" is the measure of electrical impedance. Your speakers will always have an 8 ohm impedance. Since your amp is almost certainly a constant-voltage source, the amount of current your system draws for a particular SPL is fixed. The setting in your receiver will essentially limit your speakers from going beyond a certain level, because too much current will overheat the amp. Of course, the amp has an overheat protection circuit already, and will shut itself down if it get's too hot. So the setting is really there to cover the manufacturer's legal butt, and you should turn it to the highest impedance setting you can (as that will yield the most current, thus the best performance), regardless of what you're speakers are rated at.

P.S. Your speakers do not have a fixed impedance anyway.

-Jason
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post #11 of 14 Old 09-05-2008, 10:40 AM
 
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Quote:
Originally Posted by Hurtful Goat View Post

"Ohm" is the measure of electrical impedance. Your speakers will always have an 8 ohm impedance. Since your amp is almost certainly a constant-voltage source, the amount of current your system draws for a particular SPL is fixed. The setting in your receiver will essentially limit your speakers from going beyond a certain level, because too much current will overheat the amp. Of course, the amp has an overheat protection circuit already, and will shut itself down if it get's too hot. So the setting is really there to cover the manufacturer's legal butt, and you should turn it to the highest impedance setting you can (as that will yield the most current, thus the best performance), regardless of what you're speakers are rated at.

P.S. Your speakers do not have a fixed impedance anyway.

This seems confusing and contradictory, but maybe I'm just reading it wrong. You say the speakers will always be 8 ohms, then say they do not have a fixed impedance
Seems to me the highest impedance setting will yield the Lowest current, not the Highest. If you had an amp Without settings, it would draw more current at lower impedances, not the other way around.
I think the goal is to pick the setting that most closely matches the speaker impedance, although the actual speaker impedance may vary wildly over frequency, so you have to trust that the "nominal" rating is representative.
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post #12 of 14 Old 09-05-2008, 11:21 AM
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Quote:
Originally Posted by tcb-player View Post

This seems confusing and contradictory, but maybe I'm just reading it wrong. You say the speakers will always be 8 ohms, then say they do not have a fixed impedance
Seems to me the highest impedance setting will yield the Lowest current, not the Highest. If you had an amp Without settings, it would draw more current at lower impedances, not the other way around.
I think the goal is to pick the setting that most closely matches the speaker impedance, although the actual speaker impedance may vary wildly over frequency, so you have to trust that the "nominal" rating is representative.

I was generalizing about them always being 8 ohm. That was probably a bad idea to keep that there after the note of varying impedances.

Anyways, the impedance setting in your receiver does not actually affect your impedance. That is determined by the physical properties of your speakers. Instead it affects a limiter of some sort on the power supply that reduces the maximum current the system can output. The lower you set it, the more it limits the current, for supposed "safety". Plenty of amps DO lack impedance settings, including most pro amps and stand alone home amps. In fact, it seems the nicer or more powerful the amp, the rarer these switches become.

The reason being, with the smaller amps in receivers, there is a concern they can't supply the needed current (or dissipate the heat from it) to 4 or 6 ohm speakers all the time, and could overheat if driven hard. The amp of course will go into protect instead of being damaged, but which would annoy the average customer more: A menu setting that makes the device "safer", or an AVR that randomly shuts down for reasons they don't understand? Of course, it's the first one. They wouldn't know it cuts down on the amp's dynamic power while not actually making anything or anyone safer, including the amp itself.

Sound engineers and audiophiles/hobbyists would know why current limiting is bad, and why amps go into protect, and would prefer not to have these switches on their amps. They would want them to have full power all the time, and shut themselves off it comes to that. Hence the reason pro amps and standalone home amps generally don't have impedance switches.

Now that you know, you don't need one either, so go ahead and set it to the highest impedance choice (least current limiting)

-Jason
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post #13 of 14 Old 09-05-2008, 01:22 PM - Thread Starter
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Ok, im understanding more now....but when you say I should set it to the highest setting is that the lowest number meaning the amp allows maxium output?

BTW, I finally found it in the manual and in one part it says reciever accepts 4-16 ohms and then in another part it says use the 6 ohms setting for speakers between 6-16 ohms...so I got the direct answer from the manual after I posted the question....but you guys have given me some of the "why" that I so annoying about getting sometimes...thanks, lol.

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post #14 of 14 Old 09-07-2008, 03:06 PM
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i have a similar situation that confuses me as well , i have all 6 ohms speakers which are compatible with the AVR but on my DENON AVR-788 it says if Front A or B (6-16 ohms) and if Font A+B (12-16 ohms) can i still plug my speakers or i need to have min 12 ohms speakers? or can i put 2 speakers together in series(6+6=12 ohms) and then instead of 4 speakers for A+B i would end up with 8?
thanks for any help
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