6 ohm Speakers with 8 ohm receiver power question. - AVS Forum
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post #1 of 29 Old 08-09-2011, 10:45 PM - Thread Starter
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Hi there.

I have just purchased a new Yamaha rx-v1067 receiver that is at 8 ohm. In the manual
it says to match the impedance of the speaker to the receiver. My speakers are wharfedale diamond 9s at 6 ohm.

Question is :

1. Do I really have to change the receivers impedance to 6 ohms ?
2. If I change it to 6 ohms will the speakers sound better ?
3. I have heard you lose power at the receiver if you decrease the impedance from 8 to 6
How much power will I be losing ? i.e will it be a discernible difference ?

Thanks in advance.
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post #2 of 29 Old 08-09-2011, 11:18 PM
 
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Run the 1067 and make sure it doesn't get overly hot at the volume you will be normally achieving. If it never gets too hot, it won't shut down.
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post #3 of 29 Old 08-15-2011, 08:38 PM - Thread Starter
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Quote:
Originally Posted by schan1269 View Post

Run the 1067 and make sure it doesn't get overly hot at the volume you will be normally achieving. If it never gets too hot, it won't shut down.

Thanks for the reply. After running it loud for half an hour , I put my hand on the grill at the top and noticed it was only warm, but not hot, so I think its ok.

However, my next question is,

1. Will there be reduced power output If i switch the receiver to
6 ohms ? Would the sound come out cleaner perhaps ? Or would it not make a difference. ?

2. Would it be worth my while to change to 8 ohm speakers ?

Thanks in advance.
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post #4 of 29 Old 08-15-2011, 09:10 PM
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Normally if you change the receiver to 6 ohms there's an increase in watts per channel. So I would change it to 6 ohms.

Fred
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post #5 of 29 Old 08-15-2011, 09:20 PM
 
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MgFred has it backwards...

The amp will create more power if you LEAVE IT ALONE.

The point of a 6(or 4 ohm) setting is to tell the receiver to LOWER its gain.

Essentially, an amplifier is built to only dissipate "so much heat". Heat is a by-product of power production. When you connect 6 ohm speakers you are asking the amp for MORE power. You "could" ask for more power than the amp can effectively cool off, rendering it to go into shutdown.

All a 6 ohm setting is for is to lower the gain, so it will produce the same amount of "safe" power. However, if you leave it alone...and make sure it never gets "too hot", you really are getting the extra power(at the brief instances you really will be asking for it) when you need it.
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post #6 of 29 Old 08-15-2011, 10:20 PM
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Quote:
Originally Posted by abumuqaatil View Post

Thanks for the reply. After running it loud for half an hour , I put my hand on the grill at the top and noticed it was only warm, but not hot, so I think its ok.

However, my next question is,

1. Will there be reduced power output If i switch the receiver to
6 ohms ? Would the sound come out cleaner perhaps ? Or would it not make a difference. ?

2. Would it be worth my while to change to 8 ohm speakers ?

Thanks in advance.

The speaker impedance is not static. Most 8 ohm nominal rated speakers will read 5-6 ohms.

Having said that, the amp output/load will vary to power the speaker's load. In the case of well built receiver/amp, the lower impedance of speaker would require increase in watt output/load from the amp.

In any case, the tolerance of amp really depends on available power from it's transformer. In most cases/rule of thumb, high current capable amps can manage low impedance speakers much better to power dynamic loads during audio playback.

Heat is one sign of amp stressing, but most obvious sign is increase in distortion which will eventually lead to clipping. Now, hard clipping will most likely damage your speakers. Most SS amps have safety features built in and will shut down before it kills itself.


Anyway, my in-law drives 4 ohm rated speakers, in 7.2 surround mode with his HK 7550HD. All 7 speakers are 4 - 6 ohms(Citation 7.2 x5 and Citation 7.3 x2), and he drives it loud without an issue. The receiver fans do kick in, however. I believe HK7550HD is only rated for 8 ohm speakers on paper. I told him to get a separate amp to drive the front 3, but he seems to be happy so far with the performance from his AVR. YMMV.
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post #7 of 29 Old 08-15-2011, 11:16 PM
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Technically, the 6 ohm switch will reduce the voltage supplied to the amplifier section. So it could conceivably limit power. Some people suggest not to use it for that reason (I am inclined to agree with them, why arbitrarily limit power?)

At reasonable playback levels, I would think the Yamaha receiver will have no problems.

One thing I thought about. Music is not like movies. It has less dynamic range. So when played loudly, the receiver will be more stressed. If you are trying to push the system really hard, lower impedance speakers could cause the receiver to overheat as mentioned above - but if it's only two channels, you are probably ok.

Your receiver has a number of protection circuits to protect itself - ideally, it shuts down if it's unhappy.

Not trying to make you nervous - as I say, you are unlikely to have issues. Just pointing out a few things about impedance.

Some people run 4 ohm speakers with no issues, which is a more difficult load than 6 ohm speakers.

"But this one goes up to 11"
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post #8 of 29 Old 08-15-2011, 11:50 PM - Thread Starter
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Thanks alot for all the informative answers :-)

I think Il just leave it be.
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post #9 of 29 Old 08-16-2011, 03:14 AM
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Quote:
Originally Posted by schan1269 View Post

MgFred has it backwards...

The amp will create more power if you LEAVE IT ALONE.

The point of a 6(or 4 ohm) setting is to tell the receiver to LOWER its gain.

Essentially, an amplifier is built to only dissipate "so much heat". Heat is a by-product of power production. When you connect 6 ohm speakers you are asking the amp for MORE power. You "could" ask for more power than the amp can effectively cool off, rendering it to go into shutdown.

All a 6 ohm setting is for is to lower the gain, so it will produce the same amount of "safe" power. However, if you leave it alone...and make sure it never gets "too hot", you really are getting the extra power(at the brief instances you really will be asking for it) when you need it.

When I look at spec sheets (my VSX-59TXi in particular), the watts per channel are higher at 6 Ohm (160 watts) than at 8 Ohn (140 watts). On my NAD stereo AMP, I changed the setting to 4 Ohm to handle the tremendous power requirements of my Ohm F speakers which can easily suck all of the power of a receiver without batting an eye......

Fred
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post #10 of 29 Old 08-16-2011, 10:04 AM
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The short answer is don't worry about it.

The ohm rating on speakers is misleading in that the impeadance is no where near constant. There will be times during normal use when the 6 ohm speaker will actually have higher impedance than the 8 ohm speaker.
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post #11 of 29 Old 08-16-2011, 10:46 AM
 
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@ MgFred...

That is all fine and dandy, however.

There are (one of) two things that happen when you change the setting from 8ohm to 6ohm(or when the receiver/amp/AVR allows for 4ohm).

1. The power supply is restricted(by reducing what it can suck off the wall, or it starts metering what it can send out).
2. The gain is lowered

The measurements of your Elite were probably measured while it was still in 8ohm mode...in short bursts. Not "for hours on end".

That is part of the FTC bull crap. FTC "power ratings" are crap filled toilet paper. The FTC does NOT have a time limit for RMS ratings. So, was the amp on for 5 minutes? 20 minutes? An hour? All day?
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post #12 of 29 Old 08-16-2011, 11:16 AM
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I thought the amplifier rule used to call for one hour at rated power, all associated channels driven. With a pre conditioning period (which was lowered at some point.)

"But this one goes up to 11"
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post #13 of 29 Old 08-16-2011, 11:19 AM
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It used to be 1 hour at 1/3 power, then measured at full-power. I have no idea if that is current.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #14 of 29 Old 08-16-2011, 11:25 AM
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I think they reduced pre conditioning to 1/4 power (which is probably reasonable for movies.) But I had not heard they removed the hour.

"But this one goes up to 11"
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post #15 of 29 Old 08-16-2011, 11:29 AM
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Quote:
Originally Posted by MichaelJHuman View Post

I think they reduced pre conditioning to 1/4 power (which is probably reasonable for movies.) But I had not heard they removed the hour.

Latest statue CEA490, requires preconditioning @ 1/8th rated power for 1 hour....
However the 1 hour can be cumulative as the AVR amplifier may cycle ON/OFF for thermal shutdown..

Just my $0.02...
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post #16 of 29 Old 08-16-2011, 11:32 AM
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Wow, only 1/8 power, and it can cycle off? Why even bother with rules anymore, heh

"But this one goes up to 11"
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post #17 of 29 Old 08-16-2011, 12:06 PM
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Quote:
Originally Posted by MichaelJHuman View Post

Wow, only 1/8 power, and it can cycle off? Why even bother with rules anymore, heh

The 1/8 power is like having only 1 channel driven (7/8) in 7.1 AVR..
No surprise since the CEA standards committee is comprised of representatives from Sony, Bose, Panasonic, Samsung..

Just my $0.02...
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post #18 of 29 Old 08-16-2011, 12:49 PM
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Quote:
Originally Posted by M Code View Post

The 1/8 power is like having only 1 channel driven (7/8) in 7.1 AVR..
No surprise since the CEA standards committee is comprised of representatives from Sony, Bose, Panasonic, Samsung..

Just my $0.02...

This is one of the reasons why I do not want to get an AVR. I hope there are more pre/pro options... preferably from HK and Denon at tangiable consumer pricing.

I have been sticking with pre + older amps from 90's for the honest power output. They were also built much better, as they seem to last all these years.
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post #19 of 29 Old 08-16-2011, 01:18 PM
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Quote:
Originally Posted by bitemymac View Post

This is one of the reasons why I do not want to get an AVR. I hope there are more pre/pro options... preferably from HK and Denon at tangiable consumer pricing.

I have been sticking with pre + older amps from 90's for the honest power output. They were also built much better, as they seem to last all these years.

That can work for the category of amplifiers..
But if one wants the latest technologies for audio, video and connectivity he will need to purchase an AVR...

Just my $0.02...
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post #20 of 29 Old 08-16-2011, 03:59 PM
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Quote:
Originally Posted by schan1269 View Post
MgFred has it backwards...

The amp will create more power if you LEAVE IT ALONE.

The point of a 6(or 4 ohm) setting is to tell the receiver to LOWER its gain.

Essentially, an amplifier is built to only dissipate "so much heat". Heat is a by-product of power production. When you connect 6 ohm speakers you are asking the amp for MORE power. You "could" ask for more power than the amp can effectively cool off, rendering it to go into shutdown.

All a 6 ohm setting is for is to lower the gain, so it will produce the same amount of "safe" power. However, if you leave it alone...and make sure it never gets "too hot", you really are getting the extra power(at the brief instances you really will be asking for it) when you need it.
This. AVRs already have a number of overheat mechanisms. The only purpose of the 6/4 ohm switch is to please regulatory agencies. You are not going to be able to actually overheat it, and even if you were, I'd rather put the receiver at jeopardy than the speakers. If you google this topic there was a long blog post by a former product developer on this topic confirming pretty much exactly what schan said.
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post #21 of 29 Old 08-16-2011, 05:41 PM
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Quote:
Originally Posted by 2girls1up View Post
The only purpose of the 6/4 ohm switch is to please regulatory agencies. You are not going to be able to actually overheat it, and even if you were, I'd rather put the receiver at jeopardy than the speakers.
Incorrect...
Its there to protect the receiver from overload and thermal shutdown by limiting the available current..
Going from 8 Ohms to 4 Ohms, doubles the current and given the lower rated components used in price-point AVRs it protects the AVR from output stage failure..

Just my $0.02...
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post #22 of 29 Old 08-16-2011, 06:25 PM
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Yamaha lowers the supply voltage to the amplifier section. Therefore, lower max power. But more chance of clipping. Pretty simple. Which is why you might not want to use it, because you can accomplish the same thing by limiting the volume, but are less likely to clip on the peaks.

"But this one goes up to 11"
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post #23 of 29 Old 08-16-2011, 06:28 PM
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So if I have 6 ohm speakers, I should leave my receiver set to the 8 ohm setting?

Quote:
Of course, I got it modified with the TK-427, which cheeks it up another, maybe, 3 or 4 quads per channel.
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post #24 of 29 Old 08-16-2011, 06:57 PM
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Quote:
Originally Posted by MrEastSide View Post

So if I have 6 ohm speakers, I should leave my receiver set to the 8 ohm setting?


The simple analogy would be ..... trying to drive a 200W rated speakers with 100W capable amp. Of course, you can drive the speakers, but can't drive it at the speakers higher potential.

Also, when amp is driven beyond it's capability, the amp will give out as it will try to put out the last drop of juice into the hungry speakers before the amp fails/shuts down/clips.

Many people drive higher wattage rated speakers with lower power rated amps all the time. I don't see people worrying too much about that, and why would driving miss matched ohm rated speakers/amp be any different? Same risk involved only when pushed beyond the capability of the weakest link.

BTW, if your amp/AVR is able to switch the ohm settings to match the rated speaker impedance, I would use it. It was designed for such purpose.
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post #25 of 29 Old 08-16-2011, 07:47 PM
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Quote:
Originally Posted by MrEastSide View Post

So if I have 6 ohm speakers, I should leave my receiver set to the 8 ohm setting?

The AVR will output more power and higher current in the 8 Ohms switch position.. This will provide lower THD, higher dynamic range and better sonic performance.

The key to protecting the loudspeakers is to use common sense, use minimum EQ and operate the volume level so there is no audible distortion..

Just my $0.02...
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post #26 of 29 Old 08-16-2011, 08:29 PM
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I guess I assumed that the lower you put the receiver setting at, the more power you got. But, now I realize it's meant to actually protect things, by dropping it lower.

Quote:
Of course, I got it modified with the TK-427, which cheeks it up another, maybe, 3 or 4 quads per channel.
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post #27 of 29 Old 08-16-2011, 09:54 PM
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Quote:
Originally Posted by MrEastSide View Post

I guess I assumed that the lower you put the receiver setting at, the more power you got. But, now I realize it's meant to actually protect things, by dropping it lower.

Yes try to run new receivers at the highest ohm setting which is usually the default. If it won't play at all or gets too hot and keeps shutting down set it to the lower setting. On some brands 4 is the lower setting and some brands 6 is the lower setting so just saying "I put it on 6" is not always clear. The higher number will have more power and play louder all brands. I recently connected 3 4ohm and 2 8ohm speakers to a $1500 list receiver. It would play only to -16 volume (not very loud) before shutting down immediately every time on the higher setting. I switched to the lower ohm setting and it played to full volume no problem. Full volume wasn't super loud but sounded still quite clean. This setting clearly does make a difference in power output.
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post #28 of 29 Old 08-16-2011, 10:43 PM - Thread Starter
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I play movies at reference levels some times,
Now reading all the above, Im scared of the receiver clipping. Its a fairly new model Sep 2010 I think. Do you guys think it would actually shut itself down before clipping ? or would it just clip.

Is it even safe to go into the gains area past 0db? I cant hear any distortion, but it does tend to get a little on the "bright" side of sound. BTW i do this just for testing purposes.

I wonder if there are people that run these things past reference limits. Well.. I guess it was designed to... hmmm
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post #29 of 29 Old 08-16-2011, 11:36 PM
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Quote:
Originally Posted by abumuqaatil View Post

I play movies at reference levels some times,
Now reading all the above, Im scared of the receiver clipping. Its a fairly new model Sep 2010 I think. Do you guys think it would actually shut itself down before clipping ? or would it just clip.

Is it even safe to go into the gains area past 0db? I cant hear any distortion, but it does tend to get a little on the "bright" side of sound. BTW i do this just for testing purposes.

I wonder if there are people that run these things past reference limits. Well.. I guess it was designed to... hmmm


One way to keep the load off the amp is by using a sub/s and send all the low frequency work there. In stereo mode, you should be able to drive the loud speakers louder safely as your amp transformer should have more reserved power to run in stereo mode even as full size speaker. However, if you're not confident about the AVR, then just set all speakers as small and XO low frequency from all your speakers to the subs. This should save your amp/avr and lower the risk of ruining your audio gear.

I have set of old Infinity Kappa 8.1 for my main driven by HK signature 1.5 putting out 350w/ch. @ 4 ohm, but it is set as small and xo at 100 hz. It blends nicely with my two 12" subs in movie surround mode. But I do set them as full size in stereo mode for music w/out the subs.

Even for stereo music, subs can be tuned to blend in nicely with the main speakers set as small.

BTW, speakers turning to the bright side is also a sign of fatigue, insufficient power, or just a coloration from the amp.
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