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I just found out that all my speakers have an impedance of 6 ohms and that my receiver has an impedance selector witch goes for a “8 ohms mode†and a “6 ohms modeâ€.


So, I immediately switch to the “6 ohms modeâ€, and I didn’t notice any obvious change in the sound, but since I’m running this setup since about 3 years on the “8 ohms modeâ€, now I’m wondering if I could have damaged my equipment by not using the right mode? What’s the purpose of the mode? Should I notice any differences in sound when switching? Is it better to leave it at 8 ohms as stated by this review: http://www.audioholics.com/productre...-V4600HTp2.php (note, my receiver is a Yamaha, but no the one reviewed)?


I’m a little confused; feedback on this would be much appreciated.


Thanks in advance! :)
 

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I'd say you are fine leaving it at 8 ohms. I tried experimenting with the 4/8 ohm switch on an avr I recently owned and found no difference either with either 8 ohm or 4 ohm speakers . Audioholics called that one right.
 

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I had a Sony STR-G3 receiver with a 4/8 ohm switch. For normal listening, I could never tell a difference. However, when playing really loud, it seemed to me the bass didn't hit quite as hard with the switch in the 4 ohm position (speakers were rated @ 4 ohms) so I just left it in the 8 ohm position. A friend is still using it years later without any problems except that darn egg remote just took some getting use to. Pretty cool at the time though....



Well, now to actually answer the question. I think the purpose is to limit the current in the output stages to theoretically keep from frying the amp with a low impedance load. Thought I read somewhere that it was/is necessary to pass UL testing due to heat generation. Don't know that to be a fact though, just something that sticks in my head from way back.
 

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Quote:
Originally Posted by whoaru99
Well, now to actually answer the question. I think the purpose is to limit the current in the output stages to theoretically keep from frying the amp with a low impedance load. Thought I read somewhere that it was/is necessary to pass UL testing due to heat generation. Don't know that to be a fact though, just something that sticks in my head from way back.
This has been my understanding also.
 

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Huh? Why leave it at 8Ω? Set it to 6Ω and be happy. :)


If (as I suspect) it's a parameter for the overcurrent protection circuit, you're improving your protection. Won't have any effect on the sound.
 

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Quote:
Originally Posted by DMF
Huh? Why leave it at 8Ω? Set it to 6Ω and be happy. :)

Won't have any effect on the sound.


Don't bet on it not having a effect on the sound.


As per audioholics, it is very possible that setting it to the lower setting can have a negative effect on the sound.

http://www.audioholics.com/productre...ceiver-p2.html



"Impedance Selector Switch


I recommend the "Minimum 8 ohms" setting even for 4 ohm speakers of moderate efficiency (>89dB SPL). Yamaha includes a" 6 ohm" setting to satisfy UL as well as easing consumer concerns about driving low impedance loads. These switches step down voltage feed to the power sections which can limit dynamics and overall fidelity. My advice is to keep the switch set to "Minimum 8 ohms" regardless of the impedance of your speakers and ensure proper ventilation of the Receiver."







So.... If there has been no problems with it set at 8ohms, then he should continue to use the 8ohm setting.
 

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Quite so. The switch introduces voltage limiting so that when driving lower nominal impedance speakers under demanding conditions, the amp doesn't try to deliver the current that would be needed to satisfy the speaker's impedance at that point. E=iR and all that, right? The net result of all this, or one of them anyways, is to avoid the excessive temperatures that could result which could lead to unintended consequences like frying your output transistors due to thermal considerations. I'm not so sure that providing adequate ventilation, short of heat-sinking the area and blowing a fan on it, is any sort of guarantee against this when driving lower impedance speakers at the 8 ohm setting.


Some background on this whole thing. Sometime back in the early 90's, maybe it was late 80's, various companies, decided to not rate some of their amps or receivers into 4 ohm loads. This was a direct consequence of using rather small power supplies and hybrid output amps that have various degrees of lousy performance when trying to drive low impedance loads. In a sense, this is an engineering decision that is no doubt strongly influenced by marketing and the usual bean counters.


There are numerous reasons why you did not detect any differences.


1) the volume levels you listen to doesn't tax your receiver under any conditions.

2) the speakers sensitivity

3) where you sit in relation to your speakers

4) room size

5) your use of a sub and where it's crossed over

6) dumb luck

7) some combination of the above


Myself, I'd just switch it over to the lower setting and then just forget about it. If you're having problems driving the speakers, I think it's just preferable to get an amp or receiver that does the job instead of defeating the protection mechanisms as a kludge. Provided you like the speakers that is.
 

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John, if you leave it set at 8Ω and overdrive the power supply, it will clip and possibly alter the sound *permanently*. Better to apply voltage limiting.
 

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Quote:
Originally Posted by DMF
John, if you leave it set at 8Ω and overdrive the power supply, it will clip and possibly alter the sound *permanently*. Better to apply voltage limiting.
He said he has used it for 3 years so far set at the 8ohms setting, and it did not damage anything. So I doubt that it will all of a sudden "*permanently*" damage it now. And I have operated more than a few this way also with no damage. Granted with some receivers and some hard to drive 4ohm speakers it may be a problem.


Like the reviewer at Audioholics said, as long as the speakers are reasonably efficient it should not be a problem. And if you do have speakers where it is a problem, then you can set it for the lower setting.
 

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I thought I would pipe in to clarify a few issues surrounding the Yamaha Impedance Selector switch since my review was referenced in this thread.


In actuality setting this switch to the LOW setting “6 ohms or more†can cause more amplifier clipping when being driven hard, NOT less. By stepping the voltage down on the receiver, you risk clipping your amp, especially during transients, and damaging your speakers if continuously overdriving them.


The reason for the “LOW†setting is to make UL happy. By lowering the rail voltage, they now test the amp at lower “unclipped†power and hence the receiver will dissipate less heat and meet their requirement.


One of the reasons you don’t see this switch on separate power amps, is they usually don’t have UL approval marked on them. Hence they don’t have to meet the UL heat dissipation requirements that receiver manufacturers must adhere too. The other more obvious reasons include what others in this thread pointed out about separate amps having larger power supplies, and bigger heat sink area.


If you find the internal receiver amps inadequate for your application, by all means preamp out the receiver in favor of a dedicated amp. Don’t however use the “LOW†setting as a means to limit amp clipping when in fact it can only increase it.


I recommend reading my RX-V4600 review where I go into greater detail and even show measurements of both settings.


Here is a link to my editorial note on Impedance Selector Switches .
 

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Good advice for sure from Gene. In an earlier article on connecting 4 ohm speakers to an 8 ohm receiver or amplifier you stated that these switches step down voltage feed to the power sections which limit dynamics and overall fidelity. While the dangers of clipping are clear to me why do you say it limits dynamics and fidelity?
 

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The 8 Ohm switch position permits the highest voltage and current output capability from that respective brand/model.. and dynamic performance..

Otherwise the amplifier could likely damage itself while trying to deliver the required voltage/current..


Basic issue is cost..

Present AVRs have more amplifier channels than previous versions yet the market is demanding prices to decrease for AVRs as they have in PCs.. DVD players.. flat panel displays..

But these have decreased in cost mainly due to improved silicon and/or key components integration while the market consumption increased..

An analog AVR has little possibility for additional integration..

So other internal components/circuits are being decreased in cost by downsizing...


Additionally the marketing groups are applying more creative specs to give the impression that they provide more for less ....

when usually the opposite is true... :rolleyes:


Going forward..

Newer digital integrated AVR designs promise better performance @comparable cost and these are now starting to appear in the market...
 

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Quote:
While the dangers of clipping are clear to me why do you say it limits dynamics and fidelity?
Amp clipping, especially for solid state amps, doesn't sound all that great. Since lowering the rail voltage will result in more amp clipping this can affect fidelity and also reduce dynamic range. In addition, though its been awhile since I have seen them, some impedance switches physically raise the output impedance of the amp which can adversly affect frequency response linearity when driving reactive loudspeaker loads and damping factor.
 

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thanks for the clarification.
 

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There's one exception. The Pioneer VSX2014i triples its power in 2ohm when set to 6ohms. Since it shares its amp with the 1014/1015 I guess the same would be true for them as well
 

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Gene, perhaps I overlooked it, but did you guys also run any kind of internal temperature measurements of the unit driving both 8 and 4 ohm loads with the selector in the 8 and 6 ohm positions, perhaps measuring the temp of the output transistors?
 

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Gene, thanks for stopping by.

Quote:
Originally Posted by Gene DellaSala
In actuality setting this switch to the LOW setting “6 ohms or more†can cause more amplifier clipping when being driven hard, NOT less. By stepping the voltage down on the receiver, you risk clipping your amp, especially during transients, and damaging your speakers if continuously overdriving them.
That doesn't follow without additional information. Does dropping the rail voltage not also lower the voltage gain? Does it affect the main power capacitor .. er.. capacity? Or the recharge rate?


Seems to me that reducing rail voltage necessarily reduces the current demanded by the load, thus increasing the ability of the power supply to meet the demand and reducing the incidence of clipping. Clipping is, after all, induced by the inability of the power supply to produce the current demanded by the load at a given output voltage.
 

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Quote:
Gene, perhaps I overlooked it, but did you guys also run any kind of internal temperature measurements of the unit driving both 8 and 4 ohm loads with the selector in the 8 and 6 ohm positions, perhaps measuring the temp of the output transistors?
Not really, though I did on my RX-Z9 review since it ran so darn hot even steadystate. I wanted to verify with Yamaha that it was operating within spec, which it was.


Quote:
Does dropping the rail voltage not also lower the voltage gain? Does it affect the main power capacitor .. er.. capacity? Or the recharge rate?
Dropping the rail voltage is independent of closed loop circuit gain in the system. You are simply choking the potential of the amp by doing this. Please review the data on page2 of my RX-V4600 review and you will see the power reduction for both 8 ohm and 4 ohm loads when the receiver is set to the "LOW" setting.


Again, UL looks to test an amp at max power unclipped, say 1% (not sure on exact figure). By reducing the rail voltage, the amp will clip sooner (or have less potential) and thus dissipate less heat to meat (LOL, meet) their heat dissipation requirements.

Quote:
Clipping is, after all, induced by the inability of the power supply to produce the current demanded by the load at a given output voltage.
Its still related to voltage. If the amp cannot swing enough voltage to hit the power you are trying to reach, the amp will clip. For example, it takes 40Vrms to produce 200 watts into an 8 ohm load. In order to do this effectively, you need a +- rail of about 40*sqrt(2) + 5 = +-61.6V. Let's say the receiver has this available in the "high" impedance setting. Now flip it to the "LOW" setting and the rail voltage drops 15% or so to say 52V. You can no longer hit that 200watt rms # unclipped so you have to scale the volume level down proportionally. Thus you now test the amp at 170 watts instead of 200 watts. As a result, the amp dissipates less heat and you get your certification :)



On the flip side, if you have a 1000V rail voltage, but its only rated at 100V when driven a 1K ohm load, then yes trying to drive 100V into 8 ohms would cause the voltage to sag since the power supply cannot source the necesary current demand to power that load.


I don't wish to hiijack this thread so you have any further questions about this topic, feel free to email/PM me. Thanks and I hope this helps.
 

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Quote:
Originally Posted by Gene DellaSala
Not really, though I did on my RX-Z9 review since it ran so darn hot even steadystate. I wanted to verify with Yamaha that it was operating within spec, which it was.
Just curious, what kind of actual outer case temperatures are considered normal for the RX-Z9?

Because like you say, they run damn hot to the touch even just at idle.
 
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