A/V Receiver Impedance Selector Switch

[Trebdp83]

It’s still a heat switch. When running 4 ohm speakers, set it at 6 ohm or higher in winter and back to 4 ohm in summer.

 

[PENG]

Well I was talking about that...
Low Impedance (Z) Mode .... loudspeakers rated below 8-ohms. (This mode limits the output voltage, and therefore the maximum current any given speaker can demand of it).
High Impedance (Z) Mode ... loudspeakers rated at 6-ohms or higher....

And I suppose that would be right...
Low Impedance (Z) Mode .... loudspeakers rated below 6-ohms. (This mode limits the output voltage, and therefore the maximum current any given speaker can demand of it).
High Impedance (Z) Mode ... loudspeakers rated at 8-ohms or higher....

That's splitting hairs though.. The nominal impedance figures should be used as a general guide/approximation. For more details one would have to look at the impedance vs frequency curve. For amplifiers, owner's manual, typically simply go with 4, 6 and 8 ohms only when refer to their output ratings and/or impedance selector settings.

 

[dlaloum]

Both my Onkyo TX-SR876 and Integra DTR 70.4 had the "6ohm+ / 4ohm" switch.

My speakers drop down below 2 ohm at both the high end and at the woofer/midrange crossover.

Under all circumstances, the amps sounded best on the 6ohm+ setting - it may have run a bit warmer - but the sound was definitely better/cleaner, and it never seemed to drive the amps into their nanny mode (if pushed too hard they self protect by automatically placing themselves in the 4 ohm mode).

Given my experience with speakers providing a difficult load to the amp, I cannot fathom why they bother with that switch - all it ever does, is degrade the sound... with the sort of low impedance speakers that match the 4 ohm tag, it neither protects the receiver, nor improves the sound.

P.S. I even ran the Receivers in bridged mode for front L/R, which effectively meant the amps were seeing loads below 1 ohm (it halves the effective impedance!) - and still the amps ran fine. (but they sounded better in standard mode, rather than in bridged mode - no surprises... the sub 1ohm load pushed the amps a bit too hard!)

 

[lovinthehd]

Both my Onkyo TX-SR876 and Integra DTR 70.4 had the "6ohm+ / 4ohm" switch.

My speakers drop down below 2 ohm at both the high end and at the woofer/midrange crossover.

Under all circumstances, the amps sounded best on the 6ohm+ setting - it may have run a bit warmer - but the sound was definitely better/cleaner, and it never seemed to drive the amps into their nanny mode (if pushed too hard they self protect by automatically placing themselves in the 4 ohm mode).

Given my experience with speakers providing a difficult load to the amp, I cannot fathom why they bother with that switch - all it ever does, is degrade the sound... with the sort of low impedance speakers that match the 4 ohm tag, it neither protects the receiver, nor improves the sound.

P.S. I even ran the Receivers in bridged mode for front L/R, which effectively meant the amps were seeing loads below 1 ohm (it halves the effective impedance!) - and still the amps ran fine. (but they sounded better in standard mode, rather than in bridged mode - no surprises... the sub 1ohm load pushed the amps a bit too hard!)

The switch isn't about performance, it's about regulatory compliance....

 

[richardjhy]

I have just finished up a comprehensive article dealing with Impedance Selector switches found on many A/V receivers. I'd like to get your feedback on how you set these and why. I think everyone will find my article quite informative and shocking (no pun intended).

The High Setting is usually the factory default and pertains to speakers rated above 6 ohms.

The Low Setting pertains to speakers under 6 ohm impedance.

Read the Article

I have Yamaha RX-V1070 and DSP A1000. Both of them have a speaker impedance switch (6/8 ohms) at the back, however, rail voltages are completely opposite to what you described in the article. When I switch to low impedance, the rail voltage s are higher. Take RX-V1070 as an example, rail voltages are +/- 58v for 6 ohm speakers and less than +/- 50 v for 8 ohm speakers.

 

[gene]

I have Yamaha RX-V1070 and DSP A1000. Both of them have a speaker impedance switch (6/8 ohms) at the back, however, rail voltages are completely opposite to what you described in the article. When I switch to low impedance, the rail voltage s are higher. Take RX-V1070 as an example, rail voltages are +/- 58v for 6 ohm speakers and less than +/- 50 v for 8 ohm speakers.

That doesn't make sense based on ANY of the power testing I've done on Yamaha receivers over the last 20 years. They ALWAYS produce LESS power in the low impedance mode. I would double check this switch setting if I were you and restart the power each time you do. The low impedance mode goes to a different tap on the transformer which typically lowers the rails.

 

[dlaloum]

On Onkyo/Integra/Pioneer AVR's the 4 ohm "switch" (it's a software setting) - puts the amp into a lower power mode, in actual fact the default 8 ohm setting on these is the better setting for all speakers!

Also many AVR's have a fairly sensitive "nanny" circuit, that puts the amps into a low power safety mode if it feels it is overdriven... the Onkyo ones requires a reset to get out of it! - But I have yet to meet anyone who has experienced this in the real world, as opposed to on a test bench

 

[Trebdp83]

If the choice is between random noisy relay clicks in a hot receiver or silent running in a cool one, I’ll leave my Onkyos in 4 ohm mode. There is no degradation in sound using 4 ohm mode that I have experienced.

I use a crossover and subs with my 4 ohm speakers. I’ve also run them at Full Band with 6+ ohm setting at high volume for kicks. If anybody needs that much power and volume, they need hearing aids and/or separates. I prefer an AVR that runs cool without the annoying relay clicks that are famous from Onkyo that do not occur at all in 4 ohm mode. But, that’s just me, I’m sure.

You’d think I’d switch it back, it being winter again and all. Maybe I’ll swap out the Yamaha til’ spring. But, that little one eyed f#%ker will leave a mark on you after some high volume movie watching in 8 ohm mode. Maybe I’ll split the difference and pick up that Denon X4700H. Is it still on sale? I wouldn’t mind connecting some older analog devices, again.

 

[Trell]

If the choice is between random noisy relay clicks in a hot receiver or silent running in a cool one, I’ll leave my Onkyos in 4 ohm mode. There is no degradation in sound using 4 ohm mode that I have experienced.

I use a crossover and subs with my 4 ohm speakers. I’ve also run them at Full Band with 6+ ohm setting at high volume for kicks. If anybody needs that much power and volume, they need hearing aids and/or separates. I prefer an AVR that runs cool without the annoying relay clicks that are famous from Onkyo that do not occur at all in 4 ohm mode. But, that’s just me, I’m sure.

You’d think I’d switch it back, it being winter again and all. Maybe I’ll swap out the Yamaha til’ spring. But, that little one eyed f#%ker will leave a mark on you after some high volume movie watching in 8 ohm mode. Maybe I’ll split the difference and pick up that Denon X4700H. Is it still on sale? I wouldn’t mind connecting some older analog devices, again.

I’ve used 4 Ohm speakers in a 5.x setup since before I bought a Denon AVR-X4200W seven years ago. Still works fine but for most of that time I’ve had fans on top of it. I haven’t used the dreaded impedance switch either.

I do use the Eco mode with lower power consumption at below -30 dB on the calibrated volume scale. Most of my listening is at or below that volume.

 

[richardjhy]

That doesn't make sense based on ANY of the power testing I've done on Yamaha receivers over the last 20 years. They ALWAYS produce LESS power in the low impedance mode. I would double check this switch setting if I were you and restart the power each time you do. The low impedance mode goes to a different tap on the transformer which typically lowers the rails.

I measured more than twice. It make sense to me.
RX-V1070 rated 110wpc / 135wpc (8ohm/6ohm) for front and center channels. Power output higher for 6ohm speakers means the rail voltages for it should be higher.

 

[dlaloum]

I measured more than twice. It make sense to me.
RX-V1070 rated 110wpc / 135wpc (8ohm/6ohm) for front and center channels. Power output higher for 6ohm speakers means the rail voltages for it should be higher.

Hmmm - using the handy calculator

Speaker Power Calculator | Same Sky

Same Sky' speaker power calculator can be used to quickly solve for a speaker’s power, voltage, and impedance ratings when two values are known.

www.cuidevices.com

135W @ 6 ohm = 80.5V
110W @ 8 ohm = 83.9 V

Nope - roughly the same voltage out max - I doubt there is any difference in the V rails

10V @ 8ohm = 1.5W
10V @ 4 ohm = 3W
10V @ 2 ohm = 6W

But to be able to deliver that theoretical doubling of power out as impedance drops, the power supply has to be able to provide the massive current needed - and the power amp circuits need to be able to handle that current... Most amps can't do that - it's a theoretical ideal.

 

[gene]

I measured more than twice. It make sense to me.
RX-V1070 rated 110wpc / 135wpc (8ohm/6ohm) for front and center channels. Power output higher for 6ohm speakers means the rail voltages for it should be higher.

You're confusing impedance of a speaker vs the switch setting. Of course you will get more power at 6 ohms than 8 ohms if the voltage is held constant. Basic ohms law. The amp is supplying more current.

Flipping the impedance switch to 6 ohms will NEVER produce more power for any load the AVR drives for the reasons I stated in my article and based on test data I collected for multiple products with this feature for the past 2 decades. If you like to starve your speakers of power, use the low setting. No worries on my end but please don't report false information on this forum as fact.

 

[richardjhy]

That doesn't make sense based on ANY of the power testing I've done on Yamaha receivers over the last 20 years. They ALWAYS produce LESS power in the low impedance mode.

The attached screenshot is RX-V1070 transformer schematic diagram from its service manual. It clearly indicates that rail voltage will be higher in lower impedance mode (6ohm, more secondary wiring) than higher impedance mode (8ohm).
Don't tell me that you can't read schematic diagram.

 

[Trell]

The attached screenshot is RX-V1070 transformer schematic diagram from its service manual. It clearly indicates that rail voltage will be higher in lower impedance mode (6ohm, more secondary wiring) than higher impedance mode (8ohm).
Don't tell me that you can't read schematic diagram.View attachment 59233

So you claim that the infamous impedance switch has no effect on the output, despite Gene’s testing?

 

[cpp]

owner's manual, typically simply go with 4, 6 and 8 ohms only when refer to their output ratings and/or impedance selector settings.

That's how my older Denon 4311ci has the settings

 

[dlaloum]

V=IR (Current X Resistance) - so as resistance drops, current needs to rise to maintina voltage

Speakers / amps are voltage devices - that is to say the Sound Pressure Level is proportional to the voltage.

SPL specs are commonly measured at 2.83V at a distance of 1m from the speaker

for 8 ohm speakers that would be 2.83/8= 0.35375 Amps or/and W=VA so Power is 0.35375 * 2.83 = 1 Watt
(for my speakers that would be 86db/wm)

Now what if that speaker is a 4 ohm speaker - 2.83/4 = 0.7075 Amps, W= 0.7075*2.83 = 2 Watts

Same voltage - requires twice the current and twice the power output

At some point the power supply reaches its limit in terms of current (usually before the power limits of the power amp circuits are reached!)

for 40V output 8ohm ... 40/8=5 amps W=5x40 = 200W
for 40V output 4 ohm... 40/4=10 amps W=10x40 = 400W

Basically - with lower impedance speakers, the receiver had to provide double the current to keep the voltage/loudness at the same level (which results in double the power - for the same SPL)

More current means more heat ... and typical AVR's will max out at around 7amps

Once you hit the current limit of the power supply, the voltage starts to sag - you start to get various interesting audible effects... compression, congestion of soundstage etc...
Also, if the power supply is not adequately protected, you can get a literal melt down, release the "magic smoke".

So, to protect the system, designers put nanny circuits, and/or hard switches for lower impedance speakers.

Typically the "switch" simply constrains the power supply to a lower maximum voltage... which results in lower current output (typically gauged to be within the power supplies long term capability - ie: it won't overheat / melt down / fail ) - which in turn results in lower max power output. The Nanny circuits similarly just drop the supply voltage to the power amp circuits.

Top of the Line AVR's of 15 years ago, frequently weighed 30kg - this was mostly due to the massive transformer, giving them higher power, but more importantly substantially more current - meaning they worked better than most current AVR's with low impedance speakers. - my old TX-SR876 could handle my 1.6 ohm speakers well, my current Integra DRX 3.4 can't (the former weighed 30kg, the latter 10kg... both are class AB difference is almost entirely in the transformer)

In terms of whether the power output rises or falls - is a consequence of all the above...

Pretty much all current amps have more power at 4 ohm than at 2ohm (cos for the same voltage output, it would provide double the power, if not current constrained) - but then look at amps measured at 2ohm

The Quad 606 is a 135W amp @ 8ohm, rises substantially into 4 ohms - 180W (notice it does not double - it has reached its current limit...) - and having reached its current limit, the max voltage it can support (cleanly!) then drops off dramatically as impedance drops further - for 2 ohm we are down at just under 90W.

Inveresely - that Quad 606 - can drive a 2ohm speaker to the equivalent loudness of a 22.5W amp into an 8 ohm equivalent speaker (it's max voltage/loudness into 2 ohm is severely constrained).

The nice thing about the Quad is that although constrained, it still keeps going, remains stable, and sounds good (as long as you are not asking massive SPL's out of it!)
Most amps, and most AVR's simply start to sound like rubbish into such 2 ohm or sub 2 ohm loads - and if not adequately protected, may well self destruct.

 

[PENG]

V=IR (Current X Resistance) - so as resistance drops, current needs to rise to maintina voltage

Speakers / amps are voltage devices - that is to say the Sound Pressure Level is proportional to the voltage.

SPL specs are commonly measured at 2.83V at a distance of 1m from the speaker

for 8 ohm speakers that would be 2.83/8= 0.35375 Amps or/and W=VA so Power is 0.35375 * 2.83 = 1 Watt
(for my speakers that would be 86db/wm)

Now what if that speaker is a 4 ohm speaker - 2.83/4 = 0.7075 Amps, W= 0.7075*2.83 = 2 Watts

Same voltage - requires twice the current and twice the power output

At some point the power supply reaches its limit in terms of current (usually before the power limits of the power amp circuits are reached!)

for 40V output 8ohm ... 40/8=5 amps W=5x40 = 200W
for 40V output 4 ohm... 40/4=10 amps W=10x40 = 400W

Basically - with lower impedance speakers, the receiver had to provide double the current to keep the voltage/loudness at the same level (which results in double the power - for the same SPL)

More current means more heat ... and typical AVR's will max out at around 7amps

Once you hit the current limit of the power supply, the voltage starts to sag - you start to get various interesting audible effects... compression, congestion of soundstage etc...
Also, if the power supply is not adequately protected, you can get a literal melt down, release the "magic smoke".

So, to protect the system, designers put nanny circuits, and/or hard switches for lower impedance speakers.

Typically the "switch" simply constrains the power supply to a lower maximum voltage... which results in lower current output (typically gauged to be within the power supplies long term capability - ie: it won't overheat / melt down / fail ) - which in turn results in lower max power output. The Nanny circuits similarly just drop the supply voltage to the power amp circuits.

Top of the Line AVR's of 15 years ago, frequently weighed 30kg - this was mostly due to the massive transformer, giving them higher power, but more importantly substantially more current - meaning they worked better than most current AVR's with low impedance speakers. - my old TX-SR876 could handle my 1.6 ohm speakers well, my current Integra DRX 3.4 can't (the former weighed 30kg, the latter 10kg... both are class AB difference is almost entirely in the transformer)

In terms of whether the power output rises or falls - is a consequence of all the above...

Pretty much all current amps have more power at 4 ohm than at 2ohm (cos for the same voltage output, it would provide double the power, if not current constrained) - but then look at amps measured at 2ohm

The Quad 606 is a 135W amp @ 8ohm, rises substantially into 4 ohms - 180W (notice it does not double - it has reached its current limit...) - and having reached its current limit, the max voltage it can support (cleanly!) then drops off dramatically as impedance drops further - for 2 ohm we are down at just under 90W.

Inveresely - that Quad 606 - can drive a 2ohm speaker to the equivalent loudness of a 22.5W amp into an 8 ohm equivalent speaker (it's max voltage/loudness into 2 ohm is severely constrained).

The nice thing about the Quad is that although constrained, it still keeps going, remains stable, and sounds good (as long as you are not asking massive SPL's out of it!)
Most amps, and most AVR's simply start to sound like rubbish into such 2 ohm or sub 2 ohm loads - and if not adequately protected, may well self destruct.

The Onkyo 876 weighs 24.1 kg not 30 kg. Yes it is still heavy for a 7.1 avr.

 

[Trell]

Most amps, and most AVR's simply start to sound like rubbish into such 2 ohm or sub 2 ohm loads - and if not adequately protected, may well self destruct.

Sub 2 ohm consumer speakers I put into the “badly designed” category.

 

[richardjhy]

So you claim that the infamous impedance switch has no effect on the output, despite Gene’s testing?

No.

He claimed that "They ALWAYS produce LESS power in the low impedance mode ", but it seems not applying to Yamaha RX-V1070. I believe that RX-V1070 should be able to produce MORE power in lower impedance mode.

 

[richardjhy]

BTW, RX-V1070 weights more than 40lbs with a massive transformer. It handles a pair of 4ohm Altec Lansing speakers easily.