A/V Receiver Impedance Selector Switch

What setting is your receivers impedance switch on?

  • high setting (factory default)

    Votes: 51 71.8%
  • Low setting

    Votes: 6 8.5%
  • My receiver doesn't offer this feature

    Votes: 14 19.7%

  • Total voters
    71
KenM10759

KenM10759

Audioholic Samurai
My NAD T758 doesn't have the switch, and not one word in the manual about the subject. My KEF R500's are nominally rated to 8Ω by KEF, though even they admit that the speakers dip to as low as 3.2Ω while working. The receiver does run warm, and definitely gets hotter the louder I run it.

I think I need to bin the NAD and look for system separates that can handle the load better. ;)
 
N

nutsoap

Audiophyte
With my Yamaha A-s301 running 2 pairs of 8 ohm speakers (KEF Q500 and Athena LS-50B) simultaneously with the A+B should I still have the switch to "high"?

I am assuming the speakers are running in parallel and would then equal a 4ohm load and that high is still the way to go but I see so much conflicting advice and not much on if "high" is still the way to go for A+B.
 
gene

gene

Audioholics Master Chief
Administrator
Thank you for taking the time to post this. I'm afraid I'm still confused. :confused:

Here's what I got:

Yamaha R-S500
Klipsch Forte IIs - A
Klipsch AW-525 - B (outdoor speakers)
SVS SB-1000 sub

So, low or high? Switch is currently set to high.

Thanks for any insight you can provide.
What is confusing about ALWAYS using,the HIGH setting regardless of your speaker impedance?
 
C

coaxial88

Audiophyte
Hello good day ; i am audio enthusiast I have a small question;

I have a Pioneer ELITE SC-07 Receiver, with 7.1 channel output, I just got these totem tribe 3, a 4-ohm load speaker.
I was wondering if I could connect the surround back channel outputs to the tweeter input of the speaker and the main L/R to the bass input in a Bi-Amp Configuration Without Damaging the speakers or the Receiver? My concern is the OHM load.
This configuration is allowed by the receiver ; one goes into the menu settings and changes it to bi-amp.


if you could advice I would be thankful
 
everettT

everettT

Audioholic Ninja
You should add an outboard amp for the front 3. Here is the write up and concerns about the original ice amps in the pioneers.

http://www.audioholics.com/av-receiver-reviews/pioneer-sc-07


Hello good day ; i am audio enthusiast I have a small question;

I have a Pioneer ELITE SC-07 Receiver, with 7.1 channel output, I just got these totem tribe 3, a 4-ohm load speaker.
I was wondering if I could connect the surround back channel outputs to the tweeter input of the speaker and the main L/R to the bass input in a Bi-Amp Configuration Without Damaging the speakers or the Receiver? My concern is the OHM load.
This configuration is allowed by the receiver ; one goes into the menu settings and changes it to bi-amp.


if you could advice I would be thankful
 
H

hotrabbitsoup

Audiophyte
Sorry to bring up an old thread on my first post but the topic and related article are the reason I joined up.

Without knowing the specifics of the transformers used in our receivers and amps I am assuming that the transformer secondary that results in lower voltage in the power supply (the '4 ohm' option) is made up of conductor that is actually thicker than the winding used for the '8 ohm' option. The arguments in the impedence switch article make sense but another way of ensuring 4 ohm stable thermal performance is to use beefier conductor in the transformer core. If that secondary is wound with thicker wire you get less turns and hence the lower voltage output but the thicker conductor will survive for longer under high current draw as the windings heat up from I^2R losses. Anyone have any parts transformers from receivers that can check or know of off the shelf transformer part numbers used in AVRs that I can check ? It would really be a waste of time if the 4ohm winding in the transformer had the same current rating as the 8 ohm winding which seems to be what Gene's arguing in the article from 2010.... oh my, i'm late to the party....

Many many thanks. Hey, and Happy New Year.
 
Paul DS

Paul DS

Audioholic
Sorry to bring up an old thread on my first post but the topic and related article are the reason I joined up.

Without knowing the specifics of the transformers used in our receivers and amps I am assuming that the transformer secondary that results in lower voltage in the power supply (the '4 ohm' option) is made up of conductor that is actually thicker than the winding used for the '8 ohm' option. The arguments in the impedence switch article make sense but another way of ensuring 4 ohm stable thermal performance is to use beefier conductor in the transformer core. If that secondary is wound with thicker wire you get less turns and hence the lower voltage output but the thicker conductor will survive for longer under high current draw as the windings heat up from I^2R losses. Anyone have any parts transformers from receivers that can check or know of off the shelf transformer part numbers used in AVRs that I can check ? It would really be a waste of time if the 4ohm winding in the transformer had the same current rating as the 8 ohm winding which seems to be what Gene's arguing in the article from 2010.... oh my, i'm late to the party....

Many many thanks. Hey, and Happy New Year.
I use a Denon AVRX4400h receiver, my main tower speakers are 4 ohm. If I use the 8 ohm setting on the receiver, it gets very, very hot. I have used the Denon for some time now at the 4 ohm setting, get all the power I need, and the receiver runs cool as a cucumber.
 
P

PENG

Audioholic Slumlord
Sorry to bring up an old thread on my first post but the topic and related article are the reason I joined up.

Without knowing the specifics of the transformers used in our receivers and amps I am assuming that the transformer secondary that results in lower voltage in the power supply (the '4 ohm' option) is made up of conductor that is actually thicker than the winding used for the '8 ohm' option. The arguments in the impedence switch article make sense but another way of ensuring 4 ohm stable thermal performance is to use beefier conductor in the transformer core. If that secondary is wound with thicker wire you get less turns and hence the lower voltage output but the thicker conductor will survive for longer under high current draw as the windings heat up from I^2R losses. Anyone have any parts transformers from receivers that can check or know of off the shelf transformer part numbers used in AVRs that I can check ? It would really be a waste of time if the 4ohm winding in the transformer had the same current rating as the 8 ohm winding which seems to be what Gene's arguing in the article from 2010.... oh my, i'm late to the party....

Many many thanks. Hey, and Happy New Year.
There won't be any "4 ohm thicker winding", simply no such thing as it will be costly and impractical. I could be wrong, but try searching for such a transformer (one you described..)and I bet you won't find one. Of course, there are multi-winding transformers but not for the purpose you described. It would be easier to simply use a transformer with higher VA rating, and the winding will then be of thicker gauge naturally.

The 4 ohm setting is basically a setting that change the transformer tap to a higher pri to sec ratio so the sec voltage will be lower thereby limiting the current. It works like a tap changer, except in this case there are only 2 taps (one each for 8/4 ohms). It may be possible that in some cases, the 4 ohm setting could be done electronically instead of changing the transformer winding tap, to limit the output current instead.

I don't know if I read Gene's article of 2010 that you referred to, but if you are interested in a detailed read on this topic, the one below seemed to be from 2015:

or just a quick read (2004):

Gene was an EE in the communication (i.e. telecom) field, I was more on the power and control side and I concur with what he said in his articles. Anything is possible though I highly doubt we could wrong about how that setting works conceptually speaking. Regardless, some bench test measurements did show the 4 ohm setting for the D&M receivers limit power output significantly. So if you are like a lot of users who typically use only fractional to a few watts average with peaks occasionally reaching 100 to 200 watts (typically only happens in the L/C/R channels), you should be safe to use 8 ohm setting for 4 ohm speakers.

Happy new Year to you too.
 
H

hotrabbitsoup

Audiophyte
Thanks for the replies guys. Multiple secondary windings are common for the power supply transformers used in tube amps and is where I'm getting my inspiration from.

I think some cheaper amps, that actually have an impedence switch, implement the power restriction by using a tap on a single secondary winding that supplies a lower voltage to the power supply, but in a more expensive design I don't see why they couldn't use a second coil altogether. But, all that said I don't think it would be worth it, as you said, just make the transformer with the secondary coil that's going to work for all intended purposes in the first place.

But all manufacturers don't have acces to the same. Some shops have the size to invest in custom transformer production runs, some even wind themselves, while many others look to off the shelf parts.

I'll try and find some schematics of older 80s receivers with the switch and report back if I notice anything useful. I am EE too.
 
ntsarb

ntsarb

Audiophyte
Very interesting article. Thanks for sharing. A few things I don't understand, so here are my questions:

* Why does the manufacturer need to reduce the rail voltage more than required to keep the power rating steady? Would dropping the rail voltage from 38.47V (in the following example) to 33.3V significantly increase power loss in the form of heat? If so, does this relate to the transformer's efficiency at different voltage?

Example: if the system can supply 185W to an 8Ohm speaker, that means 38.47Volts output. At this voltage, a 6Ohms speaker would require (38.47^2 / 6 =) 246W, but if rail voltage was dropped to 33.3Volts (using the switch), the power rating would remain 185W.

* In case more heat is produced by use of lower impedance speakers at same wattage, would it not make more sense keeping the heat production steady (i.e as if n 8Ohm speaker was driven) by adjusting the voltage accordingly? Why would the manufacturer drop the rail voltage more than that?

* I have not fully understood the certification process, hence, my next question is: is the certification process biased towards use of higher impedance speakers, to the extent that it forces manufacturers to degrade the amplifier's actual capabilities (practically leading to the production of less heat with lower impedance speakers than the other way around)?

Many thanks.
 
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P

PENG

Audioholic Slumlord
* Why does the manufacturer need to reduce the rail voltage more than required to keep the power rating steady?
I believe they did it on as required basis. The issue is not so much "power". In my opinion, It was unfortunate that in the beginning, manufacturers started rating their amps by "power" output instead of voltage and current. It is now too late to change.

Loudspeakers are sort of voltage devices, their sensitivities are often rated as X dB/1W/1m but should be more appropriately rated X dB/2.83V/1m. 2.83 V is picked because for the popular 8 ohm loads, it would be equivalent to X dB/1W/1m. The fact is, if you apply a voltage signal to the loudspeaker's terminals, it would make sound in proportion to the applied voltage, not to the "power input" as such. That is, the speaker may only consume only 0.1 watt in one moment but make a very loud sound, yet may consume 0.2 W in another moment and make a much quieter sound.

If an amp is rated 100 W into an 8 ohm resistor, then it can be rated 50 W into a 4 Ohm resistor safely, and that means the output voltage has to be reduced by half in order for the current to be the same. The current would be 4.8 A. (using your 38.47 V, 8 Ohm example).

Now if the manufacturer knows their amp can be rated higher than 4.8 A, then they wouldn't have to lower the rail voltage as much for the 4 Ohm setting, may be lowering it by 30% is enough, just an example. That's why the lower rail voltage would vary depending on the specific amp's rated voltage and current capability. So far so good? And you can see why I said amps should have been more appropriately rated for their voltage and current limits, than just "power" that by itself actually makes little sense? By the way, keep in mind, you really don't know how much "power" your speaker would actually consume, all you know is how much current it draws on moment by moment basis, as a good portion of the so called "power" would be consumed, or dissipated in the amp itself!!

Would dropping the rail voltage from 38.47V (in the following example) to 33.3V significantly increase power loss in the form of heat? If so, does this relate to the transformer's efficiency at different voltage?
No, dropping the rail voltage should result in less current so less loss, not more, all else being equal.
Copper loss = I^2 R for an resistor load. For an inductive load such as many loudspeakers, it gets more complicated as much of the loss would be dissipated in the amp, not just in the speaker. It would depend on the phase angle vs frequency characteristics of the speaker.

Here's a good article for you:
Phase Angle Vs. Transistor Dissipation (sound-au.com)

* In case more heat is produced by use of lower impedance speakers at same wattage, would it not make more sense keeping the heat production steady (i.e as if n 8Ohm speaker was driven) by adjusting the voltage accordingly? Why would the manufacturer drop the rail voltage more than that?
Yes, but you are assuming the manufacturers drop the voltage more than necessary, you don't really know that for sure, as you don't know their products current capability. Again, think current, and phase angle, not "power".

* I have not fully understood the certification process, hence, my next question is: is the certification process biased towards use of higher impedance speakers, to the extent that it forces manufacturers to degrade the amplifier's actual capabilities (practically leading to the production of less heat with lower impedance speakers than the other way around)?
Not sure I fully understand what you are asking, but this is a complicated issue that I don't think there is a right or wrong answer even if you clarify your question.
 
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A

antineutrino

Audiophyte
Really interesting article. Just a silly question. Am I wrong or there is a little mistake while describing the two low impedance and high impedance setting? I mean I suppose low impedance is for speakers rated lower than 6 ohms while high impedance is for 8 ohms and higher than that.
 
Last edited:
lovinthehd

lovinthehd

Audioholic Jedi
Really interesting article. Just a silly question. Am I wrong or there is a little mistake while describing the two low impedance and high impedance setting? I mean I suppose low impedance is for speakers rated lower than 6 ohm while high impedance is for 8 and higher than that.
They don't all use the 6/8 thing, some avrs label it as 4 vs 6. In any case just leave it at the higher setting....
 
A

antineutrino

Audiophyte
here is the supposed mistake....
...Low Impedance (Z) Mode is the receivers low setting that the manufacturer recommends using when you attach loudspeakers rated below 8-ohms. (This mode limits the output voltage, and therefore the maximum current any given speaker can demand of it)...

and after that...
 
P

PENG

Audioholic Slumlord
here is the supposed mistake....
...Low Impedance (Z) Mode is the receivers low setting that the manufacturer recommends using when you attach loudspeakers rated below 8-ohms. (This mode limits the output voltage, and therefore the maximum current any given speaker can demand of it)...

and after that...
What mistake though? It sounds about right to me. The manufacturer would recommend using that setting for speakers rated 6 ohms nominal or lower, but if you use that setting the output will be limited to a lower maximum voltage, and that is correct as well. Whether you want to follow the manufacturer's recommendations or not is up to you.
 
A

antineutrino

Audiophyte
What mistake though? It sounds about right to me. The manufacturer would recommend using that setting for speakers rated 6 ohms nominal or lower, but if you use that setting the output will be limited to a lower maximum voltage, and that is correct as well. Whether you want to follow the manufacturer's recommendations or not is up to you.
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....
 
gene

gene

Audioholics Master Chief
Administrator
Sorry to bring up an old thread on my first post but the topic and related article are the reason I joined up.

Without knowing the specifics of the transformers used in our receivers and amps I am assuming that the transformer secondary that results in lower voltage in the power supply (the '4 ohm' option) is made up of conductor that is actually thicker than the winding used for the '8 ohm' option. The arguments in the impedence switch article make sense but another way of ensuring 4 ohm stable thermal performance is to use beefier conductor in the transformer core. If that secondary is wound with thicker wire you get less turns and hence the lower voltage output but the thicker conductor will survive for longer under high current draw as the windings heat up from I^2R losses. Anyone have any parts transformers from receivers that can check or know of off the shelf transformer part numbers used in AVRs that I can check ? It would really be a waste of time if the 4ohm winding in the transformer had the same current rating as the 8 ohm winding which seems to be what Gene's arguing in the article from 2010.... oh my, i'm late to the party....

Many many thanks. Hey, and Happy New Year.
You give receiver companies too much credit as if they are trying to optimize performance for 4 ohm loads with the switch. They aren't! It's there for one purpose as I stated in the article and related Youtube videos. It steps down the rail voltage so the amp clips much sooner during UL certification testing. It boggles my mind people still question this and it showcases how realistic the Netflix movie "Don't Look Up" really is.
 

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