Yamaha AS-801 "Impedance Switch": Confused and Frustrated

[Jeffrey Martinez]

Hello everyone,

Recently purchased a set of KEF Q950s (8 OHMS) to match with my Yamaha AS-801. Super excited but while trying to dial my system in, I asked the question on another forum about the impedance switch on the back of my Yamaha. Boy did I get a lot of different opinions on where my switch should be set... My head is spinning I couldn't follow.

Many posters said to set it at 4 OHMS as my speakers will dip down lower than the 8 OHMS my speakers are rated for and this setting would be able to handle it. Other said keep it at 8 OHMS to not limit the power to the speakers, others said keep it at 6 OHMS. This article from Alcoholics was mentioned several times https://www.audioholics.com/audio-amplifier/impedance-selector-switch-1 and the video clearly says to keep your speakers set to 8 OHMS.

Here is my confusion and frustration. My Yamaha has two settings (below) and the 4 OHMS setting is the same setting as the 8 OHMS. The other options is 6 OHMS. There's only two settings. This is exactly what the two settings are n the back of my Yamaha.

(A or B 4 OHMS minimum/speaker) (A+B 8 OHMS minimum/speaker)

Or

(A or B 6 OHMS minimum/speaker)

Please help my frustration and share which setting I should be on. I have tried them both, don't notice a huge difference, just don't want to fry my amp & speakers. Thank you!

 

[lovinthehd]

You're confusing things a bit. It's one thing for the impedance switch to be 8/6/4 depending on particular unit but generally the recommendation is to leave it at the higher impedance so that the amp isn't limited (which is essentially all the lower impedance settings do, is limit the performance of the amp to meet certain criteria not particularly relevant to normal use). Then again it's different as to using both A and B speakers simultaneously as to how that can affect impedance load on a 2ch amp like you have. Are you driving two pairs of speakers or just the one?

 

[John Parks]

Keep it on 8, leave it there and don't worry about it. Yes, I am speaking from experience as I had the same unit and Q750s then R500s.

Also mentioned in the A-S801 review found here: https://www.audioholics.com/amplifier-reviews/yamaha-a-s801-amplifier-review

 

[Jeffrey Martinez]

You're confusing things a bit. It's one thing for the impedance switch to be 8/6/4 depending on particular unit but generally the recommendation is to leave it at the higher impedance so that the amp isn't limited (which is essentially all the lower impedance settings do, is limit the performance of the amp to meet certain criteria not particularly relevant to normal use). Then again it's different as to using both A and B speakers simultaneously as to how that can affect impedance load on a 2ch amp like you have. Are you driving two pairs of speakers or just the one?

Just one pair of speakers. I think my confusion is the switch is both 4 OHMS and 8 OHMS.

 

[lovinthehd]

Just one pair of speakers. I think my confusion is the switch is both 4 OHMS and 8 OHMS.

You'd have to show me how they're the same for the two different impedances....page number in the manual to look at? The use of one pair of speakers you don't need to worry about the use of speakers on B, so just use your speakers and don't worry about it (i.e. the impedance load).

 

[Leemix]

Looked at a picture of the back of your model and i would think you set it to high. (As in high impedance setting)
The high setting is for 6ohm minimum and 8ohm like you have is more than that so set to high.
The A or B and A+B is if you use multiple speaker sets connected at the same time which will tax the system but i assume you are not connecting anything to both at the same time.

The volume control is what decides if there is danger or not to your speakers or components, playing very very loud is bad no matter the setting.


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[John Parks]

This is the switch:

Again, just leave it be and you will be fine. From Gene in his review: "You see that impedance selector switch on the backpanel? Don't touch it! Leave it at its factory default ‘high’ setting regardless of the speakers you connect, or else you will be starving your speakers of power just to validate a UL heat dissipation test that is required to list 4-ohm capability on the silkscreen." Another quote in the measurements section of the review: "There is a dreaded impedance switch on the back of the A-S801 that reduces the output power of this unit for certification purposes only. We recommend leaving it at the default 8 ohm setting and NEVER changing it."

 

[Jeffrey Martinez]

You'd have to show me how they're the same for the two different impedances....page number in the manual to look at? The use of one pair of speakers you don't need to worry about the use of speakers on B, so just use your speakers and don't worry about it (i.e. the impedance load).

You can view the back of the AMP here. https://www.audioholics.com/amplifier-reviews/yamaha-a-s801-amplifier-review

The "High" setting according to the back of my amp is for it to be set to 6 OHMS.

 

[Jeffrey Martinez]

This is the switch:
View attachment 50068
Again, just leave it be and you will be fine. From Gene in his review: "You see that impedance selector switch on the backpanel? Don't touch it! Leave it at its factory default ‘high’ setting regardless of the speakers you connect, or else you will be starving your speakers of power just to validate a UL heat dissipation test that is required to list 4-ohm capability on the silkscreen."

This article cleared it up for me. Several people said set it to high, which I assumed was 8 OHMS, but the back of the amp says high is 6 OHMS.

 

[John Parks]

The '801 and 950s should be an awesome combo - enjoy!

 

[Jeffrey Martinez]

This is the switch:
View attachment 50068
Again, just leave it be and you will be fine. From Gene in his review: "You see that impedance selector switch on the backpanel? Don't touch it! Leave it at its factory default ‘high’ setting regardless of the speakers you connect, or else you will be starving your speakers of power just to validate a UL heat dissipation test that is required to list 4-ohm capability on the silkscreen." Another quote in the measurements section of the review: "There is a dreaded impedance switch on the back of the A-S801 that reduces the output power of this unit for certification purposes only. We recommend leaving it at the default 8 ohm setting and NEVER changing it."

Thank you for this. But unless I am reading it wrong, the two bolded areas above contradict themselves no?

"Don't touch it! Leave it at its factory default ‘high’ setting regardless of the speakers you connect"- The high setting is 6 OHMS

"We recommend leaving it at the default 8 ohm setting and NEVER changing it."The 4OHMS/8 OHMS setting is low setting.

Sorry...just confusing.

 

[Leemix]

You can view the back of the AMP here. https://www.audioholics.com/amplifier-reviews/yamaha-a-s801-amplifier-review

The "High" setting according to the back of my amp is for it to be set to 6 OHMS.

Its not set for 6 ohm, if you read the text “High” is “minimum 6 ohm”. 8 ohm fall into that. 8 > 6
Its written in a confusing way thats true.

 

[Jeffrey Martinez]

Its not set for 6 ohm, if you read the text “High” is “minimum 6 ohm”. 8 ohm fall into that. 8 > 6
Its written in a confusing way thats true.

Got it!

 

[Leemix]

Thank you for this. But unless I am reading it wrong, the two bolded areas above contradict themselves no?

"Don't touch it! Leave it at its factory default ‘high’ setting regardless of the speakers you connect"- The high setting is 6 OHMS

"We recommend leaving it at the default 8 ohm setting and NEVER changing it."The 4OHMS/8 OHMS setting is low setting.

Sorry...just confusing.

The reason it says A or B 4ohm and A+B 8ohm is that 2 sets of 8 ohm speakers running at the same time(A+B bindings both used at same time) looks like and behaves like one set of 4 ohm speakers to the amp and the same for high 6 ohm setting (12 ohm divided by 2 is 6)


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[Leemix]

Got it!

Good, good. They really should make it clear because there are probably a lot of people stressing out over that selector just like you, these types of posts are very common for all kinds of amps.


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[Jeffrey Martinez]

Good, good. They really should make it clear because there are probably a lot of people stressing out over that selector just like you, these types of posts are very common for all kinds of amps.


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Thank you and thank everyone for helping with this. I'm going to go relax and listen to music.

 

[PENG]

Thank you and thank everyone for helping with this. I'm going to go relax and listen to music.

To be clear, if you have 8 ohm nominal speakers then leave it in the default 8 ohm setting.
If you have 4 ohm nominal speakers then the manufacturer clearly wanted you to use the 4 ohm setting because they have to cover their rear end, i.e. regulatory, legality issues.., that does not mean you would do damage to the amp if you ignore their recommendations. Conversely, if you do follow use the 4 ohm setting, it does not mean you will get poorer sound quality, because it depends on your actual power (voltage/current) requirements.

The fact is, amp output specs are not perfect, no even close. Yes some amps have higher current capability and will therefore be more suited for low impedance speakers, but ultimately it depends on the individual user's actual real world power requirements.

You can have an amp that is rated for 4 ohms such as the A-S2200, but if you crank it up high enough driving even 8 ohm large towers that has power handling rating of over 500 W, you can still risk damaging the amp if you are not careful.

Or you can have an amp not rated for 4 ohms (such as the A-S801), but your power requirement never exceeds 30 W (just an example I pick) driving your 4 ohm nominal speakers to the loudest level you can tolerate during the maximum peaks, then your little amp will be fine regardless of where you set the impedance selector.

 

[Pogre]

Thank you for this. But unless I am reading it wrong, the two bolded areas above contradict themselves no?

"Don't touch it! Leave it at its factory default ‘high’ setting regardless of the speakers you connect"- The high setting is 6 OHMS

"We recommend leaving it at the default 8 ohm setting and NEVER changing it."The 4OHMS/8 OHMS setting is low setting.

Sorry...just confusing.

Leave it at 8 ohms! Of all of the replies that's the one constant, consistent recommendation. The lower impedance switch (4 ohms) is there to limit power to meet the aforementioned UL Lab heat dissipation requirements.

 

[Phantom dc]

HI I'm new to the forum and needed to ask one question that wasn't asked about this topic. Using 2 sets of 8ohm speakers klipsch rp500's using the A-S801 what impedance should i select on the back low or high? I get I will be lowering the impedance to 4ohms. just asking because of the post above saying "leave it at 8ohms....."

 

[Pogre]

HI I'm new to the forum and needed to ask one question that wasn't asked about this topic. Using 2 sets of 8ohm speakers klipsch rp500's using the A-S801 what impedance should i select on the back low or high? I get I will be lowering the impedance to 4ohms. just asking because of the post above saying "leave it at 8ohms....."

The A-S801 may or may not be okay with a 4 ohm load, that you'll have to wait to hear from someone else. In general we'd recommend "leave it at 8" and use common sense with your volume.

What you describe, running 2 sets of 8 ohm speakers in parallel with a stereo receiver like that isn't really recommended. They're 8 ohm nominal but likely dip well below that. 6 ohms or less is not uncommon for 8 ohm rated speakers. Is it for 2 different rooms or something?