Need help with Impedance settings for Zone 2 with multi-room and in-wall volume knobs (1 Viewer)

[DougS78]

Hello,

I have a speaker system installed when we built our home that includes a total of 8 speakers (Yahama with 8 ohm) and these are controlled in different rooms by 6 volume knobs (details below). In the 7 years we've had our house, I have blown 3 receivers so I've come to the conclusion that there must be something wrong with the wiring or settings.

I am currently going about trying to make sure all of this is set up right in terms of impedance matching before I install the new receiver and could really use help.

Specifically, I am wondering how to set the impedance match switches on the knobs given some knobs are controlling 2 speakers and some are controlling just 1.

The set up is as follows.

2 outside speakers (deck) controlled by 1 knob
1 speaker (kitchen A) controlled by 1 knob
1 speaker (kitchen B) controlled by 1 knob
1 speaker (dining) controlled by 1 knob
1 speaker (office) controlled by 1 knob
2 speakers (bedroom) controlled by 1 knob

All wires run from the living room to the knobs around the house, and are "pig-tailed" to a single input into Zone 2.

My new receiver is an Onkyo TX-NR676 (4 ohm minimum impedance).

In consulting various websites (inculding here: https://www.hometoys.com/article/20...impedance-match-volume-control-settings/1540/), as best I can tell the knobs don't impact the calculation and I am just dividing the 8 speakers by their ohms (e.g., 8 divided by 8 = 1). Then I am dividing the receivers minimum ohms by that. So I calculate 4 divided by 1 = 4.

Thus, am I correct that all knobs are set to 4x and I'll be good? Or do the knobs that are wired for 2 speakers need to be calculated differently?

Thank you!!!

Doug

 

[Robert_J]

What kind of volume knob are they using? For example, this one has impedance correction - https://www.monoprice.com/product?p...MI_4f2t_783gIVBglpCh3QxQuyEAQYASABEgLln_D_BwE

Have you measured the resistance without an amp connected? Have someone turn the volume knobs and see what the lowest resistance is on the left and right wires (measure each separately). If you are dropping lower than 4 ohms you may need a pro amp to power them.

 

[DougS78]

THank you, Robert. These are great questions.

Yes, the knobs look almost just like that. I can't find the model anywhere on them, but it is basically that. There is a switch that you choose from 1x, 2x 4x, 8x

I have not measured the resistance, but would like more information about what you're suggesting. You are suggesting measuring the wires that are connected to the speakers? Or Measuring the ones that come to the knob?

 

[Robert_J]

Disconnect the wires from your receiver and measure there. That's where it is important. If it is only you, get some alligator clips for your meter or even tape the wires to the test probes and record the values using your smart phone in video mode. Run around and turn up/turn down the volume knob in different rooms. You may have a bad volume knob. Check each channel at a time. If you are running 8 ohm speakers, it should never drop below 6 ohms.

If you don't already have a meter, I found one on Amazon for under $10 with almost 1,800 reviews.
Etekcity Digital Multimeter, MSR-R500

 

[DougS78]

OK, I think I follow you. I took the multimeter I have (its a Cen Tech, but I think similar). I wasn't sure how to set the ohm reader, but set to 200 for sake of this test. First, I have to say that when I tested the two probes together at this setting I never got it to zero. It was mostly around 1.7 or 2.0. For reference when I plugged in the banana plugs for known single 8 ohm speakers I got a reading of around 10-11. so clearly there is some issue with calibration here and I'll need a new one.

So wanting to at least wanting to test your suggestion as best I could, I plugged in the zone 2 plugs. I then went around and first turned off all the knobs. The default reading when alone in this mode is about 1.0 or 0.9. I systematically turned them back on and then off. My daughter called out the readings and found that nothing changed as I turned each one up and down EXCEPT one in the office. This one caused it to go up from .9 to 1.4. It reliably did this and the rest did nothing.

Does this provide any useful information? Given the value of the zone 2 speakers (even if imprecise) was so much lower than a single speaker it suggests to me that something is not right. All jumpers were set to 4x when I did this test.

 

[Robert_J]

The Cen Tech from HF is fine for this. If your 8 ohm speaker has a crossover, then there is the possibility that 10 ohms is correct. You are reading DC voltage resistance. Your 8 ohm speakers are AC voltage impedance rated.

This is very helpful. It is not surprising that you blew a couple of receivers trying to drive a 1 ohm load in zone 2. The volume controls are working in that they show a constant resistance to the receiver and do not vary as the volume is turned up or down. But it seems the are not set correctly for the number of speakers you are driving.

Since you said they look like the controls I linked to, then they should have a setting for the number of speakers in the system. Check that. You should probably check each knob's setting.

 

[DougS78]

Thank you, Robert. So yes, each one of them has a jumper setting. Its a 1x, 2x, 4x, or 8x.

They were set at 4x at that time. I also used to have them all at 8x. Given its the highest they go, I am not sure what else I can do with them. Is there something I'm missing with regard to the calculations I made in the first post? At least it sure seems like this math should put the overall load at 4ohms or higher.

Although I don't understand the crossover scenario you mentioned, so perhaps this is an issue?

For now, I have just connected 2 of the zone 2 speakers for the main area of the home. For reference, the ohm reading I got was 5.6 with just those 2 connected. Is it possible that the jumpers might just stop working over time? In that it sure doesn't seem like the settings make the difference they should. These are 2 8ohm speakers, so with the 8x multiplier on both I should be way higher than that (right?).

I'd love to hear a suggestion for what to do. Should I add a speaker selector with impedance matching? Or as you mentioned a possibility, do I need another piece of equipment to drive zone 2?

thanks!

 

[Robert_J]

I've never used a multi-zone system, only read up on them so I could decide if I wanted to install one. I decided against it. So I have no idea if those controls can wear out. I think your idea of a speaker selector with impedance matching is a good alternative. Or swapping out controllers. Going either route will cost money and may fail. Your other option is a professional which will probably cost a lot more and you won't learn anything. I consider any failed DIY project that costs me money as paying for learning.

I'm running these speakers as my left/center/right - http://projectgallery.parts-express.com/speaker-projects/the-d-iii/ If you look at the crossover design you will see the single tweeter and dual woofers. The woofers are 8 ohms nominal each but wired in parallel, the have a nominal 4 ohm load at the receiver. There are also level matching resisters on the tweeter section of the crossover that add to the resistance. If I measure them with a meter, they measure much higher than 4 ohms because of the tweeter and additional resistor. But that is because the meter just sends a very low voltage DC current through the crossover. Coils and capacitors filter by frequency so the receiver really "sees" a 4 ohm load from about 3,500 hz and lower but higher than an 8 ohm load above 3,500 hz. Because it takes more voltage for the amp to amplify lower frequencies, my Pioneer could not handle driving these speakers at higher volumes.

I bought my first speaker building book from Radio Shack in 1986 and it has been a hobby of mine ever since. It took years for me to understand that concept I described since I didn't take anything more than basic physics in college.