Speakers causing the Power Amplifier to go into protection mode repeatedly

singhrajiv

Hi

I have the following Polk Audio Speakers:

1. Front Left - RTI12
2. Front Right - RTI12
3. Center - CSI6
4. Pair of FXiA6 as surrounds.

All speakers are connected with blue jean cable 10AWG. All speakers are properly terminated with banana plugs and insulated via heat shrink insulation. Tested the speaker wires for continuity - no issues.

I am trying to connect a Yamaha MX-A5000 to the speakers which is connected to a Pioneer Elite SC61 via preouts.


The speakers work fine when connected directly to the receiver. However when ever I try connecting them to the power amplifier - the amplifier goes into protection mode.

How can a test the speakers independently using a multimeter and other means at home to rule out any speaker issues. Please advise on any additional things I need to check before reconnecting the amp.

Appreciate your inputs.


Rajiv

F1nut

Agreed, it's not your speakers, it's your amp.

singhrajiv

Thanks for confirming

Speedskater

Try one speaker on one channel, then that speaker on the other channel.
Then do the same thing with the other speaker.

singhrajiv

I tried that connect one channel at a time, when I connected the left front channel it went into protection mode. Before connecting the left front I had tested for center and front right channel and it worked fine. Is there a way to test the woofer drivers and tweeters and the crossover using a multi-meter?

Dennis Gardner

Since you have determined that the front left channel may be shorted, connect a single speaker that doesn't short out any other channel on that front left by itself to see if that amp channel is bad. You can then move it around to see if any other single channel is involved. Remember, you are testing for a bad amp channel, not for a bad speaker, since they worked just fine on your receiver.

singhrajiv

Just got the word from the service center, the amplifier chip confirmed - speaker or speaker wire shorted. Tested for continuity for speaker wires checked out fine. As per the service center , the resistance measurement for an 8 hm rated speaker at the amplifier terminal with the speaker wires connected to speaker should measure between 2 to 4 ohms. Measurements were OK for the center and surround speakers. For the Front and Left RTI - the measurement came to 9.5 Ohms and when tested and individual woofer driver - it came at 2.7 ohms- is there an issue with the woofer coil and does it need to be replaced. Normal measurement of 8ohm rated speaker should be around 75% of the rated impedance.

Also the measurement at the speaker wire for the tweeter came as infinite. Is this OK.

Please advise.

Dennis Gardner

I agree that the 75% rule is about right. What I can't agree with yet is a bad speaker if it worked on another receiver. I still believe that you haven't narrowed it down to a single speaker issue yet.

Start with the left front by itself as the only speaker plugged into the amp to see if it alone will trigger the protection. If it does, then move it to another channel within the amp to see if it goes into protection. If it does on multiple channels, then the wire or speaker may have a short.

tonyb

If the speaker or wire had a short, it would also send the receiver into protect mode. Because it works on the receiver, it has to be the amp or user error. If we eliminated the amp, as said by having it checked out, the only thing left is user error, or the receiver itself.

So my question is.....have you tried different cables, or different IC's between the amp and receiver ? Did you pop the top in the receiver to check if a lose wire maybe can be seen at that corresponding output jack ? That would explain why the speakers work with the receiver, but not when using the pre outs to add an amp.

mdaudioguy

I've been through a similar ordeal. A short condition may not necessarily throw a receiver into protection mode immediately. At lower volumes, everything may seem ok, but during higher volumes or peaks, boom, it shuts down. I drove a nail into one of my in-wall wires and experienced this. Not sure if you've tried running another wire yet.

My theory was that the wire wasn't actually shorted, but the nail pierced one side and caused positive and negative to be too close, leaving little to no insulation between the two, which only became problematic at higher current. I don't know if this theory is electrically sound, but it made sense to me and helped me solve my problem.

singhrajiv

I have replaced all speaker wires and are not running through the wall but on wall. The funny thing is that with the jumper plate installed ( as advised by polk audio tech support) between the lower and upper terminals, the right front speaker measures 8.4 ohms across the terminals which is line with the 8 ohm rated impedance - however I checked for the left front speakers with the jumper plate installed and it measured at 8.4 ohm, which means the actual impedance may be in the range of 11.2 ohms (measured dc resistance is about 75 % of the ac impedance) .

Even Yamaha service center support says once they reset the amp and got it out of protection mode, they had the power amp on for 24 hours with speakers connected with no issues, no burnt out fuses or channels. At the behest of polk audio tech support I removed all drivers and checked for any signs of physical damage on the cross overs did not find any signs of burn or physical damage. Here are the resistance measurements for all the Woofer and mid-range drivers - the measurements were identical for both front left and right speakers:

Mid-range Drivers: 3.2 & 3.3 ohms for the two drivers
Woofer Drivers: 2.4, 2.5 and 2.4 ohms for the 3 drivers.

I know for a fact as soon as I will connect the speaker it will send the amp into protection mode and will need to go back again to the service center for reset.

As per the service center technician, the resistance on the speaker wire (positive and negative terminals) end which will be connected to the power amp should measure between 4 and 8 ohms. For the center and surround speakers it measures within that range - However for the front channels both left and right the number is 8.5 ohms.

Could there be an issue with the speaker wire for the front left and right channels. I checked using a South wire continuity tester (south wire http://www.lowes.com/pd_761625-295-40040S___?productId=999970936&pl=1&Ntt=continuity+tester) and it checked out fine.

Not sure what to do next??

Dennis Gardner

I saw that you did a continuity check on your speaker wires, but did you check for cross continuity? This would be the indication of a short. Negative to positive.

pitdogg2

Yes this ∆∆∆∆∆∆∆

singhrajiv

Thanks for the valuable inputs. I have also initiated a dialog with Yamaha - to which they have requested to ship the unit to one of their facilities to check the unit out.

I will retest the wires for cross continuity as well.

Is there a definitive method to identify a shorted speaker and what kind of tools are required to determine that.

Appreciate your inputs.

Dennis Gardner

If all drivers check out as good, then the crossover may have an issue.

I still maintain that if the speakers worked properly with your receiver, but not with your amp, then the amp must be at fault.

The protection circuit in your new amp could simply be so sensitive that an issue with the crossovers in your mains is causing the amp to detect the fault that the receiver simply worked with.

Personally, I don't know that I would want to deal with an amp that required a service center reset each time my system had a hiccup. They used to install fuses that were user serviceable instead of circuits so complicated that it rendered it inoperable.

heiney9

I've lost track of the gear in this thread, but 80's and early 90's Yamaha amps suffer from inexpensive protection circuits that eventually start to fail with age. If this fits your scenario that's probably the culprit.

H9

Dennis Gardner

New 11 channel HT amp. crutchfield.com/p_022MXA5000/Yamaha-MX-A5000.html?tp=180&awcp=1t1&awcr=28874215883&awdv=c&awkw=mx+a5000&awmt=p&awnw=g

singhrajiv

I did the cross continuity test to find any short circuits in speaker wires, did not find any.
I also measured the dc resistance from the speaker wire end connecting to the amp terminals - here are the readings:

Front (Left & Right RTi12) - 8.7 Ohms.
Center Channel (CSiA5)- 4.6 ohms.
Surrounds (FXiA6) - 4.0 ohms. (For left and right respectively)

Not sure if there is an issue with my Center and Surrounds as the numbers don't add up for a rated impedance of 8 ohms.

Since the amplifier impedance selection switch is set of 8 ohms , could this differential in speaker loads be causing the amplifier to go into protection mode.

Also if I need to get an impedance tester, to gauge the the true speaker load, can you suggest one.


Appreciate your inputs.

F1nut

the resistance measurement for an 8 hm rated speaker at the amplifier terminal with the speaker wires connected to speaker should measure between 2 to 4 ohms. Measurements were OK for the center and surround speakers. For the Front and Left RTI - the measurement came to 9.5 Ohms

That's far too much resistance. It should be the 4 ohm range.

Also the measurement at the speaker wire for the tweeter came as infinite. Is this OK.

Exactly what and where were you measuring?

F1nut

I also measured the dc resistance from the speaker wire end connecting to the amp terminals - here are the readings:

Front (Left & Right RTi12) - 8.7 Ohms.
Center Channel (CSiA5)- 4.6 ohms.
Surrounds (FXiA6) - 4.0 ohms. (For left and right respectively)

I see the resistance changed a little bit for your fronts from the earlier measurement. Regardless, it's still too high.

Not sure if there is an issue with my Center and Surrounds as the numbers don't add up for a rated impedance of 8 ohms.

Yes, they do. It's your fronts that don't.

singhrajiv

The service center had advised me that the load at the amplifier terminal at the speaker wire should be around 4 ohms hence checked the load. Where I got the measurements as stated above.
The reason the numbers were a little different before the Multi-meter was defective - had to get a new one hence the difference.

The speaker wire resistance measured at .1 to .2 ohms.

F1nut

The service center had advised me that the load at the amplifier terminal at the speaker wire should be around 4 ohms hence checked the load.

That is correct, the measurement should be around 4 ohms. The fact that you got 8.7 ohms on the fronts indicates they have a problem.

Also the measurement at the speaker wire for the tweeter came as infinite. Is this OK.

This is what I am not clear about. Exactly what and where were you measuring?

singhrajiv

Ignore the statement - Also the measurement at the speaker wire for the tweeter came as infinite. I am trying to learn the physics behind the audio electronics and the statement just reflected my ignorance on the subject.

I will contact Polk Audio Customer Service for further assistance on getting the towers fixed.