Out of Phase? or "Dead zone/muddy sounding vocals"

[tillerman6]

Well not everyone has a two channel oscilloscope to play with, so I don't expect too many answers for this question, but here is something to try that's easy and fast!

I must apologise in advance if I'm missing some basic information, but I think we were all fed the same cautionary tales about making sure that you maintain polarity + to + and - to - from your amp terminals to your speakers right???

But I have went to a lot of trouble and checked my polarity 3 times with a flashlight and it was perfect. However, the sound in my living room was crap. I could hardly make out the words in the vocals and midrange was muddy to say the least. I went thru all the setup steps 5 times and the only way it sounded half way decent was to crank it up about half way which drives the wife crazy ( and we all know about what a bad idea that is!)

But I remembered my old oscilloscope and thought it would be a good idea to check the phase from an electronic viewpoint.

And as luck would have it, there are a couple of You Tube sources for test tones that you can run thru You Tube and or your Iphone to put that 1 KHZ tone on your input for free!
So I did, BUT I don't understand why I got that 180 degree out of phase display on the scope?? Checked it 3 times! Is that all rcvrs, or just Yamaha, or what?

But here is the good part- Since the two sine waves were exactly 180 out at the RCVR, it would be easy to swap the wires on ONE speaker and go the other way around- which I did,
and guess what? The muddy dead zone is drastically reduced! And you don't need a scope to play with your polarity ---- If you have a dead zone in the listening room or the vocals are mushy at lower volumes- just swap ONE of the left or right speaker wires and put them back on reversed. There is no danger to your equipment since everything is insulated to the max. It will only move the speaker cone the opposite direction from what it has been doing up to this point.

 

[nicoleise]

If the polarity within the receiver is wrong (I understand you can "fix" this by switching the + and - wires), wouldn't a simple multimeter on DC setting show this error?

I think that if your measurements are correct, it's a highly unusual flaw in your receiver. On the other hand, you seem to be able to "fix" the error by swapping polarity of one speaker. But are you confident it the source material?

I ask because you state you got the test tone off YouTube, and while there's plenty of great content there, there's also both worthless content and downright trolling. So I'm wondering if maybe the test tone itself, if in stereo, may contain the actual error. Did you check for this?

 

[highfigh]

Well not everyone has a two channel oscilloscope to play with, so I don't expect too many answers for this question, but here is something to try that's easy and fast!

I must apologise in advance if I'm missing some basic information, but I think we were all fed the same cautionary tales about making sure that you maintain polarity + to + and - to - from your amp terminals to your speakers right???

But I have went to a lot of trouble and checked my polarity 3 times with a flashlight and it was perfect. However, the sound in my living room was crap. I could hardly make out the words in the vocals and midrange was muddy to say the least. I went thru all the setup steps 5 times and the only way it sounded half way decent was to crank it up about half way which drives the wife crazy ( and we all know about what a bad idea that is!)

But I remembered my old oscilloscope and thought it would be a good idea to check the phase from an electronic viewpoint.

And as luck would have it, there are a couple of You Tube sources for test tones that you can run thru You Tube and or your Iphone to put that 1 KHZ tone on your input for free!
So I did, BUT I don't understand why I got that 180 degree out of phase display on the scope?? Checked it 3 times! Is that all rcvrs, or just Yamaha, or what?

But here is the good part- Since the two sine waves were exactly 180 out at the RCVR, it would be easy to swap the wires on ONE speaker and go the other way around- which I did,
and guess what? The muddy dead zone is drastically reduced! And you don't need a scope to play with your polarity ---- If you have a dead zone in the listening room or the vocals are mushy at lower volumes- just swap ONE of the left or right speaker wires and put them back on reversed. There is no danger to your equipment since everything is insulated to the max. It will only move the speaker cone the opposite direction from what it has been doing up to this point.

RoomEQ Wizard shows wide frequency range and where phase cancellations are occurring. It also allows seeing correction in real time over that wide range if someone installs/moves acoustical treatments. Much more efficient method than using a scope. Since this program can be run with most computers, a line audio input can be fed from an amplifier's output using a resistor in series with the speaker outputs. DO NOT make any connections when the equipment is ON and don't make or break connections to the speaker outputs on a tube amp when it's ON.

Just switching the wires at one speaker can work, but there's no certainty WRT where the reversal is occurring- don't be surprised if it's in the speaker- manufacturing hasn't reached the point of perfection. Also, if a midrange driver has been replaced, it's entirely possible that whoever did the work didn't understand that the polarity of that driver was reversed because the crossover design requires it, so the output in the crossover region of the woofer and mid will be 'in phase'.

What does "insulated to the max" mean?

 

[TLS Guy]

Well not everyone has a two channel oscilloscope to play with, so I don't expect too many answers for this question, but here is something to try that's easy and fast!

I must apologise in advance if I'm missing some basic information, but I think we were all fed the same cautionary tales about making sure that you maintain polarity + to + and - to - from your amp terminals to your speakers right???

But I have went to a lot of trouble and checked my polarity 3 times with a flashlight and it was perfect. However, the sound in my living room was crap. I could hardly make out the words in the vocals and midrange was muddy to say the least. I went thru all the setup steps 5 times and the only way it sounded half way decent was to crank it up about half way which drives the wife crazy ( and we all know about what a bad idea that is!)

But I remembered my old oscilloscope and thought it would be a good idea to check the phase from an electronic viewpoint.

And as luck would have it, there are a couple of You Tube sources for test tones that you can run thru You Tube and or your Iphone to put that 1 KHZ tone on your input for free!
So I did, BUT I don't understand why I got that 180 degree out of phase display on the scope?? Checked it 3 times! Is that all rcvrs, or just Yamaha, or what?

But here is the good part- Since the two sine waves were exactly 180 out at the RCVR, it would be easy to swap the wires on ONE speaker and go the other way around- which I did,
and guess what? The muddy dead zone is drastically reduced! And you don't need a scope to play with your polarity ---- If you have a dead zone in the listening room or the vocals are mushy at lower volumes- just swap ONE of the left or right speaker wires and put them back on reversed. There is no danger to your equipment since everything is insulated to the max. It will only move the speaker cone the opposite direction from what it has been doing up to this point.

I have been thinking about this, and if you are correct, that there is phase inversion of one channel, then there more likely than not is a serious fault in one of your power amps. I don't see how this could be a simple wire inversion, as the terminals are usually soldered into a circuit board and not usually wired.

You need to remove that unit from service and bench test it with a dual channel scope and signal generator.

You then need to see which channel is out of phase with the input. The channel with the output out of phase with the input needs looking at closely as there is probably a failure in that amp, in the phase/splitter driver stage ahead of the power transistors. More likely than not there is a failed diode.

 

[tillerman6]

I have been thinking about this, and if you are correct, that there is phase inversion of one channel, then there more likely than not is a serious fault in one of your power amps. I don't see how this could be a simple wire inversion, as the terminals are usually soldered into a circuit board and not usually wired.

You need to remove that unit from service and bench test it with a dual channel scope and signal generator.

You then need to see which channel is out of phase with the input. The channel with the output out of phase with the input needs looking at closely as there is probably a failure in that amp, in the phase/splitter driver stage ahead of the power transistors. More likely than not there is a failed diode.

 

[tillerman6]

TLS guy!
Yes I agree with you about the idea of being hard wired at the factory into a circuit board. It is extremely unlikey that there could be a crossed channel in the output of the RCVR.

I don't have schematics for the RX-V 365, so I'm relying on Yamaha corp to come up with an idea or just tell me that "it's normal" and not to worry about it??? Although THAT would worry me a lot more, because I have heard that polarity matching dogma for 40 years and no one ever questioned it. I just assumed that we were all on the same page, and both left and right channels DO go positive at the same instant in time with a mono input tone, but I have never actually fact checked that idea with a scope until yesterday.

And it is still possible that my scope is playing tricks on me, but I did touch both probes to the test output on the scope and got a perfect overlay of the two signals in time and polarity that way. Then without changing any settings on the scope I went back to the two red speaker wire outputs on the back of the RCVR and got that same out of phase wave form every time.

Unfortunately, the mounting and lack of shielded probe connections for the scope is hampering my testing efforts. I have never had to crawl around like this before and try to hand hold the probe tips down in a hole like that, so I never bought anything for that purpose- until now. - It's in the mail.

The other variable is how the test tone is delivered. That test was done using the 1000 HZ test tone off of You Tube. I know nothing about that, but I would assume that it's legit and it is a single source sine wave.
I just used my cell phone to select it on you tube and it comes thru the speakers loud and clear.

I don't own a signal generator as I had always used the equipment at Honeywell Aerospace or Texas instruments. I have about 35 years of electronics hands on , but you know the old sayin- There never was a horse that couldn;'t be rode and there never was a cowboy that couldn't be throwed" .

Anyway, in a couple of days I will have some proper shielded coaxes with alligator clips on the ends which I will attach and shoot some pictures for everyone. I think Yamaha would like to see that too?

I appreciate your interest and help, and I'm hoping and waiting for someone on here to repeat the 1KHZ tone test on their own equipment and see if they get the same result. That would tell me if I'm looking at a bad RCVR or not. Unfortunately, I do not have another RCVR to test. it should be something other than a Yamaha just for good measure.

 

[tillerman6]

RoomEQ Wizard shows wide frequency range and where phase cancellations are occurring. It also allows seeing correction in real time over that wide range if someone installs/moves acoustical treatments. Much more efficient method than using a scope. Since this program can be run with most computers, a line audio input can be fed from an amplifier's output using a resistor in series with the speaker outputs. DO NOT make any connections when the equipment is ON and don't make or break connections to the speaker outputs on a tube amp when it's ON.

Just switching the wires at one speaker can work, but there's no certainty WRT where the reversal is occurring- don't be surprised if it's in the speaker- manufacturing hasn't reached the point of perfection. Also, if a midrange driver has been replaced, it's entirely possible that whoever did the work didn't understand that the polarity of that driver was reversed because the crossover design requires it, so the output in the crossover region of the woofer and mid will be 'in phase'.

What does "insulated to the max" mean?

Room EQ Wizard-
"Insulated to the max" + The speakers are not metal, the floor is not wet, the amp is grounded in some cases (mine was not) the speaker wire is insulated for a couple of hundred volts. There isn't much chance of a short to ground or any sort of electrical problems with a normal setup. Pretty safe to swap + to - at either end of the speaker wires if you shut the amp down first.

When I get my RCVR phase question solved I will also be looking into my speaker cone phasing. You are absolutely right - anything can happen with that. These old speakers have never been worked on, but they are paired with a set of Bose 301's for the time being. There are two Pioneer CS511A's and two Bose 301's on top of them (literally) It's probably a terrible idea, but that's what we have right now.
The living room is also a challenge- 16 foot front to back and 24 ft wide with a vaulted ceiling.

My next new project will be some flat panel speakers made out of ceiling tiles and the little 40 watt stick on drivers as per the You Tube videos- something to play along with my Klipsch sub woofer.

The idea is to get wide area dispersion of the sound. This room needs all the help it can get!

 

[TLS Guy]

Room EQ Wizard-
"Insulated to the max" + The speakers are not metal, the floor is not wet, the amp is grounded in some cases (mine was not) the speaker wire is insulated for a couple of hundred volts. There isn't much chance of a short to ground or any sort of electrical problems with a normal setup. Pretty safe to swap + to - at either end of the speaker wires if you shut the amp down first.

When I get my RCVR phase question solved I will also be looking into my speaker cone phasing. You are absolutely right - anything can happen with that. These old speakers have never been worked on, but they are paired with a set of Bose 301's for the time being. There are two Pioneer CS511A's and two Bose 301's on top of them (literally) It's probably a terrible idea, but that's what we have right now.
The living room is also a challenge- 16 foot front to back and 24 ft wide with a vaulted ceiling.

My next new project will be some flat panel speakers made out of ceiling tiles and the little 40 watt stick on drivers as per the You Tube videos- something to play along with my Klipsch sub woofer.

The idea is to get wide area dispersion of the sound. This room needs all the help it can get!

More BS. How the Hell can you claim a phasing issue if you don't have a signal generator to inject a sine wave into the unit?

Members, this thread is nonsense with zero validity.

 

[MrBoat]

Room EQ Wizard-
"Insulated to the max" + The speakers are not metal, the floor is not wet, the amp is grounded in some cases (mine was not) the speaker wire is insulated for a couple of hundred volts. There isn't much chance of a short to ground or any sort of electrical problems with a normal setup. Pretty safe to swap + to - at either end of the speaker wires if you shut the amp down first.

When I get my RCVR phase question solved I will also be looking into my speaker cone phasing. You are absolutely right - anything can happen with that. These old speakers have never been worked on, but they are paired with a set of Bose 301's for the time being. There are two Pioneer CS511A's and two Bose 301's on top of them (literally) It's probably a terrible idea, but that's what we have right now.
The living room is also a challenge- 16 foot front to back and 24 ft wide with a vaulted ceiling.

My next new project will be some flat panel speakers made out of ceiling tiles and the little 40 watt stick on drivers as per the You Tube videos- something to play along with my Klipsch sub woofer.

The idea is to get wide area dispersion of the sound. This room needs all the help it can get!

The room could be why everything sounds off. Put in a suspended acoustic ceiling to cancel the vault and put the speakers on the small end and pitch the Bose.

 

[highfigh]

Room EQ Wizard-
"Insulated to the max" + The speakers are not metal, the floor is not wet, the amp is grounded in some cases (mine was not) the speaker wire is insulated for a couple of hundred volts. There isn't much chance of a short to ground or any sort of electrical problems with a normal setup. Pretty safe to swap + to - at either end of the speaker wires if you shut the amp down first.

When I get my RCVR phase question solved I will also be looking into my speaker cone phasing. You are absolutely right - anything can happen with that. These old speakers have never been worked on, but they are paired with a set of Bose 301's for the time being. There are two Pioneer CS511A's and two Bose 301's on top of them (literally) It's probably a terrible idea, but that's what we have right now.
The living room is also a challenge- 16 foot front to back and 24 ft wide with a vaulted ceiling.

My next new project will be some flat panel speakers made out of ceiling tiles and the little 40 watt stick on drivers as per the You Tube videos- something to play along with my Klipsch sub woofer.

The idea is to get wide area dispersion of the sound. This room needs all the help it can get!

Disconnect the Bose or Pioneer speakers- that configuration could be causing the problems- the sound from one speaker arrives at a different time from the other. Line array speakers are time-aligned, yours aren't.

 

[tillerman6]

Disconnect the Bose or Pioneer speakers- that configuration could be causing the problems- the sound from one speaker arrives at a different time from the other. Line array speakers are time-aligned, yours aren't.

Hifigh- That's a good point, but the room is fairly large and the sound is better with all 4 fronts working at the same time even if they are out of time/phase. With just the Bose or the Pioneers alone they sound too far away for lack of a better description.

And today I noticed that the right channel is much lower in volume than the left on the Bose system.
That could be a symptom of the original problem ? It would be unusual, but it is still possible I guess.

I have been looking in vain for another rcvr or an integrated amp ( I never listen to radio), don't own a turntable or tape deck any more, rarely play a CD etc.

When the wife is out of the house again I will do some more testing. If the right channel is really dying it will show up in the 1000 hz test tone and on the scope.

I have the RX-V365 levels cranked to the far right trying to get enough volume there to match up with the left side now.

Don't have a test bench to ring stuff out anymore. And that's slowing me down with the troubleshooting.

Right now everything is sourced from the TV which is feeding audio thru an optical link to the RX-V so it's possible that the right channel is being attenuated or not being amplified further upstream too.

But to replace the RX-V with something with dedicated pre-outs that could drive my P2250 would be expensive, so I'm making due with what I have for now.

I was going to try driving both sets of speakers in parallel off of the P2250, and it can handle a 4 ohm load just fine, but it needs a level 4 preamp type input to make it follow whatever source I can provide- which doesn't work with the RX-V unless I can use a speaker level to line level converter. (LOC)

So I ordered a cheap one Boss audio today just for testing purposes.

In a couple of months I will be in a better financial position and all this will change, but right now I'm stuck

"in the mud room" as it were LOL!

 

[nicoleise]

I just assumed that we were all on the same page, and both left and right channels DO go positive at the same instant in time with a mono input tone, but I have never actually fact checked that idea with a scope until yesterday.

Wait, what...?
You're basing all this on a receiver not driving the L and R channels in perfect sync? Did you check the settings for channel delay/distance in the receiver?

If for example L is configured to be 1 ft further away than R, then the receiver will delay the output of the closer speaker (R) by the time it takes sound to travel 1 ft (a bit under 1 ms).

It's the only way the receiver can compensate for different distances in an (imperfect) layout of speakers. So if L/R are not set to the exact same delay/distance then what you're observing is simply intended functionality.

To rule out other issues, I'd suggest repeating your test will all delay settings (including for all speaker channels and the A/V delay) at zero. It may sound displeasing at the MLP, depending on your layout, but the channels should then be in sync (still providing your test signal is actually correct and is played back correct by your phone).

 

[TLS Guy]

Hifigh- That's a good point, but the room is fairly large and the sound is better with all 4 fronts working at the same time even if they are out of time/phase. With just the Bose or the Pioneers alone they sound too far away for lack of a better description.

And today I noticed that the right channel is much lower in volume than the left on the Bose system.
That could be a symptom of the original problem ? It would be unusual, but it is still possible I guess.

I have been looking in vain for another rcvr or an integrated amp ( I never listen to radio), don't own a turntable or tape deck any more, rarely play a CD etc.

When the wife is out of the house again I will do some more testing. If the right channel is really dying it will show up in the 1000 hz test tone and on the scope.

I have the RX-V365 levels cranked to the far right trying to get enough volume there to match up with the left side now.

Don't have a test bench to ring stuff out anymore. And that's slowing me down with the troubleshooting.

Right now everything is sourced from the TV which is feeding audio thru an optical link to the RX-V so it's possible that the right channel is being attenuated or not being amplified further upstream too.

But to replace the RX-V with something with dedicated pre-outs that could drive my P2250 would be expensive, so I'm making due with what I have for now.

I was going to try driving both sets of speakers in parallel off of the P2250, and it can handle a 4 ohm load just fine, but it needs a level 4 preamp type input to make it follow whatever source I can provide- which doesn't work with the RX-V unless I can use a speaker level to line level converter. (LOC)

So I ordered a cheap one Boss audio today just for testing purposes.

In a couple of months I will be in a better financial position and all this will change, but right now I'm stuck

"in the mud room" as it were LOL!

Repeatedly stirring that dog's dinner of a system will only make things worse. You need to simplify, simplify and simplify and not add more muck
to dish. That system is horrendous and there is no other word for it.

 

[One and a Half]

Just wondering, is the amp processing a simulated or processed signal at all? The output could be subtracted to provide this effect, but it sounds like an extreme condition for the fronts usually meant for rear channels, Are they also out of phase by any chance when you look at this again?

 

[tillerman6]

Wait, what...?
You're basing all this on a receiver not driving the L and R channels in perfect sync? Did you check the settings for channel delay/distance in the receiver?

If for example L is configured to be 1 ft further away than R, then the receiver will delay the output of the closer speaker (R) by the time it takes sound to travel 1 ft (a bit under 1 ms).

It's the only way the receiver can compensate for different distances in an (imperfect) layout of speakers. So if L/R are not set to the exact same delay/distance then what you're observing is simply intended functionality.

To rule out other issues, I'd suggest repeating your test will all delay settings (including for all speaker channels and the A/V delay) at zero. It may sound displeasing at the MLP, depending on your layout, but the channels should then be in sync (still providing your test signal is actually correct and is played back correct by your phone).

Good points to consider, but my scope second channel was showing 180 degrees out of phase, not just a tiny fraction, so it's either a scope setting out of place or the amp is really bad. I will be replacing the amp soon, so there will be time to check things out properly then. By the way- the delays if any for speaker distance were minimal.