How to test POLARITY/PHASE of your Speakers and Entire Sytem?

[esldude]

With multi-way speakers you sometimes have crossover designs that have drivers in reverse polarity to others in order for the crossover to function properly. If such is the case with your speakers holding 5 drivers you wouldn't want to change that. Your crossovers would alter the basic frequency response enough to be much worse if you did.

 

[esldude]

I think you can test for this at least up to the speaker terminals.

 

Will give it some more thought.

 

I think you could construct an asymmetrical tone with audacity or similar, then use a diode and multi-meter at the speaker terminals. Used in one direction you would read a higher DC voltage with the multimeter than you will once you reverse the multimeter connection. This at the speaker terminals. The direction of the meter connection with the higher reading would tell you if the entire system was correct phased or reverse phased. This probably doesn't make sense perhaps. If I get time, I will try it here and let you know if it works.

 

[esldude]

Audacity has a neat plug in called 'Diode Processor'. I am on linux, sometimes there are little differences in the linux and other versions, but I think this one is in all of them.

 

So open Audacity, select generate, select tone and it will by default offer 30 seconds of sine wave at 440 hz. That should be fine. So generate that tone.

 

Okay, you will need to have downloaded the Audacity plug ins for this part. They are listed alphabetically under the Effect menu then inside Plug Ins. So find Diode processor. You will get a slider with values between 0 and 3. An explanation that 1 is half wave and 2 is full wave rectification. Put the slider at 1.00 (need not be exact, but get pretty close). Then let it process your 440 hz sine wave. This makes the wave look like it would had it passed through a single diode.

 

Now take your diode tone and play through your system. You need nothing more than your multimeter for this part. Set your meter to read DC volts. Put your red lead on the speaker red terminal, put your black lead on the speaker black terminal. Play the tone and you should read some small voltage and it should be positive. If you read negative DC voltage then your system has reversed polarity overall. If reversed simply flip your speaker leads. Your system now has correct polarity.

 

The voltage reading will depend on the particulars of your system and might be a half volt or so or it could be a few volts. Still it will read steadily and the main thing is whether your reading is positive or negative. To confirm you also can flip your multimeter leads and it should read negatively that way.

 

[esldude]

I don't think it will matter. What matters is if the bulk of the signal is more in one direction than the other. You may have a point, and I did think about that. I have already tried it with my system before posting the test procedure. It worked, but I am using a system that is DC coupled. Give me a minute and I will stick a cap on the multimeter and see what happens.

 

[esldude]

Just connected the multimeter and put a cap in series with the leads. Worked just fine. I had a small value cap so the voltage reading was smaller, but it was a steady positive reading, and reversing leads it became a steady negative reading.

 

[esldude]

Yes, Audacity is available for Mac, Linux and PC. I just attached the file here. Audacity is a handy tool though worth having to play with.

 

This is testing the audio signal polarity.

 

Yes, you could do it with an analog outputs anywhere in the system. But there is no point anywhere except at the speakers. I suppose if you just wanted to know if a component altered phase it might matter to you. But for listening it only matters at the speakers.

 

For instance a number of brands over the years would have pre-amps and amps that flipped phase. As long as you pair them up, you flipped it once with the pre-amp, and the amp flipped it back. Result was the same as if it were never flipped.

 

Also, flipping phase by itself really does no harm. If your total system flips, just reverse your speaker connections and everything is fine.

 

[esldude]

Well, just got back from a quick bike ride. Nice day for it here in the Southeast USA.

 

Yes, I went back and attached the file. All you have to do is play it in any music player. It will unzip into a .wav file.

 

[esldude]

Caleb are you sure that is 40 volts and not 40 mV (millivolts)? Don't know if your multimeter is auto ranging or not.

 

If you are reading 40 volts DC on your speakers then something seems wrong?

 

BTW, you will get better results with the speakers connected. Prevents stray voltage readings.

 

With speakers connected, red lead of meter should be on red (+) lead on speaker. The black lead of the meter should be on the black lead (-) of the speaker. Measuring at the banana plugs is a good place to do it. Also just to confirm, the red and black leads of the meter should be connected at the same time.

 

Sorry about the poor illustration, I am attaching a sketch of the connection. I left out the speaker cables, but they should simply be connected as they normally are when you are listening to music. Meter set to volts DC.

 

 

 

[esldude]

If you were reading millivolts, then your readings might make sense. Lots of amps have some DC offset. Though reading that while playing the test signal seems unlikely. Did you have the test signal turned up enough to hear at something like normal listening volume? If you had the signal at low volume it may have been masked by the small DC offset of the power amp.

 

Multimeters have a very high input impedance like 10 megaohms. So very low stray voltage signals can be read. If you connect across a lower impedance load, the load usually gets rid of the stray voltage as it has no power behind it, it cannot create enough current to matter. You did say touching the leads together gave a zero reading which is how it should work.

 

Now reading something like a pre-amp output probably would work okay. The reading you get on DC like that will be small and you will need to have the scale reading in millivolts to see it. So you don't necessarily need to test at the next upstream component. I haven't used this signal to read a low voltage level like that, but it should work.

 

[esldude]

You are testing the signal from the amp. You really have to assume the speakers are marked correctly. As I mentioned before with multi-way crossovers they may intentionally invert some drivers vs. others. You really shouldn't need to worry about that. So get the signal at the speaker input terminals correct, by getting the amp correct and you should have it.

 

If something upstream of the speakers inverts polarity, then flipping the speaker leads will correct for it whether it is an amp, pre-amp or source that is doing the flipping.

 

I just checked my methodology here again. I dug up two 5 uF caps just to see if it mattered. Put these on the leads of the meter, and read almost exactly the same voltage as connecting the meter directly. I also generated a pure sine wave and tested it. Just as a for instance in this case, AC setting pure 440 hz sine wave read 1.88 volts while switching to DC gave a reading that fluctuated between -2 millivolts and plus 3 millivolts which basically is nothing. Reversing leads gave identical measurements. Next going with the asymmetrical test tone I uploaded in this thread, on AC I read .945 volts and switching to DC I read .757 volts which was pretty steady. The DC read positive in one direction and negative if I reversed leads. All readings taken at the speaker terminals.

 

So you should be able to get similar readings. Put on the test tone and set volume so you get maybe 2 volts using your meter on AC. Switching to DC you should get a reading somewhere between 1 and 1.5 volts and the polarity should tell you what you want to know.