Drivers out of phase on 2-way?

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theAnonymous1

theAnonymous1

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Joined 2004
I bought this "phase tester" tool just because it was ridiculously cheap (like $9). You play a burst tone that was supplied on a CD and then hold the device up to the driver under test and it will light a green or red light to tell you the "phase". It seems to work in that regard.

Anyway, the first thing I tested it on is my Phase Technology PC80 2-ways. It showed that the tweeter and woofer are out of phase. I checked the internal wiring and the colors match at least.

This probably shows my complete ignorance of speaker design, but is this phase mismatch intentional by the designer? Is this tool even a useful device or just a gimmick?


Thanks
 
K

KeepHopeAlive

Member
Joined 2013
Don't confuse phase with polarity.
Polarity is absolute. Polarity can be visually inspected and physically changed by reversing wires.
Phase is relative. Phase is affected by crossovers and distance (among other things). Two drivers are in phase at some frequencies and out of phase at others and a blend of both depending on where you measure. Room reflections and baffle diffraction will also play a role.

When you place the device in front of the tweeter you still measure the woofer but with different path lengths. You also measure diffraction effects. Also, distance from the driver will matter.

If the device is equidistant from both drivers and the noise burst is around the crossover point then it may be useful. Hard to say without seeing it and the test.

Cheers.

Rich
Acoustics Engineer
 
J

jjrenman

Member
Joined 2013
I Agree with "KeepHopeAlive". Also some crossover types will require the tweeter to be hooked up in revesrse polarity to achieve the desired results at the crossover frequency.

The devise you have is probably for checking the polarity of each speaker in a HT system.
 
theAnonymous1

theAnonymous1

Member
Joined 2004
The tester needs to be really close to the driver to work (depends on sound level), so interference from the other driver isn't likely. I rechecked by disconnecting one driver at a time and the results are the same.

I really don't see a purpose for this device now that I think about it. Telling phase between say right/left channels is pretty easy to do with just your ears.
 
Pano

Pano

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Joined 2004
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It depends on the crossover. It's pretty common for the tweeter to be connected in reverse polarity. If there is a 90 deg phase shift in each driver at the crossover point, what's the best way to get them back in phase again?

Yep, you got it. :)
 
K

KeepHopeAlive

Member
Joined 2013
I agree that I wouldn't use a 9V on anything except large subwoofers. An AA battery is sufficient for cone woofers and midrange drivers. Trying to see a tweeter dome move with a battery would probably be the last thing you do with the tweeter!

All that said, we mostly care about the interaction of the tweeter and midrange at the crossover frequency. studying the crossover's effect on phase and predicting phase shift is certainly a viable option.
 
K

Karsten Sømand

Member
Joined 2006
Polarity check

Here is a tool which is not especially cheap, but it is very useful. You don´t need any CD´s to play or similar. Just connect the Phase-It to the loudspeaker terminals and press the button.

You will only hear a little "blop" in your speakers/drivers and the tweeter will not suffer from this test. At the meter you will see a green or a red LED depending on the polarity of the specific driver.

I think this tool is very useful especially if you have speakers with more drivers. The tool is extremely easy to use so you will be quite sure that the results are reliable.

I am not connected to the shown company in any way, but I have been using a similar product many times when working with my cross-overs etc.

Kind regards

Karsten

HiFi DIY products and accessories - Welcome - sidekick-audio.com
 
doctordata

doctordata

Member
Joined 2010
theAnonymous1 said:
I bought this "phase tester" tool just because it was ridiculously cheap (like $9). You play a burst tone that was supplied on a CD and then hold the device up to the driver under test and it will light a green or red light to tell you the "phase". It seems to work in that regard.

Anyway, the first thing I tested it on is my Phase Technology PC80 2-ways. It showed that the tweeter and woofer are out of phase. I checked the internal wiring and the colors match at least.

This probably shows my complete ignorance of speaker design, but is this phase mismatch intentional by the designer? Is this tool even a useful device or just a gimmick?


Thanks
Click to expand...

Very simple test to check phase :
Disconnect tweeter , play a test tone around crossover frequency (REW or tone generator as source ) and listen . connect tweeter and listen again .
If test tone sounds louder : speakers in phase
If test tone sounds less loud : speakers out of phase

Cheers ,

Rens
 
Superstrand

Superstrand

Member
Joined 2013
I have seen incorrectly assembled 2 way systems that use a second order crossover (usually identifiable, consisting of two inductors and two capacitors). If you do not reverse the tweeter leads the tweeter will be 180 degrees out of phase with the woofer. (Make sure that the circuit board has not already taken this I to account)
 
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