Determining When Tweeters are in Phase - diyAudio
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Old 9th June 2013, 09:43 PM   #1
gassit is offline gassit  Australia
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Default Determining When Tweeters are in Phase

Hi,

With some second-order crossovers, it's recommended to reverse the phase of the tweeters.

How can you tell when the tweeters are correctly phased?
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Old 9th June 2013, 10:50 PM   #2
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If they are out of phase, one pushes as the other pulls, the sound in not natural.
There is no centre for the audio and it is very noticeable.
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Old 9th June 2013, 11:16 PM   #3
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Default phase

If you have access to a acoustic measurement system all have to do is perform a frequency response test. Then switch the polarity of the tweeter and if the phase is correct a deep dip will be present. I use this technique for all types of crossovers. If you don't have a measurement system there is a few free programs that use computer sound cards. Speakerworkshop is one I like
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Old 9th June 2013, 11:19 PM   #4
jcx is offline jcx  United States
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if the XO design requires phase reversing a driver then there will be a pronounced dip in the acoustic output frequency response at the XO frequency if you get it wrong

most physically small condenser mics are fine for audio midband measurements - no calibration needed - you are looking for a deep notch on axis, at listening distance
best done where reflections can't interfere, speaker lying on back outdoors is simplest
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Old 9th June 2013, 11:51 PM   #5
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Default phase

Another free program is holm impulse HOLM Acoustics

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Old 10th June 2013, 12:30 AM   #6
system7 is offline system7  United Kingdom
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We've all taken speakers apart and then found, in our excitement, we have forgotten to note the wiring polarity!

The good news is that 99% of speakers wire IN PHASE.

As noted, if it's wrong, you get a hollow vague "phasey" sound around crossover frequency.

Really the only exception is where the tweeter is on a simple first order capacitor circuit and the bass is on the usual bass-boost coil. This wires out of phase.

To determine the positive terminal, which is often marked with a red dot, a 1.5V battery briefly touched positive to positive will make the driver move forward.

A 3 way speaker is more complex, and depends on the filter orders. You could find a similar type of speaker here and compare too:
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Well, there it is! Best regards from Steve in Portsmouth, UK.
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Old 10th June 2013, 02:03 AM   #7
gassit is offline gassit  Australia
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Thank you all.

And as it's way past your bedtime, a good night to you System7.
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