In Phase ?

[chris haberland]

How can you tell that my voice coil,diaphram for my 288's is wired in phase.I dont see any marks that tell me negative from positive.Thanks chris.PS i did a search on this, found nothing.

[scott fitlin]

In pro circles we use a phase checker! Its a device that you hook up to an aux input and then yopu have another handheld unit! When you hook this up and turn up the volume youll hear a clicking sound. You point the handheld unit at the driver/horn and itll light up red or green. Green indicates your in proper phase!

These devices are available from www.partsexpress.com and are reasonably priced! Its an invaluable tool when working on large systems!

[scott fitlin]

or you can take the back of the driver off so you can see the diaphragm. Hook up a wire to the terminals and use a 9 volt battery to see which way the diaphragm is moving! But youll have to do this with the driver off the horn so you can open it up to see which way the phragm moves when you put the battery to it! Positive phase would be the phragm moving forward.

[Todd W. White]

All older Altec speakers used terminals marked with "L1" and "L2". These are carryovers from the Western Electric days. Here's what they mean:

When a voltage is applied to a terminal connected to the voice coil and the coil is forced OUT of the magnetic gap, the WE engineers designated that terminal "L1". The terminal that caused the voice coil to move into the gap was labelled "L2".

In other words, when a speaker produces a compression wave TOWARD the listener, the terminal it is connected to is where the positive speaker lead goes. HOWEVER - in Altec HF compression drivers, the voice coil/dome assembly moves INTO the voice coil gap when creating a compression wave toward the listener, rather than AWAY from it like a woofer does.

SO - in Altec HF compression drivers, you would connect the positive lead to the "L2" terminal, because it moves the voice coil TOWARDS the listener. "L1" would connect to the negative lead.

In woofers, however, the opposite is true....

Confused?

Hope you're not anymore...

P.S.: Be sure you have physically aligned the high and low frequency components, lest you recreate the Eleanor Powell tap dancing problem....

[ngccglp]

Hi Todd,

But an Altec 2nd order XO e.g. N501-8A is 2nd order XO and therefore the black leads (Common) should be connected to the L2 Terminal right?

Thanks

[LICORNE]

.
Another way is to use a kleenex tissue and a 2 volt battery if the tissue goes out then your pushing so that is your positive.

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[ngccglp]

Hi Convergence,

My problem is not about the polarity of the 288, I have already figured that out. The puzzle is: do I connect the + lead or the - lead from the 2nd order XO to L2 (Compression). Since for 2nd order XO the HF and LF is 180 deg out of phase, theoretically the - lead should go to the L2 terminal. Is this correct?

[donaldpatten]

Phase or polarity can be tested with two mics an amplifier and head phones. Play mono sound though the speakers: music, voice, noise, just not a single tone and listen to the sound the two mics pickup. Place both the mics close to one speaker. Move one mic to a different speaker leaving the other as a reference. Try reversing the leads to one speaker and you will hear the sound shift from the middle of your head outward when the speakers are connected reversed polarity.
A cassette recorder may be used as the amplifier.
Radio Shack has low cost omni electret mics.
Don

[LICORNE]

I logged out to early. Phase shift and time alignment. You will need a realtime analyser or RTA. Since time delay causes the speaker to be out of phase.

If you think your system is really out of phase
either try to rent a unit or buy the necessary equipment and soft ware for your computer.

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[ngccglp]

Thanks Donald,

You gave me an idea, I managed to dig out a mono limited edition CD of Pink Floyd's Piper (I think this is the only mono recording I have). This is very effective, the sound should be dead centre, right? In that case, the - lead should go to L2 i.e. the HF driver is wired out of phase from the woofer, as a 2nd order XO should.