A7 Driver Phasing

[Altec19]

Greetings All,

While assembling a pair of A7's this evening it occurred to me that I didn't really know if the woofer and compression driver were in correct phase with respect to each other. The crossover (N501-8A) is clearly labeled with Common, LF+, and HF+. The 515B woofer has a + stamped on the frame next to one of the thumb-screw terminals. This terminal also has the number "1" stamped on the end of it. The other terminal has a "2" stamped on it.

Now for my confusion. The 802-8D compression driver has no polarity indication on it but the two thumb-screw terminals are stamped with a "1" and a "2" on the ends just like the woofer. When I remove the endcap there is a green wire leading from the "1" terminal to the diaphragm and a brown wire from the "2" terminal. I would take this to mean that green is negative but that would indicate that the "1" compression driver terminal is of the opposite polarity compared to the "1" woofer terminal.

I didn't pay close attention when the system was disassembled for transport but it appears that the black HF crossover wire was connected to the "1" terminal on the compression driver which would agree with the internal green wire being negative.

What is the correct way to wire an A7 or is there a method to determine if it's correct?

As always, thanks in advance.

Later . . .

[Altec19]

Hi stpower,

The way I have it wired agrees with your explanation. I thought I was remembering something about a need for phase inversion and I was pretty sure someone on this forum could confirm that.

Thanks again for your help!

[Todd W. White]

Hi,

Go here for a previous discussion on this topic:

http://www.hostboard.com/cgi-bin/ult...c&f=3729&t=318

[Altec19]

Hi Todd,

Thanks to you too! Now I know why this works the way it does.

By the way, how's the Model 19 SuperCrossover coming? The A7's in the family room are backups for the Model 19's in the living room . . .

[stpower]

Hi Altec Fan,
Black on the HF driver goes to 1. You want the LF driver and HF driver out of phase because the diapragm on the HF driver is behind the magnet and moves opposite of the woofer cone which is in front of the magnet.

stpower