288C Terminal Polarity

[magnarc]

Greets all from Sydney...

I have several 288C's, all of which have the older diaphragm in them. The driver terminals are marked 1 and 2.

The actual diaphragms are marked on one side L1, and I have forgotten which terminal L1 gets connected to, 1 or 2, or if it actually matters.

Cheers

Nat

[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....

[magnarc]

Todd, thanks.

Not confused, and was aware of what you wrote, it had just been a long time since I opened up my 288's, and one had terminal 2 connected to L1, the other 288's had terminal 1 connected to L1.

Needed a clarification on what terminal on the diaphragm matched which terminal on the outer 288 cover.

Cheers

Nat