Altec Crossover Improvements

**rondo3000** · February 27th, 2009, 10:31 AM

The crossovers used on many of Altec's later VOTT home and commercial speakers, such as the Model 19 home speaker or the 1234 commercial speaker, have a HF level control that not only reduces the overall level of the HF driver, but unfortunely also progressively rolls off the upper treble.

This treble roll-off can be easily eliminated by by-passing the small (.3mh or .5mh inductor in the beginning of the HF section of the crossover. This can be easily done.

In the N1201-8A crossover used in the Model 19, just move a wire from one side of this .3mh inductor to the other side (see the schematic that has been previously posted on this Forum).

In the N1209-8A crossover that is used in many later VOTT speakers, just cut one lead to the .5mh inductor to take it out of the circuit.

In both crossovers there is an 8 ohm variable resistor that is wired in parallel with the subject inductor. It is really just one leg of a standard 8 ohm L pad. I converted this to a true L pad by adding a small jumper wire from the unused lug on the L pad to ground. This greatly expanded the amount of attenuation possible.

Ron Kramer

**BugC** · March 15th, 2009, 01:28 AM

Hi Ron,

If I understand you correctly, what needs to be done is just connect a piece of wire from the (+) input to L2 (2.7mH) thereby bypassing L1 (.3mH) of the N1201-8A .... Then connect another piece of wire from the unused portion of R1 (8ohm variable) to ground for this modification ... This one is easy, cheap and easily reversible! ... What possible effect will this have on the LF performance since L1 is in series with L2? Thanks for sharing this mod.

Cheers!
BugC

**altec-man** · July 1st, 2009, 04:20 AM

Has anyone else tried this mod and what is the function of the .3/.5mH HF choke.

**selmerdave** · July 1st, 2009, 02:22 PM

I would have thought they would have designed in a progressive roll *in* of the upper treble. Do frequency response plots of the Model 19's show this roll-off relative to the plot for a raw 802 (902?)?

Dave

**altec-man** · July 2nd, 2009, 03:24 AM

I can't see why Altec would have designed a xover where the treble rolls off, especially when they were promoting the new 802-8G with it's new Tangerine Phase Plug and better top end response. It just doesn't make sense..