Installing a 3-prong attinuator?

**Old Guy** · November 25th, 2012, 05:26 PM

3 is unused. 2 is wired to ground, thru a series resistor that doesn't allow it to reach zero- ie at least 2 ohms to ground. 3 is just hanging out with nothing to do, sorta like me.

**gortnipper** · November 25th, 2012, 07:27 PM

I noticed in the photo that the other lpad (MF?) is wired with tap 1 unused...?

**rontec** · November 25th, 2012, 08:02 PM

Originally Posted by Earl K

This L-pad seems to be configured as a basic speaker volume control.
Depending on the value of the L-pad from mostly on to full off. Yes?

**Panomaniac** · November 25th, 2012, 08:22 PM

Yes, that's how they work.

Correct A.B.. In this use it is for EQ, not overall level, so you do want the impedance of that section to change.. Might not even be an L-Pad, just a power resistor (pot).

**Cal Weldon** · November 25th, 2012, 10:12 PM

[QUOTE=Old Guy;1844179] then the mids attenuated. <snip> Ta-da! Here is the HF portion [QUOTE]

That looks like the MF attentuation, or is that what you meant? And why are they doing that on the HF as well?

**Old Guy** · November 26th, 2012, 06:35 AM

[QUOTE=Cal Weldon;1844198][QUOTE=Old Guy;1844179] then the mids attenuated. <snip> Ta-da! Here is the HF portion

That looks like the MF attentuation, or is that what you meant? And why are they doing that on the HF as well?

It's two filters. Not just one. Each filter has a level control In this circuit they are just variable resistors.

When used as an L-pad it is wired AFTER the filter, not as part of it.

**gortnipper** · November 26th, 2012, 03:49 PM

So, why is the HF section wired with tap 3 unused, and the MF wired with tap 1 unused?

**Old Guy** · November 26th, 2012, 04:22 PM

Originally Posted by gortnipper

So, why is the HF section wired with tap 3 unused, and the MF wired with tap 1 unused?

Because they are not used as L-pads. I've been trying to say they are part of the complex filter (since it is two combined).

http://home.earthlink.net/~jmarkwart...1201-8aRev.pdf

Just look at the schematic- do you see one AFTER the filter? An L-pad goes between the filter and the load. As has been said, you can use just one section, and it is a variable resistor.

See Rontec's post...the crossover normally would be BEFORE the L-pad. In the model 19 the VARIABLE RESISTOR- not being used as an L-Pad- is IN the filter, or complex filer as it is two combined...hope it makes more sense now? An L-Pad only varies VOLUME (theoretically), where as in the Altec they are used to vary bands not the entire out put. I think your mistake is you think there is a separate HF section- there is not. there is only one driver. So you have to vary the response in the crossover, you don't have a mid and high driver you can turn up and down independently. THEN you would use L-pads. I apologize if not clear, but a LOT of engineering by better men than I went into the 19 crossover.

**gortnipper** · November 26th, 2012, 06:02 PM

Originally Posted by Old Guy

Because they are not used as L-pads. I've been trying to say they are part of the complex filter (since it is two combined).

http://home.earthlink.net/~jmarkwart...1201-8aRev.pdf

Just look at the schematic- do you see one AFTER the filter? An L-pad goes between the filter and the load. As has been said, you can use just one section, and it is a variable resistor.

See Rontec's post...the crossover normally would be BEFORE the L-pad. In the model 19 the VARIABLE RESISTOR- not being used as an L-Pad- is IN the filter, or complex filer as it is two combined...hope it makes more sense now? An L-Pad only varies VOLUME (theoretically), where as in the Altec they are used to vary bands not the entire out put. I think your mistake is you think there is a separate HF section- there is not. there is only one driver. So you have to vary the response in the crossover, you don't have a mid and high driver you can turn up and down independently. THEN you would use L-pads. I apologize if not clear, but a LOT of engineering by better men than I went into the 19 crossover.

Yes, that makes more sense to me now. Sorry, I can be slow!

The reason I am asking this is because I have been mucking about with a L-pad wired onto (but after) my crossover as both a variable resistor and an L-pad in order to tune the GPA-IIIs horn to the cab/room better. I found that by using it as series-R instead of an L-pad, the sound was slightly better - a bit more "clear" is I guess is how I would characterize it, and I am trying to better understand why.

**Old Guy** · November 26th, 2012, 06:23 PM

Originally Posted by gortnipper

Sorry, I can be slow!

The reason I am asking this is because I have been mucking about with a L-pad wired onto (but after) my crossover as both a variable resistor and an L-pad in order to tune the GPA-IIIs horn to the cab/room better. I found that by using it as series-R instead of an L-pad, the sound was slightly better - a bit more "clear" is I guess is how I would characterize it, and I am trying to better understand why.

Don't worry. I can be slower! Have had more years to practice!

There are so many variables. Could be: L-pads don't track well. Maybe having a higher load flattens the crossover response. maybe it's not flatten the response but instead enhancing freqs you like...see what I mean? Nobody else has a setup exactly the same. That's why testing beats predicting every time. I just resign myself to some things I won't ever figure out...such as Redheads.