Got A Couple Dozen L-Pad Attenuators- What To Do With Them?

[stevieb]

All pictured on this webpage:

http://www.theelectronicsshop.co.uk/Accessories/levelcontrols.htm

3 each, Order code 962-110
2 each, Order code 962-150
5 each, Order code 962-250
8 each, Order code 962-160

I see they range from 15 to 100 watts power handling capabilities, and all have Impedance of 8Ω ±20% and Attenuation- 0dB to ∞dB

Most are NOS- the 962-160's are all made in Japan, the others apparently ROK.

I know they are sold to, say, be mounted on the wall of a room and adjust the volume of speakers in that room (without having to go to the source,) and this http://www.colomar.com/Shavano/lpad.html talks about using them for tweeters and mids- are there any other uses for them?

I would love to have a 5-25 watt guitar amp attenuator,- the kind that drives power tubes hard so you get power-tube distortion- can I use them to build those attenuators? This guy http://www.regiscoyne.com/ampwell/ apparently did- anybody use such an attenuator? And this guy http://www.amptone.com/wallmountspeakerattenuator.htm went super-simple, just mounting an L-pad to the bottom of his amp. Is this an example of lunacy, or elegant simplicity? (I know there is some yahoo who is selling "attenuators" on ebay for about twenty bucks- they are NOT real attenuators, but rather, as best I can tell, master volume controls that you plug into an amp's effects loop. Yuck.)

Anybody have any use for any of them?

I just read this about L-Pads:
3.4 "L-Pads"
The "L-pad" is a resistive device with two variable impedance pads. It has constant impedance with respect to the amplifier, usually 8 or 16 ohms. "L-pads" were developed to control the output level of tweeters and midrange speakers without the high current typical of woofers. The "L-Pad" sounds great, has minimal phase shift, is very linear up to its power rating but has a major drawback, which virtually eliminates the “L-Pad” from use in multi-room and custom installation situations. Because the "L-pad" is a constant impedance device, at lower volume settings the "L-pad" converts
all of the energy not sent to the speakers into heat which can be considerable. Even in a moderately powered system, "L-pad" reliability is low and lifetime is short. Worse yet, there is a fire hazard present when using "L-pads" to control full range speaker level signals.
http://www.knollsystems.com/tech-docs/whitepap.pdf

That does not sound good in general, and seems to bode badly for my guitar amp attenuator idea.. But wait, they are used to "control the output level of tweeters and midrange speakers without the high current typical of woofers," so they don't have those drawbacks in those applications?

On a related note, isn't a "speaker motor" just a speaker with no cone, thus it produces no sound? THIS guy http://amps.zugster.net/articles/attenuation says it is...

 

[mshilarious]

It's all down to the rating of the pad. That website is devoted to home theater design and probably his experience is based on the stuff designed for in-wall. There are plenty of more robust L-pads you can get, but 100W should be capable of sustaining that level long-term or it was improperly rated or just a piece of crap to begin with.

Properly rated L-pads are fine for amp attenuators. Guitarists will always find a reason to object to anything, the criticism is that speakers aren't resistive loads (which is true), and that changes their "tone". Of course every change to "tone" that doesn't pass the muster of purity must always be a negative change, whereas you'd really expect that to be somewhat random, but there aren't a lot of double-blind tests being done on guitar circuitry . . .

You are correct on speaker motors, although they won't behave *exactly* like a speaker because they aren't loaded with an air mass. More sophisticated networks are possible to create a more accurate impedance model, but at that point I doubt anybody really cares that much . . .

 

[dintymoore]

Radio Shack sold some in the 80's and 90's I bought.

I had a pair of Peavey 1 12" + horn speakers and the piezos were pretty evil. For awhile we'd jam mic windscreens and black gig socks in the horns. I ended up putting L-pads on the horns and it helped some.

Here's a MacGyver:

I was on a gig with a monitor right by me and the mixer far way. The unit has an L-pad in a pill container and a cable that went to the power amp and a cable to the monitor speaker. It was attached to a spring clamp so I could clamp it on a stand. Not the prettiest but it was nice to have control of the monitor right there. To me as long as you use them within specs and they don't feel excessively warm I wouldn't worry.