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plasmodium 26th November 2002 11:35 AM

I like the idea of being able to adjust the level of the tweeter.... a book I am reading suggests using an L-pad to supply an adjustable resistance across and in series with a driver, calls it an L-pad - I am thinking it is similar to a potentiometer, but have never seen one...

does anyone know where to source them from in Australia???

Westrock2000 26th November 2002 12:22 PM

You should read my thread, its very similar to your question. Yes an L-pad is just a big pot, but you may have to wire it differently that just in series to avoid any problems.

mrfeedback 26th November 2002 12:48 PM

Sign off With A Real Name Ok.....DIYetiquette
You can phone Wes Components - Ph: 02-9797-9866
or phone me (08-9405-9779) - I have the full print copy of the catalogue.
Many older speakers used them.
General regard is that they are not for audiophile usage, but can be useful temporaryily for determination of appropriate level, and then replaced with fixed resistors, or a rotary switch with a set of attenuation values.
Experience dictates that the resistive (nichrome ?) wire that they are made from forms a hard oxide film that causes dynamic contact resistance and thereby roots the sound.
Treatment with something like Caig Deoxit helps very much (even brand new ones), and helps long term ensurability.
Other contact treatments can bugger it up.


FrankDIY 26th November 2002 04:11 PM

This is exactly what I am doing, I tweak with L-Pad and use fixed resistor for the final version of the board.

mrfeedback 26th November 2002 11:53 PM


Originally posted by Westrock2000
You should read my thread, its very similar to your question. Yes an L-pad is just a big pot, but you may have to wire it differently that just in series to avoid any problems.

An L-Pad is not a pot - it is 2 variable resistors - one in series, and one in shunt.
The values are configured such that a reasonably constant load is presented to the amplifier, and variable level fed to the load driver.


paulj 12th May 2004 03:41 PM

Looking for L-pads in Australia
I've come across this old thread - I'm looking for L-pads here in Australia. 100 watt, 8 ohm. Can anyone help?

Cheers, Paul

lucpes 13th May 2004 06:31 AM

L-pad is formed out of two resistors, you don't need 100W ratings, 5W or 10W would be more than enough (for the tweeter). Google a 'L-pad calculator' and buy the two resistors :)

paulj 13th May 2004 08:15 AM

Thanks for your advice lucpes. I'll go out and buy the resistors and try some different amounts of attenuation.

A question for you - (excuse my ignorance with circuit diagrams): am I right in assuming the two resistors R1 and R2 are inserted on the "tweeter side" of the crossover capacitor?

Regarding the power handling of the resistors, the tweeters are bi-wired and bi-amped with an amplifier that is 65 w RMS/8ohms per channel. Would you still be happy with 5 or 10watts per resistor?

Many thanks, paul

Andy G 13th May 2004 08:27 AM

This is the fella you want.. and a heap of 5w or 10w resistors

and with a bit of thinking, you can get up to 6 positions with a solid switch between each position......not a variable slide contact !!!

Have fun figuring it out !!!

here's an L-pad calc

paulj 13th May 2004 09:02 AM

Thanks Andy! Can you tell me where I put the R1 and R2 [ between the crossover capacitor and the tweeter or on the amplifier side of the capacitor? (All the diagrams I've seen only show the R1 and R2, not the cap, and I'm a beginner!)

Also, will the 10 watt resistors stand up to the power of my amp? There don't seem to be any resistors rated at more than 10 watts on the Jaycar site. Is there any point in "ganging them up" for extra power handling or does this screw up the impedances?

Thanks, Paul

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