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Are L-Pads a good idea in a passive XO?
Are L-Pads a good idea in a passive XO?
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Old 26th August 2019, 09:59 PM   #1
Moondog55 is offline Moondog55  Australia
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Default Are L-Pads a good idea in a passive XO?

Researching a new small 3-Way and several of the XO designs for similar speakers have variable resistance L-Pads on both the midrange and the tweeters.
What are the benefits of using them?
What are the drawbacks other than the high cost?
I don't like padding down a midrange usually but I understand that it is needed to get a proper balance between drivers sometimes.
Locally I can only find one supplier and they are $26- each plus postage and purchasing from O/S won't save anything as International postage has gone through the roof lately
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Old 26th August 2019, 10:37 PM   #2
Galu is offline Galu  Scotland
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I would regard the advantage as being able to change the levels when the acoustic environment of the speakers changes e.g. when introducing new furnishings to the listening room or even introducing the speakers to a different listening room.

Some say the disadvantage is that the contacts between wipers and tracks may become unreliable over time. However, I've been using L-pads on the tweeters of one of my speakers for 30 years now with no signs of deterioration.
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Old 26th August 2019, 11:22 PM   #3
rayma is offline rayma  United States
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Most will eventually develop contact problems and need to be cleaned, or at least exercised enough
to temporarily clear the problem. Fixed resistors are preferable.

Last edited by rayma; 26th August 2019 at 11:25 PM.
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Old 27th August 2019, 01:44 AM   #4
bentoronto is offline bentoronto  Canada
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Are L-Pads a good idea in a passive XO?
Quote:
Originally Posted by Galu View Post
I would regard the advantage as being able to change the levels when the acoustic environment of the speakers changes e.g. when introducing new furnishings to the listening room or even introducing the speakers to a different listening room.....
+1

Absolutely necessary. Just a wannabee-engineer dream you can plan ahead perfectly.

But the corollary is obvious: the mid-range and tweeter have to start louder than the woofer.

Silly not to bi-amp/DSP if you want to meet today's SQ expectations.... and save yourself endless grief that comes when a conscientious builder is going with passive XO. You just dial it in, listen, tweak, done. Repeat next week if not satisfied.

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Last edited by bentoronto; 27th August 2019 at 01:46 AM.
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Old 27th August 2019, 02:27 AM   #5
whgeiger is offline whgeiger  United States
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Quote:
Originally Posted by Moondog55 View Post
Researching a new small 3-Way and several of the XO designs for similar speakers have variable resistance L-Pads on both the midrange and the tweeters.
What are the benefits of using them?
What are the drawbacks other than the high cost?
I don't like padding down a midrange usually but I understand that it is needed to get a proper balance between drivers sometimes.
Locally I can only find one supplier and they are $26- each plus postage and purchasing from O/S won't save anything as International postage has gone through the roof lately
L-Pads are used to match the output level of drivers with different sensitivities. They may be implemented with resistance ladders that provide 1-5 to 3 dB steps selected by strapping. A lot of steps are not required to align driver outputs. Use these on tweeter drive signals only. This arrangement avoids cost and noise inherent with the use of continuously variable or switched L-pads. WHG

Last edited by whgeiger; 27th August 2019 at 02:29 AM.
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Old 27th August 2019, 02:32 AM   #6
Cal Weldon is offline Cal Weldon  Canada
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Are L-Pads a good idea in a passive XO?
Doesn't work for everyone but what I like to do is have a variable L-Pad on hand during the voicing, adjust levels to suit, measure the DC resistance of the Pad when satisfied and replace it with fixed resistors.
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Old 27th August 2019, 02:34 AM   #7
Deano452 is offline Deano452  Australia
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They do have the advantage of an 8 ohm impedance level as well, I've used the ones your talking about Wagner / Loudspeaker kit they are good to 100 watts .
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Old 27th August 2019, 02:35 AM   #8
sangram is offline sangram  India
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Tannoy uses fixed position variable resistor sets on their tweeter that allow +/- 2dB increments.

Typically the shunt resistor is the one to change, as the series resistor doe shift the axial response somewhat.
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Old 27th August 2019, 02:57 AM   #9
eriksquires is offline eriksquires  United States
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I put some thoughts here:


A Speaker Maker's Journey: Crossover Basics - Driver Response
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Old 28th August 2019, 12:19 AM   #10
Pano is online now Pano  United States
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Are L-Pads a good idea in a passive XO?
Ditto what Galu said.

FWIW, DeoxIT is your friend.
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