How do you wire an L-pad?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=87284
Printed Date: May 14, 2025 at 2:54 PM
Topic: How do you wire an L-pad?
Posted By: puttster
Subject: How do you wire an L-pad?
Date Posted: December 16, 2006 at 9:26 AM
I have a situation where my center dash speaker is too loud compared to the kickpanel speakers. So I got an L-pad for it. There was no 4 ohm pad available so I got an 8 ohm stereo and connected the three front terminals to the three back ones which (based on what I read on the internet) will convert the L-pad to 4 ohm.
Here is my hookup. hope this comes through. I am calling the front set of terminals on the L-pad "a" and the back set of terminals "b."
amp Left + -----> L-pad1a--L-pad1b -----> centerspeaker +
L-pad2a --L-pad 2b <---- centerspeaker -
amp Right - <--- L-pad3a --L-pad3b
With this setup (sorry about the arrows) I can lower the center speaker volume but... turning the the knob down (counterclockwise) makes the center speaker actually get louder. And, though the L-pad is a 50w one, I think it has a kind of a burning smell to it.
Q: what is the proper setup for my L-pad?
Replies:
Posted By: haemphyst
Date Posted: December 16, 2006 at 11:35 AM
Reverse the amp input side, then connect "centerspeaker +" to "L-pad 3b"... That'll make it "turn down", when you turn it down, and keep in in proper phase.
If your L=pad is rated 50 watts, and you are running it off the bridged channels of the amplifier, it is very possible you are running over 50 watts to it, thus the hot smell...
What amp are you using? Is it capable of more than 25wpc at 2 ohms, in stereo mode? If so, then there is your problem... Most likely well overpowering the l-pad.
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: jvillefinest
Date Posted: December 16, 2006 at 7:39 PM
what is an L-Pad? ------------- 2007 Acura TSX
SQ setup in the works
Posted By: stevdart
Date Posted: December 16, 2006 at 8:16 PM
^^ "What is an L-pad?" Resistors, one in parallel and one in series, to a driver that are used to attenuate the output (the resistors form an 'L' shape if seen in a schematic; and "pad" is a deriviitive of "padding", which describes attenuation of a driver to match the output of the other drivers in the network). This is commonly used in passive crossovers to attenuate the tweeter, but the most common usage of the term "L-pad" is when there is a potentiometer included in the mix. A commercial L-pad as described in this thread is one such that uses a pot to tailor the attenuation. The power handling in question has to do with the abilities of the resistors in how much heat they are capable of dissipating. Phoenix Gold used to market a 4 ohm L-pad and I have two of them in the rear deck of my car. After upgrading amplifiers I don't really need to use them to attenuate the rears, but they work well so it frees up my factory deck fader so that I can use it to attenuate the sub. But you know how the progression of sound systems goes...you upgrade some things which makes something else unnecessary, but you use it anyway because it works just fine and you don't want to mess with it. ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: puttster
Date Posted: December 17, 2006 at 7:30 PM
Thanks fo rthe speedy reply. I rewired as per suggestion and now when i turn clockwise the center speaker gets louder, as hoped. putts
Posted By: puttster
Date Posted: December 29, 2006 at 2:09 PM
I was doing an SPL test and had the center speaker, the one with the L-pad, turned all the way down. Smelled smoke, saw smoke, saw oil leaking out of the L-pad. I was surprised to see this because I have a pretty weak system, 75 W rms/ch . The kickpanel speakers are only 3.5", so I still would like a center speaker for a filler speaker, especially for bass, but it is drowning out the little ones. All the speakers are 4 ohm. What are my options?
Posted By: haemphyst
Date Posted: December 29, 2006 at 4:53 PM
You have two options at this point (actually 3)
1: Use a MUCH higher powered L-pad. An amp, rated 75wpc, @ 4 ohms, can (if the power supply is stable enough) produce as much as 300 watts to a bridged 4 ohm load. You stated your L-pad was rated 50W. You are VERY overpowering this L-pad. I also explained this to you in an earlier reply.
2: Use a lower powered amplifier for your center channel, and dedicate it. You can then set the gain control of the center channel amplifier, and not have to worry at all about the L-pad. (If I had to have a center channel, this is the way I would do it.)
and 3: Forego the center channel all together.
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: puttster
Date Posted: December 29, 2006 at 6:36 PM
I went to radio shack for a resistor but the biggest they had was 1 w. Would an 8 ohm speaker reduce db by 10+? or more like 3? Or would it mess up the other speakers?
Posted By: haemphyst
Date Posted: December 29, 2006 at 7:05 PM
3dB, which you'll barely notice. STILL, you are running FAR too much power through that L-pad! Whether the speaker is 8 or 4 ohms, it's too much power!
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: puttster
Date Posted: December 29, 2006 at 10:00 PM
oh yes, I see that my L-pad is too weak. I don't think that is the way to go. I am surprised that 3 db is all a doubling ohms would reduce after reading here about how many folks want to reduce ohms for loudness. I guess if I could find a 16 ohm speaker it would cut down 6 db? Should I wire it between the left+ and the right- or is there a more effective way?
Posted By: stevdart
Date Posted: December 30, 2006 at 12:50 AM
There are other sources for resistors besides Radio Shack. You can add heat dissipation value by using multiple resistors, either by wiring them in series or parallel. Use the calculators found in the left blue column to find final resistance value, but sum the wattage capacities. I usually buy resistors from Parts Express. ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
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