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Old 29th December 2011, 09:08 PM   #1
kach22i is offline kach22i  United States
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Default L-Pad variable resistance dial in tweeter volume

What are the do's and don'ts of installing an L-Pad variable resistance dial in tweeter volume knob?

Like these:
L-PADS from Parts Express ship same day and come with 45 day money back guarantee. Free Shipping Available. Order free 10,000 product catalog.
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My tweeter is 6 ohms, the woofer is 8 ohms. There is no real crossover, I'm using a capacitor to frequency protect the tweeter, and a resistor bridging the positive and negative tweeter leads for now. This resistor might go away if the L-Pad is up to the task of the considerable knock-down and flexibility I'm looking for.

Any warnings or suggestions before I go down this path?

Can you help me pick out a good value one?
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Last edited by kach22i; 29th December 2011 at 09:10 PM.
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Old 29th December 2011, 11:25 PM   #2
AllenB is online now AllenB  Australia
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Since these will dial in both a series and a parallel component of resistance, they allow you the freedom to adjust your levels while maintaining a (reasonably) constant impedance so that you don't have to constantly adjust any of your other components.

Use this closest to the tweeter. There will be minor variations in the impedance, especially as you turn them further. If it is designed for 8 ohms, then I would assume from this point on that you have an 8 ohm tweeter whenever you calculate capacitor values, etc.

When I used to use these, I'd have issues with the contacts becoming dirty and dropping out at some points in the rotation.
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Old 30th December 2011, 01:24 AM   #3
kach22i is offline kach22i  United States
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Thanks AllenB, from what you have said it looks like this line of thought has possibilities. More research is ahead, but I like learning by doing so that is not a problem.

I read in the review/comments section of the parts link I provided that many 8 ohm tweeters actually measure closer to 6 ohms. I'll measure mine to get a more accurate idea of what I'm dealing with.
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Old 30th December 2011, 03:11 AM   #4
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The thing is, that the further you turn these the greater the influence they have. They will take any impedance, high or low, and eventually turn it into a resistive 8 ohms the further you turn them.
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Old 30th December 2011, 03:47 AM   #5
kach22i is offline kach22i  United States
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I just ordered the L-Pads (the cheap $10 ones), going to have some fun and learn new things (also called mistakes).

While ordering I selected a couple lower value capacitors to raise the frequency in which the tweeter jumps in (will be removing the old ones first). This should eliminate the slight lisp to Johnny Cash's voice and the extra edge I heard on the B-52's. Lowering the volume will also help - of course.

I found this site and calculator to be very helpful in capacitor selection.
Car Audio - Speaker Crossover Chart and Capacitance vs. Frequency Calculator(High-pass)

My new speakers already sound better in many ways than my old Martin Logan Aerius speakers. This is a very unconventional design I'm working on, if it all works out I'd like to share more of the details. However, I don't want to show off anything half-baked. These are a bit DIY looking, but very artsy looking and crafted as well.

Thank you AllenB for all of your guidance and patience.
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Old 3rd January 2012, 02:29 PM   #6
kach22i is offline kach22i  United States
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UPDATE: 01/03/2012

The L-Pad's are installed:
http://www.parts-express.com/pe/show...number=260-255

They are working as planned, I have the new cap after them.

They are dialed up only 1/4 of the way, I swear they are on just a tiny bit when turned down all the way.

Everything is working out and sounding great, thank you to everyone which posted in this and the prior thread and helped out.
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Old 3rd January 2012, 02:45 PM   #7
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I use that L-pad too and find it works fine. I know others will say it 'dirties' the sound but i think they are benign. What drivers are you using?

Zilla
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Old 4th January 2012, 03:25 AM   #8
kach22i is offline kach22i  United States
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Quote:
Originally Posted by Godzilla View Post
I know others will say it 'dirties' the sound...
I read that they get dirty over time and cause popping and sound dirty.

Now that I have a setting I like, how do I measure the resistance? Just measure at the leads?

I suppose I should plan on replacing the L-pad with a set of resistors eventually.

I do like the flexibility though.

I once had a pair of Audio Lab speakers with Fisher drivers (1979-1989), they had a tweeter dial of some sort, must have been an L-pad.
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Old 4th January 2012, 04:02 AM   #9
AllenB is online now AllenB  Australia
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Yes, most likely.

If you want to measure, disconnect the middle terminal. Use a meter to measure between the middle and ground terminals to find the resistance to put across the tweeter. Measure from middle to the input terminal for the series resistance.

Measure both sides in fact, and consider the differences. This might help you to identify differences between the units, human error, and room differences. In some rooms the reflections will make one side seem more loud than the other, and will shift the stereo image.
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Old 4th January 2012, 02:42 PM   #10
kach22i is offline kach22i  United States
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Thank you AllenB.

I'll give this a try soon, but need to get some other work done first.

Cheers, George/kach22i
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