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Easy way to add a L-pad to Heresy II?


Jsaint

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I have a H II stock crossover on a square cup (circuit board type) have not dissembled yet. The plan is to use a single 100w mono L-pad to adjust mid and hi together. Any one done this before? I need to do this cheaply. Needless to say bypass existing board traces.

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The pad connects into the speaker wires themselves, so you don't have to get into the circuit board. However, with one tweeter and one midrange, you'll need two L-pads as was already mentioned. If you only want to use one L pad, consider using a resitor network instead to adjust the tweeter output. L pads are pretty cheap. They do have ganged L pads , but I didn't see any with an 8 ohm and 16 ohm. Depending on how they are built, you might be able to get ganged 8 ohm and ganged 16 ohm units and reassemble them into ganged 8/16 ohm units. Parts Express: http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=196

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Gentlemen you never fail to please, I just cut a couple traces and kinda figured out one L-pad was not the solution.

I was at a loss till I saw 16ohms, that is what I needed to know.

So far. I will post a picture here in minutes of my cut traces. Ignore the jumpers now that we know a second pad is needed.

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Done properly (L-pad between the network and the drivers), a 15W rated L-pad is all that you will need.

The autotransformer on the Heresy raises the impedance on the input side to over 70Ω, so you can't use an L-pad there.

Buy two of each of these:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-274

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-248

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-254

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Done properly (L-pad between the network and the drivers), a 15W rated L-pad is all that you will need.

The autotransformer on the Heresy raises the impedance on the input side to over 70O, so you can't use an L-pad there.

Buy two of each of these:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-274

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-248

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-254

OK so, L-pads on the output leads, Hi 8ohm 15w / Mid 16ohm 50w, fix my trace cuts, pads are generous enough due to existing filtering. Thank you for advice. Jason

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There is an alternative.

The autoformer used in the net can be removed altogther and the 1.5uF place in parallel with a 22uF(?). The addition of L-pad will then provide attenuation from 0dB to the limit of the pad.

By placing the pad between the autoformer and the driver, as is currently being proposed, the system is attenuated at -10db with the pad set at 0dB. This is acceptable if the goal is to reduce further the attenuation currently provided by the autoformer,

Should the desire of the "enthusiast" be to increase the output, say to -8dB, then removal of the autoformer is the option and the destruction of the net and PWK's vision complete!

(some tweaks to the net design are here: http://www.northreadingeng.com/Forums/index.php/topic,18.0.html )

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