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gear to scavenge. building a crossover

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Bams View Drop Down
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    Posted: 20 March 2020 at 11:40am
So here you are.. a quarantine with no end in sight, a load of acceptable drivers and wood, websites enough with calculators but no components for crossovers.. any oldtimers who can tell which unused gear to scavenge for coils and so on? 
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2020 at 12:02pm
I usually use parts stemmed from Power Supplies used in old desktop computers when I need a quick passive crossover.

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Edited by Elliot Thompson - 20 March 2020 at 12:03pm
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2020 at 2:19pm
+1 to what Elliot said - power supplies are where you want to look for them THICC components

Motor start/run caps are non-polarised and usually quite large values. Otherwise large non-polar caps are quite rare outside of audio gear. You can parallel lots of smaller caps together though, and end up with a composite cap that actually has a very low ESR and potentially better high frequency performance than a single large unit.

For inductors, you're not likely to find anything over 1mH, wound with decently thick wire, anywhere but in an actual crossover - but, there's a lot of wire in transformers, so look at hacking those apart, and rewinding the thick secondary wire onto another former. Input/output chokes on SMPS are sometimes quite beefy, might just be about the right value for a tweeter crossover? Not usually large values though as they're there to filter out remnants of a 100kHz+ switching frequency, not our <20kHz audio range.

The big white 25 and 50 watt ceramic power resistors are not very common, but smaller 5 watt types can be found in power supplies. Again if you parallel them you can add up the wattages, but remember resistors don't really mind running red-hot, at least until the solder melts ;)

I'd reccommend getting one of the "Transistor Tester" multi-component analysers, if you're building from salvage - much less fiddly than a normal probe multimeter for checking the values of stuff as you pull it out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2020 at 2:58pm
Scrap electric motors can be a good source of enamelled copper wire (also known as "winding wire" or "magnet wire") for making inductors.
A few years ago I would also have suggested CRT video monitors (for the scanning coils) but they've probably all long gone to landfill...


Edited by madboffin - 20 March 2020 at 3:00pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote service dept Steve Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2020 at 3:30pm
Fluorescent light fittings usually yield a largish value bi polar capacitor or two.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bams Quote  Post ReplyReply Direct Link To This Post Posted: 21 March 2020 at 7:14am
This is why i love speakerplans! that's up to the attic for me then.
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