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gear to scavenge. building a crossover

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Forum Name: Advanced Discussion
Forum Description: Advanced discussion area for higher lifeforms
URL: https://forum.speakerplans.com/forum_posts.asp?TID=105012
Printed Date: 29 March 2024 at 9:35am
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Topic: gear to scavenge. building a crossover
Posted By: Bams
Subject: gear to scavenge. building a crossover
Date 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? 



Replies:
Posted By: Elliot Thompson
Date 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.

Best Regards,


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Elliot Thompson


Posted By: studio45
Date 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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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA


Posted By: madboffin
Date 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...


Posted By: service dept Steve
Date Posted: 20 March 2020 at 3:30pm
Fluorescent light fittings usually yield a largish value bi polar capacitor or two.


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Posted By: Bams
Date 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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