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Old 1st February 2003, 09:46 AM   #1
djdan is offline djdan  Romania
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Default Electric motor capacitor for crossover ?

What do you think about using this capacitor type for crossover .
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Old 1st February 2003, 10:52 AM   #2
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I asked a similar question. mrfeedback supplied his observation.
http://www.diyaudio.com/forums/showt...2690#post82690
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Old 1st February 2003, 12:51 PM   #3
djdan is offline djdan  Romania
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Thank you Ciclotron ,

I can buy a couple of hundred from a banckrupcy store at very low prices ( 60uF/400V at 0,5 $ for example ) and it would be very good if I can use this capacitors at Sound Reinforcement Crossovers .
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Old 1st February 2003, 01:17 PM   #4
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Hi,

This one looks very similar to the Comar ones and is probably the same:

http://www.comarcond.com/home.html (Italian only)

These are primary made for mains use at 50/60 Hz. Most modern ones are polypropylene capacitors although paper ones are still made. They can handle high power and have low losses. But don’t know how they perform at high frequencies. I have used 50uF ones for a flash unit.

Probably they will perform excellent in a crossover. These are definitely much cheaper than “audiophile” ones, mainly because profit margins are much lower and they are made in huge quantities.

For a 50uF/450V PP motor capacitor I paid around $15,- Brand new from stock.

Note that these are rated at AC. A 400V one can handle 600V DC and some are rated 800V short peak. Also nice for tubies.
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Old 1st February 2003, 01:29 PM   #5
Mark Kravchenko
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Re Motor Cap
If you have the equipment do a frequency response sweep similar to that of circlotrons microphone calibration procedure.
It will cost you one cap some time on your computer and you will have a definitive answer.
On the construction of the cap itself it will probably be much more rugged than your garden variety film cap due to the voltage and high surge current requirements necessary in AC motor starting.
It's time to get your feet wet friend.
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Old 1st February 2003, 03:07 PM   #6
Wombat is offline Wombat  Germany
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I use some kind of Motor type MKP 420 Volt for my
mids dome. They are oil filled and sound better than the
audyn cabs i had in before. But the burn in was hitting
my nerves. They sounded different nearly over 2 weeks of
listening until a friend gave me the tip to run them on
220v~ from the plug for a while. I loaded them about
half an hour until they became warm. Now they don´t change
the sound no more and i am very pleased with it.
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Old 1st February 2003, 03:43 PM   #7
EC8010 is offline EC8010  United Kingdom
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Default Cheap at twice the price

At 50c each, you can hardly go wrong. They'll certainly be good enough for sound reinforcement, and rugged too. Go for it - get your feet wet!
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Old 2nd February 2003, 10:43 AM   #8
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I'm not convinced of the need to "burn in" the caps, but if you do decide to stick them across the mains, then 1uF = 3183 ohms at 50Hz so you can't just stick an unlimited amount across the line because it will pull way to much current. While you are doing this, see if your electricity meter goes backwards. There are quite a few urban legends about this sort of thing.
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Old 2nd February 2003, 12:46 PM   #9
Wombat is offline Wombat  Germany
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Hi Circlotron,

it is only 15üf together. I didn´t believe in burn in as you
until i used these caps. The mids i used these parts with where
different from day to day - after the plug they didn´t change anymore.
Don´t know why, but this is what my ears tell me!
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Old 4th February 2003, 08:58 PM   #10
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NO... NO... most emphatically NO!

You cannot run a watt/hour meter backwards with a capacitor, this is urban legand. Most any foolishness you try only makes them run faster..... not slower. They can be made to run backwards via co-generation, but that's another topic!

You can however hit resonance and cause some interesting and exciting side effects by careless experimenting with LC networks across power mains. Be careful!

Cyclotronguy
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