Some basic questions on Inductors and Capacitors

[Ronj]

Dear DIY Brotheren,
I have few questions on the Capacitors and Inductors… Mainly



1) In the attached picture, you will see maroon colored caps. The seem to be made by Panasonic right? Now the question are they polyester or Metalized polypropylene? How do I find that out? Googling with what’s written on them didn’t help me much…


2) My best guess is they are polyester, that brings to my second question, I know polypropylene has a better performance in audio applications, but how about polyesters? Are they worse than even those black Bi-Polar electrolytic caps in the picture in audio application? Especially in cross-overs? I wanted to parallel two of them for a 1.2µF for a super tweeter. Should I stick to an electrolytic bi-polar 1.0µF(which I have, not in the picture) or these polyester ones are good enough?


3) Also what you see in the picture are few coils. Two of them again are color coded, maroon colored through hole axial mount coils of 82µH. Now the question? Do inductors have a power rating? They measure 2Ohm DC resistance on my DMM. Now How do I know the current handling capacity of these coils?


4) Can I use on my Mid-range cross over circuit for 82µH? Crossover frequency is 2500Hz in my particular application. As my 8” mid-bass can’t reach there. And the 8Ohm mid range, I use can only reach a max of 12kHz beyond which a soft-dome tweeter takes over… Now the question is can such coils take enough current to be in the cross-over in series to the mid-range?


5) The other coil in the picture is 39µH and they are copper-wound? How abt them? How much current they will be able to handle? Where I get that information?


Sorry for the long post. And sorry some of the questions look stupid… Your replies are appreciated…


Thanks
Ron

[picowallspeaker]

5) Useless in audio
4)I guess that at 12 KHz the tw takes over ...but in which direction ??? With a tone generator you can easily define the real magnitude of a frequency .
Usually a mid-wf starts to decrease its efficiency in reproducing the high frequencies at an order on magnitude lower ,around 1,2 KHz ( it depends mainly on its diameter ).
3 ) same as 5)
2) Take a look at some web shop , or search for crossover ,X-over components .
1) Now !! You have some big 6u8 F ( something dielectric) capacitors .
They might have an use in crossovers . Put them in the circuit and listen . If making a
comparison with other types of cap in the same circuit you'll hear some improvement , nothing ( more common ) or some downgrade , then you'll be able to tell us if they are woth or not .

[rongon]

There is a good discussion of the relative properties of various capacitor types for use in audio in Morgan Jones' "Valve Amplifiers." He measured a bunch of different kinds of capacitors for electrical series resistance (ESR) and dielectric absorption (DA), or how a material acts after discharge, whether it charges itself back up after discharge.

Basically, electrolytic capacitors have high ESR and high DA, so are the least good for pulse applications (like audio). Where 1. is best (lowest ESR and DA) and 10. is less good (higher ESR and/or DA):

1. Teflon film
2. Polystyrene film
3. Polypropylene film
4. Polycarbonate film
5. Polyester (Mylar) film
6. Electrolytic
7. Ceramic

Also, there are some who claim that film-and-foil construction sounds better than metallized film construction, because the metallized film is sputtered, so has irregular thickness of conductive layer which can add self-noise. I personally have enjoyed the sound of Axon tin foil and polypropylene film capacitors, so I believe there is some validity to this. But I don't *know* this. That is my *opinion*, based on my own limited experience. YMMV.


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[DrDyna]

Originally Posted by rongon

Basically, electrolytic capacitors have high ESR and high DA, so are the least good for pulse applications (like audio).

I believe electrolytic also have shorter lifespans than their poly counterparts as well.

IMO the only reason people ever have to use electrolytic caps is cost and size. You can get a 250 or 300 mfd electrolytic cap that's the size of your thumb for less than 5 bucks in most cases, where a film-type cap would be closer to $80 or $90 (on the cheap side, some are much more) and can in some larger values be nearly the size of a soda can.

[Ronj]

Thanks a lot....

Someone told me those caps are
1) Metallized polypropylene, here's the datasheet courtesy of Farnell:
http://www.farnell.com/datasheets/817052.pdf

And the Inductors...
Yeah those coils I had them with me... so wanted to check on a low power(2W) application, in a lower High Pass Tweeter/mid-range...Well certainly I never thought I could use them for my woofer. But for a midranger/LowerHF tweeter which cuts in at around 3Khz... I thought they might do? May be they won't... These in the proposed application, have another 16µF in series. So the power/current handling will be much less... I did account for that 1.5Ohm coil resistance in my cross over design anyway... DC resistance of the closed basket driver I am using for midrange is 8Ohm... So together it will read something like 9.5Ohms... Thus the question...

Thanks a lot for the info again...

[Andrew Eckhardt]

Does your ohm meter read 0 with the leads shorted?

[Ronj]

Originally Posted by Andrew Eckhardt

Does your ohm meter read 0 with the leads shorted?

Yup it does most of the time! I already accounted for the offset(if there any) anyway... Only the axial pin through "resistor" type inductors have such high DC resistance. Other coil shown and my Woofers big copper wound coils register close to "0" ohms.

[Andrew Eckhardt]

Ok. I thought you were measuring 1.5 on the bobbin core inductors.

I was going to suggest that they'd be okay for a couple watts, but those axial lead jobs... I dunno. I'll bet you'll get some kind of "sound" out of those.

[rongon]

Someone told me those caps are
1) Metallized polypropylene, here's the datasheet courtesy of Farnell:
http://www.farnell.com/datasheets/817052.pdf

Yup, "WF" means metallized polypropylene. Those should be some decent capacitors.

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