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Midwest Audio Fest

It’s that time audio enthusiasts!

Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project.
We are excited to see all returning participants, and look forward to meeting some new designers this year, as well!

Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans.

We hope to see you this summer!

Vivian and Jill
2 of 2 < >

Midwest Audio Fest

It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
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Help with ESR

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  • dynamo
    started a topic Help with ESR

    Help with ESR

    I know I could measure it myself however I don’t have access to the capacitor at the moment…

    Could anybody give me an educated guess at the approximate ESR of a new 47uf Electrolytic capacitor? Bennic specifically.

    thanks

  • dynamo
    replied
    Thanks guys, good info!

    Leave a comment:


  • neildavis
    replied
    Originally posted by saabracer23 View Post
    Well esr isn’t stable. It changes with frequency I believe so I wouldn’t know the answer to that question, sorry.

    Dan
    That's correct. ESR is the Dissipation Factor divided by (2*Pi*F*C). Dissipation Factor isn't a constant, but it usually doesn't change more than a factor of 2 across audio frequencies, so it is often treated as a constant. So for a given capacitance, ESR is inversely proportional to the frequency. The ESR for electrolytic capacitors is usually specified at 120Hz. That means a capacitor specified as having a large ESR may have very low ESR at crossover frequencies..

    A lot of modern "audio grade" NPE capacitors have a dissipation factor in the 5% range, which will result in "negligible" ESR. If the DF is 10% or higher, you should probably use a modeling tool that takes ESR into account, especially for high-order crossovers. But the ESR isn't going to change the response much at all if you use 5% DF capacitors and typical crossover types.

    I just picked a NPE at random from the PE catalog: https://www.parts-express.com/33uf-1...citor--027-350 ..It's got a 5% DF, which I assume is typical of the NPE capacitors sold at PE. Don't worry about ESR with these caps.

    You can verify the effect of ESR on the response with PSD-Lite. Click on "Options" in the Passive Crossover Module and you can enable the ESR calculations. Just specify the DF and the program will add the ESR to all capacitors and recalculate the response. Spoiler: you won't see any significant change in the response unless the DF is 10% or higher.

    Leave a comment:


  • craigk
    replied
    ESRis the total in phase AC resistance of all parts and materials in the cap. ESR is not a constant with cap size.

    Leave a comment:


  • dynamo
    replied
    That’s what always kind of confused me I guess..

    what frequency were the readings you provided taken at?

    Leave a comment:


  • saabracer23
    replied
    Well esr isn’t stable. It changes with frequency I believe so I wouldn’t know the answer to that question, sorry.

    Dan

    Leave a comment:


  • dynamo
    replied
    Thank you very much! This is a dumb question but should I then use that esr number as the resistance of the component like the dcr of an inductor? I.e. is a npe, with it’s inherently high esr, the same concept of a poly cap damped with a half ohm or so resistor?

    Leave a comment:


  • saabracer23
    replied
    I measured a good number of 47uf electrolytics I have ranging from 16v to a 100v rating, both polar and non polar. I saw a range of 0.46 and 0.95.

    Dan

    Leave a comment:

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