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Get familiar with the reaction system: Introducing the Reaction System
Comments
Kornbread's thinking these will never see more than 30v.?
@dcibel Don't know if you were kidding about the cheap panasonic film caps, but I ordered several of them and some will be going in these speakers.
I've been informed by a knowledgeable person in the past that the AC voltage involves swings across 0 to where the magnitude can exceed 100V swing in some cases, and this is why 250V caps are considered the minimum requirement. Were these for a preamp filter, I feel they would be fine.
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I'm not someone who uses math much in my profession. I've probably forgotten more HS algebra than I care to admit. Plus I don't work in Base 10 at my job. I deal with 30, 29.97, or 24 frames/sec. Then there's numbers associated with the camera exposure triangle - F-stops, shutter speed, & iso , which must seem very strange to non-photographers. I always have to look things like this up -
https://www.cuidevices.com/product/resource/calculators/speaker-power-calculator
I’m not saying it’s good or proper, but a lot of those rack system monkey coffins of the 90s had 50v npe caps in them and I’ve never seen an exploded cap in one. Keep the amp a reasonable size considering the math on the cap rating and I think you are ok.
50 volts peak into an 8 ohm load is 156 Watts RMS. With a small driver like that I'm guessing you'll be powering it with something more like a 15 WPC amp.
As a "piece of mind" check, load your filter circuit and driver files into Xsim and call up the voltage across component graph. Don't forget to tune the source to your expected power level. I bet the voltage across the cap is way below 50 volts at a sane power level. In a nutshell I wouldn't hesitate to use those Wima caps in that application.
Easy Peasy. Thanks Craig! I had no idea you could tune the source in xsim. This will be very helpful.
With the source tuned to 50 watts, it shows 13 volts across that cap. That little ns3 is rated for 40watts and the TPA3250 chipset, as configured in the fx502a pro, is only good for 37watts. Since this will be gifted as a pug-n-play system (speakers/amp/cables) I'm thinking the 50v caps will be fine.
Xsim shows it will take over 700w for this cap to see 50v.
700 watts of power at 2000 Hz!!!! Holy ear drums Batman!
Settled on this filter. I'll run it past boy's ears and compare it to his pair of unmodded Pico. I'd post the crossover but I don't really trust my ears yet and afraid you guys might laugh.
Ungated, green is w/filter. When measuring something like this that will have a lot of stuff in very close proximity, is it preferred to gate the response, or no?
Thanks in part to the tiny wima caps, it all fits on 1.75" x3.75" which should fit through the tiny ns3 woofer hole. The inductors are from reclaimed motor windings so not quite the awg I would prefer but adequate. And no, they are not nice and pretty like @squamishdroc crossovers.
Don't use peak voltage to calculate power, for AC use RMS voltage. In audio land you'll often see companies quote "peak power" which isn't a real thing in AC land. Power is power and its calculated from RMS voltage. What they're quoting is the DC power if you clip the amp so hard that you're simply making a square wave from rail to rail. As you clip an amp and the sine wave becomes closer to a square wave, RMS voltage increases closer to the DC rail voltage, and thus power is increased as well over a clean sine wave of the same peak voltage.
Anyway, to the topic at hand. Ive owned some "vintage" Heathkit speakers that had caps rated for only 16v in them and they survived. Assuming the caps are rated 50VDC, that would have a rating of about 30VAC, or 112.5W into 8 ohms. No, it's not likely you'll damage them from normal use in a speaker.
@Kornbread sorry, I don't remember which panasonic caps, my brain is a bit mush these days. Motor start caps?
I didn't use peak voktage to calculate rms power. 50 Volts peak = 35.35 Vrms
35.35^2 / 8 = 156.2 Watts
It was in a pett post. Maybe you were being factious, maybe not, anyhow I'm game, so a few sizes of these get thrown in on Mouser orders https://mouser.com/ProductDetail/667-ECQ-E2565KF/
When buying input caps, many times I'll order 10+ to get Mouser's qty pricing and I wind up with several of these things. Wima MKS2 datasheet says 30vac, 50vdc, so that makes me confident these will be fine in this application.
Oh, well for low cost caps those Panasonic ones are perfectly decent. Give 'em a try in a crossover, you might be surprised.
@PWRRYD sorry, I didn't mean to presume, your wording threw me off.
So far the Wima have been the surprise. I like em' better the the ebay Audiophiler caps for sure. I'll use some of the Panny on this build going forward and see how they feel.
FWIW, I do not like the 'Audiophiler' brand caps.
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Wimas have always sounded good! They are made with a dual-layer unlike other metallized caps.
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Yeah, as the audiophilers are used up they will be replaced with wima except for the sizes wima doesn't have. And honestly, I may start using some of the cheap pannys once I get a feel for them. The wima MKP10 are the popular ones for crossovers but I'm finding the MKS4 and MKS2 sound good too.
I've only used the MKP10, to be honest.
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Here's the filter for taming the humps in the response. Surprisingly, it makes a larger difference when listening to them far-field, as normal stereo speakers, than up-close as computer monitors.
This look ok to you guys? Would you have changed something? The ~1.7k hump can be adjusted +/- with the resistor.