Overkill filtering capacitors for active subwoofer. Bad or good idea?  - Page 1
Forum section: electronics / projects

author: Finderbinder
author_rank: Regular Contributor
timestamp: May 13, 2023, 08:24:29 pm
content: Originally subwoofer (250W) came with 2 x 10000uF x 50V general (no name?) capacitors of size: 30x50mm. One of them was blew so replacement needed. I see it is hard to find something branded to fit 30mm diameter and maybe at higher voltage. So plan B is to replace them with any reasonable caps do not taking into account dimensions (would wire them somehow instead of soldering). Now there are a lot of possibilities, but...May it affect other parts negatively if:1) capacity will be too high? How much is not too much/enough?2) ESR will be too low? How low is not too low/enough?Maybe these (size is overkill, age too, but..., and price is ok)?https://www.stockclear.nl/a-75175029/elco-s/philips-vishay-elco-15000uf-63v-30a-groot-model/#descriptionor these?https://www.stockclear.nl/a-64948753/elco-s/sprague-powerlytic-36de233g100de2b-23000-100dc-elco/#descriptionor something else?Or all this upgrade tends to be worthless?

author: bdunham7
author_rank: Super Contributor
timestamp: May 13, 2023, 09:26:48 pm
content: Having a bit more capacity or voltage is OK, but probably pointless TBH. ESR is not critical for this application. Those screw-type monsters would be a silly hack as well, IMO. You haven't stated the lead type and spacing, but capacitors with the same specs as the original or a bit bigger are readily available at the same 30 x 50mm dimensions. I don't know what is readily available to you, but European suppliers should have a similar lineup as what I see.Heres one that is 15,000µF @ 50V, 3000hr @ 105C.https://www.mouser.com/ProductDetail/Rubycon/50MXG15000MEFCSN30X50?qs=T3oQrply3y%2FhjqWDFl1AEg%3D%3DAnd one that is 12,000uF @63V, 3000hr @ 85C and a larger 6.2A ripple current.https://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/SLPX123M063E9P3?qs=5mhQgkvyHZA8r7RI2ghylA%3D%3D

author: Finderbinder
author_rank: Regular Contributor
timestamp: May 13, 2023, 09:46:32 pm
content: Lead type is snap-in, spacing 10mm.Actually height will fit 70mm freely.

author: CaptDon
author_rank: Super Contributor
timestamp: May 13, 2023, 11:25:39 pm
content: If it has a 60hz power transformer with full wave rectifier then E.S.R. is a factor since the unit is probably driving a 4 ohm or less subwoofer speaker. Marginal units tend to have 10,000uf on the plus and minus rails, higher quality units seem to have more like 20,000uf on each rail and tend to cause any lights on the same A.C. circuit to briefly dim when you first power up the subwoofer unit. With higher frequency SMPS power supplies the caps tend to be critically small, around 1000uf to 1200uf. I have a piece of shit Bash 500S 'plate amplifier' for subwoofer use that has a SMPS power supply and a SINGLE 470uf@200vdc cap sitting across the rails from plus to minus!!! What a joke!! 500watts?Maybe for the brief instant the FET's short out and dump the full capacitor right across the speaker! I have a much heavier Dayton Audio 250 watt unit with a linear 60hz power supply and BIG filter capacitors. It dims the lights on power up! It needed extensive upgrades to higher wattage 15 volt zener diodes to regulate the 15 volt rails and also the dropping resistors were severely under sized. After the upgrades the Dayton sounds far better than the Bash ever did and seems to have much more 'clean' headroom before clipping!! Best wishes!!

author: Zero999
author_rank: Super Contributor
timestamp: May 14, 2023, 01:24:10 pm
content: The main issue with over sizing the capacitor is the fuse blowing, during power on.

author: strawberry
author_rank: Super Contributor
timestamp: May 14, 2023, 02:47:31 pm
content: 45V / 4= 11.25Apk 1Vripple / 11.25Apk = 0.088capacitor ESRmaxlooks like general 100Wrms amplifier ( including ripple and voltage sag ~80Wrms)fc = 1/(2*PI*4*0.01F*2) = 2Hzvoltage drop due-to charge ~10V/10ms@10mF transformer not included due-to relative high ESR (0.9..0.1)