Capacitor value

nemohm
nemohm Posts: 19
in Speakers
Hello All,
I have a capacitor to identify. Could be 72pF, need confirmation, please.
It is the second capacitor in series with 3.3uF in the first order high pass speakers filter. I believe it is for phase correction. There is 10wR4 between capacitors
I'm looking to replace it with a better quality one, non-ceramic?
Thank you again,

ni2n1pmva6yn.jpg
· Share on FacebookShare on Twitter

Comments

  • Gardenstater
    Gardenstater Posts: 4,455
    It might not even be a capacitor. Could be a MOV or a polyswitch.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on FacebookShare on Twitter
  • nemohm
    nemohm Posts: 19
    edited April 2023
    Then better keep it untouched? Do they age?
    · Share on FacebookShare on Twitter
  • Gardenstater
    Gardenstater Posts: 4,455
    nemohm wrote: »
    Then better keep it untouched? Do they age?

    Those components I mentioned, which yours may or not be, definitely are known to deteriorate and even fail.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on FacebookShare on Twitter
  • F1nut
    F1nut Posts: 50,494
    edited April 2023
    nemohm wrote: »
    Hello All,
    I have a capacitor to identify. Could be 72pF, need confirmation, please.
    It is the second capacitor in series with 3.3uF in the first order high pass speakers filter. I believe it is for phase correction. There is 10wR4 between capacitors
    I'm looking to replace it with a better quality one, non-ceramic?
    Thank you again,

    ni2n1pmva6yn.jpg

    It is a 60V 0.75A Radial Lead Polyswitch, which is a thermal reset device. It acts as a fuse of sorts. Generally, the device will have a resistance of 0.5 ohms. If you remove it (highly recommended) you should replace it with a 0.5 ohm resistor of at least 5 watts, 10 is better.

    When asking for help like this state what speakers you have, so what speakers do you have?
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

    · Share on FacebookShare on Twitter
  • nemohm
    nemohm Posts: 19
    edited April 2023
    Hello, Thank you very much for your suggestions!
    After years of stale audio interests I decided to get back on the field. I have Denon AVR used for stereo only. Kef HTS3001SE that I'm not happy with. The room response is pretty much on the inferior side.
    This is how my saga started.I was able to get RTi150 for very optimistic price. The first (and last) hookup (2x80W) was devastating.
    The drivers were flapping, extremely muffled sound. Same outcome with mid/tweeter hookup only. Tweeters are blown. Not sure if the speakers came with blown tweeters (not tested at the point of sale) or were blown as a result of my AVR clipping. Or faulty crossover (s). Took the speakers apart and measured Re of drivers.
    Woofers are 1.3ohm each, serially connected; mids are measured 3.4ohm. No wonder the speakers are exceptionally power hungry ones. Sourcing tweeters or replace with 3rd party ones, can't figure it out. Fear to have a hookup again with new tweeters.
    Despite the fact the speakers are "8ohm compatible" according the manual.
    The part under question is from friend's DQ QX6A speakers.
    0.50hm 10w resistor is hard to source though, too many types, too many series of the same resistor.
    My best hit is Solen MOX 1ohm 10w, 2 in parallel. Hope this works.
    Much appreciated!

    (BTW, I found exactly the same component on AliExpress...)
    · Share on FacebookShare on Twitter
  • Gardenstater
    Gardenstater Posts: 4,455
    Have you measured the resistance of that suspected polyswitch? If it is a 0.5 Ohm one when it isn't shifted or blown, then here is a good replacement:

    https://www.soniccraft.com/product_info.php/050-ohm-vishay-mills-mra-12-p-5332?osCsid=sojbji2ue07n5ni2putf4skd70

    What exact component did you find on AliExpress? The polyswitch? Show us a link :)
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on FacebookShare on Twitter
  • nemohm
    nemohm Posts: 19
    There is the link here:
    https://fr.aliexpress.com/item/32929341401.html?gatewayAdapt=glo2fra

    Thx
    · Share on FacebookShare on Twitter
  • Gardenstater
    Gardenstater Posts: 4,455
    Maximum Post Trip Resistance = 600mOhm
    Minimum Untripped Resistance = 250mOhm
    Maximum Untripped Resistance = 400mOhm

    https://www.arrow.com/en/products/rxef075/littelfuse

    No specs here:

    https://www.aliexpress.us/item/2251832646848137.html

    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on FacebookShare on Twitter
  • nemohm
    nemohm Posts: 19
    It is typical for AliExpress to provide no details.
    There is pic from the measurement:wg8hu97cihl3.jpg

    The resistance fluctuates 00.2-00.4, initially could go to 6-7 briefly.
    · Share on FacebookShare on Twitter
  • nemohm
    nemohm Posts: 19
    edited April 2023
    The Polyswitch is available even in Canada
    https://www.digikey.ca/en/products/detail/littelfuse-inc/RXEF075/5015922

    Time for reaction is 6.3 sec --Is it not enough to fry the tweeter?

    A resistor of 0.5 ohm (or else) as replacement - would it be better or in disadvantage?
    Thx
    · Share on FacebookShare on Twitter
  • F1nut
    F1nut Posts: 50,494
    0.5 ohm 12 watt high quality resistor,
    https://www.soniccraft.com/product_info.php/050-ohm-vishay-mills-mra-12-p-5332?osCsid=8cgfg59j7n18rlfohrirs7n2l2
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

    · Share on FacebookShare on Twitter
  • Gardenstater
    Gardenstater Posts: 4,455
    edited April 2023
    nemohm wrote: »
    The Polyswitch is available even in Canada
    https://www.digikey.ca/en/products/detail/littelfuse-inc/RXEF075/5015922

    Time for reaction is 6.3 sec --Is it not enough to fry the tweeter?

    A resistor of 0.5 ohm (or else) as replacement - would it be better or in disadvantage?
    Thx

    I was shocked at that reaction time as well. It also said max. of 3.75 A (so even longer to trip at 1.5 A ?) The fast blow fuses for the Peerless tweeters in my 7Bs are 1 A.

    People who omit the Polyswitches have said they contribute to audible distortion, especially after they have tripped multiple times. I don't know which would sound better, an untripped polyswitch or a fuseblock with a fuse. My fuseblocks have ferromagnetic rivets that Polk used as the conductor. There are those such as Danny Ritchie who claim that any ferromagnetic materials in the conductor path can cause audible effects that are negative.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on FacebookShare on Twitter
  • nemohm
    nemohm Posts: 19
    -Omitting the switch in a whole is one option I'm considering.
    -Replacing the switch with resistor as suggested by F1nut. But will the resistor provide any protection?
    -Searching for switch with faster reaction..
    - Fuses - kind of cumbersome and seldomly used solution.
    Which way to go?
    Thx
    · Share on FacebookShare on Twitter
  • F1nut
    F1nut Posts: 50,494
    If you think you need a fuse or polyswitch you shouldn't be playing this game.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

    · Share on FacebookShare on Twitter
  • nemohm
    nemohm Posts: 19
    With all due respect, I'm confused - what is the game here?
    Could you please elaborate?
    I'm not sure of anything related to electricity. (my background is in mechanical engineering).
    Not sure if such switches are common and effective and if they do good or harm, nor what the resistor replacement does.
    I was surprised to find that component within a crossover, never seen one before in my very limited experience.
    Just looking for a piece of advice from knowledgeable people...
    · Share on FacebookShare on Twitter
  • F1nut
    F1nut Posts: 50,494
    Just replace the polyswitch with a resistor and be done with it.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

    · Share on FacebookShare on Twitter
  • pitdogg2
    pitdogg2 Posts: 25,412
    @maymarilyn reported
    · Share on FacebookShare on Twitter
  • skipshot12
    skipshot12 Posts: 1,157
    nemohm wrote: »
    With all due respect, I'm confused - what is the game here?
    Could you please elaborate?
    I'm not sure of anything related to electricity. (my background is in mechanical engineering).
    Not sure if such switches are common and effective and if they do good or harm, nor what the resistor replacement does.
    I was surprised to find that component within a crossover, never seen one before in my very limited experience.
    Just looking for a piece of advice from knowledgeable people...

    Not at all uncommon to find poly switches in a speaker’s crossover.
    What gives you the surprise to find them in a crossover?
    · Share on FacebookShare on Twitter
  • skipshot12
    skipshot12 Posts: 1,157
    As said above, measure the resistance of the switch and replace the switch with the same value resistor.
    If you’d like to play with the sound of your speaker you can also try different value resistors or jumper to remove it completely.
    One word of caution when jumpering/eliminating the switch… make sure you have plenty of clean power so your amp never goes into clipping. Bad stuff happens with under powered gear when the switch has been eliminated.
    If driving with a receiver it would be wise to not eliminate the poly switch.
    · Share on FacebookShare on Twitter
  • skrol
    skrol Posts: 3,372
    The problem with measuring the resistance of the polyswitch and replacing with a resistor of that value is that if they have ever tripped, they don't go back to the same resistance (usually higher). Best to find a spec sheet for the polyswitch and use the value for untripped. Or just replace it with a 0.5 ohm resistor as is commonly done for that polyswitch.
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.

    HT:
    Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601
    · Share on FacebookShare on Twitter