Sda srs poly switch
Answers
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WHICH resistance? The resistance when new? The resistance after Polk popped 'em once? Or the resistance after the consumer popped 'em repeatedly, and the contacts got progressively more burned?
When it was MY speakers, the polyswitch was removed and no compensating resistor was installed. And overall, I'd prefer the treble to be a bit louder. -
The pre-trip resistance, of course.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 -
I think Polk did some sort of preconditioning of the Polyswitches before installing them. Overall the way they work is there's a temperature sensitive compound that has carbon particles imbedded in it. The material is electrically conductive at normal temperatures. As higher amounts of current flow through it the temperatures increase until the carbon particles become separated and it loses conductivity. Then it cools down and the particles come together and conduction returns. Kind of like gluing two wires to the surface of a balloon. Then hook the wires to an electric pump which slowly inflates the balloon until the wires separate and the pump shuts off and the balloon starts to deflate until the wires can touch.
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Absolutely, the resistance of the polyswitch was factored in.
Another vintage Polk non sequitur, as they were factored in to the wonderful SL2000 equation.Don't take experimental gene therapies from known eugenicists. -
I checked with Stu Lumsden, Polk's retired head of engineering, and he said:
"Yes, we did trip each Polyswitch PTC device to make sure it would meet our requirements. When new each device would trip at a higher level than the specification, but then after "burn in" it functions correctly. We found that after they sit for a while, say 6 months, they revert back to the higher threshold. I'm not sure how the newer versions of theses devices react." -
It does make sense that the resistance must have been considered as it would have been easy to protect the tweeters with little or no resistance. For the srs with SL2000’s it was good to tame them a bit as I always thought the SL2000’s that came new sounded way too hard. With the 0194’s I really think it sounds nice with the PS out. Depends on amp and source too. I wonder what those with 0198 tweeters do? Those I spoke to about crossover builds seem to go with .5 ohm non inductive resistors. I will reassess when I finish the crossovers.
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I'm seeing two different things that seem to be getting confused. Specifically, voltage required to trip the polyswitch vs. the resistance of the polyswitch before/after tripping.
1. Yes, Polk at some point was deliberately tripping the polyswitch as part of crossover assembly. I don't know if they did that from the beginning, or if it was adopted some time after polyswitches were being used.
2. The voltage needed to trip the polyswitch decreases as they're "exercised". I understood that the first trip took more voltage than the second, third, etc. I did not know that the polyswitch "healed" after "say six months" the voltage went back to the higher value. My understanding is (was?) that the more they're tripped, the easier it is to trip them--lower voltage required.
3. Aside from the voltage level needed to trip a polyswitch, the resistance of the polyswitch increases every time they're tripped. The contacts progressively deteriorate (burn) and thus the resistance progressively increases.
So it doesn't make a huge amount of sense to "factor in" the resistance of the polyswitch when the resistance is a changing value. The best they can hope for is that the polyswitch is never activated "in the field" and thus remains at a stable resistance from a single tripping...but if the polyswitch is never tripped in the field, why have the thing in the first place?
Logically, if the thing is needed--it's resistance is a moving target. If it's not needed, the polyswitch is a waste of time, money, effort, and enthusiasm.
The polyswitch is a cynical response to ignorant and/or careless consumers. I absolutely understand why Polk would include tweeter protection. I would too--who wants to pay the warranty costs for all the tweeter replacements? Especially when a protective device is so easy to obtain and include in the circuit at an extremely low cost AND doesn't require consumer replacement (unlike a fuse) and can't be easily defeated (like installing aluminum foil over a fuse, or installing a higher-value fuse.) MOST consumers wouldn't remove the crossover, identify the polyswitch, and wrap the legs together to take it out of the circuit.
Therefore, my position is that the polyswitches need to be removed--and that's not an unusual attitude around here. Where my opinion differs is in the compensation needed when the polyswitch comes out of the circuit. And that's likely going to vary based on the actual speaker model, listening habits, musical taste, hearing acuity, room acoustics, and probably other factors I can't think of right now. Point is, LISTEN to the treble and assess if it's loud enough.
The Polk speakers I'm familiar with (SDA 1B, SDA SRS 2 pin-blade) do not have enough treble for me. Not only do I want the resistance of the polyswitch removed, I want lower-value tuning resistors in the treble circuit.
Be very careful when someone says the polyswitch needs to be compensated with some value of resistor. -
A study of vintage Polk schematics clearly shows that Polk changed the values of some resistors when they went from using a fuse to using a polyswitch. Therefore, the polyswitch has a definite resistance value that was accounted for in the crossover circuit.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 -
2nd Shurkey.
Exactty -
Polyswitches are for b*tches.Don't take experimental gene therapies from known eugenicists.
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Be very careful when someone says the polyswitch needs to be compensated with some value of resistor.
Of course you can remove the polyswitch and just install a jumper. You only need to compensate for the polyswitch with a resistor if you want the speakers to sound the way Polk intended them to sound. I know the 0.5ohm resistor always comes up as the value to use, but are there schematics out there that back it up?
Post edited by joebass3 on -
Of course you can remove the polyswitch and just install a jumper. You only need to compensate for the polyswitch with a resistor if you want the speakers to sound the way Polk intended them to sound. I know the 0.5ohm resistor always comes up as the value to use, but are there schematics out there that back it up?
The real questions are "do you want the speakers to sound the way Polk intended", or do you want the speakers to sound RIGHT?Gardenstater wrote: »Going by the "090" wouldn't the pre-trip resistance be around 0.25 Ohms (0.31max/0.20min) ?
https://www.tme.eu/Document/3224e893b8d3a8cb339f75bf0e3d390f/Littelfuse_PTC_Radial_Leaded_RXEF.pdf
For me, in my rooms, with my ears and music...MORE TREBLE, please. Which means less resistance in the treble circuit.
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Don’t forget. We hAve all moved to a very different speaker with 0194’s crossovers, sda inductor…
No PS for me. We all have waaaay better power now as well.
XS chop hits it again.
Cheers! -
Anything less than a .5 ohm resistor is way too much treble for me, but then again, I'm not deaf.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 -
After I finish the crossovers I will most likely start with no ps and if it is too much I will try some resistors to get it good. I also have a very very smooth sounding tube like amp. Makes a big difference for me. I’ll have to confess as well that my ears have aged over the years. Try one of those youtube hearing tests and see where your eats quit. Mine now quit ant about 15-16k. But I’m hyper sensitive to mid highs now. But I can say the setup I have now which is RME ADI dac to Threshold S550e power amp is smooth as silk with ZERO ear fatigue. To each his own. Cool that we can fine tune it though I say.
Cheers
Go VGK! -
The real questions are "do you want the speakers to sound the way Polk intended", or do you want the speakers to sound RIGHT?
For me, in my rooms, with my ears and music...MORE TREBLE, please. Which means less resistance in the treble circuit.
That makes sense. Jumping the polyswitch or using a resistor to get the sound you're after. Making these speakers sound the way we like is the reason we do all these upgrades in the first place. -
A lot of what’s said above for me.
Maybe it’s the gen 3 blade/blade sda SRS’s, I found them to be a tad too mellow for me.
I also feel it depends on the quality of watts you’re feeding them.
However, after I finish the crossovers I’ll be re-evaluating how they sound. After that… -
The SDA SRS has a laid back, kind of thick sound characteristic.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
