SDA Polyswitches Are Nasty

TennMan

jmitchnh wrote: »

Since it's in paralell I am assuming I do not need to jumper it?

This is the question I answered. Once again, the correct answer is yes the polyswitch does need a jumper for proper operation of the tweeter. I see nothing about completing a circuit in that question.

heiney9

TennMan wrote: »

This is the question I answered. Once again, the correct answer is yes the polyswitch does need a jumper for proper operation of the tweeter. I see nothing about completing a circuit in that question.

If it's in parallel to the cap then if you remove just the poly, the cap still completes the circuit, why add a hunk of wire to the cap? Now that's simply in practice as there is more going on here than simply removing the poly since the cap and poly work together for the protection circuit.

If I am wrong about how parallel and series circuits are configured please explain.

H9

FTGV

TennMan wrote: »

Once again, the correct answer is yes the polyswitch does need a jumper for proper operation of the tweeter.

Yes,and you can remove the cap(C4)if so desired since it will have no function.

DarqueKnight

heiney9 wrote: »

DK,

So the cap is part of the protection and not part of the contour circuit?

Yes, as specified in the schematic notes.

heiney9 wrote: »

Seems like a large hole in the contour would exist if you just take it out, since it's obviously in the signal path.

If that were true, then the previous model Monitor 12 would have a large hole in the contour since it has the identical HF circuit minus the polyswitch and 4.2 uF cap.

FTGV wrote: »

It appears in normal operation the polyswitch shorts the 4.2 uf cap( taking it out of the circuit).If the levels are high enough to trip (open) the poly switch then 4.2 uf becomes part of the hi pass network.This would allow the tweeter to still have some output but because C3 and C4 are now series connected( the combo resulting in just over 3 uf.) the high pass filter will be shifted to a higher frequency which would afford the tweeter more protection.

I agree. The higher the signal's frequency, the less power there is in the signal.

DarqueKnight

TennMan wrote: »

I think you will have to jumper it. When closed it is part of the circuit. If you simply removed it the tweeter would stop working as it does when the polyswitch trips.

TennMan wrote: »

This is the question I answered. Once again, the correct answer is yes the polyswitch does need a jumper for proper operation of the tweeter. I see nothing about completing a circuit in that question.

You answered incorrectly because you obviously assumed the polyswitch was in series with the tweeter, rather than being in a parallel combination with a capacitor. Your statement that the "tweeter would stop working as it does when the polyswitch trips" is not correct since the signal would still have a path to the tweeter through the 4.2 uF capacitor if the polyswitch were removed.

FTGV

DarqueKnight wrote: »

If that were true, then the previous model Monitor 12 would have a large hole in the contour since it has the identical HF circuit minus the polyswitch and 4.2 uF cap.

Correct ,however removing just the polyswitch as per H9's original suggestion would cause a large hole in the frequency response due to the high pass xover frequency being pushed much higher as a result of the series connection of C3 and C4.

quadzilla

musky1963 wrote: »

Quick hijack.....I just pulled the pr's from my 2.3tls. I want to get rid of the polyswitches and use jumpers. I do not see enough room to do so, as the legs on the mustard colored polys are not long enough and are very close to the board. Tight quarters, next to harness and a cap too. Do I have to remove the x-over and do it from the backside of the crossover?

Pretty much yes. But it's just a single hex bolt plus unclipping the harnesses to remove them. It's not a big deal.

heiney9

FTGV wrote: »

Correct ,however removing just the polyswitch as per H9's original suggestion would cause a large hole in the frequency response due to the high pass xover frequency being pushed much higher as a result of the series connection of C3 and C4.

So the poly has that much influence on the contour? I was always aware the poly had a very small influence on the sound. I've removed several and never heard a large hole in the frequency response.

H9

TennMan

heiney9 wrote: »

If it's in parallel to the cap then if you remove just the poly, the cap still completes the circuit, why add a hunk of wire to the cap? Now that's simply in practice as there is more going on here than simply removing the poly since the cap and poly work together for the protection circuit.

If I am wrong about how parallel and series circuits are configured please explain.

H9

I think you might be looking at this parallel circuit as if the polyswitch was functioning as a resistor when it is operating normally.

I'm not an electrical engineer but I will explain the reason for my answer.

If the polyswitch is not tripped, and is in new condition, is should ideally function as a straight piece of wire. Since electricity takes the path of least resistance the capacitor would effectively be bypassed.

Once the polyswitch trips due to overheating, it does provide resistance and works in parallel with the capacitor to attenuate the power going to the tweeter in order to protect it.

FTGV

heiney9 wrote: »

So the poly has that much influence on the contour? I was always aware the poly had a very small influence on the sound. I've removed several and never heard a large hole in the frequency response.

H9

Normally it wouldn't but with this model as tennman also points out because it has an additional paralleled cap that only gets introduced into the circuit when the poly switch is triggered (or removed entirely).

heiney9

I am not and EE either and I can certainly see your logic.

Fred and Raife are EE's so I'd certainly take anything they say more seriously.

H9

FTGV

heiney9 wrote: »

Fred ... EE .

H9

I wish but just a lowly ET.

heiney9

FTGV wrote: »

I wish but just a lowly ET.

I'm not even that

DarqueKnight

heiney9 wrote: »

I am not and EE either...

I'm not an EE either, I just stay at Holiday Inn Express a lot.:razz:

dudeinaroom

DarqueKnight wrote: »

...... I just stay at Holiday Inn Express a lot.:razz:

lol lol

jmitchnh

After reading numerous threads (beside this one) concerning removing polyswitches I went ahead and did the deed. I did install a solid core copper wire in it's place and the resistance of both switches registered at approx. .3 ohms. The result? Count me in is one who thinks this does make a significant improvement. The highs have more sparkle and air to them. More detail, more clarity. They sound a lot closer to the way my SDA-1Cs did and that is a very good thing. Next up, RDOs and Clarity Cap x-over rebuild.

audio_alan

+1 in the believer camp!

I need some more time listening to them (and probably more burn-in), but I'd say there is a definite hi-end clarity improvement without the Polys. I know for sure the Poly in my left speaker was junk.

FYI - I installed .5, 12 watt Mills. I also have some .22's that I might try after a month or so, just to see if I can tell the difference. It almost takes longer to remove all the faceplate screws on the SDA-SRS plate, and warm up the soldering iron, than it does to complete the mod! (It helped having a TV snack tray that was about the exact height I needed to support the xover and plate while I worked on it though...)

(A monster may have just been created! :cheesygrin: Spikes are next, already in hand.)

simm

I have a pair of 1C's that I haven't listened to much over the last year or two as they just didn't sound that good to me. I have been debating selling them since they were just taking up space. I decided yesterday to see how complicated it would be for me, who has ZERO experience with soldering and ZERO experience with electrical circuits to to remove the polyswitches just to see if I would hear something better. I popped the passive out, unbolted the crossover, identified the polyswitch and decided to go for it. I had no soldering iron so went to Radio Shack and bought the $10.00 beginner kit and made a jumper to run between the leads. The soldering work is not especially pretty but damn these speakers sound like they have a new life. I have been listening most of the afternoon and can't believe they are the same speakers. Anyone sitting on the fence because of lack of knowledge I strongly urge you to just go for it, it really is simple and takes no more than an hour start to finish.

StantonZ

I wish some of you guys had posted the (resistance) value of the polyswitches you removed. I just completed an XO mod on my Monitor 10's and replaced the PS's with a 0.5 Ohm resistor. The resistance value of the (removed) PS's ranged from .7 to 2.2 Ohms! Needless to say I'm thrilled with the results.

xschop

Just found this thread. I believe this is the reason my RD0194s sounded somewhat veiled on my CRS+
After long cap burn in, I am now clearly hearing some distortion in some synth and horn frequencies.
Since I previously installed 2.0 ohm Mills resistors in place of factory 2.7ohm, would it be ok to just replace the polyswitch with a 1.2ohm Mills resistor?

DarqueKnight

xschop wrote: »

Just found this thread. I believe this is the reason my RD0194s sounded somewhat veiled on my CRS+
After long cap burn in, I am now clearly hearing some distortion in some synth and horn frequencies.
Since I previously installed 2.0 ohm Mills resistors in place of factory 2.7ohm, would it be ok to just replace the polyswitch with a 1.2ohm Mills resistor?

The factory ceramic metallic resistors have a 10% tolerance, so a suitable replacement for the 2.7 ohm resistor would be in the range of 2.5 to 3 ohms.

The appropriate resistor for polyswitch replacement depends on the resistance of the polyswitch. The resistance values for various polyswitches, along with spec sheets and pictures, are provided at the beginning of this thread.

xschop

Pleasantly surprised. I pulled both and the right channel offender measures 1.6 ohm, the left channel measures 0.4 ohm.
MCI 500 is imprinted on both...
I replaced both with the Mills 1.2 ohm spares I had on hand... Dire Straits don't sound so dire now and we have a balance in the force.

K_M

We had 2 tweeters get fried, even WITH the polyswitch in place.

xschop

I concur, as with mine, the distortion was in 2-2.5khz range. The synths on "Walk of Life" were about to become the walk of death for the tweeters.
Where's F1, this mod is not official until I get his blessing hehe.

K_M

xschop wrote: »

I concur, as with mine, the distortion was in 2-2.5khz range. The synths on "Walk of Life" were about to become the walk of death for the tweeters.
Where's F1, this mod is not official until I get his blessing hehe.

Both of our tweeters were gone in an instant. We got new ones for free, installed them and it sounded good again.
Not sure how the Polyswitch did not save them, yet was still in good shape?

heiney9

K_M wrote: »

We had 2 tweeters get fried, even WITH the polyswitch in place.

Probably using a low power entry lever AVR, it'll do that every time if you push it.

DarqueKnight

K_M wrote: »

Not sure how the Polyswitch did not save them, yet was still in good shape?

Low powered amplifiers are more susceptible to "hard clipping" when driven too hard.

During clipping, the transient spikes of energy can sometimes occur too fast for the polyswitch to react, or be damaged by the energy spike.

It's the same principle as some people having been struck by lightning and weren't harmed. A large amount of electricity passed through their body, but it passed through their body so fast that there was no tissue heating.

K_M

heiney9 wrote: »

K_M wrote: »

We had 2 tweeters get fried, even WITH the polyswitch in place.

Probably using a low power entry lever AVR, it'll do that every time if you push it.

No, it was using a Fairly high powered amplifier actually.
250 watts per channel, but had a loose input connection to power amp that made a very loud snap sound when moved. Poof!

We never play stuff loud enough to clip. I listen at moderate volume levels always.

Why would you make the assumption it was with an AVR?

K_M

DarqueKnight wrote: »

K_M wrote: »

Not sure how the Polyswitch did not save them, yet was still in good shape?

Low powered amplifiers are more susceptible to "hard clipping" when driven too hard.

During clipping, the transient spikes of energy can sometimes occur too fast for the polyswitch to react, or be damaged by the energy spike.

It's the same principle as some people having been struck by lightning and weren't harmed. A large amount of electricity passed through their body, but it passed through their body so fast that there was no tissue heating.

Sorry, 2 wrong assumptions.

txcoastal1

Ouch,
we've all made similar mistakes...including myself
Please power your stuff down when moving gear and/or swapping cables