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  1. #1

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    Default SDA Polyswitches Are Nasty

    Question:

    "Why was the polyswitch deleted from the SDA 3.1TL? It is the only SDA that does not have tweeter protection."

    Answers:

    "I don't know for sure. We were having some trouble at the time with inconsistency on the polyswitches and may have decided that it was simply not necessary due to the lower power handing of the 3.1 Ultimately we determined that the trip current of the polyswitch prior to being tripped the first time was significantly higher than its rating. As I recall we then began a program of pre-conditioning polyswitches by tripping them prior to installation."

    -Matthew Polk -Polk Audio Co-founder and SDA Inventor

    ________________________

    "People complained about the protection kicking in and out. They did not see it as a benefit. The damn thing cost $1+ way back then. We came to the conclusion that it was easier to design the speaker so that the tweeter did not fail unless/until it was painfully obvious that it was playing beyond its capability. In other words, while it is possible to overpower the speaker given the limitless choices of amplifiers, the speaker will sound really distorted long before it blows - garbled almost unintelligible. SO, the limit of the loudspeaker is the point on the volume knob at which it begins to sound distorted."

    - Stu Lumsden - Polk Audio VP of Engineering


    Historical Information

    The polyswitches Polk used in the SDA's and the current replacement polyswitches were made by the Raychem corporation. Doing a search on the part numbers lead me to Raychem's website (www.raychem.tycoelectronics.com) and to the websites of vendors who sell the parts. The old RDE series part numbers were superseded by and are now cross referenced to RUE and RXE series part numbers:

    Part number RDE090A was replaced with part number RUE090.

    Part number RDE050A was replaced with part number RXE050.

    Part number RDE070A was replaced with part number RXE075.

    The current polyswitches that are provided by Polk to replace the RDE parts are Raychem part number RXE135.

    The RXE135, RXE075, and RXE050 are obsolete, but are still available from parts vendors. They are even sold on eBay. The RUE090 is still in production, but it is being phased out by Raychem.

    Data sheets for the RUE090 and RXE series polyswitches are attached below.

    The RXE050 (RDE050A) has a resistance range of 0.50 to 0.77 ohm, with a post trip resistance 1.17 ohm.

    The RUE090 (RDE090A) has a resistance range of 0.07 to 0.12 ohm, with a post trip resistance 0.22 ohm.

    The RUE090 (RDE090A) has a resistance range of 0.25 to 0.40 ohm, with a post trip resistance 0.60 ohm.

    The current replacement polyswitch, the RXE135, has a resistance range of 0.12 to 0.19 ohm, with a post trip resistance 0.30 ohm.

    I have four unused RXE135's. Their measured resistances were 0.16, 0.16, 0.17, and 017 ohm. I saw that the schematics for the SDA 1C, SDA SRS 2.3TL, and SDA SRS 1.2TL specify the RXE135 polyswitch. However, the polyswitches removed from my SDA 1C's were RDE050A's. I still have one of the polyswitches taken from my 1C's. It measured 0.85 ohm. While this is not a post trip level of resistance, it is well out of spec.

    I also have five of the RDE090A polyswitches which came out of my three pairs of 1989 model SDA CRS+'s (I seem to have lost lost, misplaced, or mistakenly thrown away the other polyswitch. The 1989 SDA CRS+ uses the same crossover as the 1989 SDA 2B, yet the 1989 CRS+ schematic specifies the RDE050A and the 1989 2B schematic specifies the RDE090A. Maybe Polk neglected to update the 1989 CRS+ schematic.

    The measured values of the resistances for the RDE090A's taken from my CRS+'s were 0.29, 0.22. 0.23, 0.21, 0.23, and 0.42 ohm. These values are in the range for an RDE090A that has been tripped.

    While the attenuation properties of the polyswitch are relatively insignificant, the noise characteristics of the devices are considerable and audible...even when they are brand new. After a polyswitch is tripped the first time, the resistance increases from 52% to 83%. The noise from the "burned" polyswitches also greatly increases. [Quantifying the signal damage done by new and tripped polyswitches would be a good project for an interested meter pontiff.]:) Removing the polyswitches removes a tiny bit of attenuation, but removes a significant amount of noise. When noise is lowered, the signal becomes apparently louder although the amplitude (level) of the signal remains the same. It is analogous to cleaning a dirty window.

    Life Without Polyswitches

    I have been polyswitch free since 1990. When I consulted with Polk prior to doing my first SDA modification, I was advised that there would be an improvement in high frequency sound quality if the polyswitches were removed, but I was also advised to remove or short the polyswitches if and only if I was using quality amplification and if I was not in the habit of overdriving my amplifier.

    With the polyswitches out, I heard a more natural high frequency presentation, but it was not forward or bright. It was as if a veil had been lifted off the high frequencies.


    Three-fourths of the Foul Four (top to bottom): RXE135, RDE050A, RDE090A.

    ______________________________

    References:

    Change in Resistance with Polyswitch Removal

    I Removed My Polyswitches
    Attached Files
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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    "Knowledge, without understanding, is a path to failure."~DK

  2. #2

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    I knew there was a good reason to leave them out when I rebuilt my 1C crossovers. :D

    Nice research Raife. You always seem to objectify what most of us knew in the back of our heads.

  3. #3

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    I bought a pair of the original SDA2's that tripped way too easy. After a few trips the SQ dropped dramatically. I have a hard time recommending there removal to people I don't know for this reason
    ...I was also advised to remove or short the polyswitches if and only if I was using quality amplification and if I was not in the habit of overdriving my amplifier.
    I have been deleting them from my work, and giving caution.
    Thanks
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben

  4. #4

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    guys,, what are you using as a "jumper" in place of the polyswitch?
    JC approves....he told me so. (F-1 nut)

  5. #5

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    Default

    20 gauge solid core copper hook up wire.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
    __________________
    "Knowledge, without understanding, is a path to failure."~DK

  6. #6

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    Default

    Quote Originally Posted by DarqueKnight View Post
    20 gauge solid core copper hook up wire.
    +1. Just a small arc of solid core 16.
    Sony 60'' SXRD 1080p
    Amp = Carver AV-705THX 5-Channel
    Processor = NAD T747
    Panasonic BD35 Blu-Ray
    Main = SDA-1C Studio with RD0s, spikes, XO rebuild, rings, I/C upgrade
    Center=Polk CS10, Surround = Athena Dipoles, Sub= Boston 12HO
    Music/Video Streaming = Netgear NEO550
    TT = Audio Technica

  7. #7

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    Quote Originally Posted by george daniel View Post
    guys,, what are you using as a "jumper" in place of the polyswitch?
    Depends. If I can place the cap lead to the line side of where the Polyswitch was I do that, but if the board needs a jumper in place I just use a piece of 20ga or better solid.
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben

  8. #8

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    Question Polybitches

    Does anyone have a before and after picture of the switches in place and then the jumper cable in their places.....so visual learners like me can get the picture?

    -Luc
    "I'm sure it's better than it sounds."

    Mark Twains' response, when asked what he
    thought of Wagners music.

  9. #9

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    Default

    You could also use a scrap cap/resistor lead if you're in a pinch.
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche

  10. #10

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    Default

    I have one with the jumper in. Jesse and I just used a clipped lead from a cap.

    Look at the S location I believe.
    Attached Images  

  11. #11

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    I'm assuming this would also hold true for speakers which are not from the SDA line, but still have poly's for the tweeter protection, such as my brothers Monitor 10 Series II speakers.
    Ludicrous gibs!

  12. #12

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    Yes and No,

    I took some out of my RTA 11T's a couple of weeks ago and they sound better. I looked at my RTA 8TL's and they did not have any poly switches and they still sound the same:D

  13. #13

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    Default

    Nice and concise as usual Raife :).

    I'm going to take this off on a slight tangent to get your views and others as well. I have a pair of 5B's which have Solens and Mills but they are fused. Do the same types of issues apply to fused protected speakers?

    What is the best way to eliminate the external fuse? Simply solder a thick piece of wire across the holder or is it better to place the jumper inside on the PC board?

    Any thoughts appreciated.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  14. #14

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    I knew I liked my 3.1TL for some reason. :)

    engtaz
    engtaz

    I love how music can brighten up a bad day.

  15. #15

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    Do it on the board.
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben

  16. #16
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    I usually just use a clipped piece of lead since it's what I have available. I figure if it's good enough for the Sonicaps I'm using, it's probably good enough for a jumper.

  17. #17

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    I originally installed new polyswitches when I upgraded my XOs, but shortly afterwards I removed them. The switch fed the C2 12uf cap and the C4 750pf bypass cap. Since I had already removed the C4 bypass cap, I took the lead from the C2 12uf cap and connected it directly to the input lead S1 where the switch was. Figured why have the extra connection through the jumper wire.

    The new 135 polyswitches measured .2ohm each.
    Last edited by tugboat; 10-28-2008 at 07:11 PM.
    Driver carries only 20 dollars in ammunition

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  18. #18

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    I'm going to jumper the polyswitches from my SDA2's but before I do I wanna make sure these are indeed the polyswitches. If they are it looks like the lead wires are long enough to join together and solder. There is a poly on the stereo crossover and 1 on the dimensional crossover. Is this correct?
    Mike
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  19. #19

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    Quote Originally Posted by michaeljhsda2 View Post
    I'm going to jumper the polyswitches from my SDA2's but before I do I wanna make sure these are indeed the polyswitches. If they are it looks like the lead wires are long enough to join together and solder. There is a poly on the stereo crossover and 1 on the dimensional crossover. Is this correct?
    Mike
    That little blue thing is it;) If your 2's have the side by side tweeters then yes you will have two per channel.
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben

  20. #20

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    Quote Originally Posted by ben62670 View Post
    That little blue thing is it;) If your 2's have the side by side tweeters then yes you will have two per channel.
    Ben
    Yes, they do have the side by side tweeters. Thanks for the confirmation Ben.

    Mike

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    Quote Originally Posted by ben62670 View Post
    That little blue thing is it;) If your 2's have the side by side tweeters then yes you will have two per channel.
    Ben
    Success! The leads were indeed long enough so it was just a matter of soldering them together. 22 years later and I'm polyswitch free.

    Thanks again Ben.

    Mike.

  22. #22

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    Mike, now that you are "free".....was it worth it? What do your ears tell you? I upgraded the tweeters on my 2b's and may take out the switches too I guess.

  23. #23

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    Mike-

    Do you have an "after" picture you could post?

    -Luc

    Quote Originally Posted by michaeljhsda2 View Post
    I'm going to jumper the polyswitches from my SDA2's but before I do I wanna make sure these are indeed the polyswitches. If they are it looks like the lead wires are long enough to join together and solder. There is a poly on the stereo crossover and 1 on the dimensional crossover. Is this correct?
    Mike
    "I'm sure it's better than it sounds."

    Mark Twains' response, when asked what he
    thought of Wagners music.

  24. #24

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    Quote Originally Posted by muncybob View Post
    Mike, now that you are "free".....was it worth it? What do your ears tell you? I upgraded the tweeters on my 2b's and may take out the switches too I guess.
    Luc,
    It was definitely worth it. I just soldered the leads together and ....wow, they sound alot better. I highly recommend it so long as you provide adequate amplification and don't get carried away with the volume control.
    Mike
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    Thanks Mike!

    Quote Originally Posted by michaeljhsda2 View Post
    Luc,
    It was definitely worth it. I just soldered the leads together and ....wow, they sound alot better. I highly recommend it so long as you provide adequate amplification and don't get carried away with the volume control.
    Mike
    "I'm sure it's better than it sounds."

    Mark Twains' response, when asked what he
    thought of Wagners music.

  26. #26

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    Quote Originally Posted by trubluluc View Post
    Thanks Mike!
    You're welcome Luc.
    Mike

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    I have cranked 450wpc through polyswitch-less SDAs without a problem. As long as you don't underpower and clip your speakers a bunch, you won't have a problem.

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    Closeup of the little buggers.
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    This is a great tweak...mine must have been in really bad shape. The difference is night and day. Seriously.

    All of you who still have polyswitches, get them out of there.

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    I agree that the poly's should go. After removal I noticed an increased energy in the highs that at first sounded good, but as time went on I realized this made the highs too bright for my ears. I then replaced the jumper with a .5 ohm, 12 watt resistor. Ah, much better.
    'Political Correctness'.........defined

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