Time to Open the Wallet

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slbenz
slbenz Posts: 97
in Vintage Speakers
Been enjoying the Polk SDA 2B speakers for the last couple of months. Just last night, the right speaker started to fade in/out. Had an extra set of speakers to rule out my preamp and power amp, both of which are only a year or two old. Sure enough, it is the speaker. Looks like I will have to open the wallet and replace the crossover components. Since I already have the RDO-194 tweeters installed, will only do the standard component replacement. Time to get out the soldering iron.
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  • Schurkey
    Schurkey Posts: 2,100
    edited December 2015
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    Enjoy! It isn't difficult, and doesn't have to be expensive. Even "cheap" film caps are WAY better than ancient electrolytics.



    I gotta say, "fade in/out" isn't something I'd expect from the crossover. I suppose it depends on what exactly has gone wrong with the crossover. Keep an eye out for -anything- amiss inside the cabinet, including loose wires. Do you mean that the tweeter entirely and abruptly quits working for awhile--then abruptly comes "back to life"? That could be a failed polyswitch.
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  • slbenz
    slbenz Posts: 97
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    It doesn't seem to be just the tweeter but the overall sound reduces then comes back to full volume. Been using a different set of speakers and have not heard the same issue so it is not the power amp or preamp. I have ordered new components and hope will solve the problem.
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  • Conradicles
    Conradicles Posts: 6,036
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    Make sure your amp is "common ground" which I am sure you already know this.
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  • westmassguy
    westmassguy Posts: 6,850
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    Don't rule out your amp just yet. SDAs are not like conventional speakers. They present a more difficult load than your typical 2 or 3way speaker. Even in stock form, the 2Bs will drop below 4 ohms at certain frequencies. If the tweeter is fading in and out, it could be the Polyswitch. The Tweeters in all SDAs cover a very wide frequency range, and may give the impression that all frequencies are fading in and out.
    Home Theater/2 Channel:
    Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
    Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
    Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
    Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
    Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer

    dhsspeakerservice.com/
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  • slbenz
    slbenz Posts: 97
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    The amp that I am using is a common ground and does not exhibit this fading in/out of the sound when I use a different set of speakers. Been using the 2B for the last couple of months daily until now. If it is the polyswitch, I can bypass it correct? Or do I order a component to replace it? I did not think of doing anything to the polyswitch when I ordered at the time.
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  • slbenz
    slbenz Posts: 97
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    Decided this morning to take a look at the crossover and check and clean all the connections. Also applied damping material to the mid and passive drivers on both speakers. Been playing the SDAs off and on all day without experiencing the fading in/out issue with the right speaker. But the damping material did do what others said on this forum. It cleaned up the mids and lows while making the highs sound clearer without listener fatigue. Nice inexpensive upgrade. Just waiting for the new crossover components to arrive on Monday.
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  • slbenz
    slbenz Posts: 97
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    Installed the new components to both crossover networks. I would agree that there is an improvement. The sound stage is blacker, with greater detail and definition. Clarity improved with voice sounding very similar to my Magnepan IIIas. Highs are more extended with lows tighter sounding. One thing I failed to install was replacing the poly switches. I have a set of Mills resistors coming in the mail. I am assuming that replacing the poly switches will further increase the overall clarity and extension of the 2B's. The new components that I ordered already lifted the veil on these speakers and replacing the poly switches will further lift that veil, I am assuming. Rebuilding and modifying these speakers certainly is much easier than a Magnepan IIIa rebuild. :)
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  • RandyCroissant
    RandyCroissant Posts: 475
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    Those poly switches have been known to cause noise especially once they have been tripped. Replacing them with a jumper or a 0.5 ohm resistor is a recommended mod.
    Yamaha RXA1030, Yamaha CD-S2100, Yamaha AS-2200, Bluesound node 2i
    Polk SDA2btl highly modded
    Polk SDA 1C modded
    Polk CS350 LS x2
    Kimber 8TC
    Sony 55" Bravia
    Wish list SVS sub

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  • slbenz
    slbenz Posts: 97
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    RandyCroissant wrote: »
    Those poly switches have been known to cause noise especially once they have been tripped. Replacing them with a jumper or a 0.5 ohm resistor is a recommended mod.

    Randy, thanks for the information on the poly switches. Since I am one of those sensitive to high frequencies, going the 0.5 ohm resistor route is probably best for me. Time to get out that soldering iron again in a couple of days and take those speakers up another notch.
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  • slbenz
    slbenz Posts: 97
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    The Mills resistors arrived. Soldered them in and yes, I would agree that it removed another layer. Speakers again are clearer sounding, with even more detail. Seems the SDA affect is even wider with better positioning of instruments and voice in space. Great modification for cheap.
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  • RandyCroissant
    RandyCroissant Posts: 475
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    That was my experience as well. Just wait after some burn in time they get even better, funny thing electronical stuff
    Yamaha RXA1030, Yamaha CD-S2100, Yamaha AS-2200, Bluesound node 2i
    Polk SDA2btl highly modded
    Polk SDA 1C modded
    Polk CS350 LS x2
    Kimber 8TC
    Sony 55" Bravia
    Wish list SVS sub

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  • Mr_Hz
    Mr_Hz Posts: 176
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    Love your title to this thread. I don't have any technical input but will say, that since I joined this forum a ~year ago, I've been opening my wallet for this upgrade and that... and also expanding my SDA speaker collection. Money well spent in the pursuit of fine music reproduction! This from a guy who has had original SDA2's from the mid 80's and finally decided to upgrade his listener experience.
    2.3TL's - Living Room
    CRS+'s (4.1 TL's) - Office
    SDA1C's - Famdamly Rm
    SDA1C's - Master Bedroom
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  • Schurkey
    Schurkey Posts: 2,100
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    slbenz wrote: »
    The Mills resistors arrived. Soldered them in and yes, I would agree that it removed another layer. Speakers again are clearer sounding, with even more detail. Seems the SDA affect is even wider with better positioning of instruments and voice in space. Great modification for cheap.
    Do I understand this correctly? This last mod, you replaced just the polyswitches with Mills resistors, and the SDA effect is wider/better?

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  • slbenz
    slbenz Posts: 97
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    That is correct. Removing the poly switches got rid of another layer and provided another level of SDA experience. I think because of the reduced background noise as others have said doing this. It is able to flesh out more from the speakers.
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