SDA-2 Tweeter (Dimensional H.F.'s)

[ISLANDREAMER]

I noticed that the outer tweeter (Dimensional H.F. units) on each baffle of my SDA-2 does not emit any sound but when removed and tested on the inner tweeters (Stereo H.F. units), it does make a sound. My manual mentions of 2 fuses, one for dimensional and one for the stereo H.F. units near the speaker connection terminals but I don't see any "fast-blo" fuses on these speakers. Any advice is highly appreciated.

[F1nut]

Welcome to the forum.

You will find either the fuses or polyswitches, depending on the version of your SDA 2's on the crossover board. Remove the passive radiators from the front of each speaker to get access to the crossover.

[ISLANDREAMER]

I took off the passive radiator and there are 2 crossovers. The crossover (top) not directly connected to the speaker terminals has a roll of copper wire behind it. Will these fuse look like a regular fuse with glass in the middle and metal caps on the end? I am clueless on what a polyswitch would look like. I certainly appreciate the assistance F1.

[ISLANDREAMER]

This is a thread from my last email. I need help in locating the fuse or polyswitch. Thanks.

[F1nut]

I don't see any regular fuses in there and I'm only quessing about this one, but it looks like the polyswitch is the small blue device on the top crossover near the lower right hand edge.

Since I'm not all that familiar with your speakers, I've forwarded this thread to Ken Swauger at Polk with the hope that he'll be able to help you further.

[DarqueKnight]

As F1nut guessed, the poly switch is the small blue disk-shaped two-pin device on each of the circuit boards.

Sometimes these switches will go bad due to age and/or electrical stress. Polk will provide an improved replacement part free of charge. Even though the other polyswitch is still working, I would go ahead and replace it.

Contact Ken Swauger at polkcs@polkaudio.com.

Prior to the polyswitches, glass fuses were used in earlier SDA models. These fuses were located on the binding post plate. Back when these speakers were made, Polk would insert a correction sheet into the old manuals until they were all used up rather that print a new manual with the correction.

[F1nut]

Thanks for chiming in Raife, I owe you a email. :)

[ISLANDREAMER]

Thanks for the tip DarqueKnight and F1Nut. I also emailed Ken Swauger at Polk and see if I have to mail out the crossovers or will I get the polyswitches and install them myself.:)

[DarqueKnight]

If you can use a soldering iron or if you have a friend who can use a soldering iron, it is a very simple procedure. It is not necessary to send the crossovers back to Polk.

[ISLANDREAMER]

I have a soldering kit and I can do this myself. Just in case Polk can not mail me the switches asap, do you have any recommended speaker parts online stores? I've checked out Parts Express and they have a few made by Raychem with different ratings at $1.35 a piece.

[DarqueKnight]

Polk is usually quick about getting parts out. I would expect that the polyswitches would be shipped within a couple days of placing the order, unless they are out of stock. If they are currently out of stock, you might ask if there is an equivalent part available from another parts supplier.

[trixie_tracer]

If my memory serves correctly, the poly switch was used to shut the whole crossover down to prevent overheating. Does the tweeter emit no sound? The SDA was designed to eliminate "crossover" from right channel to left, thus giving true "stereo" sound. I belive the second tweeter you mention is the one that gives this effect to the listener. I could be wrong, it's been over 15 years since I worked on them.

[ISLANDREAMER]

I decided to do a continuity test with my multi-tester on these polyswitches with the speakers powered up. What puzzled me is that all four polyswitches indicated continuity. I was expecting that two of the four will show no continuity. What's even more puzzling is that one of the outer (Dimensional H.F.) tweeter is now sounding but the other outer tweeter is still mute. Did that polyswitch for that tweeter reset (if possible)? Did I do the right check on these polyswitches?

[trixie_tracer]

Poly switch is triggered by heat. It is a short when measured at room temp, when heated up the poly switch "opens" like a fuse. When poly switch cools, it will go back to 0 ohms. Pretty cleaver, eh?

[F1nut]

The polyswitch shuts down the tweeters, not the mid-drivers. My advice is to replacement all of them.

[dorokusai]

Originally posted by trixie_tracer
If my memory serves correctly, the poly switch was used to shut the whole crossover down to prevent overheating. Does the tweeter emit no sound? The SDA was designed to eliminate "crossover" from right channel to left, thus giving true "stereo" sound. I belive the second tweeter you mention is the one that gives this effect to the listener. I could be wrong, it's been over 15 years since I worked on them.

Crosstalk...not Crossover :)