Problem with SDA 1C's

phxrider

I have a pair of SDA 1C's with a problem - when I first play them, they sound great, then shortly after, a terrible distortion kicks in. I don't really want to pay to ship them to Polk so I am looking for advice on what (and how) to check/replace.

I have never troubleshot anything like this before so basically I'm clueless as to where to begin...

fbm211

More info needed.Is your amp(s) common ground? Do you have another set of speakers to see if they work OK.

phxrider

Not sure... It's a Carver TFM25. I have a set of RTi 150's and they work fine with it, although I don't like their sound as much as the SDA's!

Marty913

Distortion? One speaker or both, can you pinpoint it to a driver (tweeter or mid-bass) or is it all drivers. When you say they were OK but shortly thereafter then sound bad, what does "shortly" mean (minutes, days, weeks?).

Hang in there. There's a lot of experts on here that will help.

fbm211

Try them without the interconnect cable connected and see if you still get the distortion.If you dont get any distortion then your amp isnt common ground.I had that problem but found out about it before I recieved my SDAs.Another member will probably chime in and know more about that amp.You MIGHT be able to tie the neg speaker terminals together to get a common ground.

phxrider

Sorry, I should have mentioned that they (and the 2B's I had before them) worked for years without any issues so I'm assuming the amp IS common ground. The TFM-25 makes plenty of clean power and the speakers were often played at max volumes (as in clean max, not knob turned all the way up). I'm almost certain whatever is wrong with them is from lots of loud playing.

They've been in the boxes for a few years now since this happened, but I seem to remember not being able to pinpoint the driver, but I'd say it was more from the mids. It's the left speaker. Do the crossovers/electrical parts in these tend to go first, or the drivers? I haven't tried them without the cable, maybe that will help pinpoint a driver...

jon s

sounds like a crossover problem... how long does it take before the distortion starts? If the driver is bad, the sound would be distorted from the beginning.

ben62670

If it is a tweeter distorting it could be the Poly switches. We really need more info, or we are just guessing.
Ben

treitz3

Have you switched the speaker cables and interconnects? If so, does the distortion follow?

BSUfbfan

I agree with Ben, if the distortion is in the tweeter of one speaker, then you probably have a bad poly switch on the crossover. You can remove the polyswitch and install a jumper, but then you need to watch the volume level and avoid distortion.

phxrider

I was thinking it was something in the electrical parts as well (crossover was my guess), since it only starts after a few minutes or when the volume is turned up past a certain point (which unfortunately isn't very much - far below the tweeter shutoff threshold), then it will distort until it's been turned off for a while (and whatever the offending part is cools down, I'm assuming).

Is it difficult to replace the polyswitch with a jumper or new one? I certainly don't mind using a jumper to diagnose it but probably would not want to run it indefinitely that way...

BSUfbfan

phxrider wrote: »

Is it difficult to replace the polyswitch with a jumper or new one? I certainly don't mind using a jumper to diagnose it but probably would not want to run it indefinitely that way...

It depends on the listener. Several on the forum have replaced polyswitches with jumpers and have great success. You just have to know the distortion threshold and don't cross it. I listen pretty damn loud, but i'm running some serious clean wattage.

If you are worried, then you can get replacement polyswitches from Polk Parts.

candyliquor35m

Clip the polyswitch leads off about 1/4" (or long enough for them to touch each other) from the x-over board and then bend them together until they are touching and then solder them together.

Don't turn your volume past 12 o'clock or past halfway from where it starts and ends.

ben62670

phxrider wrote: »

Is it difficult to replace the polyswitch with a jumper or new one? I certainly don't mind using a jumper to diagnose it but probably would not want to run it indefinitely that way...

Can you solder?
If you can its easy. Many use jumpers. It really depends on your self control. If you hear any distortion back off. Poly switches are not 100% either. Transient spikes can kill too.

Ben

phxrider

Yeah, I think that's what happened to the polyswitch (or whatever this eventually turns out to be) in the first place! :-P The speakers were in the custody of an ex girlfriend who likes to really rock out while vacuuming and I think she was less anal than I am about distortion. Anyway, my self control is pretty good - others' I worry about sometimes.

I can solder fine, if I can identify the polyswitches. They always kicked in when there was no distortion, maybe I'll be better off without them anyway?

The TFM-25 puts out a ****load of clean power so I'm usually more worried about genuine overdriving than clipping the amp. Nothing makes me cringe like the sound of my woofers making a crackling sound!

treitz3

So I take it you have determined that it is a woofer and not a tweeter?

F1nut

If the poly is bad, you won't get any sound from the tweeters. Since you say it's distortion you're hearing shortly after things warm up, it very well could be that a cap has gone south.

phxrider

As I said, they have been in boxes for a few years since this happened so my memory is a little fuzzy on it, but I recall that I was not able to tell exactly where it was coming from... I remember thinking the sound was in the woofer/mids.

What F1nut said is exactly what I thought... If this is the case, does that mean we're talking about a new crossover? If so, is it worth the cost?

jakelm

phxrider wrote: »

As I said, they have been in boxes for a few years since this happened so my memory is a little fuzzy on it, but I recall that I was not able to tell exactly where it was coming from... I remember thinking the sound was in the woofer/mids.

So your not listening to them right now??? At least listen to them , then come back to us with what you hear.

F1nut

phxrider wrote: »

What F1nut said is exactly what I thought... If this is the case, does that mean we're talking about a new crossover? If so, is it worth the cost?

You can't buy new ones, you have to rebuild the originals.

I take it you have limited knowledge about this stuff, so before you do anything else you're going to have to pin point the problem. Hook them back up to make sure the problem is only with the one speaker. If that is the case, swap parts starting with the crossovers.

If you'd like some help, state where you live as there might be a Polkie close by that could guide you in person.

jakelm

jakelm wrote: »

So your not listening to them right now??? At least listen to them , then come back to us with what you hear.

And I want to appologize, I didnt mean to come out to abbrasive. But you really need to hook them back up and take another listen, so we can determin wether its the drivers or xover ot both.

phxrider

No offense taken... I do need to get them out and do some more playing with them. I think trying without the crossover cable would possibly help isolate the distortion better. I did not do this originally.

I'm in the Phoenix area, Chandler to be exact. But I really should get them out of the boxes and ready before asking someone to spend their time helping me rip them open and troubleshoot.

treitz3

My advice to you would be to hook them back up, listen to them. Then BEFORE you report back, go back through the questions and comments in this thread and answer/address them.

Your issue is within the posts here.

Once we know what is happening then we can guide you to the next step. At this point we are just shooting in the dark looking for possible issues [in a speaker] that might have nothing to do with the speaker, but everything to do with another component or both. Besides, rumor has it that when speakers sit in the magic closet for a while, all of a sudden they mysteriously work. :eek: :eek: :eek:

phxrider

Now that would be funny, wouldn't it?

I agree, we've gotten as far as possible on speculation based on my limited input. I will go through some of the suggestions listed above and narrow things down.

treitz3

No, I'm being serious.

phxrider

Alright, got 'em out and unfortunately, no closet magic....

But I had no problem reproducing the problem. It is DEFINITELY the mid/woofers on the left channel speaker. The tweeters sound fine.

PolkClyde

I recently ordered RD0194-1|5 TWEETER SL2000 8ea
RD6519-1|5 DRIVER MW6510 1 EA

guess what they were delivered but to the wrong person. I don't know who. They even sign for the package and misspell my name. I wonder why FED EX didn't pick up on that. My neighbors said they didn't see a fed ex truck the entire day. I call fed ex and they said that they will investigate. I also have sent Polkaudio an email about this problem. I will call them on monday. have any of you club polk members had this problem with fed ex? I am so upset.The cost is over $400.00 I want my replacement drivers. can anyone give me some advice. thanks

treitz3

phxrider, take the offending woofer with no power applied to the speaker and push the woofer in and release it a couple of times. Do you feel any grinding, scratching or any other type of abnormality that prevents the woofer from traveling in and out freely?

Dennis Gardner

It sounds like a woofer with very close tolerance in the voice coil/magnet gap that rubs when heated up by high volumes. This can happen when the glue over the coils melt a little, it makes them fill the gap more. Time for a new driver.

phxrider

Yes, there is one woofer that does that, the lower inner one. Since I hooked it up w/o a crosslink cable last night and the sound came from the inners, I guess this means the inners are the mains and the outers are the SDA drivers? Is there any reason I wouldn't want to take the woofer out and hook it up to a source by itself to verify?

When I listened last night, it sounded like both drivers were distorted, would this be normal if it was a single bad driver, maybe an acoustic effect or something? Is there any danger to the amp or speaker if I test the speaker without the suspect driver in the circuit?

Dennis Gardner

You can unhook any driver, just leave it in place to pressurize the cabinet, or you might not get the same excursion from the driver you are testing. In other words, test them in place.........