Polk SDA 2 - Bad crackling sound in left speaker. HELP!

Smit

Hi all.
New to the group. I own some Polk SDA 2's (1 tweeter - 2 mid-woofs) and I love their sound but I don't think I'm getting all that I can out of them with my current set up. So I tore down my studio to rearrange. When I hooked everything back together I switched amps to a Crown CE 1000. 275w at 8ohms - 450w at 4ohms. I had been powering it with a Hafler1600 (75w/8ohms) figuring I would get a truer sound with the added power. Before I hooked it up I tried to find out if the Crown is a common ground amp. Couldn't ascertain if it was so I just said 'screw it' and hooked it up. (cue ominous foreshadowing doom music...)

So I anctiously powered everything back up and the Polks sounded phenomenal!! HUGE.

Until...my left speaker began to crackle badly. The sound sputtering in and out. Then it would correct itself and sound great again...then more crackling. I freaked out and shut it all down. Checked the wiring and connections. Made sure that it was in fact the speaker and not the amp or something else. It's definitely the speaker. So here I am thinking....

Damn. Did I blow something??

Anyway, that's my tale of woe. I was hoping someone here could give me a plan of attack to further diagnose or fix the issue.

Thanks in advance for any assistance.

- Smit

F1nut

3 posts for the same damn thing....unbelievable!

xschop

According to F1, ULTSOx3.

Smit

Sorry for the multiple posts. How can I delete?

F1nut

No worries, we're moving on. Now if I could just figure out what ULTSO means.....

TennMan

Hook the speakers back up to the Hafler and see if the problem goes away.

xschop

U Let The Smoke Out... Of all people, that acronym should have rang a bell lol.

Smit

Problem went away going back to the Hafler. Low volume and high there is no cutting out or crackle. However, I don't think there is enough juice to properly power the sub radiators. They're there....but I feel they should have a bit more punch/rumble.
Need to look into a proper integrated amp to run these correctly. Seems to be a lot of posts regarding amps for SDA 2s & 2Bs. That being said I'm always open for suggestions. Thanks for the assistance.

Tried to research ULTSO to no avail.

TennMan

The "sub radiators" are passive radiators. They don't require any power from the amp. They are coupled to the mid-woofers by air in the cabinet and that is what makes them move. If you feel there is a problem with the passive radiators not working correctly the problem is likely to be an air leak in the cabinet.

Do this test. Press in on the passive radiator with your finger tips placed in the center of the passive radiator and hold it there. You should see the mid-woofers move outward and then slowly retract. If yours retract quickly you probably have an air leak in the cabinet, usually around the gaskets that seal the drivers or passive radiator to the cabinet.

Normally a lack of power won't cause a problem with just the passive radiator unless you are cranking them up really loud and causing distortion. If you are looking for rumble as the measure of a speaker's performance you might want to invest in a sub-woofer. They do a lot better job of rumbling than Polk speakers do and a powered sub-woofer doesn't require a bigger amp.

Smit

Thank you for the advice. I performed your test. Gently pressed on the PR...the MWs pushed out and retracted a bit before holding their position. When I released pressure on the passive radiator the MWs retracted further back to Normal position.

So....from that description what do you think? Good seals/ Bad seals?
Not having done this before I am still unsure.

Should they have retracted with one long slow movement?
Again, mine seemed to push out, retract a bit and hold and then retract all the way when I released pressure on the passive radiator.
Is there any other diagnostics I can perform?

Another thought... now that I understand the speakers operate effectively by a sealed design, could the 'crackling' and sound break up I experienced possibly be due to leaked pressure by a bad seal when more power was driving the speakers? Or is it more likely that the Crown was simply overdriving the crap out of them like a sledgehammer? Definitely wrong amp for the job.

Before the bad audio issue occurred the speakers sounded amazing. Definitely more low end than I get with the Haffler. And 'rumble' may not have been a good descriptor for the low end sound I desire. I understand I am not going to rumble the room with these. I'm not a basshead who wants to shake the neighborhood. But the low end was way more pronounced with the Crown (before break up). Rich and full along with the crisp highs and neutral mids. I think it gave me a glimpse of what these polks can do.

Smit

Found a bunch of great info here...
https://forum.polkaudio.com/discussion/89778/want-more-bass-seal-your-speakers
Again, thanks for your help.

Smit

From F1nut:
.....the test should be as follows, press the PR all the way in and hold it there. The mid-drivers should push out all the way and move back slightly after 3 to 5 seconds, but not all the way back until the PR is released.

My mids push out all the way and move back slightly well before 3 to 5 seconds...
More like 1/2 second. I believe I have leakage.

So What comes next? Mortite around the MWs? Inspect the cabinet seams and fire up the hot glue gun?

Trying to read up on as much as I can before making a move.

pitdogg2

No moretite you'll regret it.
One of two check screws for tightness or disassemble and reglue cabinet with powergrab adhesive.

Unless gaskets are tirn they should be ok

Smit

Thanks

F1nut

Hang on, there should be no need to disassemble the cabinets and I strongly suggest you don't try. If needed or desired, simply run a bead of sealant around the seams on the inside.

Never use Mortite.

F1nut

Smit wrote: »

From F1nut:
.....the test should be as follows, press the PR all the way in and hold it there. The mid-drivers should push out all the way and move back slightly after 3 to 5 seconds, but not all the way back until the PR is released.

My mids push out all the way and move back slightly well before 3 to 5 seconds...
More like 1/2 second. I believe I have leakage.

So What comes next? Mortite around the MWs? Inspect the cabinet seams and fire up the hot glue gun?

Trying to read up on as much as I can before making a move.

Sorry that should read, the test should be as follows, press the PR all the way in and hold it there. The mid-drivers should push out all the way and move back SLOWLY TAKING 3 to 5 seconds UNTIL THEY COME TO REST, but not all the way back until the PR is released.

pitdogg2

F1nut wrote: »

Hang on, there should be no need to disassemble the cabinets and I strongly suggest you don't try. If needed or desired, simply run a bead of sealant around the seams on the inside.

Never use Mortite.

Yes correct! Poor wording on my part. I was referring to removing the drivers not to disassemble the actual cabinets.

TennMan

I agree with all the above. Sealing the cabinets is always a good idea.

could the 'crackling' and sound break up I experienced possibly be due to leaked pressure by a bad seal when more power was driving the speakers?

I don't think a leaking cabinet would cause a crackling sound nor do I think too much power is causing it. Lots of people here on the forum run 2Bs with high powered amps without a problem. A crackling sound in the Crown and not in the Haffler makes me think the Crown could have a capacitor breaking down when you crank it up. That will cause a crackling sound like you describe.

Faustin

TennMan wrote: »

I agree with all the above. Sealing the cabinets is always a good idea.

could the 'crackling' and sound break up I experienced possibly be due to leaked pressure by a bad seal when more power was driving the speakers?

I don't think a leaking cabinet would cause a crackling sound nor do I think too much power is causing it. Lots of people here on the forum run 2Bs with high powered amps without a problem. A crackling sound in the Crown and not in the Haffler makes me think the Crown could have a capacitor breaking down when you crank it up. That will cause a crackling sound like you describe.

^^ I agree. My thoughts are that there is a problem with the Crown amp. Do you have another set of speakers available that you can connect to the Crown to see how they react?

Smit

Firstly, thanks to all for your replies. Really appreciate it.

F1nut: Thank you for the clarification on the pressure test. Appears that it take maybe 3 seconds or slightly less for the mid drivers to slowly retract.

Thanks for the tip to avoid mortite.
And possibly running a bead of sealant around the inside seams.
Makes sense.

I did go around all the screws to the drivers and radiator to make sure they were not loose. There were two screws on each of the tweets (R & L) that appear stripped. Not really bad, but definitely not biting solidly. So there's that fix needing to be done.

As for the Crown amp...
TennMan: I do not have another set of speakers available to test the Crown amp. Although when I was experiencing the 'crackling' it was only in the right channel. I switched the leads and it remained in the right channel. Would that then rule out the capacitor issue? Forgive my ignorance but are their capacitors for each channel L & R?
Is there a different test I could do to test the caps on the Crown?
At any rate, I will try to get another set of speakers to run a test.

Although now the Crown has me a bit jittery. I believe F1nut commented "cheap mega watts syndrome"... From that I got the impression the Crown CE1000 might not be a good match for the SDA 2s.

So I think my to do list is:
1) Fix the stripped screws on the tweets. Possibly with a threaded insert. I believe I saw this posted on a different post on the forum. Unless you all have a better avenue.
Then perform pressure test again.

2) Possibly seal the inside seams.

3) Test the Crown amp with other speakers and or begin looking for a different integrated amp that works well with the Polks. Hopefully won't have to spend an arm and a leg.

Thanks all!

TennMan

Smit wrote: »

...
As for the Crown amp...
TennMan: I do not have another set of speakers available to test the Crown amp. Although when I was experiencing the 'crackling' it was only in the right channel. I switched the leads and it remained in the right channel. Would that then rule out the capacitor issue? Forgive my ignorance but are their capacitors for each channel L & R?
Is there a different test I could do to test the caps on the Crown?
At any rate, I will try to get another set of speakers to run a test.

Although now the Crown has me a bit jittery. I believe F1nut commented "cheap mega watts syndrome"... From that I got the impression the Crown CE1000 might not be a good match for the SDA 2s.
...

Trying another set of speakers may not be the best way to test the amp because they may not put the same load on the Crown amp that the SDAs do.

A better test in my opinion would be to use a different amp with lots of power capable of driving your SDAs and see if you have the same crackling problem. Adcom and Parasound are popular choices for driving SDAs.

I don't want to offend any Crown fans but I don't think the Crown amp you have is a good match for your SDAs. If you find out yours is defective I wouldn't spend much money to repair it. I would spend my money on a different amp and sell the Crown as is.

Smit

Only other amp I have is a Radio Shack (Pyramid) MPA 200.
100 per channel @ 8 ohms - 120 at 4 Ohms
Again, probably not a good amp to power the SDAs but maybe enough power to run a test. It's more power than the Hafler (60 @ 8ohms / 75 @ 4ohms)

Thanks!!

Gardenstater

I think that RS amp should be fine for a "crackle" test.

If you don't want to go the hurricane nut route at this point in time, you can repair a stripping screw location by removing the screws at the bad locations and spraying them with a couple good coats of dry lube and allow to dry. Mine is from HD and has teflon in it and is Blaster brand. Then use some JB Weld or the like and with a toothpick get a decent amount of it into the stripped hole and move the toothpick around to try and spread it evenly. You don't want so much that it comes out when the screw is inserted. Then just put the screws in as usual but without torquing them down of course, and let it all cure for a few hours or overnight. After that point you should be able to torque those screws down and even remove and replace them without problems. Worked for me on my subwoofer screw that was stripped.

Smit

Great tip! Thanks - will try this on the stripped screws.