Polk sun making thud sound

[Deleted member 38504]

Ok so my Polk sub DSW550i has been making a thud sound when I power it on.

If I turn off all the mains ,and power it on,the sub makes a thud. After that it plays like normal.

Called the profx guys, he came over for a home visit and told me the sub was not getting earthing,hence the sound. So now he connected a physical wire from my amp into to earthing socket in the main switch. 7 out of 10 times the thud doesn't come but it's the 3 times that's annoying me.

I don't know if he's blowing smoke through his ass or if there is a problem with the sub. I've called them next week again.

There is no problem of earthing or grounding in my house. Everything was inspected by the maintenance team at home.

The profx guys say the sub and in turn the amp needs to be grounded. If that's so,how come all the wires are two pins? Why not give a earth and make it three pin?

Can anyone share some light on this please thank you.

 

[superczar]

There is a good likelihood that the output stage Capacitor has leaked
I had a similar problem in my Pro 500 - You can unscrew and pull out the plate amplifier in the back and examine for any signs of bloating/leakage on the cap

The Cap can be easily spotted by following the speaker wire leads to the board they go to - The big Cap right next to where the wire terminates is the one you need to take a look at..

Mine had leaked electrolyte on the board - Had to pull it out, clean the board and replace the Cap -

 

[efernand1]

Hi Derek,

I suggest you call ProFx again and explain this.....tell them also you are a HFV member where a lot of members have Polk stuff and also some more potential deals in the pipeline (business for them pan india).

With this, I am sure they will inspect on the spot and resolve it.....

 

[Deleted member 38504]

This is happening with my brand new sub since day one.

Anyways next week will have it checked out. Thanks. Too many variables,quite a few things could be wrong I guess...

 

[superczar]

if it is a brand new sub then the cap can't be the issue (in all likelihood)
Can you try using another source to rule out a LFE out issue from the AVR- or if that is not possible, try using the line level or even the speaker level inputs on the sub to isolate the issue?

 

[Deleted member 38504]

Superczar,thanks so much but I have no clue to what u just said lol sorry man I'm a lil daft

 

[superczar]

Superczar,thanks so much but I have no clue to what u just said lol sorry man I'm a lil daft

with all those intimidating connectors, We've all been there at some point in time mate!
What I meant was that your Sub has multiple ways of taking an input.
The default method is to use a single cable from the AV Receiver to the LFE in socket of the subwoofer - Now if for some reason, your AVR is sending a high pulse over this when switching on (or a faulty cable), you will get a loud pop

If the problem is with the cable/AVR then you shouldn't get this thud/pop if you use the alternative methods for connecting which are :

a) Speaker level inputs - The Front Left/right speaker wires go the speaker level input on your sub and the speakers are connected to the the corresponding output on the Subwoofer

b) Line level inputs - If you have a pre out socket on your AVR, two separate cables for Left and right will go the sub

in both these cases, you will need to go to the AVR settings to mark the speaker settings as No subwoofer

The Pro 550 manual should give you all the necessary details to wire them this way

 

[efernand1]

Hi Celester340

If I recall correctly, there were a couple of posts last year where Polk subs seem to face this challenge of loud pops....

As suggested, read the ops manual again and try different recommended settings which would perhaps help resolve the matter.

 

[Deleted member 38504]

Quick question, is it compulsory to ground the amp? If so, why don't the company provide a three pin? All my sources, my sub and the amp have only two pins..... So is the grounding of the amp absolutely necessary?

And if so, why don't the manufacturer provide it?

Sent from my ONE A2003 using Tapatalk

 

[efernand1]

Hi,

Not necessary as per my understanding and usage experience.

 

[Deleted member 38504]

Everyone I have asked including the sales guys at profx keep saying grounding is required. It's a must. So again,back to my previous post.

Guys who have grounded their amps etc,can u all shed some light?

 

[superczar]

Everyone I have asked including the sales guys at profx keep saying grounding is required. It's a must. So again,back to my previous post.

Guys who have grounded their amps etc,can u all shed some light?

Nothing extra to do really!
Almost all AVRs take a 3 pin supply so as long as your earthing works fine, you don't need to do anything over & above that.

PS: I see you have mentioned that your amp has only 2 pins - just check the power female socket on the amp to see if it has three prongs (it should), just replace the two pronged power cable with a three prong one.

PS: If you want to test your earthing, use a DMM to test the voltage between live and ground followed by live and earth - Both should return the same voltage..
Another easy and dirty way to test it would be to use a table lamp (or any other load) - connect to your live and earth to see if it works as expected...

On a separate note, before you do any of the above, why don't you do this -
just unplug the LFE cable coming from the AVR to the Sub - Now switch the sub on.
If you still get a thud, the problem is with the sub
if not, the problem is with the source

 

[Deleted member 38504]

My avr and the sub and the turntable all have two pins, do they make them with three pins?

Sent from my ONE A2003 using Tapatalk

 

[Deleted member 38504]

OK so behind my sub, I have the option USE AS LFE. The default is yes. So I have kept it as yes. I unplugged the cable from the AVR and powered the sub back on, I still got the thud. Does that mean it's a sub problem?

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[superczar]

My avr and the sub and the turntable all have two pins, do they make them with three pins?

Sent from my ONE A2003 using Tapatalk

Just checked that the model in your signature does indeed have only two pins..
Why don't you run that basic test (LFE cable unplugged - Switch on sub) to isolate the problem

 

[efernand1]

Hi Celester340

If u unplugged the LFE cable from sub and still it gave the thud after turning on indicates clearly a sub issue.

 

[Deleted member 38504]

No ed,I unplugged the cable from the AVR end while keeping the sub connected, the thud came.

Next I unplugged it from the sub end while keeping the AVR connected,again the thud.

So both ways,the thud is coming still.

 

[superczar]

QED - The sub has a problem and the profx guys are just shifting the blame !

I am pretty certain of what the problem also is (the output stage cap on the Polk D class amps is prone to blowouts)
But since your sub is under warranty, get them to fix it.

If they don't listen , call the Polk US helpline and raise a complaint... (Polk US sent a replacement Amp plate to a colleague for his 2 year old blown Polk sub - all he did was called them to complain why Polk India has 1 year warranty - they asked him if he has a local US address and shipped it to that- I carried back the plate with me on a trip)

That's how I also know that the Polk subs have an issue with the output stage cap - His original amp had the same thud issue which he ignored till the leaking Cap blew completely and shorted some of the SMD chips.
I started getting the thud noise recently and changed the capacitor with a high grade Nichikon which fixed the issue completely

 

[Deleted member 38504]

Thanks so much, the profx guys are coming tomorrow afternoon.

So this is definitely a problem with the sub then!

http://www.hifivision.com/speakers/56583-do-subwoofers-make-loud-thumping-noise-when-powered.html

Could u just go through this thread please if u don't mind and again revert here?

Thanks so much !

 

[Deleted member 38504]

In the evening got a call from profx saying they will replace my PCB for me. Completely out of the blue! Maybe they read posts here on the forum haha

Will take a few day's they said so I'll post back when it's done!

Thanks a mill guy's!

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