How do I detect a possibly damaged speaker?

[pwnz]

Yesterday, I removed the woofers from my main DIY-speakers to do some work on the crossover. The woofers are Wavecor WF259PA01, so you could consider them fairly "expensive". At least they are quite valuable to me as I had to save up for some time so I could afford a pair of them

Unfortunately, the factory-applied foam gasket is sticky as hell, so to remove them after they were properly screwed down requires an incredible amount of force.

So I carefully pulled the tweeters and started pushing on the woofer's basket from inside the box through the tweeter hole. First gently, then gradually increasing to insane grunting force.

You can imagine what happened. I slipped and power poked the area where the surround meets the paper cone. You can still see my fingernails imprinted exactly where the surround overlaps the paper cone. From the outside!

Neither cone nor surround seem ruptured, though. There isn't any unusual flexing or buckling in that area when you push the cone.

After reassembly the speaker sounds fine as far as I can tell. No audible buzzing or anything like that when feeding it pure sine waves. Measured frequency response also perfectly matches the unharmed speaker.

Still, I am uneasy about this. Is there any way to make sure the woofer is fine? Without prying it out of the box again, of course, cause I'm never doing that crap again

I own a measuring mic and SPL meter. Would a distortion measurement in REW be of any use? The woofer is behind the crossover now, so higher frequency resonances might not show up? What frequency range would you expect an array of fingernails sized cracks to impact the response. They form an almost perfect line along the glued area.

I hope I can soon forget about this stuff.

Here's an image of the damaged area:

 

[solderdude]

If it sounds and measures fine it probably is fine.

 

[McFly]

REW distortion measurements close mic’d of both your undamaged and “damaged” drivers will show any motor and surround issues. Use your good driver as the reference.

 

[pwnz]

Thank you! I just measured both woofers at 105 dB, distance to mic approx. 1 ft.

Frequency response (orange is the damaged one):

Distortion undamaged woofer:

Distortion damaged woofer:

It seems to produce LESS distortion above 100 Hz but more below. What do you think?

 

[sergeauckland]

Those look pretty well matched to me, so I wouldn't worry about it. As to the slight difference in distortion, that could well be normal manufacturing tolerances. Unless you have measurements of both drivers before the unfortunate mishap, it's impossible to know whether anything's changed.

Regardless, it doesn't look to me as if there's anything wrong with the 'damaged' one so I wouldn't worry about it.

One thing I will say, and I've learnt this to my cost many times, is 'Leave Well Enough Alone' (also known as 'If it ain't broke, don't fix it)

Many a time and oft, I've had something working well, but couldn't leave it alone and wanted to 'improve' it, so I fiddled, and broke something.

S.

 

[pwnz]

Thank you.

I have never measured distortion before so, as you said, we'll probably never know if anything has changed.

Just wondered if the box itself or mounting/damping/loose wires ... could contribute to distortion figures in such a way. But I'd have to pull that woofer again zu find out which will definitely result in more damage

I will try not to fiddle with it for a week or so and see if I can find peace. If not, I'll just buy a new woofer

 

[pwnz]

For those who are interested:

I pushed both woofers to Xmax with a 15 Hz sine signal and shot 240 fps slow motion video of the same region. Copy 1 has the visible fingernail mark / line along the top, copy 2 is the unharmed speaker.

Copy 1:

Copy 2:

Personally, I see no difference in their movement. No creasing or flapping. The surround/cone seems to have maintained all structural integrity.

So ... case closed. Thank you for your patience and support