Identifying blown driver

wallstreet

I need some strategies for identifying a blown driver. While watching Casino Royale, a loud pop came from the left LS90 speaker during the airport action sequence. Which, BTW, is an awesome sequence. The right LS90 played flawlessly and the sound levels were at a moderate level. The speaker sounded its normal outstanding self except for that one sequence where the plane guns the engines to avoid hitting the jet fuel tanker (a truly bass bonanza). I upped the xover from 60 to 70HZ and that helped somewhat, but I'm only treating the symptoms and not the problem now.

treitz3

Hi Wallstreet. I've never blown a driver *crosses fingers*, so this may not be the best way to approach this. What I have done when diagnosing my friends blown drivers is first determine whether it is a tweeter or an actual woofer. From the sounds of it, I would imagine that you have a blown woofer.

For this, I would try to recreate the problem to determine which woofer it is that's blown. You know that during that scene a loud pop is heard, so what I would suggest is turning down the treble all of the way and try to make the woofer(s) reproduce the pop. If you are successful, backtrack the movie to just before where the foreign noise starts and literally walk up to the speaker and put your ear in front of the speaker. About a half a foot away is fine. Now play that sequence again. During that sequence that made the speaker pop, you should be able to quickly determine which driver is the faulty one. It might take a couple of times doing this depending on how many drivers you have within your speaker, but it's a fairly easy way to determine which driver has the issues.

For an even easier test, you can take the grill cover off and manually push each driver [not the tweeter] in. When gently doing so [applying pressure equally over the cone and not the dust cap], see if you feel any grinding or abnormalities within any driver. They should all move in and out without any obstructions whatsoever. If you do find that one of your drivers has an obstruction, then you have found out which driver to replace and you don't need to even bother with the test above.

If this does not yield the answer to your question, then get back to us please. Good luck and I'm sorry to hear about issues with your rig. That's always aggravating.

treitz3

Thought of something else as well. Depending on how old the speaker is, your surrounds that attach the cone to the frame may be shot. That will sometimes make what folks interpret as a pop coming from the speakers. All that needs to be done to determine if they are shot is a visual inspection. Do you see any dry-rot, splitting or tears in the surround?

If so, a replacement of the entire woofer will yield the best results IME.

xandra

A polk tech once suggested I take off grill, hold pillow over one, then the other to determine...

wallstreet

I'm going to pull the speakers this week and take a closer look. The speakers have the rubber surrounds, so they look and feel just as good today as they did when I bought them.

F1nut

With your fingers spread out evenly around the outer edge, just inside of the surround, gently push in and let it out. The driver should move freely without any scratching noise. If you hear/feel any scratching or if the driver doesn't move freely, it's toast.