Replaced Driver... Interesting / Unusual Defect ? (1 Viewer)

[SeanA]

I just replaced one of the midrange drivers on my Wharfedale Emerald center channel speaker. I had started to notice a buzzing sound from the right side driver when sound peaked, and confirmed it when I did a speaker balance with the AVIA disc. The buzzing became very noticeable with the AVIA noise signal (from the speaker balance test).

Anyway, Wharfedale was very good about sending a replacement driver and I had the driver at my doorstep in just a few days after contacting IAG America (Wharfedale's rep in the U.S.). I replaced the driver and ran the AVIA noise signal again, and the buzzing was gone. I was than looking at the driver I replaced and trying to decide whether to keep it or just throw it out when I noticed the metal flange at one of the four attachment points was bent inward (in the direction of the speaker enclosure). It is very noticeable, and now I wonder if this could be the cause of the buzzing ??? If the metal flange did not seal properly against the enclosure at this point, would this potentially cause the buzzing I experienced ? I am also wondering if I could straighten it out, would I have a perfectly good spare driver ?

I also have one somewhat related question. When I screwed the new driver back in place, I never got the sense of the screws getting progressively tighter and so I don't get the warm fuzzy feeling that the driver is sealed tightly against the speaker enclosure. Is there anything that can be done to improve the "tightness" of the seal, such as using wood filler in the screw holes ???

 

[Andrew S-]

sounds to me that the speaker isnt secured properly. this could deffinately cause any number of sounds.

i would either fill the hole with wood glue or maybe some liquid nails and then try again.

 

[DavidES]

If you have a drill or Dremel and want fresh holes, drill out a new set of pilot holes each about 1/4" away from old ones carefully using driver holes as a template. Don't use same size drill bit as screws but use a bit about half the diameter of screw so that screw threads can bite into MFD but not break up wood.
Caulk the old holes with elastomer-type outdoor caulk (it doesn't become brittle over time) and use the new holes to mount driver.

I'm assuming this is flush-mounted so isn't there a black felt-like material in between the baffle recess and the driver?
If so don't damage it any more than it is, align the holes in it with the newly drilled ones in the baffle.

Just a suggestion.

 

[SeanA]

DavidES,

Not a bad idea. I just might give that a try. I really think over time this driver is going to loosen up and loose its seal, so I need to do something. I may try Andrew's suggestion first since it is a simpler approach.

The speaker is a flush mount and the back side of the speaker has a thin gasket material for sealing. Seems the gasket could be a bit more substantial, but I think the real problem is the inability to get good clamping pressure with the 4 mounting screws. And I am sure it was even more difficult to create a good seal with the bent flange on the old driver. It was probably acting like a spring in resisting the tension from the fastener.

 

[DavidES]

If you do caulk the old holes let it sit for a day, I've just read that silicon fumes will destroy drivers. You might could use wood putty or drywall spackling instead or none at all if you can use that gasket. I just found this today if you're interested in replacing it.

 

[Geoff L]

Sean

You can try one of the suggestions above as they all will work for new mounting holes. If they just won't tighten down but still thread in, get some plumers tape and wrap the screws with it. Should build the threads up enoung to be able to tighten them up snug, but not overly tight.

Another fix, is being that they have trim rings around the driver once mounted, you could use a (slightly over size screw in the same holes).
This would most likely be the "best and easiest choice for repair" of the bad threads.
Any hardware store will have what you need, take a stock screw with you.

The thinner gasket is fine that comes with the driver, no need for rope caulk or closed cell foam tape.

More than likely the other driver is fine aside from the slightly bent flang. Might be why the screws were stripped to begin with. They tried to tighten down the flange flat in the drivers counter sunk hole at the factory. Won't hurt to try and straighten it, if you screw it up, no problem as you have your new one and Wharf will send you another if you blow or trash that one.

Hey, you get a real receiver yet????

Cheers
Geoff

 

[SeanA]

Geoff,

I like your idea of the plumbers tape best. I got a ton of the stuff and now I can put some of it to good use. That may just do the trick since the threads just need a little more bite. Maybe the plumbers tape can be considered a version of "Loctite" for wood threads ???

Hey, you get a real receiver yet????

Kick a guy when he's down why don't ya !?!? Not yet. I just got back from the Michigan NASCAR race, so my receiver $$$ went to that instead. I need to save my penny's and I should be ready for a new receiver in a month or two. I am thinking a Denon or HK, and maybe a refurbished unit from eCost.

 

[DavidES]

Huh, plumbers tape; now why didn't I think of that. So simple and cost-effective. [sound of head beating against the wall]

 

[Andrew S-]

the tape may work well if you have enough wood left.

silicone will only give off fumes while it is drying. so once it has dried you should be good.

 

[SeanA]

Resurrecting this thread because I tried the teflon tape, and it did not work. I have come up with a better idea, which I have discovered is not unique. I did an internet search on "speaker repair" and found exactly what I had in mind... some type of locking nut that would screw or bite into the wood. It is called a T-nut, but it needs to have prongs on the large diameter of the nut specifically for sinking into the wood face.

In most cases, the T-nut is hammered into the wood but this would be impossible since I would have to hammer from inside the speaker enclosure. I than stumbled upon the following neat idea for getting the T-nut to bite into the wood without use of a hammer:

Unique Method for Installing a T-nut with Prongs

I am heading to my local hardware store tomorrow to pick up some T-nuts and machine screws. Even if I have to drill open the existing holes a little bit, this is definitely going to hold the driver more securely than the wimpy wood screws. I would venture to guess that better quality speakers use a similar type of fastening method to hold drivers in place, as opposed to just wood screws.

 

[Brian Bunge]

Sean,

Just be careful. T-nuts are notorious for breaking loose when used in MDF and particle board. If they do, they'll just spin around in there and you won't be able to take the screw out should you ever have to replace the drivers again. For this reason, I prefer threaded inserts. These screw down into the wood from the top and then you use machine screws just like with the T-nuts.

 

[SeanA]

Good thought Brian. It did occur to me that some manufactured types of wood may not hold the T-nuts as well as intended. I may try a little glue as a back up, or check for the threaded nuts at the hardware store. That would really suck if you needed to replace a driver and couldn't get the screws out !!!

So do the threaded nuts have reverse threads ? And when you say they screw in from the top, are you saying from the outward surface and not from inside the enclosure ? If so, I would think I need to create a counter-sunk hole for the head of the nut.

 

[Geoff L]

Ok heres a couple more if you care to try.

1)- Fill the screw hole with hot glue and let it cure about half way. Put screw back in, no drilling. Tighten the next day.

2)- Also epoxy wood putty bought in a small squeeze tube. Fill the hole let dry then re-drill with smaller size bit than the screw and install.

3)-Get an oversize screw and drill the basket screw hole out if the screw wont fit threw it. Then tighten that sucker down just firm.

T-nut will be a bitch with that center speaker as I have one. It will work but will be a tuffy.

Best of luck
Geoff

 

[SeanA]

Hey Geoff,

Sounds like you have tried some of these techniques in the past. I have tried filling holes with wood putty in the past, but never quite seem to be able to get the hole completely filled in. Since these are very small holes, I did not bother to try filling them in.

However, I can say now that the T-nuts work, and it really wasn't too bad !!! I was very careful with everything and it ended up taking a little less than an hour and a half to re-fixture two drivers. The T-nuts worked just as they should and did not damage the wood. I did re-drill the holes to open them up slightly, and I put a little bit of wood glue on the back face of the T-nut. The technique that I presented in the link above worked like a charm. I had to stack a bunch of washers under the wing-nut, but I think the washers also helped to distribute the load better since they were wider than the wing-nut itself.

Now the question is do I want to do this with my Wharfedale Emerald towers ??? Nah... If it ain't broke, don't fix it. But if I ever do have to replace another driver in the future that is held in place by simple wood screws, I would not hesitate to use the T-nuts with machined screws. It definitely clamps more securely on the driver than wood screws ever could.

 

[Geoff L]

Nope not really, just stuff I think up that may or may not work. :b

So is the buzzing, rattel, distortion, Center channel problem now gone bye bye??

Did you get your H/K yet and if so how the calibration/setup coming along??

Regards

 

[Brian Bunge]

Sean,

Here's an example of what the inserts look like. This pic shows an insert that can be installed with a screwdriver. Some require a hex wrench but either will work fine. You simply drill a pilot hole for the inserts, screw them in and then bolt in the driver.

http://www.rtlfasteners.com/Merchant...ategory_Code=Q

 

[SeanA]

Geoff,

You probably would make a good design engineer.

Buzzing is gone now. I really think it was due to the bent flange on the driver and thus not getting a good seal. And the poor bite from the wood screws certainly did not help.


Brian,

Thanks for the link. I am saving it in my "favorites" just in case. I have seen inserts of this type that are molded into plastic, but didn't know there are types also made for wood. I guess the only concern would be whether or not the insert would back out when backing out the screw. I guess a little bit of glue with the insert would help prevent that from happening.

 

[StevieP]

Easiest thing I have found to do is--Wooden toothpicks, stick into holes, then break off flush, and if it makes you feel better, a little Elmers wood glue.

I've had good luck both ways.

Hope this helps,
Steve.