WTB MW6511, or where to find ?

itsnotme

Need a replacement MW6511 for my SRS 2.3 ... Damaged it while watching Oppenheimer last week.... All of a sudden too much bass and I was too slow with the volume knob. Now it distorts at lower volumes and has a scratchy noise when pressing in the cone. So far have not found any online.... any help appreciated.

pitdogg2

Shifted magnet maybe?

Gardenstater

I was thinking torn spider. Those 6511s may be more prone to overtraveling compared to a driver like 6502s. If you do a calculation of BL x Compliance/DCR you get 2.2x greater vs. 6502.

itsnotme

Thanks for the suggestions. I had examined the spider including while moving the cone and saw nothing damaged. As for shifted magnet, my reading is that is usually caused by blunt force trauma and results in seized condition, which is not the case here. The cone moves freely, but makes a slight scraping noise when being moved. I also tried the trick of installing it upside down, didnt help.

Toolfan66

itsnotme wrote: »

Thanks for the suggestions. I had examined the spider including while moving the cone and saw nothing damaged. As for shifted magnet, my reading is that is usually caused by blunt force trauma and results in seized condition, which is not the case here. The cone moves freely, but makes a slight scraping noise when being moved. I also tried the trick of installing it upside down, didnt help.

A slightly scraping noise can still be a shifted magnet ( a slightly shifted magnet ) 😎

pitdogg2

Toolfan66 wrote: »

itsnotme wrote: »

Thanks for the suggestions. I had examined the spider including while moving the cone and saw nothing damaged. As for shifted magnet, my reading is that is usually caused by blunt force trauma and results in seized condition, which is not the case here. The cone moves freely, but makes a slight scraping noise when being moved. I also tried the trick of installing it upside down, didnt help.

A slightly scraping noise can still be a shifted magnet ( a slightly shifted magnet ) 😎

And it can get that way from sudden movement. The glue is well documented to just finally let go, even just sitting there playing nothing.

My guess is that driver is very fixable.

Gardenstater

There's compliance of the drivers when they are made and compliance after they are old and worn.
Could be a lot looser. Also I would want to see if the voice coil has gotten separated from the cone and also if the voice coil is rubbing on the pole piece anywhere (check with shims). Time for a surgically performed dustcapectomy

itsnotme

Hmm, I had not considered the possibility of slightly shifted magnets caused by overexercising its mechanics (and time)... figured the voice coil got cooked and warped.... Something is definitely rubbing in there, much more so when pressing the cone in on the left or bottom than on the top and right. I guess the only way to tell is to start taking it apart. The question now is whether to start ordering exacto knives glue and jig components or to find a pro..

Gardenstater

I'd definitely check their DC Resistances. Supposed to be 3.130 Ohms.

joebass3

itsnotme wrote: »

The question now is whether to start ordering exacto knives glue and jig components or to find a pro..

If you're a hands on kind of person, it definitely is a very satisfying project!

itsnotme

The damaged speaker impedance looks to be off a bit. Reading 3.4 while I get 3.1 when checking two of the other (presumably good) 6511s. My multimeter is a POS and the readings bounce around a bit, but am fairly confident in the finding that the damaged one is 0.2 to 0.3 ohms more than the others.

I am not much of an expert at shipbuilding in a bottle type things, but guess I am up for trying a shifted magnet fix (in the absence of any other options).
I have read elsewhere that expectations of success should be set at 50/50.
But before going down that route, what does that impedance diff mean ?

Gardenstater

What happens to the reading when you move the cone, on the bad one and the others? Try to make sure you use alligator clips to get the most stable reading you can.

itsnotme

I bought another low end multimeter and some alligator clips...
retested and got basically the same result...
3.3 ohms on the (presumably) good one, and 3.5 on the damaged one.
When moving the cone by hand, both multimeters go nuts, readings all over including 0s, but
if depressed cone is not moving (eg placing a roll of tp on the cone) the readings stabilize to the above numbers. This is the case for both the damaged and presumably good speaker.
I was surprised that the readings went nuts on the good one when moving by hand.... hope that does not mean it is also bad...
Wondering if maybe those readings are caused by the multimeter being confused by the small current created by the movement (?).

Gardenstater

That's interesting. I'm not surprised the reading was unstable/went nuts while the cone was in motion, due to the back EMF.

I really was wondering if there were any positions of the cone where you got a different reading with the cone stationary. That would definitely indicate voice coil damage. You didn't see that so probably the voice coil is OK.

F1nut

3.3 ohms on the (presumably) good one, and 3.5 on the damaged one.

Not every driver of the same model is going to measure exactly the same. Yours are seriously close enough.

Gardenstater

Gardenstater wrote: »

That's interesting. I'm not surprised the reading was unstable/went nuts while the cone was in motion, due to the back EMF.

I really was wondering if there were any positions of the cone where you got a different reading with the cone stationary. That would definitely indicate voice coil damage. You didn't see that so probably the voice coil is OK.

I should've said that they might be OK electrically but there is still a possibility that the voice coils have been physically damaged.