Opinions wanted: 240Ti vs L-150A

[JeffW]

Here's a vid of Edgewound putting new foams in some 044Ti tweeters, for reference

https://www.facebook.com/UplandLouds...0368414884259/

[grumpy]

Nice. You can see how squishy the foam is. Lots of good info!

Congrats Grandpa Ken!

[BMWCCA]

Here's a vid of Edgewound putting new foams in some 044Ti tweeters, for reference

https://www.facebook.com/UplandLouds...0368414884259/

Did I miss a step? Did Edgewound glue the "plinth" back to the base after running the sweep? If so, what type of glue was used? Thanks for that.

[Dagfinn]

Very informative video, thanks a lot ! I think the foam I have found is very similar to what he's using, very soft. I will trim them a little, and maybe "dome"-shape them as well. He's compressing more than I imagined, so I'll make them taller than I first planned. I was afraid of over-dampening, but seeing what he does I'm confident I'll be fine .

He doesn't say whether he glued or not, he just skipped from "be very careful" to "ok, the diaphragm is reattached to the magnet". He does mention "checking alignment" when mounting the cover, so I'm not sure it's fixed in place? Guess I'd be partial to using some dots of the same double sided tape as originally used, to maintain position while reattaching the cover and still be able to disassemble it again in the future...

Great video find!

[JeffW]

I don't know if he re-glued or just used the bolts to hold it - I've seen posts where the glue was omitted.

He has quite a few vids on his Facebook. I don't have Facebook, but there's a link on his homepage

http://www.repairspeakers.com/

[LHorn]

Sorry to butt in here..but I have 8 of the 044Ti's to refoam as well. My question is this...is the foams purpose to mechanically dampen the dome from resonating or is it to block sound waves from bouncing around under the dome hitting the pole piece? If the latter I could see using foam..but if it's to dampen the actual dome why not coat or put a drop of something rubberized on the inside of the dome?

I did see a while back where someone coated the outside of the dome with Aquaplas...but I wouldnt want to do that..even if I could get Aquaplas.

[JeffW]

In the vid above, Ken mentions that the foam is to contact the rear of the dome to damp the ringing of the titanium dome.

As to why JBL decided on that as opposed to putting a drop of something on the back of the dome, I couldn't say.

[LHorn]

Right...I guess it makes sense..if the ringing would be caused by waves bouncing around under it the foam wouldn't necessarily need to be touching the dome...just like the insulation in a cabinet doesn't have to touch the drivers for instance.

Thanks Jeff.

[macaroonie]

In the vid above, Ken mentions that the foam is to contact the rear of the dome to damp the ringing of the titanium dome.

As to why JBL decided on that as opposed to putting a drop of something on the back of the dome, I couldn't say.

Aquaplas seems to work pretty well on the 2450SL diaphragm.

Might be worth a go if you can get your hands on a little.

My own digging on this subject suggests that the coating on the 2450SL is much finer in texture than that used on bass drivers.
Mortar and pestle ??

Edgewound does Aquaplas treatment on bass drivers ( I believe).

[grumpy]

JBL did put aquaplas on these Ti domes... LSR32 and 28. 053Ti ... don't know if that was instead of, or in addition to foam.

Also, the residual adhesive on the 'plinth' is sufficient to keeo things from moving around once the screws are in.

[macaroonie]

Grumpy was that on the outside ?

I got a small amount via a connected member and applied it as he did in a thread here.
It definately took away that tinsel sound that Ti has. It seems quite gritty , is water soluble and paints on quite easiy , when it dries it is well stuck to the dia , not flakey.
Actually for a non factory application it was easy to get a satisfactory visual result.
Just enough to get an even non patchy coating.



Outside it is. No ribs on that diaphragm I notice. My conclusion is that the ( Antivibe ) is a sufficiently efficatious treatment that they were able to do away with the rib forming process.

[JeffW]

Aquaplas seems to work pretty well on the 2450SL diaphragm.

Might be worth a go if you can get your hands on a little.

My own digging on this subject suggests that the coating on the 2450SL is much finer in texture than that used on bass drivers.
Mortar and pestle ??

Edgewound does Aquaplas treatment on bass drivers ( I believe).

If they weren't so hard to come by, it might be worth a shot. I'll not be trying it on mine

[grumpy]

Yes, same lack of ribs on the aquaplassed 4" dias. I bet they tried it. Probably dampened the upper freq tizz that the stiffened/ribbed diaphragms added to measurable and noticable effect, so why bother if it took that away. (conjecture)

The factory black coating looks sprayed on and the 'grit' is quite fine, unlike the stuff folks were hand painting their 2435Be drivers with awhile back (most seemed happy with the result, regardless). Front vs back? Probably much easier to evenly spray a diaphragm on the convex side, and easier to identify and differentiate in the marketplace... less distracting in the studio on an all black monitor. (more conjecture)

I have a LSR28 with a wrinkled dome and a spare 053Ti available to replace it (not in any hurry as the wrinkled one ended up sounding fine)... but if I ever swap the new one in, I can check to see if there's any foam behind the dome. I am a bit curious now, but don't hold your breath. Maybe someone else has taken one apart. I don't think they ever sold repair kits, just entire tweeter assemblies.

[LHorn]

I was looking at the 1986 Ti brochure and found this interesting. JBL states that the diamond pattern in the surround and the ribs in the dome raises and lowers the resonant frequencies to above and below human hearing...along with strengthening the material. Nothing mentioned about the foam.

In the one paragraph they state that other manufacturers use "high internal dampening" to control resonances...but I dont know what that means. Is the foam considered internal dampening? Is the foam an afterthought due to the patterns not quite doing what was on paper?

[Dagfinn]

*Sigh*. If you look closely at the pics of the tweeter, there's a small black dot in the middle of the dent in the first picture. My friend in France recieved it like that, yet in the pics posted by the seller it was undented. The black dot is a tiny needle hole . It looks punctured on purpose. I didn't catch it until today, my eyesight is less than perfect.

Anyway, looking at the foam plug again, there's a lot of pressure needed to compress that plug from 1/2" to the height of the dome+thickness of plinth. I wish he hadn't skipped that part in the video. For me, the weight of the plinth/diaphragm isn't enough to hold it in place, by far. The stickyness is gone from the old tape; I'm wondering if it was there just to be able to assemble it, due to the pressure from the plug? The tolerance for misplacement is tiny, and any foam plug I can imagine will push it out of position without adherence.

But, what will the hole do, you think?