Surround Replacement question ....

[dllyons]

I'm installing new surrounds on four 125a & 127a 10" woofers, and had no problem with all of them until this last one. It seems that the spider on this cone seems flimsier than the rest, even though they're all fairly close in age.

First of all, 'NO' is the answer to your question as to whether I'm using shims in the voicecoil to center the cone. I've never had to do that in all of the cones I've ever done this to. But should this be my first one ?

All of the other spiders were stiff and could seemingly keep the woofer centered in the voicecoil with no help of a surround at all. This last one, seems mushy- like if it was sitting on it's magnet without a surround, the cone assembly would sink deeper thru the voicecoil than the rest. Like there should be a 'centered' position vertically. Am I being clear ?

If I should continue with this install, what recommendations would be in order to center this voicecoil in all directions ? For instance, should I try to keep the woofer facing down to allow the spider to extend somewhat while I glue the surrounds down ?

Should I use shims ? The thought of peeling the dustcap off scares me to death. It''s a 127a woofer for an L40.

[johnaec]

In terms of vertical centering, I don't think it will make much difference, though I see how it could conceivably make a little, but would be so small as to be almost insignificant. I'd be much more concerned that it's centered horizontally. Are you sue the spider is securely glued down at the outside edges?

It sounds like one of them may have been reconed at some time, with the age difference accounting for the difference in compliance?

John

[brutal]

A proper surround kit will come with a 30HZ test tone CD and instructions to properly align everything by using the tone while the glue on the outer surround edge sets up.

If you search the forums, you may find a location to download the test tone.

[dllyons]

A proper surround kit will come with a 30HZ test tone CD and instructions to properly align everything by using the tone while the glue on the outer surround edge sets up.

If you search the forums, you may find a location to download the test tone.

Yeah, I had heard about this guy on eBay that sells surrounds and includes the 30hz test tone. I had already bought these kits. Damned .... would have been nice to have one .... so you're saying you run the tone as the glue is still wet ? gutsy .... but sounds good. Gotta find one ............. :blink:

[dllyons]

Ok, I went out on the 'net and downloaded a bunch of test tones (isn't the 'net great ?) . They were only 10 seconds long, but fortunately I have a .WAV editor and I extended them to 2 minute long tones, so I'm ready to do this .... scared but ready. Any advice now ?

[Mr. Widget]

I'd be much more concerned that it's centered horizontally.I'd be more concerned that the spider on that one woofer is shot... with a worn spider the driver will never sound quite right.


Widget

[johnaec]

I'd be more concerned that the spider on that one woofer is shot... with a worn spider the driver will never sound quite right.Well, yeah, but I've never seen a surround so shot that it affected the compliance noticeably. That's just my personal experience - I suppose there's always a first time...

John

[dllyons]

that's what's in the back of my mind ..... the one cone needs replaced. :(

I learned something today - even though I thought I had rebuilt the other 3 surrounds perfectly without using a test tone ... I found one rattling. :banghead:

By playing the test tone, and then by exerting just a little pressure on one spot of the surround, the rattling ceased. I suppose that's telling me that I didn't get it centered as well as I thought ?

What I don't understand is, I can press down directly on the center of the cone until the cone bottoms out, and not detect any rubbing whatsoever, but the 30 and especially the 40 hz tone test reveal a rattle. CRAP !!

I'll probably need to get all new surrounds, because I'll bet I'm not too successful getting these unglued. Do you think ?

I have learned a lesson in speaker repair. I must have just been darned lucky on the others I've done, including my L300's. No rattling detected on those with the tone tests, but lots of wall and other crap rattling ;)

[speakerdave]

Well, yeah, but I've never seen a surround so shot that it affected the compliance noticeably. That's just my personal experience - I suppose there's always a first time...

John

I have. A woofer that has dangled at a angle for an extensive period will torque the spider, leading, I believe, to non-linearities in travel.

David

[John]

What I don't understand is, I can press down directly on the center of the cone until the cone bottoms out, and not detect any rubbing whatsoever

I would advise you not to do that in the future. Not good when the amp does it, and not any better when hands do it!!!

[macaroonie]

Read through this - it has some relevent comments.
http://www.troelsgravesen.dk/JBL-L26.htm

Best of luck

[dllyons]

I would advise you not to do that in the future. Not good when the amp does it, and not any better when hands do it!!!

I was very careful to press down with one finger directly in the middle of the dustcap. I'm not so foolish to press it down off center. But still, it's not something I felt comfortable doing.
The only reason I did it was because I noticed the woofer's excursions playing the test tones were longer than I had tested previously. I actually wondered if the woofer was bottoming out, but it really wasn't close.

[dllyons]

Read through this - it has some relevent comments.
http://www.troelsgravesen.dk/JBL-L26.htm

Best of luck

Macaroonie - very interesting reading ! thanks for sharing that.

[LRBacon]

that's what's in the back of my mind ..... the one cone needs replaced. :(

I learned something today - even though I thought I had rebuilt the other 3 surrounds perfectly without using a test tone ... I found one rattling. :banghead:

By playing the test tone, and then by exerting just a little pressure on one spot of the surround, the rattling ceased. I suppose that's telling me that I didn't get it centered as well as I thought ?

What I don't understand is, I can press down directly on the center of the cone until the cone bottoms out, and not detect any rubbing whatsoever, but the 30 and especially the 40 hz tone test reveal a rattle. CRAP !!

I'll probably need to get all new surrounds, because I'll bet I'm not too successful getting these unglued. Do you think ?

I have learned a lesson in speaker repair. I must have just been darned lucky on the others I've done, including my L300's. No rattling detected on those with the tone tests, but lots of wall and other crap rattling ;)

Dave, that rattling you hear just might be a small section of the surround that is not completely glued to the cone.
Check the surround all the way around the cone. I had that problem on a pair of LE111H's that I did here recently.

Larry

[dllyons]

Well, I haven't determined what the rattling is yet in the 125a woofer that I had fixed the surround on.

I'm happy to report that the scary looking 127a woofer that had the semi-flimsy spider on it (compared to the others) is alive and doing fine after I installed the new surround ! and it's thanks to you guys who suggested using the low freq. tones to help center the cones while gluing the surrounds down to the frame. :applaud: That was very slick procedure, although I don't know if I did it by the book, it still came out just fine though.

I'll bet I'll have to re-do the 125a mentioned above. I wonder if I'll be able to get the glue off around the frame, or will I have to just replace the whole surround.

[boputnam]

I learned something today - even though I thought I had rebuilt the other 3 surrounds perfectly without using a test tone ... I found one rattling. :banghead:

By playing the test tone, and then by exerting just a little pressure on one spot of the surround, the rattling ceased. I suppose that's telling me that I didn't get it centered as well as I thought ? 'zactly.


...so you're saying you run the tone as the glue is still wet ? 'zactly.

There has been some extensive posting on this in the Resurround Step-by-Step Thread, even sources for finding a 30Hz tone if you don't have the CD or a tone generator.