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Guido
06-30-2003, 04:31 PM
Today I got my K140 reconed as 2235H. I started to break them in and one work perfect.
Unfortunately the other one makes some clicking noise. Its not loud and not really clicking. It's like fluttering with something touching the cone. Checked the wires, ok.
It seems to come out of the dust cap inside the voice coil. When I'm moving the cone there is no sound or scratching.

What the h... this could be?

Thanks for help

boputnam
06-30-2003, 04:43 PM
I started to break them in - how? Were you bench testing them outside of the cabinets?

It "sounds" like (sorry...) you might have a slight voice-coil rub from mis-alignment of the cone/spider assembly. "Fluttering" sounds like the sorrowful symptom.

If you have a tone generator or that handy BassZone Test CD (http://basszone.stryke.com/) select something in the 30 - 50 Hz range, and ease the signal into the driver on a bench, listening closely. You should hear nothing...

If you hear rubbing, you can try and very VERY gently apply asymmetric pressure moving around the cone and see if it worsens or disappears. If it disappears, I believe there is a problem in the voice coil positioning in the gap.

Good luck!

Guido
06-30-2003, 04:51 PM
Hi Bo!

Thanks for fast reply.

I did test them outside the cabs.

I will try to check the misalignment as you said tomorrow as it is 1AM here.

If there is that problem, what can I do. Can it be adjusted or is the cone for the waste bin?

Tom Loizeaux
06-30-2003, 05:12 PM
If there is a problem with the coil alignment, or any other re-cone problems, you should return the driver to the people who did you re-coning for a re-do!

Tom

boputnam
06-30-2003, 06:32 PM
Tom's right, I'm 'fraid, Guido. The spider and surrounds need be redone - that is, re-centered, and that will take a new recone kit

Bummer... Not so much the hassle, as the lost time! Ugh! You could possibly do the work yourself, if you can't find a good shop!

Guido
07-01-2003, 04:26 AM
Today I called the reconer.
We agreed that I send the speaker back. this means another 2 weeks waiting :mad:

I hope they will not make any problems because of the reconing from K140 to 2235H:rolleyes:

Thanks for your help guys!

JBL Dog
07-01-2003, 11:34 PM
Is it possible to salvage the cone and voice coil of Guido's 2235H kit if they have not been damaged? Just replace the spider, dustcap and surround? Ironically, I have a few 2235H's that have similar issues and my speaker guy (JBL authorized for over 20 years) says he can salvage the voice coil and cone if they are in good condition (both spiders are bad).

Thanks! :)

This message comes from JBL Dog :cool:

boputnam
07-02-2003, 06:21 PM
"salvage the voice coil and cone "


JBL Dog...

I've been thinking about your question off-and-on while travelling today, and you "could" salvage the cone and voice coil, but by taking the assembly apart you run the risk of increasing the chances of misalignment on reassembly :eek: - lots more pieces to align versus the JBL kits which are pre-assembled.

Alternatively, you could soften the glues (using MEK) on the spider and surround, and merely try and reposition the wrongly installed kit - this may be what Guido's shop may try and do. I guess I'd try that if it was the last recone kit around, and you could feel comfortable you could "convince" the cone/coil into proper position, but you better be listening hard for any misalignment, and be gentle. And don't be rude to the surround... ;)

GordonW
07-03-2003, 12:41 AM
JBLDog,

I"ve actually done the operation you mention, a few times, with JBL and other speakers... cutting out the dustcap, removing the assembly, applying a new spider and surround, and shimming/re-assembling the speaker.

It really depends on WHY the original installation of the kir was rubbing... if it was simply an original alignment flub, then yeah, this procedure will almost universally take care of problems. HOWEVER... if the voice coil was WARPED (which can be done, rough handling of the kit before assembly), then no amount of re-shimming and reassembly is gonna make it run clean.

A good reconer/rebuilder should have a good enough eye, to tell whether a kit is reusable... it takes some experience and feel... but if it's done with non-defective and non-damaged parts, this kind of rebuild can work...

Regards,
Gordon.
who just got thru doing this to a whole bunch of old EPI 8" woofers, due to having to re-glue loose magnets/pole pieces... got 'em ALL to work again!!

Guido
07-10-2003, 05:36 AM
Oh Oh!!
I did send the speaker back and they checked their work. Now they say the “fluttering” is caused from demagnetised basket.
Could this be the case???

JBL Dog
07-10-2003, 12:06 PM
Is that possible? I would seek a second opinion.

:confused:

This message comes from JBL Dog :cool:

boputnam
07-10-2003, 12:19 PM
I say, boooooo-gus ! :mad:
I agree with JBL Dog - that is nonsensical.

Your description was perfect for a misalignment. Just MHO!!

See if you can get a new JBL kit (maybe even through the shop giving this "advice") and do it yourself!

Guido
07-10-2003, 01:12 PM
Stooooop!!!!

Hey Guys! I let them recone the 2235H cones in a K140 Basket.

Alnico!

boputnam
07-10-2003, 01:25 PM
"I got my K140 reconed as 2235H"

Yea, I got that part, but then you got noise that "sounds" like coil rubbing. I don't know what Alnico has to do with coil rubbing, if that's what it is.

You have confused me, Guido... Help? :confused:

Guido
07-10-2003, 01:30 PM
Hello Bo!

No it's not coil rubbing. As I wrote before it's more like "fluttering".

Another interesting thing is when I close the vent on the backside of the magnet it's like breathing.
I think the defect speaker moves more than the other. When I partially close the vent it breathes more than the other and it makes slightly "fluttering" sound.

They say its demagnetized magnet. Could be possible as the baskets are bought used.

boputnam
07-10-2003, 01:53 PM
Hey, Guido...

Yea, I know. The "futtering" you describe is perfect for the sound I get on poorly aligned cones - but only when slightly mis-aligned. It can be very subtle, but needs be gone.

I wonder if covering the "vent" is merely reducing the cone movement, and reducing the "fluttering"... ?

Still "sounds" to me like one of those reconed K140's ain't quite right. And anyway, if the K140's are same vintage, and a pair - shouldn't they be the same?

If you can hear it, and it's mechanical (and not sound...), I'd say it ain't right.

Oh well... :)

GordonW
07-11-2003, 12:24 AM
Man, I'm in total agreement with JBLDog and Bo here. A partially demagnetized motor wouldn't do ANYTHING to cause a noise like that... especially if its occuring at relatively moderate power levels.

All the effect demagnetization will generally have is to make the speaker:

-less efficient (less motor strength)
-higher Q (lower, albeit boomier bass in box)
-less top-end (weaker motor, less acceleration, hence slower movement giving less upper-end response).

None of these things should make the speaker do something non-linear like rubbing, ticking or chafing sounds...

Regards,
Gordon.

MikeM
07-11-2003, 08:08 PM
Originally posted by Guido
Today I got my K140 reconed as 2235H. I started to break them in and one work perfect.
Unfortunately the other one makes some clicking noise. Its not loud and not really clicking. It's like fluttering with something touching the cone. Checked the wires, ok.
It seems to come out of the dust cap inside the voice coil. When I'm moving the cone there is no sound or scratching.

What the h... this could be?

Thanks for help

Sounds like a warped voice coil/cone kit. Also the magnet might be out of alignment. I bet its a bad cone kit. Take that driver back to them and have them replace the kit. Jbl will send them a new kit free. sometimes reconers try to spray a formulation on the voice coil former that will shrink it a bit so be careful and mark the old cone with something. Good luck. When they go playing around with swapping cones and frames thats asking for trouble. I bet that frame is out.

boputnam
07-11-2003, 09:49 PM
Great points, Mike.

Hey - if we can offer any help with your "Avatar", drop a pm - those 4350's (??) look worth seeing! :D

MikeM
07-11-2003, 10:54 PM
Originally posted by boputnam
Great points, Mike.

Hey - if we can offer any help with your "Avatar", drop a pm - those 4350's (??) look worth se

eing! :D

No the picture is in color thats as large as the system will accept. i shrunk it with "Paint". need to convert to BW. yep those are my 4350's.

boputnam
07-11-2003, 11:23 PM
Hey, Mike...

Go back to "Paint", open up the original pic, and save it as ".GIF", and say "yes" to the "Loss of color information OK?" dialogue box.

Then, if the file is still too large, use the "Image" / "stretch/skew" choice, and slowly, repeatedly step the image down (both horizontal and vertical IDENTICALLY% each time), and save each iteration, until the file size is acceptible.

Your ending Avatar will be substantially improved.

I have done my editing in a mediocre photo editing package, and get there by "resizing" the .jpb until right-sized (ie.e, small enough). Do not be discouraged if the image you see is kinda blocky (those are pixels) - at the reduced size of the Avatar, the blockiness blurs to resolution...

Maybe others out here have different ideas to offer ;) Lordy knows, there could be a bit more clues (like maximum file size!!) on the Avatar "Help". ;)

boputnam
07-12-2003, 08:38 AM
Hey, Mike...

I've been testing doing an Avatar in "Paint" :banghead: - it ain't easy because the image must be BOTH

<= 150x150 pixels
<= 20 kBytes

If you want, reply to this Post with a .jpg attachment of your photo reduced to <= 160,000 bytes. I'll snag it from your Post, and see if I can get an Avatar done for you. If so, I'll Post it and you can snag it from my Post. :cool:

Alternatively, email the original to: tesuque@comcast.net and I'll make a stab at it. :spin:

Don McRitchie
07-14-2003, 11:43 AM
it ain't easy because the image must be BOTH
<= 150x150 pixels
<= 20 kBytes

This is actually not hard to do. Just make sure that you are saving the picture in a "jpg" format and not a "gif" or "bmp". Jpg's are a compressed file format while gifs and bmps are uncompressed. My avatar is close to the maximum pixel size yet is only 3 kBytes. :dancin:

boputnam
07-14-2003, 11:56 AM
Don...

You are right - I toyed around with this over the weekend, and found that what you now post is right-on. :coolness:

I had tried the .GIF for reduced file size, but the results were not good. I then copied Tom's Avatar (being simply one of the cleanest and with best definition), and studying it, found his was a .jpg and only 4 kBytes, but the pixels were within the guidelines. Ah HA!

So, I next tackled the 150x150 pixel limit alone, without concerning myself of kBytes. I went back into Paint :banghead: and just kept "Image, Stretch/Skew"ing, reducing by identical % both the vertical and horizontal, and got both below 150, and produced a desireable result.

All this and Transducers, too! :spin:

Guido
07-17-2003, 12:33 AM
Today I did check the speaker in the cabinet. There was no fluttering except below approx. 28 Hz. But I think this is normal as the cab is tuned to 30 Hz and below the tuning frequency the woofer start to flutter. So the fluttering noise has gone when the speaker is mounted inside cab. Strange:confused:
Anyway, at the moment I’m searching for a magnetizer who is able to regauss such a big speaker. I think it could only be an advantage as I do not know what they did with my speakers before. Of course I will keep you informed.
I think demagnetising is not such a common task.
;)

boputnam
07-17-2003, 07:46 AM
There was no fluttering except below approx. 28 Hz. But I think this is normal as the cab is tuned to 30 Hz and below the tuning frequency the woofer start to flutter. So the fluttering noise has gone when the speaker is mounted inside cab. Strange
IMHO, greatest cone excursion will occur at low frequencies and when not mounted in a cabinet. When sitting on a bench, there is no air pressure resisting cone motion, and so is therefore the best for testing. And that is why the testing of woofers is so important at low Hz, and why one must be careful to avoid damage from excessive excursion on the bench.

It may be that the affects of your voice coil mis-alignment (if that in fact is what the issue is) is most (only...?) pronounced at the extremes of cone motion.

I don't think magnetization of the basket, or whatever you seek will resolve this low Hz "fluttering".

rehkop
07-17-2003, 01:26 PM
The problem could be caused by the lose 50 gr massring, which normally is glued inside the voice-coil with the 2235h. Cut off the dustcap and have a look. Use epoxy to reglue it.

Peter

Guido
07-17-2003, 03:15 PM
Thanks Peter,

but the massring is fixed!

It is demag or missalignment.

I will have regaussed it within the next weeks. If this is not working I will have them reconed from the JBL Shop.