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JBL Dog
11-05-2003, 07:21 PM
Just got my 2235H's back from being reconed and I've always heard they need a certain amount of "break-in" time.

Any ideas how long that is? Also, does it require a test signal or is normal use fine?

:hmm:

TIA

:D

This message comes from JBL Dog :band:

boputnam
11-05-2003, 07:28 PM
I'm certain you'll get a "smarter" response from Giskard, but in the past, I believe he's advised something on the order of say, +48-hrs, continuous play, with normal source (i.e., music) and nominal/soft volume.

4313B
11-05-2003, 07:34 PM
That was for these goofy super-duper capacitors they sell nowadays Bo :)

You can run those 2235H's for a few hours at 20 Hz to get them softened up. I think it's 7 volts or 10 volts in at 20 Hz but I can't remember which. I'd have to look it up. Oh, and that's out of the enclosure too. If you wait for them to break in normally you'll be waiting a long time.

JBL Dog
11-05-2003, 07:39 PM
Originally posted by Giskard
That was for these goofy super-duper capacitors they sell nowadays Bo :)

You can run those 2235H's for a few hours at 20 Hz to get them softened up. I think it's 7 volts or 10 volts in at 20 Hz but I can't remember which.

How can I generate a 20hz signal? I don't have any test equipment or a signal generator, etc.

:hmm:

Can I, maybe, uh.... play some rap music laced with profanity for an hour or so and get the same result?

:D

This message comes from JBL Dog :band:

boputnam
11-05-2003, 07:42 PM
Originally posted by JBL Dog
How can I generate a 20hz signal? I don't have any test equipment or a signal generator, etc. I haven't tried this, but give it a look: http://www.esser.u-net.com/ttg.htm

And, gimme a minute, I've got something that Rick Cobb had suggested for centering cones on resurrounds. Be right back...

boputnam
11-05-2003, 07:50 PM
OK, a few Links from the trustworthy Rick Cobb, aka Mr. Surround, that he reports provide good source material for test tones:

http://users.swing.be/hdepra/home/P22/E-sounds.html

and,

http://www.audioease.com/Pages/Free/MATTMain.html (Mac compatible)

I've not tried these, but Rick has never steered me wrong... :thmbsup:

Daniel B
11-05-2003, 09:07 PM
Hey, Giskard…

I was just thinking back to a warning you posted awhile ago. When you break-in the drivers, what do you mount them on so the vents aren’t flat on the bench?

4313B
11-05-2003, 09:55 PM
I have a super high tech pair of 2x4's that I sit them on while they break in.

JeffW
11-05-2003, 09:59 PM
Hey! That 20Hz test clip doesn't work! I played it over my computer speakers and it was just silence.....:duck:

gyusher
11-06-2003, 02:23 AM
I have used pink noise at a level of 1 watt output for a 24 hour minimum. I would place the speakers face to face and throw a blanket over them and let them go. . .This was recomended to my by Paridigm once when I bought some of their speakers. . .I will say it does loosen things up or so I thought at the time. . .

Guido
11-06-2003, 03:32 AM
Originally posted by JeffW
Hey! That 20Hz test clip doesn't work! I played it over my computer speakers and it was just silence.....:duck:

Hey! We all hope that this is a joke. :bomb:

Guido
11-06-2003, 03:34 AM
Originally posted by Giskard
That was for these goofy super-duper capacitors they sell nowadays Bo :)

You can run those 2235H's for a few hours at 20 Hz to get them softened up. I think it's 7 volts or 10 volts in at 20 Hz but I can't remember which. I'd have to look it up. Oh, and that's out of the enclosure too. If you wait for them to break in normally you'll be waiting a long time.

You once posted 20Hz for 4 hours with 10 Volt.

Oh, and the driver should sit on the high tech pair of 2x4's for ventilation:D

4313B
11-06-2003, 06:58 AM
You got it Guido! :)

JeffW
11-06-2003, 07:00 AM
Originally posted by Guido
Hey! We all hope that this is a joke. :bomb:

Yes, a joke...I have my PC set up as a source for my entertainment center as well. I don't think my PC speakers have much frequency response at 20Hz... I could barely hear it if I turned it up pretty high.

I guess my :duck: didn't get the point across...:rolleyes:

boputnam
11-06-2003, 07:13 AM
Originally posted by JeffW
Hey! That 20Hz test clip doesn't work! I played it over my computer speakers and it was just silence.....:duck: Whoa... That's amazing! If a manufacturer, you could advertise they work to 20Hz (@ -120 dB)... :nutz:

[Yea, your :rotfl: did work great - pretty hilarious. Just that I was sleeping through it all.]

GordonW
11-06-2003, 11:11 PM
If I don't have a test CD handy, I just take the Telarc recording of Michael Murray on organ with the Atlanta Symphony, of the Poulenc Organ Concerto in G minor, and put it on repeat. 16 Hz pedal tones do the trick!! Just be careful to set the gain at the LOUD part before you walk away!! :duck: (oops, there went the cone flying thru the air...)

Regards,
Gordon.

Alex Lancaster
11-07-2003, 07:16 AM
Gordon:

You beat me to it, I was going to suggest the same but with the TELARC 1812, more range, set the volume just so it clips occassionally.

Alex.

Audiobeer
11-07-2003, 09:55 PM
Originally posted by JBL Dog
How can I generate a 20hz signal? I don't have any test equipment or a signal generator, etc.

:hmm:

Can I, maybe, uh.... play some rap music laced with profanity for an hour or so and get the same result?

:D

This message comes from JBL Dog :band:

Come by an get my old heathkit tube sine generator...... I could listen to it for hours.....

JBL Dog
11-07-2003, 10:47 PM
Originally posted by Audiobeer
Come by an get my old heathkit tube sine generator...... I could listen to it for hours.....

I'll be there in 15 minutes!

:p

This message comes from JBL Dog :band:

jtgyn
11-11-2003, 09:39 PM
G'Day,
I have just received my 2 x 2225's reconed as one each of 2234 and 2235 from the JBL agents.

The burn in procedure works fine for the 2234 but the 2235 makes a scuffing noise above 7.5V @ 20Hz.

Is 7 V the limit for a 2235H @ 20Hz?

Regards Scott

Oldmics
11-11-2003, 09:54 PM
One would need to know the amplifier gain before an answer could be formulated.But according to the specs 10 volts are used sweeping the freqs from 20-1200 for a dynamic test.Oldmics

jtgyn
11-11-2003, 10:09 PM
G'Day,
Sorry, I should be more specific.

The speaker is suspended on two bits of 6" x 2" and the voltage is measured across the speaker terminals.

After a bit more listening the sound is more like something is hitting internally... like a soft (dull) click...

Regards Scott

GordonW
11-11-2003, 10:47 PM
Jtgyn.. hate to be the purveyor of bad news, but to me, it sounds like there may be a fault in that 2235. I would be surprised, that if 7.5V (only about 7 watts at 8 ohms) at 20 Hz would be able to make a normally-operating 2235 flinch at all!

My guess, is that someone didn't quite get the voice coil aligned in the gap properly... either an insufficient shimming of the voice coil during assembly, or a premature removal of said shims, before everything had set up and cured thoroughly. :banghead: Either way, it'll probably be a replacement of the cone kit, unless someone gets REALLY lucky and is simply able to strip off and replace just the foam surround and re-align the cone in the process of gluing the new foam surround in...

Regards,
Gordon.

John
11-11-2003, 11:17 PM
It just might be a problem with a loose mass ring,but hey just take it back to the reconer and tell them to get there shit togeather. :mad:

Guido
11-12-2003, 10:21 AM
Originally posted by GordonW
My guess, is that someone didn't quite get the voice coil aligned in the gap properly... either an insufficient shimming of the voice coil during assembly, or a premature removal of said shims, before everything had set up and cured thoroughly. :banghead: Either way, it'll probably be a replacement of the cone kit, unless someone gets REALLY lucky and is simply able to strip off and replace just the foam surround and re-align the cone in the process of gluing the new foam surround in...

Regards,
Gordon.
YEP!
Right, I had the same problem and still wonder why this so called "experts" are unable to align a voice coil. IMO it's just sloppy work.:die:
Since this happened to me I do recones myself. The first recone I did was even better then "their" work.

Sorry:(

boputnam
11-12-2003, 11:43 AM
Originally posted by Guido
Since this happened to me I do recones myself. Bingo! Except JBL Pro has made it impossible to get their kits, so do what I do - get to know your reconer, and try and hang around their shop when they're shimming... :yes:

Guido
11-12-2003, 02:32 PM
Originally posted by boputnam
Bingo! Except JBL Pro has made it impossible to get their kits, so do what I do - get to know your reconer, and try and hang around their shop when they're shimming... :yes:

Bo,

what is thing that you do no longer get JBL Kit's?
Does this mean that it is forbidden for reconers to sell you kit's? I mean if the door direct from JBL is closed, can't you use backdoors?

jtgyn
11-12-2003, 10:29 PM
G'Day,
I was starting to get a bit cross that the re-cone was a dud and I thought I should just check everything again before taking it back.

Well.... I think I have found the problem.

Comparing the two drivers I noticed the voice coil braid on the 2235 driver was much longer than the 2234 and almost touching the spider without any voltage applied.

When I drove the 2234 to 10V @ 20Hz the braid was just missing the spider but the 2235 was hitting the spider at 7.5V.

The 2234 braid hits the spider at 12V @ 20Hz.

Hmmm, I checked the cone displacement and at 10V @ 20Hz it is approx .4" (Xmax) so my guess is than 10V is all it is going to take. (@ its resonant frequency in free air anyway)

So... does anyone have a copy of the JBL re-cone guide that will tell me the correct way to set the braid length?

B.T.W. the Fs for the drivers seem low... 2235H ~17Hz and the 2234H ~ 19.5Hz... is this normal?

Regards Scott

John
11-13-2003, 12:51 AM
The Fs on the 4x2235,s that i have come in at 18.4 - 19.0:)

4313B
11-13-2003, 05:39 AM
"B.T.W. the Fs for the drivers seem low... 2235H ~17Hz and the 2234H ~ 19.5Hz... is this normal?"

Did you measure the Fs before or after breaking them in?

boputnam
11-13-2003, 07:25 AM
Originally posted by Guido
Bo,
what is thing that you do no longer get JBL Kit's?
Does this mean that it is forbidden for reconers to sell you kit's? I mean if the door direct from JBL is closed, can't you use backdoors? Hey, Guido...

JBL Pro will not sell recone kits to us Pedestrians, no matter how long we've had a "relationship". They have, in the past year-or-so, halted sale of recone kits to Authorized JBL Repair businesses. And, if any of them onward sell, they could lose their access (read: JBL authority). So, the "backdoor" too, is closed. Bummer... :(

I guess I've done my last recone, and am relegated to doing resurrounds only, even though I can (and would...) recone most everything that cycles through my world.

boputnam
11-13-2003, 07:39 AM
Originally posted by jtgyn
Well.... I think I have found the problem. Hey, Scott...

Is there enough slack in the braid that you can tighten-it-up a bit? Can you de-solder the connection to the tang, push the braid further through and take-out some of the slack? Maybe just bending the tangs a bit will suffice. I'm in :duck: here, since I've not worked on the 2234 or 2235.

jtgyn
11-16-2003, 09:35 PM
G'Day,
Well do I feel like a goose... I just had to bend the binding post tabs up and all is well.... if the honk fits!

Thanks Bo. I was missing the obvious. (A personal trait of mine)

The Fs of the drivers has not changed much after the burn in.

2235 before 17Hz after 17.3Hz
2234 before 19.5Hz after 19.2Hz

I am going to borrow another function generator just to check the figures again.

Thanks & Regards Scott