Another bad refoam? (L100T)

[DanMan]

So with all this talk about bad refoams lately... :blah:

Is the attached yet another case of a bad refoam??

I had this done at the local JBL Authorized Service Center, um, so it should be correct. This was done long time ago (maybe 8 years or so).

Should I be :banghead: that the local authorized shop did me wrong on this ?!?

[SEAWOLF97]

the foam IS on the front of the cone and I cant tell if there is no gasket around the frame or if the foam is on top like the L65. ?

[mech986]

The surround foam pictured is mounted on the front. The grey neoprene like trim is just discernable from the grey surround so it does look like the surround is correctly glued to the frame and the trim glued on top of the surround.

IMHO, since JBL does not specify or give a procedure for refoaming (only reconing is JBL condoned), the refoamers, maybe even the JBL Authorized shops that do refoaming, seem to be on their own. Some, like OCS, have said there isn't any difference, ITO, and it is easier and faster to do, so the shops may have an incentive (or ignorance) to do it that way.

However, like Edgewound mentioned in the L65 thread, the concientious technician will do the refoam to look exactly factory (hopefully that also includes the right dustcap if shimming and putting them on in a similarly correct orientation (convex vs concave) if the driver had it that way.

Really, everything seems to boil down to how fast, how easy, etc. vs. correct and whether people will charge/pay for that level of service.

Regards,

Bart

[DanMan]

but indeed the foam is on the correct side of the gasket... im not that much of a (where the idiot smiley icon) LOL.

i'll attach more pics to ascertain...

i have to be honest and say I didn't know the foam should be on the back of the woofer... (gaskets another thing altogether)

but regardless, this was done by the local JBL authorized shop, and it is indeed IMHO that they should do things right regardless. thats why i take things to the pros, oh man, im starting to :biting:

[SEAWOLF97]

for me , it is much easier to put the foam on the back , where it belongs....takes what ? 5 seconds more ? Also allows me to use more glue without the fear of getting messy on the front of the cone. cant understand why anyone wud consider it more difficult ?

If you look at it ...foam on the back supports the cone during movement while foam on the face has the cone trying to pull away from it.

[DanMan]

I guess my question "Should I be :banghead: that the local authorized shop did me wrong on this ?!?" is more on an ethical/moral basis and :blah: we could discuss that forever...


I just did a search on JBL's site for authorized service centers in Austin, and the place that was (and did these), is no longer, listed there :applaud: .

Man I hate shoddy work, but I still feel bad for applauding.

[SEAWOLF97]

I guess my question "Should I be :banghead: that the local authorized shop did me wrong on this ?!?" is more on an ethical/moral basis and :blah: we could discuss that forever...


I just did a search on JBL's site for authorized service centers in Austin, and the place that was (and did these), is no longer, listed there :applaud: .

Man I hate shoddy work, but I still feel bad for applauding.

We all on this forum seem to agree on the orientation of the foam, BUT not everyone outside the forum agrees on this. Shoddy , unethical , immoral ?? probably not. You wouldnt win that one in court.
Not to our collective way of thinking ? For sure . YES.

The LFs do work either way, and I dont think anyone could tell in a blind A/B test.

[macaroonie]

Tidy for a bad job though :p

[DanMan]

can anyone explain how all that dust accumulated on the top half of the woofer? (:confused:) i would have expected it all to settle to the bottom half? quite embarassing, i've called in the french maid brigade ...!

[SEAWOLF97]

can anyone explain how all that dust accumulated on the top half of the woofer? (:confused:) i would have expected it all to settle to the bottom half? quite embarassing, i've called in the french maid brigade ...!

I would bet that the woofer was rotated when refoamed.

[GordonW]

It's just unprofessional. No other way of putting it. Anyone, under normal circumstances (ie, dealing with an unmolested original woofer) who would install a surround like that, has NO right to call themselves a competent professional.

As for time/cost? A measly FIVE BUCKS would EASILY cover the additional time (if ANY) to do the job RIGHT. Is anyone SERIOUSLY contending that FIVE BUCKS per woofer would dissuade someone from having the job done the RIGHT way?

Heck, I don't even charge differently... I see no need to. A 2214H is an EASY refoam, compared to some...

Regards,
Gordon.

[pelly3s]

im with gordon on this its not a difficult thing to do, i dont ever charge extra for having to refoam on the back side of the woofer. if thats the way it came from the factory thats the way it should be done.

[Tim Rinkerman]

Just to be the devil's advocate here....sometimes the foam from the surround left on the back of the cone can be very hard to completely remove, especially a small diameter woofer such as yours. And if you don't get all of it off, the new surround will not seat nicely against the back of the cone,looking far worse in the long run. Your technician might have weighed the difference between possibly doing more damage to the cone by trying to remove all the foam, and doing a neat job of putting it on the front, putting the cone through far less trauma. As long as it is bonded securely and neatly, I really don't think there is any difference between the front or back.

[edgewound]

Just to be the devil's advocate here....sometimes the foam from the surround left on the back of the cone can be very hard to completely remove, especially a small diameter woofer such as yours. And if you don't get all of it off, the new surround will not seat nicely against the back of the cone,looking far worse in the long run. Your technician might have weighed the difference between possibly doing more damage to the cone by trying to remove all the foam, and doing a neat job of putting it on the front, putting the cone through far less trauma. As long as it is bonded securely and neatly, I really don't think there is any difference between the front or back.

Bullshit!!!!

The technician that does it that way is looking to cut corners. There is no excuse.

[grumpy]

LE10A refoam (lansalloy surround) was the only set I've had to spend much time on
to get the old "foam" off of the cone... it's a much narrower surround than the 2214's
I did and even the lansalloy wasn't really -that- much of a problem (other than with my
patience). That said, it's not something I'd recommend just anyone to do on their own
and there certainly are people out there who are willing to short-cut the effort required.

-grumpy

[kingjames]

I am quite interested in this topic more so because I bought those L-65's 2 weeks ago that have the foam on the speaker front.

I have googled proper ways to refoam and every single shop that I went to on-line every single shop put the foam on the front of the speaker with some shops saying it made no difference.

I'm not trying to second guess anyone here but if JBL doesn't recommend re-foaming then I have to ask who came up with the idea of putting it on the back of the speaker? Is this where Jbl puts there foam and everyone assume's that is the way it should be? I can understand that, put it back the way it was.

Now,is there scientific proof that foam put on the front of the cone is not good? I know there are quite a few experts here and I am not second guessing your expertise but a liitle proof would go a long way on this topic.

Since there is no word from JBL on this subject then all we have are opinions on this . Maybe this is an item for the Zilchlabs.

What is the difference,does it sound different,does this cause the voice coil to rub,does it not take the same volume, what?

Why is it so important to put it on the rear of the cone?Cosmetically I think it looks good or the same as if it were put on the back.

[Titanium Dome]

I am quite interested in this topic more so because I bought those L-65's 2 weeks ago that have the foam on the speaker front.

I have googled proper ways to refoam and every single shop that I went to on-line every single shop put the foam on the front of the speaker with some shops saying it made no difference.

I'm not trying to second guess anyone here but if JBL doesn't recommend re-foaming then I have to ask who came up with the idea of putting it on the back of the speaker? Is this where Jbl puts there foam and everyone assume's that is the way it should be? I can understand that, put it back the way it was.

Now,is there scientific proof that foam put on the front of the cone is not good? I know there are quite a few experts here and I am not second guessing your expertise but a liitle proof would go a long way on this topic.

Since there is no word from JBL on this subject then all we have are opinions on this . Maybe this is an item for the Zilchlabs.

What is the difference,does it sound different,does this cause the voice coil to rub,does it not take the same volume, what?

Why is it so important to put it on the rear of the cone?Cosmetically I think it looks good or the same as if it were put on the back.

Wow, you're a risk taker, aren't you? I think there's a lot of passion on this subject.

Frankly I'd be more concerned about the foam surrounds having the right compliance and the correct roll (shape) in the foam. I've seen a few foam surrounds that had an obviously wrong roll (too shallow or too pronounced) that I would think would put the driver into a worse position that the small amount of offset produced by front rather than back mounting using a correct surround.

Still, it is good practice to put things back the way they're supposed to be. However, if we followed that logically, we'd do as JBL tells us and only recone, never refoam.

[grumpy]

...I'm not trying to second guess anyone here but if JBL doesn't recommend re-foaming then I have to ask who came up with the idea of putting it on the back of the speaker?...

...that would be the designer of the transducer.
Note that some drivers are designed to have the surround attached to the front of the cone.

If you're worried about the sound, do a comparison vs. a fresh driver or recone...
with measurements would be even better, including 2nd & 3rd harmonics.
Note that for some drivers, there may very well be no significant audible difference.

If you're attempting a "restoration", putting the foam on a different side than the original
seems an odd notion to me... if you're worried about the resale value, "original"
almost always brings in more.

Also please note that there are threads like this ad nauseaum here that -do- go into
more detail regarding offsets, gap depths, coil length, blah, blah, blah.

It's not hard to do it as-designed, so -if you have the choice- why do it any other
way? If that's not the cards you were dealt and you're not up for a recone, then you
can either choose to enjoy the speakers, as they are (which I've done with one pair),
sell 'em (knowing better next time), or shorten your life worrying about it.

Sorry if I didn't actually prove anything... it would be lovely for argument's sake, but
I'm really not hung up on this topic. -grumpy

[kingjames]

Like I said TI, I am not second guessing anyone here and all I want is some concrete proof on why it should be done this way.I honestly don't know the correct procedure and in the past have only gone by what the expert's here say.

I don't like graph's and such but maybe one should be used here if possible to show us dummies that there is a consequence for putting it on the front.

[Chazmatic]

I agree with putting the surround on the inside of the woofers and passives. I just did a pair of the 150's. (first time surrouding anything). It was very easy. The surrounds seat better than on the outside. They stay in place as your applying the glue. Next: L112's. Chazz.

[Titanium Dome]

I agree with putting the surround on the inside of the woofers and passives. I just did a pair of the 150's. (first time surrouding anything). It was very easy. The surrounds seat better than on the outside. They stay in place as your applying the glue. Next: L112's. Chazz.

Congrats! If you're not too shy, show us a picture.

[kingjames]

I agree with putting the surround on the inside of the woofers and passives. I just did a pair of the 150's. (first time surrouding anything). It was very easy. The surrounds seat better than on the outside. They stay in place as your applying the glue. Next: L112's. Chazz.

Ok, now we know it's easier that way but it doesn't answer my question. Is there a test that will show that there is a difference in sound or is it just cosmetic?

[Zilch]

Is there a test that will show that there is a difference in sound or is it just cosmetic?Unlikely, and I'm not taking it on.

I guess we should all be thankful that OCS (and other feckwits) have developed a new "standard" for resurrounding opposite of factory spec. It's thus easy to tell which cones have been refoamed with indeterminate performance and provenance.

I prefer to buy drivers with rotted foam. I have no way of knowing if my reconer uses surrounds that match original spec in all cases, but he DOES install them mechanically according to factory standard....

[kingjames]

I'm done with this.

[Maron Horonzakz]

Whether your job is large or small, do it well or not at all.;)

[DanMan]

. if thats the way it came from the factory thats the way it should be done.

Amen to that :applaud: ! Thats actually the reason I take (took) my drivers to the FACTORY AUTHORIZED service center - I expected that they would be restored to within factory-authorized specifications.


...that would be the designer of the transducer.
Note that some drivers are designed to have the surround attached to the front of the cone.

Also please note that there are threads like this ad nauseaum here that -do- go into more detail regarding offsets, gap depths, coil length, blah, blah, blah.
. -grumpy

Well regarding offsets, gap depths, coil length, excursions... what else does a woofer really do? Seems like it just needs to move from point A to point B as the designer intended it to (no small feat). Any modification to that movement IMHO will doubtly make the driver perform "better" but more likely limit the intended movement in some negative way. (as long as the cone is out .... why not wrap some more edgewound copper around the coil... oh crap did i just say that out loud... )

Here's a cross-sectional view of another JBL driver where the surround (in this case nitrile-butylene rubber) was engineered by the transducer designer to be placed on the front of the cone. I've drawn in red what IMHO what happen if it were placed on the incorrect side. Seems like the surround "may" be stretched beyond the original intended limits <?>, which could effect the sound, or it could push the cone to a different location than the original intended location of the driver by at least the width of the cone <?>. I just dont see how modifying the driver in this way could produce any positive results for the overall performance of the speaker. Maybe the onus should be on the people who do it incorrectly to prove that it makes the speaker better???




Whether your job is large or small, do it well or not at all.;)

Rock on to that quote! :applaud:

[edgewound]

Nice illustration,:applaud: Dan...that took some thought.

[kingjames]

Thanks Dan, that is what I was looking for.People here assume everyone should have the same knowledge on this. I prefer to see evidence since this is not accepted by JBL.

Without clear instructions from Jbl on this issue then I wanted to know why it was put on the back and if it was put on the front in error what effect would it have on the cone movement.

It appears this is something that I should have known and by some of the reply's something I shouldn't have asked.

Well gentleman, I wanted to know why this is done this way since there's no input from JBL on this issue.

With 10 shops out of 10 shops that I seen on the internet saying the re-foam can go on either side with no difference is why I chose to ask this question.

What about the people who don't know about this site that send their speakers to one of these shops? They won't know that their foam was just put on the wrong side and,the proof of this can be seen in all the ebay listing's with foam on the wrong side and the sellers not even knowing it to be an issue.

Try to remember that stupid questions in your eyes are not so stupid to everyone else who doesn't have this simple knowledge.

[grumpy]

Nice illustration,:applaud: DanIndeed. If one can imagine this illustration with the cone at rest and surround on the
alternate side, you might also imagine a small amount of assymetry that would be present
regarding the forces on the suspension. This typically translates to increased harmonic
distortion... no matter how small the signal/displacement. It is also something the
transducer designers go to great lengths to minimize and go on about in white papers. :)

-grumpy

Edit: If I've made anyone feel stupid... that was not my intent. There have been -many- conversations
here about this very topic (or topics: surround repairs -and- feeling stupid or minimalized), and I
guarantee there will be more.

[DanMan]

it was JBL's illustration, I just did a little mark up to help visualize, which sometimes helps me to understand whats going on...

however, with JBL speakers, you typically can't visually ascertain woofer movement before you can already feel the house shaking :D

here's another way-oversimplified way to look at the situation... if the woofers max peak-to-peak travel is 0.5 inches, and the cone is only 0.1 inches thick, then placing the surround on the other (incorrect) side of the cone has an error of 0.1 / 0.5 = 20%. So the job is only 20% incorrect :biting: .

Oversimplified for sure, and it surely doesnt amount to 20% distortion, but still... why accept anything less than 'professional' from a professional?

[Zilch]

So, the next time 10 out of 10 refoamers tell you the surrounds THEY use are made to go on the front, BUT can also go on the back, if you insist, without consequence, would be ignorant of the very fundamentals of their trade?

[Say it ain't so.... :banghead: ]

I am confident that designers of aftermarked surrounds for JBL drivers INTENTIONALLY designed them opposite of factory spec, and made all of the requisite adjustments, for the convenience of refoamers.... :p

[kingjames]

Zilch,these are not the fundamentals of my trade and that is why I asked the question,

I have read many threads on this forum about this before I posted this question but I saw no diapgrahms backing up this procedure, unless I missed them.

I wanted this information for my own edification so that I may understand fully a consequence if there was one on foaming the front of the speaker.

With the drawing's posted by Dan now I can see what the difference is and instead of checking those L65''s that I'll be getting in a week to see how the speaker's react to the foaming of the front I'll just have them re-foamed without checking.

It's amazing what a picture can do,I guess they say it speaks a thousand words,in this case it would have saved the same amount!:applaud:

[richluvsound]

my 4435's had new surrounds when i got them. The surrounds were put on the front. Is there any way they can be changed ? I think I know the answer to this one already. I'm just thinking what else I could do with a grand sterling. 2235 kits x 4 = :banghead:
Richard

[kingjames]

[Say it ain't so.... :banghead: ]

I am confident that designers of aftermarked surrounds for JBL drivers INTENTIONALLY designed them opposite of factory spec, and made all of the requisite adjustments, for the convenience of refoamers.... :p

I'm glad you find humor in my posting and, I'm sure your response will get you applause and I must say I didn't expect anything different from you.

Your motto should be this is Zilch from Zilchlabs who also happen's to be the God of Audio!

[DanMan]

... on the other (incorrect) side of the cone has an error of 0.1 / 0.5 = 20%. So the job is only 20% incorrect :biting: .



... just wanted to add that those numbers were my fuzzy logic :p

it would be nice to know what the total (partial?) harmonic distortion really is, when you modify a speaker beyond its designer's original intention. got me as this isn't really my trade either...

another way I look at it.. and not that any of us would ever drive our speakers with more power than was intended, but if it did happen, I wanna know that my speaker goes into failure mode the way that the original designer intended without worrying about how novice repositioning of speaker parts might adversly affect the speakers performance at its limits... (tearing off the surround, coils hitting metal parts, etc. etc.)

[kingjames]

my 4435's had new surrounds when i got them. The surrounds were put on the front. Is there any way they can be changed ? I think I know the answer to this one already. I'm just thinking what else I could do with a grand sterling. 2235 kits x 4 = :banghead:
Richard

This is what I'm talking about,people. He's asking a simple question from you God's of audio.Wonder why he's asking? Maybe he read this thread and realized his foams are on the wrong side. Wonder why he said eeks in the beginning,I'm sure it has nothing to do with the attitude's here.

Sorry to quote your reply,didn't want to put you on the spot.

[edgewound]

The surrounds were put on the front. Is there any way they can be changed ? Richard

The answer is a definitive maybe. It depends on what type of glue was used.

A rubber-based contact cement could be softened with acetone and worked off the cone. The back side probably needs a good cleaning too since the bonehead that did yours didn't prep the backside.

I'm pretty sure acetone will soften up a water-based glue too.

Or....if they sound ok to you now, just wait a few years till the current surrounds rot and then do a recone:D ;) ...provided the parts are still available from JBL.

[kingjames]

... just wanted to add that those numbers were my fuzzy logic :p

it would be nice to know what the total (partial?) harmonic distortion really is, when you modify a speaker beyond its designer's original intention. got me as this isn't really my trade either...

another way I look at it.. and not that any of us would ever drive our speakers with more power than was intended, but if it did happen, I wanna know that my speaker goes into failure mode the way that the original designer intended without worrying about how novice repositioning of speaker parts might adversly affect the speakers performance at its limits... (tearing off the surround, coils hitting metal parts, etc. etc.)

I asked this question not using your words but I was downright rejected.

I guess it's ok to swap speakers build cabinets and change crossover's out of spec but not a re-foam job.

[edgewound]

C'mon guys...don't start a fight over this.

Oh yeah....I'm passionate about doing the job right....we all should...because this sight is about preservation and restoration, just as one would a classic piece of furniture or a classic car...think Concourse restorations.

I had a heated debate on this subject when I first joined:

http://www.audioheritage.org/vbulletin/showpost.php?p=59358&postcount=13

Even when original parts aren't available, the true preserver tries to get it original by whatever means are available.

In the end, though....this should be for your own enjoyment.

kingjames....Zilch is a very generous and prolific poster here that also comes with a bit of sarcasm attached. I don't think he considers himself God of Audio...But he does do alot of hands on discovery that is useful to many DIY'ers.

It wouldn't do any good to the preservation of Lansings' heritage to do a half-assed job.

[Zilch]

I'm glad you find humor in my posting and, I'm sure your response will get you applause and I must say I didn't expect anything different from you.Don't know why you take this stuff personal, James.

My observation is directed at the sleezy practitioners of this aftermarket "art," approximately 100% of them, according to your findings.

However, it IS good to see you have now concluded that all of the folks here who gave you their best advice did NOT have their heads so far up their asses as you supposed....

[richluvsound]

thanks Edgewound,

acetone should work. It cleans paint brushes a treat too ! I'm very proud to belong this forum. People do their very best to provide me with the advice I seek.
Why spend all that money if I dont need to. £ 1000 is a lot bloody money. I will spend it if I have to though . I love these babies too much !

cheers , Richard

[kingjames]

[Say it ain't so.... :banghead: ]

I am confident that designers of aftermarked surrounds for JBL drivers INTENTIONALLY designed them opposite of factory spec, and made all of the requisite adjustments, for the convenience of refoamers.... :p

This is why I took this personal,what kind of answer is this? This is nothing more than sarcasm. I am not here for your amusement.

I thought I asked a legimate question which was two fold.

1.What is the proper way to re-foam?
2.What damage if any is incurred by a improperly re-foamed speaker?

I asked for this proof because JBL does not condone re-foaming and, I also asked maybe we can actually see what really happens when they are re-foamed wrong.

I normally take your guy's word as law but in this area I wanted a little more info.There are quite a few speakers out there that are re-foamed wrong and yet no one has complained about their sound and I wanted to know why this is.

I never stay mad more than 10 minutes,just ain't worth it.:applaud:

[kingjames]

However, it IS good to see you have now concluded that all of the folks here who gave you their best advice did NOT have their heads so far up their asses as you supposed....

What advice did you give Zlich, I must go back and read this thread,I must have missed it.

Where in this thread did I say your head was up your ass?

Being the Zichlabs and all, I thought maybe you would like to check out the difference's between the two foam jobs.

Who knows maybe it will perform better,can't ask JBL because they don't want you to re-foam.

Very rarely do I question anyone's expertise here and wanting proof of an opinion should be welcomed here after all people are more willing to accept graph's and gauge's as scientific fact.

With all the speakers that are re-foamed incorrectly I just thought this would be interesting to find out the effects on the cone. Sorry, I guess I was wrong.

[Zilch]

If I thought everyone else here were wrong, I might undertake adding to the knowledge base.... :p

[DanMan]

Who knows maybe it will perform better.

I struggled with this one too kingjames. Modifying the speaker in any way will either make it better, worse, or the same. A speaker in its simplest mechanical form is simply a piston. Modifying the location that the surround attaches to the piston is similar to putting a different cam in the engine of your car, or raising the head, or changing the crankshaft, or maybe all three <?> The odds that it will be the same are nearly zero, the odds that ( a non-speaker designer ) can improve the speaker by modifying it from its original design are slim, i'm going with the odds that it will negatively effect the characteristics of the driver.



Ok, Is there a test that will show that there is a difference in sound or is it just cosmetic?

Yes there is a test. My velodyne sub uses it, its called a "Digital High Gain Servo", which is basically an accelerometer which attaches to the cone, measuring the cone's actual location, sending that info to a microprocessor, compares it to the location its supposed to be, and in the velo's case actually makes real-time corrections to the cone's location, which is purported to decrease the distortion levels (in this case distortion being defined as the cone being in a different location than its supposed to be) (all of which IMHO degrade the quality of an analog signal... but anywho...)

I believe thats the test: "Is the cone in the correct place at the correct time?". IMHO anything you attached to the cone (spider & surround) that are not in the correct original location will place the cone at the incorrect location at any time. Like they say here, can you A/B comparison and hear the difference... ?? Maybe not, but again why take chances, especially if you're a professional paid to do the job correctly.

I attempted a similar test with my fubar'ed L65 woofer (http://audioheritage.org/vbulletin/showthread.php?t=15054&page=2&highlight=fubar) but really I just own a laser pointer and a slide rule, so I don't know what I really accomplished... The surround on that woofer is placed so incorrectly that it appears that it limits its possible movement in one direction, which is what I was trying to measure. But again, I dont recommend people attaching superfluous items to woofer cones... especially 9 volt batteries!~


... that there is a consequence for putting it on the front.

Well it appears that Austin's JBL authorized service center is no longer listed as one on JBL's website (even though the store still exists and lists themselves as a JBL authorized service center on their own website) I would hope the consequence of these "sleezy practitioners" is that they can no longer practice their non-professional sleeze on mine or others' JBL products.

And if "King of Sarcasm" has not been awarded here yet.. im throwing in my nomination... :bouncy:

[kingjames]

Dan man, to reserve Bandwidth I will not quote what you said but,what you say makes a lot of sense to me.Thanks for your explanation.:)

[Chazmatic]

I agree with putting the surround on the inside of the woofers and passives. I just did a pair of the 150's. (first time surrouding anything). It was very easy. The surrounds seat better than on the outside. They stay in place as your applying the glue. Next: L112's. Chazz. Check it out..

[grumpy]

Nice looking job, Chazz. -grumpy

[Zilch]

As SKILLED practioner who obviously gives a whit about the integrity of his speakers! :thmbsup:

[4313B]

Now, is there scientific proof that foam put on the front of the cone is not good?Yes. And JBL is including specs in newer Engineering Design Specification sheets to highlight coil position. Reference

2262H (http://audioheritage.org/vbulletin/showthread.php?t=11345)

2268H (http://audioheritage.org/vbulletin/showthread.php?t=11346)

Many newer JBL transducers have the surround attached to the front of the cone by design.

The various centers that practice attaching surrounds are probably correct in assuming that the average end user would never hear the difference in a majority of the cases. But we don't buy JBL loudspeakers because they are half-assed. We buy them because they are best-of-class at their price points. A re-surround done "wrong" is ignorant as opposed to malicious.

Obviously one would never refoam something like a 112/2108 or 2122 with the surround attached to the front of the cone since the coil is so short and position is especially critical.

Also note that an incorrectly refoamed JBL is nothing more than a core in certain markets.

http://www.klippel.de/

[richluvsound]

Hi Chazz,

great job on the surrounds. I have a pair of 150's here that need recones. Whould you happen to know if they are still avaliable from JBL ?

regards, Rich

[grumpy]

Thanks Giskard, I assume the bottom-right quadrant is a decomposition of distortion
effects, using klippel's swept-sine analysis (and the x-axis -could- be mapped to
frequency if one had info on the test setup ?). The suspension would appear to have
the largest component except perhaps at a few discrete frequencies.

even just the summary text for the application notes is interesting:

http://www.klippel.de/download/group.asp?group=35

-grumpy

[4313B]

It should be readily apparent why we don't do refoams except as a last resort when recone kits are no longer available. As we have stated since the beginning of this forum - the spiders wear out and that is why we recone JBL transducers as opposed to refoam them. Newer JBL transducers have significantly improved spider implementations and voice coil braking is designed to reduce wear and tear on spiders as well.

For the average consumer end user none of this probably matters much. Refoam, recone, whatever works for the individual.

[Chazmatic]

Hi Chazz,

great job on the surrounds. I have a pair of 150's here that need recones. Whould you happen to know if they are still avaliable from JBL ?

regards, Rich
Hello Rich, I bought mine from Simply Speakers out of Florida, USA. Email: www.simplyspeakers.com (http://www.simplyspeakers.com). I did shop around for the best one's I could find. These are very well made and the glue that comes with it sets up very quick. I did buy another surround kit from a company on ebay, I thought they were to thin and compared to Simply they were. It was like night and day difference. I'll be selling my 150's, I got a great deal on a pair of L166's and L112's which also have to be done. I bought them from a church. Chazz.

[kingjames]

I (http://www.I) bought them from a church. Chazz.

Ever notice how many pairs of JBL'S are bought from Church's? It would appear even God loves JBL!:applaud:

[johnaec]

Ever notice how many pairs of JBL'S are bought from Church's? It would appear even God loves JBL!:applaud:I just bought these from a church: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=170094018767&ssPageName=STRK:MEWN:IT&ih=007

(For the band.) :band:

John

[kingjames]

Thos look nice Johnaec, I never really got into the pro line though.