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....]
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....
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!
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 =
Richard
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.Originally Posted by Zilch
[Say it ain't so....
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....
Your motto should be this is Zilch from Zilchlabs who also happen's to be the God of Audio!
... on the other (incorrect) side of the cone has an error of 0.1 / 0.5 = 20%. So the job is only 20% incorrect.
... just wanted to add that those numbers were my fuzzy logic
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.)
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.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 =
Richard
Sorry to quote your reply,didn't want to put you on the spot.
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
...provided the parts are still available from JBL.
Edgewound...JBL Pro Authorized...since 1988
Upland Loudspeaker Service, Upland, CA
I asked this question not using your words but I was downright rejected.... just wanted to add that those numbers were my fuzzy logic
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 guess it's ok to swap speakers build cabinets and change crossover's out of spec but not a re-foam job.
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/vbullet...8&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.
Edgewound...JBL Pro Authorized...since 1988
Upland Loudspeaker Service, Upland, CA
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....
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
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.
[Say it ain't so....
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....
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.
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.
If I thought everyone else here were wrong, I might undertake adding to the knowledge base....
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.
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/s...ighlight=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!~
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...
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