2235H distortion?

[Figge]

hello in the phorum!

k i have now tried and changed amp and the harsness in the room turned to silky smooth! guess it was the quads input sensitivity that was haunting me?

anyway now when i can really hear the music without blowing my brains out i noticed one of the 2235:s making a distorted (like something is loose) sound...at pretty high frequensies...for example: it is heard very clearly when playing piano and putting my ear infront of the woof. i pulled it to see whats up...couldnt see anythin´ strange though! it sounds like its coming from behind the dustcap.

what do me do? cut it open? buy new?

oh! i tried to pull it in and out by hand...=no scrape or rub sound, that means the coil is intact. right?

my first spontaneus guess was: that the massring is somewhat loose.

[Mr. Widget]

I doubt it is the mass ring, but that is a possibility. Try sweeping a tone generator to see what it sounds like from 100Hz to 1000Hz. A VC rub should become pretty obvious.


Widget

[Figge]

ok the distortion occurs at 630Hz and dissapears quickly above.


????

[Mr. Widget]

Try the same thing (at low power) with the woofer out of the cabinet. If it still occurs you have a sick woofer. If it goes away, there is something loose in the cabinet.

Alternatively you could swap woofers between left and right.

Widget

[Figge]

well the test is made with pulled woofer. any idea what it could be? it plays crystalclear up to 600 and beyond 700.

[Mr. Widget]

I have no idea, but I would recone it.:(

Widget

[Figge]

im pretty puzzled too... i would like to believe that if somethings wrong it would be heard over a much wider span...


my guess with the massring was due to old experiennses: i had a pair of infinity Qjr and some luxman reciever couple of years ago.

was having a party and the luxman was taken to its limit...it did well untill some fool went up to it and pulled the loudnes switch ( on the allready overdriving luxman). that blew out both mids completly and one (newly re-foamed) woofer started to sound REALLY bad...
i cut open the dustcap (the day after) and found somekinda massring, not made of steel but some soft heavy material looking like chewed chewing gum...it was totaly loose..so i glued it back...

oh! the (newly bought) diaphragms in the EMIT tweeters went too!:)

so did 2 fuses in the reciever! so much for music that night

[Figge]

has this happend to anyone else? distortion between 600-700Hz.

i find it quite strange!

[scott fitlin]

I have at times had problems such as this! Once with an Altec woofer, and what happened was the adhesive was undone due to heat and age, and part of the voice coil was loose, and it resonates at a certain frequency, and thats when you hear the problem!

Another time, I had this same problem with a JBL 2402 tweeter, it played fine, except with two records, then there was a raspy, buzzing sound! I thought I had a shattered diaphragm, but when I opened up the unit, half the voice coil was not attached to the former because the adhesive had let go! The diaphragm itself, and the voice coil were fine, and I installed a new phragm, no more problem! The date on the diaphragm I removed was Mar 06, 83! The date I removed this diaphragm was Dec 2002! Almost twenty years old! Never blew! Still worked, just the glue let go! It was the original diaphragm that I removed from when those tweeters were purchased. Its a good testament to the reliability of well built products!

If this is in fact whats happening with your woofer, recone it and youll have no more problems!

[GordonW]

I'm with Scott on this one- sounds like either a voice coil winding loose, or something has come unglued. That kind of narrow-band "sing-out" noise, is usually something that's partially come unglued. Check the spider to voice coil, spider to basket, surround to cone and basket, gasket to basket, terminals to basket... any joints where anything is bolted or glued together. Same goes for the cabinet! I just had a speaker of a different brand, that the PORT TUBE in the back of the box, would sing out at about 500 Hz! Only on ONE or TWO specific piano or synth notes in that range... but BOY, it would just ZING on those. Drivers were perfect, but the cabinet and port were effectively hosed... speaker going back to the mfr. for warranty.

Check all the glue joints, driver and cabinet... might be the thing...

Regards,
Gordon.

[Figge]

ok! found out what´s up....foam is gone...or more correctly put: startin´to go!

dammit! when i finnaly get it really ROCK!....well well refoamtime!

ok i refoamed a 116H 8" i can imagine this being harder to do on 15:s....

i maild mr.Cobb in hope he´ll help me out...


oh! :cheers:

[GordonW]

That'd do it! :banghead:

At least it isn't terminal! A new foam ring, and it should be back in business.

Regards,
Gordon.

[Figge]

unbelieveble! the foam looked very nice! and i got home another amp and pre-amp and the system needed high volume testing...all fine untill i crawled upp infront of the speaker to convince my self it didnt sound bad from the dustcap...i felt the air blow through the foam edges....so its safe to say the cone is missaligned now!

oh! and i pushed the system with vinyl also. and had the player on the floor (as i have no shelve for the stuff yet) was running the amp hard! then the player got feedback from the speakers! and poled the woofer several times...hope i didnt destroy the voice coil! it was after this i found out about the foam...



how do i tell when it´s time to change the foam before it breaks?

[Figge]

i refoamed them today. and it went very well. ricks kit was a perfect fit (as usual). however the distortion still remains!:( guess i damaged the VC when the turntable poled it....yippii recone time! damn!

[4313B]

Well hell...

[Oldmics]

Not too much of a market for used (but new) foam rings.

[Figge]

no it probably isnt worth a ratts ass! good thing though is that one of em became simply ecxelent!... and i know i cant send just one for recone.

im allso thinkin´ id get 2 brand new ones, and brand new diaphragms for the 2421:s aswell, just to "eliminate" all problems. but that "little" project would cost about as much as i paid for the speakers!


suggestions?

[Figge]

ok i called and talked to jbl service. and the guy recomended me to recone just the bad one since the other was good. does this make sense?

in my head u allwas do the same to both speakers.

should i do as the service guy says?

[Figge]

ok i found a single brandnew in box 2235H in an add...at a good price.(the same as jbl wanted to recone) so i bought it!

someone give a opinion on this!

one brand new and the other 2235 is probably 20 years old could this actually work out well?

[Figge]

ok!

i got the new 2235H it really is "new in box" never been mounted!

i know its the same but it didnt look like my old ones....who cares...as for now. "theres gonna be some rockin´" angus young....