Page 1 of 2 12 LastLast
Results 1 to 15 of 30

Thread: JBL L-300 Summit woofer re-foam problem

  1. #1
    Junior Member
    Join Date
    Jul 2012
    Location
    Minnesota
    Posts
    13

    Unhappy JBL L-300 Summit woofer re-foam problem

    I just did a surround re-foam on my JBL Summit L300 woofers. I followed the sticky in the DIY forum using Rick Cobb's kit with the CD. It went well, and the speaker coils pretty much aligned themselves like the instructions said they would. I ran the tone at high volume (about 1/4 inch cone travel) until the glue was dry. They both sounded great, until I picked them up off the counter. One of them continued to sound great, but the other one started clicking like crazy. If I put it back on the counter, or cover the rear vent with my hand, it again sounds great.

    It doesn't seem to be a side clearance issue with the driver, it seems like the whole cone is bottoming out. When I hold the speaker completely vertical, or with the cone pointing slightly down, it sounds fine no mater how I spin it around it's axis. It does sound good up to about 60 watts in any orientation. Unfortunately, the L-300 speaker case front is NOT completely vertical, it tilts slightly back.

    It does appear that the cone sits slightly (very slightly) lower in the basket than the one that sounds good.

    Anyone have this problem before? I hate to have to re-cone the damn thing, but is that my only option?

    Thanks much,
    Keen

  2. #2
    Moderator hjames's Avatar
    Join Date
    Nov 2005
    Location
    NoVA - DC 'burbs
    Posts
    8,547
    Cone position is determined by the surround AND by the spider - maybe the spider on that woofer has sagged?

    Have you had these speakers since new or did you buy them elsewhere used?
    Maybe one of the woofers was replaced at some point and doesn't fully match (re: usage, not model info)

    No flames meant - just a thought ...


    Quote Originally Posted by keenyoung View Post
    I just did a surround re-foam on my JBL Summit L300 woofers. I followed the sticky in the DIY forum using Rick Cobb's kit with the CD. It went well, and the speaker coils pretty much aligned themselves like the instructions said they would. I ran the tone at high volume (about 1/4 inch cone travel) until the glue was dry. They both sounded great, until I picked them up off the counter. One of them continued to sound great, but the other one started clicking like crazy. If I put it back on the counter, or cover the rear vent with my hand, it again sounds great.

    It doesn't seem to be a side clearance issue with the driver, it seems like the whole cone is bottoming out. When I hold the speaker completely vertical, or with the cone pointing slightly down, it sounds fine no matter how I spin it around it's axis. It does sound good up to about 60 watts in any orientation. Unfortunately, the L-300 speaker case front is NOT completely vertical, it tilts slightly back.

    It does appear that the cone sits slightly (very slightly) lower in the basket than the one that sounds good.

    Anyone have this problem before? I hate to have to re-cone the damn thing, but is that my only option?

    Thanks much,
    Keen
    2ch: WiiM Pro; Topping E30 II DAC; Oppo, Acurus RL-11, Acurus A200, JBL Dynamics Project - Offline: L212-TwinStack, VonSchweikert VR-4
    7: TIVO, Oppo BDP103D, B&K, 2pr UREI 809A, TF600, JBL B460

  3. #3
    Dang. Amateur speakerdave's Avatar
    Join Date
    May 2003
    Location
    Northern California
    Posts
    3,734
    My guess is that your tone drive was excessive. You don't need that much to center the voice coil, which is an event of magnetics happening in the gap. The excessive travel was tugging on the new surround, and it may have pulled in a bit asymmetrically where the hold was not as strong as elsewhere. Or it may have pulled all around and the foam is in effect deflecting the spider (a really soft one). Or maybe the spider had sagged over time. I would try refoaming it, but I would first examine the spider carefully for tilt or pushup on one side. I've never done it, but I've heard said a hair dryer will soften a spider enough to help it remember it's true self. You would want to have a setup all ready to hold the cone in place while it cools. Very carefully identical pieces of stryofoam very carefully identically placed between the frame struts and the back of the cone may work. I suggest these heroic efforts because if those cones are the original 136a cones you will have to recone both of them if you do one.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  4. #4
    Junior Member
    Join Date
    Jul 2012
    Location
    Minnesota
    Posts
    13
    My father bought them new. They are one serial number apart. The woofer cones are definitely the same, and I know he never had work done on them. They have been sitting unused with rotted foam for probably 15 years, but they were working fine before that. They have been sitting in a basement with a fairly constant temp and humidity level. I'm not sure why one spider would sag and not the other, but I suppose it's possible. It is definitely the coil bottoming.

    Is there any way to determine the spider position without pulling the cone?

    Thanks,
    Keen


    Quote Originally Posted by hjames View Post
    Cone position is determined by the surround AND by the spider - maybe the spider on that woofer has sagged?

    Have you had these speakers since new or did you buy them elsewhere used?
    Maybe one of the woofers was replaced at some point and doesn't fully match (re: usage, not model info)

    No flames meant - just a thought ...

  5. #5
    Dang. Amateur speakerdave's Avatar
    Join Date
    May 2003
    Location
    Northern California
    Posts
    3,734
    Quote Originally Posted by keenyoung View Post
    My father bought them new. They are one serial number apart. The woofer cones are definitely the same, and I know he never had work done on them. They have been sitting unused with rotted foam for probably 15 years, but they were working fine before that. They have been sitting in a basement with a fairly constant temp and humidity level. I'm not sure why one spider would sag and not the other, but I suppose it's possible. It is definitely the coil bottoming.

    Is there any way to determine the spider position without pulling the cone?

    Thanks,
    Keen
    The spider should look level.

    The foam rotting may have been different on the two woofers, supporting one cone less than the other.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  6. #6
    Senior Member edgewound's Avatar
    Join Date
    Jun 2005
    Location
    Southern California
    Posts
    2,776
    Quote Originally Posted by keenyoung View Post
    My father bought them new. They are one serial number apart. The woofer cones are definitely the same, and I know he never had work done on them. They have been sitting unused with rotted foam for probably 15 years, but they were working fine before that. They have been sitting in a basement with a fairly constant temp and humidity level. I'm not sure why one spider would sag and not the other, but I suppose it's possible. It is definitely the coil bottoming.

    Is there any way to determine the spider position without pulling the cone?

    Thanks,
    Keen
    The spiders can sag due to age and use. The spiders used on the 136A is lighter than the spec' new recone kit C8R2235. It's possible to replace both the surround and spider but it's a tedious job. Some prefer this route to maintain the original voice coil length and spec as long as the original coil is in good shape...and save a couple hundred bucks in the process since the OEM kits are the major cost of a recone.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  7. #7
    Dang. Amateur speakerdave's Avatar
    Join Date
    May 2003
    Location
    Northern California
    Posts
    3,734
    It's going to take some fooling around, but I would try to save it. The exact equivalent cone kit is no longer available. My experience with the 4333a with original 2231's says that every effort should be made to restore the original cones. The 2235 replacement cone kit JBL specifies for this speaker is good, better in some ways, but it is a little different. You will have to do them both.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  8. #8
    Junior Member
    Join Date
    Jul 2012
    Location
    Minnesota
    Posts
    13

    Hairdryer trick?

    Darn. I ran at 1/4 inch cone travel because that was the upper limit suggested by Mr. Cobb, and I wanted to be damn sure to get it right. Live and learn, I guess.

    Hmm. Visually, the edge of the new foam has the same gap to the edge of the basket on both speakers, and they are both really centered on the basket. This and the fact that the coil is definitely bottoming on the case leads me to believe that the spider must have shifted.

    How would I inspect the spider without removing the cone? As for the hairdryer trick, are you suggesting doing this with the speaker sitting on the coil end, or upside down with the basket on the desk?

    I really don't want to recone the pair, but I know the new woofers are different.

    Thanks,
    Keen


    Quote Originally Posted by speakerdave View Post
    My guess is that your tone drive was excessive. You don't need that much to center the voice coil, which is an event of magnetics happening in the gap. The excessive travel was tugging on the new surround, and it may have pulled in a bit asymmetrically where the hold was not as strong as elsewhere. Or it may have pulled all around and the foam is in effect deflecting the spider (a really soft one). Or maybe the spider had sagged over time. I would try refoaming it, but I would first examine the spider carefully for tilt or pushup on one side. I've never done it, but I've heard said a hair dryer will soften a spider enough to help it remember it's true self. You would want to have a setup all ready to hold the cone in place while it cools. Very carefully identical pieces of stryofoam very carefully identically placed between the frame struts and the back of the cone may work. I suggest these heroic efforts because if those cones are the original 136a cones you will have to recone both of them if you do one.

  9. #9
    Dang. Amateur speakerdave's Avatar
    Join Date
    May 2003
    Location
    Northern California
    Posts
    3,734
    Hold the woofer up and look across the spider between the struts of the frame. It should not look dished or uneven.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  10. #10
    Member
    Join Date
    Oct 2011
    Location
    california
    Posts
    67
    just food for thought, have you checked the tinsel leads to make sure it's not slapping the cone or spider. I've had that happen by after removing the speaker, I grabbed the basket and didn't realize that I bent the lead close to the cone, but does make a slap/bottoming sound at volume. Good luck. TONY

  11. #11
    Dang. Amateur speakerdave's Avatar
    Join Date
    May 2003
    Location
    Northern California
    Posts
    3,734
    Quote Originally Posted by keenyoung View Post
    . . . . As for the hairdryer trick, are you suggesting doing this with the speaker . . . .
    I'm not suggesting any technique for this, because I haven't done it; I was just passing on a passing comment one of our members dropped in a post in the past. He may chime in here when he gets off work. It may be Custer's last stand, so I'm not recommending you try it until you get some more-experienced advice. Remember before anything gets wrecked, edgewound can replace the spider for you.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  12. #12
    Dang. Amateur speakerdave's Avatar
    Join Date
    May 2003
    Location
    Northern California
    Posts
    3,734
    Quote Originally Posted by keenyoung View Post
    Darn. I ran at 1/4 inch cone travel because that was the upper limit suggested by Mr. Cobb, and I wanted to be damn sure to get it right. Live and learn, I guess.

    Hmm. Visually, the edge of the new foam has the same gap to the edge of the basket on both speakers, and they are both really centered on the basket. This and the fact that the coil is definitely bottoming on the case leads me to believe that the spider must have shifted . . . .
    I perhaps a bit overstated the case. It was just one possibility. You likely didn't do anything wrong, but I do think 1/4 inch is way more than necessary. You just need to have the magnetic fields acting on each other to center the coil. Perhaps to a point more current is better, but I think not so much.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  13. #13
    Junior Member
    Join Date
    Jul 2012
    Location
    Minnesota
    Posts
    13

    Ok, you guys are good. It's spider sag.

    Tip of the hat to all who suggested spider sag. I can definitely see it cup down in the center. The spiders on both speakers do, but the rattling one is much more pronounced.

    So speakerdave, do you know the thread on this possible spider sag repair? Or perhaps the member name of the gentleman who commented on it?

    Many thanks,
    Keen


    Quote Originally Posted by speakerdave View Post
    I'm not suggesting any technique for this, because I haven't done it; I was just passing on a passing comment one of our members dropped in a post in the past. He may chime in here when he gets off work. It may be Custer's last stand, so I'm not recommending you try it until you get some more-experienced advice. Remember before anything gets wrecked, edgewound can replace the spider for you.

  14. #14
    Dang. Amateur speakerdave's Avatar
    Join Date
    May 2003
    Location
    Northern California
    Posts
    3,734
    Read this:

    http://www.audioheritage.org/vbullet...hed-in-speaker

    I have fairly decent manual skills, but there are things in that thread I wouldn't try.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  15. #15
    Junior Member
    Join Date
    Jul 2012
    Location
    Minnesota
    Posts
    13

    Spider Sag

    Yeah. I don't know about using MEK. I used that stuff to get the old glue off the baskets, and wound up dizzy even with good ventilation.

    I can't really afford a recone right now, so I will attempt the hair dryer first, and see how it goes. If that fails, I may try the MEK, but it would definitely be last resort before a recone.

    I'll report back when I get it done.

    Many thanks,
    Keen



    Quote Originally Posted by speakerdave View Post
    Read this:

    http://www.audioheritage.org/vbullet...hed-in-speaker

    I have fairly decent manual skills, but there are things in that thread I wouldn't try.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. 4412 woofer problem
    By mimo_proshol in forum Lansing Product Technical Help
    Replies: 8
    Last Post: 09-30-2011, 03:58 PM
  2. L96 woofer problem
    By infinityQ2 in forum Lansing Product Technical Help
    Replies: 6
    Last Post: 05-01-2009, 07:30 PM
  3. JBL 4312 problem with a woofer?
    By schwanncell in forum Lansing Product Technical Help
    Replies: 14
    Last Post: 11-08-2007, 01:35 AM
  4. Advice on problem with L36 125A woofer
    By Royd in forum Lansing Product Technical Help
    Replies: 1
    Last Post: 10-02-2003, 10:32 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •