ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  
Pages: [1] 2  All   Go Down

Author Topic: Lunched ONE, now what  (Read 6166 times)

danfowler

  • Full Member
  • ***
  • Offline Offline
  • Posts: 129
Lunched ONE, now what
« on: May 25, 2004, 10:38:27 am »

Hi Everyone,

Last weekend I heard one LAB (one per side)thunk disturbingly. I immediately shut it down and grabbed another to finish out the night. I did the 9v battery thing and knew one driver was dead.
Took it apart today and this is the problem.

The windings have spooled off the VC. The other 12" is fine.
Obviously this one bottomed and was hot so the wire came off the bobbin.
They weren't being run hard,the amp(QSC 3002 bridged) was at -10 most of the first set. For this room I hi-pass the subs at 40hz (DBx 260) to keep it from getting boomy. Maybe this is a fatigue problem?
They've been in service for 15 months (out of warranty, of course) but it wouldn't be a honest warranty situation anyway.

Anybody else seen this?
Notice the rub marks on the inside of the VC. It was covered in dust as is the magnet pole piece. The exterior of the VC shows no damage or rub marks. The backing plate shows no visible damage from hitting it. Could it have been DC offset pulling the VC to the pole piece? I'm puzzled.

Gotta' get to reconing.
Dan O:)

index.php/fa/128/0/
Logged

John Sheerin

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
Re: Lunched ONE, now what
« Reply #1 on: May 25, 2004, 04:44:07 pm »

Hello,
First, I would like to point out that we have a 7 year warranty on our speakers, so I'm not sure why you think it is out of warranty.  This does not mean we will warranty it - you will have to send it in and let us look at it.  There's info about how to do this on our website.  It's also a good idea to not tear into the speaker if you want us to warranty it.

However, based on your picture, it appears that you bottomed the coil.  The wire commonly falls off the bottom of the coil when you bottom a speaker.  It's hard to say for sure since the pic's a bit out of focus on the coil, though.  However, power is not an issue here - the coil looks pristine.  If you were burning it up, the coil would be darker or even black.  Regarding the rubs, if that's what's on the right side of the inside of the coil, that is probably just from manufacturing.  If the coil was really rubbing, there would be very linear marks on the inside of the coil and corresponding marks on the opposing side on the wire (where it scraped the top plate).  However it is possible that there was a manufacturing defect.  Please send it in and let us look at it if you'd like to know.

John
Logged

danfowler

  • Full Member
  • ***
  • Offline Offline
  • Posts: 129
Re: Lunched ONE, now what
« Reply #2 on: May 25, 2004, 05:34:12 pm »

Hi John,

I talked to Parts Express (bought these there) about a recone kit. In talking to the tech me asked how old they were and I said 15 months. He said "well they're out of warranty anyway" so I let it go at that.

They have bottomed before. I think that's what all the black-ish dust is inside the gap, paint from the back plate and epoxy dust from the former. I can send this coil/cone to you but I know the bottoming took it out.

It probably was the VZ-3600 testing that was so miserable a failure with bottoming problems galore.

The glue you've used isn't an epoxy nor a CA. It scrapes off easily and is unaffected by MEK. What is that stuff?

Dan o:)
Logged

BrideofZen

  • Newbie
  • *
  • Offline Offline
  • Posts: 8
Re: Lunched ONE, now what
« Reply #3 on: May 25, 2004, 07:09:45 pm »

Dan,

John probably won't tell you.  It is a closely guarded secret.  I have worked with it myself and I still can't get a straight answer out of McJerry or Tom about it!

Jeff
Logged

danfowler

  • Full Member
  • ***
  • Offline Offline
  • Posts: 129
Re: Lunched ONE, now what
« Reply #4 on: May 25, 2004, 10:21:52 pm »

Hi Jeff,

It is good stuff. It's almost like a hot glue consistency but I know it must be an air cure (aerobic?) for the heat resistance.

It must not be solvent based since the MEK had no dissolving effect on it at all. Maybe it's a super latex?

I know I can use gel C.A. on the spider attachment. We did it all the time on car speakers between rounds at competitions.

The foam concerns me. I don't want to use anything detrimental to the foam or anything that would break it down (age it) prematurely.

Dan o
Logged

Sound Construction

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
Re: Lunched ONE, now what
« Reply #5 on: May 26, 2004, 01:04:44 am »

it sure is nice to see someone from eminence has an interest. this niche market driver can't be their biggest market.

John, are you from Eminance? are there readily available cone kits for the lab12? if so do they work like more like a JBL where you just plop it in the slot and glue it or more like an EV where you have to assemble the parts 1st?

Dan o, its looks pretty clear that you bottomed out, the question is why. is the suspension chamber that that driver sits in still air tight? It might help to epoxy all of the joints and corners in that chamber and probably the other one to be safe before you send another driver into service in that box.

the glue is probably like the stuff RCF uses. don't bother with MEK. use an exacto knife to get rid of as much of the spider and surround as you can and then use a dremmel with a course sandpaper drum. Keep a light touch with the dremmel though, once you get down to the metal you don't want to gouge it. The grinding sounds a bit brutish but thats the technique worked out after 100+ JBL and RCF recones with out failures. It would be nice to know at least what disolved the glue - ...John?
Logged

John Sheerin

  • Newbie
  • *
  • Offline Offline
  • Posts: 15
Re: Lunched ONE, now what
« Reply #6 on: May 26, 2004, 09:23:40 am »

Hi Dan,
Maybe the PE guy was referring to their warranty...  That would make more sense.  I think that's 45 days or something similar.

I'm not sure which glue you're asking about - there are 5 or more different glues used on that speaker...

To answer some other questions:
Our recone kits come with instructions including what kind of glue to use.  All the parts are separate, not assembled.  If you can't demag the speaker, make sure you cover up the voice coil gap before doing anything - you don't want any junk in there.

I would also add that it is perfectly possible to bottom out the speakers or otherwise tear them up - just run a single box in half space at 33hz with more than 1400 watts (64V) and you should be well on your way to needing recone kits!

John
Logged

danfowler

  • Full Member
  • ***
  • Offline Offline
  • Posts: 129
Re: Lunched ONE, now what
« Reply #7 on: May 26, 2004, 04:02:22 pm »

The glue line I'm referring to is the spider attachment to the frame and the outer surround (foam in this case)to the frame. These parts don't get that hot.

I use Loctite Black Max 380 at the coil-to-cone junction. That gets hot. This resists 250 degrees and is really tough. It is expensive though.

When a previous re-coner has gouged up the surfaces of the frame, or the glue is extremely stubborn (like on these), I've used a 5" orbital sander with 120 grit sandpaper to smooth out the spider attachment ring and the surround landing flange. A quick wipe with MEK, then aviation (self-etching)wash primer and it's ready for glue. Raw aluminum, I've found, makes for poor glue retention.

I think when these boxes are used with a single per side they are easy to over excursion. I just have to keep that in mind next time and clamp down a little more on the 260.

Later,
Dan O:)
Logged

Randy Smith

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 72
Re: Lunched ONE, now what
« Reply #8 on: May 26, 2004, 08:11:42 pm »

>>>Dan wrote:I think when these boxes are used with a single per >>>side they are easy to over excursion. I just have to keep >>>that in mind next time and clamp down a little more on the >>>>260.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >


Sorry to barge in here and change the subject. You hit on a subject I noticed the other day by accident. I was playing with my gear in the basement and was getting a huge frequency dip around 45Hz or so on left side sub. I got to checking and determined it was cancellation from low part of ceiling their.
Anyway on to the meat of this post.
When I put both side-by-side I noticed I could move the HPF lower, without bottoming the speaker, then I could with only one. I figured since you were talking about it there must really be something to what I was hearing.

Can anyone please explain to me the whys and how-comes of this?
also does it keep going the more speakers you add(Can you keep lowering the HPF with every speaker added)?

Logged

Tim Padrick

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 5008
Question for Mr. Sheerin
« Reply #9 on: May 27, 2004, 04:54:50 am »

John Sheerin wrote on Wed, 26 May 2004 08:23

I would also add that it is perfectly possible to bottom out the speakers or otherwise tear them up - just run a single box in half space at 33hz with more than 1400 watts (64V) and you should be well on your way to needing recone kits!

John


What voltage would you recommend as the setting for a brickwall limiter on a single box in half space?  And at what recommended high pass?  (For instance my 4 Ohm tops are rated 400w, and per the manufacturer's recommendation they are brickwalled at 35v.  My subs are 8 Ohms (ish), rated 800w (and noted for being conservatively rated) and are brickwalled at 80v.
Pages: [1] 2  All   Go Up
 

Page created in 0.111 seconds with 18 queries.