Post by: danfowler on May 25, 2004, 10:38:27 AM
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:)
Post by: John Sheerin on May 25, 2004, 04:44:07 PM
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
Post by: danfowler on May 25, 2004, 05:34:12 PM
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:)
Post by: BrideofZen on May 25, 2004, 07:09:45 PM
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
Post by: danfowler on May 25, 2004, 10:21:52 PM
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
Post by: Sound Construction on May 26, 2004, 01:04:44 AM
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?
Post by: John Sheerin on May 26, 2004, 09:23:40 AM
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
Post by: danfowler on May 26, 2004, 04:02:22 PM
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:)
Post by: Randy Smith on May 26, 2004, 08:11:42 PM
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >
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)?
Post by: Tim Padrick 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.
Post by: Too Tall (Curtis H. List) on May 27, 2004, 11:13:44 AM
| John Sheerin wrote on Wed, 26 May 2004 09:23 |
Hi Dan, 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 |
Hi John,
Something we need to keep in mind is that compared to the typical front-loaded system this is much more complicated.
First and foremost we have a modular system where the safe operating limits change depending on how many and how they are stacked and located.
Next we have a DIY product where the majority of the boxes in use are being used in stacks of one or two instead of the four it was designed for.
Lastly the sneaky little bastards sound good as single boxes
Post by: Chris Hindle on May 27, 2004, 11:54:14 AM
also does it keep going the more speakers you add(Can you keep lowering the HPF with every speaker added)?
In a nutshell, with horn loaded subs, the more horns you put beside each other, the bigger the mouth gets. Bigger mouth supports lower frequencies.
The lowest note that the horn itself would support once you get 10 or 12 boxes together is <probably> lower than what each individual driver can take, so there is the law of diminishing returns to deal with, so don't throw out the HPF and sharp slope ! If you take the signal below where the box un-loads, it will get real quiet, real fast at the kind of power being thrown around these days.
On the old-standard W bins, 1 was useless. 2 was not much better. 3 worked, 4 was a bit better. 6 or more would flap the old pants legs. This was before subs.
Chris.
Post by: danfowler on May 28, 2004, 09:59:50 AM
It takes a while getting used to hearing the band out of context (all high end, the crow's nest is a bass nulifier)and I power the crap out of my boxes. Always have, probably always will. I lose fewer drivers to overpowering than to clipping. This is my first Lab 12" failure. Not bad for a 15 month run.
When I walked the floor at the beginning of the fist set it was readily apparent I had too much low end going. I was working on the kick and that Midas EQ is quick off center. I heard it slap, but it has slapped before without damage. Not this time.
I suppose I couldn't hear the magnitude of the slap at this club. Luckily, I shut it down before the other 12" got hurt.
The GOOD NEWS is LoudspeakersPlus got me a recone kit for about $40.00. Thanks guys. I had it reconed in under an hour and I'm back in the game. I could almost throw a kit, some CA and accelerator, and a scraper in my Tech box for field repair. But I'll just carry a spare driver instead. I have to say that using speaker clamps instead of TEE nuts/machine screws helps in changing out drivers. See pic.
I'm gonna set the limiter to let the amp just swing 50 volts and get a preset loaded on the 260 titled "1Lab/side".
Hope I've passed along some useful info to every one.
Thanks to everybody who posted. I love this place.
Slam on!
Dan o:)
Post by: Rick on May 28, 2004, 09:41:12 PM
Post by: danfowler on May 28, 2004, 10:38:17 PM
They hold very well. Some of the not-so-obvious reasons are:
They are the HD 1/4" thick Penn Fab versions
They've been countersunk to match the screw heads
The screw is 1/4"-20 and is 18.8 stainless (and non-magnetic)
The baffle board is VERY tight fitting to the driver frame so the speaker clamps just push the driver into that 1/2" recess.
You have to position the driver so the clamp lines up with a frame rib so it's grabbing the strongest part of the lip.
No problems so far. Very fast replacement. I have nightmares about pushed out or stripped 10-24 tee nuts; just as I'm putting the last one back in place................ AuygH @#$%^&*!
Sorry about the pics guys, I tried down sizing that thing before I uploaded it but I didn't hit some key I needed to.
Dan O:)
Post by: danfowler on June 02, 2004, 04:58:26 PM
Got the kit in from LoudspeakersPlus.
With the frame scraped and already cleaned it took less than a 1/2 hour to recone the LAB12 GII save for the latex adhered parts.
I used Loctite 380 on the spider to coil, spider to frame, coil to cone and surround to frame attachments. Insta-set accelerator moves that along fast
Regular latex speaker glue was used to attach the cork gasket to the surround lip, and bond the 2 inverted dust domes to the cone. The latex has to set up overnight to cure but about 1/2 an hour's work on the critical parts. FYI fellas.
Pretty easy to recone. The lead wires are crimped in the push post antennas so they're completely reuseable. No solder required. The most expensive part was the Loctite 380. I thought the kit itself was quite reasonable. Come to think of it, very little 380 was used so I guess it's not so bad. You can probably recone a dozen Labs from a single 1 oz. bottle.
When you order the kits, go ahead and buy 2 of them since shipping was about 25% of the cost of a single kit!
Later,
Dan o:)