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Author Topic: Lab12 Reliability - Ripped 4  (Read 9289 times)

Geri O'Neil

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Re: Lab12 Reliability - Ripped 4
« Reply #10 on: July 09, 2004, 06:29:59 pm »

Actually, it appears that YOU didn't read Al's post carefully, or at least missed the context. I'm pretty certain he was responding to the fellow that loaded the Kappa drivers into the Peavey cabinets and NOT your original post. From reading Al's posts over the years, I know he's pretty sharp. If I were you, I'd listen to him a little more carefully.

Respectfully,
Geri O
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thejesse

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Re: Lab12 Reliability - Ripped 4
« Reply #11 on: July 10, 2004, 08:36:50 pm »

so we have allso lost 4 in this verry same manner dont know what to think and the cheapest recone kit ii can finde is 75 a piece ouch this is starting to get old   jesse bruce
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Tim Padrick

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Re: Lab12 Reliability - Ripped 4
« Reply #12 on: July 12, 2004, 12:39:32 am »

It seems to me that:

If the flex leads can be broken owing to over excusrion, it's a design flaw.

If the voice coil former can be damaged owing to hitting the back plate, it's a design flaw.

If the cone or surround can be damaged owing to the strength of the drive motor, it's a design flaw.

The only thing that should ever be capable of damage in a properly designed loudspeaker is the voice coil, owing to being driven beyond it's power rating.

raj

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Re: Lab12 Reliability - Ripped 4
« Reply #13 on: July 12, 2004, 01:03:19 am »

I had heard of cloudburst but here I see cone burst
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RL

Too Tall (Curtis H. List)

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Re: Lab12 Reliability - Ripped 4
« Reply #14 on: July 12, 2004, 11:12:21 am »

TimmyP wrote on Mon, 12 July 2004 00:39

It seems to me that:


If the flex leads can be broken owing to over excusrion, it's a design flaw.

If the voice coil former can be damaged owing to hitting the back plate, it's a design flaw.

If the cone or surround can be damaged owing to the strength of the drive motor, it's a design flaw.



I disagree.
You could instead say that it is not idiot proof or totally bulletproof.
Your conditions above would seriously curtail the power of this motor and therefore its output capability.
   We want to use as powerful a motor as possible and leave as few restrictions as possible.
If we look at a race car you don't put in a tiny motor with a so little power that it can not hurt the drive train or blow itself up. We put in as powerful a motor as we can make (and still make sense for the purpose) and give the driver a RPM gauge letting him use the motor to its limit.
The limit here may be the strength of the glue, surround and cone material. That just means we need to use it within those limits, not replace the motor structure with something that has less power.

Where you are correct is that the surround and cone structure should fail before the leads run out of length and around the same time as you bottom out. It does seem that this is what is happening.
So far we have a problem with glue and that is been taken care of for the speakers coming off the line and is being covered by Eminence on a case by case basis for speakers in the field.





TimmyP wrote on Mon, 12 July 2004 00:39


The only thing that should ever be capable of damage in a properly designed loudspeaker is the voice coil, owing to being driven beyond it's power rating.


In a world where we have material with unlimited strength and durability this would be nice. Otherwise according to your guidelines if we have the best material available we should then cut down the motor strength till it can not hurt itself. Most of the Pro bass speakers out there are not designed that way. The products you see that are designed that way appear mostly in the home and MI market.
   "Yes, that's right, you can turn it all the way up to 10 and it won't break. Of course it sounds like garbage at 6, but it doesn't break." I've used enough gear like that through the years. It sounds like garbage at 25% of rated power and you only WISH it would blow up and put it out of your misery.
This design is a formula-1 race care, not a taxicab with a governor the driver can't get to.
For the LAB sub we need to determine its mechanical limits and properly filter and limit the input. This is less obvious with the LAB sub because it sounds good right up to the point where it starts to rip itself apart.
   As I said before we need to hold Eminence's feet to the fire on factory defects, which this glue issue seems to be, but this does not mean we can just turn it up till it breaks and call it their "design flaw".
   The tricky part here is what to do with failures that happen 1 year or two years down the road. Was it bad glue that fatigued or were we pushing it past its Xmax on a regular basis and it should have blown up the first night?

Respectfully,
Too Tall
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Too Tall
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Graeme Goodacre [Centauri

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Re: Lab12 Reliability - Ripped 4
« Reply #15 on: July 13, 2004, 05:39:25 am »

Hi, haven't built any Labs myself yet, but had been looking at it.  My Hornresp simulation of the LabSub would seem to suggest that Xmax can be reached at 50Hz and 33Hz with an 800W input signal (400W per speaker). Depending on program material etc, I would think a 1200W amp would be capable of easily over-excurting the drivers.  Running things so much on the edge would HAVE to compromise long term reliability.

Maybe 800W should be the recommended maximum input for the Lab ?

Cheers
Graeme
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Tom Herr

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Re: Lab12 Reliability - Ripped 4
« Reply #16 on: July 13, 2004, 03:29:07 pm »

800 Watts?  I have been hitting mine with 2400 watts per box for over a year now. No driver failures. To my knowledge non of the labhorns I have built have experienced driver failures. I do stress the importance of checking the access plates regularly. An air leak could shred a perfectly good set of drives.  I check mine just about everytime they roll out of the trailer. But I consider that part of system maintenance just like painting cabs, cases or cleaning connector ends, etc...   Just part of a days work.

Tom Herr
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Brad Litz

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Max Power
« Reply #17 on: July 13, 2004, 11:50:27 pm »

I think most high spl users want to push the drivers past the one way linear travel (Xmax) 13mm to the two way max displacement (Xmech) of 44mm on peaks. The analysis I have done indicates that in 4 box groups they should handle 2400 watt peaks if high pass filtered -3db at 30 hz with a steep roll-off.

Mechanical fatgue is a very non-linear process. Easing off 1 or 2 dB can be the the difference between early failures or long life if you are operating near Xmech.
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Graeme Goodacre [Centauri

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Re: Max Power
« Reply #18 on: July 14, 2004, 06:53:49 am »

Brad Litz wrote on Wed, 14 July 2004 13:50

I think most high spl users want to push the drivers past the one way linear travel (Xmax) 13mm to the two way max displacement (Xmech) of 44mm on peaks.


I thought one of the original design parameters of the LasSub was to achieve the highest quality sound from a DIY box, and operating outside Xmax isn't really doing anything for quality of sound.  If I want higher spl, I add more boxes.....

Cheers
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Too Tall (Curtis H. List)

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Re: Max Power
« Reply #19 on: July 14, 2004, 09:42:56 am »

Centauri wrote on Wed, 14 July 2004 06:53

Brad Litz wrote on Wed, 14 July 2004 13:50

I think most high spl users want to push the drivers past the one way linear travel (Xmax) 13mm to the two way max displacement (Xmech) of 44mm on peaks.


I thought one of the original design parameters of the LasSub was to achieve the highest quality sound from a DIY box, and operating outside Xmax isn't really doing anything for quality of sound.  If I want higher spl, I add more boxes.....

Cheers


Ah yes, the difference between what we say and what we do.  
The box was designed to be used in blocks of four and my guess is more then half the time they are used as singles or pairs.
As to your comment on quality just about everyone would agree in theory while they push the volume higher and higher (as long as it sounds good and the amp they use doesn't show solid clip).
In the end many do not have the money to build headroom into their system and quality components at a decent price works for them too.
   Such is our business.

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Too Tall
        Curtis H. List    
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Independent Live Sound Engineer (and I'm Tall Too!)
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