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Author Topic: One of my lab cabs is creaking ?  (Read 5441 times)

Joe Jones

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Re: One of my lab cabs is creaking ?
« Reply #10 on: February 21, 2006, 09:19:48 am »

If the drivers were out of phase you'd get almost nothing from them. I'd test them out of the box, if there's a problem a 30Hz sine signal at 10 volts will point it out pretty quick. If it isn't the drivers then there's a leak in the box somewhere.
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Dave Rickard

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Re: One of my lab cabs is creaking ?
« Reply #11 on: February 21, 2006, 11:43:54 am »

Low tech question:

Have you swapped drivers?  Take the drivers (pair) from cabinet A and put them in cabinet B, and vice versa.  Did the problem move with the drivers or stay with the woodwork?

If the problem moved with the drivers, swap only 1 this time and track the problem.

Joe Jones' test is worth trying too.

Dave

Dave
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Dave
Yorkville dealer

"The wrong piece of gear, at the right price, is still the wrong piece of gear."

"If you don't have good stuff at each end of the signal chain, (mics and speakers) what you use in between is just turd polish."--Dave Dermont

Gary Perrett

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Re: One of my lab cabs is creaking ?
« Reply #12 on: February 21, 2006, 01:38:20 pm »

Is it possible one of the drivers is rattling against the cover plate?
I'd secure that mouth brace before doing anything else also.

P.S. those speakers have 2 dust caps, one under the other.

G
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Antone Atmarama Bajor

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Re: One of my lab cabs is creaking ?
« Reply #13 on: March 08, 2006, 02:46:08 pm »

I just posted about an issue I was having with binding posts having poor mechanical connection to coil lead tabs.  I don't think it will make your cabs creak.  But I was making mine make chunking/popping rattling noises.

    I think I have another of them doing that in my BS-212's at high levels.

I found that using a right angle Philips on the screw cleared it up on one of them.

    Now I have to experiment with the other that seems to make chunking under high power.

    Does anyone know if the lab 12 driver audibly complains if you over excurd it?

Antone-
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Wayne Parham

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Re: One of my lab cabs is creaking ?
« Reply #14 on: March 08, 2006, 04:46:47 pm »


I think you smoked the driver(s).  The voice coil has come unbound and started to buzz.

Look at this:

LAB12 Destructive Test

In that thread, you'll find destructive test results for a LAB12 driver.  You'll also find out an easy thing you can do to prevent this in the future.  One bolt-on part for each of the drivers conducts the heat from the pole piece to the outside covers.

A lot of heat is radiated from the voice coil into the pole pieces and magnet, and that heat re-radiates into the voice coil and bakes the glue.  This is a pretty common faiulure mode for situations like you've described, extended use at high power levels.

The solution described is an easy and effective fix.

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Wayne Parham
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Wayne Parham

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Re: One of my lab cabs is creaking ?
« Reply #15 on: March 08, 2006, 04:53:32 pm »


Over-excursion makes the driver sound like a jackhammer.
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Wayne Parham
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Alan Star

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Re: One of my lab cabs is creaking ?
« Reply #16 on: March 08, 2006, 07:18:14 pm »

I am pretty sure the drivers are fine and haven't been overdriven, I have taken one out to inspect it and the voice coil doesn't look in the least bit burnt, and the cone moves in and out freely and feels nice and stiff. They have never been fed huge amounts of power either.

There are binding posts on the inspection plates which i dont use any more as I have routed the cables through to neutriks at the back of the speaker. I am getting some 6mm aluminium covers made up to replace the wood covers and am going to recess them into the timber so hopefully this will solve the problem. Antone, chunking/popping/rattling noises could easily describe how it sounds when turned up.

I agree with the suggestion of swapping drivers/cabinets until you isolate the problem but don't want to go through this process because the other cabinet is running fine and dont want to mess with it especially because when you take the driver out you have to replace the gasket and I don't have spare gaskets.

Thanks for your help / suggestions everyone, will post back here once I get these aluminium covers on and try it out again.
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Antone Atmarama Bajor

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Re: One of my lab cabs is creaking ?
« Reply #17 on: March 08, 2006, 09:08:09 pm »

Adam if you take the drives out again, also try running a LF signal though them.  If you can hear the sound while they are free air, try tweaking on the binding post on the driver.  

If its loose you can wiggle the post and it will make noise.  

You maybe able to do this by simply running the cab with the access panel open since the lab12 binding posts will be exposed.

Antone-
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Alan Star

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Re: One of my lab cabs is creaking ?
« Reply #18 on: March 08, 2006, 09:14:32 pm »

Yes I did this running them in free air and one thing i did notice is that the wires that run from the binding posts on the speaker frame to the voice coil were slapping against the cone with the cone movement but I thought that couldn't possibly be making all that noise, anyway I twisted the binding posts a bit to try and get the wire to clear the cone.
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Dave Rickard

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Re: One of my lab cabs is creaking ?
« Reply #19 on: March 08, 2006, 11:44:32 pm »

Alan Star wrote on Wed, 08 March 2006 19:14

but I thought that couldn't possibly be making all that noise, anyway I twisted the binding posts a bit to try and get the wire to clear the cone.

Wouldn't the horn would amplify the lead slap as well as the program material?  Some drivers have foam tape on the back of the cone to keep the leads quiet, others have sleeves for the leads.

Dave
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Dave
Yorkville dealer

"The wrong piece of gear, at the right price, is still the wrong piece of gear."

"If you don't have good stuff at each end of the signal chain, (mics and speakers) what you use in between is just turd polish."--Dave Dermont
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