Broken Tinsel leads. |
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Shortrope
Young Croc Joined: 08 July 2013 Location: Ireland Status: Offline Points: 1232 |
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Posted: 20 January 2017 at 8:36pm |
These are BMS 18" 1200w drivers.
I've had the Tinsel leads fail on a pair now, snapped off just by the Solder join. They're in Relfex cabs driven by a PXM 1450 so about 1450w with appropriate limiters. Live music venue so not driven as hard as they could be. I've sent pics to BMS as well to see if they've any ideas what's going on. Any ideas lads?? |
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My Tinnitus is coming along nicely!!
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bass*en*mass
Old Croc Joined: 03 September 2009 Location: "unknown" Status: Offline Points: 4009 |
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hmm, had very much the same issues with one too.. has been dealt with ok.
doesnt seem to be a general issue though. propably check cab tuning, xover and limiter to make sure its not a "user error" due to overexcursion? |
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Centauri
Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792 |
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Always on the cards if you have movement next to a solder joint - the leads should always be secured away from the solder connection.
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bee
Old Croc Joined: 14 June 2011 Location: Middlesex Status: Offline Points: 4553 |
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Bass en mass there in the same cabs as you have..
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https://www.elements-audio.com
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MattStolton
Old Croc Joined: 04 September 2010 Location: Walthamstow Status: Offline Points: 4234 |
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Would appear to be a work-hardening fracture.
Any metal "wiggled", firstly gets warm (you are doing "work" on it, thermodynamic laws, etc) which realigns the crystal structure, or even moves the crystal boundaries. Eventually, with enough energy in, you can cause microscopic cracks along crystal boundaries, which then snow ball into big enough cracks to be seen, and eventually - "ping". Bend a peice of copper wire in your hand, in the exact same spot, repeatedly, and you will be able to feel the heat put into the bend, and eventually it will fracture. Most metals will do the same thing, but the design of the item and exact metallurgy, and method of smelting/cooling, of the item will govern how quickly it goes. Rolls Royce aeroplane engine blades are actually "grown" as one single crystal, to eradicate crystal boundary weaknesses. In this instance, being near a solder joint, the solder has crept up the litz, and formed a reinforced region. As the solder finishes, the string filled pipe of wire is then mega flexible, but this initial region is making up for the inflexible solder region. This leads to a area of concentrated "work" being done on it from movement, and - "ping". Same reason belt pack mic cables break just after the cord grip, the initial region of flex is flexing for its own applied energy to it, and having to flex for the immobilised cord grip region. Double movement is twice as much "work" applied to one particular region, or set of crystal boundaries - "ping". Simply thermodynamics in action. Matt Stolton - BSC (Hons) Chem, A Levels in Maths, Chemistry and Physics, AS Maths, and 11 GCSEs. SmUg GiT ExTrOaDiNaIrE. And avid BBC 4 documentary watcher. PS - The fix is to dress the route of the tinsel, so that the movement, and therefore the induced work and heat, is centred on a broad portion of the middle of the tinsel. In that way the ends are fairly immobile, and so won't move much relative to there fixing points, avoiding localised stress, and what heat and work is applied to the wire, is over as large a length as possible. Same energy applied over a large area, means the heat is able to radiate away before it builds up enough in any one local spot to affect metal crystal structure.
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Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains" |
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jbl_man
Moderator Group Joined: 12 January 2005 Location: London. Status: Offline Points: 11155 |
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"And avid BBC 4 documentary watcher."
Completely agree with that Matt,it's esential viewing for me too. James May re-assembling a Dansette record player the other night,what better way to pass 30 minutes on a cold night. |
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Be seeing you.
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MattStolton
Old Croc Joined: 04 September 2010 Location: Walthamstow Status: Offline Points: 4234 |
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I watched it too, I turned to the wife and said that is a "Dansette record player, I had one in before Christmas and had to rewire it", and she told me to stop being so daft, how could I possibly know what that 60's peice of junk was, and then James said "This is a Dansette...." I did feel for him trying to reload the amp module back in, quite a bird's nest, and a valve in the mix to boot. She skulked off to the fridge and got me a beer as recompense, so happy days! I have also correctly predicted the outcomes of the last 9 episodes of "Death In Paradise", which also winds her up. Serves her right for making me watch it. If there is a brother of deceased, he is always guilty...with or without accomplices is the trick!
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Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains" |
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valve head777
Old Croc Joined: 27 July 2012 Location: East Sussex Status: Offline Points: 1781 |
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Just wondering why they put such thick insulation on the tinsel leads?
This just adds unwanted mass to a part which is prone to resonance. The added rigidity also concentrates the flexing to the anchored ends. |
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Freedom of choice, choice of freedom.
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madboffin
Old Croc Joined: 03 July 2009 Location: Milton Keynes Status: Offline Points: 1538 |
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Yes, the most likely cause of that problem is "poor lead dress" which should be a warranty claim.
I would have expected to see a strain relief sleeve (or at least a bead of non-corrosive silicone) over the termination, to stop the wire from breaking where the solder has wicked up the braid. The classic method of checking for problems with lead-in wires is to use a stroboscope and audio oscillator, to see how they behave as the frequency is swept through the speaker's operating bandwidth. They can sometimes resonate and flap around in spectacular fashion. This is normally done at the prototype stage - the result of the test enables the designer to specify a length of wire, end termination, and lead dress that minimise the chance of breaking. That's why, if re-coning a speaker, it is necessary to take note of the lead in wire arrangement and copy it closely on reassembly. Edited by madboffin - 21 January 2017 at 7:25pm |
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Shortrope
Young Croc Joined: 08 July 2013 Location: Ireland Status: Offline Points: 1232 |
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Just to clarify, the heat shrink insulation went right over the spade terminal that the lead was soldered to (I'd cut it off before the pic).
The lead and the insulation had snapped together just at the spade. |
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My Tinnitus is coming along nicely!!
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bass*en*mass
Old Croc Joined: 03 September 2009 Location: "unknown" Status: Offline Points: 4009 |
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looking back i would say its a mix of both, manufacturing/design issue+slightly overdriven re xmax for some duration? (strangely it only happened to 1 driver of 24, 12 of which still play fine 2 years later..)
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bee
Old Croc Joined: 14 June 2011 Location: Middlesex Status: Offline Points: 4553 |
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by design its demanding on drivers, hence why a lot of drivers cant be used for b6 loading.
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https://www.elements-audio.com
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