turning your woofer

[greyhound]

in the dutch audio forum (where im active) the discussion started , if it makes sense to turn your woofer (for instance clockwise) because of material fatique. the weight of the woofer may have an impact on the coil.
so turning it every year may stabilise the quality on the woofer in the long run.
ive had some pretty old woofers and none of them had any coil problems.
no scraping sounds or anything like that.
you guys are facing the vintage stuff reguarly does it sound familiar. ther is some logic in it i think.
the discussion started when someone picked up some old Kef's and transported them on their side in staed of on the back and his coil was damaged. The speakers were old (22years). he didnt know for sure that the damage was already done before transport.

[moldyoldy]

I have no idea when woofer rotation started, but I've seen several 50's cabinets with penciled rotation logs on the backs or inside. The degree of merit for the practice would depend entirely on the properties of the individual suspension. I've been able to get a few more miles out of an old woofer or two that were beginning to rub by 180 rotation, but whether regular rotation can extend the overall life is pretty iffy, and again, depends on the speaker.

Suspensions treated with non-hardening dope sometimes need turned to keep excess dope from puddling or migrating, but simply removing the excess dope is a better fix, after all...it is excess...

I've seen some amazing damage to speakers from shipping, but find it hard to imagine a voice coil getting hurt if nothing else was damaged, like the pole or magnet shifting. It takes more than the coil simply touching the pole a few times to cause any real damage.

There is an exception. Foam surround woofers with disintegrating or no remaining foam could easily sustain coil damage, and are actually pretty likely to, even with decent handling. When the cone weight hangs only by the spider, every bounce will force the coil against the pole plate. Speakers in this condition should use some non-destructive way to ensure the cone is centered and can't move in shipping, or the recipient may need to do a recone instead of the foam job he'd planned on.

For gear that gets roaded, you can reduce concerns by connecting a short across the terminals. When the cone bounces and moves, it creates a small voltage, and the short provides a braking force just like a low output impedance amp. Some Pro cabs use a switched jack that provides this shorting when the plug is removed.

[greyhound]

well that makes sense. so turning your drivers is something they advised in the old days. The materials the woofers were made from are not heavier than the stuff they use today (i think) exceptions for brands like Kef and tannoy. the older woofers i have seen from them were quite heavy. the spider most have alot of strain on it and will create problems in the long run. Do you think later developments have illiminated this "problem"

i had trouble understanding the last bit of the story.
are you saying that supplying a battery (like 1.5 volt) to the terminals before transport is a smart thing to do?
ore just short circuit them

[moldyoldy]

Do you think later developments have illiminated this "problem"

i had trouble understanding the last bit of the story.
are you saying that supplying a battery (like 1.5 volt) to the terminals before transport is a smart thing to do?
ore just short circuit them

Improved materials extend performance life, but eventual sag is inevitable as long as we use suspension materials that weaken with time and use. Somebody needs to invent a linear, mag-lev, variable-compliance suspension.

No, DON'T hook a battery to the speaker, merely attach a short wire across both terminals for transit. We think of speakers turning voltage into cone motion, but they can do the reverse as well, movement of the coil will produce a small, but measureable voltage, called 'back EMF'. Shorting this voltage out with a jumper wire for shipping "damps" the cone motion, though it doesn't prevent it entirely. It's also something most people never do. If you're a worrier, it's an easy task that might let you rest easier.

[greyhound]

Improved materials extend performance life, but eventual sag is inevitable as long as we use suspension materials that weaken with time and use. Somebody needs to invent a linear, mag-lev, variable-compliance suspension.

No, DON'T hook a battery to the speaker, merely attach a short wire across both terminals for transit. We think of speakers turning voltage into cone motion, but they can do the reverse as well, movement of the coil will produce a small, but measureable voltage, called 'back EMF'. Shorting this voltage out with a jumper wire for shipping "damps" the cone motion, though it doesn't prevent it entirely. It's also something most people never do. If you're a worrier, it's an easy task that might let you rest easier.

never gave it any notion but it 's true. moving the woofer wil create energie. well thats a good tip so thank you for that.

and i think its better for me not to get involved in creating new kinds of supsension. i can barely get my tweeter reconed.
So the sagging woofer story is a fact. any idea how this is wilth \jbl drivers. because their quite big but very light weight pulp.

[moldyoldy]

They're all different. Long-throw subs are likely the worst, but I'm speculating now.

[greyhound]

They're all different. Long-throw subs are likely the worst, but I'm speculating now.

the cone is heavy but the way their build is pretty robust. I think its better to look at material than size.
ore does size matter?

[Mike Caldwell]

Some of the JBL Cabaret series speakers used 1/4 normalling jacks that would apply a short to the speaker when the plug was removed. I can't think of any pro speaker today that puts a short on the cabinet when it is unplugged. Most high power cabinets today use Speakon connectors and there is no real to do that with them anyway.

I have heard of the cones sagging on some horn loaded designs where speaker is mounted in a face down kind of position.

Mike Caldwell

[RKLee]

Personally, I would think the fact of removing and re-fastening the mounting screws presents the possiblity of damaging the speaker cone, you know like, "oops." I personally it is not work the risk and I would forgo this process.

[greyhound]

Personally, I would think the fact of removing and re-fastening the mounting screws presents the possiblity of damaging the speaker cone, you know like, "oops." I personally it is not work the risk and I would forgo this process.

i can agree. also a lot of screwing and unscrewing would eventely damage the screw hole. the wood would crumble i think so the screw loses its grip.

[Zilch]

T-nuts, typically.

[RKLee]

i can agree. also a lot of screwing and unscrewing would eventely damage the screw hole. the wood would crumble i think so the screw loses its grip.

Not that, just that if your screw driver slips or something falls on the woofer cone and ruptures it, etc etc you're pretty much SOL. Woofer cones aren't cheap.

I used T-nuts on when I built my speakers using 2 Altec 414-8Bs. T-nuts are like little cleats with a nut. You put them in from behind the sound board.

[greyhound]

Not that, just that if your screw driver slips or something falls on the woofer cone and ruptures it, etc etc you're pretty much SOL. Woofer cones aren't cheap.

I used T-nuts on when I built my speakers using 2 Altec 414-8Bs. T-nuts are like little cleats with a nut. You put them in from behind the sound board.

oh im sorry
i totally understood what you were telling me. i just added a possible problem.

[Gary L]

MOLDYOLDY,

For gear that gets roaded, you can reduce concerns by connecting a short across the terminals. When the cone bounces and moves, it creates a small voltage, and the short provides a braking force just like a low output impedance amp. Some Pro cabs use a switched jack that provides this shorting when the plug is removed.

I always wondered about this! When I purchased 2 sets of Model 19s new, each came with a U shaped paperclip grounding black to red. There was a tag by the connectors that said "Remove and discard before attaching wires from the power amp". Every time I ever transported them I put the jumpers back on figuring they knew what they were doing and there must have been some reason!

Gary

[moldyoldy]

Hi, Gary,

If you still have the clips and tags, I'll bet you could pay for several months' satellite access for what some "minty original extremely rare Altec Model 19 motional dampers with instructions" would bring on eBay...