Transporting speaker cabs face-down

There shouldn`t be any crud in the magnetic gap! However, I did once have an Old Altec Lansing that developed an intermittent raucous scraping noise that was indeed something twixt voice coil and pole. The only way I could cure it was to remove the aluminium dust dome, and after vainly trying to clean it out with various bits of card, sticky tape etc. I ran the speaker face down with a low frequency sine wave for some time. Eventually a small chip of aluminium dropped out.

I would expect a speaker is safest transported on it`s face, as I image that way there are the least stresses on the basket from the weight of the magnetic assy.

Other peoples mileage may vary (as they say)

Ron(UK)

I've never had an issue transporting speakers face down and have hauled them like that for thousands of miles. These days we jam everything together in a trailer in a standing position.

You would be correct. And I'm going to try to get your Furman info today as my brother in law wasn't available yesterday.

Usually, speakers fail like this from being dropped and the magnetic magnetic assembly shifts. When this happens the pole piece rubs against the voice coil. Speaker is usually toast when this happens.

Also, if the speaker has been over excursioned from abuse, the rear of the voice coil warps and rubs on the pole piece during times of higher excursions causing a scratching rubbing sound.

I had a yamaha 4115 drop vertical once and it shifted the magnetic so much that it froze the voice coil.

I had a grundorf trap that fell over that snapped the magnet/pole piece off the cast frame.

Bob

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Small particles could collect and be forced into the gap by dropping where they will stack up an cause a rub issue. The magnetic assembly shifting is usually when they are transported vertically. It's really hard to shift the magnet face down. What I have seen, with high compliance loose suspension, big voice coil drivers is the coil fall out of the gap, then foul the voice coil former.

Remove the dust cap and have a look. It's all you can do at this point. Sometimes Xylene or Acetone or Toulene can soften the glue to permit removal, or you can use a razor blade.

Pull the cone toward you and see what is actually rubbing.

Debris can be fished out with masking tape, compressed air, shims, etc.

If the gap is not symeterical and concentric, the speaker is toast. It has to be reglued and remagnetized. Unless it is a holy grail speaker, buy a new one.

If the former is deformed, maybe you can finesse it back with shims but a new voice coil is usually required.

Good luck

on

The problem is now more likely the owner having stored it in a damp garage for a few years , unused. There were numerous spiders webs and insect cocoons inside the amplifier and spot rusting of the metalwork of this combo. So probably insect cocoon or rust flake has got in the coil gap or even cone distortion due to damp differentially affecting/distorting the cone. Presumably "palpating" the cone in different clock positions to feel for rubbing would be the best disgnostic.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

If there is any paint inside there, it can peal and fall off into flakes. I saw one gap all rusted once.

greg

falling

down.?

garage

and

cone

I've not literally been able to get my hands on this one yet - still with the owner , he decided to aquirt the universal solve-all in there - WD40.

If it is salvagable from WD40 etc and if the oproblem is due to damp affecting the cone , is this being a 15 inch cone more likely to have cone distortions than a 12 inch for the same sort of damp? Intuitively I could expect a large cone to be more likely to have a twisting type distortion than a smaller cone, having a greater proportion of unsupported edged length to surface area.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

and

amplifier

for

flakes.

twisting

correction - vice versa - less proportion of edge length to area

Well if it wasn't knackered before, it is now! Save the WD40 for rusty gate hinges, it has no place at all in an electronics workshop.

(cue huge debate about the pro`s and cons of WD40)

If it`s a speaker from a reputable pro manufacturer, get it reconed at Wembley Loudspeaker, if not, just replace it with whatever the customer will pay for.

What part of a speaker do you consider to be 'unsupported edge length'?

Ron(UK)

with

WD40.

cone

twisting

If you took a cone from a 12 inch and a 15 inch and laid them face down on a surface. Then a flat plate on the cylinder extension of the 12 inch and then some weights on that, but not enough to cause it to collapse. Then add the same plate and weights to the 15 inch and before the cone would collapse by compression or radial buckling, would not the larger one be more likely to start to fail by the central section twisting and then collapse. Less torsional stiffness is probably the term I'm looking for.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I don't really understand where you're coming from, the only 'weight' on a speaker cone is the voice coil assembly and dust cover and they weigh very little, even in a high power speaker. compared to PA speakers, guitar amp speakers are often deliberately made with reduced cone stiffness so that they 'trash out' at lower volumes.

In the back of my mind, I do recall seeing a photo of a speaker cone, face down, with a chap standing on the voice coil former to demonstrate the strength of the cone assy. I don't remember which company it was.

Most pro speakers have very rigid cone structures, it`s pretty uncommon to find a professional speaker failure that is attributable to mechanical damage during use, even over excursion is fairly rare - tho dj`s do try their hardest.

Almost all pro speaker burnouts are due to being driven with amplifiers of insufficient headroom,[1] or some external failure i.e. Bad switch on sequence etc.

There was once a company called Baker who made probably the worse speakers in the world, the skinny cast alloy baskets would crack, dumping the puny magnet in the bottom of the cabinet - happily long in the past.

Ron(UK)

then

would

more

collapse.

This was not in-use damage but from storing in a damp garage for some years. It went in perfectly ok and came out with amp working but speaker sounding like the amp was clipping. The amp will drive an external speaker fine and another amp gives horrible noise through this speaker. So damage due to transporting from (ot to) the garage face-down or more likely something to do with damp distorting the cone or maybe distorting it now its been indoors for a few weeks, drying out.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on