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God's element
04-01-2006, 03:12 PM
Hello,

What are the telltale signs of a speaker going bad? I know that the voice coil will rub making a scratching sound but I also hear of the spider wearing out, but I don’t know the symptoms. Also, what is the life span of a speaker? How long will it perform if operated daily? What are other symptoms of a speaker going bad?

Thanks

speakerdave
04-01-2006, 03:40 PM
Heavy cones in soft suspensions can sag over time. I can remember reading that woofers should be rotated 90 degrees every six months are a year. The old foam surrounds will decay. Some turn to oil (AR) some turn to dust (JBL) some turn to crust (Lansaloy). I don't know if more recent foam has been bred to eliminate these problems. I hope so.

Old cones with integral paper surrounds can dry out and/or weaken at the hinge points, especially if over-driven. Doped versions of this design maintain flexibility better, but still can be over-driven.

"Accordian" pleated surrounds and spiders are made with something poured on a fabric base, linen, I think. These can last a very long time with no apparent time-induced negative effects, although both will probably soften some with use, especially if over-driven.

Some of the old glues that hold things together can apparently give out under certain conditions.

I've seen paper cones that look sun-bleached. I don't know how to tell if they are weakened structurally by that, so that, for example, their pistonic behavior would give up the ghost at a lower frequency, but I suppose it stands to reason. Paper cones driven hard in breakup mode are probably slowly turning to pulp.

In general, I think it is reasonable to assume that moving parts of mechanical devices experience wear. The more they move the more wear; the more abuse they sustain, the more they weaken. If you have two-decade-old drivers made by a company still in business, and they keep new cones available, a recone might purchase some peace of mind for you, especially if the speakers have been used a great deal and driven hard. On the other hand, there are many old speakers out there that have not been reconed, and are still apparently pleasing their owners.

David

Steve Gonzales
04-01-2006, 03:51 PM
When you've got a worn out spider, the speaker will bottom out easily.

God's element
04-01-2006, 04:54 PM
thanks for the info,

what do you mean by bottom out? sorry for the nub question but i dont know the jargon yet.

Steve Gonzales
04-01-2006, 05:42 PM
The accordian pleated spider is the other part of the suspension that works in tandem with the foam or pleated paper surround. When the spider is fatigued or worn out, it is unable to control the cone and thus the whole thing travels beyond it's intended point very easily. Sometimes you'll hear a 'pop' and sometimes you'll hear a 'knock'. Those noises are caused by either the voicecoil bobbin bottoming out in the gap or another part slapping against the pole piece. Think of it as badly worn shocks on a car.