[Peter Wieck]

Much snippage.

A few points:

a) Replacing before failure. Use speaker surrounds as one excellent example.. Those surrounds give plenty of warning prior to failure. Checking them even semi-annually is enough. Similarly the paper cones if so equipped - treating them if they start to seem brittle (again, plenty of warning) will stop the problem dead in its tracks.

b) Oil changes vs. belt replacement: A full-service oil-change for my VW TDI costs approximately $140 including parts and labor. Synthetic diesel/ash-rated oil, filter and tire rotation. That is 0.048% of the value of the vehicle. Neglecting it could cost thousands. As to greater efficiency and operational economy, if that were the only reason, it would be a poor exchange - and there would be no reason at all not to keep the original oil in place, just topping up as needed. Do the math: my average economy for my style and type of driving is 36.8 MPG since-new (72,000 miles). Assume per VW an oil change every 10,000 miles, and diesel fuel at $4.10/gallon. Assume a 10% fall-off from dirty oil (less than that most likely). Oil = 6 x $11. Filter at $9. $75 in material -labor at $65. That is 34 gallons of fuel. 271 gallons gets me 10,000 miles at present. Assume 33.12 mpg (10% penalty) for not changing the oil. That comes to 301 gallons of fuel. Cheaper not to change the oil by $16.40. And do this over and over. Then change the engine at 100,000 miles (if not sooner) for $8,000+.

Getting to belt replacement: should the timing belt fail on an interference engine, at least a new head will be required - assuming no additional damage. Starting at $2,000 or so. So, that is maintenance. Not repair. Not a wait-until-failure item.

Tying it back to speakers: Cones, surrounds, crossovers, contacts, cleaning, proper fusing, occasional fuse replacement (you don't think they wear? Ever watched a fuse running near the blow-point? The element dances!) all are maintenance issues or items prone to wear and/or age. And their eventual failure has nothing to do with OM materials choices, execution or workmanship. It has to do with an electro-mechanical device operating at hundreds to thousands of cycles per second over long periods of time.

One more non-speaker example: I am rebuilding a small integrated amp right now that suffered a cascade effect from a single failed 68-ohm, 1/2 watt resistor on the right-channel driver board. The one on the other board is nearly black - that will get replaced too - both with 1-watt units. But had someone actually had a look at these boards before letting out the magic smoke and noticed the blackening resistors, it _all_ could have been prevented by replacing two $0.40 resistors. Now, it is a transistor driver pair, two output transistors, six other resistors and one capacitor, my labor being therapeutic, discounted. OK, David Hafler ran everything at the bleeding edge of failure, so one might be able to blame the maker here for using a 1/2 watt resistor. But that is still not the point. Repeat after me: Cascade effect. That is what I am trying to convey and how to prevent it. It may be a PITA to lift the hood on occasion with audio stuff - and even lifting the hood will not discover everything, but at least give yourself half-a-chance to avoid catastrophic failure.

Peter Wieck
Melrose Park, PA