Speakers - Do they wear out?

[Ex_Vintage]

I my experience, speakers either fail due to over stress (fried voice coil) , or they simply degrade due to the age of the materials (usually the cone surround fails due to dry out). Older speakers usually suffer surround failure and need to be re-coned. My question is more in line with the continuous operation of a speaker. Speakers are electro-mechanical devices and any mechanical mechanism will suffer some sort of cycle rate failure, or material deformation over time, So with that in mind, is anyone aware of a "wear out" issue in modern speakers? Additionally, is there a characteristic change that a speaker will go through during its lifetime, such as  a change to its frequency response characteristics?

[adaboy]

Dec 22, 2018 23:30:45 GMT -5 Ex_Vintage said:

I my experience, speakers either fail due to over stress (fried voice coil) , or they simply degrade due to the age of the materials (usually the cone surround fails due to dry out). Older speakers usually suffer surround failure and need to be re-coned. My question is more in line with the continuous operation of a speaker. Speakers are electro-mechanical devices and any mechanical mechanism will suffer some sort of cycle rate failure, or material deformation over time, So with that in mind, is anyone aware of a "wear out" issue in modern speakers? Additionally, is there a characteristic change that a speaker will go through during its lifetime, such as  a change to its frequency response characteristics?

Hmmm, subscribed! Looking forward to answers to your question.

[DYohn]

"Wear out" is an interesting idea. A driver's Q and Fs will change over time as the compliance of the spider and surround changes, and it is theoretically possible that this could alter the sound of the system enough to hear. Voice coils and magnets do not degrade over time in normal use (as long as no over-power or physical damage.) In general, however, I'd say it's not something to be worried about. What is much more likely in older systems is a capacitor or two in the crossover network will fail.

[Ex_Vintage]

For speaker crossovers, the caps are a film type which do not have the chemical makeup and resultant thermal issues that electrolytics do in a power circuit. Inductors are passives that will not change over time. So, I agree, its largely an issue of "work hardening" materials where the compliance of the material changes and that will have an effect on the frequency response. It may be that a significant change is necessary to alter the performance of a speaker to the point it is even detectable. This is also a curious phenomena, that is some way would be associated with the belief that it is necessary to "burn in" a new speaker. The only reason such a thing wold be real, would be due to changing compliance of materials.
Just a thought.

[DYohn]

Dec 23, 2018 11:44:39 GMT -5 Ex_Vintage said:

For speaker crossovers, the caps are a film type which do not have the chemical makeup and resultant thermal issues that electrolytics do in a power circuit. Inductors are passives that will not change over time. So, I agree, its largely an issue of "work hardening" materials where the compliance of the material changes and that will have an effect on the frequency response. It may be that a significant change is necessary to alter the performance of a speaker to the point it is even detectable. This is also a curious phenomena, that is some way would be associated with the belief that it is necessary to "burn in" a new speaker. The only reason such a thing wold be real, would be due to changing compliance of materials.
Just a thought.

Not work-hardening, quite the opposite. Spiders develop micro-cracks with use and become more compliant. This is the main mechanism of loudspeaker "break-in" as the Fs, Vas and total Q of a driver changes by up to 20% in the first 40-50 hours of use. There is no myth to loudspeaker break-in, it is a well-understood behavior of dynamic loudspeakers, and manufacturers actually list driver parameters with the predicted "after break in" values for designers. Nothing becomes "harder" with the possible exception of old foam surrounds. and then when they get hard enough hey simply crack. All caps change with time, even film and oil-filled ones. And if a loudspeaker Xover uses electrolytic caps, it is a cheap-ass crossover and will likely sound like crap in my book.

[DavidR]

Large drivers that have a spider can wear out and become over compliant. Speakers using electrolytic capacitors in the crossover can degrade and typically rise in capacitance - thus changing the crossover point. They will also sound dull due to aging. Older mylar and polypro film caps can also degrade and sound dull. Not so much with the newer film caps. And of course, as you mentioned, the surrounds can wear out and deteriorate.

[DavidR]

Dec 23, 2018 11:53:11 GMT -5 DYohn said:

Dec 23, 2018 11:44:39 GMT -5 Ex_Vintage said:

Not ............................................................................................... And if a loudspeaker Xover uses electrolytic caps, it is a cheap-ass crossover and will likely sound like crap in my book.

Some of the most expensive speakers out there use NPE(lectrolytic) capacitors. Most people can't tell the difference and tests have been done using so called cap experts, An electrolytic cap behaves differently in a crossover than a film cap. Non polar electrolytic caps (npe's) measurement results are significantly more frequency dependent than even the least expensive film cap (mylar or poly). Simply put, as frequency increases measured capacitance goes down. As frequency decreases it goes up. This is much more pronounced with npe's. The changes are insignificant with film caps.

When I retired I took up restoring speakers. Mostly Acoustic Research but have worked on a number of others. I used some Mundorf ECap electrolytics (and Bennic for the larger values) in an AR10Pi and chose film for a rebuild of AR91. Both are 3-way speakers. The 10Pi sound every bit as good. When going with film caps in a circuit designed for NPE caps it is not always as easy as replacing a value for value, as I found out. You can get a lot of brightness, glare and harshness from film caps; more so from less expensive ones. I ended up recapping the recap of the AR91s and used Clarity CSA on the series caps and added bypass caps to help control the brightness, glare and harshness. Now they sound nice; before I was unable to listen to them for more than 30 minutes as they'd get 'under my skin' (listener fatigue).

[405x5]

Dec 22, 2018 23:30:45 GMT -5 Ex_Vintage said:

"I my experience, speakers either fail due to over stress (fried voice coil) , or they simply degrade due to the age of the materials (usually the cone surround fails due to dry out). "Older speakers usually suffer surround failure and need to be re-coned". My question is more in line with the continuous operation of a speaker. Speakers are electro-mechanical devices and any mechanical mechanism will suffer some sort of cycle rate failure, or material deformation over time, So with that in mind, is anyone aware of a "wear out" issue in modern speakers? Additionally, is there a characteristic change that a speaker will go through during its lifetime, such as  a change to its frequency response characteristics?"

"Older speakers usually suffer surround failure and need to be re-coned" 

This is a common misunderstanding.
"Re-foaming" and reconing  are entirely different procedures. Refoaming is just that...….the surround attached to the cone is scraped clean and replaced and reattached to the basket. 
Reconing involves usually both the voice coil and the cone being replaced. Of course the foam will also go along with that. A loudspeaker will usually get the whole smash if the coil is cooked. A speaker that has NOT been overdriven in its life rarely will need to have a voice coil replacement.

This is not the easiest question to provide a simple answer, because we're usually taking about a loudspeaker SYSTEM (tweeter, midrange, woofer, crossover and controls,) etc. any one or combination will effect the performance outcome went bad things happen.

Bill

[DYohn]

Crossovers use electrolytic capacitors only when necessary for cost reasons. I don't care how 'expensive" the system might be, using an electrolytic is a cheap-out tactic to save money and/or space. It's a cop-out demanded by bean counters who don't give a damn about audio. In my opinion. And by the way, this is the attitude that got me fired from Sony.

[Ex_Vintage]

Electrolytic caps typically have greater ESL and ESR than a film cap. The "wear our" issue with electrolytics is they lose electrolyte due to out gassing (which is accelerated by current magnitude causing temperature rise). An electrolytic will decrease in capacitance over time due to electrolyte loss. An electrolytics capacitance is not frequency dependent, but its ESR is. The ESR decreases with frequency. Yes electrolytics are a poor choice for an AC application and especially of you want a consistent filter break frequency.
One curious question with respect to speaker break in. IF a new speaker requires 40-50 hours of use to "meet specifications" I assume the flexibility of the spider and the surround are changing. Since these speaker components are made of homogeneous materials, what stops the change in compliance. I would assume if the material is homogeneous, the rate of change would possibly exponentially decrease over time, but this would yield a significant change in the speakers performance over a relatively short period of time (maybe 400-500 hours use).

[DavidR]

To measure is to know

[DYohn]

Dec 23, 2018 22:36:52 GMT -5 Ex_Vintage said:

Electrolytic caps typically have greater ESL and ESR than a film cap. The "wear our" issue with electrolytics is they lose electrolyte due to out gassing (which is accelerated by current magnitude causing temperature rise). An electrolytic will decrease in capacitance over time due to electrolyte loss. An electrolytics capacitance is not frequency dependent, but its ESR is. The ESR decreases with frequency. Yes electrolytics are a poor choice for an AC application and especially of you want a consistent filter break frequency.
One curious question with respect to speaker break in. IF a new speaker requires 40-50 hours of use to "meet specifications" I assume the flexibility of the spider and the surround are changing. Since these speaker components are made of homogeneous materials, what stops the change in compliance. I would assume if the material is homogeneous, the rate of change would possibly exponentially decrease over time, but this would yield a significant change in the speakers performance over a relatively short period of time (maybe 400-500 hours use).

What "stops the change" is the physical nature of spiders. They are generally made from epoxy-impregnated paper. The mechanism of the change is micro-cracks in the epoxy between the paper folds due to flexing. Once the cracks are formed along the stress lines, the change stops since there is no more to change - no more epoxy to crack. The mechanism (at least in dynamic drivers like woofers) happens once, and the degree of change is measurable and predictable with statistical accuracy.

Woofer manufacturers will list T/S parameters for their drivers after the break-in occurs. If you measure a woofer right off the line it will be different than the specs, but after break-in will fall within the normal variance of the specs. Some manufacturers will actually break-in their drivers before they ship them to their users, especially for higher-end system companies.