There really is no such
thing as break-in. Sorry to dispel all these myths that writers
who get paid by the word and are often politically connected
to their suppliers have put in your head; but let's examine
all the parameters.
To start, do not confuse
"break-in" with "burn-in". Burn-in
is a factory procedure when after a unit is built it gets
connected and operated (often into a rated load; for example
a power amp connected to a load resistor) to determine
if anything will fail - an infant mortality test for all
the components if you will. This has nothing to do with
running the equipment so it gets "better" and
therefore the manufacturer has "saved" you some
"time and effort", although sadly, some
manufacturers or after-market snake oil vendors will try
and sell you on this idea.
First let's examine what
We all know batteries
change. Because of their continuing and changing electro-chemical
action they are more organic than anything else, and therefore
exhibit all sorts of subtle and not so subtle operational
changes. We all know batteries drain, and therefore their
entire mode of operation is continually changing - their voltage
for example. But you're not directly listening to batteries
- this is just an example.
Be aware there are MANY types of capacitors. Precision
wound mylar film caps are VERY stable. Chemical types
that have electrolytes - similar to a battery - are all
over the map, and if subjected to temperature changes
and high current flow they will tend to have a rather
short life - perhaps a very few years. Perhaps months.
There are "average"
caps and "audiophile grade" caps used in some passive
crossovers in speakers. There are instances where they have
a price ratio of 50 or 100 to one. Do not be surprised if
your speakers that cost $5000 have $3 caps in their crossover.
In addition, the % tolerance of the large value caps used
in crossovers is rather sloppy. Expect +/- 10% or worse if
you are lucky.
there are tubes. Since the thermionic emission of tubes means
that electrons are boiling off the cathode, as time goes by
the cathode gets depleted, and various other subtleties take
place, and so yes, you can easily say that tubes 'change'.
You could theoretically consider this 'break-in' if you were
to also say that the reference point would not be reached
until the tubes were operating for 100 hours. What if your
reference point were at zero hours? Then from that point on,
the circuitry would get "worse".
But for essentially everything else, the
effect is more human than a phenomena of physics.
The psychoacoustic truth
is that nearly anything will sound correct - and become your
personal "reference" - if you listen to it long
enough; it becomes the new baseline (pun almost intended)
of your reference, and then "other" things will
then sound wrong, or at least different.
When you listen to a new
unknown for awhile, its physical characteristics fill slots
in your auditory mental library that may or may not line up
with your auditory notions, pre-conceived notions, or expectations.
For instance, if you play one brand of piano for a long time,
when you play a different one it seems "wrong" for
a "certain amount of time". As you become more adjusted
to it it might not seem so "wrong" but it will still
seem "different". The entire mechanism of your hearing,
including the vagueness of your auditory memory "learn"
the complex loudness envelope, frequency, harmonic structure,
and phase characteristics of the overall sound and stamp that
impression onto your admittedly soggy notions. Very few people
can listen to a Steinway, then a Bosendorfer, then a Yamaha,
then a Young Chang and come back 6 weeks later and pick them
out again. Of course YOU may think you are in the minority
and are able to do this. That's what being an audiophile is
all about. (!)
If you go back and forth
between driving an 18-wheeler, a sports car, and a squishy
sedan, each seems like a "wrong fit" for a little
while until the new proprioception reference points settle
in, then eventually the vehicle you are in becomes the "norm".
In essence your nervous system and its inherent feedback loops
are micro-phaselocking to all the physical and spatial reference
points, and there is a "fit" between your body-mind
loop and its operating environment. This exact same phenomena
happens in audio and the mechanism of your hearing.
While you are IN the truck
you may long for the tight feel of the sports car, but the
truck is still your current reference set, and then the NEXT
vehicle you are in, no matter what it is, is referenced back
to your last reference point, the truck. This is the same
phenomena as with speakers. You notice it because speakers
are mostly so different from each other.
Besides, all speakers
are of course designed and tested "new" --- with
new parts. No one designs and tests speakers with old, used
drivers, with the surrounds loose and worn out, etc.
Yes, sure everything has
a downward curve. Speakers, like people, start getting worn
out from the moment they're born. So you might
say that speakers never get better, they only get worse over
time; the surrounds get looser and less able to mechanically
snap back to their original center position; the magnets get
weaker, although only a tiny fraction.. and so on. Of course
the phrase "over time" may typically mean MANY,
MANY years, just like people. There is no technical change
over a few hours or days... but as a human you might have
a perceptual change over a few minutes, few
hours or few days.
Yes, there are also the issues of temperature
and humidity, but for these purposes we will assume a moderately stable
"living room" set of measurements.
driver technologies are somewhat ahead of the stuff that so
many of us might have enjoyed in "college" years
ago. From the early 70's on many manufacturers used cheap
drivers available to both (a) make a buck and (b) ensure that
with a reasonable amount of smog and a reasonable amount of
frat house partying, the most owners of these low freq drivers
or subs would "use up" the drivers and therefore
they would require reconing or replacement. Under the thinly
veiled guise of "better sound" the manufacturers
used the worst and therefore most absorbent paper cones; the
worst and therefore most smog/pollution-sensitive 'foam' surrounds,
(often called "foam rubber", but not rubber at all,
actually a urethane) and so on. The resistance to humidity,
ultraviolet, temperature cycling, pollutants, thermal effects
of the coil and magnet, and so on was minimal. Did they "change"?
Yes, but not over a few hours or a couple of weeks.
Newer properly designed
and made drivers, with stable materials, still look the same
in measurements before and after they are "exercised".
We can take a driver at room temp, check its parameters, then
exercise it by driving it right to its xmax limits for hours,
then measure it again, and the amount of change is small,
and mostly due to coil temperature. More stable materials
are just that -- more stable. As soon as the coil temperature
goes back to ambient, the measurements are the same.
And besides, the most
difficult thing to do in all of speaker manufacturing (besides
getting it right in the first place, the subject for at least
one long book) is consistency! We want a finished speaker
(that means speaker cone, speaker driver, and finished product
in a box, including crossover and adjustments) made today
to sound the same - within incredibly tight limits - as one
made last week, or last year -- or next year! And we also
want 6 of them made today to sound the same, and to measure
to within a hair of a reference manufacturing standard.
dispel any myths about manufacturing tolerances, everything
has a tolerance. If you machine 2 pieces of metal which then
have to fit together, they each have a + or - mechanical tolerance.
So here's the surprise:
if you purchase 6 tweeters (or mid range drivers, etc.) from
a manufacturer and connect them up to a rotary switch and
feed them white noise, you will hear, with your own hearing,
6 apparently different sounds as you rotate the switch. That's
a sad fact of life. Amazing! There is simply almost no
such thing as "the same" ! They are all close
perhaps, but all somewhat different. Your ears may be able
to discern that difference... or maybe not. Here's why:
To touch on specs and
frequency response for a moment, many if not most mfgs spec
response as + or - so many dB, i.e. ±3dB. Therefore
you can have 2 drivers sitting on the test bench connected
to the aforementioned rotary switch, and one driver might
have a bump of 2.5 dB batween 2k-4k and the other might
have a dip of 2.5 dB between the same frequencies and they
are both "within spec" yet to a human, switching
back and forth between the two, they sound rather different.
Perhaps very different. (they are 5 dB "apart")
Spec sheets show "smoothed" response curves. In
real life, there may be +/- tolerances of a few dB EVERY FEW
CYCLES. But if they showed you those unsmoothed
curves you would never buy anything.
But the overall point
of this paper is not manufacturing tolerances, but what constitutes
"change(s)" in parameters.
Of course over a VERY
long period (15-25 years) some parts can degrade, especially
capacitors, as mentioned above. If the wrong solder or flux
was used the connection can craze and turn into a noisy or
rectifying junction. Carbon resistors can change a couple
% or so here and there... well you get the idea. Those changes
are subtle and occur over time, which means months and years.
You might say that the
magnet [in the speaker] weakens MICROSCOPICALLY over time,
perhaps a few percent in many many years. Some magnetic materials
- and much about our understanding of magnetism still borders
on alchemy and magic - change their strength and other properties
permanently when exposed to high temperature abnormalities.
The reasons there are essentially no neodymium magnets in
large woofers is twofold: first that would be WAY too expensive,
and second, the surprisingly large temperature heating of
the voice coil would tend to weaken the magnetism.
There is the phenomena
of "driver compression" which changes with temperature,
and an issue with temperature in general. For example, if
you start out with a subwoofer in a cold room and the coil
heats up until it is "hot" then the sound from that
driver will be a little 'different'. But at the same time,
your own hearing and perception will be different than
when you started because since you have been exposed to these
loud sounds your thresholds will change, therefore you cannot
base your perception on a fixed point because your perception
of your perception is continually changing!
And last but hardly least,
the absurd myth about 'break-in' with wire and cable (ahem...
'interconnects') During my time at a private laboratory division
of Hughes Aircraft I had many opportunities to witness and
partake in various devices being tested in the most amazing
ways: everything from electron microscope examinations of
hard and floppy disc surfaces to cloud chambers where transistor
junctions were being tested to determine the extent of cosmic
ray bombardment, to changes in different alloys undergoing
thermal changes (from nearly liquid state to near absolute
zero) to ohm meters with better than milliohm resolution and
scientifically, no one has ever been able to determine anything
happening technically that would change the sound of an RCA
cable the first few hours, weeks, or months you play it.
So there you have it.
Bottom line: enjoy your
speakers and your system. If you need a laundry list of
other things to worry about in life (besides "break-in")
I can supply a very long list for you.