Why burn in?

[sianturi]

I got one of my tweeter damaged (in my right channel speaker), I recently replace it with a new one (same model). I then played some music, and hear that the right speaker's (the one with the new tweeter) sound is brighter than the left speaker's. I also heard more noise produced from the right speaker.

I just remember, that every speaker (or audio equipment in general) needs several hours of burn-in. Here comes the basic question:

Why would we have to burn-in the equipment? Can somebody explain in terms of physics/electric/science?

Thanks!

[Lisandro_P]

Well, as most things "hi-fi", the burn-in myth is mostly bullsh... lies But on the particular case of speakers, yeah, they'll change their sound after a while, and in that sense a burn-in period is not insane. There're a couple of reasons, like the cone loosing it's initial stiffness with time.

[bostarob]

The spyder and surround loosen with time. I don't know about the cone losing it's initial stiffness. After breaking in the suspension of a new woofer (best and most quickly done with a low frequency [20 -25 Hz] sine wave driven at a high enough level to generate signif cone motion for a while. Some say 24 hours. This can drop a woofers resonance enough so that a box designed before break in would no longer be optimal.
Your tweeter problem does not seem to be due to lack of break in. When you first got your speakers, did they hiss at you? Keep listening and see if they do break in. If not, you could either get a new tweeter for the left to match the right, because things have obviously been changed in the factory, or you could return the new tweeter because it has an audible defect. If neither works, buy new tweeters. (this introduces a host of other problems, crossover, attenuation, etc. However, it is certainly plausible.)
-andy

[Thatch_Ear]

Speakers with voice coils are mechanical devices. A period of break in is to be expected as in any other motor. Brightness in new tweeters is common. Leave it playing while you are away and hopefully a balance will achieved soon.

[Brett]

Take your new speakers and place them face-to-face, ie drivers towards each other, as close together as you can. Hook them to an amp with a signal source, with one speaker out of phase. FM interstation noise is as good a source as any. Leave them to play for a day or two at moderate volume. If the noise they make is too loud, a couple of heavy blankets over them and/or placing thm in a cupboard will reduce the level further.

Oh and using the best audiophile quality cables during break-in will make them sound more detailed with better sound staging.
(TPFIC)

Speakers and phono carts are the two devices with the highest level of break-in, because they are mechanical devices. TT's, CDP's may stabilise in performance, but it usually only takes a couple of hours. Amps when new, or have been stored for an extended period will change in performance over the first day or two as caps form etc, but it's usually minor and depends on the amp. I feel most break-in is psychological.

[sianturi]

Originally posted by Brett
Take your new speakers and place them face-to-face, ie drivers towards each other, as close together as you can. Hook them to an amp with a signal source, with one speaker out of phase.....

Now this is interesting....
Question#1: Why is the other one connected out of phase (reversing the polarity)?

Is this because the face-to face placement, ie: if L speaker move the air forward, the R speaker will move backward, so that air displacement doesn't destroy the conus?

Question#2: Why face-to-face?

To shorten the break-in time?

Thanks,

[Brett]

<b>Now this is interesting....
Question#1: Why is the other one connected out of phase (reversing the polarity)?

Is this because the face-to face placement, ie: if L speaker move the air forward, the R speaker will move backward, so that air displacement doesn't destroy the conus?

Question#2: Why face-to-face?

To shorten the break-in time?</b>

Tha answer to both questions is that it limits noise leakage during the break in process, because the sound from one speaker should cancel out the other. With them face-to-face and out of phase the net SPL from the pair should be zero. It won't be, but it will be reduced by 40+ dB, so you can have them in a room that's used, and still have them being driven quite hard, and the background noise level they generate should be quite low. I doubt air displacement would be able to damage the cones at any level possible in a domestic environment. Rear facing ports or drivers will still output some level so cover them with a blanket. Best idea of all, is to place them in a spare room/garage so they don't annoy anyone. The last pair of new speaks I bought (B&W 602 II) were so bright and harsh out of the box, I truly hated them. I put them in a spare room connected as I've said, using FM noise and music program alternatively for a week, 24/7, at about the same level I would use them at. They were different speakers afterwards, actually listenable.

HTH
Cheers

[tiroth]

Originally posted by Lisandro_P
Well, as most things "hi-fi", the burn-in myth is mostly bullsh... lies

Actually, electrolytics really do "burn in"...you'll often see this with people pushing the bleeding edge on their computer's clock speeds--"burn in" increases stability.