Speaker break-in is not an unusual question to see on any audio forum. Generally someone's bought speakers and they're trying to figure out if those speakers are really for them. There's a lot of issues that come into play here: positioning, calibration, effects of the room. Often the person who posted the question is somewhat inexperienced and hasn't done the best job of placing the speakers. Or perhaps they've just bought the wrong speakers (but they sounded good in the store!) for the room that they're going in. The purpose of this post though, is not to deal with those issues, deserving as they may be of an in-depth discussion.
This is about the issue of speaker break-in. Scientifically, the topic of speaker break-in has been studied rather extensively using techniques such as laser interferometry, measurements of speaker parameters, and controlled listening tests.
David Clark, an AES Fellow presented "Precision Measurement of Loudspeaker Parameters", which was published in the March, 1997. Abstracting from that paper is the following quote:
"5.1 Break-In"
"A break-in process is recommended. Drive-unit storage may cause the diaphragm suspension to drift away from its normal or in-use position. Break-in, with the drive-unit axis in the in-use orientation (usually horizontal), restores the normal diaphragm position. The recommended procedure pneumatically stretches the suspension to one excursion extreme, then the other and continues to alternate, decreasing the excursion each time until x is at zero. This process can be completed in less than 1 min."
Mr. Clark also indicated that drivers which had been stored face-up or face-down sometime need 1 minute of pink noise to restore the original center position. This could also be accomplished by a few strokes of the suspension which many manufacturers do routinely when the speaker is at the end of the assembly line. This suggests that most speakers, are in fact broken in when you get them.
Further work has been performed by Tom Nousaine who has measured speaker parameters pre and post break-in as well as having conducted controlled listening tests. He has found that the Fs of the speaker falls however that is offset by a rise in Vas. Both these parameters were related to the changes in compliance that occurred. During the playing or excercising if you will of the speaker both the spider and the surround become more compliant (they move easier if you will). Additional measurements on samples of identical drivers indicated that the changes that occured pre and post breakin on a single driver were smaller than the variations within a particular lot of drivers. Since there are manufacturing tolerances for drivers this indicates that whatever changes are that occur are smaller than those of manufacturing tolerances. This further indicates that the net effect of speaker breakin is nada, nothing, zilch, forget about it, etc.
In one experiment, Nousaine used a driver that was said to need 48 hours of break-in. Placing the driver in a 1.5 cubic foot box, he found the system resonance to be 53 Hz before break in. After 48 hours the resonance was 49 Hz. After a few minutes rest, the resonance had gone back to 51 Hz. The following morning it was back to 53 Hz. This indicates that whatever small changes that occur in a driver's characteristics during playback comeback to their original state after rest.
These experiments have been performed with other drivers such as from Dynaudio with similar results. Overall this indicated that whatever changes do occur, they do not change the sound quality.
Moreover, Richard Pierce, who some may know as having designed the crossovers for the Rockets, is a well known consultant and speaker designer who has examined the parameters and behavior of thousands, if not tens of thousands of drivers. His finding also concur with Clark's and Nousaine's with regards to how drivers behave in the real world.
So if the sound quality does not change in any significant way, what then does occur? Well listening adaptation would then have to be looked upon as a very strong reason for the perception of speaker break-in. Anyone who has spent time listening to audio systems or components knows their opinions with regards to the nature of the sound changes with time. In the case of speakers, when one buys them and brings them home, you become used to the sound of that particular speaker. That sound may grow upon you or you may find there's something that you don't like about it. Nonetheless, however they sound in your particular home, it'll be different from the way they sounded either in someone elses home or the stores where you heard them.
Now I've had a few emails that I've sent to various speaker manufacturers and these are some of the replies on this subject of break-in.
We've found (as have our dealers and customers) that the most significant changes occur within the first 75-150 hours, with smaller incremental changes occurring up to a few hundred hours. After that point, you shouldn't notice much change at all, as the speakers would be broken in thoroughly. This time is the same for each model and is best accomplished by just playing music through them.
Thank you for your interest in Revel.
Todd Sutherland
Madrigal