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TS Parameter changes during break-in

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  • #16
    Does the OP notice any subjective changes in the sound of the driver with his ear over the break-in intervals is what I want to know.

    Measurements don't tell the whole story in my opinion . . . they are just raw data that can support or reject the perceived sound changes.


    You have comments concerning the sound column missing from your spreadsheet, DeZZar.


    • #17
      Steve Lee honestly I didn't think of that - plenty of room for subjectivity of course - but in this case I have just got the driver on the test bench - it hasn't even seen the box its intended for. But I tell you what - I've only broken in this single woofer - the other one I've left in the box - just in case I screwed something up in my comparisons I could start over with a fresh driver - so what I can do is assemble the speakers without breaking in the second set of drivers and see if can report back as objectively as possible on any differences between them!

      Might be a little while before I can report back on that though as I still need to go through crossover re-design for these with the updated box/baffle design etc.
      Last edited by DeZZar; 07-29-2021, 03:42 AM.
      Constructions: Dayton+SB 2-Way v1 | Dayton+SB 2-Way v2 | Fabios (SB Monitors)
      Refurbs: KLH 2 | Rega Ela Mk1


      • #18
        I would be very pleased if you would add that column to your spreadsheet and give us your subjective & objective assessment of the 2nd driver as you break it in at the chosen intervals, DeZZar.

        Thanks for sharing your findings/skills and your projects, Sir.

        You are a great member here. (and generally a nice guy).



        • DeZZar
          DeZZar commented
          Editing a comment
          Thanks mate :D

        • Steve Lee
          Steve Lee commented
          Editing a comment
          You made it easy by being a good guy in delivering your message in a kind/helpful manner.

          Keep going - this world needs more like you and far less egotistical ***** that have apparently taken over the world - they actually number a very small portion of our population yet seem huge because they are so loud in their need to be relative like petulant children - spank them and move on with the productive people.

      • #19
        Alright 13 hours update and at this point we can already see the rate of change slow down completely.

        Click image for larger version

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        Vas, Mms remain the two that are quite different to manufacturer specs. Is it a a co-incidence these are also the two params most likely to suffer inconsistent calculations using the added mass and other approximation methods?

        Here's a couple of plot showing the change over time so far.
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        It seems apparent already that the greatest amount of change, for most items, takes place after just one hour of break-in. Definitely value in continuing on to 7 hours but very little change out to 13 hours.

        We'll keep going.
        Constructions: Dayton+SB 2-Way v1 | Dayton+SB 2-Way v2 | Fabios (SB Monitors)
        Refurbs: KLH 2 | Rega Ela Mk1


        • #20
          Since you've got a second driver it might be interesting to break it in like manufacturers do at the factory. If I remember correctly it's usually a band passed pink noise signal at rated power for 2 hours.


          • billfitzmaurice
            billfitzmaurice commented
            Editing a comment
            The vast majority of manufacturers don't break in drivers. At best they might run a signal through them for a few seconds to verify that they work.

          • devnull
            devnull commented
            Editing a comment
            Manufacturers break drivers in before they measure them for the published specs so it might be interesting to use an industry standard to break the driver in before measuring and comparing it to the published specs

          • billfitzmaurice
            billfitzmaurice commented
            Editing a comment
            If there is an industry standard for break in I'm unaware of it. Having been involved in developing a few OEM drivers from Eminence I'm aware that they do break them in before measuring the specs on the prototypes, and that they periodically pull drivers from the production line that they then break in and test to be sure they're within spec. They do that because they know from experience that their component suppliers sometimes change the components without notice.

        • #21
          (this is good stuff ...)


          • #22
            The relevant industry standards are AES2-2012 AES standard for acoustics - Methods of measuring and specifying the performance of loudspeakers for professional applications - Drive units and IEC60268 Part 5 Sound system equipment - Part 5: Loudspeakers

            Here's a quick summary of them

            AES break in period is implied from the section on power handling. The power handling section states bandwidth limited pink noise for 2 hours without significant permanent changes in acoustical, mechanical or electrical characteristics. The previous 1984 version of the standard specified significant as 10%. So if the characteristics of the driver aren't supposed to change after 2 hours then 2 hours is a reasonable assumption for the break in period of the driver.

            The IEC standard is more direct and has a specific section titled preconditioning. Preconditioning is simulated program signal(i.e. pink noise) at the rated power for one hour and then at least one hour of rest before further testing.
            Last edited by devnull; 07-30-2021, 01:27 PM. Reason: Because I'm an idiot and put AES twice instead of AES and IEC...


            • #23
              I'm an AES member, very familiar with AES2-2012. It deals with measuring, not breaking in. Nothing in it says that the specs cannot change after two hours, they just use it as a reasonable period of time to work the driver before taking a measurement. In truth drivers continue to break in almost indefinitely. One of the first drivers that I measured in 1983 was an EVM-12L. Out of the box the Fs was 60Hz. After an overnight break in it came down to the advertised 53Hz. I used that driver in a number of cabs over the years, measuring it again every time I put it in a new box. Every time the Fs had dropped a little more. The last time I did so, around 2001, Fs was down to 46Hz. Bass players are fans of old drivers, because they sound better with age. But that drop in Fs also results in a drop in high frequency extension, so guitar players tend to favor newer drivers, unless they don't care for a bright tone.


              • #24
                28 Hours in now. The final measurement here is with the driver going completely stone cold overnight. The others I had taken after a couple of hours cool down. That might explain some of the creep back up in Fs but its not significant. Re is consistent in any case so voice coil heat seems to be about the same - perhaps just compliance related.
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                After nearly 30 hours break in I cant see that things will change much from here. They will always continue to change throughout the life of the speaker but for design and modelling purposes I think one can draw the line here.

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                I don't know what most manufacturers or Dayton in particular would consider acceptable in terms of variance from specification but as you can see a number of these params are well outside of even a 10% variance.

                In terms of my design it does not make much of a difference. The designed application for these will hit 34Hz f3 in 27L and handle up to 30watts input for content down to 32Hz. If my VAS measurement is unreliable for any reason and it is in fact closer to spec, we'll hit 37Hz, same design but with a little less power handling.

                It's been interesting to document this and I might try it with a few other new woofers I have including some SB Satori's.

                My final thoughts/ponderings:
                1) Should the measurements really be taken with the speaker warm? After all once its in its box playing music it'll be warm....not stone cold?
                2) I cant imagine the type of signal used for break-in would really matter - its current and mechanical movement that achieve break in - not frequency?
                3) The equivalent 'break in' for a consumer set of speakers from a store must take....months?...of regular use...
                4) Should be obvious to most - but definitely don't build your custom designed speakers until you get the drivers, break them in and measure them. In this case if you had just used the manufacturer specs it wouldn't have been a disaster but it wouldn't be optimal. Fortunately I've worked with this driver before and have some already broken-in units on hand so I knew what to expect.
                5) What sort of variance should one expect in advertised specifications? Ironically this is Dayton's own woofers measured with Dayton's own measurement devise...
                Last edited by DeZZar; 08-10-2021, 12:49 AM.
                Constructions: Dayton+SB 2-Way v1 | Dayton+SB 2-Way v2 | Fabios (SB Monitors)
                Refurbs: KLH 2 | Rega Ela Mk1


                • #25
                  When the voice coil is warm other issues crop up, most notably a rise in DCR. Where home use is concerned it usually doesn't amount to much at normal listening levels. In pro-sound use at high levels the rise in DCR can result in power compression, which can reduce output by 6dB or more.

                  The break in source doesn't matter much, but I always use a sine wave well below Fs, for maximum excursion with minimal power, and if the driver isn't mounted it's also pretty much inaudible.

                  Break in of speakers by just using them may take up to 40 hours, depending on the material and level. It does not take the hundreds of hours that some manufacturers claim. The main reason for that bit of nonsense is that over time you do get used to the sound of a speaker, so one that sounds bad initially may not seem so bad after a few months. It also may encourage one to keep the speakers beyond the free return window, if there is one.

                  By all means don't finalize a design before breaking in and measuring the drivers.

                  A spec variance of +/- 10% is considered normal. After break in +/- 5% will have little effect on the result. As I mentioned Eminence does periodic spec checks. They can do that because they build their drivers in house. With sellers of sourced goods, like Dayton, it's not so easy to do. Even if they measured some from the initial batch 3rd party suppliers have been known to substitute everything from cones to voice coils without notice, hoping that no one else will notice.


                  • #26
                    As one can see from DeZZar's excellent work, the compliance of a driver changes based upon its use (Flexibility). Use it frequently or lose it.

                    Kind of like the human body as we age . . .

                    DeZZar - thanks for posting this stuff and please keep us updated - it is truly educational and fun to see.


                    • #27
                      What's the consensus on tweeter break-in? I'm assuming Pink noise with a high pass? Any other methods?

                      I was going to try two tweeters facing each other out of phase in an attempt to reduce the sonic impost of running a tweeter for a prolonged amount of time within earshot. Unfortunately I don't have a shed out the back where I can just leave them running for a while.

                      I'll 3D print up a little jig to hold them first.
                      Constructions: Dayton+SB 2-Way v1 | Dayton+SB 2-Way v2 | Fabios (SB Monitors)
                      Refurbs: KLH 2 | Rega Ela Mk1


                      • #28
                        Put them in your car wired as you suggest and put the battery charger on the battery with the ignition in ACC position?


                        • #29
                          Probably if they were in a sturdy cardboard box that would absorb most of the high frequencies.


                          • #30
                            Working with the SB tweeter now. A little more difficult as its so annoying to leave running in the house for such a long time. I 3D printed this little jig to hold the tweeter for measurements and to hold two of them facing each other so you can easily play them out of phase. Amazing how much the volume is cut down by doing this but it doesn't go completely silent. Still need to stick them in a box under a blanket lol. Tomorrow I'm going to try putting them in a cooler.

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                            Here are the initial measurements compared with 1 hour of pink noise.
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                            The Q's are all way off at this stage but Re and Fs are pretty well bang on.

                            I decided to also see what changes in frequency response and distortion could be seen during break in.

                            Here is the frequency, straight out the box and after 1 hour of pink noise.

                            Completely ignore the absolute SPL values - its not calibrated. Unfortunately I also forgot to take the initial measurement at 2.83v so this is really just showing relative change at this input level. (2.83 would just make it a little easier for consistent repeatability)

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                            I don't think much of a conclusion could be drawn from this yet - I want to say that it appears some areas have smoothed a little - but realistically for everything that's smoother something else is lumpier - so I would just say that response does change.

                            I thought a better indicator might be distortion but after one hour of break-in, interestingly distortion has actually increased across the spectrum. Not by much - you can see the percentages recorded in the data above for 1K, 2K, 6K and 10K (arbitrarily chosen points). 6K and 10K saw a respective increase in distortion of...errr....6 and 10% (total co-incidence). Here is the 1 hour distortion results.

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                            The distortion results surprise me. I expected these to immediately start heading in the opposite direction. I attempted to keep everything in the measurements as consistent as possible (mic distance, levels, mic gain, amp gain, etc etc).

                            Tomorrow I'll let these run for an additional 6 hours and retest and see where we land. Will post an update as soon as I can.
                            Constructions: Dayton+SB 2-Way v1 | Dayton+SB 2-Way v2 | Fabios (SB Monitors)
                            Refurbs: KLH 2 | Rega Ela Mk1