BlackbeardBen
1000+ Head-Fier
analogsurviver, quite frankly this sounds like used car salesman spiel - implying that this burn-in "method" is proven without actually showing that this is.
I understand your goal (lowering the driver fundamental resonance), but I have a few issues with that:
1. Why? Like xnor mentioned, with a low output impedance amplifier the damping factor is large and frequency response anomalies from the resonance are negligible. Also, the mechanical behavior of the transducer (its resonance frequency) is directly related to its electrical properties (the impedance of the transducer).
2. Regarding the phase shift: It should not matter in the slightest, as long as the channels are equal to each other. We are generally not very sensitive to absolute phase (See p.13 here thanks to the white hat, Dr. Floyd Toole of Harman), and without crossovers or rooms where phase alignment is not perfect, dispersion throughout the room is critical, and cancellation varies by frequency, it should not matter at all. I call B.S. on your claim about hearing a loss of imaging below the natural resonance frequency of the driver based on the phase shift - again, because that phase shift is inaudible or nearly inaudible.
3. How? You claim that exercising the driver - and in particular your "method" of doing so - will lower the resonance of the driver. First, I don't think we're talking about planar magnetic drivers because they're fundamentally similar to electrostatic drivers. So speaking about dynamic drivers, you believe that the driver's compliant portion will change its modulus of elasticity and/or damping by "exercising it - and that your method is better than others. Your method, if I read correctly, is that by exercising it at lower frequencies than its resonance will cause it to want to resonate at a lower frequency, right? And you has come up with a highly detailed process for doing so, yet again without any evidence for its efficacy?
My experience with materials (I am a mechanical engineer and I have done some graduate level studies of material behavior and failure) is that in a molded polymer object like a diaphragm will have residual stresses from the cooling process. That is, at rest the driver that will be under stress internally at varying levels at different points - and it is plausible that there are some very small points within the driver that are near yield stress - that is, the stress where the material will plastically (permanently) deform. During the first cycle of a transducer, such points near yield stress will exceed the yield stress and deform - breaking in. QC running the drivers, or the very first cycle you play of high-excursion notes (low bass, high volumes) will be enough.
As far as further cycles, fatigue failure of polymer drivers appears to be a non-issue, so I don't think that fatigue failure is a critical consideration here - though I can't prove it of course. That's a whole can of worms on its own too, as fatigue is not well understood regarding polymers and it can have very strange behavior characteristics.
I think the experimental results speak for themselves - there's little change over time. I just don't think there's even a theoretical basis for break-in beyond the first running of the driver.
I understand your goal (lowering the driver fundamental resonance), but I have a few issues with that:
1. Why? Like xnor mentioned, with a low output impedance amplifier the damping factor is large and frequency response anomalies from the resonance are negligible. Also, the mechanical behavior of the transducer (its resonance frequency) is directly related to its electrical properties (the impedance of the transducer).
2. Regarding the phase shift: It should not matter in the slightest, as long as the channels are equal to each other. We are generally not very sensitive to absolute phase (See p.13 here thanks to the white hat, Dr. Floyd Toole of Harman), and without crossovers or rooms where phase alignment is not perfect, dispersion throughout the room is critical, and cancellation varies by frequency, it should not matter at all. I call B.S. on your claim about hearing a loss of imaging below the natural resonance frequency of the driver based on the phase shift - again, because that phase shift is inaudible or nearly inaudible.
3. How? You claim that exercising the driver - and in particular your "method" of doing so - will lower the resonance of the driver. First, I don't think we're talking about planar magnetic drivers because they're fundamentally similar to electrostatic drivers. So speaking about dynamic drivers, you believe that the driver's compliant portion will change its modulus of elasticity and/or damping by "exercising it - and that your method is better than others. Your method, if I read correctly, is that by exercising it at lower frequencies than its resonance will cause it to want to resonate at a lower frequency, right? And you has come up with a highly detailed process for doing so, yet again without any evidence for its efficacy?
My experience with materials (I am a mechanical engineer and I have done some graduate level studies of material behavior and failure) is that in a molded polymer object like a diaphragm will have residual stresses from the cooling process. That is, at rest the driver that will be under stress internally at varying levels at different points - and it is plausible that there are some very small points within the driver that are near yield stress - that is, the stress where the material will plastically (permanently) deform. During the first cycle of a transducer, such points near yield stress will exceed the yield stress and deform - breaking in. QC running the drivers, or the very first cycle you play of high-excursion notes (low bass, high volumes) will be enough.
As far as further cycles, fatigue failure of polymer drivers appears to be a non-issue, so I don't think that fatigue failure is a critical consideration here - though I can't prove it of course. That's a whole can of worms on its own too, as fatigue is not well understood regarding polymers and it can have very strange behavior characteristics.
I think the experimental results speak for themselves - there's little change over time. I just don't think there's even a theoretical basis for break-in beyond the first running of the driver.