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Showing content with the highest reputation since 06/13/2020 in all areas

  1. 2 points
    The 1kv to ground sounds very weird as even if the heatsink was live on purpose you wouldn't expect 1kV to be generated anywhere in the amp. Mix of output transistors is a very bad idea as they won't share current effectively. On the plus side this is making me very certain I don't want one of these amps in my life
  2. 1 point
    Any small issue with glue or primor can lead to failure. Its a bit tricky and takes precision. Hopefully Eminence can get those fixed for you
  3. 1 point
    This is so annoying. I was just way too curious to see if I could improve the amp's performance by adding those components and now I caused 150$ damage again. Well, heres more random info on the PSU: when both amp stages are disconnected, the PSU hold over 200V for an hour. I used a light bulb to quickly drain it. When it's down to 0.1V, it takes about 10 seconds to climb back to 2V. I immediately connected the 230V light bulb after I powered the amp off, when the PSU was still at around 350V from positive to negative. It was a 30W light bulb or smth, it lit up brightly for a second and the light faded completely after some 20 seconds. Very convenient way when you're working on this kind of stuff.
  4. 1 point
    Art clean box pro will convert the single ended signal from your phone to balanced signal with gain. I did some measurements /modifications on mine to improve LF response: https://www.diyaudio.com/forums/analog-line-level/329210-art-cleanbox-pro-low-freq-modification.html
  5. 1 point
    @SMEI've been looking into getting a miniDSP to better fine tune my sub, so your recommendation for a HPF to protect the driver will move that decision along. I have a tone generating app that I used to do the test you suggested to find the tuning frequency. It appeared to be about 21-22Hz. By 18Hz the cone was moving quite a bit again. I was shooting for 20Hz, so it will be interesting to see what it actually is, when I do measurements with REW. Listening impressions - During the build I tried to give my wife an idea of what to expect from the new sub. It was always a difficult topic, because I wasn't completely sure what to expect. But now that it's playing in my living room, the new sounds I'm hearing are a little easier to describe. Both music & movies are dramatically different. With music there is a "presence" of bass that can't be ignored. It's not totally volume, but rather how the bass now seems to fill the room. As the bass line gets lower there is no obvious reduction of volume which, of course, makes it louder in the lower frequency ranges & that increase in volume comes with an increase in chest-thumping vibrations. Listening to music is a much more visceral, immersive experience now. Even at moderate volume the ability of the sub to reach down & hit the lowest notes with authority is impressive. Movie viewing has been radically changed - especially action movies with Dolby Atmos soundtracks. However refined & musical it's capable of being, start Mad Max Fury Road & it becomes a sledgehammer - seriously rocking us during explosions. The ability to reproduce loud explosions, gunshots or car crashes is stunning. The sub never seems to be pushed anywhere near its limits - even when the soundtrack is as loud as I can stand (the ultimate measurement of the volume capability of your system - it's louder than you can listen to it) . I don't want to sound too giddy, but I'm more than pleased - I'm thrilled.
  6. 1 point
    Interesting. I wonder how fine-grained the IPAL system is here? Does it adjust EQ in real-time or just gain? If it adjusts EQ, how tight is it? Do the sound characteristics noticeably wander through a live performance? It's not too hard to monitor DC resistance and adjust gain in real-time, but that may not be good enough. I expect that thermal changes manifest over seconds to minutes or hours. If we assume all of the thermal effect is to raise the coil DC resistance, then the nature of the non-linearity is such that we can understand things in terms of linear response that changes with time. This is not possible for inductance because inductance can fluctuate much more rapidly, with each stroke of the driver. Using a linear analysis, we consider a sine wave at one single frequency at a time. The impedance (Z) describes the relationship between voltage (V) and current (I), and we can describe the behavior completely if we let V, I, and Z be complex quantities with *real* and *imaginary* parts. Each quantity can alternatively be described as having a *magnitude* and *phase angle* part. Both descriptions are useful depending on the circumstances, and one can convert between them using arithmetic formulas or geometry. A complex quantity can be represented as a point on a 2D X/Y with x = *real* and y = *imaginary* parts. Draw a line between this point and (X=0,Y=0). The magnitude is the length of this line and the phase angle is the counter-clockwise rotation from the positive part of X-axis to the line. (This article on the Complex Plane might be helpful.) For V and I, the magnitude is the absolute value of the peak amplitudes of their oscillations. The phase angle describes the *phase shift* which essentially describes the temporal shift while recognizing that a continuous sine wave is *periodic*. Periodic means it precisely repeats at the same interval. If you shift a sine wave by exactly 1, 2, 3, etc. periods, the result is exactly the same. So, it makes sense to represent the amount of time shift as a *phase rotation* on a circle. Analogously to Ohm's law, the relationship at a single frequency is: V = I * Z or (rearranged) I = V / Z or (...) Z = V / I. The rules for multiplication/division of two complex quantities are as follows: (1) multiply/divide the magnitudes to get the new magnitude. (2) add/subtract the phase angles to get the new phase. Therefore the meaning the impedance phase angle is the phase difference or change between V and I. Note that this math is generally useful for analyzing oscillating signals including audio acoustic transfer functions (i.e. frequency response magnitude/phase). So if we can easily multiply and divide complex quantities using the magnitude/phase description, what is the purpose of the real/imaginary description? The latter is for adding subtracting such as when analyzing a series electrical circuit or acoustic interference effects. The rule for adding and subtracting complex quantities is to add and subtract the real and imaginary parts independently. For impedance, the *real* part is called the *resistive* part, and the *imaginary* part is called the *reactive* part. As expected, a pure resistance (i.e. straight a wire) contributes only to the real/resistive part of impedance, and the tendency for oscillating energy storage/release manifests only in the reactive part. Ideal (as in zero resistance) capacitors and inductors only contribute to the reactive part. Do note that the resistive part of the impedance is not always equal to the DC coil resistance. The acoustic properties of the subwoofer contribute to impedance (both resistive and relative) as well. As such, we can conclude that increasing the DC resistance by heating the coil will alter the frequency response by different amounts depending on both the magnitude and phase of Z. The increase in Re adds directly to the resistive part of Z. The peak current is reduced, but the amount of reduction depends on how much the *magnitude* of Z changes. So you can plot the initial value of Z on the Complex Plane and then plot the *new* Z shifted to the right by the increase in Re. Then, the current will decrease in inverse proportion to the change in distance between each point and (x=0,y=0).
  7. 1 point
    18Sound have some interesting drivers that have little/no inductive impedance rise using a technology they call AIC: http://www.eighteensound.com/media/W1siZiIsIjIwMTgvMDkvMTAvMTFfNDZfMDNfNzU1X0FJQy5wZGYiXV0/AIC.pdf http://www.eighteensound.com/en/products/lf-driver/10-0/8/10NMBA520 I think KV2 might be using their drivers.
  8. 1 point
    I will try to explain as best I can here. Shorting rings don't act mechanically, at least not directly. They magnetically interact with the voice coil to reduce and/or linearize inductance through the driver's stroke. The voice coil is a natural inductor. Inductors store and release energy via the magnetic field in their proximity. For a straight wire with pure resistance, the current responds in perfect lock-step to changes in voltage. If an inductor is subject to a sudden increase in voltage, however, some time and energy are required for the current to "spin up" the magnetic field. At that point, if the voltage is suddenly cut to zero then the current flow continues for some time while the magnetic field "spins down" and releases stored energy. Hence, rapid fluctuations in voltage tend to be smoothed out in current, e.g. high frequencies are reduced. This is a major cause of high frequency loss and sometimes "humping" in a speaker driver's response. At the same time, the inductance itself is likely to vary, not just with frequency but with changes in instantaneous current and/or driver stroke. This is *non-linear* behavior, which causes distortion, including inter-modulation distortion, which may be particularly undesirable. Though the linear aspects can also be degrading if not precisely corrected with EQ. The response "humping" alters the spectral balance and likely imparts a non-neutral characteristic sound. A shorting ring is made from a material that is both magnetically and electrically active. The magnetic field generated by the current induces current flow within the ring. The ring "shorts" this current to the rest of the driver assembly, allowing some of the energy in the magnetic field to be transferred to the shorting ring and dissipated as heat instead of stored. If designed correctly, this effectively reduces the inductance of the coil), and depending on the position of the rings vs. the voice coil, may also keep inductance from fluctuating as much throughout the stroke. The relationship between inductance and damping is via the electrical impedance. Impedance is essentially a 2-dimensional quantity which can be described in terms of a pair of parameters: either *magnitude* and *phase angle* or *real* (resistive) and *imaginary* (reactive). Inter-conversion is possible via basic trigonometry; see the "Complex plane". Damping is a property of the resistive / dissipative (non-energy storing) component of impedance. Pure inductance and capacitance both contribute only to the reactive (energy storing) component of impedance. Speakers using a composite electrical circuit that has effective resistances, inductances, and capacitance contributed by several different factors including the mechanical and acoustic properties of the system. So needless to say, inductance and "damping factor" both contribute to the system behavior in a way that's not simple to describe. To answer your last question: No. I mean, if the resistance of your speaker wire is high enough be a problem in the absence of shorting rings, then shorting rings probably won't fix that problem.
  9. 1 point
    Yep...The 21 Klippel data is from Eminence. I would've preferred to see it done by RedRock but a lot of the time RR seems to cut the data capture off before a long stroke driver is really pushed. They don't seem to ever go past 15mm so the data may not have been as indicative. The Eminence data certainly looks great. The Xmax based on the Klippel defined limits for subs is almost 19mm based on all 3 criteria. I was surprised by the suspension behavior. I knew the spider choice and arrangement was good but I thought the triple roll surround would start to tighten earlier.
  10. 0 points
    Yes, it happened to me with B&C drivers . You will find my video on YouTube
  11. 0 points
    https://drive.google.com/file/d/1-fUDVjQIgSk6yMSriJNTysL_wo4IN-vJ/view?usp=drive_web Surround isn't glued perfectly to the frame as I can decrease the noise by putting pressure between the outer roll and gasket. This is the worst out of four. Two are fine, one is very slight, and this one is noisy. The low frequency noise is clipping in the signal. Seems this was an issue with several drivers from other manufactures as well.
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