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Jabber

Found 2 results

  1. I am new to active crossovers, new to using REW to test speakers and Klipsch speakers. So I am hoping someone with more knowledge can "look over my homework" to make sure I am on the right path. @Chris A or anybody else with active speakers or familiar with active crossovers, I would be happy for y'all to look at driver graph and then see if crossover points are correct. This is a tri-amp setup via 2 MiniDPS 2x4HDs (one doing left channel and the other doing the right) with 3 AIYIMA A07 amps. While I am not overly familiar with REW, I have watched a few videos on how to use it to measure your speakers. Scott Hinson has video on how to measure each driver and I tried to follow his steps to get my response graph for each driver (1v @ 1m because I have neighbors). While it may not be perfect since I could not take my speakers outside to measure each driver, I think they are close. Then again, I maybe fooling myself, which is why I am hoping someone can look this stuff over and tell me I am all wrong or on the right track. Lastly, I attached 4 MiniDPS settings "screens". The low pass, for the woofer, the band pass for the squawker, and the high pass for the tweeter. The 4th is the time delay that I derived using the tech paper that MiniDPS posted on measuring impulse response to time align your drivers. There is no delay for the woofer, a 2.8ms delay for the squawker and a 4.45ms delay for the tweeter. I have tried to verify these settings and there is still a few uSeconds of variance between all the drivers. If I change the delay on the tweeter, the impulse either fall just in front or just behind the squawker--I can't seem to get them to align perfectly. This could be because: I am not familiar enough to using REW to measure the impulse correctly OR I think I am hitting the delay resolution of the MiniDSP OR I could just have totally messed up the original impulse response measurement and these number of nowhere remotely correct. So fi these delay settings seem incorrect, I would be happy to revisit them. With all this said, they still sound a LOT better than it did with the original AA crossover. So I think I am on the right track. Thanks!
  2. Looking at the Active Bi-Amping/Tri-Amping FAQ, it was stated: This thread will provide insights and listening experiences on using solid state (SS) amplifiers for bi-amping and tri-amping, and the reasons for the disproportionate increase in sound quality (SQ). Let's start with the most obvious reason: 1) The reduction in the load that each amplifier drives. For example, it has been noted the there is an average power split between bi-amped loudspeakers based on the crossover frequency chosen, with the 50-50 power split frequency close to the 350 Hz band. If you bi-amp with a crossover point around 350 Hz, then you can expect to need only half the rated output power for each bi-amping amplifier. This is a real advantage for the low-wattage amplifier crowd, including tube/valve amplifiers and chip amps. By bi-amping, even sub-watt amplifiers can drive their loudspeakers to higher SPLs without accompanying distortions produced by each amplifier. Since these lower power amplifiers often cost much less than higher power amplifiers, the economic advantage of bi- or tri-amping becomes more attractive. If Tri-amping, the audible spectrum (i.e., 20-20,000 Hz) can be broken into three parts, with each amplifier requiring, on average 1/3 the output power to produce the same loudspeaker output SPLs. 2) The elimination of amplifiers driving unnecessary resistive and reactive loads that passive crossovers introduce. This usually isn't talked about by the "old school", especially by those that otherwise "distrust" active crossovers, since it isn't pleasant to talk about when defending passive crossovers. . It isn't a secret that real-world acoustic drivers all have resistive and reactive characteristics. What's not discussed is how much more resistance and reactance is added by the passive crossovers. In some cases, the added resistance and reactance is greater than the drivers themselves. If you look at the older passive crossover designs used by Klipsch on it's Heritage loudspeakers (particularly the Khorn), you will see impedance swings from 4.2 to 43 ohms on the frequency vs. input impedance curve: Direct-coupled amplifiers are amplifiers that do not require an output transformer to couple to the loudspeakers without presenting a higher amplifier output impedance to the loudspeakers than the loudspeaker's input impedance. Solid state amplifiers are typically direct coupled amplifiers--with noted exceptions. SS amplifiers lose many of their advantages when driving loudspeakers with high levels of load reactance, of which unnecessary contributions are generated by passive crossovers. Direct coupled amplifiers "like" resistive loads. Most of the output power stage design differences between typical Class AB and Class D SS amplifier designs lie in how the amplifiers are designed to handle complex and non-linear reactive loads. By minimizing load reactance by direct coupling loudspeaker drivers without using passive networks, the amplifiers themselves can do a better job of faithfully reproducing the music via the loudspeaker. Driving highly reactive loads contributes negatively to the resulting sound. Additionally, the amplifiers in a bi-amp or tri-amp configuration are not driving any parasitic resistive loads that simply dump a significant fraction of amplifier output to heat: all the amplifier's output is going directly to the drivers themselves - direct coupled. 3) Reduction of modulation distortion (FM and AM), transient intermodulation distortion (TIM, i.e., "slew rate" distortion), and zero-crossing distortion via separating low frequency/high amplitude signals from high frequency/low amplitude signals. Much of the discussion centering on amplifier "classes" (A, B, AB, C, D, etc.) is tightly coupled to non-harmonic distortion types, including modulation distortion, transient modulation distortion (TIM, otherwise called "slew rate" distortion, loudspeaker impedance-coupled frequency response distortion, zero-crossing distortion (i.e., higher-order harmonic distortion) and clipping distortion (higher-order transient harmonic distortion). The objective of using the different types of amplifier classes or architectures is the avoidance of these type of distortions, not the introduction of any them into the signal path. By separating low frequency/high amplitude signals from higher frequency/lower amplitude, better choices for amplifiers of differing classes and strengths/capabilities can be used. For instance, amplifiers of very high slew rate (low TIM), low intermodulation via fewer gain stages and lower levels of feedback can be direct coupled to the HF drivers that typically exhibit capacitive reactance , while high output current/voltage low output impedance amplifiers can be direct coupled to the LF drivers, drivers that often exhibit large relative amounts of inductance reactance. Additionally, it is well known that LF drivers are usually much less efficient than HF drivers, such that output gain matching can be accomplished by the amplifier gain controls or the active crossover without resorting to increasing impedance or resistance in the signal path to pad down the HF drivers. This last point (reduction of non-harmonic distortion levels) using bi-/tri-amped amplifiers of differing types that are individually more optimal for driving the their respective loads at lower overall non-harmonic distortion levels -- is the greatest single advantage that is achieved via active bi-/tri-amping. This aspect of bi-/tri-amping is also the one that receives the least visibility and understanding, and that likely makes the largest difference in the sound quality improvements over typical passive crossover - single amplifier/loudspeaker configurations. Chris
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