|Mitch's current system. Notice that Mitch is using the little ACA's powering the ultra-sensitive horns (JBL 2453H-SL compression drivers + 2384 waveguides) in his JBL Pro 4722 speakers. Notice the use of Crown XLS 1502 (525Wpc into 4Ω) for the dual 15" drivers on each side. Plus dual Rythmik F18 18" subs with 900W each for <50Hz frequencies!|
What is interesting is that I have had several lower distortion amps like the Purifi 1ET400A and active speakers like the Kii THREE and Dutch &Dutch 8c here. With the ACA’s running my HF compression drivers, I have not had any thoughts about distortion from the ACA’s as compared to those much lower distortion gear. But that is largely due to the efficiency of the compression drivers maybe requiring up to a couple hundred milliwatts of power. As Arch has alluded to, with that amount of 2nd harmonic distortion, this reminds me of tube sound. It has that “glassy” sound to the top end, which I am a sucker for. I know the objective measurements are not good, but listening to music, I don’t find anything really objectionable about the sound quality. So what if I like some sugar on top of my accurate sound? J
[I asked Mitch to discuss more about the protection capacitors he uses - I suspect this will be beneficial for folks to be aware of.]
With respect to protection capacitors, whenever a midrange or high frequency compression driver is connected directly to an amplifier, it is recommended that a capacitor be wired in series with the driver in order to attenuate any low frequency and switching transient signals, and to block DC components that can damage (expensive) compression drivers. Note that this is not specific to the ACA, but all amps connected directly to compression drivers. Safety first J.
I used a chart like this: https://www.markertek.com/attachments/ATS004711.pdf to determine the value of the protection cap. Best practice is to select a capacitor that is active at approximately one octave below the crossover frequency, assuring minimal acoustic interference with crossover region performance while maintaining a good degree of protection.