Bi-Amping Discussion

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11 hours ago, audiobomber said:

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Well designed passive crossovers use techniques that most people are unaware of. They think you can just replace a passive crossover with active fourth order slopes at some chosen frequency and that's going to be an improvement. In fact it will likely sound like crap, because of improper driver timing and no baffle step correction. 

What do you mean by "improper driver timing"? Phase errors or impulse-response errors or both?

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1 hour ago, audiobomber said:

I was thinking primarily of phase. For example, where the woofer drops by 6dB/octave due to its internal inductance, so a 2nd-order Butterworth is used with 3rd order on the tweeter for a final BW3 transition.  

But with a BW3 crossover HF and LF output will be 270 degrees out of phase at the crossover frequency and it introduces a group delay for the LF output. One could avoid/correct that with a digital crossover and a FIR filter. 

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10 hours ago, audiobomber said:

Yes, digital crossovers have an advantage there. But the point I originally made is that people who think they can simply use active LR4 crossovers and done are highly unlikely to achieve a good result.

Possibly. I successfully use an active LR4 for crossing my main speakers and sub, but I never tried bi-amping a tweeter and a mid/bass driver. I'd probably use something like a miniDSP for that.

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13 hours ago, audiobomber said:

I have one, but there's no way I'm going to run my main speakers through a miniDSP, the quality is just not sufficient. Their SHD Studio looks interesting though.

MiniDSP SHD Studio indeed seems to be the way to go. You will be stuck with the miniDSP's volume control though, which may or may not be a problem.

 

I suspect that the insufficient sound quality of the miniDSP 2x4 (HD) is mainly due to a lacking  implementation of the analogue output circuitry (power supply/voltage regulator/output stage). When this is done well, it could be used in principle as a quality preamp.

 

For example, I replaced the LM317 based voltage regulator circuit of my active Xkitz LR4 analogue crossovers with an LT3045 based circuit and the SQ improvement is remarkable. Best preamp/buffer I had sofar for my Schiit Vidar stereo power amp and KEF LS50 main speakers + active sub! And it also performs very good with a pair of JBL LSR305 active (internally bi-amped) monitors which rival the passive KEFs for a fraction of the price. The bass response with the JBLs may even be superior. The JBLs have the advantage of an ADC > DSP > DAC induced group delay of about 10ms which is approximately equal to the analogue LR4 induced low pass delay.  So impulse response of the JBLs and subwoofer are more in line and I think this is audible..