Have you considered pro audio digital crossover and DSP? Some are very clean. For example dbx 480 DriveRack is reasonably priced and very capable
Speaking of those external D.C. power supplies, how have you implemented them?
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Not familiar with Zapco but I don't want to buy another DSP. Curious therefore, did you compare miniDSP-HD with an active-analogue X-over ?
I have a mini-DSP-HD serving as a 2-way X-over but have not invested the effort to build an analogue version to try out instead (i.e. some transistors or op-amp)
I have a mini-DSP-HD serving as a 2-way X-over but have not invested the effort to build an analogue version to try out instead (i.e. some transistors or op-amp)
@Bigun
Not sure my anwer adds value to your case, but my experience is that miniDSP HD is a "good" DSP x-over. Its DSPing works well, but to me quite clearly the A>D and D>A sections can be done significantly better. So, what I am doing is to use the openDRC DI [which can quite easily be modified to support 4x4 by adding two wires and cut one trace) followed by Khadas Tone 1 DAC boards. If more than 2 Ways are wanted, a miniDSP nanoDIGI is a vialble solution of no FIR is needed. Regarding analog x-over: I'm not doing that at all anymore, DSP is just so much more flexible and faster in implementing changes to filters...
just my 2cents worth...
Winfried
Not sure my anwer adds value to your case, but my experience is that miniDSP HD is a "good" DSP x-over. Its DSPing works well, but to me quite clearly the A>D and D>A sections can be done significantly better. So, what I am doing is to use the openDRC DI [which can quite easily be modified to support 4x4 by adding two wires and cut one trace) followed by Khadas Tone 1 DAC boards. If more than 2 Ways are wanted, a miniDSP nanoDIGI is a vialble solution of no FIR is needed. Regarding analog x-over: I'm not doing that at all anymore, DSP is just so much more flexible and faster in implementing changes to filters...
just my 2cents worth...
Winfried
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Joined 2009
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It does seem a shame to go through multiple digital-analogue conversions. I am not really using the power of the dsp right now, it's set up with a simple 450Hz 6dB two-way. But I will use it to explore other options, higher slopes, and perhaps some EQ, to see what sounds best. I may not need a DSP.
Well yeah! Multiple A>D and D>A conversions are to be avoided, but transparency depends on A>D and D>A quality, though. To optimise tonality of a speaker your DSP may suffice, converting this into an analogue circuit, really doing the same clearly has its own challenges 
My sources are mostly digital anyway, so only the output signal of the Turntable RIAA equalized amp is A>D converted by a dedicated board, the rest of the chain is digital, DSP x-over & DACs are located in the speakerboxes and directly feed the power amps.
Greetings,
Winfried
My sources are mostly digital anyway, so only the output signal of the Turntable RIAA equalized amp is A>D converted by a dedicated board, the rest of the chain is digital, DSP x-over & DACs are located in the speakerboxes and directly feed the power amps.
Greetings,
Winfried
Room correction can be a problem.
Always correct is measuring the loudspeakers and linearize them correctly in frequency and phase response.
If in the bass some correction is necessary because of the room I would do it separately.
Easiest are fullrange drivers to measure and adjust: they can be measured in the near field (=less than 50cm to the box, 20 to 30cm is ideal).
Multi ways are more difficult to measure.
For a fullrange a minidsp 2x4 with only iir is enough.
Always correct is measuring the loudspeakers and linearize them correctly in frequency and phase response.
If in the bass some correction is necessary because of the room I would do it separately.
Easiest are fullrange drivers to measure and adjust: they can be measured in the near field (=less than 50cm to the box, 20 to 30cm is ideal).
Multi ways are more difficult to measure.
For a fullrange a minidsp 2x4 with only iir is enough.
@Freedom666
Agreeing to most what you say, in my experience IIR filtering can/will suffice in most cases, FIR filtering (in particular a phase/group-delay linearization) adds the "icing on the cake" if the rest of the chain matches in performance.
While the plain miniDSP 2x4 (without HD) did the filtering job (i.e. the DSP part) well in my case, it otherwise did not hit the "HiFi mark" for me (i.e. ADC and DAC wise). Now that was to be expected given the low budget for it. But a decent full range driver deserves as decent ADC/DAC DSP performance and will then reward with according overall high fidelity!
Greetings,
Winfried
Agreeing to most what you say, in my experience IIR filtering can/will suffice in most cases, FIR filtering (in particular a phase/group-delay linearization) adds the "icing on the cake" if the rest of the chain matches in performance.
While the plain miniDSP 2x4 (without HD) did the filtering job (i.e. the DSP part) well in my case, it otherwise did not hit the "HiFi mark" for me (i.e. ADC and DAC wise). Now that was to be expected given the low budget for it. But a decent full range driver deserves as decent ADC/DAC DSP performance and will then reward with according overall high fidelity!
Greetings,
Winfried
I have 3 active XO's. I have one made from the Marchand XM boards, One made from early X Kitz boards and a Peavy 18db unit that is an early one with a linear PS. The Marchand is the best of those however it really can not compare to the 48db xo and its ability to do delay for driver offset. Using the LR 24 digital vs the Marchand it is evened out a bit however there is a significant character that the analog XO's have that seems to be dominated by the caps used to create the filter. The Marchand has plenty of room so I did experimenting a while back on that and it was quickly becoming a monster with caps dwarfing the pcb and the PS. I am president of the Las Vegas Audiophile society and we have as a member Noel Lee. Noel is the father of Monster, as in Monster Cable. At the last meeting he showed his new Klipsch Jubilee's that he is doing DSP on. He is working on the DSP via a car audio centric system that really perked my interest and I have started down that rabbit hole now. Been sick w Covid 2x this fall and just getting back to things. The Mini needs the right Opamp as it has about half the supply voltage as the PRV and I feel that is a major limiting factor with that system.
I have been sick 2x this fall which set me back massively of free time but hope to resurrect this thread as I really am super pleased with where I have been heading on this venture. I have also started down a parallel rabbit hole with car audio based DSP's and there is a whole plethora of products there since it seems to be massively more popular in those installs. A local audiophile friend Noel Lee ( the Noel Lee who started and owns Monster Cable) introduced me to the car based units after I mentioned the PRV. We are getting samples from China soon.
On to what I did/ discovered:
The first thing one needs to do, even before mods is get the input levels right. You can set the levels in the interface however if you are not using a tape loop type of setup that sends full signal level ( pre out to power amp) then it can suffer a lot and I suggest setting your pre amp to a higher volume level and compensate in the interface. This is even more important for the car audio based stuff where line level is 4 to 9v!
Mini DSP 2x4HD Bypassing. I also suggest a linear PS. I have several from AliExpress that sound excellent. The AD chip and DSP chip are well bypassed locally underneath to the ground plane and I am surprised that the big Oscon had the effect it did but it was a large improvement. I used 330uf 6v units. Looking at the overall circuit there is not any large capacitance after the regulators, only local bypass so that may be part of the reason for improvement.
On to what I did/ discovered:
The first thing one needs to do, even before mods is get the input levels right. You can set the levels in the interface however if you are not using a tape loop type of setup that sends full signal level ( pre out to power amp) then it can suffer a lot and I suggest setting your pre amp to a higher volume level and compensate in the interface. This is even more important for the car audio based stuff where line level is 4 to 9v!
Mini DSP 2x4HD Bypassing. I also suggest a linear PS. I have several from AliExpress that sound excellent. The AD chip and DSP chip are well bypassed locally underneath to the ground plane and I am surprised that the big Oscon had the effect it did but it was a large improvement. I used 330uf 6v units. Looking at the overall circuit there is not any large capacitance after the regulators, only local bypass so that may be part of the reason for improvement.
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I have cap coupled power amps so I decided to check for DC offset and see if I could bypass the ceramic output caps. I got .001vdc on the active side of the ceramic output coupling caps which is close enough to 0 for me with amps that are already cap coupled. Make sure any tiny DC offset is not going to be an issue with your amps before bypassing the ceramic output caps. I just removed them, put a bare wire across the pads and soldered it in place. You can also see the opamps on the underside. I did adapters to DIP8 sockets on the PRV and its just not possible to do the adapters to change out opamps on the Mini so it's live with them or use a hot air station and change them out. I personally like the AD8599, AD8066ARM and LME49860 however the LME is optimized for higher supply voltages and that is what I am using in the PRV.
As a teaser here is the interface for the car audio based DSP's. The units with Ti DSP chip as well as the Cirrus DSP chips both share this 31 band PEQ interface with time delay and XO's for each channel, all XO slopes up to 48db are available as well as all 3 of the common alignments. They also support auto correction via mic! Noel Lee is using the Audio Dynamics setup ( same software interface) however they all seem to be made in China by a few manufacturers that I found on Alibaba. Several have amplifiers integrated using the TDA3116D2 class D chips and some are chip amps. I will post the PRV mods over the weekend.
FYI, the Nichcon output (electrolytic) capacitors have really good distortion performance. In this application they're perfectly fine and needn't be removed.
You most likely have much worse offenders in your signal chain regards series capacitors.
An upgrade might be something in the Panasonic bipolar selection. (But even that would marginal.)
Dave.
You most likely have much worse offenders in your signal chain regards series capacitors.
An upgrade might be something in the Panasonic bipolar selection. (But even that would marginal.)
Dave.
Dave,
it has been my experience that electrolytic capacitors don’t sound that great when used without a bias voltage. In this application, there is such a tiny amount of bias voltage that it’s clear that they just put these here as protection, in case, something fails versus having to block DC offset in the circuit.
Nevertheless, there is a clear boost in sonics when they are removed from the circuit. With that said, the input cap has a bias voltage and should not be removed. I bypassed the input caps with styrene caps which opened up the hf a touch. Unfortunately, there’s just not much space inside these to do high-end or exotic parts/capacitors, etc..
it has been my experience that electrolytic capacitors don’t sound that great when used without a bias voltage. In this application, there is such a tiny amount of bias voltage that it’s clear that they just put these here as protection, in case, something fails versus having to block DC offset in the circuit.
Nevertheless, there is a clear boost in sonics when they are removed from the circuit. With that said, the input cap has a bias voltage and should not be removed. I bypassed the input caps with styrene caps which opened up the hf a touch. Unfortunately, there’s just not much space inside these to do high-end or exotic parts/capacitors, etc..