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Active Bi-Amping/Tri-Amping FAQ


Chris A

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On 11/17/2017 at 11:21 AM, Wim M said:

Maarten,

 

Think of it this way: if jou want to build a nice house,  you need a strong foundation.  Well, the Xilica is part of that foundation,  you want it to be right from the first time.  

It's okay to wait a while to get the money saved, I guess that's what most of us do.  As we say in Belgium: "Rome wasn't built in a day"

 

Wim

The Yamahas are just as good as Xilica. I have both.

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I've found that the Xilica XPs are quieter quiescently than the Yamaha SP2060, but both brands are excellent crossovers.  I used the Yamaha on the Jubs for a couple of years until I replaced it and a couple of Dx38s with one Xilica XP-8080 for my main setup (5.1).

 

The Yamaha is now my system set-up/test unit--and I also have a pair of Khorn clones (Shinalls) in the study that will likely inherit the Yamaha in the future, to tri-amp them and correct the various time misalignments and frequency response.  The Yamaha is a really solid crossover and it has a digital AES/EBU input in case I want to try that out, i.e., digital only from the source up to the input to the power amplifiers. 

 

The Xilica XD series also have AES/EDU inputs and FIR filter capabilities but the price rises about $1k over the XP series.  etc6849 (Ellery) is using a XD4080 in his setup...mentioned above.

 

Chris

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The specs on the Ashly Protea processors I have don't match the Xilica but they sound excellent as well.  I have not been motivated in any way to replace the Ashly's.  But I really do like the Xilica performance, the quiet background, and especially the PC tools it comes with.

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9 hours ago, Droogne said:

Have been wondering about this for some time, would the Xilica DCP series also work?

Hey Maarten,

 

I’ve seen several xp4080s on 2ehands, and it appears there ‘s little interest in them.

 

Wim

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1 minute ago, Wim M said:

Hey Maarten,

 

I’ve seen several xp4080s on 2ehands, and it appears there ‘s little interest in them.

 

Wim

There is a Xilica DCP3060 on Marktplaats for only 175, so I could buy this one and sell my Behringer. That way I lose no money and end up with something better. The DCP does seem to have everything I would need.. Also I the xp4080 go for way to much for what I need it right now. I already bought an OEM version of the Xilica XP4080, and as far as I can tell it's genuine. Not sure about the quality.. I would need to some kind of test, but not sure what. 

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ChrisA.  If I remember correctly, you have offered to help people set up their digital crossovers in the past.  If you are still willing to help, I would love to take you up on that offer. 

 

I am using a MiniDSP4x10HD.  I have a THT sub, La Scala bass bins (with K-43s), and a B&C DE750TN 2" driver on 11x17 ZXPC horn.  I am no longer using a tweeter above this.

 

Using REW, here are the measurements I have taken of each driver (with 1/6 smoothing).  These were taken 3 ft from the speaker mouth, except the sub curve, which was measured at the listening position.  I think this is the data that would be needed to set up a digital crossover, but I am new to this.  I got an initial setup going that sounds pretty good (amazing actually), but I would love to get your input, as you are much more experienced in these matters.

 

3ft Measurements.jpg

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I saw some guys selling their Xilica XP 4080, because they are upgrading to an XD model.  I know that the difference between the two models is that the XD models have FIR filters.  Did some research on FIR filters but I think it is still a bit over my head.  So, without going too much into technical detail, is there an audible difference between the two (XP vs. XD) that is worth the trouble of upgrading?

 

I use an XP 4080 on a pair of bi-amped La Scala IIs and a pair of THT subs, should it make sense to use an XD model on this setup?

 

Wim

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etc6849 (Ellery) has reported on the Xilica XD crossover, and has mentioned that it has a FIR filter limitation (i.e., no lower than frequency) is 500 Hz.  The lowest frequency that a FIR filter can go is determined by the length of the number of "taps" in the filter's settings.  Lower frequency = more required memory.

 

What he said was the real difference was the digital input (AES/EBU) that bypasses the digital-analog-digital sequence out of the preamp into the DSP crossover, instead supporting digital all the way.  The real kicker, however, is that you need a preamp output of AES/EBU.  Ellery found this one which is PC-based.

 

Chris

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Here are the specs of the DCP3060. Anyone any experience with this unit, or some insights based on these specs? Looks like the exact specs of XP series. It does seem the DCP is an older series, and that the price was lower than the XP series now. 

 

EDIT: I see some differences, the XP series has a "Super" instead of a "High Performance 24-bit", and the XP also has a 40-bit floating sampling rate instead of 32-bit (40-bit ext). 

image.thumb.png.af0cce4ffabd10fab9e7da49bfbe2151.png

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On 26/3/2018 at 9:50 PM, Tarheel TJ said:

ChrisA.  If I remember correctly, you have offered to help people set up their digital crossovers in the past.  If you are still willing to help, I would love to take you up on that offer. 

 

 

 

Yeah, Chris helped us too.  I'm still trying to figure out how he came to his results based upon the measurements I sent him.  The only thing I can say is that our LSIIs sing like never before since Chris' results are loaded in the Xilica.  @Chris A, big thanks!

 

Wim

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If you can find a used XD4080, I would go for it over the XP4080.  I would also try calling Acoustic Frontiers and haggling on a new one too.  The one's I bought from him were well below retail (somewhere between 1400-1600), but he is a nice guy and gave me a decent price compared to any pro audio online place I tried.

 

I use the Xilica XD's FIR feature for the LF/MF/HF and wouldn't go back.  You are limited on taps (they change the slope of the FIR), but there are plenty of taps for my speakers and keeping distortion below .2% at the listening position and at 90dB.  This compares with some of the worlds best headphones in terms of distortion, but magically my speakers are 7 feet away where as Focal beryllium driver is an inch from your ear.

 

It is 100 times easier to get great sound when setting up FIR filters.  I played with a lot of different filter types, but FIR won hands down and I really believe I hear a difference.  Not distorting phase is a huge plus for FIR filters.  Someone really experienced like Chris can no doubt get a setup sounding great without FIR filters and get a very nice looking phase, but he has read a lot and spent a lot of time to get there and is one smart dude.  I was immediately happy with FIR and the results measured very well with less phase wrapping in the REW plot versus what I could do with IIR filters.

 

On 3/27/2018 at 8:48 AM, Wim M said:

I saw some guys selling their Xilica XP 4080, because they are upgrading to an XD model.  I know that the difference between the two models is that the XD models have FIR filters.  Did some research on FIR filters but I think it is still a bit over my head.  So, without going too much into technical detail, is there an audible difference between the two (XP vs. XD) that is worth the trouble of upgrading?

 

I use an XP 4080 on a pair of bi-amped La Scala IIs and a pair of THT subs, should it make sense to use an XD model on this setup?

 

Wim

 

 

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Some pics of my new PC case.  I'm using this rack for tri-amping my C, FL and FR, and also crossing to 5 subs that are individually time aligned and level matched.

 

The PC case didn't do anything for sound, but sure looks nice.  I highly recommend everything else in the rack though because the amps and processors did improve my sound and measurements over the consumer gear I had before.

 

Front.jpg.2729942fac454bbad0445a081c5ec22f.jpg

 

 

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I certainly have nothing against FIR filtering--in fact, the only downside is a little added delay, but usually not anything that can't be handled (vis-à-vis loudspeaker channels not using FIR filtering in the same setup) with a preamp or other DSP means to balance the delays.  FIR filters are the only ones that allow the user to simultaneously control amplitude and phase at the same time, and phase-coherent loudspeakers are a big, big deal in terms of what your ears tell you is "better". 

 

Once I get through the near-term MEH stuff and get a handle on Class D amplifiers to simplify my amplifier rack (hopefully reducing the need for class A amplifiers that heat the room), I intend to turn my attention to exactly what Ellery has done above and replace my preamp processor with the PC-based system that Ellery is showing. I've got to make sure, however, that my significant other can also run the system if I'm not here.  So that will be an additional capability (i.e., simplicity of operation) that I have to achieve at the same time.

 

Chris

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By the way, one reason why I highlighted the 500 Hz minimum frequency thing: the MEHs that I plan on using (5 surround channels) will have one compression driver covering 500-20000 Hz, so phase correction of this band isn't really required.  The only thing that is required is paying attention to the phase shifts in the crossover filters, and the use of Bessel crossover filters (almost as good as Gaussian in that regard) at ~400-500 Hz will reduce that crossover phase shift to a minimum.  But FIR filters will also handle these issues, too, if you've got them available.  What I'm looking at is the elimination of the additional D/A-->A/D from the output of the preamp to the input of the DSP crossover using the PC bus interfaces that Ellery found. 

 

It would be nice to be able to package all of that into an integrated package for those folks that might be a bit overwhelmed with the technology, but still want the superior sound that you can get out of them...;)

 

Chris

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ATI makes some 8 channel amps that use the hypex n-core modules: http://www.ati-amp.com/AT54XNC.php.  I have a feeling these would make great amps for tri-amping, and you could fit 16 channels in 8 rack units and have much lower noise floor than other consumer brands.  They are likely the best bang for your buck, and the only amps that measure better are the Benchmark amps, but they are very expensive even if you buy them in bulk like I did.

 

I would probably call ATI and see if they have some B-stock units.  They have gave me a 50% discount 8 years ago, but I'm not sure what they are doing now days.

 

As for ease of use here's a video of some of the controls and display in action: https://drive.google.com/open?id=19DguWj0G3R-7xSj7UBlGWrW507STXZSA

 

And here is some of the code I had to create to get everything working: http://cocoontech.com/forums/topic/30996-new-modules-matrix-orbital-vk-displays-vfd-rme-totalmix-osc-jriver-and-mce-controller/

 

You can get a PC to act like an appliance, but it does take a lot of setup.  Even when I use the keyboard volume control, RME TotalMix changes level (instead of the Windows volume mixer).  The JRiver apps make it very easy to play a movie or music though using an iPad or Android tablet too.

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