PC Crossover Software

[jman11964]

Originally Posted by boris81

44.1 -> 96 -> analog -> 96 -> processing -> analog.

I think with miniDSP you go:

44.1->DAC->ADC->SRC(48)->processing->DAC

Or you can send it the SPDIF (if you have a miniDIGI) and cut out the first DAC->ADC pair, and it still does SRC. I don't klnow if the onboard SRC will be better or worse than a software sRC at source.

The GroundSound units will process at 96kHz, but I don't think they have an SPDIF feed option.

[tritosine]

Lynx can be slaved to the DA converter that's a nice way of doiing things.

[Pano]

Both miniDSP and the DCX2496 can be used with digital inputs. No need for the A/D conversion. miniDSP runs at 48Khz and the DCX at 96Khz, AFAIK.

[planet10]

Originally Posted by jman11964

I guess his jobs-ness doesn't see fit to allow a PCIe on an iMac so its not very practical, which is a shame since the small iMac might be fine otherwise.

Expect the next rev of the iMacs to have Light Peak/Thunderbolt (like the new MacBook Pros), which does support PCIe,

http://www.diyaudio.com/forums/digit...-new-post.html

dave

[boris81]

Originally Posted by Pano

Both miniDSP and the DCX2496 can be used with digital inputs. No need for the A/D conversion. miniDSP runs at 48Khz and the DCX at 96Khz, AFAIK.

Thanks for clearing that up, I wasn't sure about the digital input.

OK so miniDSP offers a better precision than kx-project because it processes in 24bits but they both run at 48kHz. Does miniDSP upsample the signal on the output?

[jman11964]

Originally Posted by boris81

Thanks for clearing that up, I wasn't sure about the digital input.

OK so miniDSP offers a better precision than kx-project because it processes in 24bits but they both run at 48kHz. Does miniDSP upsample the signal on the output?

Increasing 16 to 24 bits isn't an upsampling operation. SPDIF data streams have 24 bits of precision, but consumer devices only fill in the least significant 16 bits. So its just a multiplication opportunity in the crossover, AFAIK anyway.

Note that you need a miniDIGI to get SPDIF input to a miniDSP, and that means you can't use the handy off-the-shelf enclosure. The miniDSP/miniDIGI combo is $160. I'm wondering if its worth the hassle of building a custom enclosure and power supply and using these, or whether it makes more sense to just put a fanless Atom PC behind each speaker and use my choice of PC sound card.

Seemed like overkill when it first popped into mind, but once you factor in pain of building enclosures etc its tempting to consider GroundSound, and then its tempting to consider that you can pretty much build a PC and MAudio solution for the same money, give or take. Madness!

[Tenson]

What do you guys think is the best (most powerful yet still cool) CPU for a mini-ITX system to do crossover duties? You have a few options like a dual core Atom, some of the lower power i5 chips or Phenom x4, Athlon II chips from AMD. A powerful 'mobile' processor seems like it would be good but I don't see they are easy to get hold of and don't fit most ITX motherboards.

Low power chips obviously mean the PSU would do less work and is easier to cool without a fan.

[BobEllis]

It depends on your chosen software's requirements.

I have Frequency Allocator running on an old 3GHz Pentium D with 1 GB of ram (three way XO, although I don't think it affects CPU usage much). Even when running multiple other applications simultaneously, I haven't had a playback glitch. Building a mini-ITX box for Frequency Allocator, I'd go with the lowest powered processor I could find.

If you want to use another program, take a look at the user support forum. There are likely to be a number of "how much CPU power do I need for a standalone" threads.

[jman11964]

Originally Posted by Tenson

What do you guys think is the best (most powerful yet still cool) CPU for a mini-ITX system to do crossover duties?

No idea - I'm fairly confident in what I need, because I'm planning to use IIR and not try to push the envelope with a lot of FFT code.

Seems you can get fanless dual core Pine Trail at 1.8GHz for 60 quid here: mini-itx.com - store - Intel Atom Mini-ITX boards but you'll need choose a case and PSU solution carefully to run a PCI card - the boards with integrated power probably code out cheaper (eg with a M300, albeit useless CF - expect to boot off a USB key). Absolutely no idea how well BruteFIR would run on that, although we've had 10 years of CPU evolution since Torsten started on this - and gcc got a good deal better at optimising too.

But don't listen to me - my current ITX is a server and definitely not silent! I'm attracted to the M350 case for convection cooling but it does imply a USB or firewire sound card. If you want silent/passive cooling, you might want to consider a PSU-less microtower case so there is air over the motherboard rather than something small with a PCI card laying right over the CPU heatsink.

You haven't said how much software you aim to do - sure the path of least resistence isn't to keep that LynxAES and just run Windows off an SSD with Frequency Allocator Light? Won't do all the magic phase stuff, but Thuneau can probably advise what sort of CPU you'd need for teh full-fat version.

[Tenson]

I plan to have 8 channels, each using FIR phase linear crossovers and inversion IIR EQ to smooth the response of the drivers. I also want delay to be as low pas possible. Quite a heavy load I suppose.