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HTPC Audio w/ Minimal Brain Damage

588 Views 7 Replies 4 Participants Last post by RayL Jr., Sep 10, 2003

ccd

Discussion Starter · Sep 9, 2003

Taking up the DRC thread with a different twist, there appear to be a couple of easy approaches to Audio HTPC, ie, 5.1 with crossovers and EQ.

All approaches would seem to rely on an audio card for processing (5.1 or 7.1). The cards of choice seem to be the M-Audio 410 or Revolution. For the high end the delta 1010 seems to be the choice.

1) Use a couple of Behringer DCXs which can be configured for 5.1. This is pretty simple and relatively cost effective. The Behringer can provide crossover and EQ for 5.1.

2) Use DRC and then use a crossover like the Behringer or Driverack 260 without using on board EQ. This would probably provide more sophisticated EQ. This approach assumes that DRC can be used for 2 pairs of speaker and one mono channel for the sub at the same time for 5.1.

I'm not trying to do anything sexy here, just something that isn't terribly expensive and easy to implement.

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RayL Jr.

· #2 · Sep 9, 2003

I'm thinking the same thing! I was also wondering about phase control in addition to crossovers (eg for a sub in the corner).

I also found these links: http://www.directproaudio.com/shop/s...m?section=1433

Alto X23 2-Way Stereo / 3 Way Mono Crossover

>115dB dynamic range for transparent sound

Phase inversion switches

Balanced XLR and 1/4" jack input and output connectors

Peak LED indicators

Linkwitz / Riley 24dB/Octave filters

Mute switches

Digital Crossover 2-way stereo,3/4-way mono

2/3 way stereo crossover, or 3/4 way mono crossover or distribution mixer. Delay lines up to 600ms for each input and up to 200ms for each output. Polarity reverse and phase adjustment on each output for a total of 360 degree operating range. Bessel, Butterworth, Linkwitz/Riley Crossover filters up to 48dB per octave.Each input and output features digital limiting and five parametric EQ's. 32 User presets.

This one can also use a Windows interface! "Several of our digital processors can have their parameters set via PC". Prices are not too bad either.

Alto crossovers - http://www.altoproaudio.com/default.asp?p_id=4

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RayL Jr.

· #3 · Sep 9, 2003

I found this link on the Behringer DCX-2496 ULTRA-DRIVE PRO review - http://www.audioasylum.com/scripts/t.pl?f=hug&m=52808

It sounds like an excellent piece of audio gear. Someone there on that thread also recommends the BSS FDS-336 - able to drive a stereo 3-way system but it's a lot more money.

The right digital attenuation in the sound card still could replace a hi-end preamp. The DRC thread mentions FIR filters (for digital room correction). I think they can do crossovers (w/filters) and phase control with software - only I'm not sure if the sound would be as "pure" as this solution. If it can be done in 24-bit like the digital attenuation I wonder...

An HTPC solution would be nice â€“ with the right software and possibly "hardware" to do it right.

That reviewer at AA above also rates it as excellent, one of the best changes he made to his hi-end "high efficiency speakerâ€ system. I'm comparing the Behringer with the Alto's digital crossover tech specs. Reading up on Alto - it also looks like they make excellent crossovers and digital amplifiers as well! I'll also look @ Marchand crossover specs.

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K-Wood

· #4 · Sep 9, 2003

I not sure exactly what you guys are talking about, but after wading through the digital room correction thread, it seems to me that we could get the biggest bang for the buck by implementing DRC on only the sub channel after the crossover, rather than trying to implement DRC on the full range of all five channels.

M-Audio's drivers for the 410 and Revo implement a variable sub crossover for all five channels. I could imagine a software solution that could "stack" a DRC convolver filter on the sub channel after the sub crossover, thereby applying DRC to only the sub channel. I'm not a software designer, so I have no idea how this would be implemented, but it does seem to me that the bass information is where the worst of the room nodes will be.

Forgive me for possible diverting your thread . . .

- Ken

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RayL Jr.

· #5 · Sep 10, 2003

Well, I see your point Ken, your thread was not OT. Eg, for a 2.1 system, have the mains run full range and then have a 2nd channel pair with the crossovers and phase to the sub (where DRC is implemented).

In a 2-way crossover design (digital or analog), the preamp or sound card outputs from just a 2 channel pair go to the crossover inputs. Then the crossover outputs have 1 pair to the mains and the 2nd pair (summed) to the subwoofer.

The method you mentioned would have the mains run full range, but would not blend or "disappear" with the sub nearly as well...

To see a simple diagram see Figure 3 - http://www.marchandelec.com/ftp/ug.pdf

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jimwhite

· #6 · Sep 10, 2003

This "could" turn into an interesting thread, but damn..... what a dumb name!!!

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RayL Jr.

· #7 · Sep 10, 2003

I thought the thread name "logical" - if he's comparing using a HTPC DSP solution and literally writing or finding your own code.

I'm working on a similar thread - Digital crossovers, phase and volume/attenuationâ€¦ Whether they are in the HTPC or soundcard or if they are in one of these "outboard" units.

Funny, the poor folks at AA are stuck on getting the digital volume control part (which we can already have in our HTPC). Resorting to EXPENSIVE Meridian, Wadia or Cary CD players. I did a search on "digital crossovers" there, seems a lot of these units need a preamp for proper volume control.

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RayL Jr.

· #8 · Sep 10, 2003

I have to note that for the Behringer DCX2496, Alto Maxidrive 2.3 and much â€œpro-audioâ€ type gear have XLR balanced connectors. Some do have balanced and/or unbalanced connection options like the DBX 223 and 234 crossovers, also the Alto X23 "Any combination of balanced and unbalanced operation is permitted".

"3. How do I connect balanced and unbalanced equipment? [Paraphrased from the excellent rec.audio.pro FAQ at
http://www.cis.ohio-state.edu/hypert...o-faq/faq.html amongst other places]

The correct way to connect balanced and unbalanced equipment is an audio balance transformer

To connect an unbalanced output (typically on a phono connector from some home audio equipment, eg a CD player) to a balanced input (almost always an XLR connector). Connect the centre pin to pin 2 of the XLR connector, and the ground ring to pins 1 & 3

To connect a balanced output to an unbalanced input is trickier. If it's a floating (passive) balanced output you can connect pin 2 of the XLR to the phono pin and pin 3 to the ring. If it's an active balanced output then you may be able to XLR pin 2 to the phono pin and pin 1 to the phono ring, leaving pin 3 unconnected. If that fails try connecting XLR pin 3 to the phono pin, XLR pin 1 to the ring and leavin pin 2 unconnected. Both of these approaches may well cause distortion or more noise." - http://www.faqs.org/faqs/theatre/sta...ection-27.html

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