Generally, I am investigating the limits/extent of what I can do with Linux/Alsa/DSP as an alternative to commercial equipment in these three areas:
1. the live concert scenario (we currently do everything analog now) -- as previously discussed.
2. home theater / hi-fi
3. something I haven't mentioned before: using WinAudioMLS and RME 9632 as a RTA (I know this will work) -- eg measurement/RTA for both home hi-fi and prosound / live concerts.
All of these to extend below 20Hz as far as I practically can.
Sergei, I will be digitizing my SACD audio output via a RME card etc as I think you must be right about interfacing a SACD to Linux directly/digitally... And I want an analog input/output capability if at all possible as after all the real world is analog!
For all scenarios I know I can go out and buy hardware to do this -- an exmple for #1 is the DBX DriveRack PA (about $500) including subsonic "synthesizer" and three-way x-over, parametric EQ's (post Xover) and 31 band GEQ, limiters, compressors. A pretty good brand, plug-in solution for small venus. About the same price as a good RME card.
For #2 I'm certain I can buy a variety of very expensive AV receivers to do what I want.
For #3, if all else fails, with a good RME card and Windows, I'll have a decent RTA.
You and Sergei both rightfully question my intentions here, as well as my quest for subsonic reproduction.. Although I realize frequencies below 20hz aren't technically audible, in my experience with audio, I have realized that the perceptual sensation to the body at subsonic frequencies (eg where the ears drop off and the body takes over) is an important part of the "total experience". In fact you may already know how popular subsonic bass reproduction is in the high end marketplace these days -- take for example vibrating furniture, A/V receivers that work to well below 20hz, SACD CD's some of which do indeed contain subsonic energy, and the list goes on and on. There must be something to all of this! I want to explore everything Linux can offer me in this exciting new area. I believe (but can't quote a specific source) that the brain synthesizes low frequencies not present in music. Indeed, I find when listening to a good recording -- if I have excellent LF response, I find I can turn down the midrange and treble as the LF seems to "satisfy" some audio craving I can't explain. Interestingly, from my perspective anyway, the most difficult thing to reproduce (cleanly and physically due to the large spaces required) is low frequencies but these challenging low frequencies tend to be the most "satisfying".
A good friend of mine is a rocket engineer. Since high school, he has been building liquid rocket engines, his first with 100# thrust, and in his recent years he has developed some very innovative exotic engines which he tests in Mojave CA and New Mexico facilities. I've had the opportunity to visit him and to experience these tests first hand on many occasions. If I could sum up in a sentence what I'd like others to experience: it would be to experience true infrasonic energy as in a live rocket test firing (the lack of the "real thing" enhanced by video of course). At some point I'll be attempting to digitize one or more of these firings to be used as a reference source in my experiments; however, for now I will be using a combination of live music, pipe organ music, synthesizers, electronic test equipment, SACD CD's (Telarc, Mobile fidelity sound lab) and other CD source widely known to contain energy between 5-20HZ. The information is there - I need to reproduce it and hopefully to manage this with Linux! Am I crazy? probably...
As I'm sure everyone here is aware, most music recordings (at least until recently) do not contain any signals except rumble and extraneous noise in the 5-15-Hz range. This is I think due to the fact that the recording equipment employed (microphones, tape recorders, etc.) was almost never designed to cover this infrasonic range; besides, and as comments in this and other news groups hints, few really care or know about recording or reproducing these low frequencies. So what's to hear if there is nothing to hear? I'd like to think if I had LF response down to 5Hz, besides the vibration through direct bone conduction, I might realize improved transient and phase response in the audible range, resulting from the extended LF response of my audio system. What do you think?
Having had experience in electronic (analog) design, I can say there is a practical limit to what you can do with analog / opamp filters/eq's in terms of low frequency loudspeaker/system management. My hope was to explore free or low-cost software/hardware combination using DSP/Linux; I realize however you can't get something for nothing. In any case this is probably more than you wanted to know.
Thank you
Ronan
On 2/1/07, Bill Unruh <unruh@xxxxxxxxxxxxxx> wrote:
On Thu, 1 Feb 2007, ronan mcallister wrote:
> Hello,
>
> I've recently discussed other topics (including RME) on this forum, related
> to prosound and DSP; here I want to focus a specific question I have about
> home hi-fi and theater.
HOME HI FI? I thought it was for large concert venues. In any home room,
the bass response craps out because of the size of the room. Ie, below
about 100 Hz the response is completely dominated by the room, and at 5Hz,
it is simply the pressure increase caused by the motion of the cone. ( and
how well air sealed the room is). Any kind of bass reflex, which is what
almost all bass speakers are has zero response at 5 Hz.
And a closed acoustic suspension is not much better.
>
> I'm using Suse 10.2 with RT kernel and I am considering the RME products
> (RME 9632 for instance).
>
> Regarding one Windows XP "legacy" app I have -- WinAudioMLS pro; I am
> leaning toward a RME if nothing else but for this card.
>
> Also, the RME has the subsonic capability (to 5Hz) which is what I need for
> both audio RTA and subsonic processing (if I can figure out what I need to
> do this).
I think maybe the key is why you want to do it.
>
> And RME seems to have quite a bit of Linux support.
>
> As well, the 9632 seems to have enough channels to do the job of surround
> sound 7.1.
>
> I'd love to hear from anyone who has implemented their 5.1 or 7.1 surround
> sound using a RME card! As well, I'd welcome any news from folks using the
> RME card in Linux for multichannel SACD playback.
>
> I guess I'd need the extra I/O card to actually give me the discrete
> channels I'd need.
>
> Am I trying to do too much with Linux?
>
> thank you
> Ronan
>
>
--
William G. Unruh | Canadian Institute for| Tel: +1(604)822-3273
Physics&Astronomy | Advanced Research | Fax: +1(604)822-5324
UBC, Vancouver,BC | Program in Cosmology | unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1 | and Gravity | www.theory.physics.ubc.ca/
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