Bill, Sergei,
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 <[EMAIL PROTECTED]> 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 7.1surround
> 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 | [EMAIL PROTECTED]
Canada V6T 1Z1 | and Gravity | www.theory.physics.ubc.ca/
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