Author Topic: A new computer in my music room.  (Read 3268 times)

Offline ToddC

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A new computer in my music room.
« on: January 29, 2009, 09:13:54 PM »
Hi Everyone. I'm a  newcomer here at AudioNervosa, but have been lurking for a while.  I'm a computer programmer by trade, was an electronics technician years ago and have always been an avid music lover.  I recently took the plunge into computer audio in a big way and I thought you might find my recent experiences interesting.

My system's analog side consists of a Ayre AX-7e integrated Amp and B&W 703 speakers.  My digital equipment consists of an older benchmark DAC1, a Rega Apollo CD player and  a dedicated Unbuntu server streaming 500GB of FLAC, WAV and MP3 files to a Slim Devices Squeezebox.

My listening room is a 12x16 room with a 15ft cathedral ceiling, with serious reflection problems that made listening in this room almost unbearable.  Unfortunately, it was either this room as a dedicated listening room or nothing, so I made the best of it.  While my wife was away on a business trip about a year ago I bought 9 acoustic panels and hung them around my room. The "ask for forgiveness" strategy worked in this situation :) The panels made a gigantic improvement and eliminated about 75% of the room's acoustic problems.

I really love my system, but there were still a few nits that I've been living with and wanted to fix.  A JPS labs digital AC power cord for the Benchmark DAC1 helped clean up grain I was hearing on vocals, but it seemed that a bit was still coming through.  The other problem was a resonant frequency that was really really annoying when playing music with deep bass. At moderate levels the whole room would just shake with a bloated 80Hz resonance.  On the plus side, imaging, resolution and dynamics were fantastic and I really didn't want to impact those.

Up until late last year, I had resisted any sort of computer integration with the stereo, as I felt that the combo of the Squeezebox and the Benchmark gave about as good of a digital sound as I was going to get.  Truthfully, I never noticed any significant differences between FLAC files through the Squeezebox and the CD that they were ripped from on the Rega. The ease of use of the squeezebox made it a much more user friendly solution, so thats how I listened to most of my music. 

So midlife crisis or something, I started asking myself, "is that all there is?" I started thinking about a high end turntable, but just couldn't bring myself to spend $7000 to make my pops and clicks sound more velvety...  The obvious answer was to start looking a better digital solution.  After months of web surfing, I decided that I needed two things to make me really happy (or so my I thought) - higher rez digital files and digital room correction to fix the remaining room harmonic problems. 

So I started down the road to installing a computer in my music room.  I felt that one of the main roadblocks to putting a computer into my room was fan noise that all computers have.  I bought a refurb HP computer and retrofitted it with a fanless power supply, a huge CPU heatsink and a lowspeed, noiseless case fan.  Once it was all together, I couldn't hear any noise from the computer if I was more than a foot away.  I found this quite acceptable. For the audio Card, I selected an m-audio 1212M as it had had both digital s/pdif and balanced analog connectors without an outboard. I setup a VNC server on the computer so I could control it from my laptop.   


I spent a few days learning the ins and outs of the m-audio patch mix application that is required to interface your music player with the sound card. Once I understood it, I felt I was ready to start experiencing hi rez audio.  I setup foobar 2000 to read from a file share on my music server and I sent the music to the sound card using ASIO.  I had several ripped DVD-a albums and I downloaded some 192Khz files from Lynn records.  The overall effect of the 192Khz 24 bit files was nice.  The improvement was much more subtle that I thought it would be, the major difference being a definite increase in airyness around the instruments. While this was nice, there's still not a lot of music to be found that's been recorded at this high a resolution, and what you can download is rather expensive.  Happy, but not fully satisfied yet....

The next trick was to start experimenting with room correction.  Flush with cash from a recent fantasy football championship (yea Nutsackers!!!), I splurged on not one, but two different room correction solutions.  The first solution was the Audiolense room correction software and the second was IK Multimedia ARC package.   

The basic process with both of the solutions is that you first need to perform frequency and impulse measurements.  Thes measurements are then analyzed and correction FIR (Finite impulse response) filters are created.  You apply the FIR filters through a "convolver" which is inserted somewhere in your computer sound chain.  Very simply, the convolver filter applies the opposite affect that your room is imparting to your sound, supposedly leaving you with a totally flat frequency response. 

To get started with Audiolense and measure my room frequency and impulse responses, I had to purchase a calibrated measurement microphone and a mixer to power the mike, a mike stand and some cables to hook it all up.  The application is sparsely documented. While a online forum exists, it doesn't have too much information on it.  Fortunately it was simple enough to use.  I ran through a few frequency sweeps and generated some correction filters at 44.1kHz, 88kHz, 96kHz and 192kHz. Audiolense does not come with a way to play the FIR filters that it generates, so I had to scrounge around on the internet to find a way to implement them.  The best solution that I came up with was to use a convolver plugin for foobar. 

Once I had all the pieces together, I was quite exicited to give it a listen.  To say I was suprised by the results is an understatement.  The sound was compressed, dead and lifeless. It was like I had replaced my Ayre receiver with a Yamaha.  I spent many hours tweaking and trying different correction curves, different convolver hosts, etc...  Everything I tried seemed to be a tradeoff of one sort or another.  One very interesting side effect during this tweaking phase was the experimentation with the undocumented menu selection "automatic polarity correction" It appeared to do exactly the opposite, reversing the phase of one of the speakers.  Ended up giving me a very 3d holographic sound and canceling out all of the bass. Very wacky.  Anyway, I'm sure that if I spent more time and engaged in conversations with the software developer I could have gotten better sound out of it.

After about 2 weeks of working with the Audiolense system, I decided to try the IK Multimedia ARC room correction system.  This is an all in one system that comes with it own  calibrated microphone.  The ARC's room correction algorithms are licensed from Audyssey, which is the same solution integrated into a lot of home theater receivers.  It requires DAW (digital audio workstation) software to use the resulting filters that it generates.  Since I tinker a bit with my own digital music, I already had Ableton Live to host this solution.

The measurement process was very user friendly, and quite different from the audiolense process.  The audiolense generated 2 long frequency squeeps one for the left and one for the right speakers, while the ARC system generated 12 sets of 10 short pulses from the left then the right speaker. Each set of measurements was taken from a different listening position centralized around the primary listening area.  This is supposed to help widen the effective listening area. 

It took about 10 minutes to take the measurements and a couple more to get the filter setup in my daw with the ARC VST plug-in. The whole process was very simple and the software was very professional in appearance and operation.  Once again I was very anxious to hear what difference this solution would make, and again I was very suprised.  The sound was diffent, but not near as disappointing as my earlier efforts were.  It was restrained, but it certainly wasn't lifeless.  It was very obvious that it had removed the echo that my cathedral ceiling was imparting to the room.  The 80hz hump? Totally gone.  Micro details in the music were much more audible.  The grain on vocals was gone.  I'm not entirely sure why, but I'm guessing what I was hearing and calling grain was an artifact of the room reflections.   The new sound allowed me to listen much longer without the typical listening fatigue I used to get after about an hour. Happily, I didn't notice any difference in sound staging or dynamics which were good to begin with. 

It's not all rosy though.  While the ARC software is easy to use, the integration of all of the pieces: Foobar, the DAW, asio routing, m-audio patch mix software is fiendishly complex.  It takes a while to figure out how to make it all work togther well and there are times when it just all has to be rebooted to make it work.  The room added character to acoustic material, when I a/b compare with the room correction on and off, it seems a bit more sterile with it on. 

I've just started playing around with the DAW's 8 band parametric equalizer to tweak the sound to fit it closer to my liking.  When I get nostalgic for the uncorrected room, It's all very easy to bypass.

It was a lot of effort to finally get to this point, but I feel that I've made a really big improvement to my system while keeping it relatively low cost.  Mid life crisis averted!