Week of 17 January 2005

One of Barbara's belated Saturnalia gifts finally arrived, a Creative Labs MuVo Micro N200 flash-based MP3 player. Like one of our Border Collies who once caught a UPS truck by the front tire, the question becomes, "Now that I have it, what do I do with it?"

Barbara wanted a tiny, sub-$100 MP3 player that she could take to the gym. I looked for a unit that supported OGG Vorbis format, but the only ones I could find that did that were way out of our price range. So I settled for the MuVo, which like most units supports MP3 and WMA. The first question is, which format should I encode Barbara's CDs to?

I have no idea whether the MuVo supports variable bitrate MP3s, so if I settle on MP3 format I'd do some test files at different data rates using constant bitrate and variable bitrate encoding to determine which formats the MuVo supports. Obviously, after I rip all her CDs I'll have to encode them, and I'd prefer to encode them only once. I'm not concerned about minimizing file sizes for the MuVo; I want quality good enough to use for home audio as well. With constant bit-rate MP3, that probably means encoding at 320 kb/s.

I installed grip this weekend and ripped and encoded a dozen or so of Barbara's CDs to 320 kb/s MP3s, just to have something to play with. At 320 kb/s, a full CD generally occupies from 75 MB to 175 MB, which isn't unreasonable. The good news is that when I connect a USB cable to Barbara's MuVo it appears as a USB mass storage device. I can simply copy MP3 files to it as I could to any other drive, and delete them when she wants to substitute other files. The MuVo has a USB 2.0 interface, which is a blessing. I'd hate to fill it with USB 1.1. It'd take quite a while.

But before I rip and encode hundreds of CDs, I want to make sure I've made the right choice for encoding. I think I understand that WMA has better audio quality than MP3 across the board. WMA even supports lossless compression, which would be ideal. I'm not concerned about the proprietary WMA format, because these files will be only rips of the original CDs, which will remain available. I am concerned with playback, because of course we're standardized on Xandros Linux around here. If I'm going to encode to WMA, I want to make sure that there's a full-function player for Linux that supports WMA format(s). Ideally, I'd like to do the encoding on a Linux box, but if there's no WMA encoder available for Linux (or if the Windows-based WMA encoders are superior in features or audio quality), I'd be willing to do the encoding on a Windows box.

Which brings up the question of how to organize all these audio files. Barbara has hundreds of audio CDs. Ideally, what I'd like is a Linux application that would allow me just to feed in a stack of audio CDs. It would rip each CD, get the metadata from CDDB, encode each track to MP3 or WMA using whatever parameters I specified, and add each CD and track to a database. When Barbara wanted to reload her MuVo, she could simply fire up the database application and sort by CD title, track name, artist, genre, or whatever to build a custom playlist. She could then mark checkboxes for those tracks she wanted to copy to the MuVo, connect the MuVo's USB 2.0 cable, and copy away.

-------- Original Message --------
Subject: Boomy speakers
Date: Mon, 17 Jan 2005 18:06:18 -0600
From: Edgerton, Paul A
To: Robert Bruce Thompson

In a prior life I was a recording engineer. I think I can explain why your Logitech speakers seem boomy while the M Audio speakers in the other room do not. The short answer is that bass frequencies have very long wavelengths. They are much more affected by the physical dimensions of the room and coupling between the speaker and nearby surfaces. Those factors have much less effect on higher frequencies.

You mentioned that your Logitech speakers are a 2.1 system. I'm guessing that you have the subwoofer near a wall, on the floor or both. Many speakers are designed to radiate into a spherical space, but most subwoofers were intended to rest on the floor, radiating into a hemispherical space. If you put them too close to a wall, this looks like a quarter-sphere at bass frequencies, so the bass would seem louder. If you stuck the subwoofer in a corner, you are radiating into only 1/8 of sphere. The walls of the room act as a kind of a horn. (Remember Klipschorns?)

The implication of this is that you can fine-tune the amount of bass by moving the subwoofer closer to the walls or further out into the room. There are a couple of gotchas, though. First, your little subwoofer probably isn't putting out much real bass; I would guess most of it's output is around 100 Hz. This is near the top of the range of "real bass," and if you put the subwoofer too far away from the satellite speakers, the sound image sort of becomes "unglued" in the sense that the subwoofer appears to be a distinct sound source rather than a reinforcement of the satellite speakers.

Another problem occurs when you have a small room with parallel walls and not much low-frequency absorption. All rooms have pronounced resonances (or eigentones) that reinforce some parts of the frequency range but not others. The smaller the room, the fewer and further apart these resonances are. Unless the dimensions of the room are selected to avoid this problem, several different parts of the room may resonate at the same frequencies, especially in rooms whose dimensions are integral multiples. This buildup of resonances can be exacerbated by putting the subwoofer under your desk.

Barbara's speakers are better to begin with, and I suspect that they are in a more favorable acoustical environment. But as I suggested before, you can experiment with subwoofer placement to make some improvement in your other set up. Don't expect too much, though. Those little subwoofers make up for their lack of real, chest-pounding bass by putting out more sound in the boomy range from 100 - 200 Hz. If you tame the boominess, you may kill what little bass they produce. As in everything, TANSTAAFL.

I see that I 'm seriously past due on my membership renewal, which I'll take care of right away. Thanks for all you do.

-- Paul Edgerton