Wednesday, October 19, 2005

Recording Audio from Sermons and Classes

This post gives an overview of how I record audio files from my classes and sermons at church. I'm a tightwad, always looking for the cheap instead of the expensive, the free instead of the cheap. Being a techie at heart, I also look for better, cheaper ways to do things. Efficiency with efficacy is the key.

I have to take many classes in the course of preparing for ministry. I wanted to record the class audio, but tapes just don't work for me. I wanted a digital recorder, ideally one that records in MP3. I also needed to record sermons at church, so I began to look for a devices that would be able to do both.

I found one device that would do it all. Frankly, there are three or foud on the market now that do what I require, but I believe the products from iRiver continue to be the most reasonable and the most faithful recordings.

MP3 Recording Hardware

For church, I purchased an iRiver iFP-390T (256mb). For my own use, Cathy bought me an iFP-380T (128mb). There are much larger capcities available now. I selected the 3xx series because they include a line-in jack as well as an omnidirectional microphone.

Software (PC)

CDex Version 1.51 (
MP3Gain v1.2.2 (
Mp3 Tag Tools v 1.2 Build 008 (
mp3DirectCut (
dBpowerAMP Music Converter (

Acquiring the source audio

The iRiver iFP-380T/390T is a flash ram MP3 player and voice recorder. It has a stereo line-in jack which can be used to record MP3 audio (requires a powered signal). For sermons, I record the audio on the line-in jack at 64kbps at mono. I can record about 7:45 of audio on the 390T )256mb, which allows up to four recordings.

For my classes, the 380T gives me 7:45 of voice recording at 32kbps, which should be sufficient if you are diligent in archiving your audio files weekly. A single battery will usually record about 16 hours worth. The trick is to place the device at least three feet from the speaker but with no osbstruction between the device and the speaker.

For both devices, I use the iRiver's UMS (USB Mass Storage) firmware version 111. This causes the device to show up as a USB drive (like an USB keychain).

Why record in mono instead of stereo? The final output file I desire is mono, so recording in stereo is a waste bandwidth. Also, note that a mono 64k MP3 has the same quality as a 128k joint stereo stream recoded to mono. I get a better quality source file by encoding in mono.

Since I am recording sermons from a live church service, I am plugging directly into the sound board. I am using the Studio Out, which is pre-fader, in order to avoid someone turning down the pastor's mic for the house and killing my recording level. I record the audio file with the dial at unity (0 gain). Ideally, I would use a pre-fader mono aux send, but my setup at church limits me. Also, I find that disabling all effects, such as reverb, is best for the speech portions of the recording.

Splitting and compressing the audio

I am using Windows XP, although most of this software if available for free on Linux as well. Non-Windows users can substitute Audacity for an audio splitter.

I use MP3DirectCut to split the source MP3 into smaller chunks and to eliminate silence or audio junk. Then I use MP3gain and adjust the audio to normalize at 89 db. The human ear cannot detect changes smaller than 1.5 db, so changes in increments of 3 db is suggested... some people suggest 92 db as a better baseline, I wouldn't really know.

Using "Mp3 Tag Tools" I label the tracks with the speaker or preach, when and where, the title and so on. Tagging the split up files allows all transcoded files to also have the same tags, thus saving you work later.

For uploading to the Internet, I use CDex, with Encoding Option set to "Windows MP3 Encoder" with a Codec Bitrate Selection of "24kBit/s, 11k Mono" and "High Quality" checked. This results in a FastEnc (FhG) encoded MP3 file, which sounds better for low bit rates than LAME encoding does. The file is about 21% the size of the original. I also take the tagged, uncompressed MP3 and use dbPowerAmp to creat "Windows Media Audio 9 Voice" files at 16k. The resultant file is smaller than the compressed MP3 about 14% the size of the original.

Why MP3 instead of XYZ

Why MP3? Why not Real Audio, or Vorbis? I selected MP3, not for its quality or size, but for the ubiquity of the format. Everybody has a MP3 player/decoder on their computer, and it will "just work." Although I am using FastEnc, I am not be required to pay royalties, from what I understand according to the licensing.

Why WMA? Windows Media Encoder (WMA) encodes voice at passable quality as low at 8kbps, and 16kbps is amazingly good. WMA has size as an advantage, the encoder is free, and there are no licensing fees for redistribution.

Why not OGG? I considered Oggs Vorbis, but while a quality of -1 does save 30% in size (a 6mb MP3 becomes a 4.2mb OGG), the Vorbis codec is simply not intended for voice, and does not sound as well. Without a size advantage, it doesn't make sense to transcode to Vorbis. Royalties are also not an issue here, but there is no compelling reasons to use OGG.

Finally, many folks, just as myself, have portable MP3/WMA players. Vorbis and other formats I have considered are usually not supported, or not supported at low enough bit rates for me to worry about them.

I initially used LAME to produce the smaller, lower-quality MP3 files to save space. I use all2lame (although any LAME front-end will do) and us the following encoding parameters:
--short --athtype 3 --lowpass 9.1 --cwlimit 7.2 --substep 0 --ns-bass 6 --ns-alto 13 --ns-treble 21 --ns-sfb21 6 --strictly-enforce-ISO --vbr-new --abr 24 --verbose -q0 -b 8 -B 40 -mm
For notes on which version of LAME to use see this forum link at HydrogenAudio. I started out using LAME version 3.93 because 3.90.3 did not work with All2LAME & tag.exe. The file is about 20% the size of the original.

I'm not an audio engineer or anything like that. I've done my homework and a lot of reading, but I'm just a computer geek that loves Jesus and wants to further His kingdom. I'll try to help you if you are trying to setup digital recording at your ministry, just don't expect a pro. You can contact me via email by looking in the footer on the main blog page.

Software to consider (also free)

LAME version 3.93 MMX (, see also
all2lame v1.9.1 (
RazorLAME (
Audacity (
DeepBurner (
CDBurnXP (

1 comment:

  1. I've been asked about digital recording before by fellow students or people who visit our church. This provides an place to point them to... :-)