Tune the encoded format to the information the source actually contains
Practical LAME MP3 settings for spoken word, FM and AM radio, historical discs and other sources whose useful bandwidth differs from modern full-range audio.
Source-aware MP3 Encoding Guides
Encode for the source, not just the bitrate
Most restoration workflows concentrate on producing good PCM first. That remains the right starting point. These guides add a second question: once the useful information in the source is understood, should the MP3 encoder be asked to represent frequencies or channels that the source never meaningfully contained?
The aim is not to replace restoration. It is to avoid wasting lossy-encoding effort on out-of-band pilot tones, receiver noise, surface hiss, duplicated channels or other material that does not belong to the useful programme.
Three-stage workflow
- Replay and restore correctly. Set speed, replay equalisation, channel handling and any necessary restoration in PCM.
- Assess useful bandwidth. Use the known source format, spectrum and listening to decide what part of the signal contains programme information.
- Tune the encode. Choose VBR/ABR/CBR, mono/stereo and, where justified, a low-pass that matches the source rather than blindly preserving noise or signalling components.
Guides
Interviews, podcasts and storytelling
Bitrate, mono/stereo and bandwidth choices for voice-first material.
FM radio recordings
Work with the 15 kHz programme limit and residual 19 kHz stereo pilot.
AM, MW and radio bandwidth
Account for transmission standards and the often narrower bandwidth of real receivers.
Historical discs and 78 rpm transfers
Keep replay EQ separate from encoder bandwidth and use manufacturer/era data as context.
A note on high-pass filtering
Low-frequency rumble is a real issue in disc transfers, but LAME's built-in high-pass has an implementation limit of roughly 481 Hz at a 44.1 kHz sample rate. That is far above a normal vinyl-rumble filter. Rumble, mains hum and subsonic cleanup should therefore normally be handled in PCM before encoding; LAME's low-pass is the more useful source-tuning control for these guides.