Here are a few key points on how the thickness of a DML panel affects its sound quality:
- Thinner panels generally have better high frequency response and dispersion, but less low frequency output[1][2].
- Thicker panels exhibit better bass extension down to around 100-120Hz before needing a subwoofer. But highs may be more directional[1][3].
- Optimal thickness is typically around 10-20mm (0.4-0.8 inches). Thinner panels may flex or tear over time. Thicker ones get heavy and less efficient[2][4].
- With thicker panels, spacing between resonance modes increases, smoothing the frequency response. Thinner panels have more closely spaced modes[3].
- Efficiency and maximum output tends to be greater with thicker panels. Thinner panels require more amplifier power[2][5].
- Edge diffraction effects are reduced with thicker panels. Thinner panels are more prone to beaming at high frequencies[3].
- Thicker panels generally provide a fuller sound, while thinner panels image better. A balance needs to be struck based on goals[4][5].
In summary, moderate thickness around 0.5-0.8 inches provides a good compromise between bass extension, efficiency, frequency smoothness and wide dispersion for high quality DML speakers.
Citations:
[1] https://www.diyaudio.com/community/threads/a-study-of-dmls-as-a-full-range-speaker.272576/page-184
[2] https://www.reddit.com/r/diyaudio/comments/qq6rdw/dmls_50mm_thick_xps/
[3] https://dmlspeakers.com/articles/Does%20Size%20Really%20Matter
[4] https://techtalk.parts-express.com/forum/tech-talk-forum/64791-diy-flat-panel-speaker-love/page89
[5] https://projectgallery.parts-express.com/speaker-projects/fantastic-192-watt-diy-dml-panel-speaker-build-bertha/
[6] https://www.audiocircle.com/index.php?topic=70541.3080