Here are some key factors that can limit the number of exciters used in a DML speaker:
- Panel Size – There is only so much surface area to mount exciters. Packing too many exciters too densely risks coupling issues.
- Amplifier Power – Each exciter requires amplifier power. Too many exciters can overload an amp’s capacity.
- Impedance – Wiring multiple exciters lowers impedance seen by the amp. Too low can cause issues.
- Acoustic Coupling – Exciters spaced too closely can acoustically couple, causing phase issues, uneven response.
- Cost and Complexity – More exciters add expense and make crossover design and wiring more complex.
- Diminishing Returns – Beyond 4-6 exciters, further gains become smaller and incremental.
- Panel Distortion – Too many exciters can overdrive the panel material causing distortion at high output.
- Placement Optimization – It’s better to focus on ideal placement for a few exciters than just adding more randomly.
In summary, considerations like panel size, amplifier power, acoustic coupling, and optimal placement typically limit exciter quantity to 2-6 for most DIY DML speaker designs. The goal should be quality implementation of a few exciters rather than simply maximizing driver count.
Citations:
[1] https://www.diyaudio.com/community/threads/a-study-of-dmls-as-a-full-range-speaker.272576/page-254
[2] https://en.wikipedia.org/wiki/Distributed_mode_loudspeaker
[3] https://youtube.com/watch?v=MHCpcbOnZZw
[4] https://www.daytonaudio.com/topic/excitersbuyerguide
[5] https://www.instructables.com/Make-Your-Own-Transparent-DML-Speakers/
[6] https://projectgallery.parts-express.com/speaker-projects/dml-flat-pannel/