“My goal is to design a 3D printed standalone speaker based on transmission line theory
Hello to everyone! Today I am happy because I can finally introduce you to this project that I have been working on for many months now. These are 3D printable speakers connectable with a cable to a PC, or using the Bluetooth of your notebook or smartphone. They have a lot of acoustic power, pushing out without distortion 10 watts RMS (in general the computer speakers are 3 watts!), and thanks to the hi-quality full-range driver, they rock! They are also perfect to keep in the room to listen to music as you do with that little portable Bluetooth speaker, but I swear, these speakers sound much better.
“A transmission line loudspeaker is a loudspeaker enclosure design which uses the topology of an acoustic transmission line within the cabinet, compared to the simpler enclosures used by sealed (closed) or ported (bass reflex) designs. Instead of reverberating in a fairly simple damped enclosure, sound from the back of the bass speaker is directed into a long (generally folded) damped pathway within the speaker enclosure, which allows far greater control and use of speaker energy and the resulting sound.”
The cabinet simulation was obtained with HornResp by entering the T / S parameters found on the woofer manufacturer datasheet.
Once I got the transmission line, I modeled it using Grasshopper for Rhino.
Since my transmission line had to be 3D printed I could introduce some innovation and work with much more complex surfaces; so the algorithm takes the parameters from HornResp and makes rectangular cross-sections in golden ratio, with an always correct parabolic trend of the surfaces of the duct during the folding. The folded TL is then used in Fusion 360 for the design modeling.
Baffle step crossover (not added)
For the baffle step crossover design I used XSim, and I created FRD and ZMA files using FPGraphTracer. You can download them from the attached files list.
At the beginning I clap my hands to show the room acoustics, the sound level, and the background noise of the microphones. The recording is done with my smartphone, which has two microphones and records in stereo with a rather decent quality, but still nothing “ideal” for these things. Listen to it on headphones, but remember that what you hear is a sound captured by microphones and reproduced by the quality of your headphones, at best you can judge the richness of the sound.
The speakers were 90cm apart, and oriented towards the listening center at 160cm where the smartphone was positioned on a tripod.