small bass reflex desktop speaker (8cm driver) by jojolll

Last crawled date: 3 years, 4 months ago

Thingiverse broken, but it's a remix from https://www.thingiverse.com/thing:4668173
After testing the @Guppyk model, I found that it lacked low frequencies. This is certainly due to the architecture of the speaker, which doesn't have much "resonance" space behind the driver. Moreover, its model is complicated to assemble, you have to either glue or cut out the side parts in wood.
So I decided to design simple desktop speakers, trying to recover some low frequencies.
This one is "print it and use it". You just need 4 screws for the speaker, and 4 for the front panel (you could glue it).
I notice that the 4 screws on the front panel are slightly spaced in the height direction. I added 5cm of hot glue to ensure a good closure on each side.
For the design, I used the tools available at DIYAudio to deduce the best box architecture (https://www.diyaudioandvideo.com/Calculator/).
The conclusion of these tools: 2.09lts enclosure, ported box.
So I followed these advices for the modeling. The inside of my enclosure is 2.09lts, and the vent respects the tools calculations.
Having already printed Guppyk's enclosure (https://www.thingiverse.com/thing:4668173), I compared the two boxes and I am satisfied with my design, which has a better overall sound (to my ears and those of my girlfriend) and attenuates much less the low frequencies.
After several tests in stereo with a pair of my design, the results are really better than with the original design, but it doesn't replace a subwoofer.
With a bass EQ, I have good results, but I'm thinking about adding a subwoofer for very low frequencies.
[UPDATE (11/01/21) : I made two new tests, a closed box of 1.1 lts, and simply closed the vent on the box of 2.09 lts. None of these solutions is better than the ported box.
I noticed that the 1.1 lts box vibrates much much more, but does not have more bass, on the contrary. Also, I recovered a home theater subwoofer, and the sound rendering in 2.1 is very good, without EQ.]
Hardware part :
The stands are optional, you can use the original design ones, as for the speaker cover.
Driver : VISATRON FRS-8 M (8cm = 3.3 inch).Only 8cm, for another size or speaker you have to redo the calculations and redesign a box.
Screws needed : 8pcs M3x16 + 4 nuts (nylstop for me)
optionalnal for feets : 4pcs M3x8 (bottom not fully drilled intensionnally, you have to force when screwing)
Since these are 8 Ohm and 50 W peak speakers, I decided to use a TPA7498 module of 2x100W peak (@4 Ohm & 36V).
If this module is powered in 25V and with these speakers, it will be barely able to deliver up to 2x50W, which is exactly what I want (EDIT : 2*50W is huge. I've never gone above 10W (with the subwoofer !), so you can also plan a less powerful circuit).
If the amplifier is more powerful than the loudspeakers, it's absolutely not a big deal and it's even a good thing (refer to many topics on the internet).
I don't plan to integrate this module in a loudspeaker, so feel free to design a box dedicated to the amp.