Waveguided HiFi Speakers

These speakers are designed using the poly SB Acoustics SB15 and alum SB26 drivers, with integrated augerpro waveguide
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updated June 22, 2024

Description

Introducing the best (in my biased opinion) 3D printable speakers on the web! 

These MTM simi-bookshelf speakers borrow from the D'Appolito design principles, and create an excellent sense of space and dynamics. 

The magic in this speaker centers around using the SB Acoustics SB15NRX-8 woofer and wave-guided SB26ADC tweeter in a mid-tweet-mid configuration, crossed at about 1700hz. By waveguiding, the air mass in front of the tweeter is increased, which allows for it to be crossed so low. The crossover point needs to be this low, since having two mid drivers playing the same waveforms next to each other can cause directivity issues and interference at higher crossover frequencies. 

When properly executed, the resulting speaker design can create an excellent on and off axis horizontal, as well as vertical, frequency response. 

Here is a summery of the crossover I designed, but feel free to try your hand at improving it or using an active crossover. I personally found this design to be the best compromise between neutrality and efficiency:

 

Crossover Design:

The 2.2uf, 100uh, and 10r notch filter is optional.

The 5.1 and 150uh filter, which is used to suppress woofer breakup, is optional as well.

Simulated impedance:

 

Ground plane measurement gated at 10ms:

I found the 3.5khz resonance to be equally distributed throughout the horizontal and vertical dispersion, and can therefor be equalized using these filters:

I switched back and forth between the filter being on and off, and in my room, I could not hear a difference. If you have a heavily dampened studio, this EQ filter may be preferred. From my in room measurements, the treble boost was unnecessary. By snipping off the phase shield from the tweeter front plate and adhering it to the waveguide, a more even and elevated treble response can be achieved.

Feel free to tune the crossover for your own desired voicing, I would love to see what the community comes up with!

Here are the full measurements with the filter and FIR crossover phase linearization (LR 24db @ 1600hz):

10ms gated:

100ms gated:

 

Just like my other bookshelf speaker design, this speaker bass port is internally vented. These port vents allow for higher frequency port resonances to be bled off, resulting in a port which has almost no resonance byproducts!

 

Distortion:

 

I recommend two brass heat-set nuts be installed in the tweeter mount holes once printed, and before the three main body parts can be JB welded together. 

Once the JB Weld / adhesive  is cured, the tweeter can be installed using the tweeter bracket, with a bit of foam / paper towel / cloth sandwiched between the tweeter and the bracket. I would suggest using bluetac (or similar) putty between the waveguide mouth and the tweeter, to ensure a proper seal.

Here is my suggested layout for the crossover, and where to install it in the speaker:

 

 

Once the tweeter and crossover are installed, the two cabinet braces can be installed with JB weld. Installing all the components in this sequence should result in a painless and simple speaker build!

I suggest lightly packing the woofer section with polyfill, and heavily stuffing the tweeter section with polyfill.

I used Dayton Audio speaker taps:

https://www.parts-express.com/Dayton-Audio-BPA-38G-HD-Binding-Post-Pair-Gold-091-1245?quantity=1

Your feet of choice can be used, there are many options to chose from out there that will work!

I printed my speakers with Bambu labs black PLA, because it gives a great finish and is easy to print with. I used a 57f heat bed, and printed at 30% cubic infill. Supports are optional, but I did use them for the top of the woofer opening. 

As an added bonus, I have included the files to a normal MT bookshelf, using the 4 ohm SB15 woofer. The same crossover used in my other design can also work here as well:

https://www.printables.com/model/661737-waveguided-bookshelf-speakers-using-sb15-woofer-an

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