Plans to build a speaker!

I have started designing and building a speaker! My dissatisfaction with my past speakers motivated me to want to buy new ones, however after plenty of research I was convinced I could build a better speaker for way less than buying one. My previous speakers were the Edifier R1280DB, a pair of Bluetooth bookshelf speakers, with a Monoprice 8" 60-Watt powered subwoofer (both pictured bellow). The Edifiers were wired to the subwoofer to provide extra bass.

Even with adding the subwoofer I was unhappy with the bass output. It was loud enough for me but it didn't not play low notes at all. After some research I learned that the Monoprice subwoofer has a steep highpass filter around 50 or 60Hz and would refuse to play those low notes. While I was unhappy with the speakers, it is important to note for the price range, the Edifier speakers are probably some of the best you can get.

Choosing the drivers

To start the design process I made sure to lay out my requirements. I wanted a speaker which could play 20hz-20000hz flat within a few decibels. I also wanted it to be able to adjust the volume of the bass so I could play it loud if I wanted because I really enjoyed the feature of being able to adjust the bass loudness on my Edifier speakers. These requirements led me to design a speaker that would have a huge 12" subwoofer, so I could play the loud low bass, a 4" inch midrange drive (it claims to be 4" but truly is 3") and a 3/4" tweeter for the treble. I also went with high sensitivity drivers so they would get loud with very little power.

Speaker Driver	Model (all manufactured by Dayton Audio)	Intended Frequency range	Sensitivity on 1 Watt of power	Image
Subwoofer	DCS305-4 12" Classic Subwoofer 4 Ohm	0-200Hz	90.5dB
Midrange	RS100P-4 4" Reference Paper Woofer 4 Ohm	200-3000Hz	88.5dB
Tweeter	TD20F-4 3/4" Soft Dome Neodymium Tweeter 4 Ohm	3000-20,000Hz	90dB

Designing the enclosure

After I had chosen my drivers I started designing the enclosure. I used WinISD to figure out an adequate box size and port size for my subwoofer. I settled upon using a vented enclosure tuned to 24Hz. WinISD give me a box size of 3.418ft^3 and a port diameter of 3in and a port length of 7.42in.

After getting the volume of the box I did some math to figure out the dimensions of the speaker enclosure. Using 3/4" wood I landed on a box that was 15.5" by 23.5" by 22.25". Inside the box there would be a second enclosure for the mid range driver that needed to be 0.05ft^3.

Once I decided on all of the dimensions it was time to start modeling. Since I had used Fusion 360 once or twice before, I came up with a simple bookshelf speaker design before to practice using Fusion 350. The design is very similar in size to my Edifier speakers and is pictured bellow.

Next I designed the first version of my speakers. I decided to make them white with a wood grain on the sides. I also included a horn for the tweeter and a quickly designed port.

Here is the speaker next to my first bookshelf design for scale.

After the first iteration I decided I liked the design and wanted to refine it. This time I made sure to carefully design the speaker so all of the drivers would sit flush and the port would sit flush. I also redesigned the horn and port so they could be 3D printed. Finally I decided I wanted glossy paint instead of matte. The volume of the box was also slightly larger as I forgot to account for some variables.

I will continue with the discussion of the design of the cross over in the next post!