Designer:

Bobby Kinstle

Project Category:

Bookshelf Speakers

Project Level:

Intermediate

Project Time:

8-20 Hours

Project Cost:

$100-$500

Project Description:

My dad asked for a speaker that could help him hear better for TV shows , movies, and music to mount on the wall on either side of his big flat panel TV.

Design Goals:

The speakers needed to have very clear voices and vocals so someone with hearing damage can still understand what’s being said on the TV. It has to be self powered and with SUPER SIMPLE operation, controlled entirely over HDMI from the TV remote.

Driver Selection:

I opted for the Tang Band W6-2144 driver because their bamboo paper cones always do great justice and emphasis on the human voice. Their vocal forward and warm nature are perfect for this application. While these full range drivers are extremely clear, everything sounds very flat to my dad so I added a Dayton Audio DC25T-8 tweeter to sharpen the detail edges.

Enclosure Design:

I used ⅝” MDF to keep the weight down with a solid teak panel front face. The shallow design helps it be flat on the walls but still have enough internal volume for a decent bass reflex design. Deep powerful bass isn’t needed in this application and I mounted the port downward facing so no objects can fall into them. The back has a french cleat to secure it to the wall. 17 Liter internal volume and a 1.5” by 4” long port gives an F3 of 61Hz.

The amplifier enclosure is made of Walnut with some CNC engraving on the top.

Crossover Design:

The crossover is a 2nd order Linkwitz Riley topology at 4300 Hz. This was a good point to match these two drivers with a very smooth and flat response. I wanted it high enough to let the TangBand handle the sounds that are often too harsh below 4K but low enough that rising impedance wouldn’t be a problem. 4300 Hz fit the bill very nice with a slight dip at 2800 Hz. I built on the handy Dayton 2 way 12dB crossover PCB. Minimum impedance 6.8 Ohms and the tweeter is reverse polarity.

Tips & Tricks:

Seal MDF with sanding sealer before applying any other finish.
Downloading ZMA and FRD files and trying to build a crossover before ordering parts really helps dial in the design and give you a good idea of what you’re going to get.
It’s good to re-run ZMA and FRD in the enclosure. ZMA is easy with a DATS but FRD is much harder without a proper acoustic recording space. Turning the volume up to 1 watt helps.
Tweak component values in crossover simulation using increments of values you can actually buy and see how it plays out on the simulation.
Some paint, like Rust Oleum Hammered finish, takes literally weeks to dry before you can set it on another surface. Sitting in direct sunlight for a day helps speed that up. Just be patient and don’t touch it no matter how much you want to mess with it and test it and listen to it. Sorry just gotta wait.
T nuts help get really tight fitting joints in soft materials like MDF with no worries about stripping it out.

Conclusion:

The speakers are warm and inviting. Vocal heavy music always puts the vocalist first and vocals are super clear and easy to understand. They do great with strings and horns or just sitting around watching the news on TV. There’s plenty of power for my dad to hear everything he needs. Vocals are bit forward but that was a goal in this project. My dad can control the volume with his TV remote. No need to mess with more than one remote, super simple just the way he likes it.

About the Designer:

I grew up in the Mojave Desert in a small community of scientists, craftsmen, and engineers. We were the kind of people who didn’t accept “it’s impossible” or “you can’t do that”. If I want something that doesn’t exist, I’ll just make one. Now I manage a team of engineers in the hyperscale server industry and I currently hold 17 patents worldwide.

Project Parts List: