A cleverly designed series of blue-tooth enabled desktop speakers inspired by producers' efforts to create the illusion of depth in audio mixes.
Producers and audio engineers alike strive rigorously to create “depth” in an audio mix - a sense of “front to back-ness” that the user perceives from two side by side speakers. In response to this industry standard illusion in the time domain, I decided to design a speaker that achieves the same likeness in the physical domain.
Inspiration was also drawn from my favorite sculpture at the Washington DC Sculpture Garden:
Having owned a JBL Clip 2, I decided to reverse engineer it in order to replicate its incredibly superior acoustic performance:
Pictured below is the characterization of the frequency response of the signal at the input of the speaker's amplifier (LM48511 class D amplifier) using labview:
Notice the steep roll off below 100hz and the +6db boost centered at 250Hz. This is how the speaker achieves a booming and omnipresent bass from a tiny 1" driver.
Pictured below is the LTSpice simulation of a parametric EQ circuit that achieves the roughly the same response as well as the accompanying circuit realized on a breadboard:
Although this circuit achieved a similar EQ curve, it had a very high noise floor and large distortion at frequencies greater than > 5kHz. So, I decided to scrap the discrete circuit and utilize a the ADAU1761 DSP chip. Pictured below is the GUI tool called SigmaStudio (by Analog Devices) used to generate an identical frequency response to the real JBL Clip 2 :
The chip itself is $11 in single quantities and features a library of basic and advanced DSP functions. You can see in the attached image the use of a parametric EQ block, a block that adds harmonics of signals below a certain threshold to convince the user of strong bass, and a compressor to limit the input signal to the amplifier.
Below is the entire circuit including amplifier evaluation board, DSP chip evaluation board, and a test speaker:
And below is the entire schematic in Altium:
Below is the finalized design with stained wooden edges to produce a visual depth.