Two Towers by José Cordero-Medina

Unfinished Loudspeaker

Left-Right speakers capable of full frequency range and meeting Dolby standards for cinema playback. Designed to provide a cheaper replacement to the current sound system in Walker 134. Center channel also designed, not yet built.

Overall Design Goal:

Provide Dolby standards for cinema playback to Walker 134. System capable of outputting 85dB SPL at audience distance with a 20dB headroom and an additional 10dB for the Low Frequency Effects unit.

Cabinet Construction:

5-sided box removes parallel surfaces reducing resonance in particular frequencies while also providing directional sound for maximum even coverage. 3/4 in layer of 13ply plywood outer layer and 1/2 in inner layer of MDF combine to provide rigidity to the cabinet as well as support for its size of 5’5″.

Drivers:

Each of the drivers were first and foremost chosen for its sensitivity and secondly for its compatibility with each other. Unfortunately, not all have perfectly flat response, reducing the overall frequency response balance, thus not making them suitable as professional mixing speakers. They do offer great sounding playback worthy of cinema speakers.

Cross-Over:

Very simple design with some additional parts for driver attenuation. The tweeter has a 1st order Buttersworth at 1.8kHz crossing over to the midrange with a 3rd order Buttersworth at 1kHz. The tweeter has a baffle step correction above 4kHz of -5dB, the midrange has a -3dB pad and the entire cross-over has a -6dB pad. The midrange rolls off naturally at the bottom end. The woofers have an interesting testing error cross-over that ended up working. As testing and tuning went by, I was changing the crossover from a 3rd order Buttersworth at 150Hz to 100Hz. I changes the capacitors, but not the inductors. Not sure what kind of cross-over it really is now, but it did what I needed it to, so I left it. It also has a notch filter at 200Hz to get rid of an overlap with the midrange driver.

<a rel=”license” href=”http://creativecommons.org/licenses/by-nd/3.0/us/”><img alt=”Creative Commons License” style=”border-width:0″ src=”http://i.creativecommons.org/l/by-nd/3.0/us/88×31.png&#8221; /></a><br /><span xmlns:dc=”http://purl.org/dc/elements/1.1/&#8221; href=”http://purl.org/dc/dcmitype/Sound&#8221; property=”dc:title” rel=”dc:type”>Michigan Tech Transducer Theory Dolby Speakers</span> by <span xmlns:cc=”http://creativecommons.org/ns#&#8221; property=”cc:attributionName”>Jose Miguel Cordero Medina</span> is licensed under a <a rel=”license” href=”http://creativecommons.org/licenses/by-nd/3.0/us/”>Creative Commons Attribution-No Derivative Works 3.0 United States License</a>

System Tests:

Frequency Response

Driver Responses

X-Over Responses

Harmonic Distortion

Horizontal Frequency Response

Step Response

Minimum Phase Response