Desktop Stereo System: In Pursuit of Excellence

Jeff YirakBy Jeff Yirak, P.E., CPMP, LEED AP BD+C, O+M

In my last post on the subject, I charged a capacitor to install in my desktop car stereo (desk stereo?) system. It’s not much of a system; it’s actually just a 600-watt amplifier bridged for mono channel operation and a 12-inch subwoofer supplementing some typical full-range computer speakers. Hey, what better way to boost worker productivity that with some soothing infrasonics? Here’s how I did it.

Subwoofer

Let’s start at the end. The subwoofer I’m using is a JL Audio W3v2 12-inch woofer with dual six-ohm voice coils. Wiring the voice coils in series yields a twelve-ohm impedance, while wiring them in parallel yields a three-ohm impedance.

How to wire the subwoofer terminals

How to wire the subwoofer terminals

The impedance will affect the amount of power that the amplifier can put out, as subject to Ohm’s law. Ohm’s law says that V = I*R, where V is voltage (volts), I is current (amperes or amps), and R is resistance (ohms). Power is equal to V*I, or solving for I, V/R. Decreasing the resistance will increase the power and increasing the resistance will decrease the power (holding voltage constant). There are some good reasons to go for a higher impedance, but if what you want is power, go for the lower resistance. I wired the sub for three-ohm duty.

The subwoofer must be in some sort of enclosure. The front of the woofer needs to be isolated/separated from the back of the woofer so that the pressure wave created by the cone’s movement isn’t canceled by the opposing wave created on the back of the cone. Subwoofers are typically installed into boxes made of wood, either particle board or medium-density fiberboard (MDF). I chose a vented enclosure with about 1.25 cubic feet of internal volume. This is a little smaller than the ideal size for this woofer, but it fits under my desk well.

Jeff's subwoofer under his desk

With the dark carpeting, this thing practically disappears.

Amplifier

Following the speaker wire from the subwoofer, we next go to the amplifier. I have a SoundStream Reference 2.640 class AB amplifier. This is a beefy unit that will crank out 640 watts RMS into 4 ohms if given 80 amperes of 14.4 volt DC electricity. That’s more power than I need at work, so I’m only providing about 25 amperes at 13.8 volts (from the power supply I used to charge the capacitor). With this much electrical input, I’m only capable of generating about 200 watts, but that’s still enough to make myself heard throughout the office. The amplifier is also not rated to operate into three ohms in bridged mode, but I’m never going to exceed the current capacity of this amp with this power supply, so I’m safe.

Inside an amplifier

The amplifier’s guts. Image Source: http://www.diymobileaudio.com/forum/1658470-post2.html

The amplifier is installed on my cubicle wall, in plain sight, but most people don’t even notice it. Even if they do, they don’t know what it is. I like the anonymity that this provides. When I feel like listening to music during the day or messing around early in the morning, sometimes someone asks me, “Do you hear that?” I just say “Huh; must be a truck outside”.

In terms of office setups that play music, this system is gross overkill, but that’s why I like it. The standard has been set for desktop stereos, and in my opinion, set pretty low. This setup says a lot about me; why settle for normal when you can be excellent? Indeed.

 

Follow Jeff on Twitter @ JYirak_WH

This entry was posted in All Insignts, Commissioning, Electrical Engineering, Mechanical Engineering. Bookmark the permalink. Post a comment or leave a trackback: Trackback URL.

Post a Comment

Your email is never published nor shared. Required fields are marked *

You may use these HTML tags and attributes <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

*
*