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Klipsch 7.4 Surround Sound


A Klipsch GMX series subwoofer. This is part of a ProMedia GMX A-2.1 System including a control module and two satellite speakers. The goal of this project was to integrate the 2.1 system into a full 8 channel system for surround sound gaming for my good friend Constantine Linos.

My friend and I found a ProMedia GMX A-5.1 System at a local pawn shop. Unfortunately, they had only three of the five satellite speakers. In addition, the DIN cable and one of the speaker cables were missing. Here are the three satellites with the speakers from the 2.1 system.

The 5.1 system’s control panel. After testing it with the DIN cable from the 2.1 system, we verified that it was indeed broken.

The control panel opened up. No obvious problems could be identified, so an alternative system had to be devised to drive each speaker channel.

The back of the 5.1 system subwoofer. Klipsch built the amp entirely inside the subwoofer, so each of the five satellite speakers plug in there. The white cable is a spliced RCA cord used a replacement speaker wire.

The back of the 2.1 system subwoofer. It has the same DIN plug as the 5.1 sub.

The DIN plug, up close. Each pin is designated to carry the audio signal for a specific channel, so a trial and error set of tests is necessary to determine what channel each pin corresponds to.

A stereo headphone plug, spliced. Each wire (red=right, white=left, black=ground) is soldered to a lead wire cut from a resistor. The lead’s act a pins that can slide into the DIN socket.

The lead pins stuck in the DIN socket. Music is played from an audio source, and the left and ground pins are placed into different holes of the DIN socket. The ground pin is alternated among the remaining pins until music plays from only one of the speakers. Once the ground pin is discovered, the left channel pin is moved around to determine which pin corresponds to which speaker (FRONT RIGHT, FRONT LEFT, CENTER, SUB, REAR RIGHT, REAR LEFT).

My iPod, hooked up as an audio source for testing. Since I did not have a multimeter handy, I was lucky none of the pins tested had a high voltage that could harm my MP3 player.

The complete mapping of the Klipsch ProMedia GMX DIN socket. The pin holes, in order, when looking at the DIN socket: SUB, CENTER, FRONT RIGHT, REAR RIGHT, REAR LEFT, FRONT LEFT, GROUND. I also cut the DIN cable in half. The colored wires refer to the following channels: sleeve=GROUND, red=FRONT RIGHT, white=SUB, blue=FRONT LEFT, green=REAR RIGHT, orange=REAR LEFT, black=CENTER.

Now that we know the channel mappings, the next step is hooking the two subs up to the computer using four 1/8” headphone plugs.

A set of three 6ft, 1/8” male to 1/8” male headphone cables from Target. Two were cut in half, yielding four 3ft cords. The last was cut at the end for a larger 6ft cord.

First modification: The first DIN cable is made for the 5.1 sub. It is spliced and stripped, ready to be soldered.

Three headphone cords are soldered to the appropriate wires from the DIN cable. The 5.1 sub will handle the FRONT, CENTER/SUB, and SIDE signals from the computer.

The completed DIN cable. The sub signal is not wired to the corresponding pin on the subwoofer. Instead, it is wired to the green stereo headphone plug in the photo.

Preliminary testing showed that there was no crossover built into the sub, so low’s sounded incredibly muddy. The sub’s crossover is actually inside the control panel, so the subwoofer’s signal had to be passed through it first. The green plug from the DIN cable carries the subwoofer signal into the control panel, where the crossover processes it.

Second modification: The working control panel from the 2.1 system is used to process the sub signal. Two RCA wires are soldered to the solder pads of the output DIN socket which correspond to GROUND and SUB OUT.

The control panel closed up. The green subwoofer wire enters the green headphone socket. The processed subwoofer signal exits over the two RCA cables. Subwoofer volume is controlled using the knobs on top of the controller. The unused ports on the back of the controller are covered with electrical tape.

The cables that operate the 5.1 sub, including the control panel.

Third modification: The second DIN cable is made for the 2.1 sub. Since the second sub only runs the REAR channels, just one headphone plug is necessary on the other end.

The complete system. Each wire is color-coded for easy hookup. The four headphone plugs on the left connect to the computer. The two DIN plugs connect to their appropriate subs. The green headphone plug for the sub signal connects to the control panel. Finally, the two RCA outputs connect to each of the subs via their SWS ports (RCA ports Klipsch designed to link extra subwoofers, or in this case, connect the sub signal).

Seven satellite speakers and the two Klipsch subs. Two JVC speakers from a broken mini-system are used as the front channel speakers.

The completed 7.4 channel surround system. The JVC speakers have there own discrete subwoofers (one for each channel), with wiring separate from the main woofers/tweeter. The sub signal from the SWS port is put into a separate amp, the amp is connected to the two JVC subs. The five Klipsch satellites, the two JVC speakers, the two Klipsch subs, and the two JVC subs makes this setup a complete 7.4 channel system.


Costs:

Klipsch 2.1 System FREE
Klipsch 5.1 System $30.00
3x Headphone cables $15.00
RCA speaker cable $6.00
JVC Speakers FREE
Stereo amp FREE
RCA piggyback cable $12.00
Solder/electrical tape FREE

Total $63.00


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