ART USB Dual Pre
Behringer B2 Pro
Denon DP-61F
Dynaco ST-70
Hafler DH-110
Hafler DH-500

  Hafler XL-280
Klipsch KG1
Mogami/Canare RCAs
Nakamichi CM-300
Scarlett 2i2
Tannoy 603
VOX Pathfinder 15


  • I bought this audio system new in 2000 for my PC and have enjoyed it since day one. Now after 15 years, seeing that Klipsch still produces this THX-rated system implies its a pretty solid design. But I suspect some parts may be a bit tired and there was likely some cost-cutting in the original unit...I decided its a perfect candidate to modify.

    I have read the original sub used a Class D amplifier for the woofer and separate Class A/B amplifier for the satellites. While mine contains a large transformer and power supply, more recent versions of the Promedia have much smaller boards with tiny transformers. This could be due to miniaturization over the years but I wouldn't be surprised if highly efficient Class T amplifiers are being used today.

    The first step in any assessment is to open it up and see what's inside. What I found was surprising. Instead of a set of "drivers in a box", Klipsch actually made the satellites into real speakers. The cabinets contained white fiber-fill, and the crossovers use a 6db slope with higher quality parts than I've seen in some floor speakers. Good job Klipsch!

    A generic "CAPEX" 4uf 100v NP electrolytic cap is used on the tweeter. While this cap isn't audiophile quality, for a small computer speaker it's acceptable. However, I measured them at 4.75 and 4.83uf which is close to 20% out of tolerance, not good. A 5 ohm 5W resistor pads the tweeter. An iron-core inductor is used on the mid-woofer.

    The mid-woofer appears fairly robust with a foam surround and a long-throw magnet. The heavy, dual-magnet design is unusual for a tweeter...especially in a speaker meant to receive only 35 watts max. This "overdesign" is an unexpected but welcome sight.

    The Control Pod (below) beneath one speaker is slides back and comes out with a bit of fiddling. Inside are some electrolytics just begging to be changed out. The four on the top left are 10uf 50v polarized caps which if you look at the schematic are the input caps for each channel. In a peculiar move they are wired as reversed pairs to create two 20uf NP caps. A NP cap is actually two separate polarized caps reversed inside a case...but this is the first time I've ever seen separate pairs soldered this way. I'm guessing it was for space considerations. The other two caps are 100uf 16V. A TLO74CN low-noise JFET op amp and assorted resistors, diodes, etc, round things out.

    NOTE: If you follow the circuit, the musical signal from the PC first travels to the Control Pod under the speaker... through the "20uf" NP input cap circuit...back down to the the HF amplifier inside the sub...then out the speaker jacks to the satellites. This means optimizing the Control Pod circuit will have an audible effect on the sound quality.

    2ND NOTE: using speaker spring-clips on the back of the sub where they can be easily kicked loose is a poor design. As with stereo receivers, it's common for exposed speaker wire ends not to be pushed in all the way...and easily short the wire next to it. I suspect this is where many reports of these subs being unreliable came from.

    The mini-pin input on the back of the speaker is not a good choice for a speaker rated for 35 watts. In fact, if you own this system you are likely familiar with having to fiddle with the mini-pin jack on the speaker every time it cuts out. Others who have modded this speaker came to the same conclusion: replace it with a pair of binding I bought an inexpensive set of "mini" binding posts online from Parts Express.

    The existing mini-pin is easily removable from the inside of the cabinet. Minus all the extra collars and plastic base the new metal binding post fit perfectly into the existing hole. I then measured and carefully drilled a hole for the upper post, using one of the new binding post collars to insert in the hole from the inside for strength. The result are two posts that appear "factory" and sit the same height. Think this through before you drill, as you can't drill a hole smaller(!)

  • Next I replaced the input caps on the Control Pod with 10uf 50V Elna Silmics. I find Silmics to have a smooth, open sound with accurate bass. Slightly large but they fit perfectly. Due to space limitations I changed the two 100uf caps to Nichicon VRs. VR's are quality general purpose caps with neutral sonic character and are excellent in modern circuits. The circuit inside the sub itself is working fine and I don't see the need to replace any of that circuitry yet.

  • BELOW: Now this is a great looking crossover. I replaced the marginal electrolytic on the tweeter with a Dayton 1% 4uf 250V metallized polypropylene. I have used the Daytons over the years in crossovers and find them to have a clear, accurate sound with no hyper detail...very musical. I left the resistor and inductor alone.

  • CONCLUSION: For now I am using the existing stock wiring in the speaker and the stock speaker wire with the mini-pin snipped off. And yes the sound quality has definitely changed. Music is much more open with a detailed 'presence' that didn't exist before. Imaging is now rock solid with vocals hanging in 3D space between the actual soundstage exists. Transients and guitar zips are more detailed and bass is tighter and more integrated with the music. The sound is simply....better.

    While the effects of the mods are cumulative I believe the biggest improvement was likely getting rid of the old electrolytic caps on the tweeters that were 20% out of spec. For under $25 this mod has been very successful and will make this system enjoyable for another decade. Ā© 1997-2018
All mods are illustrative only, perform at your own risk.
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