For years my 5.1 home theater speakers have all been Klipsch. The fronts are vintage Forte IIs, the center a RC-62II, and the rears RS-35s. The exception was a decade old Pinnacle Digital 600 12" sub that had given me good results. But recently when playing music at high volumes the sub struggled. The bass maxxed out and the punch flattened a bit compared to the rest of the system. I began looking at replacements but I'm not a fan of rear ported subs that direct bass to the rear wall. This causes reflections and make EQing the room more difficult in my opinion. So when looking at Klipsch subs I ruled out the Synergy and Reference models and went right to the top tier: the SPL series. Klipsch is crafty using the name SPL as the acronym for Sound Pressure Level implies that this sub series means business. One spec that jumped out at me was the maximum acoustic output of 118db as my old Pinnacle was only 108. I also liked the menacing slot across the bottom of the front grill. This uses a folded horn design to aim bass towards the listener which has been a Klipsch concept for decades.

Internally the 120 uses a highly efficient class D amplifier rated at 300w (600 peak). Class D uses a PWM circuit similar to digital instead of using an old-school power supply like class A/AB, producing 90% or higher efficiency. D's also typically refresh at 50,000hz instead of the slow 60hz of the past. This super-tight power supply regulation allows Class D amps to handle 1 ohm speaker loads with ease. They also run cool making D perfect for sealed subwoofers.

A long-standing trope is that bass is non-directional but I don't agree. While bass drivers don't need to be pointed at the listener its easy to hear where in the room deep bass is emanating. So I believe in using dual-subs for balanced room response. I usually open up speakers when I first unbox them to see the interiors but decided not to on the 120. This sub was securely braced and tested for high volumes and I worried opening it up could disturb the factory integrity. After doing a EQ room sweep I put on several test songs that had stressed my old sub. My goal was deep, powerful, bass with no compression or fluttering at extreme levels. If anyone can pull this off its Klipsch who for decades has designed speakers for maximum performance, not for the prissy audio salon crowd.

For sub demos I use mainstream music and try to only play WAV, FLAC, or blu-ray audio. I stay away from mp3s and analog recordings made before the advent of digital. My tunes may not seem too esoteric. But the deep bass in these recordings is surprisingly hard for woofers to play properly at high volumes.

WAV AUDIO
John Pardi- Dirt on my Boots
The Weeknd- Blinding Lights
Sublime- What I Got (reprise)
Gorillaz- Saturnz Barz
Metallica- Nothing Else Matters

BLU-RAY AUDIO
Cream- Live at Albert Hall 2005- Crossroads
Taylor Swift- Reputation Live Tour- Ready for It
Avatar- The opening scene

For my interconnects I bought a bulk length of Mogami W2552 cable and constructed a 10ft pair with RCA jacks to reach reach the opposite corners of my room where each sub sits. But during placement I was faced with an issue: my receiver only has a single RCA output for a subwoofer. The age-old solution is to use a Y-cable to split the signal into two lines. But a single RCA jack pushing a signal through two 10 ft long interconnects into two separate components worried me. Was this one output capable of driving both at high volumes? Could a shared circuit be introducing artifacts or be loading down the sub output at the receiver, even slightly? Considering the time and money spent on optimising all aspects of my home theater wiring I didn't like this arrangement.

So I took a tip from the guitar world which is familiar with using a preamp to bolster signal strength between pedals and rack equipment. As a test I ran the Y-cable from my sub-out on my receiver to a quality stereo preamp and from the fixed preamp outs to each sub. The effects were exactly what I expected. Deep bass was more intense and refined, less boomy. The overall bass soundfield felt more accurate and correct. High volumes were tighter and more robust. I had no doubts about the results as using a preamp as a buffer is an accepted method for sound reinforcement, not snake oil. I found the best combination of bass and soundstage was to place the subs about 1 foot from the side walls facing forward.

Subwoofer reviewers are an interesting crowd. They seem to enjoy pointing out minor shortcomings or the lack of 1hz of response instead of focusing on musicality and all-around performance. Well, the SPL-120 is rated down to 24hz and I'm not sure I understand the hand-wringing. Yes there are subs that reach lower but the 120's high-volume musicality and low distortion make it a standout. Keep in mind there is little bass content below 27 hz unless its from movie effects or a synthesizer. In my case I found the 120 to be clean and accurate through the whole bass register with very deep room-shaking power. The response was tight and controlled even at the very highest volumes, no chuffing or distortion. I tried my best using my torture-tests but was not able to trip it up once. There was never that cringe-moment where I knew an effect was coming that I was worried the volume was too high. I found fine-tuning the crossover point on the back of the sub made a big difference, even though my receiver had preset the levels. One interesting find was that the auto-on circuit correctly cuts in between beats, my old sub would start midway into the 2nd beat which was jarring.

So did a pair of SPL120s make for an improvement over my old sub? A huge one.