Anatomy of a Center Channel: Why Horizontal Speakers Fail (And How Physics Fixes It)

In home theater design, there is a fundamental conflict between Interior Design and Acoustical Physics. For a speaker to fit neatly under a television, it must be wide and short. However, arranging speaker drivers horizontally creates a notorious acoustic phenomenon known as Comb Filtering.

This is why, with many center channels, you have to sit in the “dead center” to hear clear dialogue. Move two feet to the left, and the voices become muffled. The Klipsch RC-64 III serves as a fascinating case study in how to cheat this geometry using a sophisticated engineering technique called the 2.5-Way Tapered Array.

The Horizontal Hazard: Comb Filtering

To understand the solution, one must understand the problem. When two woofers play the same frequency simultaneously, their sound waves interact (Physics). Ideally, they sum together perfectly. However, if you are sitting slightly off to the side, the sound from one woofer reaches your ear micro-seconds later than sound from the other.

At certain frequencies—specifically in the critical vocal range of 1kHz to 3kHz—this time delay causes the waves to cancel each other out. This creates “lobes” of silence and volume peaks in the room. For the listener, it sounds like the actors are mumbling or speaking through a tube. This is the inherent flaw of the standard MTM (Mid-Woofer - Tweeter - Mid-Woofer) design found in most budget center speakers.

The 2.5-Way Solution: The Tapered Array

The Klipsch RC-64 III utilizes four 6.5-inch woofers. In a basic design, all four would play the same bass and midrange frequencies. This would be an acoustic disaster, creating massive interference patterns.

Instead, Klipsch engineers implemented a 2.5-Way Crossover Network (Engineering). * The Inner Pair: The two woofers closest to the tweeter handle both Bass and Midrange frequencies, reaching up to the crossover point of the tweeter. * The Outer Pair: The two outer woofers reinforce only the Bass frequencies. Their output is electronically “rolled off” or attenuated before they reach the higher midrange frequencies where interference occurs.

So What?: By filtering the high frequencies out of the outer drivers, the speaker effectively acts as a single point source for the critical vocal range. This eliminates the horizontal interference, ensuring that the person sitting on the far end of the couch hears the same crystal-clear dialogue as the person in the sweet spot.

The Cerametallic Rigid Body

The drivers themselves are subjected to immense mechanical stress. The cones must accelerate and stop instantly to reproduce voice articulations. Klipsch utilizes Cerametallic™, an anodized aluminum core sandwiched with ceramic.

This material pushes the “break-up mode” (the frequency at which the cone starts to flex and distort) well outside the operating range of the crossover. Combined with the cast aluminum baskets, these drivers operate as pure pistons (Physics), minimizing the harmonic distortion that often clouds deep male vocals.

Controlled Directivity: The Tractrix Horn

While the woofers handle the width of the soundstage, the Tractrix® Horn manages the tweeter’s dispersion. A standard dome tweeter sprays sound 180 degrees, bouncing energy off the floor and ceiling. These reflections arrive at your ear slightly later than the direct sound, smearing intelligibility.

The 90° x 90° horn acts as an acoustic lens. It restricts the sound energy to the listening area, reducing floor and ceiling reflections (Acoustics). This increases the ratio of direct-to-reflected sound, which is the primary metric for Dialogue Clarity.

Field Note: Because of the horn’s controlled directivity, precise aiming is critical. If you place the RC-64 III on a low cabinet, you must angle it upwards towards your ears. If the horn is firing at your knees, you will lose the high-frequency detail required for speech intelligibility.

The Klipsch RC-64 III is not just a “loud” speaker. It is a precisely tuned array designed to overcome the physical limitations of horizontal placement. It solves the lobing problem not by magic, but by intelligent signal filtration.