Polk RTA 11t loudspeaker Page 2

The crossover circuitry is mainly carried on a printed circuit board attached to the rear of the terminal panel, with the exception of the series air-cored inductor in the woofer feed, which is wound on a circular molding integral with the panel. The low-pass filter for the woofer is second-order, a polarized electrolytic capacitor shunting the drivers, while the tweeter high-pass also appears to be basically second-order. However, a resistor in series with the shunt air-cored inductor and another in parallel with one of two series capacitors give a hybrid response, where the filter's output gently tilts down below 12kHz with then an initial 9dB/octave rollout slope. A series voltage-dependent resistor in the tweeter feed provides protection—normally very low in value, it changes to a high resistance when the speaker is overdriven in order to cut the current flow to the drive-unit. Internal wiring is all 18AWG.

The cabinet is covered with a "furniture-grade" vinyl finish and is constructed from 3/8" fiberboard, with ¾" MDF front and rear baffles. The sides are braced horizontally, and a front-to-back brace adds further stiffening of the enclosure. The top of the cabinet is filled with what appears to be acrylic fiber, and all the drive-units are rebated into the baffle.

Sound quality
The RTA 11ts were positioned well away from room boundaries, as the mid-bass became too heavy when the speakers were placed within 3' of the rear wall. Sidewalls were 5–6' away. As my floor is quite heavily carpeted, I tried using Tiptoes to clean up the upper bass/lower midrange, but the metal studs on the speakers' bases defeated this, the speaker sliding off the smooth top surface of the cones. At low levels typical of casual background listening, the sound of the RTA 11t was quite seductive, a rather loose, rounded bass quality being allied to a feeling of air and space in the treble. Upon more critical listening, however, it became apparent that although the speaker is tonally well-balanced through the midrange, the overall characteristic resembles the familiar saddle-shaped "loudness" contour, where emphasis in the treble and bass compensate for the ear's low sensitivity at the frequency extremes at low listening levels.

The peak in the high treble exaggerated spit and sibilance in spoken male voice, and could be heard as a metallic signature added to recorded tape hiss, though paradoxically, the treble in total sounded rather recessed and shut-in. Violin tone, as well as the sound of the flute on the Stereophile Poem LP, was too warm, and lacked HF air. Despite the presence of the high-treble peak in the speaker's response, the speaker was too laid-back, apparently due to a lack of energy in the presence region. At high levels, however (spls in the 90s), the sound took on a treble hardness which had me reaching for the volume control.

Lower down in frequency, a hooty lower midrange added to the feeling of a warm tonal balance. Again, this was not unpleasant at low levels, but at more normal playback levels the speaker featured a significant degree of resonant overhang in the lower midrange. This was particularly bothersome on my own piano recordings, where the definition of pitch became obscured. On slow music, or when the melodic line being played lay well above the treble staff, things were relatively OK, but with contrapuntal music lower down in frequency, the sound of the piano degenerated into an unclear mess. Similarly with orchestral music or rock music with a complex mix: the sound was acceptable as long as things were quiet and simple, but when they got complicated and loud, instruments seemed to obscure each other's tone colors, the result being an untidy, muffled effect.

In this respect, the RTA 11t performed significantly less well than the two much less expensive speakers reviewed this month, the Cambridge SoundWorks Ambiance and the Monitor Audio MA7. The Ambiance may have a less flat tonal balance than the Polk speaker, and it is certainly more "colored" in that sense. But it has considerably more clarity, there being much less resonant overhang in the lower midrange, and it is more listenable as a result.

Polk Audio
5602 Metro Drive
Baltimore, MD 21215
(800) 377-7655