Test Bench: Klipsch RF-83 Home Theater Speaker System
In the lab
Frequency response (at 2 meters) front left/right: 43 Hz to 20 kHz ±5.2 dB center: 99 Hz to 17.8 kHz ±3.8 dB surround: 117 Hz to 16.6 kHz ±3.9 dB subwoofer: 46 Hz to 108 Hz ±1.9 dB
Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input) front left/right: 96 dB center: 95 dB surround: 95 dB
Impedance (minimum/nominal) front left/right: 2.8/11 ohms center: 2.8/13 ohms surround: 3.1/5 ohms
Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room) front left/right: 32 Hz at 88 dB center: 40 Hz at 78 dB surround: 62 Hz at 74 dB subwoofer: 20 Hz at 91 dB SPL 107 dB average SPL from 25 to 62 Hz 110 dB maximum SPL at 32 Hz bandwidth uniformity 97%
All of the curves in the frequency-response graph are weighted to reflect how sound arrives at a listener's ears with normal speaker placement. The curve for the left/right front channels reflects the RF-83 tower's response with the speaker standing on the floor, averaged over a ±30º window with double weight at 30º (the most typical listening angle). The center-channel curve reflects the RC-64's response averaged over ±45º, with double weight directly on-axis of the primary listener. The surround-channel curve shows the RS-62's response averaged over ±60º. The center and surround responses were measured with the speakers on a 6-foot stand, which gives anechoic results to approximately 200 Hz. Except for the subwoofer, all measurements are taken at a full 2 meters, which emulates a typical listening distance, allows the outputs of large speakers to fully integrate acoustically, and, unlike near-field measurements, fully includes front-panel reflections and cabinet diffraction.
Front & Surround Speakers
The calling card for this system, as with most built around horn-loaded drivers, is efficiency, which is one reason it enjoys such exceptionally high sensitivity. Another, however, is relatively low minimum impedance for all channels. The impedance curves of the RF-83 towers and RC-64 center speaker have a single low point of 2.8 ohms at 180 Hz and climb as high as 11 and 13 ohms, respectively. But the RS-62 surround speaker never presents a load greater than 5 ohms between 200 and 3.5 kHz or above 13 kHz.
Frequency response is quite similar for all channels above 300 Hz, predicting good timbre matching from speaker to speaker, but all exhibit a fair degree of roughness as well. The RF-83 and RC-64 have unusually good low-frequency extension and measured Bass Limits for their respective channel assignments. As with most floorstanding speakers, the RF-83's response dips at 200 Hz because of acoustical interference from a floor bounce. The RC-64, on the other hand, distinguishes itself with off-axis response that indicates only moderate lobing. The RS-62's response, like that of all bi-directional speakers, tends to flatten out off-axis; it is uniform to both sides of the speaker, on the other hand, which is not always the case.
We measured the RT-12d's bass limits with it set to maximum bandwidth and placed in the optimal corner of a 7,500-cubic-foot room. In a smaller room you could expect 2 to 3 Hz deeper extension and up to 3 dB greater sound-pressure level (SPL).
This RT-12d has strong, uniform dynamic capability across its full range of frequencies, based on a maximum distortion threshold of 10%. Bass Uniformity was an impressive 97%. Maximum output, 110 dB SPL, occurs at a relatively low 32 Hz, and a minimum of 105 dB SPL was available at any frequency in the sub's range from 25 Hz and upward. Hooray! This is Olympic-class performance.
The sub's controls performed largely as advertised. Turning the crossover control downward also tended to modify static response at lower frequencies, however. For example, with the crossover set to a marked 40 Hz the lower -3-dB point shifted to 27 Hz and the upper point was 55 Hz, and overall level was reduced by 8 dB. From a marked 80 Hz and upward, the true crossover point was about 10 Hz lower than the marking but there was little volume/crossover interaction. The adjustable crossover slopes matched the true acoustical slopes reasonably closely, and there was only a moderate volume interaction. The "Punch" EQ setting added 2.6 dB below 65 Hz, while the "Depth" EQ added 3 dB at 60 Hz.
Because my facility does not suffer significant modal problems, I had to solicit locations where modes would form that were not at listening positions in order to test the RT-12d's room-correction circuitry. I found that Room EQ tended to work in moderation, addressing modal irregularities with finesse and understatement. It under-compensated both peaks and dips below 100 Hz and simply applied level adjustment for seats where response was already flat. I was able find a spot 5 feet from the floor where the EQ simply cut output by 6 dB below 100 Hz when the "problem" was a 125 Hz peak just outside the EQ and subwoofer bandwidth.