Test Bench: KEF Reference 207/2 Speaker System
In the lab
Frequency response (at 2 meters) front left/right 33 Hz to 17.5 kHz ±4.7 dB Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input) front left/right 93 dB Impedance (minimum/nominal) front left/right 3.5/6 ohms Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room) front left/right 20 Hz at 82 dB 94 dB average SPL from 25 to 62 Hz 102 dB maximum SPL at 50 Hz bandwidth uniformity 92%
The curve 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 207/2 reflects response with the speaker standing on the floor averaged over a ±30° window. All measurements are taken at a full 2 meters, which emulates a typical listening distance, allows the speaker to fully integrate acoustically, and, unlike near-field measurements, fully includes front-panel reflections and cabinet diffraction.
The 207/2 has unusually extended low frequency response and dynamic capability for a tower speaker. Therefore, I also measured bass limits as if the speaker were a subwoofer, and discovered that each tower performs about as well as a small 10-inch sub. The overall response displays a 3-dB wideband elevation above about 300 Hz, along with a series of small, narrow irregularities throughout the remainder of its' operating range. There is also a 4-dB floor bounce notch centered at 160 Hz, and the curve shows that response above 10 kHz fades quickly.
The speaker's LF Adjustment control reduces output below 80 Hz by a maximum 6 dB. The HF Adjustment matched its markings at the +0.75 dB position but only provides about half the specified cut at the -0.75 and -1.5 dB positions.