DCM TF-1000 Speaker System Review

From the outside, the DCM Time Frame TF-1000 speaker looks similar to a number of planar or dipole panel speakers, but it is actually a more or less conventional three-way for-ward-radiating system. The enclosure is a folded, tapered transmission line that loads the rear of an 8-inch woofer and is terminated by a 2-1/2-inch-diameter port on the front panel. All three active drivers are located on the upper half of the panel. The woofer is nearest to the bottom, a 4-inch midrange driver is near the top of the panel, and a 3/4-inch soft-plastic dome tweeter is between them. The transmission line’s port is slightly below the woofer but on the speaker’s rear panel. The Time Frame TF-1000 is designed to be used in mirror-image pairs, with the drivers closer to the inside edges of the cabinets.

According to DCM, the system is delay-equalized for correct on-axis time coherence and improved off-axis response smoothness. An acoustic lens in front of the tweeter is claimed to improve its on-axis high-frequency smoothness and its off-axis high-frequency response. Its voice coil is cooled by a low-viscosity ferrofluid in the magnetic gap. The woofer is constructed with an aluminum voice-coil former to improve its power-handling ability and efficiency.

The TF-1000’s specifications include a frequency range of 26 to 20.000 Hz, a sensitivity of 91 dB sound-pressure level (SPL) at 1 meter with a 1-watt input, and a nominal impedance of 8 ohms. The system is rated to handle 50 watts of continuous pink noise, or 300 watts of peak program material, and is recommended for use with amplifiers delivering between 10 and 200 watts per channel. There are no level or balance adjustments.

The DCM TF-1000 stands 49 inches high and measures 19-1/2 inches wide and 8 inches deep. Extra support can be provided by a pair of short feet that swing out from the base. Weight is 49 pounds. Except for its oak top and bottom, the enclosure is fully wrapped in a nonremovable black grille cloth. The spring-loaded clips in the rear accept twin banana plugs as well as wires. There are no external fuses or other signs of overload protection. Price: $1,099 a pair.

Lab Tests

The composite frequency-response curve of the DCM TF-1000 (derived from the room response and a close-miked woofer measurement) was notably smooth and uniform, varying only ± 3.5 dB from 26 to 20,000 Hz. Between 1,000 and 11.000 Hz, the averaged output level varied only ±0.5 dB. There was a plateau between 200 and 1,000 Hz, about 3.5 dB above the high-frequency level, and a slight peak of about 3 dB at 150 and 15,000 Hz.

The bass output sloped off gently below 100 Hz. The effective crossover between the woofer and its port radiation was at 60 Hz.

The speaker’s measured sensitivity, 1 meter from its grille at the approximate height of the tweeter, was 85 dB SPL with an input of 2.83 volts. Though this fell short of the rated 91 dB, it is not very different from what we have measured from a number of good speaker systems. The woofer’s distortion, at an input of 5 volts (equivalent to our standard 90-dB reference SPL), was between 1 and 2 percent from 100 to 50 Hz, rising smoothly to 5 percent at 30 Hz and 7.3 percent at 25 Hz.

The system’s impedance varied widely throughout the audio range. Although it averaged roughly 6 to 8 ohms, its minimum levels were 3 ohms at 200 Hz and about 5 ohms from 5,000 to 20,000 Hz. The maximum was 20 ohms at 1,500 Hz, with a 16-ohm peak at the bass resonance frequency of 47 Hz. In pulse-power tests at frequencies of 100, 1,000, and 10,000 Hz using a single-cycle burst followed by 128 off cycles, the amplifier clipped before the speaker’s output became audibly nonlinear at power inputs from 500 to almost 1,300 watts.

Our quasi-anechoic FFT measurements confirmed the previously observed response variations as well as the essential smoothness of the TF-1000’s frequency response. The horizontal dispersion was very good; the response on-axis and 45 degrees off-axis diverged only moderately at frequencies over 10,000 Hz. This test did reveal some midrange cancellation effects in the off-axis measurements, probably caused by the asymmetrical driver arrangement on the panel.

The phase coherence of the system was outstanding. Its group delay varied less than 0.05 millisecond overall from 4,500 to 20,000 Hz (presumably the tweeter’s operating range, although the crossover frequencies were not specified by the manufacturer). From 1,000 to 20,000 Hz, the delay variation was 0.2 millisecond. Even at lower frequencies, where much larger phase shifts (and group delays) are usual, we measured an overall delay variation of less than 5 milliseconds between 100 and 1,800 Hz.

Comments

For our listening tests and measurements, we placed the DCM speakers about 2 feet in front of a wall, where most speakers seem to sound their best in our listening room. The sound was so pleasing that we were not encouraged to experiment much with their location. Although these speakers are not as large as they look, they are highly visible nevertheless. In a sense, since they occupy little floor space, they could be ideal “large” speakers for an ordinary-size room.

In many cases a speaker’s sound does not correspond with what one might expect from its measured performance, but the DCM TF-1000 was an exception. Even a brief audition left no doubt that it is a very wide-range speaker, with no particular emphasis on any part of the audio spectrum. In particular, there was little sign of the upper-bass emphasis that mars the reproduction of male voices by so many speakers. The general effect was of clarity and transparency. Compared with our reference speakers, the sound of the TF-1000’s seemed more open and sharply defined, a trifle brighter, and with somewhat less deep-bass extension. These characteristics are completely consistent with the measured frequency responses of both speakers.

Overall, the DCM TF-1000’s were very easy to listen to for extended periods. Their sound lived up to the promise of their unusual design and stood up exceptionally well in comparison with a number of other speakers in their size and price range—and with some more expensive speakers as well.

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