DCM Time Frame TF1000 loudspeaker Measurements

Sidebar 2: Measurements

The frequency response the speaker was measured in the listening window—spatially averaged to minimize room standing-wave problems—using a 1/3-octave warble-tone generator, which is said to be a little more analytical than the filtered pink-noise signal I have used in the past; in addition, the nearfield low-frequency response of each speaker was measured with a sinewave sweep to get an idea of the true bass extension relative to the level at 100Hz. The change of impedance with frequency and the voltage sensitivity (using 1/3-octave pink noise centered on 1kHz) were also measured.

Measured sensitivity at 1kHz is high, at around 95dB/W, rather higher than specification and something for which I have no explanation. Looking at the impedance curve (fig.1), the main LF resonance can be seen at 43Hz, with the line/port tuned to 27Hz, suggesting, all things being equal, that the TF1000 should have good LF extension. In general, the TF1000 should not be a hard load to drive, though as the impedance drops to below 5 ohms through the upper bass as well as in the mid treble, reasonably gutsy amplification, in current-delivery terms, would be best. (Even considering the high sensitivity, the TF1000s would not be an optimum match for an inexpensive Japanese receiver.)


Fig.1 DCM TF1000, electrical impedance (solid) (5 ohms/vertical div.).

The measured nearfield LF extension gave a –6dB point at 39Hz (rel. to 100Hz), though this does not take into account the reinforcement of low bass from the port. In-room, the low bass rolled off quite gradually, with useful extension down to 30Hz (fig.2). Given the well-damped nature of the low frequencies, the TF1000s could be positioned closer to the rear wall to boost the upper bass without a resultant boom, if this were felt necessary. The tweeter response seemed civilized on-axis, without too much of the presence-region emphasis endemic among soft-dome units. It was also well-controlled off-axis, suggesting that the lens used by DCM does do the job. The slightly rising response through the midrange suggests a somewhat, though not excessively, forward balance.—John Atkinson


Fig.2 DCM TF1000, spatially averaged, 1/6-octave response in JA's original Santa Fe listening room.
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dalethorn's picture

I loved the original DCM Time Windows, and I passed over them only when I decided to get the Dahlquist DQ-10's for the living room and LS3/5a's for the upstairs. The 1970's was an amazing time for speaker innovation, what with the three that I mentioned, the Bose 901, the Advents, the HMT's, and some great floorstanders like the HQD's, the IMF's, and the FMI's to name a few. The big ones were out of range of my budget then, but it's remarkable what I could afford on what would be a $50k salary today.

I've read here about how audiophiles can get much more for their money today, in terms of sound quality compared to the 1970's, but if those "affordable" speakers today are bland-looking boxes like the Advents were then, then I wouldn't be too excited about a review comparing, say, the 12 best affordable systems of the 1970's to the 12 best affordable systems of this decade. But, if there were much to be excited about with today's systems, aesthetically as well as for sound quality, that might make an interesting review.

Anton's picture

When I was in college, I had a buddy who had a pair of these with a pair of Bose 901s sitting on top. His system was in a low ceilinged basement with peeling paint on the concrete walls. Lots of tapestries and head shop type decoration/accessories.

The 'Apocalypse Now!' soundtrack played back on his Linn table was hallucinogenic.

Talk about more than the sum of its parts.

I will love them forever.

monetschemist's picture

... in the Audio Critic. I wanted them so badly...

For me that magazine was "shocking" in the truest sense of the word. Could there really be the kind of differences in equipment that were noted in the early days of TAC?

Whatever, I bought into it hook line and sinker. My fourth cartridge was a Fidelity Research FR1 Mk3F, thanks to TAC. My first MC head amp was a Marcof PPA-1, thanks to TAC. I bought and built a Hafler DH-200, thanks to TAC. I never did manage to find Time Windows nor Fouriers nor Threshold here to listen to (probably a good thing, but anyway).

Fortunately for me, the magazine was even harder to find in Vancouver than some of the gear they recommended, and when I moved offices in 1982 or so, I was no longer near the Vancouver Public Library main branch where I could find TAC back issues.

When TAC went off in new directions claiming that everything sounded the same, I was once again shocked. And by then, I didn't really believe it.

By the way if anyone is still looking for a DH 200 or a PPA-1 let me know (joking, sort of).

The O.D.'s picture

I purchased a pair of the DCM Time Window 7s back in 1996 or 1997 (can't remember which year). 20 years later, they still sound as impressive as they did the day I bought them. I just recently updated to a set of the Paradigm Signature S6's, and with the exception of those fantastic Beryllium tweeters in the S6's, the Time Windows still hold their own. The old DCM made some impressive stuff before they went under.