Headphones and Earphones
- Published on 23 April 2009
- Denon AH-D7000 Headphones and Headroom Ultra Desktop Headphone Amplifier
- Page 2: Design of the Denon AH-D7000 Headphones and Headroom Amplifier
- Page 3: Setup of the Denon AH-D7000 Headphones and Headroom Amplifier
- Page 4: The Sound of the Denon AH-D7000 Headphones and Headroom Amplifier
- Page 5: Measurements for the Denon AH-D7000 Headphones and Headroom Amplifier
- Page 6: Conclusions about the Denon AH-D7000 Headphones and Headroom Amplifier
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The data provided below were measured by HeadRoom using an artificial head microphone system. This model head has microphones imbedded in replica human ears, so it listens just as we do. This does make for frequency response plots that are different than we’re used to looking at for loudspeakers. The folds and ridges of the ear cause the high frequency response of a microphone imbedded in a model ear canal to have various peaks and dips caused by in and out of phase interference of sound travelling around the ear. The human brain equalizes this response. We never see these peaks and dips with loudspeaker measurements because they are measured with bare microphones. All headphones will show these high frequency peaks and dips. At lower frequencies, where the wavelength of sound is significantly longer than the size of the ear, there is no effect.
Most headphone manufacturers aim for a couple of dB more bass than flat to add a bit of bass weight and impact that is lost due to the fact that sound waves do not hit the whole body of the listener. Also, note the y-axis scale. Most loudspeakers, when measured in-room, have response variations of over 10 dB from flat due to room effects. Good headphones rarely deviate by more than a few dB from flat since there are no room effects for them.
These measurements, plus measurements for all headphones HeadRoom sells, can be found on their “Build a Graph” page:
Frequency response of the AH-D7000s extends all the way to below 20 Hz. The -3 dB point is about 17 Hz. There is a broad response bump in the bass peaking at about +5 dB at 40 Hz, typical, although lower in frequency compared to most headphones. High frequency response is rather flat until a suckout comes in at about 15 kHz. This suckout is likely due to cancellation in the folds of the simulated ear on the HeadRoom measurement system, as discussed before. It is paradoxically different in the left and right channels, which could have been caused by the drivers sitting on the artifical head differently on the left and right.
Distortion of a 500 Hz sine wave is spectacularly low, with the highest harmonic product just over – 80 dB. This would be good for a preamp, much less a loudspeaker!
Isolation begins to kick in at about 800 Hz, and is an impressive 15 dB or so from about 1 kHz up. Low frequency isolation is basically non-existant. Only in the ear headphones like the Etymotic ER-4S can provide good low frequency isolation. Compared to open back headphones, the Denons have isolation from 800 Hz up, as compared to 5 kHz and up as with my Sennheiser HD-595s.
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