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
- All Pages
If there is one phrase to describe the sound quality of the Denon/HeadRoom combo, it is “jaw-dropping.” One of the main drawbacks of headphone-based audio is a lack of low bass. Most headphones are simply not capable of producing large amounts of low bass due to the small size of their drivers and the small volume of air moving. Any serious bass below 40 Hz is hard to achieve, and any sense of power and weight in the bass region as a whole normally comes with excessive bloat and boom. Most good headphones end up sounding light in the bass, although still quick and agile. The AH-D7000s, with proper amplification, turn this paradigm on its head. I knew the bass was good, so one of the first tracks I listened to was Daft Punk’s “Human After All.” At moderately high volume level, I though the bass was going to implode my skull. Not that there was more bass than there should be, by the way. This particular track has a huge amount of very powerful low bass. The subterranean frequency extension and sheer power delivered by the AH-D7000s put my home system to shame, 500W monoblocks, subwoofer amplifier and dual voice coil woofers and all. Any loudspeaker that could deliver bass like this would cost many tens of thousands of dollars. The bass was also stupendously fast, agile and tonally accurate. Since there are no room effects between the driver and your ear, none of the normal acoustic effects that plague loudspeakers in a normal listening room are present. Over the course of a couple of months as the drivers broke in, the bass became even more tonally accurate and tight than when I first listened to them.
Midrange and treble tonal accuracy and presentation of timbre were also first rate, a trick for a sealed headphone. Most high performance headphones are open baffle designs. Sealed loading of the driver usually results in a closed in and tonally muffled midrange, but the Denons have been carefully engineered to avoid this fate. Tonal accuracy is at least as good or better as the Sennheiser offerings I have had the pleasure to listen to (HD 580, HD 595 and HD 600). High frequency smoothness and extension were also essentially perfect. Transient response and speed matched or exceeded any headphones I have ever heard.
Headphone soundstaging is somewhat different than normal loudspeaker soundstaging. Typically the soundfield seems to be inside and around the head. For me, the center of the soundstage is between my ears, inside the head. As sounds move “farther back” in the soundstage, they seem to sound to come from above my head. Similarly, the left and right of the soundstage seem to be inside my head near the left and right ears, and extend out beyond my head to the left and right. This results in a soundstage plane that is vertical, not horizontal. With the AH-D7000, the soundstage ranged from inside my head to 1 to 1.5 feet outside my head. This is the largest perceived soundstage I have heard with headphones. This was facilitated by the HeadRoom amplifier’s crossfeed circuit, which mixes some of the right channel into the left (and vice versa), through a time delay and amplitude filter. This simulates the effect of sound waves from the left and right stereo channels in free space (i.e. from a loudspeaker), which eventually get to both ears but at different times and at different volumes. The crossfeed can be defeated, but this results in the soundstage collapsing to three “blobs” of sound, left center and right.
When compared to my pair of Sennheiser HD-595s, the Denons were superior in every way. The soundstage was larger and more airy, transient response and speed were superior, treble extension and smoothness were better. Midrange smoothness and tonal accuracy was also greatly improved with the Denons. The bass was no contest, although there is no headphone I have ever heard that can compete with the Denon’s bass, period. The sealed design of the Denons was also preferred to the Sennheisers when any background noise was present. Compared to my pair of Etymotic ER-4S, the Denons were also superior in every way. The Etymotics have a bass shy balance anyway, and since they are in the ear headphones there is no air movement around the ear to reinforce the weight of the bass. The Etymotics do offer vastly superior sound isolation (23 dB vs 8 dB for the D7000s), allowing for fantastic detail retrieval in the face of background noise. Of course, you won’t be able to hear your phone ring either.
I also used my battery powered HeadRoom Total Bithead to power the AH-D7000s. This portable amp is also a headphone amp with a built in DAC. The DAC is USB input only, and does not offer sample rate conversion or as high a quality DAC. The headroom amplifier module is of a similar design and uses upgraded parts as compared to the standard module. It does not use the super high quality OPA627 op amps, and is powered by 3 AAA batteries rather than a beefy power supply. Every area of performance, while still listenable and WAY better than an iPod, was significantly degraded. The AH-D7000s want a lot of power to deliver their bass punch, and midrange and treble agility and speed. The total bithead made an effort, but could not keep up. The DAC was also a bit grainy and dynamically flat by comparison. While a full-up Ultra Desktop is not strictly speaking necessary to enjoy the AH-D7000s, the headphones will benefit from every bit of improvement you can provide in the source and amplification electronics.
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