I spent the better part of this afternoon listening to my new HD Radio receiver, the Sony XDRF1 HD, tuning through the Chicago FM dial. There are 33 FM stations broadcasting HD in Chicago according to iBiquity, which owns the technology. I was able to tune in the HD signal for 19 of them. After several hours of listening I remain rather unimpressed by HD Radio.
Primary HD Channels
First off I will address the question of sound quality and fidelity. iBiquity claims “drastically improved sound quality” for HD Radio over its analog counterpart. I do not agree with this claim. Tuning between the analog and primary HD channel for each station I could perceive slight differences in sound quality between them. The biggest difference is the loss of background noise and hiss in the HD channel. Now, this is a very subtle difference, primarily perceptible during quiet music passages (which are rare on commercial FM) and voice breaks. This leads to the perception that there’s a bit more dynamic range on the HD channel, but it requires fairly high listening volume to clearly detect.
While I welcome the lower noise floor of HD, I otherwise don’t perceive any other significant increase in fidelity. On nearly every station I listened to the primary HD channel sounded nearly identical to the analog FM. Much of commercial FM is overcompressed, and I found that if a station’s analog signal was so overprocessed, so was the primary HD channel.
Sometimes I would lose the HD signal–since it’s broadcast at a much lower power level than the analog signal–and I never noticed just by listening. I had to look at the tuner’s display to know for sure. The shift between the HD and analog signals is pretty smooth sounding on the Sony tuner. I can tell when it happens, but it’s quite unobtrusive. If I’m not paying close attention to the radio it can happen without me noticing.
All of the 19 HD FM stations I received are stations that come in reasonably well in analog in my apartment in the Rogers Park neighborhood on the far north side of Chicago. The Sony XDRF1 turns out to have very good analog FM performance, bringing in the analog FM signals of these stations better than any other radio in my house except my Tivoli Model One, which is another room. Of the 10 stations where I couldn’t tune in an HD signal, 8 of them don’t come in clearly in my house in analog, either. For two stations my tuner did not indicate there was an HD signal present. More details listening notes by station are at the end of this post.
Secondary HD Channels
The other big advantage touted for HD Radio are the additional subchannels a station can have. Each HD station I listened to broadcast one or two additional channels. By and large the second HD channel had decent sound quality, but that nevertheless never matched the quality of the primary analog or HD channel. This should be expected because there is only so much digital bandwidth for each station to exploit, and the FCC requires that the primary HD channel–which must have the same programming as the analog signal–have the biggest share of the bandwidth.
The second HD channels typically sound like a good webcast station. That is, they sound like medium-quality MP3s with bitrates of 128 kbps or lower. I hear more compression and less dynamic range than the analog side, and some rolling off at the high end. Right now I’m listening to WXRT’s commercial-free HD channel 2 called “Channel X” and it’s pleasant to listen to, no more fatiguing than most web stations.
The stations broadcasting only on additional HD channel had slightly better fidelity on their HD-2 channels than those broadcasting three digital channels. Chicago Public Radio WBEZ broadcasts its Vocalo service on HD-2 and has no HD-3 channel. It sounds a little fuller than WXRT’s HD-2, with better stereo separation, a little more high end, and a little more dynamic range.
WXRT also broadcasts an HD-3 music channel which is branded as last.fm, owned by the station’s parent company CBS. The fidelity on HD-3 is greatly compromised, sounding like a webcast from the late 90s. The highs are heavily rolled off, with lots of shimmery distortion on high pitched instruments like cymbals. I find it pretty unlistenable and think it’s a waste to try and cram music on the HD-3 channel.
The stations that air talk programming on their HD-3 channels are much more listenable, mostly because voice-only programming just doesn’t require as much bandwidth and fidelity as music. WUSN airs a motorsports talk station on its HD-3 channel, and while the programming isn’t my cup of tea, I could imagine listening to it if it aired something of interest to me.
The HD Experience
Listening to HD Radio is not necessarily the most user-friendly experience. The digital HD signal is broadcast at much lower power than the analog signal–in order to lessen interference with adjoining stations. Therefore I had to adjust my antenna carefully to pull in HD signals. The Sony tuner provides a nice signal strength indicator which aids in this task, flashing an HD indicator when a digital signal is detected. You know you’ve got a HD signal tuned in when the HD indicator stops flashing, and more data–like song titles and station name–is displayed.
I have a fifteen-year-old Radio Shack amplified FM antenna that is tunable to frequency. I found with careful tuning I could successfully receive the HD channel for every available station. However, keeping that HD signal was sometimes difficult. Just walking across the room could cause the HD signal to drop out. The HD signal also seemed more susceptible to electrical interference than analog FM. For instance, my wife was shredding documents in the next room, and every time she shredded something the HD channel would drop out, then take 10 – 30 seconds to come back in after she stopped.
Now, it’s true that I live about 10 miles from downtown Chicago, where most major stations are located, on the second floor of an all-brick building. It’s not the ideal location to listen to radio, but not the worst, either. I’ll argue that at least 60% of the metro radio audience lives at least as far away as I do, so I think others’ experience would be similar to mine.
On some stations it was difficult to listen to the HD channels for any length of time. They just wouldn’t stay tuned in, no matter how carefully I adjusted the antenna and tried not to move around. It’s not a big deal if I’m listening to the primary HD channel, since the tuner smoothly falls back to analog, which sounds just as good. But it is frustrating if you’re listening to an HD2 or HD3 channel, since it goes away altogether. No slow degradation, no static–it’s either on or off.
Given the somewhat delicate nature of tuning in HD stations, I have real doubts how many average radio listeners are willing to devote the patience necessary to tune in HD channels. Sure, any radio listener is used to having to move an antenna or radio to get better reception. However, with analog a listener can hear the changes when reception degrades or improves. With HD it’s all or nothing, and therefore much more difficult to finely tune. Furthermore, hearing a crystal-clear analog signal does not necessarily mean you’ll get a clear digital signal. I can only imagine how frustrating it is to try and listen to a portable HD Radio, since just maintaining a clear FM signal with a portable can be a real challenge.
Finally, one of the great experiences of analog radio listening is scanning the dial looking for a good (or tolerable) song, or simply just trying to see what you’ll find. This is not a pleasure one will enjoy with HD radio. In my experience so far it really just isn’t practical to scan HD stations. It simply takes too long to get the HD signal locked in. Perhaps someone living downtown near the major stations might be able to do this, but I just don’t see it happening elsewhere.
I will continue to listen to HD Radio in order to see if the experience improves or I figure out some tricks to improving reception. But so far I find that the technology of cramming a digital signal in next to analog one has too many compromises to be successful. The bandwidth for the HD channels is not enough to offer significantly better fidelity for the primary HD channel, and the leftover bandwidth available for HD2 and HD3 provides sound quality that does not surpass what is available online or on satellite radio. Importantly, tuning in a clear HD signal can be a very finicky process that can try one’s patience. How many signal drop-outs will the average listener endure before giving up on an HD2 or HD3 channel?
As I mentioned I did my listening with a Sony XDRF1-HD tuner which is generally highly regarded for its fidelity and performance on both analog and digital FM. I amplified the audio with a harman/kardon AVR25II receiver, which is a very high quality unit from the mid-90s. The receiver is well maintained and provides quite nice sound quality in plain 2-channel stereo that well exceeds most receivers you’ll find for under $1000 in the electronics store. The speakers are RTR28 bookshelf speakers and an Audiosource 100 watt subwoofer. Laying this out is my way of saying that I believe the electronics were up to task of fairly evaluating the sound quality of HD Radio.
These are the HD stations I listened to, with some listening notes as relevant:
- 91.5 WBEZ HD1 HD2 – HD2 had some of the best sound quality I heard on an HD2 channel.
- 93.1 WXRT HD1 HD2 HD3 – HD3’s music quality was too compressed and nearly unlistenable.
- 93.9 WLIT HD1 HD2 – HD2 is music, sounds OK.
- 95.5 WNUA HD1 HD2 – HD2 is music, sounded above average.
- 96.3 WBBM HD1 HD2 – HD2 is music, sounded average.
- 97.1 WDRV HD1 HD2- HD2 is music, heard high end “shimmery” distortion on cymbals.
- 97.9 WLUP HD1 HD2 – HD2 sounded average.
- 98.7 WFMT HD1 – No HD2 or HD3. HD1 sound quality was the best I heard.
- 99.5 WUSN HD1 HD2 HD3 – HD3 had talk which sounded adequate.
- 100.3 WILV HD1 HD2 – HD2 was talk and sounded very good for that format.
- 101.1 WKQX HD1 HD2 – HD2 was music and sounded decent, but somewhat compressed.
- 101.9 WTMX HD1 HD2 – HD2 was 80s music, pretty highly compressed.
- 102.7 WVAZ HD1 HD2 – HD2 is religious talk, sounds OK.
- 103.5 WKSC HD1 HD2 – HD2 is music, sounds average for HD2.
- 104.3 WJMK HD1 HD2 – HD2 is sports talk, sounds OK.
- 105.1 WOJO HD1 HD2 – HD2 is music, sounded slightly above average. HD3 is music, sounds poor.
- 105.9 WCFS HD1 HD2 – HD2 is simulcast of WBBM-AM. There was a lot of artifacting on HD2, not as clear as the station’s webcast.
- 107.5 WGCI HD1 HD2 – HD2 is music, sounds average.
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