HD Radio, Audio Signal Quality? - Page 2

I just want to add my two cents based upon what I hear here in the Akron/Cleveland market. A case study is 89.7 WKSU Kent Ohio. They run 4 HD channels including their primary. Their main channel is an NPR/Classical mix whereby they essential pick up the network show feeds, until the need for Classical music programing prevails. HD-2 is "Folk Alley" a typical reasonable quality feed of Folk Music. HD-3 is a Classical Music channel that never gets the NPR feed interruptions; it also in stereo. HD-4 carries a mirror of the main channel during the day in MONO and BBC news programming at night.
Gentlemen! HERE IS THE ISSUE. They do it WELL considering the digital "payload" they shell out. They BACK OFF VOLUME and that sheds sampling burden from huge amplitude spikes making their subs sound much better than they would otherwise!! You have to trade off volume level to get this done! I recently made a YouTube video of this with the audio output sampled directly to wav then transcoded to mp4 to accompany video of my actual switching of channels. I believe that the main HD-1 channel is at parity or 0dB reduction. The HD-2 channel is down 6dB and the HD-3 Classic Music channel is down 12dB the mono channel is either down 6 or 3dB I don't recall, but obviously somebody gave tremendous thought as to how to minimize that "TIN PAN/STEEL DRUM" obnoxious artifacting that always occurs when you choose to "DOG PILE" A PLETHORA OF HD SUB-CHANNELS. You can't over drive your subs. Something tells me there has to be a deliberate trade off of UNDER SAMPLING as to NOT tax the limited bit rate real estate. You can't go BLASTING every sub channel you have if in fact you're hosting more than 2.
I would LOVE to hear comments from engineers that get to play with these settings. How do the PD or GMs interact? Do they argue about max volume? So many CHRs red line their boards and make further natural "punch" an impossibility to correctly recover.
I would think that the so called "volume wars" have NO place in an HD environment however, these days so many outlets use super squeezed data compressed (not to be confused with gain reduction compression) sub-par audio formats far below FLAC and WAV to inject their analog sound with. It sounds like mp3 crud PERIOD. The "dumbed down sound" is ubiquitous and extremely annoying to this child of the 60's. FM peaked in the 80's. AC station had their (you know what) together! HD was a way to bring this back but if the general consensus does not maintain these cherished ideals, sooner or later it will be "any goes" hits the digitizer audio blender and what comes out to hit your ears, may no longer be akin to a "smoothy" palatable for your auditory taste buds.

Great point. These days, the radios will do the volume changes FOR you. Not as much need to smash the heck out of the audio. Commercial analog radio is still gonna do that just because nobody wants to be the "quietest" on the dial. It's a "thing" you'll never get program directors to part from. But when you transition from our analog to digital, there's a noticeable change in dynamic range and a slight change in maximum level. Probably because we have an engineer who's a freak about these things. We're carrying two music subchannels, so both are down around 3-6db from the main. The HD3 still sounds tinny at times, but that's the way the programming arrives. We aren't the originators. I still think our HD2 sounds the best of all of them. Peak limiter is all it has on it, AFAIK.

And, yes, we have "Artist Experience" running on HD1 and HD2 of two of the stations in the cluster, now. Can't do it on the HD3s since WYCD-3 is originated elsewhere and WOMC-3 is psychic/lifestyle talk.

Except for the classical station! I used to listen to the local classical station when they were broadcasting 96 Kbps. The sound quality was amazing. It was the only station I would be willing to compare with my CD collection.

Then they added an HD-2. Now the 48 Kbps audio sounds identical to their analog audio. I honestly can't tell any difference.

Thank you for the informative description of the signals. The part I quoted above is what interests me most. Here in the S.F. Bay Area, we have one specific station that has three digital channels (KITS 105.3), and its HD2 channel is quieter than the main channel, with the HD3 being quieter yet. This bugs the heck out of me! I have always thought of radio as being a casual source of music, so I accept the limits (pun not intended!) of the sound quality. Part of that is accepting that music will be compressed compared to CDs, and every non-classical station runs at the same general volume level, and they always have for the decades I have been listening to FM radio. That makes it easy to flip among numerous stations to find songs I like (or will at least tolerate) without making other adjustments. Now these sub-channels "mess up" the whole equation, and if I stop on one of them (really, only KITS-HD2, because their HD3 is a very odd format), I need to change the volume and then get blasted when I move on to another station later. It is very annoying! Other stations seem to sound just fine running two digital channels, so if this is a side-effect of having three or more streams, I hope they KILL it soon. This is the first trade-off of quality for quantity that I really dislike in broadcast radio.

I don't think that you will have to be concerned with "quieter HD sub channels" becoming a trend.. It does cut against the grain of maximized audio that the PD's generally crave. This remains a technical solution for the better presentation of sub-channel audio without the typical level of "perceived" artifacting that often plagues it.
One of the best sounding non-classical stations in my market (Akron/Cleveland Ohio) is 98.5 WNCX. They run their HD-2 channel in MONO and it is rock music based. I believe they are a CBS radio outlet. Their audio is true to classic rock audio. You will hear unobstructed detail. It is a listening experience for Classic Rock, a very open detail orientated sound. They even have the AC channels beat when it comes to clarity and discolored processing. It remains an iconic demonstration of how well HD audio can aid in detail recovery when done right and when the primary HD audio is both protected and processed in as transparent a means as possible. Whoever decided to set them up, did so with great integrity. If HDradio.com were to run a column on fan based feedback on audio quality coming from their local stations, this one would rank very high IMHO for a non-classical format effort. Their FM analog is decent with a bit more limiting and obvious pre-empahsis gain reduction issues that are a function of the limits of FM MPX processing in general.
One other station deserves honorable mention for their effort to protect the integrity of their main channel HD audio. Hot AC 98.1 WKDD which serves up two MONO sub channels; my favorite local sister station AM news talker WHLO (640) and they started offering a mono version of Air One on their HD-3. A trend seems to be towards protecting their main HD-1 channels these days rather than blindly obscure them by deliberately cutting their bit rates in half. My only bone with this station is that the processing sounds artificially punchy by the falsely exaggerated sound of percussive sonic elements being processed as natural dynamic restoration.
My apologies for covering many subjects under one reply which was based on the anti loudness wars sub channel "minority report". The central theme here is the creative strategies for dealing with the HD radio format in the efforts to GROOM it for more faithful sound across the finite bandwidth spectrum afforded it on a station by station basis. No size fits all, but you can witness great efforts that individuals take upon themselves to improve their sound and have signature efforts worth touting.