View Full Version : Audio Quality (cross-post from RNZI reception reports)

05-08-2006, 14:56
I noted (as Brendan pointed out) that the RNZI's bitrate is up again. Thanks RNZI :)

Now on to something completely different. Are any of the US DRMers also Satellite Radio fans? I recently acquired a Sirius portable for my car. I'm enjoying all the channels, but am quite dissapointed in the audio quality.

I turned on one of the News channels and my wife immediately said "does it always sound underwater?" She was right, it was quite bubbly. Much like (but worse) than Radio Kuwait on DRM. Now RNZI, CBC, RNW , HCJB & all the stuff tested for NAB sounds/sounded LOADS better.

I even noticed that the less-compressed music channels on Sirius aren't all that hot. I heard "Let's Dance by Chris Montez" and whatever form of Stereo they were using rendered it almost unlistenable. That song has "abused stereo" from the 60s (keyboard in one channel, voice in the other) and when the lyrics came in, the voice completely knocked out the keyboard. Yikes!

My point is this: audio quality (with all the "new" technology) seems to be a thing of the past. This current generation of kids will never know the warmth of full frequency. Hell, makes me want to get out an LP and listen to mids and highs again. Don't get me started on the quality of cell-phone audio :eek:

I certainly applaud improvements such as AAC+ and the like, and for shortwave anything better than 14kbps aac+ is a big improvement over analogue AM. I guess I expected more from Satellite radio. I'll likely listen to WRN and Old Time Radio shows rather than music on Sirius anyway.

Rant off. Any comments? I guess I oughta move this to another board.

05-08-2006, 16:02
Hi Christopher,

we don't have XM and Sirius in Europe except perhaps 21 XM channels in WinAmp via internet with 16 kbps AAC+, but we have the northwest beam of Worldspace Radio's AfriStar.
Worldspace Radio is an old system with max. 64kbps MP3. This may be a relatively good quality for tropical africa, but not here in europe.
Even on european satellite DVB the bitrates of radiostations often are only 96 or even 64 kbps mpeg2 mono.
DAB in GreatBritain is also running with bitrates far below 128 kbps.
Today's generation has different values, let's keep ours. ;)
I still enjoy my 4-way 600W stereo with klipschorn and ringradiators. :D

05-08-2006, 16:17
Sorry Chris, no XM or Sirius here. I'm enough of a pennypinching cheapskate to not shell out the subscription fees. :mad: If they were free-to-air, probably.

Shelling out the money for DRMSWR and an RX320D was plenty, but I've not regretted it. After all, the radio can be used for signals other than DRM... :D

That, and HF is more challenging. There is no challenge to satellites.

09-08-2006, 00:38
I now have listened to WRN, CBC and BBC channels on Sirius. So the broadcasters that I listen to / have listened to that are on DRM & Sirius are the following: Radio Netherlands (via Sackville and Antilles), Radio New Zealand, BBC , CRI (only in analogue), Radio Sweden & CBC/RCI.

The verdict is in...DRM SOUNDS BETTER! I know that many of you might be surprised, but the so called "news/talk" stations on Sirius are REALLLLLLLLY compressed. I'm VERY familiar with all of the above stations, and they all (CRI excluded) sound much more pleasant and listenable on DRM. Sackville (when it comes in) sounds quite nice. The RNW Antillies braodcasts are great too. So far, RNZI is the best sounding of all of them, even at a lower bit rate than Sackville.

I do have a question regarding mode C. It appears that here is only a small sacrifice in audio quality to get a significant gain in robustness. Why don't I see stations in C mode? I think there is a 16.4 or so bit rate in C (close to the 17 whatever bit rate). Also, is there any difference in bitrate or robustness for transmitting in P-Stereo vs. mono when using AAC+?

Anyway, I'd judge Sirius at perhaps 11kbp to maybe 14kbp equivalent. Anybody know for sure wht they are? What is DAB using? How about XM?

11-08-2006, 04:36
OK I ran Sirius through SpectrumLab software and looked at various channels. My ears were correct; "voice" only type channels are narrower audio bandwidth than music. Music channels look to be about 12k. Voice channels vary. BBC & CCN looked to be solid 8k. WRN was clearly 7k. The most compressed of all were the Weather and Traffic channels which looked to be between 5k-8k.

So, I sent DRM (RNZI) through spectrum lab. Sure enough, 11k but less amplitude compression. Sounds better than the Sirius voice channels (overall) and nearly as "wide" as the Sirius music channels. This is RNZI running a 10khz DRM signal, B mode, SDC 16QAM, MSC 64 QAM, 0 protection level, 17.28 EEP AAC+.

I REALLY feel there is hope for DRM in as far as people are already "living with less" audio quality in a "for fee" service like Sirius! C'mon Sangean and others, get those radios (at reasonable prices) out to the world and let's work together to save Shortwave :)

11-09-2006, 15:02
From Sirius' FCC application for a new satellite. Looks a little "bloated" per my tests, but it is their word against mine :D

Compression rate (§ 25.144(a)(3)(iii))
Currently, Sirius’ music channels are compressed to approximately 50 kb/s and normal voice channels to approximately 20 kb/s (the rates are approximate due to Sirius’ use of statistical multiplexing). Special channels (e.g., traffic/weather) are compressed further to 16 kb/s and ancillary ones are either not compressed or compressed as appropriate. The compression will change over time with technology advancement.


11-09-2006, 16:07
I have been told by an expert in the field that Sirius uses a less efficient codec with inferior audio quality than does XM.
Since I haven't heard it myself, I can only pass this on without further comment.


11-09-2006, 17:41
Curious [from this side of the Pond] to know what we (DRM types) are up against with DAB? I have likewise heard Sirius uses a less efficient codec, but don't have XM to compare.

My current feeling is that all the DRM I have heard (except Kuwait) blows Sirius talk/news channels away. Music on Sirius sounds better than the 20K music stuff I have heard on DRM however (CBC, RNW, TDP, RNZI, HCJB, etc).

The difference between AAC and AAC+ is HUGE. RNZI is running AAC+ and it does sound good.

14-10-2006, 07:12
Here in UK DAB uses MPEG layer 2 coding (MP2) which is old, but several 1.5Mbs muxes are in use using VHF band III in the UK (also L band in Europe and Far East). Band III VHF in UK, unlike most countries, is no longer used for TV, so about 8 MP2 radio stations (64k-192k) can be fitted in each mux.
There is a development where DAB becomes Digital multimedia broadcasting (DAB-IP, DMB or DAB+) which allows either a low definition mobile TV or the more modern AAC+ radio to be included in the existing DAB 1.5Mbs muxes alongside the old MP2 stations, DMB radio and TV tests are in several European and far east countries and the data ident streams are now compatable with DRM data ident streams so in therory a user will not need to know the type of transmision, but the new DAB/DRM sets the EPG will work it out after a scan.
As DRM is restricted to 10khz bw on MW/SW, giving a max of about 30kbs for the audio in good conditions, except in Austrailia or NZ where 20khz bw is allowed and the audio stream is therefore better, band III DAB/DMB radio will allways beat DRM radio in sound quality untill DRM+ is allowed in VHF (FM) band 2?.

In the US I think XM uses AAC+ but is incompatable with DRM, Sirius uses an older PAC codec so is not as efficent using the dsat b/w as XM but can vary the b/w depending on the station.
HD radio seems to use PAC but with AAC+ type enhancements, but as band III is still in use in US, has to fit into the existing AM/FM bands with potential interference issues.

Once the designs of the new combined DAB/DMB/DRM software upgradable radios are settled then there could be a HD/DRM set for the US. It's an interesting step forward that Sangean who are working closely with Dimplex/Roberts/Morphy Richards on DAB/DRM sets, will soon have HD in the range, see http://www.sangean.com/.

I also see that AAC+ v2 is now out giving even sound quality potential for DRM.

06-11-2006, 14:07
I will offer a thought. CRI audio is about the worst "feed" in quality on DRM. I am fairly certain this is not just on DRM as they sound about the same per my times with them on analogue (overdriven and distorted). Kuwait's audio due to bitrate is the worst I've heard on DRM, but it is unclear how bad the feed is. CRI's bitrate settings however seem to have very few artifacts, considering they are using a 16/16, 14k format.

I'm quite impressed overall with the 14k setting being used. All of this being said, I am surprised with the variance in DRM audio quality over the different bitrates. Since we hear equpiment made by different manufacturers, does anyone have an idea "which" manufacturers have the best sounding hardware?

I'd say if CBC could clean up their feeds (low level rumbling, crackling noise and odd cross talk from other programs during silence) they would be about the best. RNZI has no noise during silence, but artifacts are present at almost any bitrate. Montsinery is a bit more compressed and nearly as good.

All of these judgements are based on my ears, speakers and headphones. I feel safe in commenting as I think I have heard all of them enough to begin to see a pattern.