Tech Spec Differences Between Sirius and XM (and new satellite)

[tedb3rd]

I know that Sirius and XM are now 'one company' but what about the hardware?

I have heard SiriusXM (via factory radio in Chevrolet) and also Sirius (in Saturn with wired FM modulator to Starmate5 receiver)... The sound quality sounds better in the Saturn compared to the Chevrolet... Obviously the Starmate is pulling from Sirius's satellite and I'm assuming that the Chevrolet is pulling from the XM satellites (since that's what Chevy factory radios carried before the merge). To me, the 'compression sound' (that 'jar' sound that was audio over the internet back when 56K was fast) seems a lot higher on the XM compared to Sirius. Has anybody else noticed this?

I saw in another post that SiriusXM will be launching another satellite soon. What are their plans? More channels and/or improving sound quality and/or other??

 

[DustoMan]

The Sirius and XM services are running in parallel despite the fact that the companies are now merged. Taking one of the services offline without warning would cut off that customer base. One of the end goals of the XM 2.0 transition is to unify the services by basically phasing out the Sirius-side of the service over the course of 3 years and recovering that spectrum so it can be used more channels with better more efficient compression and hopefully better sound quality. I don't think they are launching a new satellite, there was a leaked document a year or so back that detailed the transition and I don't remember it being mentioned.

This is what Wikipedia says about how XM is compressed. I don't know when this was compiled and how accurate it is:

Audio channels on XM are digitally compressed using the CT-aacPlus (HE-AAC) codec from Coding Technologies for most channels, and the AMBE codec from Digital Voice Systems for some voice channels, including all of the Traffic and Weather channels.
The XM radio signal is broadcast on 6 separate radio carriers within the 12.5 MHz allocation. The entire content of the radio service, including both data and audio content, is represented by only two carriers. The other 4 carriers carry duplicates of the same content to achieve redundancy through signal diversity. The data on each carrier is encoded using time-delayed and error-correction schemes to enhance availability. Effectively the total radio spectrum used for content is a little over 4 MHz.[SUP][29][/SUP]
Each two-carrier group broadcasts 100 8-kilobit-per-second streams in approximately 4 MHz of radio spectrum. These streams are combined using a patented process to form a variable number of channels using a variety of bitrates. Bandwidth is separated into segments of 4-kilobit-per-second virtual "streams" which are combined to form audio and data "channels" of varying bitrates from 4 to 64 kilobits-per-second.[SUP][30][/SUP]
XM preprocesses audio content using Neural Audio processors that are optimized for the aacPlus codec, including spectral band replication (SBR). Audio is stored digitally in Dalet audio library systems using an industry-standard MPEG-1 Layer II at 384 kbit/s, sometimes known as Musicam. The audio is further processed by the Neural Audio processors on the way to broadcast.

XM Satellite Radio - Wikipedia, the free encyclopedia

And here's a forum post I found that kinda cooberates some things and lists reasons why 2.0 is using the XM system instead of Sirius that I found interesting:

* XM uses an audio codec known as HE-AAC, or aacPlus v1. It's designed to deliver higher quality audio at bitrates lower than 96 kbps (192 kbps MP3). Sirius uses a less efficient codec called ePAC, which takes more data to deliver at the same quality as HE-AAC. XM also uses the AMBE codec for its voice only data channels, aka the robot voice channels, which uses a mere 4 kbps.

* XM's infrastructure has the ability to move bandwidth around at will, turning channels on and off as needed and turning bandwidth up and down. Sirius channels stay on all the time, unless they're permanently deleted. They find ways of preserving bandwidth using a system like Statmux, where a group of channels have varying bitrates based on what other channels need. Satellite TV uses this too.

* XM is able to alter the channel information on its units at the push of a keystroke. If a channel is replaced by a new one, they can simply change the channel name and logo on the units. Sirius is unable to do this without shutting down the entire system and rebooting it, which causes all units to go dark for a few minutes. For a while this was routine, but Sirius hasn't done a reboot for over two years now.

* While all XM units can receive all channels, many Sirius units have a limit of 135 channels, and this includes a LOT of OEM radios. This is why XM has been adding several Sirius channels to its platform but Sirius has hardly added any XM channels. Sirius has mainly added XM channels to its Best of XM premium package, which brings the platform total over the 135 channel barrier, so the limited Sirius units have simply been deemed Best of XM incompatible. This is also why the newest Sirius XM channel, Spice Radio, has a full time channel on XM while existing part time on Sirius, sharing channel space with Sirius XM Stars Too.

Print Page - SiriusXM Moving to XM Technology

 

[navychop]

It will be interesting to see if that leaked document is still relevant or had any truth to it at all. I wonder how long before we'll know. When people in NYC and elsewhere start complaining that the terrestrial repeaters are down?

 

[DodgerKing]

I know that Sirius and XM are now 'one company' but what about the hardware?

I have heard SiriusXM (via factory radio in Chevrolet) and also Sirius (in Saturn with wired FM modulator to Starmate5 receiver)... The sound quality sounds better in the Saturn compared to the Chevrolet... Obviously the Starmate is pulling from Sirius's satellite and I'm assuming that the Chevrolet is pulling from the XM satellites (since that's what Chevy factory radios carried before the merge). To me, the 'compression sound' (that 'jar' sound that was audio over the internet back when 56K was fast) seems a lot higher on the XM compared to Sirius. Has anybody else noticed this?

I saw in another post that SiriusXM will be launching another satellite soon. What are their plans? More channels and/or improving sound quality and/or other??

I would bet that the sound quality had much more to do with the audio system and setup than which satellite it comes from.


I can say this though. Before the merger XM was many times better. I would never lose signal, even under small tunnels. Now I lose my signal just going next to a tree. XM had many ground repeaters, which Sirius slowly done away with. The XM rock stations were much better and they did not have a single DJ or person talking at all on any of the rock stations. Even more importantly, the music library was much more vast.

 

[tobsandmags]

I've lost track on what's going on with SiriusXM 2.0 and the transition referenced in this thread. The "leaked" document referenced in the earlier post talks about ground repeaters being phased out. There was talk in other threads about 1.0 radios becoming obsolete (or not). New channels were going to be made available only for the new 2.0 radios (although I can't tell from the SuriusXM site what they are). Do new cars have the 2.0 radios and, thus, get more channels? There was also some conversation about Pandora-like personalization of stations. Anyone have a summary if what's going on?

 

[MIHotBear]

I would bet that the sound quality had much more to do with the audio system and setup than which satellite it comes from.

I can say this though. Before the merger XM was many times better. I would never lose signal, even under small tunnels. Now I lose my signal just going next to a tree. XM had many ground repeaters, which Sirius slowly done away with. The XM rock stations were much better and they did not have a single DJ or person talking at all on any of the rock stations. Even more importantly, the music library was much more vast.

Not totally true. Squizz always had DJ's. Bodhi, Grant Random & Atticus to name a few. You are right about the music library though.

 

[kingofku]

I would bet that the sound quality had much more to do with the audio system and setup than which satellite it comes from.


I can say this though. Before the merger XM was many times better. I would never lose signal, even under small tunnels. Now I lose my signal just going next to a tree. XM had many ground repeaters, which Sirius slowly done away with. The XM rock stations were much better and they did not have a single DJ or person talking at all on any of the rock stations. Even more importantly, the music library was much more vast.

I did some contract field work for Sirius a few years back replacing defective HPA's they were using for their terrestrial repeaters. It was a pretty slick system as I recall. There was a 1.2m antenna that snagged the signal out of the sky which in turn fed a proprietary receiver. The output of this receiver would feed some processing equipment then on to the HPA (high powered amplifier) where that output would send it's RF signal to 4 2.3gHz antennas strategically mounted on four corners of the roof, pretty much ensuring coverage in a directions. The HPA wasn't putting out much power.....maybe 75 watts or so.


The equipment racks were built by Globecomm Systems out of Hauppauge, New York. They are a pretty good sized integrator and do excellent work.

 

[aegrotatio]

The Sirius repeaters tuned to a Ku-band transponder on AMC-16 and rebroadcast them.

The XM repeaters took two of the four transponders from one (or both) of the XM 85-degree or 115-degree satellite and rebroadcast them.

It's arguable to say which system was more elegant, but the XM system was probably less costly due to not requiring the use of another satellite feed just for the repeaters, though it did require two receivers instead of just one receiver as with the Sirius design.