Over-modulation

[toshiba tony]

Hello all, just a quickie, does anyone think DAB and internet radio is over modulated, I'm pushing into a couple of Rogers floor standing speakers and cassette, CD, phono, and TV all sound OK but on my new dab tuner it's harsh, I've put balancing components on the input which improves it, I'm going for a mismatch but it sounds a bit like multipath from the old days, any ideas anyone? Ta.

[Nuvistor]

Anyway of checking the output from the tuner? Radio 3 should be a good test, if that’s poor it could be a fault in the tuner. Audio manipulation is different for each transmission type, the commercial stations seem to limit the dynamic range more than the BBC, or at least they did.

[G6Tanuki]

What do you consider 'over-modulation' ?? Part of me thinks this will depend on what you are listening to.

For the last half-century, AM broadcast-radio has used various techniques [both analog and digital] to fit more audio-content into the available channel; from brute-force amplitude-clipping through RF-speech-processing [there were a bunch of designs widely published in the ham-radio mags, from the 'Radio Liberty' stuff and the late David Tong's DATONG RF speech-processor, one of which I have here and which gets regular outings on 80 Metres].

Compression/clipping to make broadcast-signals sound 'fuller' and so better able to overcome noie/fading is really nothing new. Extended to Internet Radio, personally I don't have a problem with it [there again, I don't have 'golden ears' - following an explosion I'm basically deaf below 300Hz].

Indeed, a while back when listening on FM to BBC Radio3 for a friend, when the music stopped playing and there was something which I perceieved as ten seconds of silence, I began wondering what had failed!

I like my audio-bandwidth to be full-fat and turned=up=to=11.

[paulsherwin]

DAB will sound much worse than typical internet streams or even Freeview on good equipment, because of the low bitrates and heavy digital compression used. The codecs have improved, but not *that* much. Even the best DAB tuners can only decode what's there.

The BBC abandoned HiFi DAB about 20 years ago, and the commercial broadcasters have never cared about sound quality. Most DAB stations are mono. It's simply not a HiFi medium as implemented.

[toshiba tony]

well. thats plenty info to chew over, i always thought cd was too clinical but i adapted in the end, thanks all

[Roger Ramjet]

Originally Posted by paulsherwin

DAB will sound much worse than typical internet streams or even Freeview on good equipment, because of the low bitrates and heavy digital compression used. The codecs have improved, but not *that* much. Even the best DAB tuners can only decode what's there.

The BBC abandoned HiFi DAB about 20 years ago, and the commercial broadcasters have never cared about sound quality. Most DAB stations are mono. It's simply not a HiFi medium as implemented.

I read via another forum that the bit rate is higher on a freeview tuner as opposed to the maximum rates available on DAB. So it is likely Tony that you may see an improvement using the TV / Radio as a source instead of the DAB Tuner. Obviously the Freeview radio stations are limited & it's a great shame that BOOM RADIO is not there !

Also picking up on Paul's comment regarding mono DAB .......I find that some of the mono stations on DAB actually sound a lot better than their stereo counterparts (albeit via my Roberts portable).

Rog

[paulsherwin]

Freeview radio streams do indeed use higher bitrates than their DAB equivalents, though it's still not really HiFi. A redundant Freeview box can make a useful audio tuner, but they can be awkward to use without an attached display.

[G6Tanuki]

There'a also a lot of rather good-quality audio streams available on FreeSat [rather than Freeview] from various European/Middle-Eastern sources.

[a friend records off-air broadcasts from the Israel Philharmonic Orchestra broadcast on an Israeli satellite-channel; the audio quality seems really rather good, though a bit more dynamic-range-compression would be appreciated by my lead-ears].

[paulsherwin]

Some satellite streams are 256kb. Freeview is mostly 128-192kb for music stations. Internet streams are often 320kb AAC, which will sound almost as good as an uncompressed CD.

[Nuvistor]

In post #1 Tony mentions DAB and internet which suggests that both are problematic.

Tony,
Is it just DAB or are both affected?

[paulsherwin]

Where are the internet streams coming from? Is the tuner a combined DAB/internet radio?

[agardiner]

I too think this is a bit rate issue rather than modulation. DAB is OK on a small table radio, but push into a hi-fi or even headphones and the low quality hits you! Internet streams MAY be slightly better, but many commercial stations still use too low a bandwidth. Freeview/Sat will be an improvement. Better still FM.

[Roger Ramjet]

Sorry I my have muddied the water the by focusing on the Freeview bit rate. If the TV works does not overmodulate as an audio source (and providing it has a Freeview tuner) then why not just use that instead of the DAB Radio ?

Rog

[Craig Sawyers]

Even R3, once the benchmark of quality on FM is alas no more. It is distributed in digital format before being D-A'd before analogue transmission.

And it is now compressed, as most music content is, so that it can be listened to in the car.

But oddly internet radio is much better quality that DAB, and now alas also FM. Higher bit rate, and no, or little compression.

[its ur aerial]

RE. Radio 3, the bench mark of quality.
I thought it was just me that thought that BBC broadcast engineering had fell through the floor.
Obviously the bean counters have influence everywhere.

[Nuvistor]

Originally Posted by Craig Sawyers

Even R3, once the benchmark of quality on FM is alas no more. It is distributed in digital format before being D-A'd before analogue transmission.

It’s been in a digital format of some form from the studio to transmitter since the 1970’s.

I have no idea how much audio manipulation occurs before transmission now but that’s not same as being a digital link between studio and transmitter.

http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

[toshiba tony]

freesat it is then, due to a stroke operating it by phone is so advantageous, it was good whilst i had it.

[paulsherwin]

Originally Posted by Craig Sawyers

Even R3 ... is now compressed, as most music content is, so that it can be listened to in the car.

The odd thing is, DAB was initially designed as an uncompressed stream, with any required compression taking place in the receiver. That was back in the 90s when the engineers were still envisaging DAB as a HiFi upgrade to FM. The broadcasters were never very keen on the idea and never supported it. This is partly because they like to apply much more complex processing to the stream than simple compression, and partly because they want their stations to have a distinctive 'sound'.

The different systems do use different processing, and the amount of processing varies depending on the time of day and the programme material. This is particularly true of R3, where the drivetime programmes are quite heavily processed to support people listening in cars (though not to the extent of Classic FM), but things like evening live concerts are much more lightly processed. The R3 internet stream has little or no processing as few people will be listening in cars or on kitchen radios.

[Hybrid tellies]

Interesting discussion. I find that there are some analogue and DAB radios that cope better with the high levels of compression than others. For analogue, both AM and FM I find that some of my older radios sound better on the highly compressed sound we get especially from some of the commercial stations and BBC R1 than more modern radios.
For DAB most sound horrible on the low bit rate DAB and DAB+ stations. The only exception is my 16 year old Philips FM/DAB radio which really does try to make the best of a bad job with low bit rate DAB stations.

[simpsons]

Paulsherwin has "hit the head on the nail" in his last post.

There have been so many complaints on this forum on the audio quality of radio which reflect the critical ear of members and it might seem perverse that broadcasters "don't seem to care." But they do. The only thing is that just like Auntie BBC, the real world paints a different picture.

Members, myself included, often have well designed, well engineered and well, expensive in the day, radios. Look at the posts comparing Elac and Goodman speakers in a Hacker. Get my point.

Joe soap public have quite a different take and often don't worry about the quality or are forced to take all that is on offer. It was long ago when Which? Magazine published the audio response of a TV.

So, the broadcaster to get his programme listen to has to do something about it.

So perhaps we can say: we have DAB for kitchen radios and perhaps the car, FM for those with either old but good radios and upmarket car systems, Freeveiew for soundbars and Internet streams for the well heeled.

The EBU Viewpoint on digital radio makes interesting reading and whilst it doesn't directly address the topic, the rational behind the move to the digital platform for radio is clear, even if the sound quality to some of us is not so, ahem, clear!

Chris