I KNOW it's not diy but ...

[Andrew]

In article , Andy Hall writes

But after all that - does it sound like bubbling mud, as the FM hi-fi purists insist that it does ?.

[mike ring]

PoP wrote in news: [e-mail]:

Sorry, Pop, I meant to say radius, and did use 4000 miles in my guesstimate of a right angled triangle with the height of the satellite "adjusted" to

24000 miles so I could divide through by 4000 to get a

6+1 hypotenuse, 1, Root(7squared - 1) triangle, to give a

4000 x root48 possible height, but it must be less than that as it would require a horizontally aligned dish.

I'm glad you were awake at the back there, just testing ;-)

mike r

[Andy Hall]

I think that a lot depends on the individual, the equipment used and the content.

We have two professional sound engineering people as regular group contributors (possibly more), so in one sense, I would defer to their experience and expertise.

I've done some work in the digital video and audio transmission world, so have some appreciation of the technologies used.

One of the objectives of any form of digital audio or video recording or transmission is to squeeze as much as possible into the bandwidth or storage available while producing quality that is fit for the purpose. In order to achieve this, some fairly sophisticated compression techniques are used. This is not to be confused with the compression that AM pop radio stations use(d) so that the listener could hear the dross that they turn out even in a noisy environment or poor signal. The type of compression used in digital audio systems takes into account the behaviour of the listener's ear and brain and uses a psycho-acoustic model. Simply put, this means that information that the ear is not likely to perceive is thrown away and not transmitted. Of itself, this can save a lot of data transmission.

Here are some papers explaining the techniques.

enough bandwidth, the results can sound fine. The problem is that the broadcasters, for most of the channels are using lower data rates than are required to produce good audio quality with some types of content. Therein is the rub.

If you like to listen to classical music and to some types of jazz and have a keen ear, you will notice the effects of the compression at the low bit rates often being used, but perhaps not on a small portable set. For other content such as speech, the effects are less noticable or if they are noticable, less objectionable.

In a way it's a shame. DAB, in principle, should be able to offer good quality results and ultimately I suspect will do. However, like DVB-T (digital terrestrial TV), it is hampered by limitations of the current allocated radio spectrum. Even with today's limitations, there are still the benefits of freedom of interference as long as the signal is good (although one can argue that that can be achieved with FM).

However, the motivation for the broadcasters is to pack as much as they can into the available spectrum, first and foremost. For example, a satellite transponder will deliver one analogue TV channel but 6-8 digital channels. The problem is that the content does not in general improve.

.andy

To email, substitute .nospam with .gl

[PoP]

Credit where credit is due - it was my intelligent auto-responder ;)

PoP

Replying to the email address given by my news reader will result in your own email address being instantly added to my anti-spam database! If you really want to contact me try changing the prefix in the given email address to my newsgroup posting name.....

[The Natural Philosopher]

I thought there was compensation built in for this, i.e. set clock to time halfway between time request sent and time ack received?

[Dave Liquorice]

It's *much* more complicated than that, take a look at RFC1305.

[Andy Hall]

There is a detailed FAQ at

well as the references from the leading light on the subject, Prof. David Mills of the University of Delaware.

email, substitute .nospam with .gl

[Mary Fisher]

I've seen and hear bubbling mud in Iceland and no, the DAB reception's nothing like that. Perhaps they haven't heard the real thing.

I have the increasing hearing problem of the 'more mature' person. That means that I can't always hear some speech, it sometimes sounds muffled. Since I listen to Radio 4 almost exclusively (we don't have a telly) I need to be able to hear speech well to have the full benefit. VHF is better than Long Wave but the quality of some voices still causes me problems.

The DAB receiver - a personal 'sports' one which I can slip under my pillow - fits the bill perfectly. It has half a dozen tone qualities, I admit to hardly being able to differentiate between them but a son says the difference is astonishing.What I do know is that I've been able to hear very well since I got it - on Christmas Day so it's not been a fair trial.

I have heard music on the receiver as well but possibly not the sort of music the FM hi-fi buffs prefer. I certainly can't bear the heavy bass noise. If I'd wanted perfect music reception, even for my beloved Bach, Britten and Beethoven, I'd have bought a Bose before now. It seems to me that some purists are very quick to damn the new and know all about the technology. Their opinions are meaningless to me. The best musical experiences are live anyway and they're never perfect.

Mary

[Mary Fisher]

That's interesting.

I've found an improvement in speech quality from the DAB set. Mind you, all our other equipment is old - not quite valve driven but past its best!

Thanks, andy, you've confirmed my experiences technically!

[Andy Hall]

Not that it's directly relevant to you since you are without a Devil's Window, but digital video uses similar concepts to remove information that the eye doesn't notice.

Funnily enough, there are hi-fi buffs who will pay good money for valve driven equipment (new designs) because they feel that it sounds better. The same goes for good quality vinyl records. Notwithstanding the pops and background noise, they are said by some to sound less clinical than CDs.

.andy

To email, substitute .nospam with .gl

[Andy Hall]

That can be for a variety of reasons, including the individual who is speaking, how they sit relative to microphone, the type of microphone used, the accoustics of the room, etc.; and that's before it goes through the transmission system.

There is a deterioration in high frequency hearing with age, but if you can hear voices in the room OK and the radio sounds muffled, it isn't you.

A lady after my own heart. I even listen to it on the internet (or sometimes the World Service) when I'm travelling. VHF should certainly be better than long wave. The frequency range of the latter is not very good at all, then with compression to overcome the background noise, it does sound very odd.

You may find that because it is a small set, its low frequency response is probably not as great as a larger system. This will probably help you a bit because it will tend to take out some of the low end stuff that may be making speech sound muffled sometimes.

I know what you mean but would probably add Sibelius, Brahms and Vaughan--Williams to your list.

True. At the end of the day, if it does the job that people want then they will buy it.

Also true, but I have to say that I shall long remember attending concert of Sibelius and other Nordic composers at the Finlandia Hall in Helsinki a few years back. The atmosphere and the performance of Symphony No 2. by Jukka-Pekka Saraste and the Finnish Radio Symphony Orchestra was quite amazing.

.andy

To email, substitute .nospam with .gl

[mike ring]

That's interesting - do Bose receivers really work. The folded horn design is good, but they seem to be too small for the job of first class reproduction.

After years of going after hifi, I've now given it up, as ISTM the higher the fi the more I heard deficiencies rather than music. Even in digital it's very often possible to hear the digits shuffling, and you CAN'T not notice it!

Andy's points about psychacoustics are well made; it is interesting to consider how much pleasure you can get from a manky medium wave tranny in an old banger rattling along the road.

An awful lot of your perception is memory cued by the sounds emitted, and you can and do for example add an octave of bass that the receiver simply cannot produce.

I find in my old age I get a lot more pleasure from grotty little receivers than when I had big hifis (I only recently gave away my Radford Auditoriums, the were a bit de trop for my Technics music centre - with dolby B to liven up the telly!)

mike r

[The Natural Philosopher]

Well. Thats right, they are. Full of dirt cracks pops, subtle distortions and intermodulation products. People like to listen not to the original reciording, but the sound of their imperfect kit.

I did a blind test with some amp designs once. The HiFi buff selected the design with the highest crossover distortion becuase to his ears it sounded like (and figures bore this out) his favorite Revox amplifier.

Notwithstanding the fact that the class A design alongside it was infinitely less 'edgy'; He missed the edginess.

HiFi buffs CAN tell the difference, they just don't necessarily know what is in fact a cleaner and more accurate sound. Or indeed prefer such.

[The Natural Philosopher]

Not really.

They are.

Mmm. Its often other things like the compression and Dolby shit put on the original recordings. Dolby is probably the worst invention ever in teh history of Hi Fi.

Indeed. Most records cut on the 50's and '60's had massive amounts of bass and upper mid boost, to make them sound acceptable on a 5" paper coned loudspeaker in a cardboard box, attached to a receiver that could barely manage 5khz bandwidth.

Frankly te best I have heard has been eithjer in studios with enormous monitors, or indeed teh tiome I was working with a loudspeaker company, and we managed to crack teh ceiling playing heavy reggae through a few kilowatts of 15" bass units and a selection of JBL chiense copey mid range horns and tweeters. Its about the only rig I have ever heard that could actually produce substantial energy in the 40-80hz region.

Best commercially available speakers IMHO are the Spendors. But its a few grand a pair these days I believe.

Folded horn and transmissin line speakers don't cut the mustard on bass guitars, but are OK for organ type bass. The pgase shift muddies up teh thumping attack on a bass guitar.

Best is a pair of floppy 15" units with ultra compliant surrounds, ultra stiff cones and very long voice coils stuck on a 1" thick baffle mounted in an old fireplace stuffed with rockwool, using the chimney as a baffle....For mid range nothing beats metal horns with serious compression drivers, tho they get big, and metal bullet tweeters (horns again). That was essentially the best high volume rig I ever heard.

[Capitol]

Its about the only rig I have ever heard that

Try Tannoy circa 1980

Regards Capitol

[The Natural Philosopher]

Yup. Sadly no longer...

[geoff]

In message , Mary Fisher writes

Well, distant stars are better. There is an ongoing problem atm because the earth is slowing down and getting out of sync with the atomic time standard.

[geoff]

In message , Harvey Van Sickle writes

Frankfurt -I presume that it is internally switchable to put the display an hour backwards.

The guts are probably made by Junghans who were one of the first companies to market reasonably priced radio sync'd clocks

I have a clock which is sync'd to Frankfurt and gives european time, no problem getting the signal, but it does take a bit of thought when setting the alarm when pissed

[Niall]

I played some old cassettes the other day. I had forgotten just how wonderful it was when I was able to chuck analogue media. The absence of hiss etc makes any possible encoding deficiencies irrelevant. Even CDs made from analogue masters have me going "why is this so noisy?" I like loads of HF as well, so could never live with Dolby.

[Niall]

Domestic sound will always be a compromise bass wise, unless you live in a huge house in the middle of nowhere. I own a pair of JBL clone

15" scoop bins which rock, but are in no way suitable for domestic use. When used in anger, a female member of the audience seated near the front complained that "it was like sitting on a vibrator". The person she complained to replied "We charge extra for that."

I have a set of drawings for a 2 x 15" TCB enclosure. One of these days...