Quality of FM reception

I am an avid FM radio listener, and currently disappointed by what the BBC puts out compared with what I experienced many years ago.


One major point other than the quality of speech from the BBC, is the overall technical quality, so to the point.


Does anyone think that they can hear, when their reception conditions are good, either a studio change or an Optimod change, or even more crucially, the difference of quality on recordings being played?


This is a hell of an obstacle course for a good home system to get through and 'see' differences up-chain I realise, but someone somewhere across the globe maybe able to do so.


As an indicator of the difficulty, Alan Shaw of Harbeth has stated that typically FM distortion can peak up to 10%.
 

U230421

Disabled Account
2017-02-07 1:54 pm
From the other side of the channel, same is on the continent. (For non-eu's, compare with local situation.) In our contemporain times, we may not expect the same conditions and results, being it fm-radio reception or what. It's not 'hot', nor important anymore. Who cares quality of speech, a story to enlighten beyond the cliff-hanger. It's only now, period.
Recording or live performances are hardly to distingish; just imagine current equipment used and people involved: simple straightforward digital and operated by one person only. We've got to shift our perspective from broadcast to narrow cast, no matter the preference (and consequence). The state dictates the rules, the BBC will be axed soon by the Johnson administration in their and not the peoples interest. The monotone concert of the orwellian future. 10% distortion? Lucky you but who cares?
I recently picked up a technics ST8080 tuner (dail on the bottom, devine design). Enjoying our local transmissions here with fairly good reception. Until some moment in the unknown future, alas.
 

jaddie

Member
2011-04-01 12:06 am
Does anyone think that they can hear, when their reception conditions are good, either a studio change
That would depend on some rather specific characteristics of the studios. Generally, probably not.
or an Optimod change,
An Optimod is far to complex a device to answer this simply. It depends entirely on what changed and by how much.
or even more crucially, the difference of quality on recordings being played?
Quality difference between recordings are again varied and quite vague. Generally, if the on-air processing is not too aggressive (that's the Optimod settings again), you should be able to detect quality difference on air that would be clearly audible if you had the recordings in hand. Aggressive processing might make the differences more obvious or less obvious depending on what those specific differences are.
This is a hell of an obstacle course for a good home system to get through and 'see' differences up-chain I realise, but someone somewhere across the globe maybe able to do so.
My impression is that the general quality of BBC transmissions should be fairly high, especially relative to typical major-market FM stations in the USA.
As an indicator of the difficulty, Alan Shaw of Harbeth has stated that typically FM distortion can peak up to 10%.
Distortion audibility is a function of several conditions. Distortion can be inaudible if the time duration of a distortion condition is short enough. The longer a signal is distorted, the lower the threshold of distortion audibility. Also, certain types of distortion are more easily masked by other components in the signal. Music masks even order distortion products quite well, odd order harmonic distortion less well (but still masked), depending on the degree of distortion and the spectrum of the music involved.

However, a distortion figure is typically a measure of the distortion of a steady state sine wave at a particular level. Distortion in the FM chain should not hit 10% at any frequency up to 100% modulation, but processing also may not permit 100% modulation by certain sine wave frequencies. The whole thing is quite dynamic. However, it is never correct to state a distortion figure alone without also including a frequency and a level. FM at 10% is a meaningless figure, and very misleading as to the audibility of the distortion.

FM audio processing does include a form of clipping, which is a valid form of modulation control. However, clipping in a processor does not necessarily mean audible distortion, though any processor can certainly be set in such a way as to present a highly distorted signal. Processor settings are a matter of subjective judgement based on the intent of the signal. A classical music program should not be highly processed, and would contain very little clipping. A loud contemporary recording may be heavily processed and may contain quite a bit of clipping, but that doesn't necessarily mean its audible.

In the classic FM processor clipping occurs mostly at high frequencies, and after pre-emphasis. This is done to control peak modulation. When received, de-emphasis is applied, which drastically reduces the resulting harmonics produced by the clipper. In a modern FM processor (such as an Optimod) clipping is done using "smart clippers", such that clipping is carefully controlled as to the amount and duration. An Optimod also has a method of reducing distortion caused by clipping, further controlling negative audible effects.

But these are just some of the variables available in an FM processor that make the statement of "10%" irrelevant.
 
From the other side of the channel, same is on the continent. (For non-eu's, compare with local situation.) In our contemporain times, we may not expect the same conditions and results, being it fm-radio reception or what. It's not 'hot', nor important anymore. Who cares quality of speech, a story to enlighten beyond the cliff-hanger. It's only now, period.
Recording or live performances are hardly to distingish; just imagine current equipment used and people involved: simple straightforward digital and operated by one person only. We've got to shift our perspective from broadcast to narrow cast, no matter the preference (and consequence). The state dictates the rules, the BBC will be axed soon by the Johnson administration in their and not the peoples interest. The monotone concert of the orwellian future. 10% distortion? Lucky you but who cares?
I recently picked up a technics ST8080 tuner (dail on the bottom, devine design). Enjoying our local transmissions here with fairly good reception. Until some moment in the unknown future, alas.

I agree that FM's importance has diminished, and due to multi media IMO.

Quality of speech here in the UK has deteriorated both in the population and very noticeably from the BBC. They used to employ "announcers", specially trained in clear enunciation.

The state has always had an influence, and arguably the BBC gained its prominence from the 2nd WW.

I tend to agree that I should not have to pay, by law, for the BBC, given that IMO its services are now generally of such low quality, seemingly for a mass dumbed down culture. Reith would be turning in his grave.
Orwellian culture? We have here locally an Armageddon Group, growing in numbers.
 
Thank you for your comprehensive response jaddie.

My point was however, if we use the analogy of sheets of glass in series to represent the complete audio chain in listening to FM; can we now with our very high resolution systems at home, (two or three of the 'sheets'), detect and determine changes coming from the studios given good reception conditions?

On my last attempt at speaker design I think I could verify that certain studios or Optimod settings were being used, so I ask, can anyone else?
On CH4 TV I could hear a noise modulation form their lavalier mics.

I notice that on Sundays, "Sounds of the 70s" is generally of a better quality than many other programmes.

Of course that material is recorded form a zeitgeist I am familiar with, and techniques surely are prone to cultural changes, as is normal speech in the population, and this must be a factor.

Much modern pop, since Mariah Carey, involves a very different mic technique and singing style, and this may well serve to obscure quality differences in sound.
A clear exception to this is IMO "Senorita".

Limiting has been used to protect transmitters for a long time.
 

jaddie

Member
2011-04-01 12:06 am
Thank you for your comprehensive response jaddie.

My point was however, if we use the analogy of sheets of glass in series to represent the complete audio chain in listening to FM; can we now with our very high resolution systems at home, (two or three of the 'sheets'), detect and determine changes coming from the studios given good reception conditions?
Again, it depends on what those changes are. I do not believe the average current systems are significantly better in ability to detect subtle changes in audio quality. Reception quality has always been the biggest limiting factor.
On my last attempt at speaker design I think I could verify that certain studios or Optimod settings were being used, so I ask, can anyone else?
If you heard it, then someone else could have.
On CH4 TV I could hear a noise modulation form their lavalier mics.
TV is one area where today's systems are radically better than a few decades previous. The 4" TV speaker is less prominent as home AV systems involve separate speakers and receivers. The ability to detect anomalies has certainly gone up in that area. But it's not always an improvement either. My next project is to install a means to conveniently shut off my sub woofers, since many TV audio mixes were apparently done without subs to monitor LFE content, and contain obnoxious levels of LFE noise. It's amazing that in an era where the expense of monitoring low frequency content has never been lower, the formerly general practice of using a 100Hz low cut filter on all mics has nearly vanished. At least, that's what I'm hearing in US produced programs.
I notice that on Sundays, "Sounds of the 70s" is generally of a better quality than many other programmes.

Of course that material is recorded form a zeitgeist I am familiar with, and techniques surely are prone to cultural changes, as is normal speech in the population, and this must be a factor.

Much modern pop, since Mariah Carey, involves a very different mic technique and singing style, and this may well serve to obscure quality differences in sound.
A clear exception to this is IMO "Senorita".
Modern music is highly processed before any radio broadcaster gets his hands on it. There has been plenty written about the loudness war. It's not just mic technique, that's actually not been changed a lot, but the signal processing applied to tracks and mixes is fear inspiring.
Limiting has been used to protect transmitters for a long time.
Yes, but now not it's not just limiting, it's multi-band compression, multi-band limiting, peak limiting, smart clipping, final clipping....and all in the digital realm. All of that is now considered standard. A single-band limiter designed for FM broadcast is a rare bird now.
 

billshurv

Member
Paid Member
2014-03-01 11:53 pm
Does anyone think that they can hear, when their reception conditions are good, either a studio change or an Optimod change, or even more crucially, the difference of quality on recordings being played?


I'll be honest, I gave up on BBC FM other than in the car as soon as they started a 320kb/s stream. I used to follow the annual arguments in the 'radio' column of hifinews in the 80s and early 90s on how much compression would be added to proms concerts. BBC have to allow for people in the car, esp around drive time and so I cannot blame them, but around 1995 I got a TV with NICAM and compared last night of the proms. After that I gave up with FM at home except in the kitchen


The Optimod is a very clever bit of kit, but used wrongly can squash the music flat.
 
Again, it depends on what those changes are. I do not believe the average current systems are significantly better in ability to detect subtle changes in audio quality. Reception quality has always been the biggest limiting factor.
If you heard it, then someone else could have.
TV is one area where today's systems are radically better than a few decades previous. The 4" TV speaker is less prominent as home AV systems involve separate speakers and receivers. The ability to detect anomalies has certainly gone up in that area. But it's not always an improvement either. My next project is to install a means to conveniently shut off my sub woofers, since many TV audio mixes were apparently done without subs to monitor LFE content, and contain obnoxious levels of LFE noise. It's amazing that in an era where the expense of monitoring low frequency content has never been lower, the formerly general practice of using a 100Hz low cut filter on all mics has nearly vanished. At least, that's what I'm hearing in US produced programs.
Modern music is highly processed before any radio broadcaster gets his hands on it. There has been plenty written about the loudness war. It's not just mic technique, that's actually not been changed a lot, but the signal processing applied to tracks and mixes is fear inspiring.

Yes, but now not it's not just limiting, it's multi-band compression, multi-band limiting, peak limiting, smart clipping, final clipping....and all in the digital realm. All of that is now considered standard. A single-band limiter designed for FM broadcast is a rare bird now.

Of course it depends on what the changes are; I'm almost pleading with all, Can you hear anything going on which is from those two sources through your system?

Maybe they could hear it too, but as the phenomenon is reduced in magnitude towards zero, we become increasingly subjective, and even create internal events. (sensory deprivation).

Even the best modern TV speakers surely will not compare with my Hi-Fi ones.
I agree about the bass, and even on films where to me it is a distraction from the events, and sounds ridiculous.

We cannot know unless currently working in broadcasting just what is going on I suppose.
 

billshurv

Member
Paid Member
2014-03-01 11:53 pm
No I am saying that BBC have HD streams available at 320kb (ok not really HD but a lot better than FM). FM radio has been over digital links for 30 odd years now.


EDIT: As of 2009 (or a bit before) the links to the transmitters are NICAM stereo. Now how 15khz filters 676kb/s NICAM compares to 320Kb/s AAC I don't know but NICAM is an old standard


@Davidsrsb: Thank you for the clarification (we X-posted as I was trying to check my memory), In that case it matches what I had thought, which is 14 bit companded to 10 bits@32kHz
 
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Thank you for all the replies giving insights.

However my initial point has not been answered.

If we use the series of glass sheets analogy, also used by Toole in his lectures, has anyone got their systems to be so high resolution that they can clearly hear what is going on at source, ie., in the studios and from the Optimod.

Are your 'sheets of glass' so 'clean' that you can 'see' the 'dirt' on preceding ones?

Of course the real limiting factor is reception quality.
 

jaddie

Member
2011-04-01 12:06 am
This:
Of course the real limiting factor is reception quality.
negates most of this:
If we use the series of glass sheets analogy, also used by Toole in his lectures, has anyone got their systems to be so high resolution that they can clearly hear what is going on at source, ie., in the studios and from the Optimod.

Are your 'sheets of glass' so 'clean' that you can 'see' the 'dirt' on preceding ones?
Because no matter how clean your system glass is, all of the other panes are dirtier, occluding each other.

The first pane in the series, the studio, would be the cleanest. It would be on the level of a listener's excellent system, and much better than the average listener's system.

The amount of "dirt" in the next pane, the processing chain, is unknown, and can be anything from fully transparent to nearly opaque depending on choices made. So you may be able to see that dirt or not depending on how filthy it is.

The next pane is reception. Again, variable, and has a lot of dirt on it. There is no way to know if that pane is dirtier or cleaner than the proceeding one, the processing, because you 1) don't know what the processing chain is doing and 2) may not have the best reception. But the two are also entirely different kinds of dirt, so one may or may not occlude the other, it's completely subject to individual conditions at both ends.

The listener's system, the final pane, may well be fairly spotless. That doesn't mean the specific dirt on the proceeding panes are always detectable, though, because we don't know what specific kind of dirt there is to detect and what other dirt is involved on what panes.

Increasing the clarity of the cleanest glass (your system) won't reveal any more details of the dirt. And what would be the point anyway? Even the most basic, but decent, FM receiver has the ability to be a cleaner piece of glass than its reception conditions allow, and possibly the transmission chain allows.

Seeing the individual grains of dirt of any one layer will not improve the listening experience. For example, one of the most common FM listening environments is the car radio. So common is it that engineers make qualitative judgments of their stations processor settings by listening in the car driving down the road in traffic. And surprisingly, that's a very revealing bit of reception! Many processing artifacts are most audible at low levels on medium quality systems. Can't tell you how many times I've done exactly this. And today you can tweak the processing while in the car from your smart phone. Pulling over and stopping first, of course. There are even reception problems that will be audible in mobile situations that won't be in a high-end fixed home receiver.

There is no single answer to your question.
 
I suppose what I really wanted to know was, if we use the glass analogy and start at the left from our homes, we have;

I/C to us; Aerial, FM tuner, Preamp, Poweramp, speakers, and preceding this, and, O/G, transmitter with limiters, probably numerous links and various formats to get the signals from the studios to the transmitters, Optimod usage and settings quality, studio desk quality, studio source quality, and recorded source quality being used in the studio.

Given the number of links in the chain, I suppose that my hope of hearing the 'signature' of the studio + Opimod is rather small, but I think I can.
 
I recently picked up a technics ST8080 tuner (dail on the bottom, devine design). Enjoying our local transmissions here with fairly good reception. Until some moment in the unknown future, alas.
If you haven't already, the 4558 in the output stage and the electrolytic coupling caps either side of it can usefully be replaced with better items. I put in polyprops and an OPA2134 and it made quite an improvement.

Back on topic, BBC R3 is a prime example of source material first. With good recorded live performances it can be very satisfying. When they let the work experience types loose on the variable level during a live relay however...
 

jaddie

Member
2011-04-01 12:06 am
I suppose what I really wanted to know was, if we use the glass analogy and start at the left from our homes, we have;

I/C to us; Aerial, FM tuner, Preamp, Poweramp, speakers, and preceding this, and, O/G, transmitter with limiters, probably numerous links and various formats to get the signals from the studios to the transmitters, Optimod usage and settings quality, studio desk quality, studio source quality, and recorded source quality being used in the studio.

Given the number of links in the chain, I suppose that my hope of hearing the 'signature' of the studio + Opimod is rather small, but I think I can.
Perhaps you should re-think the glass analogy.

I don't know exactly what you expect a "signature" is. If you change mics in a studio from an LDC to a cardioid dynamic, it's pretty likely you'll hear that all the way to the receiver regardless of anything else other than unlistenable reception. Is that a signature, or a purposeful choice of a tool? I don't know.

If you adjust one control on an Optimod...just one control, and not very much, I promise you, it can be heard at the receiver.

Neither example requires anything exotic at the receive end. Just decent reception, reasonable quieting, and modestly accurate speakers. Nothing high-end needed.

Is that what you mean?

But, flipping that around, you might also swap mics, or tweak the processor and not hear the result regardless of the quality of reception or system. It all depends on what is changed, how, and how much.

That's why there's no single answer to your question.
 

rdf

Member
2004-06-21 8:04 am
big smoke
..has anyone got their systems to be so high resolution that they can clearly hear what is going on at source, ie., in the studios and from the Optimod...

In general doesn't take much resolution to hear the difference between processor presets in an A/B. In North American markets significantly different microphones are often used in the 'backup' studio and RT60 is losing ground to looks so studios can all sound different.
BTW, Orban processors are also losing ground to Omnia because louder.