How about recording the output from the speakers' negative terminals? Not something you'd want to listen to, but analysing this with an eye on dynamics, spectral content etc. should give an indication whether or not there were differences in the acoustic output of the speaker.
The edge of audibility
- Thread starter Steven Toy
- Start date
- Status
I'm assuming the differences I heard had nothing to do with in-room vibration feeding back but rather an electrical effect of adding and removing a link in the chain.
I think it's a good test, we'd not have anything at all without somewhere to start.
The external noise argument needn't come into it, common sense tells me it'll have little effect compared with in room music levels, the microphone will be dominated by the music signal given the s/n ratio and mic gain associated with a 5mm condenser microphone.
These microphones are extremely revealing BUT they need quite a bit of driving, most of the back ground noise will be the mic amp's self noise as the gain is increased.
Mic amp noise versus external background noise.
Giving it Occams razor, mic amp noise will be dominant and consistant with the levels of gain needed, with a 5mm microphone lots of gain is needed.
We only need to blank off a live microphone and measure the hiss to realise this.
It's a good test.
Mark
Edit: btw, if we used a large capsule microphone then we might have a problem as the levels of gain needed would be much lower, also a large capsule is much less accurate in response, this means that small capsule microphones needing more gain with higher self noise as a result are ideal as a bonus to this it helps rule out background noise simply because they need to be driven harder with high mic gain.
If you see what I mean.
Anyway, I think it's a good'un and a quick gain noise to background noise comparison should rule these problems out.
If a problem is seen in unusually noisy circumstances we just reduce mic gain and increase the volume of the system to dominate even more.
Mark
Would that be a problem Robert?
I think it's a good test, we'd not have anything at all without somewhere to start.
The external noise argument needn't come into it, common sense tells me it'll have little effect compared with in room music levels, the microphone will be dominated by the music signal given the s/n ratio and mic gain associated with a 5mm condenser microphone.
These microphones are extremely revealing BUT they need quite a bit of driving, most of the back ground noise will be the mic amp's self noise as the gain is increased.
Mic amp noise versus external background noise.
Giving it Occams razor, mic amp noise will be dominant and consistant with the levels of gain needed, with a 5mm microphone lots of gain is needed.
We only need to blank off a live microphone and measure the hiss to realise this.
It's a good test.
Mark
Edit: btw, if we used a large capsule microphone then we might have a problem as the levels of gain needed would be much lower, also a large capsule is much less accurate in response, this means that small capsule microphones needing more gain with higher self noise as a result are ideal as a bonus to this it helps rule out background noise simply because they need to be driven harder with high mic gain.
If you see what I mean.
Anyway, I think it's a good'un and a quick gain noise to background noise comparison should rule these problems out.
If a problem is seen in unusually noisy circumstances we just reduce mic gain and increase the volume of the system to dominate even more.
Mark
Would that be a problem Robert?
darrylfunk
Banned
thinking about this a bit more - the system to a degree has a low level feedback loop so even if you did record the output from before the power amp, if there is a difference in the signal out of the speakers it should also impose on the output of the pre as acoustic feedback....so you should then have a more accurate recording to analyse as you should have reduced the background noise problems to below audibility.
sq225917
Bit of this, bit of that
I'm sure there are ways of improving what was a first stab at it. re the mic level, I actually had it set for low sensitivity and it was set at less than half way on the record volume. This was matched to ensure minimal clipping on the recording, though `i prefer things to be as close to 0db as possible and also to keep the in room volume at Steven's typical level- thus drowning out environmental factors.
I have plenty of pre-roll from each recording from which I could cut a few seconds of just background noise if so desired.
I have plenty of pre-roll from each recording from which I could cut a few seconds of just background noise if so desired.
darrylfunk
Banned
try doing an anti phase noise reduction on the files simon.
Steven Toy
Accuphase newbie
Programme material versus means of reproduction category error.
The former should certainly not be used to determine the latter although a very good system that resolves detail while maintaining coherence can boaden musical tastes.
Of course we interpret music differently - musical taste is subjective but what we hear in recordings alters little from person to person through a given system unless their hearing is genuinely impaired.
darrylfunk
Banned
the trouble is 'detail' doesn't exist in the true musical world i.e. an acoustic performance or live jazz or classical concert that is your oft repeated category error.
plus with hi fi no one has a true idea of how the master tape actually sounds.
even things i have played on, produced or engineered are going to sound technically different for me and the others who where involved.
often i consider the biggest way forward for fidelity will be when finally designers admit that they are filtering the results for the listener and then perhaps we will get designers to actually show us the truth.
different recordings should sound more differentiated from one another as the system gets better....the reality of logic.
plus with hi fi no one has a true idea of how the master tape actually sounds.
even things i have played on, produced or engineered are going to sound technically different for me and the others who where involved.
often i consider the biggest way forward for fidelity will be when finally designers admit that they are filtering the results for the listener and then perhaps we will get designers to actually show us the truth.
different recordings should sound more differentiated from one another as the system gets better....the reality of logic.
ultrawomble
Sith Lord
I wonder why cable manufacturers don't put before and after audio samples on their websites? 
Steven Toy
Accuphase newbie
Awareness of detail is a flaw in reproduction anyway. Live music doesn't sound 'detailed'. However, the more information on the recording available the easier it is to listen to provided the performance is reproduced coherently, i.e. all the details are reassembled in the correct order.
While Simon was making the recordings I listened to how they sounded through the headphones compared to through the speakers. As revealing as those headphones are, they did not sound the same in terms of tone as the sound through the speakers they were capturing.
There is truth in this statement but it is still a cop-out.
Agreed.
While Simon was making the recordings I listened to how they sounded through the headphones compared to through the speakers. As revealing as those headphones are, they did not sound the same in terms of tone as the sound through the speakers they were capturing.
There is truth in this statement but it is still a cop-out.
Agreed.
sean99
pfm Member
If it's non-amplified (most PA systems are dire) and if you close your eyes to free up your brain to concentrate on the music then I think live music is exceptionally detailed.
Add a PA and the detail is lost, and open your eyes and your brain prioritizes visual processing, so you may not notice the detail.
Your brain is doing a lot less visual processing when it's looking at a living room wall and a couple of speakers.
darrylfunk
Banned
detail is the wrong word to describe what you are talking about.
detail does not exist in the musical language or repertoire this is a fact.
detail in the hi fi sense in most ways defines a near fault condition that implies 'highlighting' is occurring caused by a distortion. in fact in studios we have gadgets that enable that distortion.
but instruments in and of themselves do not have detail.
steven,
headphones do not emulate speakers because of 2 main differences.
1/ they are not affected by room acoustics.
2/ the left and right ears are separated from hearing the others signal by nature of the headphones operation.
detail does not exist in the musical language or repertoire this is a fact.
detail in the hi fi sense in most ways defines a near fault condition that implies 'highlighting' is occurring caused by a distortion. in fact in studios we have gadgets that enable that distortion.
but instruments in and of themselves do not have detail.
steven,
headphones do not emulate speakers because of 2 main differences.
1/ they are not affected by room acoustics.
2/ the left and right ears are separated from hearing the others signal by nature of the headphones operation.
Steven Toy
Accuphase newbie
Yes but in this instance the headphones are already reproducing the blend of two channels as they record the in-room sound via stereo microphones.
Steven Toy
Accuphase newbie
A good idea - if tedious.
Robert
Tapehead
Jason, I'm not dismissing this as insane - I'm simply saying that here we have two files and the only difference is supposed to be the mains block effect.
However it isn't the only difference. We have a non constant noise source on each file meaning that the files must be different. In other words you have completely eliminated the option of null result because it cannot occur. You guarantee a positive result. I would disagree with those who say ambient noise is not significant. It contributes significantly more to the file than many things us audiophiles consider as significant. We worry about PSU effects on for example dacs and pre amps where there is barely any measurable effect - sometimes no effect. So to dismiss something that is clearly audible and recordable is wrong.
On how we listen and compare when designing equipment, I would hope nobody does single quick A/B and says job done. There would be many, many listening sessions which changes things considerably. But you make a good point and where simple, flat, low distortion circuits are concerned, I would say that PJ Walker and Baxandall had it right. You don't actually need to listen to it because it follows rules, has a known transfer function and the result in predictable. That will have some scowling but a good case can and has been made over the years. You listen to say ' does that work, does it sound ok and have we avoided a balls-up?' Great, build them!
line out does eliminate any effect of the power amp circuit itself, but it does include speaker vibration, through feedback, and it does include modulation of the mains line by the amp as this is still drawing current and driving the speakers.
One other thing strikes me here as another variable. This test was performed with valve equipment being turned on and off (presumably as the mains connections were changed over). Make a recording, switch off valve equipment, switch on and record again - and a difference is highly likely for various reasons including the internal valve components contracting and expanding. In fact the noise from this is often easily heard as i'm sure valve users will testify. So you'd need a fairly long wait after power-up.
Of course lots of kit was switched on and off on the day - some feel this is very significant, including I think Steven. It hasn't been mentioned as a factor.
So I'd say this was a good attempt to record something and I genuinely meant what I said about Steven in particular agreeing to some attempt to capture the results. I just think as it stands the object of the test hasn't been realised.
One last thought for the day. I agree we want the amp circuit effect recorded if possible but but this is very difficult in practice.
You could take a line via the speaker terminals via an L Pad but you'd need to be driving a dummy load. With speakers connected you have back EMF and a signal going back to the amp.
A dummy load is a reasonable solution as at least you are loading the amplifier and drawing current.
Do this and make the changes in mains wiring resistance extreme enough and we should see something. It at least gives a feel for the nature of the problem, though given the lengths we evidently have to go in order to find this damned problem, I would personally file under insignificant and move on. Edge of audibility, indeed.
Steven Toy
Accuphase newbie
I think you are still clutching a straws. You are right to mention other possible variables but are still too eager to deny the most obvious conclusion.
As for insignificance, that would depend on how much you value subtlety in reproduction of recorded music and how you prioritise the various sonuc imperfections of the audio chain inherent in all systems to varying degrees. Insignificant to you maybe.
As for insignificance, that would depend on how much you value subtlety in reproduction of recorded music and how you prioritise the various sonuc imperfections of the audio chain inherent in all systems to varying degrees. Insignificant to you maybe.
sq225917
Bit of this, bit of that
The low level noise that you assume to be environmental is the fan in the pre-amp, there was no traffic noise, no passing people, no fridge or radiator hum- just the pre-amp fan.
I would have been quite happy to record just the cd player effect but it seemed sensible to record a potential mains block effect seeing as it so beloved of Steven, and disparaged by so many, myself included.
I agree that the positive result we appear to be getting begs further and more detailed investigation.
I would have been quite happy to record just the cd player effect but it seemed sensible to record a potential mains block effect seeing as it so beloved of Steven, and disparaged by so many, myself included.
I agree that the positive result we appear to be getting begs further and more detailed investigation.
- Status