Yes that is an important issue. I still have my Smith Realiser A8 and I am looking at a way to transfer the headphone-to-inner-ear transfer function that it can measure to the replay chain. One way would be to use the A8 itself as the headphone amp, which would be a natural way to equalise the headphone to listeners ears. Also has the advantage that every listener can store and use his own personal ear transfer function.
Jan
I will not pretend to even begin to understand how and why, but my experience is that faced with several amps, chances are I will like the one with a wide bandwidth better than others.
My general grievance with most (but not all) UK made amps is that they sound somehow lazy and subdued to me. This does not mean that they are unpleasant to listen to, just that they somehow seem to be lacking some gusto and speed.
On the other hand, most (but not all) Scandinavian amps somehow seem bright and lacking the "oomph!" factor to me.
Perhaps we should consider local (regional) listening cultures as well. A pointer would be to listen to some local/regional folk music, its tonal balance could perhaps offer a better understanding.
My general grievance with most (but not all) UK made amps is that they sound somehow lazy and subdued to me. This does not mean that they are unpleasant to listen to, just that they somehow seem to be lacking some gusto and speed.
On the other hand, most (but not all) Scandinavian amps somehow seem bright and lacking the "oomph!" factor to me.
Perhaps we should consider local (regional) listening cultures as well. A pointer would be to listen to some local/regional folk music, its tonal balance could perhaps offer a better understanding.
I had a friend who mostly was a friend as he had a place to stay . I don't mean that in a bad way , we were chalk and cheese . He was the last person in the world I would call an intellectual . Out of hero worship of a guy we knew he developed a liking for the study of Buddhism . As daft as Mark was he seemed to get the basic points very well . He told me this "everything is contradiction and contradiction is good " .
This is where I find myself with bandwidth . Given the choice the more the better . However as Jan pointed out FM works better than it should . CD with similar filters was not it's greatest moment .
All you can do is take each example and do the best you can . The important thing is an audio memory that says in seconds yes or no . Class AB amps warming up is where caution is required .
Funny thing . Mark interview me in his garden whilst cutting his grass . I was to say the least poked off . So I sent him up . His girlfriend sent the tape to Radio Oxford to help Mark get a job there . Upshot is they wanted me to go for an interview ( gulp ) . Henry Aubrey Fletcher from Radio Oxford taught me how to do classical music recordings . He spent a lot of time teaching me . It was a skill he picked up by being at the BBC , on local radio everyone learned these skills regardless . He demystified it to the point it made it seem simple . I looked him up recently , one of our top-draw toffs . I would never have guessed except a true gentleman .
He started with what did I find to be wrong . I said the piano sounds like it is underwater . He said that's common . He next said regardless of the mass of the building sound was getting to the microphone by two routes . He advised string to replace my stands and use the same height so as to be sure I knew where the problem came from and it's cure . Next he told me the use of string to position the microphones . The BBC used 6 and a fill in for the soloist , however where possible only 2 of the 6 used . This was a quick set up for unknown venues . Not bad for a man who took a passing interest ?
Sorry if Dyslexia got to this . Hope it stimulates ?
This is where I find myself with bandwidth . Given the choice the more the better . However as Jan pointed out FM works better than it should . CD with similar filters was not it's greatest moment .
All you can do is take each example and do the best you can . The important thing is an audio memory that says in seconds yes or no . Class AB amps warming up is where caution is required .
Funny thing . Mark interview me in his garden whilst cutting his grass . I was to say the least poked off . So I sent him up . His girlfriend sent the tape to Radio Oxford to help Mark get a job there . Upshot is they wanted me to go for an interview ( gulp ) . Henry Aubrey Fletcher from Radio Oxford taught me how to do classical music recordings . He spent a lot of time teaching me . It was a skill he picked up by being at the BBC , on local radio everyone learned these skills regardless . He demystified it to the point it made it seem simple . I looked him up recently , one of our top-draw toffs . I would never have guessed except a true gentleman .
He started with what did I find to be wrong . I said the piano sounds like it is underwater . He said that's common . He next said regardless of the mass of the building sound was getting to the microphone by two routes . He advised string to replace my stands and use the same height so as to be sure I knew where the problem came from and it's cure . Next he told me the use of string to position the microphones . The BBC used 6 and a fill in for the soloist , however where possible only 2 of the 6 used . This was a quick set up for unknown venues . Not bad for a man who took a passing interest ?
Sorry if Dyslexia got to this . Hope it stimulates ?
I built my stereo image correction device for headphones . Active buffer in class A and class A output . I still don't like headphones and that includes my Stax . The reason I now know . They are too close to me . They do not let the sound develop .
Here is an interesting thing . My speakers are as much like a pair of headphones as you can get . As I said before a 1926 recording shows space and dimensions to the point where stereo seems the best description . Doubtless the asymmetry of the room helps that illusion . To hear the ladies turning their heads is obvious and special ( whimsical ) . Looking the up recording ( cataloged Dec 18 th 1926 ) I suspect it must be a showcase for early electrical recording . I was led to believe all early electrical recordings to be awful , not so if this is one . I have been told acoustic recording had reached a state of perfection . I just feel this one must be electrical . The near soprano like skills of the girls is clearly shown ( no joke ) . As I said to my boss today on the speakers a time machine and the headphones a snapshot ( the headphone amp is for him , he dislikes headphones ) . What I think I hear is girls like they are today , the headphones don't show it . Depression and war changed that , we might be back where we should be . The 18 th century was like it from the little I know .
Here is an interesting thing . My speakers are as much like a pair of headphones as you can get . As I said before a 1926 recording shows space and dimensions to the point where stereo seems the best description . Doubtless the asymmetry of the room helps that illusion . To hear the ladies turning their heads is obvious and special ( whimsical ) . Looking the up recording ( cataloged Dec 18 th 1926 ) I suspect it must be a showcase for early electrical recording . I was led to believe all early electrical recordings to be awful , not so if this is one . I have been told acoustic recording had reached a state of perfection . I just feel this one must be electrical . The near soprano like skills of the girls is clearly shown ( no joke ) . As I said to my boss today on the speakers a time machine and the headphones a snapshot ( the headphone amp is for him , he dislikes headphones ) . What I think I hear is girls like they are today , the headphones don't show it . Depression and war changed that , we might be back where we should be . The 18 th century was like it from the little I know .
Not from where I am now.... info not with me,,,,, but maybe you can visit Sennheiser facility and get first hand how and Why they test as they do. Might make a good article as well for your product/
I have done enough accumulated tests and comparisons with artificial ears and coupler data to come to some conclusions.
I am thinking these days that you really need to measure the headphone without an artificial ear attached to it. Only a clamped to a plate with sound absorption for some headphone types which depend on a closed volume of space to work into.
As with loudspeakers.... we don't measure them at a distance in a home listening room... that wouldn't tell us what the speaker system alone is doing. The ear and its affect on the headphone's reproduction is likened to the rooms affect on the speaker measurement.
The ear has evolved to compensate for the major affects caused by the ear shape (eg. sensitivity boost etc to compensate for the dip caused by the ear canal etc.). And, because sound approaches the head from many angles, a flat free-field response gives more accurate data for listening results.
THx-RNMarsh
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Why not? When bandwidth limited signals sound better, why could full bandwidth signals not trigger misbehaviour in the gear?
Wouldnt this method give you FR errors below 200hz, how would you compensate for or calculate cavity proximity gain ...
That's possible, to be sure. Just imagine a 24/196 reader going wrong somewhere and a relatively strong signal appearing somewhere high up. I imagine quite a few widebandwidth amps would find this unsettling.
However, we need to look at actual (real) and internal wide bandwidth.
To wit, some manufacturers (e.g. Sony, Studer/reVox, etc) first make an amp a very wide bandwidth product, hitting at full power 350 kHz and above. Then, after they have stabilized them, they include an input first order filter limiting the bandwidth to 200 kHz or so. And they admit the deed by stating that your internal (i.e. without the input filter) slew rate is say 350 V/uS, while your effective (real) slew rate is say 150 V/uS.
Years ago, on one forum or another, I read from one engineer employed by Studer/reVox that 200 kHz was high enough not to cause too much phase shift at 20 kHz, but still made sure that the amp was always faster than the fastest signal that could try to get into it in real life (i.e. not purposely generated by test equipment, such as say 40 p-p at 500 kHz).
Sony prefers to lower this down to 150 kHz or so. Just as a precaution.
the usual Bode estimate correction is 5.6 degree phase shift at the 10:1 pass to pole ratio
but 5.6 degrees of phase shift isn't really the issue - because it can be mostly attributed to pure delay <800 ns in the <20 kHz band
the real audio band time/phase "distortion" is the differential group delay: from 1 kHz to 20 kHz with a 200 kHz 1st order low pass that's ~ 8 ns
for perspective calc the air path length of 8 ns ~= 2.4 um or 100 micro inches
but 5.6 degrees of phase shift isn't really the issue - because it can be mostly attributed to pure delay <800 ns in the <20 kHz band
the real audio band time/phase "distortion" is the differential group delay: from 1 kHz to 20 kHz with a 200 kHz 1st order low pass that's ~ 8 ns
for perspective calc the air path length of 8 ns ~= 2.4 um or 100 micro inches
Hmmm. Good point, thanks for the suggestion. Certainly something to consider.
I wonder whether such an effect would be measureable.
jan
Sorry for trolling a bit but I've found the classic Crosby, Stills, Nash and Young's first album to be horribly recorded. Their excellent acappella voices sound like they were recorded with the mic on the opposite side of a heavy towel.
Deja vue to me seems really pretty well recorded for 1970, but it is not very 'smooth'. All electric guitar work is heavily distorted and the voices are recorded fairly raw. But it took me a long while to get speakers that bring this out. It used to sound horrible indeed.
While not disputing what you gents are saying, one should keep things in some perspective.
Remember, The Beach Boys taped "Pet Sounds" in a motel room, on a spree. "Ha Ba Ba Ba Barbara Ann ..." was actually taped on what we'd call a poratble deck these days, and it still made it to most charts of the day. Ditto for many other groups as well. In those days, studios used to expensive and relatively rare.
While leaving much to be desired technically, it was still great music.
Remember, The Beach Boys taped "Pet Sounds" in a motel room, on a spree. "Ha Ba Ba Ba Barbara Ann ..." was actually taped on what we'd call a poratble deck these days, and it still made it to most charts of the day. Ditto for many other groups as well. In those days, studios used to expensive and relatively rare.
While leaving much to be desired technically, it was still great music.
That's right and is part of my correction .
Here is the thing . Early phones like Sennheisser HD 414 were almost a microphone in reverse . That suggests that they should decode simple recordings rather well . As microphones are added at the recording end any concept of accurate decoding is lost . Decoding is a lazy word , I think most will see the idea . If you like the second part of a lens .
We are then left with very low distortion and no crossover phase shifts and filter sounds as advantages .
Even my Stax headphones are at best boring . The sound is disjointed .
Going back to HD 414 . I don't remember them being like this . I think it was the shape of the ear pads making things slightly better . The Stax loose out because they are like cheap schools headphones in design ( I suspect that is the cause ) .
One phone I always liked was Beyer DT 990 . I think I will try to borrow some . Beyer DT 990 Studio was a special version for exactly what the name suggests . I used to keep a pair to prove to people the cheaper one better for home use . The S version had selected drive units and no HF filtering .
I bought some bottom of the range Sony ear buds . They are the weirdest things ever . Awful and wonderful in equal measure . The wonderful slightly wins the day . Something in the program material can make them sound like yoghurt pot telephones . Sometimes it vanishes completely . It has no trend I could detect . On the 1926 , 78 test they don't produce the swirl of two girls gently dancing as they sing . What they did do is separate the voices better than my expensive phones . I think that's down to the fit in the ear . The biggest mystery is sometimes the sound is like locked solid cones . It isn't fatiguing , it just sounds rubbish . Same phones decoding something different and bingo they are OK .
If I did a tick list of all things that are right with phones it should make all high end hi fi look sick . Problem is they just don't decode the material in terms of focus . Also being too close doesn't help . Ironically the better sound is when as close as possible is used . That is logical and a conclusion of sorts . I think people called it a direct pressure transducer when so ?
I listened to TV last night for one hour using phones . I think I am 70% happy . The Stax unaided 30% . That means a special headphone amp with EQ ( and direct as much modern stuff is headphone friendly ) and moderately good headphones like the cheaper Grado's sounding better than my Stax .
My advice is make it class A throughout and keep it very simple . You will be surprised how little current you will need . For capacitors I use the EPCOS bare laminated 100 V polyester types . My feeling is the are the sane end of the capacitor quality argument . The prices are so low that I suspect it is end of the line for them .
One thing Sennheiser should do is make HD 414 again . Charge like Grado do and see if the market still exists . Seeing ABBA using them should be enough for the relaunch . Nothing stopping them making HD414HD . That might be with improved drivers in the same frame .
One attempt to solve this in the past was an air tube between drivers .
A slightly disappointing outcome that makes sense to me . For what it is worth binaural recordings don't quite work . This tells me I am as far I can go on this journey .
One exception is phono stages . A piano for some reason sounds awful when a 30 kHz filter used . I supect this is because the 75 uS is already doing something important . Most use a passive 75 uS as it is the logical choice . It is useful to make it 25 to 100 uS . This is a different story to the bandwidth limiting ( very subtly and that is the thing to note ) . Many DMM are 50 uS , it was never stated . Funny thing is like tape EQ it is obvious when right . As said in my headphone piece it sounds like things came into focus more than tonal .
I don't care to say all the ins and outs of this . Just to say a big contradiction that is resolved by placing the filter in the right place . All you need do is listen and be alert to right and wrong . Passive 75 uS will always work . Active EQ is technically better if done with extreme care . Sorry to say LP's don't need this and your chances of making a mediocre thing is considerable . I have been told my phono stage sounds just like tubes ( it does ) . It measures better and is as far removed from tubes technically as it is possible to get ( no JFET's ) . The trick is it is mostly current amplifiers throughout . I suspect it is much more " studio tube like " than most modern tube designs . Many of them seems dull as their major difference over transistors . I can't stand dull . I hate harsh even more . The tube design as reference was the partner preamp to the Marantz model 9 power amp . I feel flattered as the Marantz is a correct design . Strangely mine does sound more open and bright+sweet . The Marantz had been upgraded with modern caps by it's designer , it was tested to book spec .
BTW . Transistor linearity in current mode is impressive . It is easily corrupted ( I think Early effect ) . The corruption sometimes is rather nice if wanting that . I built a tube amp with transistor current amps ( MJE 340 350 ) . They were removed at the final stage . I accepted a 50% distortion increase in doing that (1.1% THD in exponential decay at 8 watts ) . I did it to please the purists . An LM 317 worked very well as a cathode current sink . It took days to get a single transistor to beat it ( resistor used in the end ) . What this told me was how the tubes worked . In the end bootstraps replaced the active devices . Don't think I ever saw that done before ? I used 82% UL ( near triode ) . No loop feedback and per-distortion . Some told me per-distortion can not work as the tubes need to be exactly matched which will change with age . Nonsense and double nonsense . I am not prepared to say the how the why , I just say you have not done it correctly .
Pre-distortion is like a superior version of negative feedback . That is a complimentary error is used . As far as I can see only tubes can do it ( JFET's ?) . Negative feedback puts the same type of error correction in with a mild time delay and as DF 96 pointed out a number of filters in the signal path . Pre-distortion can be used with negative feedback . In fact it is rather good . Some say pre-distortion is adding artificial highlights . Nonsense , it is straightening a curve . You can not design such and amp without a spectrum analyzer .
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