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"Breaking In" AKG 701s?

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Re: "Breaking In" AKG 701s?

Postby Eric Sagmuller » Tue Jun 15, 2010 12:29 pm

David Pinnegar wrote:Hi!

If one is using an exotic driver in a horn then _all_ movement is amplified, often 0.1 watt being all that's needed to drive it for an acceptable listening volume, so the very very small differences in the mechanical properties of the foam mountings, normally irrelevant, are now amplified and become audible.

Best wishes

David P


On the other hand in a horn driver the movement of the diaphragm is only a fraction of the movement of one that is not horn coupled, for the same volume output. So changes in the suspension material would be much less, and also much less noticeable. So in the end it may work out the same.

Eric
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Re: "Breaking In" AKG 701s?

Postby Grant_Youngman » Tue Jun 15, 2010 5:55 pm

pwhodges wrote:My problem is not with the possibility that materials can change their properties as a result of movement so much as with the language used to describe the (possibly) audible effects. Audible changes should also be measurable (yes, I know how hard correlating some measurements with their audible effects is, so no need to go down that road here).

Paul


You're absolutely right. I think the real problem here has nothing to do with headphones, foam surrounds, metal fatigue, the relaxation of long-chain hydrocarbons, nano vibrations, or anything of the sort. It's the absurd language (David, I mean no offense, here) -- but really ... "less brittle"? What the blazes does that mean? Madonna can be a lot of things --- but "brittle"? Explain that to me in terms I can actually understand -- or better yet, actually hear. (And please don't tell me I just lack sophistication).

A died in the wool audiophile will describe in flowery terms what "brittle" means. But the audio-speak is akin to a secret handshake that can only be explained in the context of .. dare I say it ... membership in Skull and Bones, or Voodoo?

Maybe the rest of us appreciate a good sound without the unintelligible hysterics that accompany it's description :twisted:
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Re: "Breaking In" AKG 701s?

Postby pat17 » Wed Jun 16, 2010 3:30 am

It's funny to see how the same subjects continue year after year to generate passionate debates in the small world of audio fans... Beside breaking in loudspeakers and earphones, one also has audio and AC cables, atomic clocks to reduce jitter, loudspeakers isolation to reduce vibration and ground floor effect, etc...

I have some knowledge of all of it as I am myself an audio freak - well, I used to be, now I moved to other points of interest.

Still, if I consider as of today quite a lot of efforts an theories in that domain are a waste of energy, and in most of the time a - significant - waste of money, I still do believe in the audio breaking in. At least it costs nothing but time, and I could personally monitor on my own ESL equipment (Martin Logan for panels, Stax for earphones).

How to describe its effect? Anticipating beforehand this debate would quickly becomes passionate, I was just stating earlier it is better. But since some of you prefer to get accurate and understandable description of the gain, I would say - remember I am referring to the very specific case of ESL - sound stage widening. ESL are very well know for their biggest drawback - a very narrow sweet spot due to a highly directional sound signal. With time, sound stage gets wider, space becomes more tri-dimensional.

I'll give no scientific explanation for that - unfortunately, I am not on the technical side at all. This is just what I have monitored on my equipment , and this is very similar to what a lot of other ESL fans have witnessed as well.
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Re: "Breaking In" AKG 701s?

Postby David Pinnegar » Wed Jun 16, 2010 12:57 pm

Grant_Youngman wrote:You're absolutely right. I think the real problem here has nothing to do with headphones, foam surrounds, metal fatigue, the relaxation of long-chain hydrocarbons, nano vibrations, or anything of the sort. It's the absurd language (David, I mean no offense, here) -- but really ... "less brittle"? What the blazes does that mean?


Hi!

I'm one of those very down to earth people who sneers at venal ways to make even bigger fools of idiots with more money than sense - diamond material tweeters, for instance, and "oxygen free copper". Big jokes.

But by brittle, I mean not free and relaxed. It's a description and an explanation understood by addicts of the one particular speaker driver renowned for such an effect - you'd recognise it if you heard it and you'd only then do so when your units had actually been run in, as they sound pretty good as they are out of the box. But treated carefully for the first few days, they sound better and better. My 10 year old units sound better than my newly refurbished ones.

It's like old violins - they sound better than new ones, and new ones improve as they get older. Harps do too - in particular they need constant playing and an instrument not played for 6 months needs "playing in" until its tone comes back.

This is no audiophile freak country - it's an effect noted by musicians across the board . . . especially ones who are sonically in contact with soundboards. Even pianos get better and I prefer an 1880s instrument against a new one any day. Resonant planes have modes. The longer they resonate in a wider variety of modes, more subtle modes can come to the fore rather than merely those instantly available when they are brand new. Materials have memory and exciting higher orders of vibration will bring vibration in those modes, as flexibility increases in those modes, into availability at lower energy levels.

No doubt it's also on account of the vibration modes of the thin paper cones also. When new, simple numbers of resonant modes predominate whereas with ageing, a nearer to continuity of available vibrations opens up.

Strads were probably fairly run-of the mill violins when they were made. But for some reason because they were favoured slightly more and survived slightly better, they were appreciated more and more as their ages increased and violinists will use the terms "sweet" and "brittle" likewise in respect of old and new instruments.

I am dealing currently with one of these exotic drivers on one channel of my organ at the moment. A wire has failed at its solder joint with the lead-in wire so I have the unit apart. Some time ago, because I could not source foam spiders, I replaced the spider with a very thin rubber membrane, which is in perfect condition. But having dealt with some foam examples recently, I realise that the rubber membrane has a springiness, providing a return force similar to a new foam. But old foams are stretched so that within the confines of the pole gap field linearity, the spider allows free movement without a return force. So I can see how the process of ageing does actually affect the mechanical properties of the system and the sound will be audibly affected as a result. But it's good enough for frequency range of the channel of my organ that I'm using it with . . . However, the cone edge surround is foam and I can see that through use it has acquired concentric lines in the foam which are not present in new foam surrounds. So the effect is not only audible but visible too.

Best wishes

David P
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Re: "Breaking In" AKG 701s?

Postby David Pinnegar » Wed Jun 16, 2010 6:16 pm

Hi!

Here are concentric rings in foam speaker surrounds that have developed in use. Homogeneity of the structure has broken down. These are lines of increased flexibility.

Sorry about the colour balance . . .
Image

Best wishes

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Re: "Breaking In" AKG 701s?

Postby pwhodges » Thu Jun 17, 2010 3:02 am

The trouble with changes of this sort is that they are not entirely predictable or controllable - and of course there is no inherent reason why they should lead to improvement at all (in the end, when foam breaks down, for instance, they definitely don't). It is good engineering practice to find materials which are stable in the usage being made of them (as far as is possible in combination with other properties), and to operate them sufficiently within their limits that they are not driven into permanent change. While this may ultimately be an unattainable ideal, I would still regard the need for any breaking in outside the production process as a design flaw.

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Re: "Breaking In" AKG 701s?

Postby David Pinnegar » Thu Jun 17, 2010 9:52 am

pwhodges wrote:The trouble with changes of this sort is that they are not entirely predictable or controllable - and of course there is no inherent reason why they should lead to improvement at all (in the end, when foam breaks down, for instance, they definitely don't). It is good engineering practice to find materials which are stable in the usage being made of them (as far as is possible in combination with other properties), and to operate them sufficiently within their limits that they are not driven into permanent change. While this may ultimately be an unattainable ideal, I would still regard the need for any breaking in outside the production process as a design flaw.


:-) !!!

Dear Paul

Well yes of course. From an engineering point of view I agree. But do we therefore say that Stradivarius violins and harps have to be the product of design flaws? Thank goodness for design flaws!

The bottom line, however, in relation to these speaker drivers is that the cones become loosely held in the right place, assisted sometime by magnetic suspension but essentially, the very unidirectionally flexible foam enables very free movement to happen and this freedom is transmitted to the air. It results in extreme sensitivity, reproduction of extreme detail of sound. Of course, eventually the foam does rot, a problem in common with the Tannoy HPDs which also need refoaming from time to time. One just has to take this "maintenance" as the price for extreme reproduction against which in the right cabinets, nothing else compares.

For some time I have been investigating drive units of cheaper and more robust construction . . . and use many of them on my instrument, often for particular purposes, but finding any substitute to near freely suspended cones in an extreme magnetic flux is a tall order.

A pop group, "The Shortwave Set" came here to use the house for recording their album to be released in the Autumn. They brought state of the art studio monitors, the defects of which were very audible after hearing speakers designed according to good physics. They recorded a drum set in various acoustics, Led Zep style, and it was patently apparent that one cannot get a cymbal sounding like a cymbal out of a tweeter just an inch or so in diameter. And then there was the separation of the singer's voice from gutteral consonants represented by a thump from the woofer and a click from the tweeter. Such speakers cannot try to do justice to sound in real terms: they can reproduce the frequencies of music but cannot convey a performance.

So, in view of musical instruments like harps and violins needing playing in order to be "broken in" sound reproducers which have the reputation of needing such "breaking in" are more likely to be capable of conveying a performance as an instrument of music rather than other devices designed merely as instruments of engineering . . .

Best wishes

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Re: "Breaking In" AKG 701s?

Postby pwhodges » Thu Jun 17, 2010 10:21 am

David Pinnegar wrote:sound reproducers which have the reputation of needing such "breaking in" are more likely to be capable of conveying a performance as an instrument of music rather than other devices designed merely as instruments of engineering . . .

"Mere" engineering? I may agree that you can compromise stability against accuracy of reproduction, but this remains, in my view, an engineering compromise which can be measured and controlled; and using language that suggests that transducers are musical instruments just confuses the issue - and brings the possibility of misunderstanding or argument for the wrong reasons.

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Re: "Breaking In" AKG 701s?

Postby David Pinnegar » Thu Jun 17, 2010 12:43 pm

pwhodges wrote:
David Pinnegar wrote:sound reproducers which have the reputation of needing such "breaking in" are more likely to be capable of conveying a performance as an instrument of music rather than other devices designed merely as instruments of engineering . . .

"Mere" engineering? I may agree that you can compromise stability against accuracy of reproduction, but this remains, in my view, an engineering compromise which can be measured and controlled; and using language that suggests that transducers are musical instruments just confuses the issue - and brings the possibility of misunderstanding or argument for the wrong reasons.


:-)

Dear Paul

I think that this is possibly the point at which organs find the point where engineering and art meet. Whilst certain things can be engineered, music goes beyond what can be predicted. If products are made, such as Stradivarius violins, harps and certain forms of electromagnetomechanical sound transducers, which are good and known to improve with use, isn't that a bonus? In fact a few pianos and harpsichords have been made with metal soundboards in order to attempt to make their behaviour more predictable. But there is a problem - they don't do what musicians ask them to do in the course of making music.

This is the classic definitive diagonality between an engineer and a physicist. An engineer aims to use physics to solve problems in a controllable and predictable way. The engineer requires to suppress unpredictability, to control nature to man's behest. BP have found that Nature does not always behave in that way. In contrast a physicist seeks unpredictable phenonema, to explore rather than to suppress nature, to see what formerly insoluble problems such unpredictability will solve. What can we emulate about a Stradivarius which will make something else sound better in the course of time?

The original question related to whether any improvement could occur in "running in" such a mechanical transducer. The photograph above shows the effects of use and both experience and contemplation of the process shows that movement in a membrane partially fragmented in such a way is freer. The answer to the question is therefore "yes", whether as an engineer or a physicist we like it or not.

Best wishes

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Re: "Breaking In" AKG 701s?

Postby gecko » Sun Jun 20, 2010 9:13 pm

David P, in the course of a long and highly interesting diatribe on break-in periods, wrote:
Strads were probably fairly run-of the mill violins when they were made.

If I recall correctly, they were always thought good but perhaps too loud and coarse, and not quite in the category of instruments such as those by, say, Jacob Stainer. Tastes changed with the increasing size of orchestras and concert halls - so Stainer's instruments typically survived unaltered so they could be studied by modern makers interested in historical instruments, whereas all the surviving Stradaveris have been rebuilt numerous times and we're not even sure of some of the details of the originals.

I don't quite understand Paul's point that a breaking-in period means ipso facto an engineering defect. Materials change when they are used; there's no way around that fact, and sometimes the optimum material requires a bit of use before it settles into a stable state. For an extreme case, consider Javanese gamelan instruments, which are (mostly) instruments usually made of bronze. These can require several decades of daily playing before they settle down to a stable tuning (mostly due to work hardening, I would guess). It's possible to engineer instruments that don't require such a long break-in period, for example by making them out of brass instead of bronze, but they have a very inferior tone.

Immediate gratification is nice, but all materials represents compromises of some sort, and there are obviously other factors that have to be considered.
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Re: "Breaking In" AKG 701s?

Postby Gedakt » Mon Jun 21, 2010 12:43 am

Hi David,

Forgive me if I say you place too much emphasis on the “Stradivarius analogy”. The bottom line is that a Strad violin is not a pair of AKG 701’s - so your analogy is hardly a valid argument in favour of breaking-in the latter headphones. That aside, I’m not sure that Strads HAVE improved with age anyway! Who can say what they sounded like several hundred years ago? Sure they apparently have outstanding tonal qualities about which musicians and critical listeners seem to agree but these may well have been the original qualities of these instruments rather than the result of extended usage and age.

As far as the breaking-in of headphones question is concerned, I do not believe it is necessarily due to the suspension becoming “freer” – if, indeed, breaking-in does improve the sound. Steinway, together with many other piano manufacturers, coat their soundboards with an extremely hard-setting lacquer which is hardly likely to cause them to become “freer”. The theory here is that this hard surface dissipates less energy as heat than a “lossy” coating, reflecting more energy as sound and thereby enabling a greater “sustain”. But I’m falling into the musical instrument analogy trap myself and must admit it has nothing to do with breaking-in headphones.

As there appears to be no way at present to objectively measure sound “quality”, which is a subjective characteristic anyway, we can only rely on the evaluation of those with very sensitive ears together with exceptional auditory memories to say whether AKG 701 headphones do sound better (to them!) after a few hundred hours than they did when new.

I do not see how analogies with musical instruments can help with the discussion one way or the other.

Kind regards,

Max
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Re: "Breaking In" AKG 701s?

Postby dralanrobinson » Mon Jun 21, 2010 3:49 am

Yep,

This is highly evocative and exciting,to some. I do wonder though, since it is an established fact that the frequency response of the human ear diminishes with age ; for instance babies can hear high frequencies much better,as can dogs. We dont have a laboratory tested sound engineer. There is no scientific control. Whilst I agree macro effects are distinguishable, I have doubts about the perceptions of such experts. The fact that measurements show differences doesnt necessarily translate into the hearing experience. Thats why different people prefer different organs in different settings. There really is lttle rhyme or reason. One mans meat.......?

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Re: "Breaking In" AKG 701s?

Postby David Pinnegar » Mon Jun 21, 2010 6:06 am

Gedakt wrote:The bottom line is that a Strad violin is not a pair of AKG 701’s - so your analogy is hardly a valid argument in favour of breaking-in the latter headphones. . . . Sure they apparently have outstanding tonal qualities about which musicians and critical listeners seem to agree but these may well have been the original qualities of these instruments rather than the result of extended usage and age.


Hi!

Firstly I should comment that I have no direct knowledge of these particular headphones. All that I am saying is that there is a very established line of thought in similar directions with a particular construction of loudspeaker drive unit with which I have had experience over many years, both in listening, and more recently in repairing, and found significant physical evidence suggesting justification for what is otherwise, as you say, a subjective and potentially arguable phenonomen. But I have photographed on this thread the visible evidence . . .

For thirty years I have been promoting concerts by interesting performers, from young people to top players in their spheres. The harpist David Watkins, both a player and writer of textbooks on harp technique, can tell the difference between a harp in constant use and one which has not been played for 6 months. We might not be able to hear it, but with his fingers in contact with the strings, he feels directly how the instrument responds.

No doubt many of us have felt the how car steering responde when it has run out of steering fluid - and certainly drivers of Unimogs with portal axles, having extra gearboxes in the hub of each wheel are aware of having to drive takes 10 miles of driving to free up the system if the vehicle has not been run in a while. Of course, these effects are temporary whilst the "running in" issue refers to permanent changes. On eBay at the moment, there's a pair of such units specifically marketed as a run-in pair 2 years old with 800 hours on the clock and for once within the urban myths of hi-fi, because a visible change is apparent in the materials, it's not a matter of auditory self deception. Some people coat the cones with a varnish, like soundboards, and others warn you not to do it as it preserves part of the "brittle" sound, suggesting that the phenonomen may have something to do with the fragile paper and its breakup into multiple vibration modes. Evidence for this is that some report the sound to be "sweeter" in damp weather.

So if the AKG headphones are constructed with foam mountings, or thin paper cones, the phenonomen is possible.

Alan's is a very interesting point. One wonders how many of us have liked mellow sounding instruments when younger but now seek the thrill of enhanced upper frequencies when older? For this reason we might like different organs, none being "right", and when recorded and replayed without the reference instrument, no doubt we will have a subjective view on how we like to present it in terms of equipment. Perceptions in the change of the course of time can only be objective in the direct comparison with the original instrument side by side with the reproduction. Beyond that, as you say, all is subjective.

Best wishes

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Re: "Breaking In" AKG 701s?

Postby gingercat » Mon Jun 21, 2010 6:17 am

I think the key point is that headphones themselves are very small in scale and use very little energy, so the likelihood that any significant (audible!!!) change is going to occur due to use is probably very small. To compare to standard speakers is somewhat misleading as everything is scaled up significantly, both in size, and energy. To compare to musical instruments, which again have significantly more size and phsyical force applied to them as compared to a set of headphones is again, misleading.
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Re: "Breaking In" AKG 701s?

Postby pwhodges » Mon Jun 21, 2010 10:19 am

gecko wrote:I don't quite understand Paul's point that a breaking-in period means ipso facto an engineering defect. Materials change when they are used; there's no way around that fact, and sometimes the optimum material requires a bit of use before it settles into a stable state.

This is true; but any engineer would rather that it was not, and will try as far as possible to avoid the effects of change by using the materials sufficiently within their elastic limits, for instance, or working towards a design where the changes have minimal effect on the important behaviours of the system. If two engineers can design comparable equipment with comparable performance, but only one requires breaking in, then I would call that requirement a defect unless it can be shown that this design has enabled some aspect of performance that could not be achieved otherwise.

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