I don’t believe anyone is stating they are ‘state of the art’, but a solid design that has obviously endured.
Keith
Keith
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Complaint thread about speaker measurements
- Thread starter amirm
- Start date
Subjective listening tests in the 1970s were afaik the first indication a lossy cabinet was one really effective way to reduce speaker colouration.
It has continued to be confirmed ever since by lots of engineers and has been used since then and is still used today as a technique to produce low colouration speakers by several manufacturers.
People's ears and the laws of physics have not changed since the 1970s so whilst it is reasonable to use more modern techniques to achieve the goal assuming that the goal is now invalid since it comes from the 1970s would be stupid.
The hifi business is beset by "rigid is better" mantra, despite nothing remaining "rigid" over the whole audible frequency range if you look at the dynamics rather than the statics.
This has resulted in some pretty shite products which have a following of disciples who believe the mantra.
tuga
Major Contributor
Unlike most manufacturers, the BBC Research Department was not only able to perform direct comparisons with live music but they could also make use of the trained ears in the broadcasting department.
Here's an educational piece about the importance of listening taken from one of the BBC papers:
9 LOUDSPEAKER EVALUATION
9.1 introduction
The obvious and definitive means of evaluating a loudspeaker is of course by listening to it. An expert listener auditioning known programme material can learn a great deal from a listening test. If all of the sound balancers who use a particular loudspeaker declare it to be excellent, then by definition it is excellent. In the author's experience at least, such universal approbation is rare. Although a group of users in an organisation like the BBC usually show remarkable accord in their evaluations, they tend to use adjectives like 'woolly, ‘hard’, or ‘chesty’, and nouns like 'honk', 'quack', or ‘lisp’. One can often hear what they refer to, but such quirks can rarely be identified by objective measurement, and are very poor guides indeed to any design modifications that might effect significant tonal improvements. (Very rarely, complimentary expressions like 'clean' or 'uncoloured' are applied; perhaps one reason for the rarity of these is that a perfect loudspeaker should presumably have no perceptible characteristics of its own.)
What is required, of course, is a well-defined relationship between subjective peculiarities, measurable deviations from 'ideal' acoustic output, and oddities in physical behaviour. A 'dreadful quack at 800 Hz' should be confirmed by a disturbance in the otherwise serene acoustic time-frequency-acceptability plot, and by an agonised writhing at 800 Hz to disturb the otherwise exemplary piston-like movement of the diaphragm.
Reality is otherwise. 'Good' loudspeaker drive units appear to exhibit just as complex mechanical and acoustic behaviour as 'bad' ones. The author is currently engaged in a project to try to find some relationship between the subjective, acoustic, and mechanical facets of loudspeaker behaviour. This has been undertaken in the knowledge that previous attempts during four decades have not yielded a final solution. Results (positive or negative) will be published in due course. Two reference works only are listed relating to this subject, each includes an extensive bibliography.
9.2 Subjective evaluation
Experience shows that comparative judgements of loudspeaker quality can be made more consistently than absolute ones. An absolute assessment of a new design is something which emerges gradually out of weeks or months of use in control rooms. Often, a pair of new loudspeakers sent out for 'field trial' will be received with cautious approval, yet returned after a month or two with a list of criticisms detailing points that have emerged only gradually from continuos use. For comparative tests, a reference loudspeaker is of course needed. This is provisionally selected during the early stages of commercial production as being a typical unit of acceptable quality; once production is well established, a new reference may be adopted as a clearer picture emerges of what is 'typical'. In fact, at least three such units are selected in normal BBC practice, to provide a working standard for acceptance testing: a spare (which is carefully stored): and a standard by which the manufacturers can assess the consistency of their output, whether by listening or by measurement. An established standard is also of course the only reasonable reference available in appraising a new design.
In listening tests, it is important that the listener should begin with as few preconceived ideas as possible. For example, a look at a response plot may cause him, consciously or otherwise, to listen for some expected peculiarities. Normally, an A/B switch is provided, and the loudspeaker to be used as reference is indicated. The loudspeakers are placed behind an acoustically transparent but optically opaque curtain, especially if any aspect of the units under test might be visually identifiable. To help eliminate room effects, the test may be repeated with the loudspeaker positions interchanged. If several units are to be tested, it is useful to include one twice — anonymously — to test the listener's consistency. (Experienced listeners expect this.)
Finally, it is essential that the listener delivers his judgement before any additional information is given to him; not (one would trust) that he might 'cheat', but rather that he might re-interpret what he thought he had heard in the light of further knowledge. Subsequent discussion may well prove valuable, but must be subsequent.
Formal tests involving a number of listeners may need further care, particularly if, as is likely, they permit less in the way of personal communication between subjects and test organiser. Past experience suggests that a particular hazard is the use of descriptive terms whose meaning seems obvious to everyone, but which can actually mean different things to different people.
Here's an educational piece about the importance of listening taken from one of the BBC papers:
9 LOUDSPEAKER EVALUATION
9.1 introduction
The obvious and definitive means of evaluating a loudspeaker is of course by listening to it. An expert listener auditioning known programme material can learn a great deal from a listening test. If all of the sound balancers who use a particular loudspeaker declare it to be excellent, then by definition it is excellent. In the author's experience at least, such universal approbation is rare. Although a group of users in an organisation like the BBC usually show remarkable accord in their evaluations, they tend to use adjectives like 'woolly, ‘hard’, or ‘chesty’, and nouns like 'honk', 'quack', or ‘lisp’. One can often hear what they refer to, but such quirks can rarely be identified by objective measurement, and are very poor guides indeed to any design modifications that might effect significant tonal improvements. (Very rarely, complimentary expressions like 'clean' or 'uncoloured' are applied; perhaps one reason for the rarity of these is that a perfect loudspeaker should presumably have no perceptible characteristics of its own.)
What is required, of course, is a well-defined relationship between subjective peculiarities, measurable deviations from 'ideal' acoustic output, and oddities in physical behaviour. A 'dreadful quack at 800 Hz' should be confirmed by a disturbance in the otherwise serene acoustic time-frequency-acceptability plot, and by an agonised writhing at 800 Hz to disturb the otherwise exemplary piston-like movement of the diaphragm.
Reality is otherwise. 'Good' loudspeaker drive units appear to exhibit just as complex mechanical and acoustic behaviour as 'bad' ones. The author is currently engaged in a project to try to find some relationship between the subjective, acoustic, and mechanical facets of loudspeaker behaviour. This has been undertaken in the knowledge that previous attempts during four decades have not yielded a final solution. Results (positive or negative) will be published in due course. Two reference works only are listed relating to this subject, each includes an extensive bibliography.
9.2 Subjective evaluation
Experience shows that comparative judgements of loudspeaker quality can be made more consistently than absolute ones. An absolute assessment of a new design is something which emerges gradually out of weeks or months of use in control rooms. Often, a pair of new loudspeakers sent out for 'field trial' will be received with cautious approval, yet returned after a month or two with a list of criticisms detailing points that have emerged only gradually from continuos use. For comparative tests, a reference loudspeaker is of course needed. This is provisionally selected during the early stages of commercial production as being a typical unit of acceptable quality; once production is well established, a new reference may be adopted as a clearer picture emerges of what is 'typical'. In fact, at least three such units are selected in normal BBC practice, to provide a working standard for acceptance testing: a spare (which is carefully stored): and a standard by which the manufacturers can assess the consistency of their output, whether by listening or by measurement. An established standard is also of course the only reasonable reference available in appraising a new design.
In listening tests, it is important that the listener should begin with as few preconceived ideas as possible. For example, a look at a response plot may cause him, consciously or otherwise, to listen for some expected peculiarities. Normally, an A/B switch is provided, and the loudspeaker to be used as reference is indicated. The loudspeakers are placed behind an acoustically transparent but optically opaque curtain, especially if any aspect of the units under test might be visually identifiable. To help eliminate room effects, the test may be repeated with the loudspeaker positions interchanged. If several units are to be tested, it is useful to include one twice — anonymously — to test the listener's consistency. (Experienced listeners expect this.)
Finally, it is essential that the listener delivers his judgement before any additional information is given to him; not (one would trust) that he might 'cheat', but rather that he might re-interpret what he thought he had heard in the light of further knowledge. Subsequent discussion may well prove valuable, but must be subsequent.
Formal tests involving a number of listeners may need further care, particularly if, as is likely, they permit less in the way of personal communication between subjects and test organiser. Past experience suggests that a particular hazard is the use of descriptive terms whose meaning seems obvious to everyone, but which can actually mean different things to different people.
tuga
Major Contributor
This paper describes the development of the BBC cabinet construction:
Factors in the design of loudspeaker cabinets
H.D. Harwood, R. Matthews (1977)
https://www.bbc.co.uk/rd/publications/rdreport_1977_03
Factors in the design of loudspeaker cabinets
H.D. Harwood, R. Matthews (1977)
https://www.bbc.co.uk/rd/publications/rdreport_1977_03
tuga
Major Contributor
Regarding the Kef cabinet and driver design, I find this interview with Jack Oclee-Brown provides aditional valuable information to what has been discussed so far:
digicidal
Major Contributor
Interesting interview, but it was a bit hard to concentrate on because I honestly was more interested in the cat (who couldn't possibly have cared less about any of it). I'm guessing that the Ayre QX-5 is exactly the right level of "warm" when powered on but not in use - though I'm sure the view out the window helps. 
Interesting (though not sure I 100% buy all of it) about the idea behind the tangerine guide.
Interesting (though not sure I 100% buy all of it) about the idea behind the tangerine guide.
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Interesting discussion.
I used to have the Thiel CS6 which used a coaxial driver arrangement (tweeter mounted in mid). It was generally effective. However I seemed to notice slight interference issues/suckouts if I moved around.
Later I owned the updated Thiel CS 3.7 flagship and currently have the slightly smaller CS 2.7 using the same newly designed coaxial arrangement.
I found the design Thiel achieved with this coaxial fascinating, especially the fact they managed to "flatten" the mid driver to, among other things, reduce the usual reflection problems with a tweeter mounted in the middle. Image here:
http://4.bp.blogspot.com/-TJzTXgsKcZU/UmQ0zUN6MCI/AAAAAAAABUE/Z76CfkaKjDA/s1600/CS3.7.jpg
Here's Jim Thiel explaining the design at the beginning of this video:
I certainly can't speak to the objective success of the approach. But subjectively both the 3.7 and the 2.7 seem to have hit it out of the park. The mids and highs (and lows!) are the most coherent I've ever heard. I can not "hear out" the tweeter or tell-tale signs of separate drivers or frequency exaggerations at all in the mids/highs and acoustic sounds are just amazingly natural sounding. Image precision and density is the best I've heard anywhere. They also maintain this coherence and even frequency over a seemingly wide range of seating positions. Thiel was a smart dude!
The ideal of a pulsating sphere goes back a long way. Peter Walker's Balls was one attempt, later resuscitated as the ring structure of the ESL63 where the loudspeaker was a section through a spherical wavefront.Interesting interview, but it was a bit hard to concentrate on because I honestly was more interested in the cat (who couldn't possibly have cared less about any of it). I'm guessing that the Ayre QX-5 is exactly the right level of "warm" when powered on but not in use - though I'm sure the view out the window helps.
Interesting (though not sure I 100% buy all of it) about the idea behind the tangerine guide.
MBL do something similar, using a completely different method in their 'petal' loudspeakers in trying to create a pulsating sphere.
Whether a pulsating sphere (i,e omnidirectional) is the right approach for domestic stereo I'm sceptical about, but as a principle for a tweeter or even midrange, it makes a lot of sense.
S.
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Whatever their possible other failings, the MBL speakers I owned routinely produced the most spooky 3 dimensional sonic images I've ever heard from a speaker design.
I would really appreciate if listening tests were done prior to reviewing measurements. I know this is the part that slows you down @amirm but perhaps you can grab a few speakers and knock-out their listening tests in a row whilst taking notes to include in their final review as the measurements become available?
OP
- Thread Starter
- #331
At this point we are so low in speaker data that I can't optimize the process that way. I need to get through measuring a bunch more so that we can see if our predictive scores are good.
My hope longer term is to conduct blind tests of speakers with our local audiophile group and see if we can align those results against listener preference scores we are computing.
In the shorter term, my goal with listening tests is to get better with correlating what I measure with what I hear. If that is a source of unreliability for you, then just ignore them. If I listen beforehand, then I would have to listen again which really lengthens the time.
Micro desk top full range utilizing a curved mica diaphragm :
http://www.bifrostec.co.jp/news/pdf/publication090700.pdf
2009 Speaker by :
Heitaro Nakajima - Who led Sony's Compact Disc development in the 1970s.
Ikuo Chatani - Sony development enginer who worked on the 1st ?? diamond coated tweeter (APM-66ES) in the 1980's.
Good 1976 short story on Heitaro Nakajima personal webpage about Audio Research Inc., Sony’s newly built loudspeaker factory :
https://www.nhlab.net/english/heitaro-s-column/a-loudspeaker-diaphragm-factory/
You can also do it with sound intensity measurement, special mic required. I have been involved with this sort of thing in industrial applications where you need to separate a particular machines noise output from that of the general noise in the area.
https://www.bksv.com/media/doc/br0476.pdf
Its not a wrong concept, but its implications need to be understood. In simplistic terms the vibration characteristics of a structure will be defined by its mass, stiffness and damping. Changing these parameters will change the vibration. Being very generalised here but if you make it stiffer and you will raise the natural frequency, increase its mass you will lower the natural frequency. Damping may change the amplitude at the resonant frequencies.
So just adding bracing without understanding and quantifying its effect is not the best way to go. Stiffer doesnt necessarily mean better.
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Nowadays, one can use devices that measure acceleration on the sides and such of the cabinet.
It would be interesting to see the results of such measurements.
It would be interesting to see the results of such measurements.
Neat takeaways for me:
ls50 uses a floating brace that has dampening material between it and the outer wall.
the kef tweeter is a compression driver
Nobody seems to know that is an r11, not r5, behind them? (or is this some previous series?)
Changeable ports instead of port plugs.
Thanks for posting that!
Hugo9000
Addicted to Fun and Learning
It is indeed the Reference 5, in one of the special "Foundry" finishes.
Kent Engineering and Foundry Edition Reference--"Blue Ice White" or "Copper Black Aluminium":
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Biblob
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Do you mean with an accelerometer? To put a accelerometer on the sides and measure the displacement of a cabinet wall?
Such an experiment has been done in this video.
Maybe @March Audio can tell if this actually worth full or not.
Well, there we go, somebody tried it out. I'm sure if you find a resonance or something you didn't know about, it's worth it.
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