Interview With Dr. Rod Crawford

[Keith_W]

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Introduction
Dr. Rod Crawford of Legend Loudspeakers is well known figure in Australian hi-fi. His most famous employer was Linn hi-fi, makers of the famed LP-12. During his time at Linn, he designed a number of speakers which were very well received - the Kaber, Keltik, Nexus, Tukan, and Helix. This helped to treble Linn's loudspeaker sales. He then returned to Australia to set up Legend Acoustics.

SNA members would know how good the Legend loudspeakers are - in February this year Norpus hosted a bookshelf speaker shootout (results from post #132 onwards). The winner was the Legend Kanga.

Links: Legend Loudspeakers

<div align="center">[attachment=3132:rcc.gif]
Dr. Rod Crawford, of Legend Acoustics</div>

Q: Thank you for agreeing to participate in this interview Dr. Crawford. Can you tell us how you first became interested in music and its reproduction? And in particular how you went from this to gain such experience in speaker design?

I got seriously interested in hifi when I returned from Oxford in the early 1970s, having heard live in the UK some of the world’s great ensembles (eg LSO playing Elgar’s cello concerto with Jacquelyn du Pre in Festival Hall, the Amadeus Quartet playing Beethoven’s late quartets in the Sheldonian Theatre, etc.) only to find a dearth of good live classical music in Tassie (then the TSO in the converted Odeon Cinema was pretty woeful; now it is very much better and in Federation Hall, though the reverberation times in this hall are longer than I would prefer).

In Oxford I had a fairly basic hifi system – a Garrard SP25 MkII turntable with a self-made plinth & cover, a Quad valve mono-FM tuner (FM1?), a mono-valve amp built & handed-down by a fellow student and a self-made speaker consisting of a Goodman’s Axiom 10 driver and a Scandinavian tweeter with a single capacitor crossover as suggested by the hifi shop in North Oxford (opposite Oxfam). I left the system to Oxfam when I first returned to Tassie in 1971 (my father had died of cancer in late 1971 while I was writing up my D Phil thesis).

My first serious hifi system in Tassie consisted of a Thorens turntable, a second-hand Plessey stereo valve amp and some AR6 speakers. I then got hooked on the hifi upgrade-path but as a newly married teacher had little funds. And I knew little about electronics to build or modify amplifiers etc – the only electronics my physics/metallurgy course at UniMelb had taught me in the early 1960s was the characteristic curves of valves in Physics 2 pracs. However, having done my D Phil in the Department of Materials Science at Oxford, I guess I had an understanding of materials - which is what loudspeakers are mainly about. The first loudspeakers I then built were from magazines, particularly the long-defunct Practical Hifi and Dave Berriman’s excellent designs – though I never had the courage to tackle his formidable transmission-line design!

Q: Tell us a little more about your time at Linn.

Well, I got the job by a bit by accident. My wife comes from Yorkshire and we returned there in 1985 so she could spend some time with her aging parents. I first got a job in run-down Batley, midway between Leeds & Huddersfield, teaching unemployed and largely uninterested older teenagers some very basic electronics - it was really hard work that paid a pittance! Then one day I was reading Hifi News & Record Review and saw an advert for a loudspeaker designer at Linn. Despite having never designed a loudspeaker before, only built and modified s other peoples’ designs, I was desperate to get out of Batley so I applied for the Linn job – and after a long & rather torturous process during which at many times I assumed that I had been rejected, I did get the job, much to my wife’s horror as her only images of Glasgow were of its dreaded slums (she came, like me, to love the place, with its Victorian architecture & parks and the surrounding countryside).

For the first month at Linn I read everything I could about the theory of loudspeaker design – Martin Collom’s book, the Thiele/Small papers etc. Then Linn’s US distributors got cold feet about a new power supply for the Sondek and Linn needed new products to launch. So Ivor Tiefenbrun (Linn’s MD) gave me the task of fast-tracking a large book-shelf speaker to compete with a very successful ported Mission loudspeaker at the time. We worked like slaves, often to midnight, but we got it out in less than 6 months. And I ended up carrying the can (no pun intended) for the first ported Linn loudspeaker, which the sales guys hated – also for it being bi-wirable - because they had previously rubbished both ideas. Fortunately, Linn did have a policy of ultimately deciding these things by blind listening tests – and the ports & bi-wiring won out. The Nexus went on to be one of Linn’s commercially most successful speakers, outselling each of the previous Kan and Index loudspeakers by over three times.

And so on for my next 3 years at Linn with the Kaber, Keltik etc but I think this gives the flavour – if interested, people can read more about it at www.legendspeakers.com.au/legendstory.html

Q: Why did you decide to return to Tasmania?

As indicated above, my first return to Tasmania in 1971 was largely for family reasons – and the second return in 2007 was likewise for (different) family reasons. It is also a beautiful place to live, if slightly isolated. I guess it is finally returning to my roots – I was born & grew up in Tasmania.

Q: What type of music do you enjoy? What electronics do you use at home?

My music tastes are fairly catholic, though they gravitate towards classical music where I like most forms, with a particular preference for chamber music – my favourites being the late Schubert & Beethoven quartets. But there are many symphonies, from Haydn to Shostakovich, as well as concertos, from Vivaldi to Sculthorpe, that I also love. Although I like church choral music, I am not a great fan of opera – perhaps because I heard too many Dame Nellie wanna-be’s at the free Myer Music Bowl concerts when I was a student at UniMelb! With rock music, I’m not sure how I would classify my tastes. I grew up with (and still like) bands such as the Stones, Beatles, Pink Floyd, Jethro Tull, Genesis, Heart etc – more recent bands that I enjoy are Radio head, Silver Chair, Metallica etc. Then I like Paul Simon, Peter Gabriel, Phil Collins, Patricia Barber, Tori Amos, Rebecca Pidgeon, Laurie Anderson etc whom I’m not sure how you would classify – perhaps as people with something interesting to say musically! I don’t have a lot of time to explore less well-known pop artists, though I do enjoy listening to JJJ in the evening when not listening to Classical FM.

My home electronics (which has evolved through a lot of substages such as Rega Planar & Sondek turntables and Quad II & Levison 29 amps) currently consists of a Sony SCD9000ES CD/SACD player, a Denon 2910 universal player (mainly for DVDs including DVDAs), a DEQX PDC (DAC/digital Xover-equaliser/preamp) and home-made 4 channels of power amps for driving the Kumbar Wirris (Big Reds) actively. As you can see, I eventually learnt a bit more about electronics and have built a number of power amps over the years, largely from kits but heavily over-engineered, since I can never afford the power amps of my dreams (eg Classe Omega). The current power amps, just finished, consists of 2 channels of Leach class A/B amps for driving the Kumbar’s midrange and 2 channels of Silicon Chip ULD 15W pure class A for the tweeters – perhaps not Omega class, but not far behind with a very dynamic and clear sound without being fatiguing (that is, if the recording is not fatiguing)! And of course the Kumbars have 500W class D amps built into both bass channels. Because one can bypass the digital Xovers in the DEQX the system is also easily adapted to speakers such as the Kantus & Kamas with passive Xovers.

Perhaps it should be noted that all this current electronics is designed to minimise distortion (difference/lack of fidelity between the musical performance and its reproduction) in whatever form. As discussed below in relation to planar/ribbon speakers I believe adding even ‘benign’ distortion, in the form of turntable systems, valve amplifiers or planar/ribbon drivers, is a very slippery slope to go down.

<div align="center">[attachment=3124:210px_Isobaric_spk.PNG] [attachment=3125:kurlo3sm.JPG]
Schematic of an isobarik speaker on left, Legend Kurlo subwoofer on right</div>

Q: Linn is known for its isobarik subwoofer design. Your current subwoofers, the Kurlo and the Kurlette, appear to be sealed box designs. What are the pros and cons of the isobarik design, and why did you decide to adopt a more conventional subwoofer design?

I think there is a lot of misunderstanding about the ‘isobarik’ principle, some of it promoted by Linn for commercial reasons (and it was not Linn’s idea first but was described at least in Olson’s book on Acoustics a decade earlier - so it should not have got a US patent)! Linn sold its advantages in terms of the back drive unit removing the built up pressure on the front unit, allowing the latter to move more freely and so more deeply. However, this ignores that the back unit itself has to compress the air in the sealed box – there is no free lunch. A better explanation is that the 2 drive units act as one at low frequencies where they are tightly coupled acoustically (provided the driver separation is much less than the wavelength) and so the effective mass of the driver is doubled, thereby lowering its resonance frequency (by the square root of 2) while maintaining the high damping factors because there are 2 magnet systems. An easier way to achieve the same result (given the second drive unit behind is a real pain to build) is just to double the mass and magnet system of a single driver. This is what we do at Legend with our sub-woofers.

Q: How has your philosophy changed since you left Linn? Australian listening rooms are different to UK listening rooms - has this had any influence on your designs?

When I first went to Linn my design philosophy was heavily influenced by the BBC school of design – LS5/3As, Spendor BC1 etc which were tonally quite neutral but were not dynamic enough for Linn’s ‘foot-tapping’ philosophy. So I tried to achieve both – or at least a better balance between the two philosophies. Previous Linn speakers like the Kan & Index had large holes in their frequency response between 1-3 kHz which removed hardness due to bass/midrange driver breakup but caused all pianos to sound like honky-tonks.

UK listening rooms tend to be smaller with hard (eg stone) reflecting walls so their reverberation and bass response tends to be different to that of Australian rooms which are often larger and more highly damped in the bass (gyprock walls tend to flex at bass frequencies). I don’t think it leads to a different design philosophy as perhaps different fine-tuning of speakers when listening to them as part of the design process – for example, the bass of the loudspeakers can be less overdamped (bigger & fatter if you like) to compensate for the greater damping of the rooms in Australia.

[Keith_W]

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Legend Kanga bookshelf loudspeaker - winner of an informal SNA bookshelf speaker shootout</div>

Q: What sonic attribute do you find most important when it comes to loudspeakers? How do you achieve it?

What makes a good loudspeaker? For me it is one that reproduces all signals accurately (high fidelity) and allows one to get as close as possible to the original recording. And if it will do this for all music, given the wide range of music from simple acoustic music through opera to rock concerts, then it will certainly reproduce accurately all sounds from DVDs etc - provided of course it is fed accurate signals by equipment before it in the reproduction chain.

Music usually consists of at least one or more of the following elements:

1. melodies (tunes)
2. tonal ‘colours’
3. dynamic contrast (micro and macro)
4. rhythm

and a good loudspeaker should be able to reproduce each of these elements of music accurately.

For a loudspeaker to be high fidelity for the first 2 elements (tunes & tone) it must have a good frequency response and low distortion in the frequency domain; while the latter 2 elements of music (dynamics and rhythm) rely on a loudspeaker’s ‘speed’ in the time domain – what Linn used to call ‘foot-tapping’ ability. In an ideal loudspeaker the frequency response and the time response are simply related, but in real, non-linear speakers, the relationship is more complex.

How do you achieve these in practice? Good frequency response depends on choice of drivers and their integration through crossovers, given it is not possible to get high fidelity over the whole range of human hearing (say, 20 Hz to 20 kHz) from a single diaphragm - because of diaphragm ‘breakup’, energy beaming etc. In this I think planar/ribbon speakers or conventional drivers are not too different.

On the other hand, the ‘speed’ of a loudspeaker is characterized by how it handles a very short impulse of signal (music) fed to it by its driving amplifier. The results can be viewed in 2 parts:

1. the response to the initial rise of the impulse – its ‘attack’
2. the response to the fall of the impulse – its ‘decay’

In both parts I believe that conventional drivers are more accurate than planar or ribbon drivers and so I use the former, even though it would currently be trendier, and so perhaps commercially more savvy, to use the latter.

Some people think that planar/ribbon loudspeakers have faster attack because of their lower mass. But the ‘speed of attack’ is actually how quickly the speaker driver reacts to an incoming signal. Thus this ‘speed’ is really its ‘acceleration’ under the forces generated by the signal in the amplifier. And elementary physics teaches us that acceleration = force/mass i.e. acceleration increases as the force increases and mass decreases.

Planar speakers can have lower mass than conventional drivers (though this is not always the case). But electrostatic drivers particularly can only generate very weak forces. This is demonstrated by the low maximum sound pressure levels (SPL) that electrostatic speakers can produce before arcing between the membrane and fixed plates occurs. Therefore the ratio of force to mass which determines acceleration is actually be lower in electrostatic panel speakers. Similarly because of the open geometries of the driving mechanisms involved involved, magnetic planar and ribbon drivers can be difficult to generate large forces and so greater speeds of attack.

I also believe panel loudspeakers have poorer decay properties relative to conventional loudspeakers. This is ultimately due to their larger size and their non-rigid structure which makes it very difficult to stop them ‘breaking up’ i.e. going into uncontrolled resonances which are the major form of distortion in loudspeakers. For some types of music such as acoustic guitars etc these resonances and slow decay characteristics of the panel/ribbon drivers mimic the resonances and slow decay characteristics of the guitar strings and so may seem to enhance the acoustics – or even cover up distortions further back in the instrument to ear chain. However, as stated above, I believe that adding distortion, even ‘benign’ reverberation like this that may appear to add to the body of the sound or add its spatial properties such as depth (or second harmonic distortion from valves/output transformers that seems to add the tonal richness), is a very slippery slope - partly because it tends to make everything sound the same (a bit like adding 3 tea-spoons of sugar to all drinks); partly because it is only really appropriate for acoustic music and not other forms eg electronic where the ‘notes’ start & stop quickly; but mainly because, by hiding other distortions, we have less incentive to improve the reproduction system as a whole and get stuck with the infidelities of the current system.

With conventional (dynamic) drivers an attempt is made to keep them as small and as rigid as possible, so that they remain ‘pistonic’ over their operating frequency range and do not ‘break-up’ to form resonances which must then decay over time. Ideally they will then simply move in total unison with the supplied signal and have high fidelity with the supplied signal forces (music etc). Of course, conventional drivers are never ideal and one must make compromises – apart from choice of drivers, one of main ‘arts’ of loudspeaker design is integrating them through the crossovers. I have a particular phobia for poor integration of drivers where one can hear each driver as distinct units, no matter how good they may be. The ear/brain has poor (though not imperfect) long-term acoustic memory but very good short term acoustic memory so it picks up, very quickly and continually, poor integration of the drivers as the music fluctuates between frequencies.

Resonances related to the cabinet holding the drivers, both the panels and the air inside, is are also important but much less so than the drivers, and are generally more readily reduced eg by bracing & dampening the panels and by damping material inside the air space as well as making its sides non-parallel to inhibit any standing waves. I thus believe a lot of nonsense is talked about the effect of ‘boxiness’ of conventional loudspeakers – it is often more related to the lack of their Hass effect which panel/ribbon exhibit due to their open-backs allowing the rear waves to be propagated and bounce off the walls behind. Hass & others have found that if the time delay between these reverberant waves and the direct waves from the front of the diaphragm is less than about 15 ms (i.e. the rear wall is less than about 2m away) then the ear/brain integrates the 2 waves to form a warmer more spacious sound – but effectively one different to the original sound and so distorted/not high fidelity. I believe that if one wants to use artificial reverberation (eg to make a bad recording more palatable) it is better to do it in a more controlled & selective way in the digital domain by DSP as some DVD player do.

Apologies for such a long answer! I guess my short answer to your question should have been that a good loudspeaker must be as transparent a window to the music as possible - with good recordings sounding good & bad recordings sounding bad. We would not put up with looking at paintings through distorted or dirty glass – or take photos with Vaseline smeared permanently on the lens (even though the latter may make some portrait shots more palatable)! However designing a good loudspeaker is not easy – despite those who think that all you need is good drivers and a saw. I once asked Bruce Candy of Halcro why, now having reduced amplifier distortion to vanishing levels, he did not turn his attention to this major source of distortion in the reproduction chain and he replied that loudspeakers were far too difficult!

Q: Most of your speakers are two way designs, or two way designs with active bass modules. All the larger speakers are in MTM configuration. Most other Australian speaker companies use multiple drivers in a four-way configuration with up to five or six drivers in the box. Why do you prefer fewer drivers?

It is mainly KISS (keep it simple) – given that drivers are the main source of distortion, the more of them there are the more likely something will go wrong. KISS allows simpler Xovers and avoids band-pass filters, where the high & low pass filters interact, that are hard to get right in analogue Xovers. It particularly allows only non-distorting air-cored inductors and no distorting capacitors to be used in the signal path for the critical mid-band. The drivers we use have high power/long throw so we do not need multiple drivers to achieve sufficient dynamic range.

Q: What drivers do you use on your speakers?

Given that Australian HiFi regularly publish in review what drivers I use there is no trade secret in this! Up until about 3 years ago I mainly used Audax aerogel drivers for mid/bass units. The cones were a composite of carbon-fibres & Kevlar for strength and so high break-up frequencies as well as damping gel to control the resonances when break-up did occur. However Audax suddenly stopped making the drivers except for car production in Europe. For our Monitor range (Kama, Joey etc) we now use a doped paper-fibre cone manufactured specifically for us and Subsonic in Taiwan that has a very similar properties and sound to the Audax drivers (and I tried many others from Peerless, Vifa etc that did not); and for our Reference Monitor range (Kantu, Kurre etc) we use a modified Scanspeak 8545 driver. The tweeter for the latter range is now a very expensive Visaton pure ceramic tweeter that I found cleaner (i.e. less distorting) than any others I tried (Scanspeak Revelator, Vifa ring-radiator etc); for the former range we now use a Peerless silk-dome tweeter made specifically for us with a large backing chamber that is also extra-ordinarily good and much better than anything else I could find its price range.

Q: Have you experimented with more exotic driver technology, such as air motion transformers, ring radiators, compression drivers, horns, or ribbons?

Yes, I have tried ring-radiators and ribbon tweeters and I don’t think they are as accurate (transparent, non-distorting) as the tweeters I am currently using. I have not tried the others but have heard them and think likewise about them.

Q: What is your view on the importance of the good time domain behaviour, low energy storage, low dynamic compression, frequency extension, high sensitivity and frequency linearity in loudspeakers? To what extent do you like to trade any of these to improve another?

From my very long answer to your question about what makes a good loudspeaker I hope you may have realised that good time behaviour (including low energy storage, dynamic compression etc) is as important as good frequency behaviour (linearity and extension) when it comes to reproduction of all types of music.

The trade-offs depend on the size and cost of the loudspeakers so it is difficult to give a simple answer – in part it is intuition (experience?) when listening to and ‘voicing’ the loudspeaker with many different types of music. Generally, the bigger and more expensive the loudspeaker, the less are the compromises. As suggested by the recent review of our Kumbar Wirris in Australian Hifi there are very few compromises, particularly in the DEQX version – they are +/- 1dB from 20 Hz to 20 kHz, “stop & start on a dime” and they are very transparent/revealing – so that what you hear is pretty much what is on the recording, good or bad.

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Legend Kama speaker on left, Linn Kaber on right - notice the similarity.</div>

Q: The Legend Kama has a passing resemblance to the Linn Kaber. How similar are the designs?

The Legend Kamas & Kantus are descended directly from the Linn Kabers (one of my designs there) where in 1986 we were one of the first companies to add a second mid/bass unit in a floor-standing cabinet that both added more bass and eliminated the need for a stand. I think the NIH (not-invented-here) syndrome is stupid.

<div align="center">[attachment=3121:kumbarON.jpg] [attachment=3120:kumbarOC.jpg]
Legend Kumbar Wirri</div>

Q: Your reference loudspeaker, the Kumbar Wirri, has an interesting design. It may be ordered with an external passive crossover, or with a DEQX. DEQX is familiar to most of our readers. Which is your preferred configuration, and why?

Undoubtedly the DEQX version, because its digital Xovers and equalisation make the Kumbar Wirris more accurate than is possible with passive Xovers. The DEQX website (www.deqx.com) has various brochures and white papers explaining in more detail why this so. BTW, I first looked at such digital loudspeaker systems at Linn in the late 1980s when I started collaborating with Malcolm (Omar) Hawkesford at the University of Essex who had a couple of PhD students working on these things - we took down a pair of Kabers and I was very impressed by their improvement. Unfortunately it, like improvements in materials, got lost when I could not take the political back-stabbing of Linn anymore (though technically it was excellent).

Q: The Kumbar Wirri is a very unique design with its side firing woofer. Can you tell us the advantages of this design and the development process associated with deploying it in this way?

I’m not sure it is all that unique – it is difficult to do something truly unique in a field as old as loudspeakers! Anyway we have 2 opposite side-firing woofers mainly because their action/reactions tend to cancel and so the subwoofer cabinet provides a stable, vibration-free base for the mid-range/treble cabinet sitting on top. As well, it has the advantage that the 2x10” drivers have about the same surface area as a single 15” driver and so can move a lot of air (which needs to quadruple for every octave lower in frequency) without an extremely large cabinet panel that single 15” driver would require. Lastly, having four separate subwoofer drivers (2 per stereo channel) helps the dispersion of the bass into the room and reduces room resonances.

Q: What crossover slope do you have on the passive, and what slope do you recommend on the DEQX?

The acoustic crossover slopes for the passive Kumbars is about third order (about 18 dB/octave) consisting partly of the electrical Xovers and partly roll-off of the drivers. At one time I used to worry about the type (Butterworth, Linkwitz-Riley) of Xover, knowing their different theoretical characteristics in terms of phase etc (a Canadian called Bullock wrote a great summary paper that I read while at Linn) but now feel that you cannot get to even approximate them with real drivers. I know that 1st order Xovers have some theoretical advantages in terms of phase etc but in practice they can lead to much more distortion as drivers start to break-up, poorer dispersion patterns caused by drivers interacting over a wider range of frequencies etc. Indeed, with the DEQX, I use as steep digital crossovers as possible – 96 dB/octave - so that any driver interaction is minimised (with passive Xovers these sorts of slopes are not possible due to component accuracy etc).

<div align="center">[attachment=3122EQX_PDC.gif] [attachment=3123:hypexsm.jpg]
DEQX on left, Hypex 500W Class D amplifier on right</div>

Q: Have you found that the DEQX adds any coloration to the sound compared to the passive network?

All components in the reproduction chain add some coloration (distortion) to the signal (music)! My experience, and that of Edgar Kramer who recently reviewed them, is that the DEQX version is less coloured than the passive version, if only because its frequency response is more accurate – but also the DEQX version is, by definition, ‘active’ with each drive unit directly coupled to its amplifier which gives rise to greater dynamics etc. The DEQX PDC-300 that Edgar reviewed contained 4 class D Hypex power amps built-in for ease of use (all you have to do is add a CD/DVD player and other sources) but you can also buy the PDC without the power amps and add your own, as I do in my system with the Leach/SC ULD combination, where the amps can be tailored to the drivers. Some, but not me, may even like to use valve amps to give greater euphonics (distorton) etc – in this context I gather that at ASoN (Audio Society of NSW) where they were demonstrated recently, a few people preferred the passive version driven with valve amps to the DEQX version with Hypex amps. However, the consensus there was that the digital-to-analogue conversion and preamp in the DEQX PDC was excellent.

Q: If you could make a cost-no-object speaker using the best components available, what would it be?

It would very probably be based on the Kumbar Wirri (Big Red) concept with the DEQX digital Xovers/equalisation. The bass/base module would probably stay much as it is – as Edgar Kramer says in his review the bass is about as good as it gets (and probably can get).

I guess if cost was no object I would experiment with ceramic or even diamond mid-range units as well as diamond tweeters in the top module. I might try more exotic materials such as polymer concrete for the cabinets, which are even more rigid & better damped than MDF, and can be moulded to curved shapes that are inherently stronger than flat panels and also might further reduce internal standing waves and external edge diffraction effects of the midrange/treble, over and above the measures Legend already takes to minimise them.

On the electronics side, I guess one could try to implement even better DACs and analogue output stages. The PDC that I personally use has XLR digital outs so this could be done externally – at one time I looked at the CEC DX71 mk2 DAC which had some pretty good write-ups but they were too expensive, particularly for 4 channels, for a poor loudspeaker designer! And of course a pair of Classe Omega amps (costing around $30k each) or whatever would undoubtable trump my current Leach/Silicon Chip amps!

Then I would spend a lot of money modifying my current listening space into a dedicated listening room……….and spend a lot of money paying for the divorce and alimony costs!

Thank you for your helpful responses Dr. Crawford. I am sure that this would make interesting reading for many of our members. All the best to you.

[Keith_W]

*bump* interview posted.

[Drizt]

*bump* interview posted.[/b]

Great work again...

Thanks for organising the interview Keith.

[jaspert]

That was a good read and cheers to both parties for the time and effort involved.

[Aslan]

Many thanks Keith.............an excellent read.

[TJP]

Wow, what a great interview Of note was the fantastically in depth answer to the "sonic attribute" question.

Thank you to both Keith for organising the interview & Dr Crawford for taking the time to answer Keith's questions.

[ozcal]

Wow, what a great interview Of note was the fantastically in depth answer to the "sonic attribute" question.

Thank you to both Keith for organising the interview & Dr Crawford for taking the time to answer Keith's questions.[/b]

Yes Keith , once again a great read and you covered all the questions and lots more besides that I would have asked.The picture of the Kabers and Legend speakers side by side made me smile as it was always something I wanted to ask Rod about.Rod's insights behind the scenes at Linn are always amusing.
Rod thanks for contributing to the forums, I have yet to hear any of your own speakers but the Tukans , Nexus and Keltiks were always some of my favourites when I was working in retail in the UK and I sold quite a few pairs of Tukans here in sunny Perth.
Thanks both,
Gordon

[k371n]

A great read indeed.
Reminds me of interviews mags like Stereophile did.
A little bit of everything, which makes it all entertaining.

Thanks Dr. Crawford for sharing your thoughts + experience in this forum
and to Keith for this series.
cheers
k_

[JA]

*bump* interview posted.[/b]

Great Stuff

Well done,

Best
JA

[Moondog]

An excellent read. Great Work

Liked this bit Quote
Some, but not me, may even like to use valve amps to give greater euphonics (distorton) etc – in this context I gather that at ASoN (Audio Society of NSW) where they were demonstrated recently, a few people preferred the passive version driven with valve amps to the DEQX version with Hypex amps. However, the consensus there was that the digital-to-analogue conversion and preamp in the DEQX PDC was excellent.

Moondog

[Keith_W]

Ozcal you're welcome. It was you who floated the idea of interviewing Dr. Crawford in the first place And BTW unlike some of my previous efforts where I wrote all the questions, this time I got input from the rest of the mods to get ideas for questions. In its original form some of the questions may have been a little "professionally confronting" (as JA and LuckyDog put it) so I toned down some of them. As it is, I was a little nervous when I hit the "send" button as some of those questions were still pretty pointed (especially the bit with the Legend and Linn speakers side by side). Fortunately Dr. Crawford was most amicable and gracious and did a great job answering the questions.

I wonder whether Grumpy spent yesterday evening in the bathtub with a printout of the interview

[norpus]

Well done, great interview and excellent to get to understand the history of the Legend. I also liked the plug for our previous bookshelf gtg where the Legend Kanga did surprise us very pleasantly

[hiSky]

Well Done Keith!!!

[JiriAU]

Thanks Keith really excellent reading.
Would love to find more about polymer concrete availability, design and so on


‘I might try more exotic materials such as polymer concrete for the cabinets’

[LuckyDog]

Thanks Keith. Really interesting stuff. I do enjoy listening to Legend speakers and I enjoyed the responses from Dr Rod. I actually rang him some time back to discuss the Big Reds and I found him to be a complete gentleman and it gave me a great insight into his passion for his products.

[terry j]

An excellent read. Great Work

Liked this bit Quote
Some, but not me, may even like to use valve amps to give greater euphonics (distorton) etc – in this context I gather that at ASoN (Audio Society of NSW) where they were demonstrated recently, a few people preferred the passive version driven with valve amps to the DEQX version with Hypex amps. However, the consensus there was that the digital-to-analogue conversion and preamp in the DEQX PDC was excellent.

Moondog[/b]

I'm sure you realise that the deqx can be used active with valve amps, that may even help to extract every last bit of their rather poor damping characteristics!!

The deqx with hypex modules is a standard item, and that just happens to be the way he has set up the legends.

No, a better comparison would have been active deqx with valve amps if they so desired, of course it would have required someone who took the time to set it up, which I'd imagine was not thepurpose of the day.

Wasn't this phenomenon of 'euphonic' distortion of valve amps covered elsewhere today??

EDIT yeah, found it!!

Often, the first impression is that the valve sound presents extended "dimensions", more "air", and is more "living". The impression after a week or month, however, is that all recordings sound very much alike, and the "airiness" appears on all records. It does not even sound like air anymore, instead more like a slime that pollutes every record you play. No wonder, since it is not a real, recorded quality but a "speaker characteristic" added to all reproduced material. "Sameness" is another word for it."

[Moondog]

I'm sure you realise that the deqx can be used active with valve amps, that may even help to extract every last bit of their rather poor damping characteristics!!

The deqx with hypex modules is a standard item, and that just happens to be the way he has set up the legends.

No, a better comparison would have been active deqx with valve amps if they so desired, of course it would have required someone who took the time to set it up, which I'd imagine was not thepurpose of the day.

Wasn't this phenomenon of 'euphonic' distortion of valve amps covered elsewhere today??

EDIT yeah, found it!!

Often, the first impression is that the valve sound presents extended "dimensions", more "air", and is more "living". The impression after a week or month, however, is that all recordings sound very much alike, and the "airiness" appears on all records. It does not even sound like air anymore, instead more like a slime that pollutes every record you play. No wonder, since it is not a real, recorded quality but a "speaker characteristic" added to all reproduced material. "Sameness" is another word for it."[/b]

Yeah I do , And I would be great to listen to such a combination using valve amps designed specifically for the frequency ranges seen . Ive heard of analogue, valve and single speaker people using digital crossovers and equalizers ( highly modified ) in their systems with great results .

I also know of speaker manufacturers using modified DEQX units .

I missed the "Wasn't this phenomenon of 'euphonic' distortion of valve amps covered elsewhere today??"

But did read this
http://www.stereo.net.au/forum/index.php?s...ic=3872&hl= post number 4 , About bi wired speakers

From the article:

"What does this sound like? Well, usually, just as you may expect from physics, it appears as a change in the reproduction of space and sound stage. Often, the first impression is that the "biwired" sound presents extended "dimensions", more "air", and is more "living". The impression after a week or month, however, is that all recordings sound very much alike, and the "airiness" appears on all records. It does not even sound like air anymore, instead more like a slime that pollutes every record you play. No wonder, since it is not a real, recorded quality but a "speaker characteristic" added to all reproduced material. "Sameness" is another word for it."

Moondog

Forgot to mention 900w of bash amplification and some parametric equalization went in to the system this arvo
Pokes tongue out

[mondie]

Excellent reading Keith & Dr Crawford Thanks to both of you for taking the time

Cheers Mondie

[davidsss]

Excellent interview, very interesting, thanks to both Keith and Dr Crawford.

I have never heard either Linn speakers or Legend speakers but now I'd like to hear both.

DS

[56oval]

Very good interveiw Keith and read .
The ceramic ,diamond ,concrete and modified DEQX have been done before .I think a interview in Perth is required.
Using tube amps ina active system isn't that hard get the output tranny's wound for the correct frequencies .

Cheers.

[wadiaman]

Thanks for taking the initiative and making the effort Keith and for Dr Crawford for taking the time to respond.

I have auditioned the Big Reds and subsequently exchanged a couple of emails of my thoughts with Dr Rod and he was again more than wiling to discuss his philosophies and share viewpoints. Full credit to him and best wishes to Legend.

[Keith_W]

Very good interveiw Keith and read .
The ceramic ,diamond ,concrete and modified DEQX have been done before .I think a interview in Perth is required.[/b]

Thanks 56. You talking about Pat from WAR Audio?

[Tony M]

I know it's repetitious, but I've just gotta say these interviews are absolutely brilliant, and this is one of the best yet.

Congrats, Keith, well done. Big thanks to Dr RC......certainly puts his speakers into the must-listen category.

Cheers
Tony

[Keith_W]

Thanks Tony (and all the guys who responded). Just to let you know, there is an article by Dr. Crawford in this month's A/V Lifestyle magazine.