Quadrature DSP 5 Speaker review

quadrature DSP model 5

Quadrature DSP Model 5 [hiendy.com]

A review of an early DSP speaker system (1996) written by someone who knows what he’s talking about when it comes to the theoretical and technical side of things. It contains a very interesting nugget (highlighted) that answers a question I asked in my piece on building my speakers, and it includes some by-now-familiar accounts of the sound of DSP…

The Model 5 presents a startling, almost shocking amount of detail without having even a hint of excess treble. Moreover, it produces similarly startling stereo image quality. The Model DSP 5 simply vaults to near or at the top in these qualities. How is this possible? The answer seems to be in the phase linearity attainable by DSP.

Everyone knows that phase linearity above the midbass is of highly secondary importance as far as tone quality and tmbre are concerned.’ Tonally, moderate phase irregularities are essentially inaudible as far as timbre is concerned. But it is important to realize that the oft-quested researches on ‘Inaudibility of phase” in the higher frequency were about timbre only. When it comes to resolution and imaging the story could change. And I am becoming convinced that it does.

Not to head too far into theory, let’s just recall for a moment that localization of sound sources involves interaural timing differences down to a resolution level of one one-hundred-thousandth of a second. In this context, it seems unsurpnsing that time-correct behavior of speakers could be important for imaging…

…  All you have to do is listen. If your experience is like me you will be something like flabbergasted to hear, say. each individual member of large choruses standing before you, as it were. “Veils removed” is some nonsense cliche, and not really the right description. The effect is more of bringing a pair of binoculars into focus. Bingo—with focus achieved, there is the sharp picture. But the sharpness is not that of edginess, of the pseudo-detail of rising top end. This is clarity as clarity is in reality, natural but defined.

I’m fascinated by the various types of speaker cabinet that exist, this one being half way between the traditional monkey coffin and slim floorstander. Those razor sharp square edges, yet it sounds amazing – can edge diffraction be as detrimental as some say it is? It may be possible that the grille (not shown in the picture) provides a smoothly-shaped surround, but the veneer on the baffle suggests they’re meant to be used without grilles if desired.

The first time I ever heard stereo

I can remember the exact moment. My dad had tried to explain to me the difference between true stereo and just wiring up a second speaker to a mono radio – and failed. I went with him to the hi fi retailer Comet to pick up our new Tandberg receiver. Unfortunately they didn’t yet have the Tandberg speakers or Thorens record deck in stock, but we bought some Koss K6 LC headphones. That evening we attached some wires to make an FM aerial, and plugged in the headphones. My dad tuned in BBC Radio 2 – some big band programme I think – and handed me the headphones. Of course, within a fraction of a second I understood what stereo was. This would have been round about 1972-73.


Tandberg TR1010

This Tandberg receiver seems to be going for a reasonable price

koss k6

Koss K6 headphones. Our version of these headphones had a slider volume control on each earcup. [www.etsy.com]

“Why the vinyl revival can sod off”

A very enjoyable article.

…I’m not really blaming vinyl as a material, or even as an inferior vehicle for the delivery of recorded music (CD has a wider dynamic range when used properly, etcetera); I’m blaming it as a signifier, as a loaded totem of rockist bullshit…

Every time someone eulogies vinyl, they seem to necessarily slag CDs at the same time, and in the process of doing that they’re voiding the cultural experiences and values of a large swathe of music fans.

A 7Hz Wall of Bass

A wall of bass…

Quite an interesting story here.

Powersoft D-Cell504 IS high power amplifier modules have been specified to drive a unique ‘Wall of Bass’ in an Austrian nightclub — as low as 7Hz….

…For the rear wall, behind the 6 x 5 meter stage, 400 kg special concrete blocks were cast and set into a 6 x 3 metre wall, using 13 tons of heavy concrete and a further 35 tons for the foundation — requiring a monumental effort… 

…Each concrete block serves as loudspeaker enclosure with pressure-resistant rear chamber which implements the perfect impulse response of a ‘closed-box’ design and maximizes the radiation resistance of the woofers through the acoustically hard surface. …

 …“A perfect plane wave is created in the interior of the club, which naturally moves along the side walls and doesn’t induce any room modes. The rear of the main floor was converted into a single bass trap to absorb the incoming wave. …

…“such an operating range and evenness of the low frequencies is overwhelming”…

…Powersoft were able to deliver 25,600 watts amping power, including 4in voice coil with custom made venting system using hardened membrane….

…“The data we measured melts in one’s mouth,” summarised Reinhard Nell. “The sound pressure level is beyond 140dB and absolutely equal at any point in the room (not that anyone would need such sound pressure levels). And you don’t have the possibility to feel 7Hz throughout your whole body every day.” Summing up, Steffen Kroschel says that everyone who has played through the system has been hugely impressed. “For some it has changed their awareness of music.”

What does a DSP active system sound like?

Legend Acoustics Tikandi

It looks as though the Legend Acoustics Tikandi system is pretty much an ideal speaker by my criteria (sealed enclosure, active DSP crossover & correction). The following extracts are from this review:

…DSP works so well it has ruined me for anything else…

…I’ve barely listened to my system in the many months since the Tikandi system left my room. At the next CES I attended, with a few exceptions, I could barely sit through most of the demos because I had grown so accustomed to the natural and lifelike sound of the Tikandi system. Everything sounded broken to me….

…There was a vividness and palpability to the presentation that was unlike anything you will likely hear without the benefit of DSP. The localization of not just instrumental images but also ambience cues brought not just the music to life but brought the entire event to life. A “you are there” quality would transport you to the recorded space in a remarkably seductive way…

…The phrase “instruments well placed within the sound stage” doesn’t even begin to describe what I heard. Each instrument became distinct in a whole new way. One of the advantages of DSP, and I think this has mostly to do with correcting the phase response, is things just come into focus in a way that only happens in the most expensive, most painstakingly set up systems (which includes dealing with the room acoustics)…

…The bass was exceptionally well defined with an almost luminescent quality. It was at the same time both thunderous and well controlled creating some of the best bass I’ve ever heard in my room. In fact the bass drum on this recording didn’t even sound like the same instrument I had been hearing… so many nuances were revealed that had been previously masked…

How Do You Become a High End Designer?

What motivates the audio engineers who design our high end equipment? How do they get into the business, and how do they arrive at their particular ‘philosophies’?

I don’t know the answers, but I can make some slightly tongue-in-cheek observations…

Observation 1: It takes half a day to learn how to build a ‘hi fi’ amplifier

Audio projects must be just about top of the list when beginners dabble in electronics or attend college electronics engineering courses. It can’t escape many of these people’s attention that by spending half a day learning to solder, and putting together a few components from a data sheet they can make an amplifier. And that amplifier, if connected to a couple of hi fi speakers via any old cables they have lying around, sounds like hi fi! In other words, it takes only half a day to become capable of building an amplifier that is 80% as good as a typical High End amplifier (and in some cases, better!) and that one’s friends and acquaintances cannot, in fact, tell it from a fully-commercial amplifier. The student may not actually understand the finer details of how it works, but his amazed friends are convinced he does. Surely many mental light bulbs illuminating future career prospects must turn on at this moment.

Observation 2: Learning new stuff is hard, but ignorance can be marketed as a virtue

I remember that when I was a kid, my route into electronic design was by sort-of understanding a few circuit blocks and then building ever-more elaborate systems based on these few blocks. Learning new ‘blocks’ was hard work and took me out of my comfort zone, so I was tempted to spend my time building overly complex systems based on the methods I knew, rather than learning more elegant methods. This resulted in contraptions like my digital polyphonic music synthesiser that was based on multiple duplicates of a circuit that stored waveforms in RAM (one of the building blocks I understood) clocked through its own DAC by its own counter. Specifically the ‘sample rate’ for each note was variable. Even in the mid-1980s when I did this, if I had had the expertise, I could have probably done it all with a microprocessor or two using a fixed sample rate. Instead, I ended up with an amazingly complex box of circuit boards which wasn’t easily expandable. It had only six note polyphony but I justified this to myself and other people by suggesting (without much foundation) that you didn’t need any more than that. It’s not a great stretch of the imagination to conceive of promoting my own limitations as a virtue:

“Here at Rational Industries we believe that signal integrity is only maintained through the use of variable sample rates. This results in a more complex system, but we think the results are well worth it. Rival systems use simpler hardware, but questions have been raised over how just musical the results can be when costs are cut in this way”.

I see plenty of high end audio products that could be versions of this phenomenon.

Observation 3: audio engineering is a back door into the glamorous worlds of high culture and ‘the high end’

This has got to be one of the most attractive aspects of getting into audio design. There must be many people who, at the age of 18, have some sense of art and culture but who, for whatever reasons, end up at technical college, or studying engineering at university. That’s what happened to me. It’s always going to be an uneasy combination: seeing your truly cultured friends forging careers in photography, graphic art, music, literature, journalism and so on. Their day jobs seem to be so fulfilling and creative, rubbing shoulders with talented people, the rich and the famous, while you work in a cube doing a job whose description would make anyone yawn if they even understood what it meant (designing test procedures for the switched mode power supplies in network routers, for example – someone probably does that). You occasionally converse with people whose main interests are football and types of cake. It’s too late now: you’re too old to start again, even if you had the artistic talent – which you don’t. You could try writing a novel, but would anyone read it? You could join a band but first you’d have to learn how to play. But there is one possibility… a direct conduit from engineering into high culture. You can build a DAC circuit based on a chip manufacturer’s data sheet in a day using a battered soldering iron on an old formica worktop. That evening you are listening to Stravinsky’s Rite of Spring played by the Moscow Symphony Orchestra, using your DAC. You can hear every instrument, every note in perfect clarity. It’s thrilling, stunning, you’ve never heard this music like this before. And it only took you a day! Just think what you could achieve if you were doing this full time!! Glossy magazines spend page after page reviewing DACs that cost thousands of pounds. It took you a day and cost £10! You could be making 10000% profit! And you haven’t even started on the exterior styling possibilities that could bump up the price. What can the enclosure be made of? Solid bronze? Some exotic hardwood? A blue LED! Glowing valves would look good, too… Yours could be a future of high end audio shows, magazine interviews, photo shoots, celebrity endorsements. Your high end factory showroom and high end listening area could incorporate high end sofas and a high end coffee machine. You could listen to music as your day job. This is going to be great!

On a slightly more serious note, the world of real engineering is a pretty harsh, unforgiving place. Watching a recent TV programme on the building of London’s new Crossrail link I was struck by the unbelievably high stakes involved in getting the design right: blocking off half of London to dig the streets up, shoring up buildings that were sinking as the tunnel was dug under them, ensuring that existing cables and water pipes weren’t disturbed, and so on. As a job it must be unbelievably stressful, arduous and dirty (if you’re at the sharp end) but ultimately quite boring compared to recreating the Moscow Symphony Orchestra from your own hi fi brand at a show in some interesting location. And yet the people who do it are probably paid no more than the man who designs the crossovers that go into the latest version of the perennially-flawed  passive speaker. I know which job I’d rather be doing.

Observation 4: engineers are not scientists and scientists are not engineers. Renaissance men are rare

Engineers are not paid to carry out scientific experiments, and scientists are not paid to build stuff that can be sold. When an engineer enters the audio business, he does so by being a manufacturer of a component that already exists within a system of received wisdom. He does not re-invent the audio system; merely promotes his minor variant of ‘an amplifier’ or ‘a record deck’. The customer may fondly imagine that this technical demi-god has spent his life experimenting with radical new topologies, breaking the mould, thinking outside the box, starting from scratch and establishing the ultimate truth – which turns out to be a vinyl gramophone, single ended valve amplifier and pair of single driver speakers. But no such experiments have, in fact, been carried out. The multinational corporations plough their own particular furrows, and the so-called high end designers potter around at the margins just repeating their own limited repertoires over and over. It’s conceivable that there are audio system ‘topologies’ that are as yet untried, but that the corporations have bigger fish to fry, and the high end designers’ skills are just too parochial.

Observation 5: embellishment is easy

It does no harm, looks good, costs a predictable amount that is less than it looks, and is directly convertible into no-risk profit. Chips containing a complete DAC that works astoundingly well, cost a few pence. Embellishment with bronze chassis, 1 farad of smoothing caps, illuminated logo etc. does no harm at all. It is no more difficult to design than a more ‘basic’ version, and an entire philosophical narrative can be woven around it. Ultra-expensive record decks are a fine example: the designer simply builds layer upon layer of embellishment upon a basic system that works. Take away all the embellishment and the system will still work – it’s only a motorised platter for goodness’ sake! The designer can use mechanical embellishment (suspend it on air bearings) and he can go supposedly high tech on the speed control with – gasp – microprocessor regulation with a – gasp – LED readout of speed to three decimal places. None of it does any harm, and is simple stuff compared to say, the design of a mobile phone bluetooth interface IC that sells for $0.05. But it impresses people much more.

Observation 6: Philosophy is easy and fun!

It takes only words to spin an entire audiophile ‘philosophy’:

“Over many years I have come to the conclusion that excellent performance requires an excellent power supply – a racing car can not perform at its best when running on old chip fat! – so here at Rational Industries we use only power cables of a type that are used in the space and aeronautical industries. We have developed our own proprietary fuse holders that ensure exemplary power integrity even under the heaviest loads, and this ensures that the music never loses its composure”.

It took about two minutes to come up with that particular High End philosophy. It’s actually quite fun. Picking just the right words to avoid any commitment while still sounding sincere and highly technical probably gives quite a creative buzz in itself, I should think.