DIY audio system price breakdown

I know that my article on designing and building an audio system has puzzled a couple of people by claiming that £380-ish is sufficient to build a fully-functioning system. As I said in the article, some of it was secondhand, and the breakdown of the components was:

• Pair of old Goodmans speakers £20 (I used the enclosures and added on new baffles)
• Pair of AR bookshelf speakers £0 (again, I just used the enclosures. I had them already, but have seen similar speakers fail to sell on eBay for £5)
• Dell tower PC with Windows 7 £40
• Creative X-Fi card £30 (provides the DACs)
• M Audio Delta card £20 (slaves to the X-Fi card via SPDIF and acts as destination for audio apps, and as the source for my software. Originally the X-Fi could do it all, but this card had to be added when upgrading from XP to Win 7 due to a driver issue. I had it already, but there is a completed listing on eBay for this price inc. shipping)
• Pair of 902.222 drivers £50
• Pair of SKO100 drivers £18
• Pair of DT25N tweeters £30
• Tweeter protection caps £20 (Maybe I fell for the hype, but I bought film caps as opposed to electrolytics)
• Huge sheet of MDF £30 (used only for making new baffles)
• 3 x Denon amps £130-ish
• Software £0 (I wrote it, but there are open source convolution engines out there, or commercial packages for £40 upwards)
• Cables £30-ish

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Total: £418

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UPDATE 04.03.16

I have changed the hardware and software a bit (although probably with zero change in the sound). The following items have been substituted for the corresponding ones above:

• Sumvision Cyclone fanless PC instead of the Dell desktop £100
• Sony AV amp instead of the three Denon amps £170
• Xonar U7 USB-based sound card in stead of the two PCI cards above £90

Christmas Lectures, then and now

How the Christmas Lectures looked in 1988

I watched the first of this year’s Royal Institution Christmas Lectures today. The theme was ‘How to hack your home’, explaining how it is possible to approach any engineering problem and break it down into simpler elements, culminating in turning a real London skyscraper into a giant game of Tetris (a wi-fi controlled LED lamp in each window – you get the picture). The lecture made great use of small microcontroller boards with ethernet connectivity and scripting languages to turn lamps on and off, trigger cameras and so on. It all seems quite reminiscent of the 1980s BBC Micro initiative where a generation of schoolkids was introduced to writing computer software. The perception is that this was a great success at the time but that in the intervening couple of decades it was forgotten and we subsequently taught kids to use Microsoft Office really well, but not to write software. I think there is a movement to get the kids interested in software again.

One thing I hate about this year’s Christmas Lectures is that they have decided that having a lecturer stand behind a desk or bench is just too elitist or formal for the kids to take these days, so the lecturer should be like a modern politician and speak without notes while wandering about. I don’t like it at all. If the idea is that knowledge and education is all about building on what has gone before, then it is completely natural that a significant part of any lecture is in the form of references to texts, or objects, or pieces of apparatus, all of which may be accessed quite conveniently when placed on a large flat surface.

I thought I would have a look at at some previous years’ lectures on Youtube, as a comparison. The first one I happened to stumble upon may be of interest to audiophiles. This 1988 lecture deals with the history of entertainment in the home, starting with musical boxes then pianolas, wax cylinders, 78s, LPs, crystal sets, valve radios, wire recorders, reel-to-reel, the compact cassette, mechanical television, and ending with the then future of high definition television, flat screens and 3D. Vinyl enthusiasts are allowed a wry chuckle at the claim that

…in 10 or 15 years we will probably have lost the LP for good

Is the hi-fi industry in safe hands (and does it matter anyway) ?

This is the post that I was thinking of when I came up with this blog’s tag-line. Could the hobby of hi-fi actually destroy itself by willfully wandering off into pointless blind alleys? And could the smaller players in the industry lose access to the digital audio stream?

Anyone can become an expert

Around the web, on the subject of hi-fi as with any other subject, there are experts galore, all offering the benefit of their wisdom and experience, stated with absolute solemnity and authority. I have to say that I question just about all of it, fuelled by a large element of ‘It takes one to know one’. That is, despite 30-odd years of messing around with this stuff, and being of a technical bent, I am all too aware of the vast, gaping holes in my own knowledge, and I assume that many self-proclaimed experts are in an even worse position.

My strongest doubts are reserved for the implicit assumption that if a person is called an expert, they must therefore possess special insights regarding the bigger picture, even if their expertise is newly-formed in some narrow field.

Obviously 90% of all hi-fi customers will know very little about the subject, and so it is easy for anyone with the ability to plug together the basic components of a hi-fi system to claim, or to be accorded, the status of ‘expert’. Various other special skills can be acquired through repeated, or on-the-job, experience like positioning speakers, plugging in mains filters, fitting carpet spikes, cleaning records, utilising cable lifters, de-magnetising things, and freezing CDs etc. etc. all without any knowledge of physics, acoustics or electronics. Yet the skilled person can still impart his wisdom, combined with conscious or unconscious use of the placebo effect, to impress the 90% and/or to sell them stuff. And it is only a small step from being a salesman of ‘tweaks’ to becoming a manufacturer of ‘tweaks’ (audiophile cables, cable lifters, isolation feet and so on) again with virtually no knowledge of anything fundamental like physics. The ‘knowledge’ is stated with the same sincerity and conviction as an electronics engineer describing how to design a low distortion amplifier. It is clear that there are few people in the audio business who would be able to distinguish between even these two vastly different levels of expertise, so the designers of ‘audiophile cables’, and amplifiers, carry equal influence and are accorded similar degrees of respect.

There are experts and experts

Which brings me on to the meaning of expertise when a person does have some knowledge of acoustics, physics or electronics. Qualifications in electronics do not confer any special insights into acoustics, or into the advantages of active over passive speakers, or the true consequences of a poor damping factor. An ‘expert’ in electronics could dive straight in and start employing their skills and qualifications to design passive speakers or valve amplifiers – and start their own company and be interviewed in magazines about it – without even considering the alternatives, and I am sure this happens. Many of the more subtle aspects of audio design fall into the gaps between academic subjects, but generalists who might be able to see the bigger picture and who might care enough about it are few and far between.

Even a celebrated physicist like Professor Brian Cox could fall into the trap of assuming that valves (despite their high output impedance and high energy consumption to name but two drawbacks) are somehow superior to solid state. Or that vinyl somehow confers a magical musicality that digital does not. (He gets his retaliation in first by invoking the “retro” word, but surely a retro enthusiast would be showing off genuine vintage gear rather than some modern things with blue LEDs and a brand new record player..?). I would love to have a conversation with Professor Cox about why he chose to spend £5750 on a modern valve amp with the heady output power of 18W, and particularly what cables he uses, and why! He presumably trusts the expertise of the ‘physicists’ who designed the amps. So did he give the amps the recommended 2-3 weeks of burn-in for 6-8 hours a day, when new? Did they sound better afterwards? Does he let them warm up for an hour before listening to them? Can he hear the musicality of the silver wire inside? Has he ever seen or heard of a piece of lab equipment with similar characteristics in the many leading research establishments he has known? That is, how many scientific discoveries has he missed simply because he didn’t think to use silver wires and valve technology for measurements, and a variable speed cutting machine for recording signals, in the lab? In an audio-related discussion, Professor Cox would be by far the most highly-qualified participant in terms of ‘the bigger picture’, but it is clear that his views are swayed by some sort of romantic notions about the magical properties of valves and vinyl. Many of the subtleties of audio design may not be immediately apparent, even to a physicist.

And of course, all the while, the most fundamental flaw in audio ‘expertise’ is all around us: subjectivity. So many audio experts whose entire repertoires are based only on listening to stuff. It is hardly worth repeating all the problems with this. The experts are probably able to list the problems too, but with an implicit disclaimer that because they’ve been doing it for so long they are immune to expectation bias etc. I strongly suspect that, in reality, the most experienced audio professional in any field would not be able to reliably distinguish between all audio phenomena relating to source/amp/speaker design defects, faulty hardware or psychological biases simply by listening. Experts’ opinions (e.g. on the efficacy of high resolution sampling) based solely on listening are meaningless, in my opinion.

No sense of progress

Compared to computer graphics and video, say, audio has a non-academic, cottage industry, or corporate after-thought, feel to it. It does not feel as though there are university departments all over the world forging ahead with brilliant new discoveries, or large corporations pushing at the boundaries to achieve the highest performance at the lowest cost. Instead, it is in the hands of small private companies who are re-hashing the ideas of the past in order to sell small numbers of very expensive boxes, or if the large corporations take an interest, it is in plumbing the lowest depths in order to shift large numbers of very cheap boxes.

So I find myself without many audio ‘heroes’. I might have been in awe of Peter Walker of Quad, or the founders of Meridian, KEF and other great companies, but even in my profound ignorance on many issues, I still have reservations about their ideas on the bigger picture and exactly how they are influenced by commercial considerations. A particular charismatic industry leader may promote high resolution sampling as the next frontier, while I may think of it as a red herring and a sideshow. Do they really believe what they are saying? Are their motives completely pure?

It just feels as though the industry and hobby are blowing around in the wind rather than ‘in safe hands’. It is by no means clear to me that there is progress towards, or in existence already, an audio system that is quite simply the best that can be. Nor that there is a continuum of audio systems that can be ranked in terms of performance and that might be loosely related to price, thereby allowing customers to influence the industry in a rational way by voting with their pounds and dollars. It feels as though the whole ‘hi-fi’ thing could drift off into an oblivion of all-in-one boxes and soundbars, headphones, home theatre, faux vintage toys, and astronomically-priced, over-engineered and fundamentally-flawed bling.

But maybe none of this matters, and for someone like me, as long as there are enough secondhand bits and pieces on eBay to cobble together something passable then there’s nothing to worry about. And new innovative companies and individuals could spring up at any time and continue forging ahead with audio’s absolute progress in the future. Possibly, but as a subject for another post perhaps, there is also a sense that nothing in the IT-related world is permanent. In order to create new innovations in DSP-based audio, access to the unencrypted digital audio stream is required. But will it always be accessible? There’s no problem at the moment, but operating systems are continuously upgraded; drivers are updated; interfaces are removed. For example, various mechanisms are already in place in the Windows operating system to prevent access to the digital audio stream, except for companies willing to meet onerous conditions. External hardware interfaces carrying unencrypted audio can simply be disabled.

Some output types such as S/PDIF typically don’t have a suitable DRM scheme available, so these need to be turned off reliably if the content so specifies.

Software must be approved by Microsoft, acting on behalf of Digital Rights Management (DRM) licensors:

Welcome to the world of … the Protected Media Path, where Microsoft, copyright holders, and DRM licensors may grant or revoke permission to use your own computer and digital media.

…this functionality is known as “selectable output control”; it gives software and encrypted media increased power to intentionally break compatibility in obsolete already-purchased equipment.

…Components that are loaded into the Protected Environment by the Windows kernel must be signed and authenticated; software developers must also have produced them pursuant to a license with Microsoft, and their developers must have committed to follow certain policies that Microsoft promulgates.

At the moment it seems unlikely that such systems would be activated for audio, but these kinds of restrictions could be enforced in future if a new, exciting digital format came along, seducing the audio and music industries, and the public into abandoning their existing ‘open’ digital audio systems, and if future high quality digital music releases became restricted to this format.

So can an individual or small company be sure that they will always be able to develop their own unique digital-based audio system that is compatible with the latest high quality music releases? Not necessarily. Might our future choices be between playing at vintage technology with vinyl, or streaming directly into a limited choice of licensed hardware and software?

The audio system that never changes. An impossibility?

Although I have made no hardware changes to my audio system in over 18 months, I occasionally make small changes to the DSP configuration: crossover frequencies, slopes etc. I don’t expect to hear any huge transformation in the sound, but I have an idea that by making these changes it has almost the same effect as moving the speakers slightly, or changing the room furnishings, or even fitting new drivers. In other words, keeping the sound fresh to my ears. Maybe placebo, maybe not.

Standard audiophile lore would suggest that somewhere out there is true perfection, or at least a true optimum, that can be found if only the audiophile spends long enough looking, and spends enough money. I think a more realistic view is that apart from an anechoic chamber, any system/room combination has certain characteristics that can at first sound fresh to the listener’s ears, but which eventually become over-familiar. I would hope that by starting with a ‘straight’ system in terms of linearity, damping, phase distortion and crossover accuracy, we automatically get closer to optimum than we otherwise could. But it seems logical that what quirks and idiosyncrasies do remain will be constant and may eventually become wearing on the ears, just as listening to live musicians playing in a particular room for hour after hour, day after day from the same seat would tend to over-emphasise certain aspects of the room’s acoustics (and house PA).

The user of a multi-driver speaker with DSP has an advantage, I think, in that a subtle change to the crossover frequencies and slopes may have very little effect in theory, but in practice will change the speaker’s interaction with the room in subtle time domain-related ways – not simply like adjusting a tone control. We may shift the average vertical position at which a certain frequency range is emitted by the speaker, or affect how two drivers with differing dispersion angles blend together. Other aspects that will be affected include the excitation of any breakup tendencies in the driver cones at certain frequencies, and the contribution of doppler distortion. No single setup will ever be optimal in all areas and with DSP we don’t have to settle on a particular setup forever.

I recently made a small adjustment to the depth of my speakers’ baffle step compensation curves. It seems to me that there is a significant audible difference* between curves that are only 1 dB different. In this case, 5 dB seemed somewhat lacking in top end while 4 dB was too far the opposite way. I settled on 4.5 dB.

With such subtle differences being audible*, I began wondering about the magnitude of effects due to temperature and humidity. There’s an online calculator for absorption of sound by the atmosphere. It may be surprising to learn that at 14 kHz, for example, in typical indoor conditions, the attenuation of sound varies between about 0.2 dB/m and 0.4 dB/m, while at lower frequencies the attenuation is negligible. So if I am interpreting this correctly (and please, do correct me if I am wrong), by listening at 3m from the speakers we could effectively have variations of 0.6 dB of treble attenuation on the direct sound, dependent on the season and use of heating, air conditioning and so on. Furthermore, the reflected sound would vary even more heavily, so I don’t think this effect is negligible by any means. Such variations are presumably more significant than might be encountered by changing cables and other audiophile tweakery.

(Which speaker system will be the first to include sensors for atmospheric temperature and humidity..?!)

All of which brings me to the main point: there are very few things that a conventional audiophile can do to keep the sound of their system ‘fresh’ by deliberately introducing subtle variations, or to compensate for unwanted changes in treble response due to the atmosphere or their ears. The chances of their achieving anything like the optimal setup in the first place are remote. If I am right, and variations in broad EQ of less than 0.5 dB can cause audible problems, then it seems to me that the ability to adjust the system via DSP is vital to avoid frustration, expense and never-ending equipment ‘churn’.

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UPDATE 04/01/15: Here is an account of an apparently-small difference in treble balance being found to be significant audibly:

…The Salon2 has a level switch for the tweeter that operates in 0.5dB steps, and it turned out that the optimal treble balance would have been between two of those steps. With the switch affecting the entire range covered by the tweeter, a level difference of just 0.25dB turned out to be significant.

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* The usual caveats apply to such subjective statements.

Devialet Phantom

I saw this on Computer Audiophile via Ultimist.

Fascinating to say the least. Here is a 6 litre sealed enclosure speaker reminiscent in appearance of the Dyson school of design, capable of high sound levels down to very low frequencies (16Hz). It contains all the amps, DAC, DSP and so on to make a complete mono three way active speaker.

There is something counter-intuitive about a small box capable of such feats… and sure enough, I think a price has to be paid. I remember reading a very interesting article on building an Extended Low Frequency subwoofer which describes housing a driver in a small sealed enclosure and operating it entirely below resonance, using electronic EQ to flatten the frequency response. Being a sealed enclosure it rolls off at 12dB per octave, and so in this particular example, the smaller system with higher resonant frequency, requires about 16 times as much power to produce the same SPL at 30Hz, say, as would be required for a conventional larger enclosure. In other words, there is no such thing as a free lunch, and in order to save some space in the living room, much coal, oil and gas must be burned, or nuclear waste generated at the power station when playing very loud.

Maybe the Devialet Phantom is the ultimate manifestation of this idea. The white paper makes interesting reading.

…PHANTOM speaker drivers need to be able to create and resist extremely high pressure and vacuum inside the speaker box. We tried to use in the early prototypes the most robust loudspeakers we could find in the market, and the speaker drivers seemed to ‘implode’: the diaphragm fragmented itself into fractal shapes, sucked in by the excessive force resisting the speaker’s intended displacement.

Two versions are available: one with 750W of amplification and one with 3000W – a figure that becomes a positive marketing advantage: people don’t ask how loud the unit goes, they just know that it “goes to 3000W”. Presumably the DSP controller can intelligently limit the power for thermal protection if necessary (reducing the low bass content without affecting the remainder etc.). There seem to be stands available which also act as heatsinks.

An extremely nifty feature seems to be the ability for Phantoms to be synchronised in stereo pairs or surround/multi-room arrays of up to 24 units, all over a wireless connection.

I would certainly love to hear this. It must be very strange to hear and feel clean bass down to infrasonic frequencies coming from such a small box.

Paul Morley: ‘Pop music needs a cull’

Podcast from Spiked Online. PM’s views on there being too much music criticism, too much music; If everyone is communicating then no one is communicating; The vinyl revival is an empty re-animation of a “dead art form”; Classical music fits well into the world of downloading, but popular music needs context and a back-story or it loses its meaning.

High End speaker styling: the Space Invaders look

I keep noticing high end speakers that wouldn’t look out of place in an amusement arcade or dodgy sci fi film from the 1980s.

An autonomous killing machine from the future placed in a genteel living room is laugh out loud funny… isn’t it?

Do measurements always tell the whole story?

In audio forums there is usually a clear dividing line between ‘subjectivists’ and ‘objectivists’, with the objectivists maintaining that measurements can tell us all we need to know. In audio magazines, subjective opinions in reviews are sometimes supplemented with objective measurement results. But are measurements always meaningful? It seems to me that there is at least one area where this may not be true, and only a rational approach can explain what’s going on.

We all know that most speakers are necessarily made from several drive units, each of which covers a narrow part of the audio spectrum. The crossover filter is designed to split the high power signal on the basis of frequency, and divert the appropriate components to the appropriate drivers. This can be done in several ways. What may seem surprising is that even though the overall system can be designed to have an apparently-flat frequency response with low distortion, this may only be valid for steady-state sine waves, and it does not automatically translate into perfect performance for real music.

The areas that I find particularly fascinating (because no one in the audio business seems to question them) are:

• bass reflex
• arbitrary manipulation of the phase response

These are tricks that enable speaker designers to achieve the perfect overall frequency response using nothing more than nature’s own pure, organic components like coils of wire, waxed paper and glue, but which have the potential to do very strange things to the sound.

I have listed some of the strange things that bass reflex speakers do, before. Now I am straying into more areas of ‘the craft’ that I have avoided serving an apprenticeship in, and would appreciate any comments that could provide authoritative information. But my suggestion is that there are sonic peculiarities in speakers that most audiophiles – and even some designers I would bet – are not aware of. The mantra “phase doesn’t matter” allows a designer to pull any trick he likes in order to get a flat frequency response, as measured with sine waves. For a dissenting view, though, I can do no better than refer you to a possibly-unique speaker review. The writer goes into incredible detail about the audible effects of a particular crossover. Just one of several sonic peculiarities is described thus:

“… our human hearing could perceive and assess the Tamino as having a very severe hole or dropout in its tonal balance, in this critical band of the midrange. Note that a conventional sine wave or FFT measurement of the Tamino’s frequency response would not show this cancellation…”

– and this is a speaker he likes!

As far as I can work out, most multi-driver speakers must be subject to these kinds of sonic peculiarities regardless of the apparent perfection of their measurements. Different types of sound will be affected in different ways, transients being affected differently to steady tones. So while one musical phrase or sound may highlight complex anomalies that are reminiscent of a recessed mid range (for example), the next sound may not – and attempting to fix the problem with basic EQ either internal or external to the speaker cannot work. Needless to say, the errors are fundamental, and cannot be corrected by upgrading to a better quality of waxed paper and wire coils. Nor drivers. Nor $10,000 speaker cables.

The DSP active speaker with phase correction, on the other hand, simply tries to avoid all this stuff, and I think you can hear it; the sound is solid and coherent from top to bottom.

If what I am suggesting is true, I think it explains an awful lot!

Meridian MQA

While I was listening to possibly-defective high-priced systems yesterday, a DSP-oriented firm, Meridian, was busy launching its groundbreaking audio compression system that promises to deliver high resolution streaming in CD-sized files. All the theory and practice suggests that CD is already transparent, so this sounds similar to a question I have asked myself when archiving photographs: given that storage space is limited, would I be better saving uncompressed at, say, an already-acceptable 1920×1080, or compressing ultra-res 4000×2000 into the same file size? I think the sensible answer has got to be the latter. Anyway, Meridian can’t really lose, as even if there is no audible difference, high res scores higher on placebo points.

But selling is a dirty business isn’t it? They provide this ‘graph’ that actually undermines everything they have been commending to us for years. Analogue reel-to-reel (the audio bottleneck that digital was originally developed to fix) is placed as highest quality, and even the humble 1940s consumer distribution medium, LP, is placed higher than DVD-A. In fact, given that DVD-A can play back the highest resolution uncompressed studio formats already, this graph even undermines what they are trying to sell now. Unless the hope is that the consumer infers that MQA is a technology apart and is better than all the options shown. On that basis they might hope to snare the analogue-o-philes as well as digital people.

But can they cite any real evidence that the above ‘graph’ has any basis in reality? Maybe they meant it to be ‘quality as popularly-mythologised’ but didn’t have room for the extra words.

High End Disappointment

Well this was interesting. I booked into a very high end dealer’s showroom for a detailed listen to one of the DSP-active products that I have mentioned in these pages, plus a presentation by the manufacturer. We are talking the price of a grand piano, a house extension, or a very nice car. Basically, my aim in going was to understand a little bit more of what I’m writing about, and to confirm that DSP active systems are indeed the bee’s knees. (And also, I am not immune to the pleasure of gawping at ultra-expensive stuff in a luxurious showroom – and it really was a very, very nice showroom).

The medium-to-large demo room was a fairly standard rectangular shape with a sofa towards one end, carpeted with plasterboard walls and ceiling and a small amount of ‘acoustic treatment’. The speakers were located reasonably well away from any walls without any toeing-in. There was an audience of about seven or eight of us.

The representative launched straight into playing ‘audiophile music’ and I could tell immediately that some listeners were not altogether impressed. The sound, to my ears, was ‘boxy’ with a very peaky, congested mid range, and little deep bass. The representative turned it up quite loud (much louder than a girl-and-guitar would be in real life) and it was not impressive – I might have expected a similar sound from one of those compact systems you can buy in the electrical sections of supermarkets. There were a couple of vinyl-and-valve afficionados there, and I got the feeling they were quietly triumphant, as this proved what they knew all along.

I spied on the representative’s laptop that the system had been configured with what looked like quite strong room correction and I became convinced that this was the problem, thinking “Aha, there’s the problem. Once he turns that off, people are going to be astounded.” He duly did turn the correction off but the audible difference was relatively subtle – it sounded poor with, or without. I listened carefully, and not only did there seem to be a problem with the ‘EQ’, but there seemed to be nothing in the way of stereo imaging either – I couldn’t locate where any particular sound was supposed to be emanating from.

The source was switched from the slightly unreliable digital (“server problems”) to vinyl. A completely fresh LP was taken from its cellophane wrapping and placed on a well-regarded brand of record deck. It sounded very similar to the digital except for some very loud crackles and pops during one track.

So what was the problem? The company representative didn’t seem to notice that there was anything wrong with the sound (or he hid his doubts well), but I am pretty sure that the listeners were not impressed.

I went out into the shop’s main foyer and had a quick listen to an £82,000 (yes, really) streamer/amp/passive speaker system which comprised the largest speakers you’ve seen in your life (yet still bass reflex – why?) and a large stack of purposeful-looking boxes on a rack, with as many power supplies as functional boxes; £2000 here, £4000 there. Amazingly, in this day and age, there was a loud ‘crack’ from the speakers when the power was applied to one box while others were already on; maybe one of the hazards of multi-box systems. We turned the volume up fairly high, and again the sound didn’t seem all that impressive – you wouldn’t have known you weren’t listening to smaller floorstanders – and I thought that the drivers didn’t blend together well. However, in this case, the listening environment was definitely not ideal and we should have been standing further away from the speakers. Even so, I was hoping for a sense of something amazing. I didn’t get it.

As so often happens with my encounters with the world of ‘real’ hi fi, I am left bewildered. I am sure that there’s a lot of fine tuning that can be done in the speaker positioning and room layout, and you can’t dismiss the psychological aspects of expectation bias, what mood you’re in, how your ears have become accustomed to your existing system, and so on. Maybe on another day I might have heard something different. But I can’t help but think that something has been lost somewhere along the way; I think that there used to be an unmistakable richness that came from large sealed speakers, even if you just heard a brief burst in a shop. There were problems, too, but what I am hearing these days just doesn’t seem as good. In the case of today’s DSP active system, I think it was just plain wrong.

Of course I am undermining my thesis that DSP active systems are the way of the future, but I think that if they are loaded up with the wrong crossover files, or some other drastic problem then all bets are off. What struck me was how one bad experience could easily put you off a particular brand, or type of system, or type of room. I have no doubt that some of yesterday’s audience went away with reinforced beliefs that DSP/digital/solid state sounds bad. I am left wondering whether in my proposed house extension I should be insisting on directly-plastered walls rather than dry lining, just in case.

(My own £380 system is still easily the best I have heard so far. I genuinely wanted that not to be the case with yesterday’s listening session, so that it might show me what I am missing and inspire me to replace my £9 mid-frequency drivers with something better – but after a year and a half I still feel no need to change anything.)