Know How

Ivo Rozehnal has specialized for nearly two decades in audiophile room voicing and room correction as an independent consultant.

In an interview below provides answers how it should be done in the 21st century:

Room voicing, equalization or DRC (digital room correction), are in high-end audio the subject of controversy, even rejection as something inferior...

… and “completely unworthy of a renowned high-end system and experienced listener” 🙂 ... Yet nothing could be further from the truth than the fact that for a top-class audio experience it is necessary to optimize the entire chain recording-electronics-speakers-room for the specific situation and taste of the listener. While today at least some acoustic treatment is taken for granted for high-end stereo systems (finally after years!), and likewise at least a basic awareness of loudspeaker placement and listening position is considered obvious, the field of room correction (equalization, DRC...) is for some reason completely neglected. At the same time, calibration of both picture and sound for top-class home cinemas around the world is an absolute standard for achieving top-level results… only for hi-fi high-end stereo are we still in the Stone Age...

What can be improved? Do you focus only on solving bass?

Everything is connected with everything else. Bass does not live by itself on a deserted island - it is part of the whole - therefore it is necessary not only to help with room modes (minimize booming), but to properly connect everything through the critical Schroeder region towards the mids and highs, which can also be suitably adjusted - even things that the loudspeaker designer intentionally left uncorrected (whether due to incompetence, or as a company sound signature, or simply because in a passive loudspeaker it is very difficult to correct and if he attempted it, it would be counterproductive - it would damage sound quality elsewhere or would be prohibitively expensive).

So does this mean another box, more cables, more synergy issues, or whether it will "fit" into the system?

Not at all! Some streaming or integration services (for example Roon), or streamers or DACs today already provide sufficient functionality for quite advanced adjustments and corrections. Now it is only necessary to use this functionality properly for a massive improvement of the listening experience. It is always a matter of discussion with the potential client, what he has in the system, or what would have to be changed. The advantage of an independent consultant is that he works with the entire portfolio of tools that are used and is not interested in promoting and selling a specific box or software.

So can everyone do the adjustment themselves?

Of course! Anyone can tile a bathroom themselves as well, even if they have absolutely no experience or practice, let alone skill. If the final result is supposed to be high-end , there is no alternative but to leave it to people who have devoted years to such activity and have the competence for it. And in hi-fi it is exactly the same. There are software as well as hardware tools which make it possible in an almost automatic way and at various levels of sophistication to create correction curves and play through them, however the whole thing is often based on the fact that these tools are simplified so that ordinary laymen can operate them and conveniently achieve some kind of result.

It "does something somehow", the user clicks something, tries something, the result at first listening is very catchy, but after several minutes or tens of minutes it stops being enjoyable to listen to, or listening fatigue immediately appears due to the sterile or shouty sound after correction, and the user often returns to the original state (without correction). This story runs like a red thread through the part of the hi-fi industry that has "somehow" tried room correction adjustments. And the others are even worse off. They try to improve the sound of their hi-fi system in various ways... and leave this area completely untouched. Yet it is an area where points can be scored effectively, to use sports terminology.

Is this the famous Harman curve for loudspeakers?

Yes, for example. The gentlemen from Harman woke up many years ago and suddenly became interested in how real hi-fi actually performs in real rooms at home - and the results naturally looked miserable - at that time de facto without acoustic treatment, without any optimization whatsoever. And based on these measurements they then created an "average" - a typical frequency response - of how systems play for people. And from the average of the current unfortunate situation there became the famous industry standard, which therefore must be taken as a recommendation and not holy scripture through which no train passes. Already the way in which I measure and average frequency response in the room significantly influences how the as-is state is displayed, and a dogmatic approximation to some curve without listening gives problematic results. Above all, one must listen. Measurement is a wonderful helper.

And what about fans of analog and vinyl listeners?

There are two basic ways to approach this:Purely analog - using top-class studio analog parametric equalizers (which are inserted into the signal path) and on them, based on measurement and careful listening, an adjustment of the frequency characteristic is set. Again, do not imagine classic graphic equalizers from tower systems or mini systems from the 1980s and 1990s with terrible sound quality. At present, top-class analog studio parametric equalizers have remarkably excellent transparency, however compared to digital solutions they are limited by what can be implemented in analog into these equalizers and subsequently adjusted, and for a top- level result in some cases this may not be sufficient.

Or digitally - here it depends on how much analog enthusiasts are in principle willing to admit that something digital would be inserted into the signal path of their polished analog chain. Listening without prejudice is what decides.What if the client likes certain sonic signatures?All these things need to be understood in advance: what kind of hi- fi listening history the client has, what he prefers, and what he does not like, what he notices while listening, what and how loudly he listens, how long and how often, in short to get to know the client and his hi-fi gear so that the resulting perfection using equalization - room voicing- is as close as possible to the client's expectations - for example because he is very sensitive to excess higher frequencies and therefore prefers at almost any cost a smoother presentation of the system. Or vice versa.It is also demanding on the electronics and loudspeakers themselves. In the case of larger corrections into plus (boosting), for example in the bass, one must be extremely careful so that the components and loudspeaker drivers can handle it in terms of power and so that limiting or distortion does not occur, or God forbid damage. And then comes the phase of initial listening at the client's place - without prejudice - the first impression is enormously important. And then measurement.

What and how do you measure?

I use a sophisticated methodology which I refined for years so that it effectively achieves results. It is a set of many measurements, by various methods (different measuring signals), with calibrated microphones in different places (not only the listening position). The point is that each type of measurement and their averaging gives slightly different results about what is happening between the loudspeakers and the room and listener. The point is not to boast with graphs on hi-fi forums, the point is to have solid information as a basis for deciding where and what to improve, or where to minimize problems - what is disturbing. And the human ear (or rather the ears-brain) is in this respect bizarrely tricky - while listening we perceive a problem somewhere (a particular frequency band), but in the end the problem is completely elsewhere and even in two other places. With experience and practice during the nearly two decades I have devoted to this, of course one can learn many things and quite accurately estimate even by ear, but measurement is irreplaceable for an effective and correct result.

Likewise it is necessary to understand what measurement does not tell, what is a matter of interpretation, what is a gray zone and what is already a matter of individual taste and above all what is counterproductive to correct. And this is absolutely the most fundamental thing - and no automatic system will do it for you, AI is not that far and never will be. This requires decades of listening training and practice and the correct decisions regarding adjustments on site for the given individual client situation.

Very often it is very thin ice - when on paper (on the monitor) something looks terrible, in reality it is without issue, and on the other hand ultimate voicing requires fine adjustment by ear in tenths of a decibel.

One of the greatest misfortunes of the audio industry is that "The measurements" have often become a caricature of themselves, placing themselves into the role of arbiter in something that for the final listening quality result is important only partially or even marginally, while completely overlooking many other areas, especially how a real audio system with real loudspeakers behaves in a real room (in situ) and what can be done to improve the sound of a system to a jaw dropping moment.

I heard that you listen almost exclusively to classical music, so how does it work for other genres?

I have an intensive practice of more than 30 years as a listener ofclassical music through hi-fi equipment, certainly more than 600 attended concerts not only domestically but also throughout Europe (Vienna, London, Amsterdam...) as well as some experience with recording classical music as a sound engineer. And this listening training together with nearly twenty years of practice in adjustment and voicing using DRC and EQ gives me certain prerequisites to be relatively effective in recognizing what can be improved on a particular system and loudspeakers in a given room. Trying to determine something by ear on genres about which I know very little does not make sense for my work. So after the adjustments I arrive at the point where orchestral classical music plays significantly better on the given system - one of the most difficult challenges for hi-fi. And then it is about playing some rock, jazz and pop there to see whether the result is correct, or rather the most important thing - to play what the client listens to. In the vast majority of cases it is not necessary to significantly alter the corrections themselves, nevertheless for clients with broad musical tastes the job may also include the creation of several separate presets for certain groups of recordings which are exceptional - whether it is contemporary productions with DR4 or DR5 or, on the contrary, historical recordings such as digital transfers of mono shellac records from the 1940s.

Many customers expect a plug & play quick result, how long does the whole process take?

It is not immediate. Some time is required for preparatory work -understanding the client and system, in what space, what he listens to and, in the case of geographically more distant locations, planning the travel logistics. And then it is usually a matter of several long days in situ at the client's place listening, measuring and adjusting. Then of course there always comes the best part of the whole process. Watching the expression on clients' faces when they play their own music - that amazement and enormous joy at how their often very expensive and carefully refined system suddenly plays in a way they have never experienced before. And appetite grows with eating. Therefore some kind of online follow-up is also part of the process, where perhaps some small details are adjusted, where the client was uncertain or likes a certain correction variant more or less. It takes time.

And your final argument for room voicing and corrections?

The point is that today there are possibilities to fundamentally improve the sound quality produced even by very expensive high- end systems, and these possibilities are not used at all in practice, and if they are, they often lead to poor results, which leads to further rejection of these possibilities to significantly improve the listening enjoyment. And that is what I am trying to change. Room voicing and room corrections make sense. The results speak for themselves. Proof is in the pudding. When two people do the same thing, it is not the same thing. We are in the 21st century.