-  how to properly integrate a sub-woofer into a hi-fi system and ... more

           -  don’t look for perfect sound where it can’t be found

           -  problems of speakers positioned in an asymmetric room

           -  how to evaluate hi-end CD players

           -  balanced or unbalanced interconnections?          

           -  the ACE-bass technology

           -  about hi-fi magazines

           -  serious corner

           -  comedy corner



        how to properly integrate a sub-woofer into a hi-fi system and ... more

I would like to start this “brief” dissertation on systems with sub-woofers by quoting word for word what audio pro states on the first page of an old brochure: “everyone needs a sub-woofer”.  I think that this strong assertion is still topical and should appear in a possible “hi-fi bible”, however, in my view, with a tiny but essential adjustment: “everyone needs an  audio pro sub-woofer”.

Generally speaking, I highly recommend the use of a top quality sub-woofer with any type of speakers. In fact, Audiophiles often forget, or just do not know, that, by definition, a hi-fi system must reproduce frequencies across the audible range, from 20Hz to 20kHz ±3dB.  So, if you want to use the term “hi-fi” for your sound system, you must have a dedicated sub-bass speaker, as NO traditional full-range speaker can deliver decent infra-bass.

A quality active sub-woofer (perfectly set up and tuned into the system) is essential if you would like your hi-fi to reproduce a bass drum or an organ as perfectly and as accurately as it does a violin or a piano.  Bass instruments do not deserve to be considered “ugly ducklings” – they are the foundation, and hence, an essential part of a musical composition or, indeed, of any sonic event!

Many “esoteric” Audiophiles believe (or were told) that the addition of a sub-woofer will muddy the sound of a “high-end” system, and I have to say they are very often right!  But this happens for two main reasons: the first is wrong or very poor integration of the sub-woofer into the system, so that “booming” bass from the pair of main speakers is made worse by the sub-woofer’s additional output. The second reason is that the large majority of the sub-woofers around (or rather, almost all) do not have acceptable sound-accuracy, because they don’t avail themselves of advanced electronic technologies.

A traditional sub-woofer, simply made up of a normal amplifier and a woofer (quite often tragically larger than 10"), is something to deliberately avoid in a serious hi-fi environment! The inevitable result, due to the high distortion and lack of control (no matter the crazy price, the “noble” brand or the astonishing opinion of pathetic reviewers), is a sub-woofer affected by so called “slam” or “punch”, that is a nasty thing for demanding Audiophiles who are looking for a genuine infra-bass, but very enjoyable for young guys and car-audio lovers, who think that real bass is just a matter of “boom, boom”; so, these items actually deserve to be called “boom boxes”.

To compound the problem, when you buy a sub-woofer it is more than likely that you will not be instructed in the correct way to integrate it into your system, so people instinctively connect the sub-woofer in parallel with the main speakers and unwittingly commit a real “setup crime”. Finally, to sum up, all these negative factors combine to result in a disgusting bass range!

With audio pro sub-woofers, thanks to their patented ACE-bass technology, it is quite another story and, with the help of this instruction, you can achieve a perfect setup of your system, resulting in a fantastic bass & infra-bass range, with the additional benefit of a cleaner mid-high too.

Anyway, you may be interested to know that in 1978 audio pro produced the very first active (and ACE-bass patented) sub-woofer in the world – the legendary B2-50 – which, after 37 years of service (that's the only case in hi-fi history), is still delighting the ears of thousands of audiophiles around the world, and I’m absolutely thrilled and proud to be one of them!  Amazingly, in spite of its longevity, the B2-50 still sets standards that other sub-woofer manufacturers nowadays try in vain to match!

Now I would like to give you some important advice on how to set up for best results a system with a subwoofer.  A perfect and right setup is essential, as the quality of the sound of your entire system will largely depend on it. Please note that the following instructions are valid for any subwoofer on the market and not only for audio pro subs, but do not expect to achieve a perfect midbass- bass-infrabass if your sub(s) and speakers belong to the hopeless ones, sorry.

To begin, position the speakers and the sub-woofer following these directions:

1) if possible, situate the speakers and the sub(s) facing the long side of the room, with the speakers (if boomy floorstanders) at least 1 metre (more is better) from the corners and back wall. Do not place the speakers and/or the sub inside an item of furniture, such as a cabinet, or in a semi-enclosed space. With small speakers on stands, you can reduce those distances.

2)  always try to put the sub-woofer close to a corner, or at least against a wall, in order to increase its efficiency and consequently to reduce its distortion (for the same sound pressure). Avoid positioning it far away from a wall or, even worse, raising it from floor level.

Anyway, when you introduce a sub-woofer into a hi-fi system, the absolute rule is:  always roll off the deep frequencies in your main speakers, no matter what type they are! This way, you create and achieve a perfect crossover point with the sub-woofer. Furthermore, given that the large majority of speakers (not audio pro) are always “hilly” in the frequency response of the bass range (the cause of “booming” bass), if you apply a roll-off on this range, you manage to subdue this nasty “hill” and consequently to eliminate or at least reduce the "booming".  In the case of small main speakers joined with a sub-woofer, what happens is technically different, but you still have to roll off their bass response, mostly in order to reduce the distortion of their woofers, which is generally high in this type of speakers.

Please note that if you roll-off the lowest frequencies in the main speakers, their dynamic range and “speed” will increase and their total distortion will decline. This happens because the woofers of the speakers will no longer struggle (in vain) to reproduce the low frequencies that the sub-woofer is much better qualified to manage. So, due to the reduced distortion in the bass range, the high order harmonics of the distortion will be reduced consequently and, as a magical gift, the clarity of the mid and high range will improve. The cut off of the deepest frequencies is a joy for any amplifier too (it increases their dynamic and speed, plus reduces their THD), but for tube amps the benefits are so evident that they will thank you for the rest of their life indeed! Finally, due to the “perfect marriage” between the main speakers and the sub-woofer, low frequencies stop “booming & yowling”, and the infra-low ones are deep, fast and undistorted, as if they are “carved out of the air”.

To help you understand what I mean, I’d like to quote the words Scott Bartley used about the “bass department” of an audio pro system with sub-woofer (perfectly set up), in an old review in FFWD magazine: ”bass response is wonderfully tight, incredibly fast and, above all, really deep … to create a distortion-free sub bass effect that feels as though it’s rising up out of the very floor. Call it low-end imaging, if you will”.

In the light of what I have stated in the above lines, is there any Audiophile who still thinks that a serious subwoofer, perfectly set up by a professional, is a noxious addition to a hi-end system? If so, I’m just sad for him!

Now, back to the setup, where you have a stereo amplifier (without a Sub-Out RCA socket and no possibility of cutting the main speakers electronically), the best way to solve the problem is to connect a high quality, non-polarised, capacitor (see the values below) in series to the positive of each speaker. To do that, you'll disconnect the positive wire of the speaker cable from the positive (marked red or +) binding post of the amplifier and now you connect one of the wires of the capacitor into the red binding post of the amplifier and the other wire to the positive wire of the speaker cable (it’s better to solder them together). Do the same for the other speaker.

The value of the capacitors has to be 150μF (100V) if your speakers have a nominal impedance of 4Ω and 300μF (100V) if the impedance is 8Ω. In NZ you can find these capacitors in Jaycar stores and their part numbers are respectively RY-6924 and RY-6932.  Anyway, call us for a better explanation, if you have any doubts.

If, instead, you have a home-theatre receiver, the solution is easier:  whatever type of speakers are being used as main speakers, even if they (tragically) are as huge as a wardrobe, go to the “speaker setup” menu and select for all the speakers (front, centre and rear) the “SMALL SPEAKERS” option, and connect the sub-woofer to the “Sub-Out” RCA socket(s) of the amplifier, using a screened cable (its quality is not important).

Many home-theatre receivers also have the option of selecting the frequency for the cut of the main speakers: if so, be sure to select a roll-off point between 80 and 120Hz (it depends on the quality of the bass department of the main speakers). It is advisable to increase the roll-off point (even higher than 120Hz) in the case of very “booming” floorstanders: by moving up the crossover frequency you usually manage to clean up their bass-mid/bass range. Very simply, using only the main speakers (sub OFF), play a well recorded CD and increase the crossover frequency as far as you achieve a clean bass.

Now you have to set up the low-pass filter frequency of the sub. Normally, (if you cut the speakers at around 100Hz) this knob should be set at 50Hz, but in the case you have chosen a quite high frequency for the roll-off point of your main speakers (see the previous paragraph), you could go higher than 50Hz, but almost never more than 100Hz.

Well, I know what you are thinking right now, but do not worry: if you cut the speakers at 100Hz and the sub’s “Low Pass” knob is set at 50 Hz, you do not create any “hole” in this frequency range, but a perfect -3dB crossover point at around 80Hz, which is the condition for achieving a flat frequency response at the crossover point. It’s too long to explain why right now, but just trust me. However, it is much better to have a small “hole” in the crossover point (inaudible), than a small “hill” (very audible) and furthermore, remember that when you increase the low-pass frequency knob in your sub, you will, consequently, slightly increase its distortion and reduce its dynamic range and this is valid for every sub-woofer in the world.

It's time now to turn the sub on and adjust its level perfectly.  Unfortunately, it’s not likely that you have a spectrum analyser, so here is an empirical method to adjust the infra-bass pressure. With a spectrum analyser it would be an operation of five minutes!

At first, with any kind of amplifier, you must set up the tone controls (if any) to flat and be sure that no filter is active. With home-theatre receivers, you have also to pre-set the system to “stereo mode”. Regarding the tone controls, there is no need for them to exist anymore, but if your amp or receiver has got them, never use them!

Now select a few well-recorded, recent CDs with real infra-bass content (i.e. bass drum or organ). Do not use poor recordings that are void of very deep content and avoid using “disco music” CDs, because they are surely full of awful, saturated mid-bass, but usually devoid of real infra-bass! Be warned that, with this type of poor recordings or with old CDs, people with limited experience usually try to achieve a decent infra-bass - that doesn’t exist in the recording - by continuing to turn up the sub-woofer’s level knob!  You should also note that an audio pro sub-woofer, due to its low distortion and control, does not have the nasty tendency (common amongst normal sub-woofers) to fake a rounded bass, if this is not present in the recording.

So, to do the right thing, you may choose a Telarc CD, as this brand makes top-quality recordings (mostly of classical music). So buy (if you haven’t any) and play a Telarc CD that includes a well-defined bass drum or an organ and simply rotate the sub-woofer “level” knob until you are satisfied with the infra-bass pressure.  If, in order to be happy, you have to turn the knob past “eleven o’ clock”, either there is still something wrong in the setup of your system (check the level of the sub-out in your home-theatre receiver), or you may simply have … bad musical taste and habits!

I STRONGLY recommend that you do not set up your sub-woofer with an excessive level. Be aware that unnatural and over-emphasized bass causes listening fatigue and headaches, not to mention its hiding and dimming of the clarity of the upper audio band!

Anyway, if you have set everything up correctly, but still have a “dirty and/or booming” bass, almost certainly you have to blame the main speakers. The problem never lies with the sub-woofer if it is an audio pro.  Here are a few suggestions:

1) as mentioned above, if you have the option in the amplifier's setup menu, increase (even up to 160Hz, if needed) the crossover frequency for the main speakers and set the “Low Pass” knob of the sub-woofer around half-way or more.  This normally is the exhaustive solution.

2)  if that is not an option, try moving the main speakers further away from the corners of the room and from the back-wall, and reduce the length of the speaker cables, which should always be as short as possible (this is a general must).

3)  finally, try to move the sub-woofer from the corner along the wall.

If the problem persists, you have to blame the acoustics of your room and unfortunately this isn’t rare. In fact, poor quality bass range, and sometimes mid-high too, does not always depend on the system itself. The acoustics of your listening room is essential to build a pure sound. Sometimes, even with a top (and perfectly set up) audio pro system, the dimension, the shape and the reverberation factor of the listening room can mercilessly nullify all the efforts. So, if unlucky, experiment by relocating the system to a different part of the room or in another room: sometimes the result is miraculous!

Be also aware that the frequency of 20Hz has a wavelength of around 17 metres and you cannot physically hear this frequency in a closed room with a diagonal shorter than 8.5 metres!  This practically means that deep bass needs big and open rooms: it cannot expand and “go deep” properly in small closed rooms, but will produce a feeling of saturation and a lack of sound pressure. The shape of the room is very important too, so try to avoid rooms with “cubic” shape. These rooms are natural generators of “standing waves”, which tend to confuse and draw out the bass, killing its clarity.

In all these cases, there is not much that can be done:  you can only try to improve the infra-bass potential of your room by opening doors and, if possible, windows too (please do not laugh, I am very serious)!

You should also note that the pressure, depth and quality of the bass vary a lot around the room, so tune your system for a flat bass response in your habitual listening position. You will also find that just moving your listening point forwards, backwards, up or down, often makes a huge difference!

To finish I would like to say two words about the mid-high range. If you use audio pro main speakers, they have a very balanced and clear mid-high range, but if they don't sound this way (for example, too bright), you probably have a very reflective room, so try to reduce the reverberation by adding rugs, curtains, furniture … or in general things which can absorb and/or break the sound. There is also the possibility that their mid-high sounds too “dull” and in this case you have to increase the reverberation of the room, removing the most absorbent stuff and in extreme cases the carpet too, wife permitting!

For your information, the room that will sound perfectly in the mid-high range is one where human voices, during a normal conversation, sound natural and clear, and, when you clap your hands, you don’t hear any echo and/or reverberation. Anyway, be aware that both the previous opposite situations will only slightly modify, if at all, the infra-bass response of your system, which is 90% determined by the shape and dimensions of the room and the position of your listening point.

However, my final piece of advice to the "esoteric" Audiophiles is: instead of squandering heaps of money in useless, expensive cables and accessories, invest less money in a great sub and call a professional to set it up perfectly. It's like to change the whole system and ... welcome into the real hi-fi world, finally!

I have tried not to use too technical a language and I do hope these recommendations will help you to succeed in setting your system up perfectly, or at least in the best possible way, but if you have serious problems, which you don't manage to solve, please read the "hi-end doctor" page and do not hesitate to contact us.



        don't look for perfect sound where it can't be found

The purpose of the considerations below is to stop Audiophiles throwing away heaps of money in the foolish exercise of expecting to get good sound from very expensive, but hopeless speakers. I know that I’m often wasting my time, but I feel it as a duty, or rather, almost a humanitarian rescue mission, so I must at least try!

As a first consideration, it seems that in the hi-end environment Audiophiles have totally lost their common sense and contact with reality! Did you ever ask yourself how much should your car cost proportionately, if you pay $50k for a pair of speakers? … definitely much more than $50m!

Normally, the most expensive part in a speaker is the cabinet, because the industrial cost of woofers, midranges and tweeters is low; for instance, a top level 10” woofer could cost less than $150. I know that you also have to add on the balance the time the manufacturer has spent in “research”, but the “research” time is exponentially higher in a car design. So, in the light of these considerations, a pair of loudspeakers that cost (unjustifiably) more than $10K are a joke!

The perfect loudspeaker doesn’t exist, but nowadays you can get close enough, if its design is observant of the rules of physics-acoustics and if it’s the best compromise between a multitude of technical parameters and sonic priorities. A speaker like that won’t be necessarily expensive, because there is no reason and remember that is not the price that guarantees the quality, but the technological skill of the designer. The most important thing is to keep things as simple as possible and not to fly in the face of the basic rules of acoustics! You would think that in the hi-end speaker market this were the norm, but I assure you that it isn’t. To let you get the point with an intuitive example, imagine a market of dream-cars where almost all of them (Ferrari, Porsche and Aston Martin, Bugatti etc.) sport hexagonal wheels! You think that I’m exaggerating, but it’s exactly this way!

So, generalising and technically speaking, I’m against the big “dinosaur-speakers” (amicably called "dinos" from now on) and I do prefer a pair of top sounding, 2-way bookshelf speakers along with one (or two) serious active subwoofer(s) and I'm going to explain why.

For a start, the utopian, in theory perfect, loudspeaker would resemble the point of a needle, because it’s not affected by problems of diffraction, refraction, phase, time alignment, and interaction between drivers. Obviously it’s impossible to make a speaker that way, but, compatibly with the sound pressure and the bass extension you want to achieve, the motto must always be “the smaller, the better”, in order to minimise the problems mentioned above.

Then, if you add a sub, the main speakers don’t need to go deep and this is a great advantage, in order to minimise the cabinet dimensions. In fact the big cabinet of the “dinos” has got only one purpose: to try to extend the bass response of the woofer(s). Anyway, they never manage to achieve the deep, clean and fast infra-bass of a good active subwoofer, but what is more, the large dimensions of their front panels (where the midrange(s) and tweeter(s) are lodged), renders impossible, in the mid-high department, to honour the physical parameters mentioned above. Furthermore, many designers of these big speakers, to compound the problems or probably just to impress more, have the nasty habit of using many drivers (two, or more tweeters - two, or more midranges - two, or more woofers), instead of only one per range. Someone should explain to me what for, if the speaker is considered only for domestic use, where a live “rock concert” sound pressure is not the priority! The only advantage I think of, could be that if you double any driver, you increase the sound emission by 3dB, so, at the same level, the use of two drivers reduces the distortion, but on the other hand you gravely increase the diffraction, refraction, phase and interaction between drivers, which results in a confusing and unfocused sound. To make a long story short, these “dinos” are constructed in defiance of the basic rules of the acoustics that I studied in Secondary School, not at University! They are sport cars with hexagonal wheels!

However, to be honest, I have to say that some designers of "dinos", have taken the technical approach more seriously, housing the tweeter and the midrange (fortunately only one per way) in smaller pods, vertically aligned above the big cabinet of the woofer(s). Even if these speakers remain (as normal "dinos") 3-way or sometimes tragically 4-way (with all the insurmountable technical problems typical of these multi-way speakers), they are at least observant of the main rules of acoustics and, for this reason, these "dinos" sound better than the ones with a big front panel full of drivers. The fanny thing is that these speakers in reality are made of a normal two-way plus a passive woofer, so, my logical, plain question is: why the designers of these “dinos” have used passive woofers instead of active subwoofers? Were they afraid of making something good sounding?

Now, I'll confide to you my opinion on why manufacturers of hi-end speakers privilege the production of "dinos" instead of small, serious, 2-way speakers. Probably because they know that it's almost impossible to sell two small speakers at $50k (even the densest Audiophile would start to realise that someone is trying to make fun of him), but it's possible to do that with large speakers and for sure the game’s worth the candle! In fact the Audiophile cannot imagine that the real difference in cost between a well-made bookshelf and a “dino” is not so much: it mostly depends on the bigger dimensions and beauty of the cabinets and on more time (and the time is money) to be studied, because it’s not easy at all to make a 3-way or 4-way speaker with acceptable sound. The real difference in cost between a well-made bookshelf and a “dino” could be around 2 or 3 thousand dollars, mostly due to the bigger dimensions and beauty of the cabinet, but, to be honest, speakers like them also need more time (and the time is money) to be studied and optimised, because it’s not easy at all to make a 3-way or 4-way speaker with a sound that's at least acceptable!

So, in my opinion, very serious 2-way or slim florstander speakers, with a semi-oval cabinet (to reduce internal standing-waves) and a front panel not wider than the woofer, able to produce quite a high sound pressure with low distortion, with a crossover point between woofer and tweeter above 2.5kHz (or higher), are nowadays the best possible speakers for the reproduction of sound from 80Hz upwards. Obviously it has to have only one tweeter and one mid-woofer or (even better) one tweeter and two mid-woofers in a pure D’Appolito configuration, which is the best for imaging. Please don't faint, but my piece of advice is to buy two centre speakers: if you put these speakers vertically on 60/70 cm. stands, you can position them quite easily and in locations impossible for the “dinos”. Furthermore, centre speakers usually produce very accurate sound (designers know that it's the most important speaker in a home-theatre system, so they devote particular attention designing them) and, setting them up vertically, you automatically obtain a pure D'Appolito configuration!

Now the only problem left is to reproduce the frequencies below 80Hz and … the deeper, the better! You do it employing one (or two) serious subwoofer(s), integrated into the system by a professional.

These sat-sub systems will outperform traditional “dinos”, not only because they are much respectful of the rules of physics-acoustics, but for many other reasons, as per below:

a sat-sub system is a bi-amplified system and this means that the main speakers and the amp have to cover only the range up from 80Hz. This is a great joy for the speakers, and also a lovely gift to any amp, but actually a galactic gift to all tube-amps!  Furthermore, a bi-amplified system has got a much higher speed compared to a traditional one. Even if no one (in stores and magazines) mentions the speed, you have to know that the speed is one of the most important parameters of the sound and an essential peculiarity of any instrument! An organ has got no speed, but percussions and string instruments have a high speed and if your system is slow, you annihilate the soul and the sound of those instruments. Audiophiles think that a harpsichord is easy stuff for a system, but they are badly wrong: slow systems can reproduce an organ, but can just pretend at reproducing a harpsichord entirely and a triangle is a whole different challenge!

-  the crossover of a two-way is simpler, and the result, if correctly designed, is faster and time aligned.

-  in contrast to the “dinos”, these speakers are not natural “boomers” and you can even experiment to position them (on stands) close to the back wall or quite close to corners too. Be aware that a binding, but often forgotten, rule is that the speakers must always match the listening room. So, avoid the tragic mistake of buying large expensive speakers for small rooms or just if you have to position them in the very corners. In these cases, only a very serious professional can try to mend their huge and inevitable problems in the bass range. Unfortunately, many Audiophiles find themselves in this situation and they have to thank the lack of professionalism (or the “greediness”) of the vendors.

-  the bass-infrabass range of a serious active sub has got nothing in common with the bass range of the big passive woofer(s) in "dinos”: it’s deeper, faster and cleaner.

-  the distortion of a serious active sub is always lower than that of passive big woofers and consequently its emission of high-order harmonics (generated by the distortion) is much lower, to the great joy of the mid-high range too. Why? Because the 7th high-order harmonic of distortion, for example, at 50Hz, is 6.400Hz. In simple terms, this means that the nasty high-order harmonics generated by the distortions in the low spectrum, are added and distributed (with decreasing intensity) to the whole of the most important part of the audio band! Some pathetic Audiophiles calls it “colour”, but the correct word is “horror”!! In fact, the addition and superimposition of these harmonics on the original sound, emphasises the bass-midbass and obscures the clarity of the whole mid-high. Furthermore, these added harmonics, interfering with the genuine ones, modify the original timbre of voices and instruments. Basically, normal woofers that attempt to go deep, are a real “bungle in the jungle” for the mid-high spectrum too!

-  in contrast to the “dinos”, which, in order to try to achieve a flat frequency response in the bass-midbass, offer only the possibility of moving them around a bit, a sat-sub system can be perfectly tuned for a flat response by a professional. Merely this sets a gulf between the performances of the two systems!

-  compatibly with the quality of the CD and its recording technique, the image, the localization of the performers and three dimensionality are far better using speakers with a small front panel instead of a large one. This statement is against the instinctive and common beliefs of the majority of the Audiophiles, who think that large speakers produce a bigger image, but they are completely wrong indeed! In fact, only small speakers (possibly in a D'Appolito configuration) can rebuild an accurate image. Furthermore, the image is linked to the frequency response by a mathematic relation (Fourier inversion theorem) that practically says: the flatter the frequency response in your listening position, the better the image. So, as emphasized in the previous paragraph, with a good sat-sub system you can achieve a flatter frequency response than with "dinos" and consequently a better image too.

-  the final cost of a perfect system (speakers, sub and amp), is far lower than the cost of a traditional hi-end system. This is a good point for many real Audiophiles, but I also know that for many others, who want to show off, it won’t be a pro, but a con.

-  small speakers reduce the chances of divorce, but … I'm not sure if this has to be always considered a pro: it could also be a con!

So, in the light of these considerations, someone has to explain to me why the large majority of the Audiophiles keep buying “dinos”! If not to appear, the only explanation left is that probably they don’t (or didn’t) know the facts stated in this article. For sure no hi-fi magazine or esoteric "guru" has told them about!

Now a few words about different typologies of big speakers, with their pros and cons:

1) Large, full range, dynamic, multi-way (often multi-driver too), floorstander speakers - The cons are the ones mentioned above and regarding the pros, I have a problem to find any.

2) Big, dipole speakers (electrostatic, isodynamic, ribbon etc.) - The pros are that generally these speakers have quite an accurate timbre and detail, with speed in the mid-high too. Among the cons, there is the problem of their dynamic range, which is very limited and a non-existent infra-bass range: a very serious and fast active sub, perfectly tuned into the system by a professional, in my opinion is compulsory and it makes a huge difference, but, if you only listen to Baroque music, you could use them without sub, with reasonable joy. However, there are other cons: they are dipole speakers, and this means that there is the same emission of sound from front and back. So, the sound frontally emitted arrives to your ears at the instant (t1) and the sound emitted from the back (reflected by the back walls, corners and ceiling) arrives at your ears delayed, at an instant (t2). The result is a sound out of phase, which magnifies, or better, doesn't respect the real dimensions of the instruments (a violin results as big as a piano, for example). Another problem is that the front stage, even if enjoyably wide, doesn't allow for the localization of the performers at all. If you listen to commercial CDs, due to their poor quality and multi-mics recording technique, sometimes these problems are not very evident and you can survive, but with perfect recordings, these problems become evident.

3) Big, full range, dynamic, multi-way floorstander speakers, with an omni-directional (also called poly-directional) multi-driver head, for the reproduction of the mid-high range - These speakers have the same (or even more) cons then the dipole speakers of the previous paragraph and, regarding the pros, I cannot see one.

4) Big, full range, loudspeakers with dynamic woofer(s) and dynamic horn-drivers for mid and high range - A particular, quite long speech has to be devoted to them, but I cannot do that in full here, so I’ll try to be concise, explaining the essentials. Horn-drivers can be classified as first, second and third generation and their only purpose is to increase the sound pressure of a normal driver by a mechanical amplifier that is the horn. Employing these horn-drivers, it's possible to make loudspeakers with very high efficiency (around 100dB 1W/1m).

The most-used ones belong to the first generation and they are basically the same as the ones of 70 years ago, which, even using the best possible modern drivers and Onken, Iwata etc. profiles, produce a sound affected by heavy coloration and sometimes a nasal timbre too. This happens for many physical-acoustical reasons: Alteration of the frequency response caused by the deformation of the membrane, exposed to high pressures generated in the compression-chamber. Internal resonances at different frequencies and their multiples, generated inside the compression-chamber and the throat. Resonances generated by the reflections inside the horn, plus high-frequencies diffraction created by the horn mouth, along its perimeter.

The second and third generation of these loudspeakers is another story. In the last ten years, thanks to the use of computers and very complex computing programs in the hands of skilled technicians, veeeeery few big companies managed to solve, or at least minimise, the problems exposed above. These companies now produce full range high-efficiency speakers (with dynamic woofers and horns for the mid-high) that are in my opinion the best option for a hi-fi reproduction of music in large or enormous listening rooms. However, Audiophiles shouldn't consider employing these speakers in domestic rooms, because they are very big and designed to achieve a perfect balance only at a distance.

Regarding the very expensive “hi-end” speakers, constructed of horn-drivers and dynamic woofer(s), for what I know, almost all of them are made by small manufacturers, who use horns of the first generation and ... any comment is superfluous. Anyway, considering that these speakers represent a minimal part of the market, a couple of simple questions emerge spontaneously: are these few manufacturers the only ones who have understood everything? Is it possible that all the other ones, who are the vast majority and use normal midranges and tweeters, are wrong? I don't think so and I could also add that sometimes this kind of speakers make some tragic “dinos” appear as good ones. However, they are aesthetically impressive and probably the best speakers to show off: for many people the sound is not a priority!

5) Not too big floorstander speakers incorporating top-class active subwoofers - In as much as these speakers are seriously designed, they are the only genuine full-range speakers on the market. Actually they are like sat-sub systems and obviously a very good alternative to them. The mid-high range has to be reproduced by one tweeter and one mid-woofer (or better a D’appolito configuration) and the front panel of the cabinet must be as wide as the mid-woofer. The active subwoofer is in the lower part of the cabinet and, being totally omni-directional, can be side-firing, in order to keep the width of the cabinet not larger than the mid-woofer. A professional can flatten their frequency response without any problems!

To finish, there are other different types of speakers, but not being very representative and many times "ridiculous", I will ignore them.

However, the worst thing about the previous categories of speakers, with the only exception being the floorstanders with active subs built in, is that they are galactically expensive! Nevertheless, technically inexperienced Audiophiles are fatally attracted by the big dimensions of the "dinos" (actually, the bigger, the better) and, without thinking twice, buy them, but ... later, when they start discovering the real “soul” of these speakers, they try to mend the issues buying “blessed” cables and insane accessories, ruining another fortune with minimal result: the reality is that all their efforts only manage to barely chamfer the corners of the hexagonal wheels!

Now you can understand the exact meaning of the head-line of this article, hopefully!

I have used a simple language, not too technical, hoping to be understood by anyone. Actually, this matter is probably the most complex, difficult and important in the hi-fi planet!  So, if anyone has doubts or particular queries, I’d be pleased to be contacted, in order to help him avoid expensive mistakes.



        the problems of speakers positioned in an asymmetric room

Unfortunately, just a small percentage of Audiophiles have the chance to set up the hi-fi system in a room with a perfectly rectangular shape and consequently to position the speakers symmetrically on the bottom short wall (the best). In fact, the majority of us have to cope with the reality of the rooms at our disposal, which normally are everything but regular in shape.

In this regard, you should know that the low range of any speaker is highly influenced by the configuration of the wall(s) around it, so if you have to position the speakers in places with different surroundings (e.g. one speaker in a corner and the other one with just a flat open wall on its back, or in open space, etc.), the obvious result is that each speaker generates a different frequency response from the mid-bass to the infra-bass range, and, for dipole, poly-directional and omni-directional speakers, in the mid-high too!

In order to let you understand the seriousness of the problem entirely, I translate it in simple words: it is as employing different speakers for the left and the right channel! If you have a demonstrative CD, with a track of "pink noise", play it, and start switching (or balancing) between the left and the right speaker. This way, you will clearly and immediately hear the quite shocking difference in sound between the two speakers and ... my best wishes for sleeping well in the night! Regarding the CD with "pink noise", in my view it should be part of the accessories of any Audiophile, so, if you need it, just ask us and we'll post you one.

However, it seems the Audiophiles totally ignore the nasty issue (for sure, no one has told them about!) and this is grave, because this problem is among the most important ones they should care for! So, if you find yourself in this situation, and you want to free the full and real potential in sound of your system, you must have this very audible and disturbing sonic anomaly fixed. Be aware that you cannot mend the outcome of such disturbing stuff changing cables, which could be the "hyper-skilled" advice of some "hi-end guru", but, for this once, you need to get serious and look for the help of a real professional. This guy, with a spectrum analyser, two audio pro subwoofers, and the chance of rolling off the bass response of the main speakers in the needed way, will achieve a flat frequency response in the mid-bass, bass and infra-bass range for BOTH the speakers! Unfortunately, nothing can be done in order to equal the mid-high range emission between the two speakers, if they are dipole, poly-directional and omni-directional speakers. In my opinion, any Audiophile who doesn’t have at his disposal a room with two identical symmetrical ends, should carefully stay away from this typology of speakers!

Regarding the cut of the main speakers, in the presence of a Sachem pure preamp, the professional in charge will find the whole operation very easy, because each channel of its electronic hi-pass filter is independent and can be set up continuously, with different roll-off points and curves. However, even if the pure is the perfect machine for this job, it's possible to achieve a very acceptable (sometimes perfect) result using the passive hi-pass filter of the Sachem v.2, but this filter is much less versatile than that of the pure. The operation becomes trickier in presence of normal hi-end preamps and amps, where the only option to roll the speakers off is to insert a capacitor in series to the signal between preamp and amp, possibly a polypropylene one. However, if the input impedance of the main amp(s) is known, a professional won't have any problems to calculate the correct capacitance for these capacitors, in order to achieve a 6dB roll-off at the chosen frequency.

To finish, the Audiophile must realize that this is the ONLY possible way to operate, in order to comprehensively solve the issue and achieve the same sound-emission in each speaker, customised for your unique listening environment. If you have this job done, you will joyfully discover that your system now provides a new and much better sound, coherent, cleaner in the mid-high, free of booming and finally with a glorious infra-bass too: actually, catching "many birds with one stone"!

Please don't hesitate to contact us if you have any doubts, queries or if you need serious and professional help.



        how to evaluate hi-end CD players

Even if the standalone CD player is at death’s door, replaced by any old computer and a serious DAC, for online streaming at original CD-quality (for complete information about this topic visit the page ”USB audio DACs”), there are still Audiophiles who “invest” a lot of money in esoteric CD players. The question is: is it worthwhile spending $50k instead of $500 on a CD player?

You can probably already imagine what I personally think about it, but far be it from me to influence you, but I’d like to provide you with an unbiased and serious method for deciding unequivocally if it’s worth it, or not.

Considering that the sonic difference between two CD players is always minimal, the only effective and serious method of evaluating it is real-time switching, which, in fact, is the only way to avoid any mental conditioning.

Despite the probable hostility of your retailer to this procedure (potentially toxic to his business), you would ask him to connect a cheap CD player to one input of the preamp of the system you want to use for this trial, and the expensive one to an adjoining input of the same preamp, in order to allow rapid switching between them in real-time. Now you have to feed the CD players with two identical, preferably well-produced, CDs and start playing them, pressing the play buttons at the same instant, for a perfect synchronization.

From now on you can switch between the two CD players at any time, but the first thing you must do is to verify that the levels of the two CD players are identical. If not, the one that’s a bit louder (even minimally) always appears to be the better one: it seems clearer, more selective, etc.

Regarding the volume problems, there are these different possibilities: if you are lucky, the two CD players already put out the same levels, but usually they won’t and if both the CD players have fixed outputs, in order to even the levels, you have to get used to adjusting the volume a bit every time you switch: this is quite imprecise and frustrating, but better than nothing and you have to deal with the fact. It can also happen that one of the two machines has a volume control and, if this CD player is the louder one, just reduce its volume for a perfect parity. There is also the chance that both the CD players have a volume control and in this case you have no problems in adjusting the levels, obviously.

Anyway, once you have attained equal volume levels, the definitive way to conduct this trial is blindly: you must be totally unaware of which CD player is sounding at any moment. To do that, commission a friend to operate the switch, indicating merely by one or two fingers, when switching from machine 1 to machine 2. However, as said before, you must not know which one is the expensive one.

Enjoy the challenge now! I’m almost sure that you are going to meet some interesting and unexpected surprise and you will also understand the possible initial reticence of your retailer!

         a few personal considerations

-) the difference in sound between two CD players (if any) is minimal and almost entirely depends on their analogue sections.

-) as usual, in the hi-fi world galactic and unjustified prices are no guarantee at all of "celestial sound", but merely the result of a very effective marketing operation.

-) before spending heaps of money on these machines that, at best, can only minimally improve the sound of a system, the wise Audiophile has to be totally sure about the sound of the more crucial items in his system, particularly the speakers, which are responsible for more than 80% of the final sound. The funny reality is that a number of these Audiophiles own hi-end speakers that are not able to distinguish sonic differences as minute as the one between CD players! My advice to them is to become as logical as I always try to be, before a hi-fi problem. Practically, if I have a mote and a straw in an eye, I definitely remove the straw before the mote, but ... it seems that in the hi-end world I won't recruit many proselytes!

-) I always advise having a look at the interior of the desired expensive machine; visiting “Google Images”, in order to have a real idea about the technological skill of the designer. Avoid buying machines with messy cabling, untidy layout and home-made ugly PC boards.

-) generally speaking, when you are spending a fortune, real-time switching between two components should become the norm, in order to judge with full knowledge of the facts. However, for practical reasons, it’s not always easy to use this system of comparison. Actually it’s always possible, but for some items (amps, for instance) it becomes very arduous, and in some cases you need to employ a handmade dedicated machine. Anyway, it's easier to compare two pairs of speakers properly in real time; for sure you should avoid a commercial switch-box connected to the speaker cables (not the best solution in a hi-end environment), so, you need one preamp and two identical power-amps, individually connected to each of the two pairs of speakers, plus a switch-box to alternately distribute the signal coming from the preamp to the amps (this line-switch doesn't affect the sound at all). As noted, it’s not impossible, actually it’s easy, but you have to find a retailer who will agree to this: my best wishes!



        balanced or unbalanced interconnections?

Recently, I have realized that many hi-end appliances, in addition to the normal unbalanced inputs and outputs, feature balanced inputs and outputs too, but for sure someone has indeed noted that I have not furnished any of our Sachem electronics with balanced inputs and outputs, so I’m going to explain why.

Let me start telling you that balanced lines are specific to “professional” gear, but be aware that the adjective “professional” is NOT synonymous with high sound quality. In fact, I can affirm that normally (a few exceptions apart) the "professional" stuff is never hi-end in the sound department.

Back to the subject, the only purpose of balanced lines is to avoid the possibility of inducted noise in long signal cables. For example, in a studio or in a concert hall, the cables of the mics are usually very long (often more than 20 metres), and sometimes used in places saturated with radio frequencies and/or magnetic fields. In such circumstances, balanced lines are a must, in order to avoid interferences.

In the hi-fi world, on the other hand, the interconnections are very short, very well screened too, and the line level is usually higher than in a mic line, so it is veeeery unlikely that there will be induced noise, so you won’t need balanced lines at all. Anyway, it's more than easy to verify if you are affected by any inducted noise or not: using unbalanced lines, select an input, turn on the appliance connected to that input, and, without music playing, set the volume as high as possible and ... listen.

As another matter of interest, you may like to know how you obtain a balanced input/output from an unbalanced one and vice versa: just by adding an extra electronic circuit to the output stage of the "sender" appliance and another circuit to the input stage of the appliance that receives the signal, in order to reconvert it in unbalanced again. Usually these circuits consist of IC amplifiers, plus resistors and capacitors. These capacitors are in the signal path and have a capacitance around 10μF, which renders the use of polypropylene caps practically impossible, due to their big dimensions; so, they normally are cheap, bi-polar electrolytic capacitors! Please note that electrolytic caps are the absolute worst quality capacitors made. A good audio designer tolerate them only because, for some things, they're the only capacitors that will work (as in a power supply), but only the most starry-eyed audio technician will tell you that putting electrolytic caps in an audio signal path is an acceptable idea!

So, if your line is noise-free, by utilising balanced interconnections, you are listening to two additional (and not the best, sonically speaking) electronic circuits to NO advantage. I don’t know how much they will affect the final sound, but obviously they do. In my opinion, in a hi-end environment, it would be better to avoid balanced lines and, where balanced and unbalanced sockets are on offer, my recommendation is to use the unbalanced ones.

Now you can fully understand why I didn’t fit the Sachem pure out with any balanced input/output options: the pure is a serious machine, that doesn't need any mirror lures for skylarks to be sold (probably I'm a dreamer), so I wanted to maintain the signal path as “capacitor-free”, in order to keep calling it “pure”.

To provide you with a practical idea of these circuits, the photo below shows the ones (left and right channel) employed to convert the output signal from unbalanced to balanced, in my Sachem microphones preamp. I have had to provide this machine with balanced outputs because some professional recording machines feature only balanced inputs. However, my Tascam recorder features both XLR and RCA input sockets, and ... I always use the unbalanced RCA ones!



                                             the six, black, bi-polar electrolytic capacitors are compulsory and all are on the signal path



        ACE-bass, audio pro's technology to achieve superior infra-bass

There are huge problems in getting deep bass out of small boxes and, so far, many attempts have been made to solve this issue. Leaving aside normal, active sub-woofers, that do not deserve to be taken into consideration (regardless of price and/or brands), serious designers of these devices have realised that, without the help of electronic means, there is no hope of obtaining a decent infra-bass. Among the electronic methods that have been invented and used there are equalised systems, boosted systems and different types of servo or feedback systems. However, most of these methods are limited to closed box systems and increase distortion instead of reducing it, resulting in a muddy sound.

audio pro solved these problems comprehensively with the ACE-bass technology. This revolutionary electronic method provides the driver/s with tailor-made mechanical parameters in real time, so as to obtain a flat frequency response. What is more, since the new synthesized parameters are more linear than the untreated ones, distortion drops automatically. The final result is a frequency response between ± 0.5dB (in anechoic chamber), and distortion at around a tenth of the usual: the “treated” driver becomes very close to an “ideal” one.
This technique of creating the ACE-bass amplifier by feedback loops is unique and was patented by audio pro in 1978. We would like to point out that ACE-bass has nothing to do with (and must not be confused) any other electronic method.

ACE-bass is an acronym for “Amplifier Controlled Euphonic bass”. It was invented by Karl Erik Ståhl and presented at the 61st Audio Engineering Society Convention in New York, in November 1978, where it garnered recognition as a milestone in hi-fi history and in the reproduction of the infra-bass range.

In order to understand the ACE-bass technology, some speaker theory will be necessary, so it is not for everyone. However, what is important for you to know is that with the ACE-bass technology you can obtain an unbelievably deep and clean bass from driver/s mounted in a box relatively small, and this is the case of audio pro subwoofers! Nowadays the patent is no longer effective (patents last 25 years), but you could be still interested in the technical explanation of the ACE-bass technology! If so, please ask us for a PDF of it or, even better, look for it on the web.


        hi-fi magazines ... ?

For sure, hi-fi magazines are useful, particularly their first pages, where they present new stuff and speak about which way the market is evolving, and their last pages, usually dedicated to music and recordings. However, the most important pages should be the ones in the middle, dedicated to the reviews of various pieces of gear, but, regarding these reviews, the shrewd Audiophile ought to ask himself a few questions: Generally, do the reviews tell the truth? Are they made by serious professionals, with at least good knowledge of sound and live classical music? Are the reviewers allowed to tell the bare truth? ... my personal answer to these questions is NO!

In fact, generally speaking, all the magazines live off the money coming from the pages of advertising (more than off the revenue from selling them), so the obvious priority of every editor is to keep their advertisers happy! So, between magazine and importers (or manufacturers) there is a tacit agreement: if you advertise with us, we review your products, and ... this says everything! In your experience, are you able to remember at least one review which has spoken badly about a product? Indeed not, and this is the confirmation that there is something not correct, because I assure you that a lot of stuff (sometimes very expensive), which has received glorious reviews, actually should have been panned. Furthermore, it's very unlikely (actually almost impossible) to find a review of an item imported by a company that doesn't advertise in the magazine.

However, the reviewers are not always in bad faith: in fact, many times they are just incompetent, but this produces the same misleading result. Furthermore, the reviews depend on the personal sonic taste of the reviewers, which could be very different to yours!

I think that the following two paragraphs will be very educational for Audiophiles who take such reviews as gospel truth.

In the Italian hi-fi world, I was one of the opinion leaders for quite a long time, so, in 1986, I was asked to write two pages, "Fair Go" style, for each monthly issue of the Italian hi-fi magazine "Alta Fedeltà". It was very challenging and funny as well, but, just writing in general, not mentioning brands directly (but clear enough for those able to read " between the lines"), after twelve issues, the editor was no longer able to stand the pressure from the advertisers, who, from the very first issue, started to obsess and covertly blackmail him. Thus, I was "kindly" asked to stop and, being his friend, ... I did!

Another illustrative consideration, that merits your reflection, is that, in 1978, when the B2-50 subwoofer (at that time, something comparable to a green Martian appearing on earth) went on the market, NO hi-fi magazine acclaimed, reported on, or even mentioned audio pro, the new subwoofer and its incredible ACE-bass patented technology! In fact, the B2-50 was the very first and only active sub to land on the world's market, so the magazines had no interest in promoting something conceptually very new that had the potential to be a dangerous unsettling factor for the manufacturers of big speakers, and which might lead to a monopoly by a single company in the just-born market for subwoofers. A company, furthermore, that didn't pay for any advertising in the national or international hi-fi magazines and that was the holder of such an advanced and unbeatable technology. So, almost as if by magic, all the magazines politely ignored audio pro and the first machine in the world capable of reproducing the infra-bass range perfectly! For the umpteenth time, proof of the genuineness of the magazines, which, once again, didn't miss the opportunity to show how much they really care about the reproduction of sound and the interests of their readers. Quite sad, isn't it?

The preceding lines are enlightening so as to understand what actually happens offstage in the magazines, so, dear Audiophile, if you have to buy some stuff (particularly if expensive), you may certainly read reviews of it (if any), but be wise and go further: implement your knowledge about the "baby" looking for proper scientific measurements of it, and, visiting "Google Images", have a look at its interior (very important to verify if it's a "festival" of messy cables or seriously designed and built), but mostly, use your own ears and a perfect CD (of which you know exactly the content) for the final judgement. Please, don't be lured and misled by biased, or just incompetent, magazine reviewers! If you follow my advice, you will surely be much richer and much more satisfied with the sound of your system!

For your information, I gladly stopped reading hi-fi magazines in 1987. The magical end of bilious attacks, plus a virgin and unbiased approach, when I have to evaluate new gear!

You will find other interesting considerations about reviews and reviewers in the pages "live music vs. hi-fi" and "the hi-end doctor".



        serious corner  (this article is written by Peter Aczel, who is not the usual incompetent columnist found in some hi-fi magazine, but a high calibre mathematician and scientist, with the added passion for the reproduction of the sound and I mostly agree with him. Read here about him   (for the vinyl fanatics)   (very interesting and serious article! Things I've been saying since many years ago)


        comedy corner