Special Projects - CORUM AUDIO
We have always loved music and we have had our best ideas listening to music and could not live without it.
For a long time, we’ve nurtured an ambition to push music reproduction to the absolute limit.
We believe that in Corum Audio we will be able to do that.
Our goal is a simple one: build the world’s best sound reproduction system.
We want to recreate, with absolute fidelity, the artists’ performance in your own living room; so that when you close your eyes you can believe you are together in that room.
Perfection is what we want, not a system that ‘colours’ sound. Purity, in our mind, is the most desirable quality reproduced sound can have.
The distortion of a loudspeaker system is a complex distortion made of frequency response distortion, phase distortion, and time distortion.
Usually in a direct radiation system this distortion is over 10% at its high level reproduction sound.
More, the power from the amplifier is shared in sound in the range from 0,1% to 5% and 95% to 99.9% of this power heats the voice coil.
So we implemented a horn & waveguide system starting from high efficiency components with a real heart: the speaker management system.
The efficiency is over 105dB to have the least diaphragms displacement; we maximize the power conversion factor; the fly time of the sound from the different units-ways is exactly the same; the frequency response is flat from 30Hz to 29KHz.
Everything is focused on reaching the lowest distortion even if you are listening to a sound program with peaks of 115dB or over, on having the best possible transient response and not losing the image of the reproduction.
We use beryllium diaphragms, paper cones, and solid wood to have the smoothest sound possible without any loss of details.
We use alnico magnets to not lose the micro-details of the sound, always present even if the reproduction sound level is high.
At the end we implemented a passive diffuser based on Schroeder formulas integrated on the back and front of the single elements, so the reflected waves become an important component to create the ambience.
The system is the synthesis of 5 years of prototypes and Computer aided design.
Since the beginning our target has been to give you that feeling of being together with the artists in your living room.
Since the beginning we in Corum Audio have wanted a sculpture that could share with you an exclusive feeling.
We rejected the idea of just a conventional loudspeaker system made of cubes, towers and banal shapes.
Corum Audio, a sculptor and engineer team, cooperate to meld an artistic and technical approach to attain the best sounding and looking system.
Place the system in your living room, in your conference hall or wherever, it must be an your absolute pleasure, your own secret smile.
The system will be the statement of your life style.
Our goal is a simple one: to fascinate you. You will be surprised with your eyes and your ears … we want to generate an emotion that enthrals both you and your friends.
Nothing is left to chance, all the details are important; right from the start we select the wood, we soak and slowly dry the raw wood, we saw and joint slice by slice completely manually, matching the veins.
We follow the carving process carefully step by step and finally the system is hand carved, polished and waxed by the expert hands of the sculptor. It takes at least six months for these sculptures to be created by sculptor’s hands.
Corum Audio proposes a sculpture and not only a speaker system, truly hand made in Italy, truly a work of art.
Where you put the system will no longer be the issue it will probably be in the most important room of your home.
Every system is unique a real limited edition.
You can choose from Italian walnut, rosewood, lime, oak, your choice. We can carve the limited edition sculpture to meet your requirements. Unlike any other. An exclusive sculpture & sound reproduction system.
The name. Short, simple, important: Sinatra System.
Voice, sound, rhythm, evocative atmosphere, Italian design, 100% hand made in Italy, art ... Sinatra System:
no better name to represent the Corum Audio ambition.
- Efficiency: 105 dB/W/m - with the bass cabinet against a wall and close to a corner
- Frequency response: 27Hz-29KHz - with the bass cabinet against a wall and close to a corner
- Impedance: 8 Ohm
- Bass: 15” Paper Cone 60W – solid state amplifier preferred
- Medium: 2” 30W Beryllium Diaphragm – tubes PP or SE amplifier preferred
- Medium – Treble: 1” 20W Beryllium Diaphragm – tube SE amplifier preferred
- Super Tweeter (Optional): 15W Beryllium Diaphragm – tube SE amplifier preferred
- Bass: 90x90x135H cm included the stand
- Medium & Medium Treble: ≈90cm diameter – 145H cm with the stand
- Bass with the stand included approx. 320 kG
- Medium & Medium Treble with the stand included approx. 240 kg
- DSP: 2x paralleled DSP 96KHz/24bit (optional 192KHz/40bit floating point) always working at the maximum resolution
- Clock: ultralow jitter 24.576 MHz - precision 0,1 ppm
- A/D/A Sample rate: 96 KHz/24 bit (optional 192KHz/24bit)
- Signal delay: less than 1 ms - A/D and D/A
- Frequency Response: +0/-0.1dB - 7Hz to 32KHz
- Dynamic Range 110dB unweighted - A/D and D/A
- THD + Noise: (digital core) less than 0,001% - 20Hz to 20KHz unweighted
- Integrated MUX: 2x BNC S/PDIF EBU, 1x Toslink™, 1x XLR S/PDIF EBU
- PLL receiver - maximum distance 30 meters
- Sampling rate frequency: 44.1 - 48 - 88.1 - 96 - 192KHz
- Input impedance: 75Ωbalanc. - input level 0,1V to max 3,3V but Toslink™
- 3xRCA analog balanced, 1xXLR analog balanced
- mu-metal core transformer coupled (optional amorphous core)
- Crosstalk: -90dB @0 dBu In
- Input impedance: 20K balanced
- Max input level 2,5Vpp
- 6 bands, miniXLR balanced, mu-metal transformer (optional amorphous core) + 6 bands, miniXLR balanced, SE CV181T output line stage, Double-C core output transformer
- Volume control: 12 analog channels, digitally controlled. Positioned just before the outputs and after the digital D/A
- Maximum output level: +21 dBu
- Crosstalk: -100dB
- Output impedance: 360ohm balanced SE tube stage output, 100ohm balanced direct output
- X-over points freely adjustable for each channel: Butterworth 6, 12, 18, 24 or 48 dB/oct slope; Bessel 12 or 24 dB/oct slope; Linkwitz-Riley 12, 24 or 48 dB/oct slope
- Dynamic equalizer freely adjustable for each channel: Low-pass, Band-pass, High-Pass
- Delay freely adjustable for each channel: From 0,00 to 11,00ms (0 to 3780mm) - 2.9uS (1mm) steps
- Polarity-Phase freely adjustable for each channel
MAINS POWER SUPPLY
Sinatra at work
Why a sculpture?
A speaker system is usually a compromise and must fit standard industrial production requirements. By that I mean usually the limitations are set by what the industry can easily build with standard machine mills, saws, drills, sprayers. The budget is the main limitation so usually we have square boxes, at most a few small spherical parts to make it more appetising.
We worked without a budget , we worked ignoring the limitations imposed by standard production and we strove towards our goal to have the best sounding system even if it was a crazy idea, almost impossible for a company whose God is profit.
Why not think about a work of art rather than of a box for the reproduction of sound.
It is a system to show off; an astonishing system to leave your guests and friends really impressed. A status symbol.
Why a horn ball speaker system?
A loudspeaker system with a direct radiation suffers from a huge distortion mainly because of the big displacement of the membranes of the speakers themselves and the too drastic step the sound has to make when passing in front of the membranes to the free air.
The horns make the step between the diaphragms and the free air smoother; the result is a more natural emission: the sound waves are accompanied to the exit instead of pushed out. Technically speaking, the air in front the loudspeaker is more resistive than reactive so the vibrations released by the diaphragms are seemingly converted in vibrations of the air.
Horns have been well known since the beginning of the 1900’s and it was only at the end of the 1900’s that engineers discovered the vestigial also called waveguides. They are an evolution of the original idea, better calibrated by computer aided design.
Our profile is one of trial and error, results of a development that took 6 years. Not a classic horn, not a classic waveguide: a compromise for HiFi use
Anyway what we call it horn doesn’t have anything to do with the exponential or horns of 70 years ago.
Why a high efficiency system?
People know an efficiency system sounds more “live”. A horn system has got an efficiency 10 to 20 times higher than a conventional speaker system. That means the sounds are generated more easily and the feeling reproduced is one of a live situation.
To achieve this we use the lightest membranes and diaphragms currently in existence, paper under 100 grams for the woofers and beryllium for the medium and the treble.
In addition, we use the strongest magnets possible to use in these applications: Alnico V. If you consider only the magnet strength then they are not the strongest. But if you consider the micro-details the choice can only be Alnico V. Alnico V magnets have the best linear response even around zero. This means they don’t lose the micro-details of the sound program even if you are listening at a high level your ears capture a lot of information, you are listening to loud music but you are still hearing the micro details: the ears hear everything even when the sounds are mixed together.
Furthermore, because of the horns and high efficiency the membranes seem to be inoperative; to check they are still “alive” you have to touch them and although you can feel the vibrations with your fingers your eyes don’t see any movement. In a conventional system if you don’t’ pay attention the woofers jump in your arms. No displacement of the membranes means no distortion.
Finally, last but not least, you can use low power amplifiers. That means you can use power amplifiers with only a few components. That means the sound path is minimal. That means you can use SE triode amplifiers with a few watts only. That means the sound remains close to the sound captured by the microphone at the moment of recording. That means good!
Why the horn systems are not so common?
They are expensive because of the material used, the workmanship needed, the problem to move them in the market. So the potential customers are few and it is not good business.
A big space is needed to house them. So the potential customers are few and it is not good business.
They are not easy to set up. So the customer usually cannot buy and install by themselves.
It can be said that a horn system is not a ready to use system.
You MUST solve the time difference between the sources of the sound, better, the different position in the space of the emission points of low, medium, tremble.
You MUST solve the limitation of the horn load in the low end of the sound band.
You MUST solve the different efficiency of the different ways.
So, all things told, the potential customers are few and it is not good business.
Why the cubes engraved on the surfaces of the speakers?
To use the system not only as an emission system but as a diffraction too.
The sound propagation doesn’t stop when it reaches your ears, it continues to run against the walls, roof and floor, and come back to the emission speakers and the reflected sound waves are added to the original sound program.
This is a natural phenomenon involving reverberation time and time decay. Not easy to summarise here. Anyway it should be clear to everybody that if the reflected waves are added without any care to the original sound program the result isn’t good. We use the reflected sound as useful information, spreading the reflections first and then adding them to the sound program.
By the cubes distributed on the surfaces of the bass cabinet and medium tremble cabinet and the engraves the reflected sound is spread everywhere, so to have a smoother end result distributed to the entire spectrum. We avoid any concentration. Shroeder investigated the matter in depth and proposed his math formula to predict the phenomenon.
Starting from these studies and after a trial and error program we have reached the best compromise which we implemented in the system.
Why a spherical horn for the medium-tremble ways?
Thanks to the study of Philip Newell and Keith Holland, published in “Studio Sound” March 1994, “Round the horn”, the distortion of a round horn is much lower than a controlled dispersion horn with side walls.
Before, Henry F. Olson, investigated and demonstrated the smoothest response is for a spherical cabinet.
And in the range 500Hz to 5KHz the ears are 2 incredible instruments which can hear small differences and distortions.
So we implemented from and up 500Hz the spherical design. It is usually an expensive solution and mainly for this this is limited to small part of the commercial system. Our sphere is 90cm diameter and weighs close to 100Kg.
The approach we used in the project was to implement everything technically explained and thoroughly investigated. The secret is to know everything concerned with what you are doing, only in this way the result is close to the maximum possible. Of course you don’t have to worry about budget and you have to look only to the business; worse, you cannot propose a system radically different from your standard offering.
Always when we implement a solution there must be a technical explanation of it. This the main secret. If you know all the aspects involved with as system, you can manage it. Otherwise you are proposing the well known “snake oil”
Horns systems suffer from a huge sound image and time distortion, don’t they?
Right, if you don’t manage the different position in the space of the emission points properly.
In a horn system where the emission points are not close, the risk is to have a huge image of the sound message. You hear everything as if in a very big space. This is true when you buy a pro horn system and you install it by yourself without considering the time difference between the ways.
A horn system MUST be managed by a “control center”: our Speaker Management System. It is impossible to use a basic crossover network. If you do so, the result is ugly, huge, sharp, aggressive, without bass, and almost impossible to hear in a room.
A delay line must be implemented so the emission points are all in the same plain and as if by magic the image becomes stable and focused. It is a so called in phase emission.
Don’t forget we use Alnico V so as not to lose any information, mainly around the zero crossing of the signal, means we don’t’ lose the micro details present in any sound program.
In phase emission and micro details contribute to a natural, smooth and focused sound image.
Is it an active sound system?
Not exactly. Half and half. The power amplifiers are not included. But the system is equipped with a Speaker Management System to manage the time delay, the different sound level, the crossover points of the different sound sources and finally flattening the frequency response from 30Hz to 29KHz.
The heart is digital, 96KHz or 192KHz frequency resolution and up to 40 bits floating point. With paralleled DSPs to manage in real time all the signals and all the algorithms to implement.
Without a digital engine system all the things needed are almost impossible to implement or, if you implement in the analogue field, the result is not HiFi but suitable only for the Pro applications.
Why a digital heart? Usually a digital system sounds sharp and not smooth.
Usually you are right because digital is implemented by simple and cheap solutions, to minimize the price and maximise the offer; everything for everybody all the time!. A system for the people. But if you know what you are doing you can manage and have a high performance system even if in the digital domain.
The jitter is the main cause of the sharp sound and to cure the problem we implemented an extremely low jitter clock, below 0.1ppm for the whole system. In addition, a PLL digital receiver stage to be immune from the sources and their distances from the system.
The power supplies of the digital and analogue path are totally separate and independent. The Main Power Supply is equipped with 5 transformers, one for the tube stage, 2 for the digital paths and another 2 for the analogue paths. All the designs are with a ground plane to control the noise.
Almost all of the capacitors are made of polymer instead of electrolytic.
The A/D and D/A converters are the smoothest on the market, developed mainly for Audio.
The output stage of the D/A is made by a special audio C-core transformer , followed by a simple filter made with Hi Grade Audio components.
The digital heart works always at the maximum resolution because the volume control is placed after the D/A converters and before the power amplifiers.
… all technical jargon … but the question needed a technical reply first.
If you know what you are doing you can cure and avoid the ugly behaviour of the digital implementations made in the past or copied from other application fields. For us it is important the system has to sound, not just work.
The secret, as we said before, is knowing what you have in your hands and how to reach the maximum performance, knowing the application is for HiFi audio and not for pro audio, or car audio, or PA audio or industrial electronics.
Two well-known violinists, Isabelle Faust or Mario Brunello, get the best performances from a Stradivari violin or viola, dated 1700-1720 and made in Cremona. But instead of the original strings with sheep gut, they use modern metal strings and the handle is modified. The end product is the smooth sound of an original Stradivari, with, at the same time, the frequency extension and the fullness of the modern violins.
So the best performances usually are from the best mix of the best things of the past, present and future.
Why a 6 way – stereo Speaker Manager System?
So that our customers have the opportunity to implement a no-compromise system. So you can manage a subwoofer, usually many cubic meters away in another room or an open baffle using the loft, a bass, a medium bass, a medium tremble, a tremble, a headphone. All stereos. Totally 6+6 channels.
What kind of power amplifiers are better to use?
That depends on the behaviour of the user.
For sure the medium and the tremble can be driven with full satisfaction by mono triode amplifiers, I prefer 2A3 or 300B SE without any capacitor in the signal path, at most with inter-stage transformers. A few watts are more than enough.
For the bass section, a 2A3 PP amplifier with inter-stage transformer or a BJT amplifier with transformer driver. Anyway always with only a few components in the signal path. 20 real watts are enough.
How about the installation?
We usually ask for the floor plan of the room which will house the system. The system is not small so at least the space to get the system through the doors is needed. Better not a studio-flat.
What kind of wood can be used to make the sculptures?
Maple, walnut, mahogany, not too hard or too delicate wood, it is really a sculpture. The surface is impregnated and finally finished by wax, 7 layers. So the wood surface is not too difficult to keep in its natural state.
Is it really handmade?
We start from the raw wood, and we chose that which is suitable for the sculpture. We dry the wood artificially for 30 days, slowly slowly. Later the wood is left in the free air for 6 months. Minimum. After this the wood is cut in slices and glued together like in a sandwich. After 7 days when it is stable we engrave roughly by machine. Finally we engrave by hand and we deeply polish by hand . Finally, the wood is sealed by 7 layers of lacquer and wax .
So, if we find the wood as per user request at the time of the order, we can deliver usually within 6 months. If the wood is not immediately ready, we have to source somewhere. The rarer the wood and the longer the delivery time. The wood is be selected by us directly at the warehouse of the sawmill. Usually Italy, France, Romania or Georgia.
We have in stock some ready to use particle boards, mahogany, lime, walnut, maple and in this case the fastest delivery time is 4 months, availability depends on the open orders.
…. now you can understand why each system is more than a Limited Edition, it is a unique system. It is a work of art.