System Design

2018/11/24 created
2021/03/13 updated

Design Targets

The primary target of Gaudi II's system design is eliminating the shortcomings of Gaudi. I believe that for achievement of the best sound quality it's better way to solve problems one by one than to employ outstanding circuits and/or mechanisms.
Unsolved problems in Gaudi

In addition, the following items are set as priority targets.

  • To improve convenience
    Maintenance free, remote control, low power consumption
  • To improve affinity with visual components
    Pure audio system to A/V system
  • Enhanced immunity
    Not affected by power supply voltage fluctuation and noises from outside
  • Higher sound quality by utilizing psychological effects [2021/02/07 added]
    Stress-free operationality, appearance harmonizing with the interior of the room

Gaudi was also used like an A/V system, and I'm planning to further enhance Gaudi II's function and performance as an A/V system while giving top priority to sound quality.
If I'll have energy to spare, I also want to challenge the 4-channel stereo system like Sansui QS4, which was the rage in 1970s. I have more than a dozen of vinyl discs that are compatible with QS4. Some of them are recorded by artists who ingeniously utilized the surround effect for their music. I want to listen to their recordings with the sounds they intended to make.

For Gaudi system, I stuck to designing and building all the components, but I've decided to use commercial products, except for components for which I can make use of my own ideas.

Better yet, you also have an option of composing the system with commercial products only. However, in that case, you will use components that do not fully match the system design. Commercial products are those designed by professional, but because they are not designed according to your order, they could cause some problems.
Especially,it is obvious that custom design is more advantageous for loudspeakers and power amplifiers. Because the size of the room and the quality of the room acoustics have a great influence on the loudspeaker design, and the loudspeaker design has a great influence on the power amplifier design.

It will be the choice of which to choose between commercial products designed by professionals and custom components designed/built by an amateur. In the latter case, the result depends greatly on the level of knowledge, techniques and skills of himself.
I chose the latter. The more you brush yourself up, the better the sound quality of Gaudi II. It looks like a mirror reflecting yourself. Also, depending on your own hard work, there is a possibility to realize sound quality exceeding the manufacturer's high-end system. Just thinking so excites me.


Specifications

The specifications of the whole system is as follows:
[2021/02/07 Revised] {This section has been re-written because many things have changed (Ver.2.3)}

Input source
Analog disc ... LP, EP, also SP if possible (main source)
Music files ... DSDIFF, DSF, WAV, FLAC , AIFF, ALAC, WMA, MP3 (DSD up to 5.6M, PCM up to 192kHz/24bit)
Internet radio (FM, AM radio)
CD, DVD, Blu-ray Disc
TV (cable TV set top box (STB))
Other ... Smartphone, portable music player, etc.
Preamp inputs
PHONO: For AD player ... RCA Jack
DAP (LINE IN): For digital audio player (music files, CD, DVD, BD & net radio) ... unbalanced, RCA jack
AUX (LINE IN): Auxiliary input (for STB or other sources) ... unbalanced, RCA jack
Preamp outputs
EQ OUT: Phono EQ output ... unbalanced (RCA jack)
PRE OUT: Preamplifier output ... unbalanced (RCA jack)
Frequency response
25Hz-40kHz (+/-6dB) (system level), 1Hz-100kHz (+0.1/-1dB) (amplifier)
Phase deviation: +/- 30 deg (at 100Hz or higher, system level)
Distortion ratio
THD+N: Less than 1% (system level), less than 0.01% (amplifier)
<< THD (total harmonic distortion) does not reflect sound quality so much. What kind of indicator best reflects the sound quality, currently under study >>
Transient chracteristics
40usec impulse response: Settling time < 0.5msec (system level)
No ringing in 10kHz square wave response (amplifier)
Max SPL
110dB (L+R, at the listening position)
Power dissipation
Less than 100W (when playing an analog disc)
Convenience
Wireless remote-controlled selector and volume
Wireless remote-controlled music play (except analog disc)
Others
The potential of the frame ground (FG) is the same as earth.
Even if there is a difference in ground potentials of devises, not to impair sound quality.
Each device is to be designed so as to enhance immunity for AC line noise (under consideration of quantification)
Appearance that harmonize with the interior of the room ... the theme is 'cozy atmosphere'

For details on how I fixed the specifications, please see the following PDF.
Details on System Specifications (Gaudi2SystemSpec_en.pdf)

I put my opinion on the sound quality of the vinyl disc on another PDF. Please click on the button on the right.


Configuration

[2021/02/07 Revised] {This section has been re-written because many things have been changed. Here is the revision history}

Ver.2.0: Improved version of Gaudi
Ver.2.1: PC replaced DAP
Ver.2.2: DVCS has been introduced
Ver.2.3: Digital crossover network and power distributor have been employed

System Configuration Ver.2.3

Like Gaudi system, Gaudi II is a triamplified system (3-way multi-amplifier system).
The reason for sticking to the multi-amplifier system is that it is the best method to minimize distortion in system level.
The LS unit is a transducer whose output sound pressure is proportional to the input voltage. If there's an impedance between the power amp and the LS unit, the input voltage of the LS unit won't be equal to the output voltage of the power amp. This will cause distortion in principle.
In the multi-amplifier system, the LS unit is connected directly to the power amp. There isn't any unwanted impedance between the amp and the speaker.

If there were true full-range LS units (having flat response between 20Hz and 20kHz with very low distortion), the single amplifier system could be a hi-fi system. But as long as I know, there exists no such LS unit.

All the power amplifiers in Gaudi II are semiconductor type.
I won't use vacuum tubes any more, because they have instability factors such as aged deterioration, and pick up microphonic noise. Compared to vacuum tube power amplifiers, the semiconductor power amplifier has lower output impedance, so it can bring out the advantages of multi-amplifier system more.

I considered a stand-alone phono EQ amp (phono equalizer amp), but I've decided to include the phono EQ stage within the preamplifier, bacause analog disc is the main source in Gaudi II.

I also considered embedding the crossover network in the preamplifier, but I gave up the idea. Because the preamp should be placed near the players and the network should be near the power amps, and the power amps should be placed close to the loudspeakers and the players should be far from the loudspeakers as long as possible. If the network is embeded in the preamp, the six LINE cables have to be much longer.

The biggest difference between Gaudi and Gaudi II is the volume control. In Gaudi II, the volume control itself is not included in the preamp. Six mono volume units are embedded in each power amp, and they are controlled by the MCU (micro controller unit) in the preamp. The MCU receives signals from the volume knob (rotary encoder) of the front panel or an infra-red remote, and sends control signal to each power amp.
I named this system 'DVCS' (Distributed Volume Control System).

Components

The record player (ADP) is Technics SL-1200GR, and the cartridge is Audio Technica AT33PTG/II.
As for the cartridge, I will consider replacing it with another one, when the stylus reaches its end of life. There is a possibility that I may choose AT33PTG/II again after the consideration.
Actually using the SL-1200GR, I judged that it has the necessary performance as Gaudi II's ADP. The good point of the SL-1200GR is that it is well vibration-proof. It may be said that it is the most important performance for ADP.

PC is used as digital audio player (DAP). The PC must be specialized for audio use; no cooling fans, SSD for the main drive, only DAP apps installed, etc. Such PCs are available these days.
I've been using Sony HAP-Z1ES, but I am not satisfied with its sound quality. And, the PC excels the HDD player in expandability. I've decided to replace HAP-Z1ES. For details of HAP-Z1ES, see this page.

All the amplifiers are to be newly designed and built, because the amplifiers in Gaudi do not meet the requirements of Gaudi II.

The loudspeaker is SS-309B. It is an improved version of SS-309A that meets requirements in Gaudi II.

Category Maker Model # Outline specifications Note
Analog disc player Technics SL-1200GR Direct drive turntable
33/45/78 rpm
Statically balanced tonearm
[reasons for selection]
Cartridge Audio Technica AT33PTG/II MC type, Microlinear stylus
Output: 0.3mV, F-range: 15-50,000Hz
[reasons for selection]
Replacement to be considered
when the stylus reaches its end
of life
Digital audio player Olio Spec canarino fils9 500GB SSD, Core i3-10300T, 16GB RAM
No cooling fan, high-quality PSU
[reasons for selection]
Preamplifier NOBODY CC-218 Diversity
(tentative)
Open-loop type phono EQ,
Gain=66dB (MC only)
Embedded MCU
Flat stage: Gain=0dB
2x LINE IN, EQ OUT, PRE OUT
Infra-red remote
[details]
Crossover network
(channel divider)
(TBD) (TBD) Cross points: 1,800Hz, 6,000Hz
48dB/oct digital filters
Time alighment adjuster
[details]
May be substituted by a manufacturer product
Power amplifier
for tweeter/squawker
NOBODY MA-219
(tentative)
Tweeter: class-AB 10W mono
Squawker: class-AB 10W mono
[details]
Two units used
Power amplifier
for woofer
NOBODY MA-220
(tentative)
Class-D 80W mono [details]
May be substituted by a manufacturer product
Two units used
Master/slave volume control NOBODY MV-222
(tentative)
Mono master/slave volume control
using EVR chip
[details]
Paired with woofer amp
Two units used
Loudspeaker NOBODY SS-309B 3-way speaker system
Tweeter: Fostex T925A
Squawker: Fostex D1405+H400
Woofer: Fostex FW305
[details]
Power distributor TASCAM
(tentative)
AV-P250S
(tentative)
Switched outlet: x10
Unswitched outlet: x3
[details]
Audio rack NOBODY AR-416 Air Granite stone base
5-tier wood rack
vibration-proof
[details]
Audio rack for players and preamp
Audio Rack NOBODY AR-421
(tentative)
3-tier wood rack [details]
Audio rack for power amps
Sound diffuser NOBODY SD-423 Wooden diffuser [details]
Cable TV STB Technicolor BD-V570 Terrestrial, BS, CS, double tuners
Recording feature w/ USB HD
[reasons for selection]
Leased by CATV company
TV/display SHARP AQUOS 4T-C43AM1 43 in. flat display, 4K
HDMI x4
[reasons for selection]

Maximam Output and Gain

For Gaudi system, I decided the maximum output of each amplifier with a rough estimate. As for the gains, I decided them with little consideration.
For Gaudi II, I set appropriate values ​​under certain grounds. For details, please see the following PDF.
[Max output and gain (OutputPowerAndGain_en.pdf)]

Maximam output voltages of preamplifier & crossover network
2V (RMS)
(There is a possibility of making it 2.8V (+3dB))
Maximam output power of power amplifiers
For tweeter: 5W ==> 10W [2021/02/18 changed] {The spec of the tweeter amp is changed to the same as the squawker amp}
For squawker: 10W
For woofer: 80W
Gains of amplifier stages
Please see the following system block and level diagrams. (Click to enlarge)
Note that the master volume in both figures is actually built in each power amplifier.
[2021/02/18 chnaged] {The gain of the tweeter amp is +16dB in the diagrams, but it is +19dB (same as the squawker amp) in the actual system}Gaudi II block diagramGaudi II level diagram

 


Settings of Crossover Network

[2021/02/20 added] {the whole section has been added}

Gaudi's lower crossover frequency (fc1) and the upper one (fc2) were 800Hz and 6,800Hz, respectively. I re-considered wheather these are right or not.
The reason for fc1=800Hz is that the high end of the pistonic motion range (fp) of the woofer (Fostex FW305) is 450Hz, and it's desirable if fc1 < 2fp.
The reason for fc2=6,800 is that it is the lowest cutoff frequency recommeded for the tweeter (Fostex T925) by the manufacturer.

In general, it is difficult to realize a horn-loaded speaker that has a flat frequency response in a broad band. The squawker (Fostex D1405 + H400) is not an exception. Its frequency response has a peak at 1kHz and the level gradually declines as the frequency increases.
On the other hand, the tweeter (Fostex T925A) has excellent characteritics. Its frequency response is flat between 3kHz and 20kHz. The recommended fc is 6.0kHz or higher.
The recommended fc for the woofer (Fostex FW305) is 2kHz or lower. It is real that its sound quality in low treble is so good.

Gaudi II - Crossover frequencies

According to the above facts, the range of the squawker should be narrower. So, the ranges of the tweeter and the woofer should be broadened.
Though the wider range of the woofer increases distortion due to breakup motion of the diaphragm, I dare extend the fc1 to 4fp (4 x 450Hz).
The fc2 is set to the lower limit of the recommended frequency for T925A, because T925A's performance is so good.
fc1=1,800Hz, fc2=6,000Hz.

The figure on the right shows the frequency response of the crossover network. It indicates the passband of the woofer(LOW) is broad and that of the squawker (MID) is narrow.

Steep-cut filters are used in the crossover network in order to prevent interferenece among the LS units. It is easy to realize it, since a digital crossover network will be used in Gaudi II. The steepness will be -48dB/oct (it is -24dB/oct in the figure above, but it's -48dB/oct in the system design).

The settings of the network, shown above, are subject to change in the system-level tuning to the optimal values.

By the way, such a theory seems to still remain that a filter of -6dB/oct is the best for the network, or 2-way speakers are better than 3-way or 4-way. I don't agree on it. The treble from the woofer and the midrange from the tweeter have much distotion. The mix of them increases overall distortion. In a theoritical sense, it is obvious that the steep-cut filter is desirable, and 3-way and 4-way are better than 2-way in a multi-amplifier system, because the narrower passband of each LS unit excludes the distortive band of each LS unit.
Whenever the theory and practice are not consistent with each other, there is (a) unknown problem(s). Discovering and solving it/them will make the theory and practice consistent. It isn't my way 'Tonochi Methods' to jump to empirical rule without seeking for unknown problems.


Layout

[2021/02/20 revised] {the whole section has been re-written (Ver.2.3)}

System layout (Ver.2.3) - Overview

Gaudi II is installed in the living room.
The living room is located on the northern half of the second floor of my 2-story wooden house. The floor is a woody flooring. The room is western style (not Japanese style). The floor space is about 13 sq.m. (= 3.6m x 3.6m). It's adjacent to the dining room in the south and the stairs in the east. There aren't walls to divide the rooms. The distance between the south end of the living room and the south wall is more than 3m. The distance between the east end and the wall of the stairway is more than 1m.
The celing is a slant type. The topmost part is aoubt 4m high from the floor. The material is a natural wood.
The room has enough air volume for a listening room.

The figure on the rightshows the overview of the system layout. In the figure, some acoustic devices like a sound absorber (marked 'A') are installed. Those are explained later in the section 'Room Acoustics'.
The figures below show the layout of the system, particularly the location of the loudspeakers and the listening position.

The players and amplifiers are placed on two audio racks, AR-416 and AR-421. The players and preamplifier (control center) are placed on AR-416. The crossover network, power amplifiers, STB and power distributor are placed on AR-421.

System layout (Ver.2.3) - Side viewSystem layout (Ver.2.3) - Top view

 

 

 

 

 

 

 

 

 

 

Another layout plan

AR-416 is located near the loudspeaker (the left uint of SS-309B), and this is not desirable in terms of acoustics. The better position is the position shown in the figure on the right. This position is also better in terms of operationality. But the room is a living room, not a dedicated listening room. It is important to consider furniture layout and functions as the living room. I've taken the layout shown in the figures above.

The listening position is located at the position where the height of the ceiling is the highest.
The angle of the loudspeakers viewed from the listening position is 38 deg. Some would say it is too small. My old textbook (Ref #8) says that the angle shoud be more than 50 deg., and the ideal angle is 60 deg. It also says that if the angle is less than 30 deg, the listener cannot get stereoimage. It may be true with out-of-date low resolution audio systems. In my experience, however, the angle of 20 deg can make stereoimage.
The loudspeakers come near the sidewalls as the angle is widened. This may result in unstable sound image localization caused by the first reflections from the walls. In the worst case, sound image cannot be located in the center. Apart from the worst case, I feel it unnatural if sounds come sidewise. I believe 40 deg is the best.
According to the liner note of '2xHD Audiophile Speaker Set-Up', the best angle is 49 deg. Probably, it is a recent theory.

The layout might be changed according to the result of the system-level tuning.

Component layout V2.3

The placement of the components on the audio racks is determined in manner of sound quality first (see the figure on the right).
First, the record player (ADP) should be placed where vibration from the floor is best insulated. Secondly, the other components should be placed so that the cables are as short as possible.

The ADP (SL-1200GR) is placed on the top tier of the vibration-proof rack , AR-416. This place is the best insulated. In addition, it's the best position for the user to manipulate it.

Among the cable related issues, the length of the speaker cable affects sound quality more than the others. The power amplifiers should be placed near the LS units. The target lengths of the speaker cable is 70cm.
The woofer amp (MA-220) is fixed on the woofer box of the loudspeaker (SS-309B). The volume control for the woofer amp (MV-222) is on the bottom tier of AR-421.
The squawker/tweeter amp (MA-219) is placed on the top tier of AR-421.

Many cables are used to connect the crossover network with the power amplifiers. So, the network is placed on the top tier of AR-421. It's also okay to put it on the middle tier.

The preamp (CC-218) should be placed near the ADP for a good manipulability. It's placed on the second top tier (the right under the ADP) of AR-416.
On the two tiers below the DAP and its peripherals are placed.
The DAR (MR-2000S), which is less frequently used, and measurement instruments are placed on the bottom tier of AR-416.

The most components that receive AC power from the power distributor (AV-P250S) are on AR-421. So, the power distributor is placed on the bottom tier of AR-421.

The crossover network and the power distributor are commercial products. Their appearances aren't suitable for the concept of Gaudi II. They are covered by half-transparent acrylic panels.


Cabling

[2021/02/21 revised] {This section has been rewritten (Ver. 2.3)}

I don't care much about cables. From my experience with Gaudi, I know that even inexpensive cables are good in sound quality.
Especially, expensive cables for maniacs tend to have a thick character, I feel (It might be my wrong impression since I haven't tried out so many cables). I think that a cable with a simple structure is better than expensive ones.
I don't care much about the materials of the cable, either. But OFC is used even for a cheap cable these days, so I will use a cable using OFC or better material. I think the material of the coating is more influential in sound qulity than the material of the core wire of the cable, but for now, it's not a firm belief.

Regardless of the balance type or unbalanced type, 2-core shielded cable are used for the line cables in order to prevent external noises from coming into the signal as much as possible.

The loudspeaker cables should be as short as possible in order to make the cable impedance very low. Thick cables have lower impedance per meter, but they tend to be expensive and not user-friendly. I prefer short and thin cables.

The cables used by Gaudi II is shown in the table below.

Connection Wire Length Sender end Receiver end Cable type
ADP --> Preamp Low capacitance
Unbalanced wire
1.5m RCA plug RCA plug The cable that comes with SL-1200GR
Stereo pair w/ earth wire
DAP (PC) --> Preamp OFC balanced wire
BELDEN 8412
1.5m RCA plug
w/ teflon insulator
RCA plug
w/ teflon insulator
Unbalanced type
Stereo pair
STB --> Preamp - - - - Wireless (Wi-Fi)
Preamp -->
Crossover network
OFC balanced wire
NEGLEX 2549
3m RCA plug
Neutrik NYS373-0
XLR plug Unbalanced type
Cold is grounded at the receiver end
Stereo pair
Crossover network
--> Tweeter/
squawker amp
OFC balanced wire
NEGLEX 2549
1.2m XLR plug XLR jack
Neutrik NYS373-0
Balanced type
HF-MF pair x2
Crossover network
--> Woofer amp
OFC balanced wire
NEGLEX 2549
1.2m XLR plug XLR jack Balanced type
Mono x2
Tweeter/squawker amp
--> Tweeter
OFC quad wire
Canare 4S6G
0.7m Spade connector Spade connectorl  
Tweeter/squawker amp
--> Squawker
OFC quad wire
Canare 4S6G
0.7m Spade connector Spade connector  
Woofer amp
--> Woofer
OFC quad wire
Canare 4S6G
0.7m Spade connector Spade connector The cable length is the length
from amp's terminal
to woofer's terminal.
PC ==> TV - - - - Wireless

 


AC Power Supply

[2021/02/23 revised] {This section has been rewritten (Ver.2.3)}

Outlet
Gaudi II - Mains connection Ver.2.3

The AC power supply arragement of Gaudi II is as shown in the figure on the right.

There are two wall sockets for audio in the room; one is located behind the audio rack AR-416 and the other is behind AR-421. Both are a dual socket outlet.
Each wall socket is connected to a dedicated line drawn from the dedicated breaker on the switch board. The line is not connected to other wall outlets and lighting equipment. The VVF2.0 cable is used for it. The line is wired by priority so that its length can be shortest.

All the sockets used in the wall socket and power strip are a socket for medical use (hospital grade).
The hospital-grade socket has low a contact resistance, which is one third of the standard socket. The model is Panasonic Electric Works WN1138.

The power distributor (TASCAM AV-P250S), which is plugged to the wall socket behind AR-421, provides AC power to the amplifiers.
The AV-P250S has 10 AC outlets, and they are grouped in three groups, A, B and C. In the power-on sequence, the group A is turned on first, followed by the gourp B, then the group C. In the power-off sequence, they are turned off in the reverse order.
The preamplifier and the crossover network are grouped in the group A and B; the power amplfires are in the group C. Thanks to the power-on/-off sequence, the noise suppresser for power-on/-off transition is necessary only for the power amplifiers.

Power cable

As for the power cable, I am not selective. I don't think the power cable is so influential to sound quality. I'd like highly reliable cables rather than audio grade cables.
For manufacturer products, I use the supplied cable as it is.

Every NOBODY-branded amplifier has a 3-wire power cable (one of the wires is an earth wire). The plug is a 3P type. The earth wire is connected to FG (frame ground or chassis ground).
In practical use, the plug is plugged into the outlet of the power distributor via a 2p-3p adapter. That makes the chassis of the NOBODY-branded amplifier disconnected from the earth, because the amplifier has superior insulation between the AC line and the DC power rails. When the amplifier is connected to other audio device, the potential of the FG becomes the same level as the FG of the other device. The FG level of every component in the system consequently becomes the same.
When the FG of the NOBODY-branded amplifier must be connected to the earth, the 2p-3p adapter must be removed.


Room Acoustics

[2021/02/24 revised] {This section has been rewritten (Ver.2.3)}

Gaudi II is installed in a room whose acoustics is so live (the reverberation time is so long).
In addition, the material of the inner wall and floor is so thin that they could be resonated. And, I know standing waves occur between the left and right walls.
Until recently, I've been installing sound absorber panels little by little to reduce the reverbration. But I've changed my strategy.

The reason is the huge cost needed for the sound absorbers. Some researcher says that the one third of the whole wall surfaces should be made of sound absorbing materials to reduce the reverbration significantly.
On the contrary, it is much cheaper and easier to use sound diffusers instead of sound absorbers. I've chosen this method. Though the room is live, it isn't too live for a listening room. I expect the room acoustics will be improved enough by only blocking frist reflections and standing waves.

Sound Diffusers

Some audio manufacturers are producing sound diffusers, and many of them are floor standing type. They would make the room smaller and look pushy from the listener's eyes.
I need ones that harmonize with the interior of my room in order to 'produce a cozy atmosphere', which is the concept of Gaudi II. I love to listen to music in the cozy room.

The sound diffusers will be installed to elimnate the first reflections.
(for the definition of 'first reflection', please see the glossary... here)

Though the first reflection from the floor is the most harmful for sound quality, it's easy to eliminate it. Japanese-style cushion placed on the floor between the loudspeaker and the listening position will do. The cushion must be stuffed with cotton, not sponge. It's so easy to put two cushions on the floor and put them away after use.

Rejection of 1st reflection - Floor Rejection of 1st reflection - Floor (top view)
1st reflection from floor: Cushions are used as a diffuser.
They are rather absorber than diffuser.
1st reflection from floor:
The location of the cushions

The second most harmful reflection is the first reflection from the side wall. It afversely affects localization of sound images.
The left wall has a window. The pane has a high reflection ratio. Multiple layers of thick curtains that cover the window are a good diffuser/absorber.
The right wall is a breast wall. The sonic waves go above it, and return after bouncing on the wall of the stairway. A sound diffuser (SD-423) will be installed on the breast wall. This diffuser also reduces the standing waves between the side walls.
A record cabinet is installed along the breast wall. Its front surface isn't flat and diffuse sonic waves.
Objet d'art whose surface is knobby will be hung on the wall of the stairway.

Rejection of 1st reflection - Left wall Rejection of 1st reflection - Right wall Rejection of 1st reflection - Right wall (top view)
1st reflection from left wall: Double thick curtains are usued. They are rather absorber than diffuser. 1st reflection from right wall: Sound diffuser SD-423 will be installed. 1st reflection from right wall: Record cabinet and Objet d'art also diffuse sounds.

Nothing special has to be done for the first reflection from the ceiling, because the ceiling is slanting. The slant ceiling itself functions as a diffuser. Besides, the ceiling made of natural woods and the surface is not flat.
The spot from where the first reflrection comes is so high (the elevation angle viewed from the loudspeaker is about 80 deg). The directivity of a horn-loaded speaker is narrow, so the SPL of the waves towards the ceiling is so low. The level of this first reflection can be ignored.

Rejection of 1st reflection - Ceiling Rejection of 1st reflection - Ceiling (side view)
Slant ceiling 1st reflection from ceiling

The reflections from behind can be ignored too.
The back wall is facing south and has a large window. The pane reflects sounds much. But the window is 3.3m away from the listening position. The path of the first reflection is 6.6m longer than that of the direct sound, and the reflection reaches the listening position 19msec later than the direct sound. I haven't found a good data that supports my idea, though, a delay of this extent seems not to distort the sound but give off reverberation. This reverberation caused by the room acoustics is unwelcome for a hi-fi system, but it's not significant for sound quality. Anyway, double thick curtains will be hung at the window to reduce the reflections as much as possible.

Other than the diffusers to reduce the first reflections, additional diffusers will be installed at spots where sounds are prone to gather.
The corner near the loudspeaker (the north-west corner of the room) is the spot. The audio rack AR-416 is placed there. It functions as a diffuser too, because it has air vents in the shelf and side boards so that the air passes through the rack in all directions. Besides, the components used in Gaudi II are all compact devices, so there are a lot of openings in the rack.

More diffusers will be fixed on the wall behand the loudspeakers, above the TV. I'm planning to make the diffusers by modifying picture frames. They will serve as garnishes too. I once considered framing lithographs in the picture frames, but pictures have too great presence. I hit upon with an idea that Japanese traditional paper (washi), world-famous craftwork of Japan, is suitable for this purpose. If images can be printed on ryoshi (washi for kana calligraphy) with an ink jet printer, I'd like to print the calligraphy of Kino Tsurayuki, my favorite poet/calligrapher. While Kana calligraphy has picturesque beauty, it is not as conspicuous as pictures. I believe it is suitable for the living room. If I could transcribe it myself, I'd do it. Unfortunately, I'm not so good at hand-writing.
The TV that is fixed on the wall is slightly tilted down. It is intended to reduce standing waves.
By the way, the reason way the TV is fixed on the wall is that the TV should be away from the baffles of the loudspeakers as far as possible. If the TV is located near the loudspeakers, sounds could be distorted by acoustic diffraction.

AR-416 Air AR-416 on the corner of the room Diffuser on the back wall Installation of TV
AR-416 Air: Audio rack w/ many openings AR-416 placed on the corner of the room Diffusers on the wall behind the loudspeakers TV fixed on the wall is slightly tilted down

Sound Absorbers

Many sound absorbers will be placed all over the room in order to reduce the excessive reverberation as much as possible.
The sound absorbers installed for Gaudi are continuously used.

The sound absorbers fixed on the walls near the highest part of the slant ceiling are the most effective ones. They were introduced for Gaudi. They are products of Inoac Corp. (distributed by Yahata Neji Corp.) and the product name is SoundGuard W. The sound localization becomes unstable without them.
The dimension of SoundGuard W that is fixed on the half wall facing the loudspeakers is 1800 x 900mm. The SoundGuard W on the side walls is 900 x 600mm.

Layout of sound absorbers Sound absorbers - Center and left Sound absorbers - Center and right
Positions of SoundGuard W SoundGuard W (center and left) SoundGuard W (center and right)

The corner of the room near the left speaker is the spot where sounds are prone to gather. Sound absorbers will be installed.
As of February, 2021, the type of the sound absorber hasn't been decided. It must be good-looking since it will be placed near the audio rack (AR-416).

Sound absorbers in the corner of the room
Sound absorbers on the corner Sound absorbers and audio rack

Other than the sound absorbers described above, there are small sound absorbers here and there in the room which were placed before Gaudi II project started. Each of them is not so effective, but rather effective as a whole. I'll use them continuously.

Sound absorbers - Opposite wall Sound absorbers - Above loudspeakers Sound absorbers - Near the loudspeakers
Sound absorbers on the south wall:Yoshio Gypsum Solaton Cube 12

Sound absorbers above the loudspeakers:
Rolls of bamboo blind w/ micron wool in it

Sound absorbers near the loudspeakers:
Paper pipe w/ micron wool in it

Other Acoustical Devices

Two acoustic panels are set up behind the loudspeakers (SS-309B). I made them myself in 2012. I'll continue using them.
These acoustic panels are designed to boost the bass response of SS-309B rather than to improve the room acoustics.
For the details, see the page on SS-309... here.

Acoustic panel Installation of Acoustic panels Installation of Acoustic panels (overview)
Acoustic panel: Yoshio Gypsum Solaton Cube 12 nailed on MDF board (18x910x1220mm) Acoustic panels are installed as they rest against the wall Acoustic panels are installed behind the loudspeakers


Supression of Vibration

There are two kinds of anti-vibration (suppression of vibration) methods.
The first one is to prevent vibration generated from the loudspeakers from being propagated to the other components (suppression of acoustic feedback). The second one is to prevent resonance of the floor, walls, furniture, etc (deadening).

Suppression of Acoustic Feedback

A special vibration-proofaudio rack is necessary for the record player, since it is very sensitive to vibrations.
For this purpose, I designed and built the audio rack AR-416 Air in 2017. Its performance was confirmed by measurement. I'll continue using it. For further details, please see the page on AR-416... here

Deadening

[2021/02/26 revised] {This section has been rewritten (Ver.2.3)}

The floor and walls of the room are so thin that reinforcement is necessary.
Especially, the floor is problematic. When a music souce that contains deep bass is being replayed, the floor vibrates to the extent I sense the vibration by my finger.

I tried out tile carpet; I put 16 pieces (50x50cm) of tile carpet on the floor. I found out the carpet supprssed vibration to a great extent.
This tile carpet has a 2mm-thick, rubber-like substrate. It seems that the substrate absorbs vibration.
I'll add four pieces of tile carpet. The total number will be 20 pieces. I think it's the best solution, since the tile carpet is inexpensive and easy to handle.

The audio racks, AR-416 and AR-421 (tentative), also function as a deadener. The both of them don't have feet and the whole bottom surface directly contacts the floor unlike commercially available audio racks. This will damp the vibration of the floor.

Tile carpet AR-416 on the floor AR-421 on the floor
20 pieces (50x50cm) of tile carpet on the floor AR-416 deadens floor AR-421(tentative) deadens floor

The devices fixed on the walls such as the TV and the sound absorbers are good deadeners.
A reinforcement board (12mm-thick plywood board) is fixed on the wall prior to fix the TV, because the inner wall made of plaster boards isn't strong enough to hold the TV. This reinforcement is effective to suppress vibration.
For the diffusers above the loudspeakers, the same kind of reinforcement will be used.
The sound absorbers at many spots on the walls are also a good deadener.

Reinforcement board for TV Reinforcement board for diffusers Sound absorber working as deadener
Reinforcement board for TV Reinforcement board for diffusers Sound absorber working as deadener

I'm planning to install more sound diffusers and absorbers on the walls.


Listening Layout and BGM Layout

[2021/02/26 added] {This section has been added (Ver.2.3)}

The room where Gaudi II is installed is a living room. The layout of furniture should be suitable for daily life and cozy to relax.
Usually, the layout is as shown in the figures below. This layout is termed 'BGM Layout'. 'BGM' stands for background music.

BGM layout (top view) BGM Layout (overview)
Usual layout (BGM Layout) Usual layout (BGM Layout)

This layout is suitable for watching TV during dinner or reading a book while listening to BGM.
This layout isn't good in terms of sound quality. The table blocks the sonic waves from the woofer. The sonic waves from the tweeter and squawker are distorted by acoustic diffraction caused by the table. There mustn't be anything between the loudspeakers and the listening position for the best sound quality.


For music appreciation, the layout should be changed as shown in the figures below. This layout is termed 'Listening Layout'.

Listening Layout (top view) Listening Layout (overview)
Layout for music appreciation (Listening Layout) Layout for music appreciation (Listening Layout)

The BGM layout is changed to the listening layout by following the steps below:

1. Move the table to the back of the listening position
2. Put the Japanese cushions on the floor between the loudspeakers and the listening position
3. Detach the grilles off the woofer box of SS-309B
4. Move the chair to the listening position
5. Turn off the ceiling light, or turn off the half of bulbs of the celing light
6. Turn on the bracket lights, and adjust the brightness

This steps includes not only improving sound quality by moving the table and detaching the grilles of the loudspeakers but also producing a good atmosphere for music appreciation.

The bracket lights use the only incandescent bulbs used in my house. I once tried out LED lamps that are compatible with dimmers, but they didn't get dim enough when I turned down the dimmer. So, I continue using the incandescent bulbs. I'm going to try out LED lamps once again in the future when the better ones are available.
There are four bracket lights in the room. One of them which is located near the audio rack AR-416 is also the light for the ADP. I can use the ADP even when the room is dark.

I'm going to get a table with casters, which is easy to move. If no such tables are available, I'll build it myself.

Bracket light illuminating ADP Table with casters
Bracket light illuminating ADP Table with casters

Coordinated Design

[2021/02/26 added] {This section has been added (Ver.2.3)}

Every component in an audio system (the room is one of the comoponts) should have appearance that harmonize with each other. That builds up integrity of the system.

I hit up with an idea, 'coordinated design'. This method is intended to enhance harmonization and unity among the components.
The scope of the coordinated design includes not only appearance but also electrical/mechanical compatibilty and unified user interface. Technologies that improve the overall sound quality like DVCS are also included.
('Coordinated design' and 'DVCS' are coined by Tonochi. For the definitions, see the glossary)

Under the coordinated design, multiple components are designed in parallel in the early stages of design phase: conceptual design, appearance design and specification design. In this way, the design of each component becomes unified naturally, and it's easy to commonalize parts and materials among the components.

The coordinated design also enhances productivity in build phase by using common parts and materials.

While designing one work, I didn't design another. It took me some two years from the start of conceptional design to the completion of the work. In this way, it was impossible to complete Gaudi II by the end of my life. I expect the coordinated design enables me to complete my Gaudi II.

I've already done some components' conceptual design. The following figures show them.

Concept of CC-218 Concept of MA-219 Concept of MV-222
CC-218: Control center (preamp) employing DVCS. Some parts are common to other amps

MA-219: Tweeter/squawker amp employing DVCS. Some parts are common to other amps MV-222: Master/slave volume unit employing DVCS. Some parts are common to other amps
Concept of AR-421
AR-421: Audio rack for power amps. Some parts are common to AR-416