Detailed System Design
2018/11/24 created
2022/03/19 updated
Here is the details of the system design of Gaudi II.
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 (Nov. 2017)
Ver.2.1: PC replaced DAP (May 2018)
Ver.2.2: DVCS has been introduced (Oct. 2018)
Ver.2.3: Digital crossover network and power distributor have been employed
(Jan. 2021)
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 which 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 |
| PC (DAP) |
- | - | Silent PC CPU: Core i5 3.1GHz or higher OS: Windows 10 |
Functions as DAP w/ DAC |
| DAC (DAP) |
- | - | USB DAC DSD5.6M, 192kHz/24bit |
Functions as DAP w/ PC |
| 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}
 |
 |
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.
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)}
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.
 |
 |
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.
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.
[2021/11/18 revised] {I've been assembling line cables without detailed design. And, my original
cables have been too extraordinary. Now I know deviation from the standard
doesn't lead to good SQ. And, more likely, it could cause trouble. I came
to prefer standard cables and select materials that meet requirement of
the cable. I don't stick to 2-core shield wire and RCA plug without shell
any more. I designed line cables with the new policy}
[Design document on line cable (LineCable_Design.pdf)]
[Assembly manual for line cable (LineCable_Assy.pdf)]
These documents include line cables for temporary use (CB12-15). And CB4
is a spare cable.
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.
[2021/11/19 revised] {I regard LS cables as a part of a loudspeaker. For the details of LS cables,
seethe page of SS-309}
The cables used by Gaudi II is shown in the table below.
| Connection | Ref Des (model #) |
Wire | Length | Sender end | Receiver end | Note |
|---|---|---|---|---|---|---|
| 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 | CB1 | Quad-core balanced Canare L-4E6S |
1.5m | RCA plug Canare F-10 |
RCA plug Canare F-10 |
Unbalanced type Stereo pair |
| Preamp --> DAR | CB2 | Quad-core balanced Canare L-4E6S |
2m | RCA plug Canare F-10 |
RCA plug Canare F-10 |
Unbalanced type Stereo pair |
| DAR --> Preamp | CB3 (Canare RC018) |
1-core unblanced (Canare GS-6) |
1.8m | RCA plug (Canare F-10) |
RCA plug (Canare F-10) |
Unbalanced type Stereo pair |
| STB --> Preamp | - | - | - | - | - | Wireless (Wi-Fi) |
| Preamp --> Crossover network |
CB5 (Canare RC03-B2) |
Quad-core balanced (Canare L-4E6S) |
3m | RCA plug (Canare F-10) |
XLR plug (Neutrik NC3-MXX) |
Unbalanced type Cold is grounded at the receiver end Stereo pair |
| Crossover network --> Tweeter/ squawker amp |
CB6, CB7 (Canare EC01) |
Quad-core balanced (Canare L-4E6S) |
1ｍ | XLR jack (Neutrik NC3-FXX) |
XLR plug (Neutrik NC3-MXX) |
Balanced type HF-MF pair x2 |
| Crossover network --> Volume unit |
CB8, CB9 (Canare EC015) |
Quad-core balanced (Canare L-4E6S) |
1.5m | XLR jack (Neutrik NC3-FXX) |
XLR plug (Neutrik NC3-MXX) |
Balanced type LF, Mono x2 |
| Volume unit --> Woofer amp |
CB10, CB11 (Canare RC018) |
1-core unblanced (Canare GS-6) |
1.8ｍ | RCA plug (Canare F-10) |
RCA plug (Canare F-10) |
Unbalanced 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. |
AC Power Supply
[2021/02/23 revised] {This section has been rewritten (Ver.2.3)}
Outlet
The AC power supply arragement of Gaudi II is as shown in the figure on the right.
There are two wall outlets 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 outlet 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 outlets 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 one by one 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.
 |
 |
| 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.
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| 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.
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| 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.
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| 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.
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| 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).
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
Variation in Layout
[2021/02/26 added] {This section has been added (Ver.2.3)}
[2021/11/20 revised] {This section has been rewritten}
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
'Daily Layout'.
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| Usual layout (Daily Layout) | Usual layout (Daily Layout) |
This layout is suitable for watching TV during dinner or reading a book
while listening to BGM.
This layout isn't the best in terms of sound quality. The sonic waves from
the loudspeakers are distorted by acoustic diffraction and reflection caused
by the table. If the system were monaural and using only one loudspeaker,
the distortion wouldn't matter. But it matters for the stereo system. The
quality in stereo imaging could be impaired.
For music appreciation, the layout should be changed as shown in the figures below. This layout is termed 'HD Layout'. The HD stands for high definition.
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| Layout for music appreciation (HD Layout) | Layout for music appreciation (HD Layout) |
The Daily Layout is changed to the HD Layout by following the steps below:
1. Move the table and the sofa to the back of the listening position
2. Close the curtain of the left-hand window
3. Put the Japanese cushions on the floor between the loudspeakers and
the listening position
4. Detach the grilles off the woofer box of SS-309B
5. Move the chair to the listening position, and put the small table in
front of the chair and the kayboard/mouse on it
6. Turn off the ceiling light, or turn off the half of bulbs of the celing
light
7. 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 fixed casters onto the feet of the table so that the table can be moved easily.
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| Bracket light illuminating ADP | Table with casters |
I devised some other variations of HD Layout for guests. The purpose of
Gaudi II is not only enjoying music by myself but entertaining my friends
with music. Lately, I'm getting to focus more on the latter. I want my
guests to enjoy music in the best SQ, so the new layouts are based on HD
Layout.
I named them 'Guest Layouts'.
Guest Layout 1 is for a single guest. The chair is placed at the listining position.
Guest Layout 2 is for 2 to 3 guests. The sofa is used instead of the chair.
A small stool and the small table for keyboard/mouse are placed beside
the listening position. I operate Gaudi II at the position.
Using the chair is better in SQ, though, if the guest sits on the middle of the sofa and doesn't lean on the backrest, the same level of SQ is given.
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| Guest Layout 1: Chair at the listening position | Guest Layout 1: Chair at the listening position |
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| Guest Layout 2: Sofa at the listening position | Guest Layout 2: Sofa at the listening position |
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.
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| 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 |
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| AR-421: Audio rack for power amps. Some parts are common to AR-416 |