Wildeboer FK90 User manual

User Manual 5.02 (2016-10) 1Subject to change
Maintenance-free
FK90 re dampers - series FK120 -
■ Heights up to 1000 mm
■ Fire resistance period up to 120 minutes
Fire classication: EI 30/60/90/120 (ve- ho, i ↔ o) S C10ooo
■ Hygiene certicate
■ Environmental Product Declaration according to ISO 14025 and EN 15804
The German original version of this document shall prevail.

User Manual 5.0-2 (2016-10) 2 Subject to change
Series FK120
FK90 re dampers
Features and characteristics
Break-resistant damper blade
for vertical or horizontal installation,
with galvanized metal frame and attached
elastomer lip seal
- frictionless sealing -
- replaceable -
Options:
Metal cover made of galvanized steel
Metal frame made of 1.4301 stainless steel
Metal frame and metal cover made of
1.4301 stainless steel
All-round enclosed
thermal release elements
70°C, 95°C or 100°C
Option:
Corrosion-resistant release element 70°C
Large free cross-section
Maximum volume ows
Minimum pressure drop
Extremely low sound
power level
Connection holes
for proles from 20 mm in height
Two control openings
(inspection openings)
for viewing both sides of the
damper blade
Thermal-mechanical
release mechanism
for manual single handed operation
Option:
Electric actuators, also explosion-protected
⇒ see page 5
Single-piece sheet steel casing
galvanized - pressure-joined - extremely
robust, airtight
Leak tightness class C according to EN 1751
Option: Epoxy resin powder coating
Dimensions B and H in 5-mm increments
Nominal width B: 200 mm to 1500 mm
Nominal height H: 200 mm to 1000 mm
Lengths: 400 mm and 500 mm
Fully enclosed:
• Operation unit
• Release mechanism
•Release element

User Manual 5.02 (2016-10) 3Subject to change Series FK120
FK90 re dampers
Description
Increased corrosion protection through powder coating and stainless steel
Casings coated internally and externally are recommended:
• metal frames of the damper blades made of 1.4301 stainless steel and
– if present – the metal cover as well
• thermal-mechanical release mechanisms with corrosion-resistant (coated) release element 70°C.
These combinations allow additional corrosion protection for harsh service conditions.
FK90 re dampers
•
Meet the hygiene requirements according to VDI 6022-1, DIN 1946-4 and DIN EN 13779
•Do not promote the growth of microorganisms 1) (fungi, bacteria).
This reduces the risk of infection for people and also the necessary
cleaning and disinfection work!
•Are resistant to disinfectants 2)
•Are suitable for use in hospitals and similar facilities!
•
Permanently perform their function under high corrosion condi-
tions.Tested according to EN 15650, annex B with 20% saline solution.
1) The corresponding resistance of the materials to fungi and bacteria was veried by testing the microbial metabolic potential under
DIN EN ISO 846 for all materials in the FR90 re dampers.
2) The resistance to disinfectants of the materials in the FR90 re dampers was tested with the disinfectant groups of active ingredients alcohol and
quaternary compounds. These disinfectants are on the list by the Robert Koch Institute, and were used in accordance with the specications in
the list of disinfectants by the Disinfectants Commission in the German Association for Applied Hygiene (VAH). It has been veried that FR90 re
dampers can withstand normal use of disinfectants and disinfection methods.
Pressure-joined casing with all-round single-piece design,
made of galvanized sheet steel, leak tightness class C
according to EN 1751. Formed connection anges, outer
beading and tapered inner beading ensure stability, free-
dom of damper blade movement, minimum pressure drop
and low noise level.
Option: Casing with epoxy resin powder coating.
Replaceable damper blade made of high-temperature-re-
sistant, corrosion-resistant and abrasion-proof calcium
silicate with galvanized metal frame and folded, wear-re-
sistant elastomer lip seals.
Options: Damper blade with metal frame made of 1.4301
stainless steel/damper blade with metal cover made of
galvanized steel/damper blade with metal cover made of
1.4301 stainless steel.
Fully enclosed, maintenance-free slider crank transmis-
sion in the area of the casing wall, as a self-locking drive
mechanism for break-proof torque transmission. Sealed
drive axles made of stainless steel, with red metal bea-
rings.
Thermal release mechanisms for 70°C, 95°C and 100°C
nominal temperature. The operation units can be actua-
ted manually or electrically.
⇒ see pages 4 and 5
Release mechanisms, operation units and electric actu-
ators are enclosed and tted with a spring return. They are
maintenance-free, can be connected in a form-locking or
force-tting manner, are easy to replace and can be easily
retrotted as required.
For installation with horizontal or vertical damper blade
axles. Air inow from any connection side. Connection to
ventilation ducts made of non-combustible or combustible
materials, including protective grilles.
Option: Additional openings on the operation side in the
casing.⇒see page 14
Widths B: 200 mm to 1500 mm | 200 mm to 1000 mm
Heights H: 200 mm to 800 mm | 200 mm to 1000 mm
Lengths: 400 mm and 500 mm
The respective width and height dimensions are available
in 5-mm increments and can be combined. ⇒ see page 14
For installing in rigid walls, ceilings and in metal
stud walls. ⇒ see pages 11 and 12
Maintenance-free FK90 re dampers according to EN 15650
Fire classications: EI 30/60/90/120 (ve- ho, i ↔o) S C10ooo ⇒see page 11
Declaration of performance: DoP no.: CPR/FK120/002
EU Declaration of Conformity according to Directive 2014/34/EU
for use in potentially explosive atmospheres
Environmental Product Declaration ISO 14025, EN 15804: EPD-WWB-20130081-IBA1-DE

User Manual 5.0-2 (2016-10) 4 Subject to change
Series FK120
FK90 re dampers
Release mechanisms and actuators (1)
Thermal-mechanical release mechanism - standard -
with 70°C release element.
Option: with coated 70°C release element.
Option: with coated 95°C release element.
Option: with limit switch
E Changeover with gold-plated contacts for 5 A
at 250 V AC or 24 V DC; IP67;
1 m silicone-free connection cable, 3 x 0.34 mm².
One or two can be plugged in for the CLOSED and/or OPEN
position indicator; instead of blind caps.
Enclosed relea-
se element
can be replaced
from the front.
Blind cap can
be replaced with
the OPEN limit
switch.
Manual release
‘Red button’
Lever for opening the
re damper.
Inserted limit
switch CLOSED.
FK90 re dampers, series FK120, are tted with maintenance-free thermal-mechanical release mechanisms or with
thermal-electrical release mechanisms on the spring return actuators. Release occurs at a nominal temperature of
70°C. Coated release elements provide increased corrosion protection. Release mechanisms with a release element
for nominal temperatures of 95°C and 100°C are provided for warm air heating systems. The requirements for use in
ventilation systems for "cold smoke extraction" are country-specic.
Electric spring return actuators also close the re dampers if the supply voltage is interrupted. They reopen the re
dampers as soon as the voltage is present again.
Release mechanisms and operation units can be replaced on site!
Release mechanism and remote release with lifting solenoid
Option: with additional remote release based on the:
closed circuit principle. The re dampers must be opened
manually, and close after the electrical supply voltage is inter-
rupted.
GU24 with magnetic clamp 24 V DC; 1.6 W;
100% duty cycle; IP42.
WU220 with magnetic clamp 230 V AC; 4 VA;
100% duty cycle;IP42.
Open circuit principle. The re dampers must be opened
manually, and close by means of electrical or pneumatic stimu-
lus.
G24 with lifting solenoid 24 V DC; 3.5 W; 100% duty
cycle; IP42.
W220 with lifting solenoid 230 V AC; 5.5 VA; 100% duty
cycle; IP42.
P with lift cylinder 4 to 8 bar.
P2 with lift cylinder 1.2 to 8 bar.
Option: Electric spring return actuator - standard -
with 70°C release element; IP54.
M220-9/V 230 V AC; 9.2 VA; Imax ≤ 2 ms = 0.27 A.
M24-9/V 24 V AC/DC; 6.1 VA / 3.5 W;Imax ≤ 2 ms = 3.5 A.
Runtime: Opening ≈60 s, closing ≈21 s.
CLOSED/OPEN position indicators via limit switches for
5 A at ≤ 240 V AC.
Halogen-free connection cable; 0.9 m long; 2 x 0.75 mm²
and 6 x 0.75 mm². The AMP connector plugs are
detachable.
Option: with 100°C release element.
Enclosed release element

}
User Manual 5.02 (2016-10) 5Subject to change Series FK120
Option: Electric spring return actuator
with 70°C release element and terminal box.
EM-1 10 Nm
EM-2 15 Nm
RM-1 10 Nm
Power consumption up to 20 W including heating;
Irated ≤0.7 A; Imax ≤
1 ms
≈2.5 A
Runtime: Opening ≈30 s, closing ≈10 s.
CLOSED and OPEN position indicators via limit swit-
ches for ≤ 3 A at 24 V AC/DC and ≤ 0.25 A at 250 V
AC/DC; at least 5 V, 10 mA.
The 12 x 0.5 mm² halogen-free connection cable must be wired
in the terminal box! All of the contained voltages must be the
same!
Option: Electric spring return actuator
with 70°C release element; IP54.
M220-7 230 V AC; 7 VA/6 W; Imax ≤
10 ms
= 0.15 A.
M24-7 24 V AC/DC; 7 VA/5 W; Imax ≤
5 ms
= 5.8 A.
Runtime: Opening 40 to 75 s, closing ≈20 s.
CLOSED/OPEN position indicators via limit switches
for 0.5 A at ≤ 250 V AC or for 1 mA up to 3 A at 5 up to
250 V DC.
Halogen-free connection cable; 1 m long; 2 x 0.75 mm²
and 6 x 0.75 mm². The AMP connector plugs are
detachable.
Option: with 95°C release element.
Enclosed release element
The actuators can be rotated into suspen-
ded and vertical positions on site.
Terminal box
FK90 re dampers
Release mechanisms and actuators (2)
Thermal-mechanical release mechanism
with 70°C release element.
Option: with coated 70°C release element.
Option: with explosion-protected limit switch
E-Ex with normally open contact and normally closed
contact for 6 A at ≤ 250 V AC
or 0.25 A at ≤ 230 V DC; IP65;
2 m connection cable 4 x 0.75 mm².
One or two can be attached for the CLOSED and/or OPEN
position indicator.
- designs
Building area where a dangerous, potentially explo-
sive atmosphere may occur in normal operation...
... as a mixture of air and combustible gases, mists or vapours... ... in the form of a cloud of combustible dust contained in the air...
... occasionally ... temporarily or not at all. ... occasionally ... temporarily or not at all.
Zone 1 2 21 22
Identication of the re damper II 2 G c IIc T6/T5 II 3 G c IIc T6/T5 II -/2 D c T80°C/T95°C II -/3 D c T80°C/T95°C
Thermal-mechanical release mechanism with or
without explosion-protected limit switch X X *)X X *)
Motor drive EM-1 or EM-2 X X *)X X *)
RM-1 - X - X
Ambient temperatures: -20°C … +40°C for T6 and T80°C/-20°C … +50°C for T5 and T95°C *) Can also be used in this zone!
24 to 240 V AC/DC; IP66.
Use of explosion-protected designs
Enclosed release element
Enclosed relea-
se element

Release element
Lip seal
Damper
blade
Manual lever
Manual release
Casing
Control opening
Thermal-
mechanical
release mechanism
Limit switch
E-CLOSED (optional)
Manual release
Operation unit
Limit switch
E-OPEN (optional)
Closing spring
Control opening
Enclosed transmission
Operation side down
Operation side up
Connection flanges
only, if
only, if
Connection holes
User Manual 5.0-2 (2016-10) 6 Subject to change
Series FK120
Damper blade
• Operation side: K
•Non-operation side: K400, K500
L = 400 and L = 500
Height-independent excess lengths T U J
Thermal-mechanical release
mechanism 95 - -
with: • W220, WU220 120
 • G24, GU24 120 - -
  •P, P2 105 - -
  •E-Ex limit switch 105 - -
M220-9/V, M24-9/V 90 - -
M220-7, M24-7 145 40 -
EM-1, EM-2, RM-1 245 150 J3
Thermal-mechanical release mechanisms
are labelled with V1, V2, V4 and are mounted
based on the width B and height H of the re
dampers.
These size-dependent allocations must not
be changed on site!
H J3 K K400 K500
200 170 - - -
225 160 - - -
250 145 - - -
275 135 - 4 -
300 120 - 17 -
325 110 - 29 -
350 95 - 42 -
375 85 - 54 -
400 70 - 67 -
450 45 - 92 -
500 20 - 117 17
550 - - 142 42
600 - 7 167 67
650 - 32 192 92
700 - 57 217 117
750 - 82 242 142
800 - 107 267 167
850 - 132 292 192
900 - 157 317 217
950 - 182 342 242
1000 - 207 367 267
Additional space must be provided for assembly, electrical connections
and servicing; observe the cable entry points!
In addition to the "T" measurement, it is recommended that a distance of 400
mm be kept from adjacent walls, ceilings or other re dampers, in order to ensu-
re that the release mechanisms and actuators can be accessed for operational
purposes.
Connection anges are tted with connection holes. If additional holes are requi-
red for duct connection, these can be added on site!
H/B ≤400 > 400 to 750 > 750
≤300 V2 V4 V1
> 300 to 1000
FK90 re dampers
Data sheet (1) Dimensions
Maximum excess lengths of mechanical and electrical equipment parts.
Actuators
U horizontal (delivery condition)
J rotated to vertical or suspended position:
J3 EM-1, RM-1, EM-2

User Manual 5.02 (2016-10) 7Subject to change Series FK120
FK90 re dampers
Data sheet (2) Free cross-sections, weights
B/H 200 225 250 275 300 350 400 450 500 550 600 650 700 750 800 900 1000
200 0.018 0.022 0.026 0.030 0.034 0.041 0.049 0.057 0.065 0.073 0.080 0.088 0.096 0.104 0.112 0.127 0.143
225 0.021 0.026 0.030 0.035 0.039 0.048 0.057 0.066 0.075 0.084 0.093 0.102 0.111 0.121 0.130 0.148 0.166
250 0.024 0.029 0.034 0.039 0.044 0.055 0.065 0.075 0.086 0.096 0.106 0.117 0.127 0.137 0.147 0.168 0.189
275 0.027 0.033 0.038 0.044 0.050 0.061 0.073 0.085 0.096 0.108 0.119 0.131 0.142 0.154 0.165 0.188 0.212
300 0.030 0.036 0.042 0.049 0.055 0.068 0.081 0.094 0.106 0.119 0.132 0.145 0.158 0.170 0.183 0.209 0.234
325 0.033 0.040 0.047 0.054 0.061 0.075 0.089 0.103 0.117 0.131 0.145 0.159 0.173 0.187 0.201 0.229 0.257
350 0.035 0.043 0.051 0.058 0.066 0.081 0.097 0.112 0.127 0.143 0.158 0.173 0.188 0.204 0.219 0.250 0.280
375 0.038 0.047 0.055 0.063 0.071 0.088 0.105 0.121 0.138 0.154 0.171 0.187 0.204 0.220 0.237 0.270 0.303
400 0.041 0.050 0.059 0.068 0.077 0.095 0.112 0.130 0.148 0.166 0.184 0.201 0.219 0.237 0.255 0.290 0.326
450 0.047 0.057 0.067 0.078 0.088 0.108 0.128 0.149 0.169 0.189 0.209 0.230 0.250 0.270 0.291 0.331 0.372
500 0.053 0.064 0.076 0.087 0.098 0.121 0.144 0.167 0.190 0.212 0.235 0.258 0.281 0.304 0.326 0.372 0.418
550 0.059 0.071 0.084 0.097 0.109 0.135 0.160 0.185 0.210 0.236 0.261 0.286 0.312 0.337 0.362 0.413 0.463
600 0.064 0.078 0.092 0.106 0.120 0.148 0.176 0.203 0.231 0.259 0.287 0.315 0.342 0.370 0.398 0.454 0.509
650 0.070 0.085 0.101 0.116 0.131 0.161 0.191 0.222 0.252 0.282 0.313 0.343 0.373 0.404 0.434 0.494 0.555
700 0.076 0.092 0.109 0.125 0.142 0.174 0.207 0.240 0.273 0.306 0.338 0.371 0.404 0.437 0.470 0.535 0.601
750 0.082 0.100 0.117 0.135 0.152 0.188 0.223 0.258 0.294 0.329 0.364 0.400 0.435 0.470 0.505 0.576 0.647
800 0.088 0.107 0.125 0.144 0.163 0.201 0.239 0.277 0.314 0.352 0.390 0.428 0.466 0.503 0.541 0.617 0.692
850 0.093 0.114 0.134 0.154 0.174 0.214 0.255 0.295 0.335 0.376 0.416 0.456 0.496 0.537 0.577 0.658 0.738
900 0.099 0.121 0.142 0.163 0.185 0.228 0.270 0.313 0.356 0.399 0.442 0.484 0.527 0.570 0.613 0.698 0.784
950 0.105 0.128 0.150 0.173 0.196 0.241 0.286 0.332 0.377 0.422 0.467 0.513 0.558 0.603 0.649 0.739 0.830
1000 0.111 0.135 0.159 0.183 0.206 0.254 0.302 0.350 0.398 0.445 0.493 0.541 0.589 0.637 0.684 0.780 0.876
1050 0.117 0.142 0.167 0.192 0.217 0.268 0.318 0.368 0.418 0.469 0.519 0.569 0.620 0.670 0.720
1100 0.122 0.149 0.175 0.202 0.228 0.281 0.334 0.386 0.439 0.492 0.545 0.598 0.650 0.703 0.756
1150 0.128 0.156 0.184 0.211 0.239 0.294 0.349 0.405 0.460 0.515 0.571 0.626 0.681 0.737 0.792
1200 0.134 0.163 0.192 0.221 0.250 0.307 0.365 0.423 0.481 0.539 0.596 0.654 0.712 0.770 0.828
1250 0.140 0.170 0.200 0.230 0.260 0.321 0.381 0.441 0.502 0.562 0.622 0.683 0.743 0.803 0.863
1300 0.146 0.177 0.208 0.240 0.271 0.334 0.397 0.460 0.522 0.585 0.648 0.711 0.774 0.836 0.899
1400 0.157 0.191 0.225 0.259 0.293 0.361 0.428 0.496 0.564 0.632 0.700 0.767 0.835 0.903 0.971
1500 0.169 0.205 0.242 0.278 0.314 0.387 0.460 0.533 0.606 0.678 0.751 0.824 0.897 0.970 1.042
B/H 200 225 250 275 300 350 400 450 500 550 600 650 700 750 800 900 1000
200 10 11 11 12 12 13 14 15 15 16 17 18 19 19 20 22 24
225 11 11 12 12 13 13 14 15 16 17 18 19 19 20 21 23 24
250 11 12 12 13 13 14 15 16 17 17 18 19 20 21 22 24 25
275 12 12 13 13 13 14 15 16 17 18 19 20 21 22 23 24 26
300 12 13 13 13 14 15 16 17 18 19 20 21 22 22 23 25 27
325 12 13 13 14 14 15 16 17 18 19 20 21 22 23 24 26 28
350 13 13 14 14 15 16 17 18 19 20 21 22 23 24 25 27 29
375 13 14 14 15 15 16 17 19 20 21 22 23 24 25 26 28 30
400 14 14 15 15 16 17 18 19 20 21 22 23 24 26 27 29 31
450 15 15 16 16 17 18 19 20 21 23 24 25 26 27 28 30 33
500 15 16 17 17 18 19 20 21 23 24 25 26 27 29 30 32 35
550 16 17 17 18 19 20 21 23 24 25 26 28 29 30 31 34 36
600 17 18 18 19 20 21 22 24 25 26 28 29 30 32 33 36 38
650 18 19 19 20 21 22 23 25 26 28 29 30 32 33 35 37 40
700 19 19 20 21 22 23 24 26 27 29 30 32 33 35 36 39 42
750 19 20 21 22 22 24 26 27 29 30 32 33 35 36 38 41 44
800 20 21 22 23 23 25 27 28 30 31 33 35 36 38 39 42 46
850 21 22 23 24 24 26 28 29 31 33 34 36 38 39 41 44 48
900 22 23 24 24 25 27 29 30 32 34 36 37 39 41 42 46 49
950 23 24 25 25 26 28 30 32 33 35 37 39 41 42 44 48 51
1000 24 24 25 26 27 29 31 33 35 36 38 40 42 44 46 49 53
1050 24 25 26 27 28 30 32 34 36 38 40 42 43 45 47
1100 25 26 27 28 29 31 33 35 37 39 41 43 45 47 49
1150 26 27 28 29 30 32 34 36 38 40 42 44 46 48 50
1200 27 28 29 30 31 33 35 37 39 42 44 46 48 50 52
1250 28 29 30 31 32 34 36 38 41 43 45 47 49 51 54
1300 28 30 31 32 33 35 37 40 42 44 46 49 51 53 55
1400 30 31 32 34 35 37 40 42 44 47 49 51 54 56 58
1500 32 33 34 35 37 39 42 44 47 49 52 54 57 59 62
Free cross-sections Afree [m²]
Weights [kg] for the standard version
To be added on:
• Damper blade with
metal cover 10%
•Actuators:
M220-9/V; M24-9/V 2 kg
M220-7; M24-7 3 kg
EM-1; EM-2; RM-1 5 kg

6
5
55
3
2
120 30 50 70
7
200
250 300 350 400 500 600 700 800 1000 1200 1500
Height H [mm]
1
Pressure drop p [Pa]
S
3
4
8
10
12
2
Flow velocity v [m/s]
A
200
250
300
350
400
800
500
600
Width B [mm]
200
250
300
350
400
500
600
700
800
Height H [mm]
Volume flow V [m³/h]
225 275
200
300
400
600
800
1000
2000
3000
4000
6000
8000
10000
20000
30000
40000
50000
150
900
1000
900
1000
ooo050 40ooo30ooo20ooo10ooo
0
2500
3000
2000
1000
1500
500
]aP[kcurdsbeirteB
1400
1300
mm0051=B
1200
Metal damper blade B = 1500 mm
1400
v > 12 m/s
A
Volume flow [m³/h]
v > 12 m/s
A
Operating pressure
User Manual 5.0-2 (2016-10) 8 Subject to change
Series FK120
FK90 re dampers
Dimensioning (1) Pressure drop with ventilation duct connection on both sides
FK90 re dampers can be used in the area of the nomograms. With large dimensions, restrictions
should be taken into account depending on operating pressure and volume ow.
Example: At an operating pressure of 1500 Pa and a width of 1400 mm, the permissible volume ow is 26475 m³/h. This may increase if
the width is smaller or if the damper blade has a metal cover, or if an electric drive version is being used.

6
5
55
3
2
120 30 50 70
7
200
250 300 350 400 500 600 700 800 1000 1200 1500
Height H [mm]
1
Pressure drop p [Pa]
S
3
4
8
10
12
2
Flow velocity v [m/s]
A
200
250
300
350
400
800
500
600
Width B [mm]
200
250
300
350
400
500
600
700
800
Height H [mm]
Volume flow V [m³/h]
225 275
200
300
400
600
800
1000
2000
3000
4000
6000
8000
10000
20000
30000
40000
50000
150
900
1000
900
1000
User Manual 5.02 (2016-10) 9Subject to change Series FK120
FK90 re dampers
Dimensioning (2) Sound power level with ventilation duct connection on both sides
Example: ⇒ see page 10

ve sound power levelitaleR ]Bd[L
-20
+10
+5
0
-5
-15
-25
125 250 500 1000 2000 4000 8000
Octave mid frequency [Hz]
+15
-10
Flow velocity v [m/s]
A
63
-30
2
4
6
810
12
2
4
6
8
12
v [m/s]
A
User Manual 5.0-2 (2016-10) 10 Subject to change
Series FK120
FK90 re dampers
Dimensioning (3) Relative sound power level, examples, nomenclature
Relative sound power level
Example:
V = 4000 m³/h
B = 500 mm
H = 300 mm
AA = 0.150 m²
Afree = 0.098 m²
Dps = 29 Pa
v
A = 7.4 m/s
LWA = 47 dB(A)
Sound power level LW-Oct for the octave mid frequencies
f [Hz] 63 125 250 500 1000 2000 4000 8000
LWA [dB(A)] 47 47 47 47 47 47 47 47
DL7.4 m/s [dB] 5 6 1 -3 -6 -9 -15 -22
LW-Oct [dB] 52 53 48 44 41 38 32 25
B [mm] Width
H [mm] Height
AA [m²] Inow cross-section B x H
Afree [m²] Free cross-section
V [m³/h] Volume ow
vA [m/s] Flow velocity in inow cross-section
Dps [Pa] Static pressure drop
LWA [dB(A)] A-weighted, area-corrected sound power level
LW-Oct [dB] Octave sound power level LW-Oct = LWA + DL
DL [dB] Relative sound power level to LWA
f [Hz] Octave mid frequency
Nomenclature