CKT-TF1225 System

The CKT-TF1225 system is a medium sized 2-way speaker design suitable for stand
or floor mounting. This system comprises the TF1225 12”(300mm) bass/midrange
driver and CDX1-1745 compression driver fitted with the H1-9040 horn. It is a
versatile and portable system that offers good performance when used either stand-
alone or with a sub-woofer. The 90x40 horn ensures good coverage over a wide
area.

Components
System Bass Driver Compression Horn Crossover
Driver
CKT-TF1225 TF1225 CDX1-1745 H1-9040 CX-TF1225

CELESTION CKT-TF1225
CELESTION CKT-TF1225
CELESTION CKT-TF1225
CELESTION CKT-TF1225
Measured Data

On-Axis Frequency Response (2m measurement normalized to 2.83V/1m)

Input Impedance

CELESTION CKT-TF1225
 Horizontal Dispersion: on-axis(red), 30deg(green), 60deg(yellow)
(2m measurements normalized to 2.83V/1m)

Vertical Dispersion: on-axis(red), +10deg(green), -10deg(yellow)

(1m measurements normalized to 2.83V)

Directivity: -6dB beamwidth

Frequency/Hz 500 800 1k 2k 5k 8k 10k 15k

Beamwidth (deg) 150 90 120 90 66 50 40 30

CELESTION CKT-TF1225
Specifications:
Format: 2-way system
Drivers: TF1225, CDX1-1745 (H1-9040)
Sensitivity: 97.5dB (2.83V/1m)
Input Impedance: 8ohms (nominal), 6.5 ohms (minimum)
Rated System Power: 400W (EIA), 1200W (peak)
LF Extension: 74Hz (-3dB), 56Hz(-10dB)
Crossover Frequency: 1.9kHz
Maximum Output Level: 123dB (Continuous), 129dB (Peak)
LF Unit Power Rating: 250W (AES)
Horn Directivity: 90deg H x 40deg V
High Pass Filter: 65-75Hz
Internal Volume: 48L
Port Tuning Frequency: 70Hz
Port Dimensions: 2 x (Diameter 100mm x Length 60mm)
Port Options: smaller port: 2 x (95Dx49L) / larger port: 2 x (105Dx72L)
Dimensions: 654 x 388 x 320mm (H x W x D)

Crossover Network
The crossover schematic and component listing is shown below, along with a
suggested component layout. The network provides a second order roll off for the
bass unit and third order for the compression driver. This results in a fourth order
acoustic crossover between the units.

L1 can be either an air core or iron(solid) cored inductor. For an iron core the
saturation current needs to be at least 8A and/or it should have a power rating of at
least 250W. The capacitors should be polypropylene types for best performance. If
the poly-switch is included it should be situated at least 30mm or so away from R1
and L1 to avoid its local ambient temperature being raised by those components if
and when they get warm.

Inductors should, in general, be positioned with their core axes at right angles and
with at least 20mm of physical space between them to avoid magnetic interactions.
However, they can be positioned with their axes parallel provided they are at the
same height and there is sufficient separation between them. This separation will
depend on the inductor size, core type and winding geometry but an axis separation
of 125mm should prevent any significant interactions between typical inductors.

The crossover components can be mounted onto a 6mm wooden board, hard-wired
and secured with hot-melt and then with cable ties fitted through holes drilled through
the board. The board can be screwed onto the inner surface of the cabinet, ideally
with 6mm spacers to prevent rattling. Cables should be connected in a way that does
not stress the component lead-out wires, tag panels or terminal strips can be used to
connect the lead-wires to the circuit. The cable conductor cross-sectional areas
should be at least 1.5 square mm.

CELESTION CKT-TF1225
 L1
I/P+ LFO/P+ Component Listing- CX-TF1225
C1
R1- 1.5 Ohms/ 20W
R2 - 12 Ohms/ 20W
L1- 1.8 mH/ dcr <0.5 Ohms(Air Core)
R1 dcr <0.25 Ohms(IronCore)
L2 - 0.82 mH/ dcr<0.6 Ohms(Air Core)
C1- 15 uF/ 250V/ DF<0.1%
I/P- LFO/P- C2 - 1.0 uF/ 250V/ DF<0.1%
C3- 10 uF/ 250V/ DF<0.1%
C4 - 2.2 uF/ 250V/ DF<0.1%
C3 P1- Polyswitch(optional): 1.1A(H)/ 2.2A(T)
P1 R2 C2
HFO/P+

C4
L2

HFO/P-

Crossover Schematic: CX-TF1225

I/P-/LF-/HF-
R1

C1
L2
HF+
LF+ L1
C2 I/P+
C3/C4
P1 R2

Suggested crossover component layout (Air core L1)

CELESTION CKT-TF1225
 Cabinet Design – ‘V’-backed

30 DEG.

BOTTOMVIEW

A
148,5 148,5
C
358 64 260

34

40
88,5

165
88,5
8 HOLESASSHOWN

4 HOLESEQUALLY
SPACEDON297 PCD

624
3
O 28

310
B B'

PORTHOLESCENTRES

269,5

92
80,5

81,5
A' C'
BACKVIEW SECTIONC-C' SECTIONA-A'
FRONTVIEW

CKT-TF1225 'V'-BACKED CABINET

15MMBIRCHPLY 224
ALLDIMSINMM
50
187

128

50

SECTIONB-B'

Construction Notes:
All joints should be glued and screwed.
T-Nuts and fixing bolts are recommended as a means of fixing the units.
Ensure that there are no air leaks in the cabinet apart from the ports – foam gasket
strip to be used in the mounting of drivers, stand attachment (top-hat) and terminal
panel.
Internal cables should be carefully positioned to avoid any rattling.
18mm MDF can be used instead of 15mm Birch plywood provided the internal
volume is maintained.

CELESTION CKT-TF1225
Cabinet Design – Square box (56L)

BOTTOMVIEW

148,5 148,5
C
358 64 260

34

40
88,5

165
88,5
8 HOLESASSHOWN

4 HOLESEQUALLY
SPACEDON297 PCD

624
83
O2

310
B B'

PORTHOLESCENTRES

269,5

92
80,5

81,5 A' C'

BACKVIEW SECTIONC-C' SECTIONA-A'
FRONTVIEW

CKT-TF1225 SQUARE CABINET

15MMBIRCHPLY
ALLDIMSINMM
250

50
115

50

SECTIONB-B'

Construction Notes:
All joints should be glued and screwed.
T-Nuts and fixing bolts are recommended as a means of fixing the units.
Internally mounted battens can be used as a means of securing the front and back
panels.
Ensure that there are no air leaks in the cabinet apart from the ports – foam gasket
strip to be used in the mounting of drivers, stand attachment (top-hat) and terminal
panel.
Internal cables should be carefully positioned to avoid any rattling.
18mm MDF can be used instead of 15mm Birch plywood provided the internal
volume is maintained.

CELESTION CKT-TF1225
Arrangement of acoustic damping material within the cabinet
The damping material should be 50mm thick acoustic wadding. Piece A is folded
double and looped over the compression driver horn. Piece B is folded double and
placed behind the bass unit. Care should be taken that the material is not allowed to
touch the cone of the bass unit or obstruct the ports. A=160x800mm,
B=200x1000mm

Methods for determining the balance point of the cabinet

Before deciding on the exact position of the top hat stand attachment, it is first
necessary to determine the balance point of the cabinet. Below are two methods that
can be used for this purpose. It is important that this process is performed on the
assembled cabinet. If it is desired that the cabinet should have a controlled forward
lean then the top hat should be positioned 30mm towards the rear of the cabinet from
the balance point (assuming a 35mm stand pole diameter).

Method 1:
In this method the cabinet is balanced on a wooden strip of 10x10mm cross-section
which runs in the side to side direction. Position markers should be drawn on both
sides of the cabinet to ensure the cabinet is always precisely aligned in the forward
direction. Carefully move the cabinet forwards and backwards to determine the front-
to-back balance point. If the cabinet is asymmetrical along its width then this process
should be repeated at 90 degrees to determine the left to right balance point.

CELESTION CKT-TF1225
 POSITIONMARKERSON
BOTHSIDESOFCABINET
CENTRE-LINEMARK

10 x10mmWOODSTRIP
FIRMLYFIXEDTOWOODEN
SIDEVIEW BASE. TOPVIEW

DETERMININGCABINETBALANCEPOINT- METHOD1

Method 2:
Safety note – this method requires two people, one to support the cabinet and the
other to mark the balance point.
The cabinet is carefully placed on top of an inverted top-hat attachment. Move the
cabinet relative to the top-hat until the optimum balance point is found. The position
of the top hat on the bottom of the cabinet can then be marked.

SAFETYNOTE: SECONDPERSONREQUIREDTO
SUPPORTCABINET.

TOPHATATTACHMENT

DETERMININGCABINETBALANCEPOINT- METHOD2

CELESTION CKT-TF1225