The RedCatt Engineering and Manufacturing teams have put a lot of effort into the development of high performance bonding techniques, specifically for use in High Frequency (HF) transducers/speakers and research in the area of HF dome design and manufacturing. The technical paper covers: Dome Forming, In-Process Dome Quality Control, Dome Treatment and Coating Process, Adhesives, UV Curing, SPL Improvement, Power Handling, and the Result Evaluation.

1. REDCATT | T: (+86) 769-83181898 | info@redcatt.net | www.redcatt.net |
1st building | Pukyo Industrial Park | FuMing Industrial City | Dalang Town | DongGuan | China
Professional Loudspeakers
Redcatt Engineering Technical Note on Dome Bonding
• Well controlled, precise dome forming
• Unique proprietary process for dome pre-bonding coating
• State of the art UV cured adhesives
• PLC Controlled, volumetric adhesives dispensing
• Precise and well controlled UV curing technology
• Strong quality control, backed up with precise metrology
equipment
even the smallest variation in the dome shape. We are fully
capable of measuring dome shapes with a 0.002mm level of
precision.
Dome Treatment and Coating Process
We were fully aware of the potential risks in bonding of low
surface energy substrates. Modern adhesives are capable of
bonding such substrates with a more or less good level of
success. During the course of developing HF drivers we have
tested many possible bonding options and processes and
discovered the importance of the bonding process in terms
of acoustic and power handling performance. The develop-
ment process resulted in Redcatt implementing a pre-bond-
ing coating process that ensures high bond strength, lowers
bond strength variations and ensures the voice coil to dome
bond joint has the highest achievable joint strength. As of
today, 100% of our domes and voice coils go through this
proprietary coating process.
Adhesives
Good quality adhesives are the basis of successful bond-
ing. Extensive research has gone into the adhesives we are
working with to ensure that they are the best available and
thoroughly tested for our application. Our glue dispensing
process is as precise as dispensing can get with volumetric
glue control and precise glue bead positioning taking care
of our batch to batch consistency.
UV Curing
UV based glues require a proper and well controlled curing
process to ensure high, consistent bond strength. Our UV
curing chambers are provide high output ultra violet light
which is precisely projected and controlled. All assembled
parts are cured under multi-directional UV lights and are
rotated in the chamber to prevent shadowing.
The REDCATT engineering and manufacturing
teams have put lot of effort into the development of high
performance bonding techniques specifically for use in
high frequency (HF) transducers in addition to the extensive
amount of research we have performed in the area of HF
dome design and manufacturing. We would like to present
a few details related to some core Redcatt assembly pro-
cesses.
It takes a significant amount of engineering to
design a high frequency device but making thousands of
consistent parts based on the original design is an order of
magnitude more challenging.
Dome Forming
A key component of the HF assembly is the compression
driver or tweeter dome. At REDCATT we consider this step
one and have designed a unique dome forming process
that incorporates PLC controlled forming techniques to
ensure all aspects of the structure are precisely monitored.
By using a programmable logic control (PLC) based system,
we can incorporate excessively detailed process parameters
including pre-heating and forming temperature controls
that are within 0.5°C at each stage of forming. We are also
able to monitor and record the pressure of the forming gas-
es, pressure of the press cylinder, level of vacuum and lastly
the cooling profile. The control and timing of the individual
forming steps are precisely established depending on the
dome type and material used then stored and recalled from
memory at the appropriate time.
In-Process Dome Quality Control
Domes are randomly sampled after the forming process
and taken for dimensional and physical parameter mea-
surements. We have fully implemented precise laser based
3D scanning metrology equipment, capable of detecting
PIC.1 Part of REDCATT UV Cure Chamber

2. REDCATT | T: (+86) 769-83181898 | info@redcatt.net | www.redcatt.net |
1st building | Pukyo Industrial Park | FuMing Industrial City | Dalang Town | DongGuan | China
Professional Loudspeakers
VOICE COIL to DOME BONDING
0 1 2 3 4 5 6 7 8 9
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
FORCE(kgf)
Elongation (mm)
REDCATT TREATED DOME
SAMPLES
COMPETITOR’S SAMPLES
REDCATT NON TREATED
DOME
Result Evaluation
We have thoroughly examined samples of non-treated
dome assemblies and compared them with ours treated.
To get a larger data pool, we have also compared the
bonding strength against assemblies available in the mar-
ket place (same voice coil diameter, same dome material).
The results were measured and recorded using our tensile
strength equipment (Pic.2.). The graphs show the max-
imum peel force between the voice coil and the dome.
There is a visible power handling improvement in our
treated domes. In terms of a percentage increase, we have
improved the bonding strength by 100%. Not only was
the bond strength improved, but the data shows higher
consistency across the tested specimens.
SPL improvement
Improved bond strength between the voice coil former
and the dome also has a positive effect on SPL behavior.
We have seen major improvements in the lower frequency
bandpass of drivers, as well as above 8.3kHz in the case
of tested compression driver. The picture (PIC.3) shows
the SPL differences recorded for our 140NCD compres-
sion driver. The driver was tested with the same magnetic
assembly and the only difference was the installment of a
treated dome assembly.
Level
SPL
Frequency (Hz)
110
90
80
30
20
10
50 100 200 500 1k 5k 10k 20k 25k
100
70
40
50
60
2k
Treated dome
Non Treated dome
Power Handling
Another area that benefits from our bonding process
is a significant increase in power handling. One of the
common compression driver failure modes in high per-
formance applications is the where the voice coil former
debonding from the dome. Specifically, the commonly
used “T” joint (straight former) is prone to these failures.
As the result, manufacturers are forced to lower the power
handling specifications or come up with an alternative
voice coil former joint shape (f.e. Sandwich). In either case
we see major improvements in joint strength resulting
in higher power handling capability. Long term reliabili-
ty testing indicate around a 30% higher power handling
capability for a given assembly.
Redcatt Ltd.
1st Bld., Pukyo Industrial Park
FuMing Industrial City
Dalang Town, Dongguan
China
tel: +86 769 8318 1898
Redcatt Co. USA Office
17802 134th Ave NE
Suite 17
Woodinville, WA 98072
USA
Tel: +1 206 883 6623
Email: info@redcatt.net
Web: www.redcatt.net
Contact Information
PIC.3 Bonding effect onto the SPL
PIC.2 Tensile test results and comparison