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As we manufacture our own components we have the ability to supply a diverse product range. We specialize in pro-audio loudspeakers sizes: 8", 10", 12", 15" and 18".
At Lorantz we understand the need to be more competitive, we must offer superior technology to our competitors, better production techniques, endorse quality control concepts and acquire overseas marketing skills, gear towards global market. These demands are necessary for long term prosperity and only achievable with a better working relationship between supplier and customer and between Tertiary education and industry.
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FE flux density magnitude displayed with colors.
We employ finite element CAD design to optimize the magnetic circuit. Although it is possible to design magnetic circuits without such tools valuable information is available from FE analysis. BL motor strength can be optimized and BL linearity can be improved. BL non-linearity is a major contributor to low frequency distortion.
FE analysis is a valuable tool enabling the designer to:
- Accurately predict gap flux
- Identify critical magnetic paths which require special attention
- Optimize magnet design for maximum efficiency
- Optimize the geometry for Bl linearity thereby minimizing associated distortion
- Minimize the weight without compromising performance
- Testing the design for component sensitivity
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Loudspeaker performance is very dependent upon the air-gap flux density which in turn is dependent on the physical size and quality of magnetic components. Consistent uniform high quality production is only possible with precision machined magnet components, the magnetic gap dimensions must be maintained to very strict tolerances. Demanding physical tolerances and production consistency were achieved by de-skilling manufacture with CNC machinery, implemented in 1995.
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CNC machined pole-pieces
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Much research has been carried out in an attempt to optimize cone materials, shape which directly affect sound quality and reliability. Most of our research has focused upon paper cones. Paper is made from cellulose, with tree-products being the prime source of cellulose. Paper cones satisfy the requirements of rigidity, strength, damping with low mass. We have developed expertise is the manufacture of traditional felted paper cones made from raw Kraft paper stock and processed to achieve the desired characteristics.
Paper cones are widely employed because they permit optimization i.e.
- Wide choice of base materials from softwoods to hardwoods and synthetic fibers can be added
- Choice wet end chemistry additives and treatments to improve strength, stiffness, moisture resistance and damping
- Choice of coatings and impregnants
- Weight and thickness is controllable to better than 5%
- Thickness can be varied over the cone body for optimum performance
- Density can be varied over the cone body
- Press, no press, hot press or cold press
Paper responds well to after treatments such as lacquer dipping, local strengthening, mold inhibitors, pesticides wet strength agents. Paper is also very recipient to surface treatment to improve strength, aging and water resistance and damping. In addition, paper offers excellent adhesion qualities and long life. These factors combined with excellent/pleasing sonic qualities make paper cones popular.
Paper cones are made from a variety of base ingredients the main components are softwoods however most are made from a blend of soft and hardwoods and it is not uncommon to have one or more of the following, kapok, wool, wheat, straw and rice straw flax, rayon, hemp, cotton glass-fiber carbon fiber and or Kevlar® added to the mix to optimize a given mechanical parameter. The real skill is to optimize the blend for a given application. The choice and quality of paper materials and processing influence the tonal quality, mechanical strength, hence longevity. Reliable consistent raw material quality and process control are important factors in loudspeaker production. The individual voicing requirements of monitor, bass, lead, rhythm guitar, synthesizer and quality sound reinforcement applications are achieved by altering the cone material properties and processes.
At low frequencies we want the cone to behave as a rigid piston, so we desire high rigidity
Bending deflection is proportional to
Where = Poisons ratio
E = Elastic modulus in bending
t = thickness
p = density
Therefore the material properties must be optimized for maximum rigidity if optimum piston operation is desired.
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The dissemination of design techniques analysis data and optimization of loudspeaker cones does not receive the same public attention or that other loudspeaker aspects do. Cone shape profile material selection is still an art/science not well understood except for the most proficient designers due to the complex analytical skills required. Little information is available on a number of crucial design factors:
- What effect does diaphragm shape have upon the frequency response, rigidity, material stress, directivity and distortion?
- What are the optimum cone material properties and what is the sensitivity of the various material and shape properties
- What is the optimum cone body thickness and should the thickness be constant or varying
- What are the important factors for longevity
- How do we design a diaphragm for low distortion?
How do you get a light weight flimsy coil of fine wire attached to a flimsy light weight cone to survive years of repeated, exceedingly high peak acceleration at high temperatures? Which adhesives should you use to hold an assembly together without creep over a wide temperature range operating at unknown high mechanical stress? The loudspeaker designer requires an understanding of materials science, chemical engineering, thermodynamics, mechanical engineering, electrical engineering and acoustics. Engineers who do understand good design are reluctant to share this knowledge.
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Much of the mystery surrounding cone design has been unraveled using computer modeling. The loudspeaker diaphragm vibrations and resulting sound pressure level can be modeled using finite element FE and/or BEM. These are essential tools to assist the design engineer in optimizing diaphragm shape and material properties; however accurate modeling is not simple. The major problem being that there is no one solution when one has to juggle many variables. Optimizing the surround shape for optimum mechanical linearity my not be the optimum shape for flat sound pressure response.
Typical direct radiator loudspeaker diaphragm
Accurate computer modeling is dependent on accurately defining complex material properties. Often material properties are biaxial, non-linear and/or frequency dependent and these properties are not available. Glue joints are difficult to model. To construct a linear computer model for the loudspeaker diaphragm we must accurately define:
- Shape
- Young’s modulus
- Thickness
- Poisson’s ratio
- Density
- Damping ratio
- Constraints, vertical, horizontal, rotational
The cone body, dustcap, surround, suspension material properties must be determined before analysis can be performed. Time and money permitting FE/BEM computer analysis can provide essential diaphragm behaviour:
- Eigen modes
- Sound pressure field
- Directivity
- Sound pressure frequency response
- Polar response
- Mechanical stress
- Material deformation
- Buckling
- Auralisation simulation of the design via DSP
We have performed many detailed investigations and discovered that it is only possible to optimise for one variable , sound pressure level, stress optimisation, mechanical linearity, structural resonances still exist and hence design is complex. The art is to control the structural resonances and if possible move them out of band each has its limitations.
The following table details the first 13 axis symmetrical Eigen modes for a typical 12” loudspeaker diaphragm
| Mode |
Hz |
Description |
| 1 |
42 |
Fundamental free-air |
| 2 |
382 |
Surround |
| 3 |
536 |
Spider |
| 4 |
821 |
Surround |
| 5 |
1168 |
Spider |
| 6 |
1625 |
Cone body |
| 7 |
1889 |
Spider |
| 8 |
2005 |
Cone and surround |
| 9 |
2136 |
Cone and surround |
| 10 |
2453 |
Cone and surround |
| 11 |
2517 |
Spider |
| 12 |
2672 |
Cone body |
| 13 |
2769 |
Spider |
It is impossible to eliminate Eigen modes for a given structure; however the diaphragm shape, material properties and material thickness can be optimized so that Eigen modes are controlled or moved. FE analysis displayed the following Eigen modes for a typical 12” diaphragm.
The above diagram displays the second Eigen mode at 382Hz, a surround resonance magnified approx 100 times
The above diagram displays the third Eigen mode at 536Hz, a spider resonance magnified approx 100 times
The above diagram displays diaphragm deformation the tenth Eigen mode at 2453Hz, cone body resonance and surrounds resonance magnified approx 100 times
The above diagram displays the cone stress at 1170Hz.
The above diagram displays the sound pressure for an excitation frequency of 1123Hz at various positions within a 1 metre radius.
The previous pictures generated from FE analysis clearly display the eigen modes, material stress levels and sound pressure in the medium for a given excitation and stress. From the above sound pressure diagram it is obvious the sound pressure at 1123Hz is becoming directional. Often the design has other limiting factors ie cost, uniformity, fatigue, stress, operating environment, stability, UV resistance and aging qualities.
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The paper is processed by beating (paper trade term). Beating modifies the paper properties. The beating process allows the optimization of parameters such as Young’s modulus, density, and tears strength bursting strength or folding endurance. Important parameters are Young’s modulus, density, damping and sonic velocity. The extent of beating is measured by the Canadian standard freeness (CSF) test.
Paper cones are usually made from a blend of ingredients. Because it is unlikely that one material alone would produce high rigidity, high tear, high modulus and optimum damping from a common process. Softwoods generally exhibit the highest rigidity for a given weight however they exhibit poor local strength;
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softwoods therefore require additives and or treatments if used in high power demanding applications.
Apart from optimizing the mechanical properties of a loudspeaker diaphragm we observed the existence of a subjective preferred listener sonic velocity range within the paper. We employ
OFP (Optimized Fiber Property) technology in our in-house paper cone production.
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A variety of paper-manufacturing processes are employed in loudspeaker industry, often the manufacturing process restricts the choice of usable raw materials, and hence not all paper cones are the same. Most automatic cone plants are geared for high throughput. In the wet state paper is weak and the transfer process to multiple drying heads can disturb the paper and impair quality. Our paper cones are individually air-dried on the felting screen to ensure the paper is not disturbed; our cones therefore exhibit high bulk, which greatly improves stiffness and bending strength. The production tooling, optimized fiber property (OFP), the process and associated machinery developed by Lorantz has been optimized to produce superior paper cones.
The down side of paper cones is the high tooling cost, a major contributing factor in loss of market share to other cheaper alternatives. When the market demand shifted to high-mass cones requiring new cone profiles, paper cone suppliers were slow to respond due to the high cost of tooling. FE computer analysis and CAD-CAM manufacturing techniques CNC machining opens a new world for optimizing new complex shapes. However the resistance to change has seen the acceptance of some good alternatives
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The spider usually consists of a loosely woven material impregnated with a thermosetting resin and then formed under heat and pressure to produce the corrugated supporting structure. The outer edge of the spider is fixed at the spider clamp diameter to the spider platform and the inner diameter is fixed to the voice coil. The spider acts as a spring in the axial direction and centers the voice-coil in the gap.
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The function of the spider is to provide linear or deliberate progressive stiffness in the axial direction but restrict any radial or rotational movement of the voice-coil i.e. voice coil travel is ideally restricted to one degree of movement. Ideally the spider should be resonant free and noise free; however in real life the spider exhibits structural resonances and is also a sound producer. The spider also acts as a barrier for foreign particles from entering the air-gap. The spider should be designed to provide most of the driver stiffness, especially towards the limits of travel. This will minimize stress on the cone, and audible noise emitted by the surround at its travel limit, which would occur without the spider limiting. Spiders are made from a variety of base materials the more popular being cotton, cotton-synthetic blend, linen, Kapton, Kevlar, Nomex and glass fiber. Choice of material thickness and degree of impregnation control stiffness. At Lorantz we have a selection of base materials and infinite control of impregnation to meet your requirements however selection and control of stiffness requires a fair amount of experience and expertise. Flat suspension is preferable as these usually exhibit a symmetrical stiffness in both directions and offer superior mechanical stability. Spider shape and material and impregnation are important design features as spiders can be attributed to the following speaker problems:
- Background noise believed to be due to air-flow through the material and/or breaks in fiber bonding
- Mechanical non linearity
- Mechanical noise due to buckling
- Poor material and/or resin choice may result in premature fatigue, lose of stiffness
- Resonance affected by climatic conditions
- The correct choice of materials and process are important factors if mechanical stability, linearity, distortion and longevity are required in demanding applications
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To allow the cone to vibrate back and forth freely it is provided with a flexible area at its outer perimeter named the cone surround. The cone surround acts as a spring in the axial direction and provides part of the restoring force necessary to center the voice-coil in the magnetic gap. The functionality of the cone-surround is to provide linear stiffness in the axial direction but prevent any radial or rotational movement of the diaphragm i.e. its purpose is to restrict movement to one degree. When dissimilar materials are joined there is a mechanical impedance mismatch. If the cone body vibrations are reflected at the cone edge undesirable standing waves result, thus the other important function of the surround is to provide mechanical damping to the cone body. The surround can be made from various materials it is usually corrugated to permit movement but it must be resonant free itself and noise free.
Material choice and shape requires experience, low resonance (high compliance) speakers usually employ foam, Santoprene or rubber surrounds. Poor choice of foam may result in a short life when exposed to ozone, sunlight, or fungus. Rubber surrounds are more stable offer excellent mechanical damping qualities , but their high cost and high moving mass restrict there use to low efficiency studio monitor and audiophile applications, rubber surrounds are not suitable for low mass high efficiency drivers applications, also if the surround is too compliant centering qualities may be inadequate. Treated cloth surrounds are generally employed in high efficiency drivers due to their low mass. Cloth surrounds usually employ accordion or "m" roll shape profiles. The “m” roll offers excellent midrange performance and the deep center groove adds strength to minimize bell mode resonances, however it is less suitable for large excursion drivers. The accordion surround is the best choice for bass drivers; however there exist good and bad cloth surrounds. Wide large area surrounds with too many rolls result in surround instability, with the surround itself resonating. The selection of surround shape the physical dimensions, material properties damping treatment require careful attention.
The cloth surrounds needs to be treated with a damping sealing compound to enhance damping and also improve memory and restoration rebound qualities and life expectancy. Were possible we manufacture our own cone surrounds thereby permitting performance optimization and also tight control of driver parameters. Rebound quality and restoration quality are important features and are closely related with creep resistance. Each individual application, end user, environment, excursion, distortion, longevity dictate the choice of material and shape.
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The heart of the loudspeaker is the voice-coil, which consists of a single or multi-layer winding usually of copper or aluminium wire or copper coated aluminium. The winding provides the path for electrical current which in the presence of a magnetic field by motor action provides the exciting force to the cone.
Typical voice coil temperature-rise vs. time measurement under constant excitation.
The coil is wound onto a thin rigid bobbin which provides the connection between the winding and the cone body. Various bobbin material are employed in loudspeakers the more popular being, Aluminium-foil, Kapton®, Nomex®, glass-fibre laminate, each have their advantages in a given application. The winding wire employed in the loudspeaker industry is diverse in gauges, material, and cross-sectional shape and wire insulation coatings. Low temperature thermoplastic coatings are often employed in low power loudspeakers. High power professional loudspeakers demand the highest temperature thermo set adhesives to be employed.
We have found the choice of materials, the brand of materials; manufacturing method and process control play a significant role in reliable loudspeaker operation and longevity. We employ materials and processes, which produce the most consistent reliable high temperature voice-coils. The choice of bobbin material is equally important, structural rigidity; mechanical stability and thermal conductivity are important consideration. Minimizing temperature rise is imperative if thermal compression is to be avoided. We perform life tests and also test our speakers in demanding hire and rehearsal studio applications, the real world, to prove they are superior to competitor brands.
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Measuring loudspeaker parameters
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We employ LMS (Loudspeaker Measurement System) for extracting the loudspeaker parameters; however we import the impedance data from Liberty sine sweep measurements as these measurements contain true phase data.
The loudspeaker is clamped by the magnet structure using a non-magnetic vice which is fixed to the ground.
We then use LMS and/or LEAP 5 to compute driver Thiele/Small parameters. Please be aware that speaker parameter variations can be attributed to differences in measurement technique. Measurement technique, choice of FFT or sine stimulus and test level may influence the measurement. There are many proposed standards but until we can agree on a common base consult with the manufacturer.
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The sound pressure response displayed in our data sheets is performed as follows. The loudspeaker is mounted in a large infinite baffle. The microphone is placed on axis at one meter. We then use Praxis FFT to measure the reflection free sound pressure response. This only enables us to measure the SPL down to 100Hz. The SPL below 100Hz is derived from near field measurements and spliced with the FFT response. These results are then also correlated with real outdoor measurements.
We use the following equipment to measure the SPL response depending on the application.
- Bruel and Kjaer recorder and B+K 4133 mic
- LMS system
- Praxis MLS measurement
- Repair Kits
We offer repair kits for all our manufactured products. However we prefer to re-cone old models into existing frames. Our manufacturing process entails building the diaphragm within the loudspeaker mechanical structure. Our manufacturing process entails aligning the voice-coil with the magnet structure; this process ensures the best and consistent voice-coil alignment.
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This implies that obsolete models are repaired within their original shell therefore an original frame/magnet structure is required to produce the repair kit.

Typical Lorantz repair kits are supplied coil spider and surround assembled. Centering shim padrings and dust cap are supplied but glue is not supplied as it has a limited shelf life and hazardous to ship.
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If the order size permits we have the flexibility to custom design products. The following options exist:
- Nominal impedance is optional
- Linear voice coil travel is optional
- Free-air resonance is optional
- Speaker parameters can be varied ie Mms, Qe etc
- Dustcap type is optional
- Tropic –proofing
- Cone body material is optional
- Surround material and type is optional
Please bear in mind the standard model usually offers exception performance/price ratio.
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We offer various system designs employing our drivers to enable the amateur constructor to build professional loudspeaker enclosures. It should be noted that these designs are general purpose designs and therefore a preferred starting point. The ultimate design usually entails optimization for the given application be it cosmetic or functionality. Each application may differ in low frequency cut-off, power handling requirements, directivity, crossover frequencies and filter order. For instance a studio monitor design will be quite different to a PA hire application even though the working frequency range and power requirements may be similar. Each application has its unique requirements and cannot be covered by a single design. We currently use CALSOD and LEAP5 to optimize our designs. We have performed more than a thousand designs for customer’s third parties and our own use and many have world recognition.
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Lorantz is dedicated to providing a vital industry service in the pursuit of superior acoustic performance. However the work is specialized, we endeavor to offer the best possible service and superior quality audio products. Whilst every reasonable precaution has been taken in preparing our technical literature, the authors assume no responsibility for any errors or omissions, nor is any liability assumed for damages resulting from the use of the information contained in our publications, any patent liability or infringements should be checked prior to use of any information offered.
Michail Barabasz - Manager/Director
