Raw Driver Features

• Woofer
• Midrange
• Tweeter
• HLD (horn loaded driver)

• Cast - To pour molten material into a mold and allow it to solidify.
• Stamped - Formed by high pressure.
• Steel - A strong alloy of iron containing up to 1.5 percent carbon along with small amounts of other elements such as manganese, chromium, and nickel.
• Aluminum - A light metallic element that is silvery white, ductile, malleable, and resistant to corrosion. The commonest metal found in the Earth's crust.
• Composite - Any building material made up of different ingredients.

• Foam - Material containing rubber, plastic, or other material filled with many small bubbles of air to make it soft or light.
• Cloth - Textile surround. Consisting of woven cloth fibers.
• Rubber - Naturally occurring elastic substance. A strong elastic material made by drying the sap from various tropical trees, especially the rubber tree. Also a strong elastic synthetic substance made either by improving the qualities of natural rubber or by an industrial process using petroleum and coal products.
• Butyl - Rubber, offering improved resistance to stretching and deterioration over time compared to foam.
• Santoprene - A manufactured rubber, offering improved resistance to stretching and deterioration over time compared to Butyl rubber.

• Single - Driver having only one voice coil.
• Dual - Driver having two separate voice coils.
• KaptonŽ - Is an advanced electrical insulation material used by engineers in the electronics industry, which maintains its mechanical stability at very high and very low temperatures, resists high mechanical stress during assembly operations, has excellent electrical insulation and thermal properties, has outstanding resistance to most chemicals, solvents, lubricants and fuels, allows space and weight savings.
• Aluminum - Made from aluminum metal.

• A pleated, round, springy, device that centers the bottom portion of a loudspeakers cone in the frame. The spider is where the diaphragm/cone meets the voice coil. Usually made from stiff, woven, fabric.

• Describes a filter, or series of filters, that pass a specific range of frequencies while blocking others. A crossover is a component that divides an audio signal into two or more parts by frequency.

• Sealed enclosure - Airtight enclosure that completely isolates the back wave of the driver from the front. Very tight, defined sound (with Qtc = 0.707) with very good transient response and power handling. Low frequency roll-off is at -12 dB/octave. Less efficient than other designs. Higher distortion levels at resonance. Easy to design and build.
• Ported Enclosure - a type of speaker enclosure that uses a duct or *port to improve efficiency at low frequencies. Excellent design for lower power systems, as the port often adds up to +3 dB to low frequency efficiency. F3 can be set considerably lower with proper design, although low frequency roll-off is generally -24 dB/octave. Good transient response with proper tuning, although the driver loses damping below the tuning frequency. More difficult to properly build and tune than a sealed enclosure, with several "optimum" alignments available depending upon the Qts of the driver. *Port: An opening in a bass-reflex speaker system that allows the sound wave from the back of a driver to reinforce the sound wave from the front
• Free air - Sometimes referred to as infinite baffle mounting. This is when the front of the driver is completely separated from the back by a baffle board, door panel, rear deck, etc. The front nor the rear of the driver are in any specifically tuned enclosure, just completely separated from each other. This eliminates cancellation.
• Single Reflex Bandpass Enclosure - sometimes called a 4th order bandpass. A design where the driver is completely "buried" in the enclosure, mounted in a sealed chamber (Vr) and firing into a second ported chamber with the sound emanating from one or more ports. This second chamber (Vf) is tuned to the sealed drivers Fcb. Band-pass enclosures pass only a limited range of frequencies, negating the need for crossovers in the circuit. In a typical single reflex bandpass, the cutoff rate below and above the "pass-band" is at a rate of -12dB/octave. These designs are very efficient within the operating bandwidth, with superior power handling, but generally inferior transient response to sealed (all the sound has to come out of the vent). Transient response can be very good if the enclosure is configured with an S of 0.70. Can be very difficult to design and build.

• Full range box - A speaker system that plays a wide variety of frequencies from low to highs.
• Subwoofer box - Speaker system that produces only low frequencies.
• Amplified subwoofer - Speaker system that includes an amplifier and produces only low frequencies.

• How many enclosures the drivers are mounted in.

• Hatchback -Enclosure can be mounted or placed in hatchback, trunk, van, or any other accommodating location. Long square or rectangular type enclosure.
• Truck box - Different than a hatchback enclosure this box fits behind the seat of a pickup truck or two seat car.
• Mini-boxes - Small, usually full range enclosures that are mounted to any flat surface. Often called surface mount speakers.
• Tube - Round or square enclosure with low frequency driver or drivers located on the end.
• Custom fit - Designed and built to be mounted in a specific vehicle in a specific location.
• Sealed - Airtight enclosure that completely isolates the back wave of the driver from the front
• Ported - Type of speaker enclosure that uses a duct or port to improve efficiency at low frequencies.
• Bandpass - A design where the driver is completely "buried" in the enclosure.
• Isobarik - Enclosure where one woofer is buried in the enclosure and a second is mounted up against the first and wired in reverse polarity. The name Isobarik comes from a term that means "constant pressure".

• Describes components manufactured for use specifically in boats. Precautions have bean taken to protect the electronics and drivers from elements such as water and heat.

• Spring clip
• Banana plug
• Binding post
• Barrier strip

• PEI - Polyetherimide. A plastic-based polymer used primarily for tweeters and midrange cones offering high resistance against harsh environmental extremes, superior rigidity, damping and resistance against harsh environmental conditions.
• Paper Paper is the traditional material for speaker cones and is widely (though mistakenly) considered to be an outdated technology inappropriate to high performance audio applications. Among its virtues are that it can easily be formed into a wide variety of shapes without overly complex or expensive tooling and its mechanical properties can be varied over a usefully wide range. Unfortunately, untreated paper is very sensitive to environmental conditions -- humidity in particular. As the ambient humidity changes, the moisture content in the paper also changes, and this leads to changes in cone mass and other parameters. Also, while it is possible to manufacture paper to be stiff enough to get extended frequency response, the paper itself is usually insufficiently lossy to achieve a smooth rolloff. Finally, paper is not the easiest material to manufacture consistently, with the possible result that there will be wide production variances. The first two of the above shortcomings can be greatly alleviated by the application of various types of surface treatments including latex and PVA-based coatings and impregnations. These coatings help to isolate the cone from ambient environmental conditions while increasing transmission loss, thereby smoothing out the upper range of the driver. (Note: many coated paper cones are coated largely for aesthetic purposes using God-only-knows what kind of materials that do God-only-knows what to the acoustical performance of the driver.) The potential for wide production variances can be ameliorated by tightly controlled production processes and quality material sourcing. Despite the seeming low-techness involved, a well engineered paper cone can deliver a combination of bandwidth and smoothness that is at least as good as any "higher-tech" material. Additional research into new paper formulations, manufacturing methods, and treatments continues. Don't be surprised if some of the newest "breakthroughs" in cone technology are based on lowly, old-fashioned paper.
• Polypropylene Polypropylene is probably the most common plastic material used in speaker cones. Most cones advertised as being made of polypropylene are in fact a combination of polypropylene and a mineral or other filler (e.g., carbon fiber and KevlarŽ). These fillers can be used both to control costs and to alter the mechanical properties of the material. Polypropylene cones tend to be inherently well damped with the result that they can deliver smooth, if not terribly extended, frequency responses. They are also largely immune to changes in ambient humidity. The material itself and the methods used in manufacturing cones with it are such that tight tolerances are easily achieved. In fact, polypropylene is the material of choice for may researchers involved in finite element analysis (FEA) of drive units because it is easy to reliably characterize. Polypropylene acquired something of a bad reputation in its early days due to fact that it's a difficult material to get things to bond to. Luckily, modern adhesive technology has completely solved this problem. However, this is not to say that polypropylene is free of problems. While a quantitative study has never been published (not to my knowledge at any rate), there are some who feel that drivers made with polypropylene cones tend to exhibit an audible degree of hysteresis or hysteresis-like behavior. (Hysteresis is a kind of nonlinearity where the parameters of a system which should be constant vary depending on the system's recent history.) The most common thinking is that it is the viscoelastic creep present in all plastic materials that is responsible. (Viscoelastic creep refers to the tendency of plastic materials to slowly stretch when under stress. This process may or may not be linear and typically is related to the lossiness in the material.) One colleague whom I respect greatly feels that the joint between the voice-coil former and the cone may be to blame. He suggests that the heat generated by the voice-coil and dissipated by the former may soften either the plastic cone material or the glue at the joint -- the amount of softening depending on how much power the coil is dissipating. Despite these actual or imagined problems, polypropylene cones remain a popular choice for high performance systems largely because of their well-behaved high-frequency response and consistent performance.
• Other plastics Apart from polypropylene, there are numerous other plastic and plastic-based materials that have appeared over the years including TPX, HD-A, and HD-I (all manufactured by Audax), Neoflex (manufactured by Focal), and Bextrene (which polypropylene largely replaced). All these represent attempts at finding combinations of stiffness, lossiness, density, and sound velocity that are somehow optimal for a given application. They generally have the same virtues and potential pitfalls as polypropylene.
• Resin-bonded high-strength woven fibers In this class of materials belong most carbon-fiber, fiberglass and KevlarŽ cones. These cones are made from a fabric of fibers bonded together with an epoxy or similar resin. The fibers themselves have a high degree of tensile strength; when embedded in an appropriate resin, a material of considerable stiffness results. Not surprisingly, these woven cones tend to have extended bandwidths. However, it comes with the cost of quite a bit of roughness as the internal losses of the basic resin-bonded material are quite low. It has been suggested the random orientation of the fibers helps to break up standing wave patterns on the cone, thereby smoothing the response of the driver. In our experience, this phenomenon has at best a minor influence on the high frequency response of the driver as every woven-cone driver we've examined has exhibited a rather rough high-frequency response. Attempts have been made to improve on the basic construction of simple woven fabric cones. One manufacturer of raw driver units employs two thin layers of KevlarŽ fabric bonded together with a resin and silica microball combination. The laminated structure is purported to be very stiff and the core material has the potential of introducing a controllable amount of damping. Another driver manufacturer employs a similar sandwich structure but with a honeycomb Nomex core. While these technologies are very exciting, they tend to be extremely costly and suffer, to greater or lesser extent, from the same high frequency roughness as their simpler cousins. It is highly unlikely that a woven fabric cone will have any hysteretic properties. (Although the surround and spider -- even the motor system -- may still suffer from hysteresis, but that's another issue.) So, while they may not generally be the best choice for wide-range applications, woven fabric cones are well suited to low-frequency applications owing to their inherent stiffness and immunity to hysteresis. In addition, woven fabric cones typically are insensitive to environmental conditions and are not likely to be bothered very much if exposed to a direct heat or light source (e.g., the sun). Thus they may be well suited to a variety of mobile or even outdoor applications as well.
• Metal Metal is seeing something of a surge in popularity as a cone material. Of all the materials we have discussed so far, it is the least well damped and so suffers from extreme peakiness in the high frequency region -- peaks of 12 dB at 5 kHz for a 6-1/2" driver being not uncommon. However, below their first breakup mode, metal cones tend to be very well behaved, and this is a major source of the attraction to metal cones. The most common materials used in metal cones are aluminum (and its alloys) and magnesium. Given the broad range of forming and surface treatment options possible with these materials, it is not inconceivable that we may one day see the advent of a well-controlled metal cone driver. However, even with the best crossover design, the high-frequency peaks present in currently available cones make them a poor choice for wide-range applications.
• Everything else Driver manufactures are constantly experimenting with new permutations of basic materials and constructions in an attempt to find (at best) a better compromise for a given application, or (at worst) a product that merely has greater market appeal. Laminates of all sorts, KevlarŽ and paper composites, and KevlarŽ and plastic composites are but a few of the materials that have recently been made available. As with any new technology, all claims made for or against such new materials must be considered very, very carefully.
• The Bottom Line I hope that by now it is clear that the "best" cone material to use for high performance audio depends on what you need to do with it and that at best it will only be some kind of compromise. It is also important to bear in mind that a loudspeaker driver is much, much more than the material from which its cone is made. The profile of the cone and distribution of material, the properties of the surround and spider at various frequencies, the voice coil geometry and materials, the magnetic structure, etc. all play a large role in the final performance of the driver. What all this means, dear reader, is that you simply cannot judge a driver by its cone material
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