Drivers In-system Design Others

Posted on

Each time your printer, scanner, camera or other external device is plugged in, it needs an avenue through which it can communicate with the computer. These avenues are known as device drivers, and they are small-scale software programs that serve as translators between the external hardware and the PC itself. 1080p60 from Atomos or Blackmagic Design HDMI to SDI converters currently not supported. 1080p60 from Blackmagic Design cameras currently not supported. Audio at the last few frames of an Apple ProRes 422(HQ) file occasionally records static. QNF drivers provide users the flexibility to try new features made available outside the launch cycle of longer-lived Optimal Driver for Enterprise (ODE) branches. QNF drivers are tested for workstation environments and are recommended only for those users who need specific features mentioned in the release highlights or release notes. Other classes of device drivers have been added to the kernel in recent times, including FireWire drivers and I2O drivers. In the same way that they handled USB and SCSI drivers, kernel developers collected class-wide features and exported them to driver implementers to avoid duplicating work and bugs, thus simplifying and strengthening the. The files there will allow the uninstall of software and drivers you've installed. I can't find a good answer for the differences between the other two folders, other that to say that since Windows 7, DriverStore is the default location for hardware drivers. However, the Drivers folder also contains drivers, perhaps for legacy compatibility.

Originally Published: May 29th, 2012

Inthis continuing series on defining Legitimately High Fidelity Loudspeakers, wehave discussed the following topics:

Thisarticle is dedicated to the actual loudspeaker drivers themselves (ie. woofers,tweeters, midranges, etc). Let us firstdefine what a loudspeaker driver is and what its primary role is. A loudspeaker driver is an electromechanicaldevice that converts electrical waves (music is more than impulses) intomechanical vibrations which in turn produces audible soundwaves. The size of the diaphragm will determine thebandwidth in which the loudspeaker will be most efficient at reproducingsound. A bass driver (usually 8” orlarger) is designed to reproduce low frequencies (20-500Hz), a midrange driver(usually 3” to 7”) is designed to reproduce frequencies above 100Hz to 4kHz anda tweeter (typically 1” or smaller) is designed to be most efficient atreproducing high frequencies (ie. 1kHz to 20kHz).

Do Exotic Driver Materials Make Speakers Sound Better YouTube Videos Discussion?

The Basics in Loudspeaker Driver Mechanics

It’simportant to understand how a basic loudspeaker works so we’ve included a basicdiagram of a typical woofer with all the major components labeled.

LoudspeakerDiagram – Courtesy of Polk Audio

The loudspeaker isbroken into several parts:

  • TheDiaphragm (aka cone or dome) - the actual physical surface area of the driverthat moves up and down from the voice coil interaction with the permanentmagnet, thus producing sound by compressing and rarefying air, thus creatingsound waves. (sound is not “moving air”it is propagating pressure fluctuations.)
  • TheDustcap (optional) – located at the center of the cone and covers the voicecoil and can increase rigidity of the diaphragm and most importantly in sealsthe diaphragm.
  • TheBasket (aka. Frame)– the physical structure that holds the entire drivertogether
  • TheVoice Coil – basically a wire coiled around a bobbin (electromagnet) atthe center of the speaker and attached to the spider. When current flows through the coil supplied by the amplifier. it produces a temporarymagnetic field when a signal is applied to interact with the permanent magnet(++ oppose ; +- attract). Whereextra bobbin strength is needed, a collar can be added to that portion of thebobbin not covered by the coil.
  • TheSpider (aka. Damper) – Two prime functions of the spider, in conjunction withthe surround, are to center the diaphragm, and force the forward and back movements of the voice coil tobe linear, so that the coil does not scrape the narrow magnetic gap. The Spider provides the primary restorative force in the suspension beingideally placed close to the motive force, the voice coil. Linearity of a drivers suspension (and hence compliance) iscritical and a lot of research has gone into designing spiders with thenecessary stiffness and linearity, and designed not to add structuralresonances of their own. The compliance of thespider & surround helps determine the low frequency limit of the driversuseful bandwidth, specified by the well-known free-air resonance (fs) parameter
  • TheSuspension (aka. Surround) – typically made of cloth, butyl rubber or foam,attaches the diaphragm to the driver basket and in conjunction with the Spider,helps to control and dampen cone movement. In some cases there may be more than one spider and in some cases(tweeters) there is no spider. Inwoofers, the surround is necessary to simply hold the edge of the cone in placeand, along with the spider, to ensure linear in and out movement of the voicecoil. It also functions as a mechanical termination for the radial travelingwaves in the cone (cones do flex!) where it can dampen standing waves that willoccur. The stiffness of the cone material is a factor in determining thefrequencies at which resonances occur - higher being better, but at leastoutside the intended operating frequency range.
  • ThePermanent Magnet – a fixed DC magnet which is part of the motor structureaffixed to the basket of the driver creating a stable magnetic flux across theannular gap which the voice coil sits in.
  • The Phase Plug (optional) – similar to the cone buttypically looks like a bullet. Itspurpose is three-fold, to reduce moving mass and on-axis beaming and also serve as a heatsink and to a smaller extent offering venting.
  • The Vented Pole Piece (optional) - this is a hole located in the center at the back of thepermanent magnet to help reduce air pressure under the dust cap and cool the voice coil.

To generalize a bit more, the magnet assembly of a loudspeaker consisting of a top plate, bottom plate and pole piece, voice coil and magnet can be considered the 'motor structure'.

ThisPolk example appears to be quite a heavy duty driver as evident by how muchventing and free air-flow they are incorporating into the design. This is the type of bass or midrange driveryou typically see in more expensive speaker systems that are able to sustainhigh output levels with low distortion and low compression. More budget-oriented designs typically won’thave vented pole pieces, which will limit how much thermal energy they are ableto dissipate at high output levels, thus potentially causing morecompression.

Check out our recently added YouTube Video discussion on Loudspeaker Driver Science with Shane Rich, Technical Director of RBH Sound to supplement this article.

YouTube Video Discussion: Loudspeaker Science: Identifying Good Speaker Design

Castvs Steel Stamped Driver Baskets

Loudspeaker driver baskets are typically constructedeither of stamped steel, plastic or cast aluminum. Plastic baskets are generally used solely for cost savings over cast, orheavy gauge stamped frames. They are fine for smaller driver applications (6” or less) but are usually notused for larger and heavier bass drivers where greater durability and rigidityis needed. Though there areexceptions. A well designed moldedplastic basket with glass fiber can provide better acoustics than both stampedand cast aluminum. The plastic can be designed by geometry and with fiber fillto have adequate rigidity, and it offers the benefit of damping any residualparasitic vibrations. Since stamped andcast baskets are more commonplace in the industry, we will focus most of thecomparisons on these two type of frame options.

Drivers In-system Design Others Perceive

the only reason to use stamped baskets is for cost savings

Here are the facts about cast aluminum vs. stamped steel frame speakers. Aluminum is paramagnetic. That means it is not entirely NON magnetic,as its permeability (let’s call it ‘desire to carry magnetic lines of force’)is about 5% higher than air. Steel onthe other hand, is hundreds of times more willing than air to carry magneticlines of force, the same way copper carries electrical currents, withease. The result is that the veryattachment of the steel to the top plate (part of the magnetic circuit intowhich the voice coil is immersed) guarantees the amount of magnetic force inthe gap will be reduced by the parasitic flow of magnetic lines of force intothe steel frame. However, much of thiscan be alleviated by moving the basket away from the frontplate by using aplastic, paper or other non-magnetic spacer. Good driver designers know and do this when dealing with stamped frames. In reality, flux leakage though the baskettypically isn’t a huge deal unless you are designing pro drivers that needevery bit of efficiency possible. But weincluded this point in this article to be as thorough as possible whencomparing various basket types.

Drivers In-system Design Others Job

Still,I can imagine some of you asking, why not use stainless steel instead ofregular steel? Good question. Two reasons: 1. It is much harder to form itby pressing (stamping) and 2. It is much more expensive than soft steel.

Drivers In-system Design Others

Stampedwoofer basket (left pic); Cast basket woofer (right pic)

Asignificant advantage of aluminum over steel is the way in which it effectivelydraws off heat from those parts of the driver that surrounds the voicecoil that get heated most quickly, such as the top plate. (remember, the top plate is directly attachedto the speaker frame, so this physical coupling will result in the transmissionof heat between the parts.) Since mostcast aluminum frames are several times thicker than the steel ones, and sincealuminum is an ideal material for heat sinking (it is what most heat sinks aremade of), it will also let the speaker run cooler for a given amount of current feed into thevoice coil. In addition, it will allow a larger amount of current to be put into the voicecoil by drawing away and dissipating the heat more efficiently than steel cando. The ONLY reason to use steel instead of aluminum for a speaker frame (andit’s a legitimate reason) is cost. Withthe proper tool, a single punch can stake and swage (attach) a steel frame to asteel top plate in a second or less. Nodrilling costly threaded through holes for screws in the top plate isnecessary. There is no need to buy the screws, or make sure they are glued inplace or screwed down with the right amount of torque. Stamped steel is a far less expensive routefor a big mechanized factory than cast frames are.

Castaluminum frames, if properly designed, are always going to offer an advantageover steel frames, especially with respect to rigidity. That being said, you can still have welldesigned stamped steel frames. Thebasket material alone does not define the quality of the driver. Manufacturers building legitimatelywell-engineered stamped frames typically use thicker gauge steel than the onepictured above left. This increasesrigidity and reduces susceptibility to ringing. You will find many of the high output budget subwoofers offered in the$1k or less price range employ thick stamped steel baskets. When trying to hit a target price point,while still offering respectable output and performance, this is a designcompromise that often makes sense.

Editorial Note about Cast Aluminum vs Steel Frames by David Waratuke

The issue of stiffness in a driver basket frame is not one of steel versus aluminum per se, it is one of geometry and manufacturing. Steel as a material is actually three times stiffer than aluminum as indicated by a property call the Modulus of Elasticity, which for steel is around 29,000,000 pounds per square inch (psi) while aluminum is only about 10,000,000 psi; a modular ratio of 2.9. The lower stiffness in a steel basket comes from using stamped manufacturing that limits thickness of resulting basket as compared to what can be cast. This difference in thickness creates an exponential differences in the geometric component of the stiffness for the resulting baskets. It all comes down to the fact that a cast aluminum basket typically contains more aluminum, with the correspondingly increased thickness, than there is steel present in a typical stamped basket and that more than makes up for the aluminum being a softer material.

AdditionalInformation about Cast Frames

Cast aluminum frames are made by pouringmolten aluminum into a block of steel that has been hollowed out using a veryprecise computer-cutting (CNC) program. This process is known as tooling, and it is a central process inall consumer products made today. Whenever you see a nicely molded, shapedpiece of plastic or metal, chances are it has been formed by some sort oftooling process. Tooling is very expensive, so much so that smallermanufacturers jokingly refer to the need to “tool” something as a four-letterword.

There are two basic types of tooling:Proprietary tooling and open tooling. Often proprietary tooling is copied, or the logo is simply ground off.

Proprietary tooling is tooling that thatparticular manufacturer designs and pays for themselves, and then they own thetooling and retain the rights to it forever. There are many distinctive tweeterfaceplates, woofer frames, or plastic satellite cubes which we associate with aparticular manufacturer’s look and style, and that’s because they’ve done theirown tooling. The manufacturer will often protect their tooling appearance witha design patent, in order to make their design immune to counterfeiting andunauthorized copying.

Good examples of proprietary, patentedtooling are Boston Acoustics’ automotive Pro Series cast aluminum wooferbaskets and Bose’s famous satellite cubes.

BostonAcoustics Pro Series Woofer (left pic) ; Bose mid woofer (right pic)

The other kind of tooling is what’s known as“open tooling.” Open tooling is tooling that a vendor of raw parts undertakesthemselves in anticipation that many of its customers will order their parts,thus making their (the vendor’s) speculative investment in the toolingworthwhile in the long run. Examples of open tooling are the cast wooferbaskets that many driver vendors make for their line of general distributionwoofers, for example, or the round plastic frames for ceiling speakers offeredby many Far East vendors to “brand name” speaker companies. You can lookclosely at the metal woofer baskets or round plastic ceiling mounting framesfrom many speaker companies and find that they are identical, absolutelyidentical.

There is nothing wrong with that, of course.The frame, top plate, back plate, and magnet are known as the speaker’s “hardparts.” It’s expensive for small speaker companies to tool and manufacturethose, so they buy them pretty much “off the shelf.” The “soft parts” of aspeaker—the cone, surround, voice coil, spider—are easier to customize andchange from run to run, so that’s where a lot of differentiation comes in forthe speaker companies. Brand A and Brand B may use the same basket, top plateand back plate, all tooled by Vendor C, but they specify and customizedifferent soft parts, and the resulting woofers are completely different, eachaccording to that particular company’s engineering design goals and marketingobjectives. Again even unique customtooled motor designs do not remain proprietary. They are copied. That'sprogress.

Cast baskets are more rigid than stamped alternatives

Rigidityof Cast vs Stamped Baskets

Regarding resistance to shipping damage, thisis a real concern. In the early 1990’s when magnetic shielding was importantfor speakers in a home theater so as not to interfere with CRT televisions,many speaker manufacturers added “bucking magnets” onto their speakers’ existingmagnet structures. This was another magnet, reversed, so its external magneticfield would cancel out, and then the entire structure was typically enclosed ina shielding “can” to further reduce stray leakage.

The problem was that now these speakers’frames were being asked to carry significant added weight for which theyweren’t designed. One major company was using a plastic frame and the additional weight of the bucking magnet andshielding were causing these frames to crack and break off during shipping.Another company was using stamped steel frames on their midranges, but thestruts were not reinforced with crimped sections—they were flat and thus veryprone to bending because of the added weight. The entire first shipment ofthese new speakers went out to the dealers and the mids were all inoperative,because the weight of the magnetically-shielded structures had torqued theframes so badly in shipping that the voice coils were all frozen out ofalignment. Both of these companies redesigned their baskets with additionalreinforcing ribs and added internal cabinet supports around the drivers to keepthem from moving and being damaged in shipping. So there is no question thatthe added rigidity and precise alignment afforded by cast frames is theirbiggest advantage. Cast baskets tend to hold the parts inalignment more accurately and with greater longevity. It has been proven countless times that suchbaskets survive shipping drops better than stamped baskets.

Bottom Line on DriverBaskets

Drivers In-system Design Others Jobs

Stampedbaskets are less costly to produce than cast baskets and are at a disadvantagein some aspects (strength, cooling, etc), but respectably good performance canstill be achieved with stamped frames. You will typically find the very best loudspeaker designs on the marketwill take advantage of the properties of cast baskets and thus employ them inALL of their drivers. Plus—cast-basketdrivers look so darned cool when they’re photographed by themselves! Anyspeaker marketing department worth its salt knows that!