The woofer is one of the parts that make up monitoring speakers. It conveys the lower frequency sounds or bass information, and sometimes the midrange information, usually from about 40Hz to 2000Hz in a two monitoring speaker system. The woofer should be rigid enough to produce the intended sound, and at the same time should be able to stop moving as soon as the sound stops without adding any sound coloration caused by its material. Different types of woofer material exist, and there have been plenty of debates over which one provides the best performance. Each type of material has its own advantages and disadvantages, but there is currently no perfect woofer material for studio monitoring speakers.
“An ideal loudspeaker diaphragm would never flex, thus it would exhibit perfect pistonic motion,” says Gene DellaSala of Audioholics Magazine. “It would always be infinitely rigid, well damped, and inherently in that characteristic, the speed of sound through the material would be infinite, thus the mass would ideally be zero and the break up mode frequency would be infinity. Loudspeaker engineers have a word for this ideal cone material. Unobtainium (apologies to James Cameron from Avatar).”
As there is no perfect woofer material yet, manufacturers of studio speakers have been competing to create the material that provides the best performance. There are three main properties that designers look for in cones: stiffness, light weight, and lack of coloration due to the absence of ringing. So, which woofer material is the best according to these factors? Before answering this question, let us take a look at the materials that manufacturers of monitoring speakers commonly use to create woofers.
Paper — Paper cones perform quite well and can sound wonderful. It’s light and stiff, and can be engineered to meet practically any requirement. Although it does react to temperature changes and humidity, there are now treatments available to address this issue. The effectiveness depends on the type of treatment, but if properly done, it’s one of the best possible woofer materials. Most manufacturers of monitoring speakers make woofers out of paper.
Polypropylene — Polypropylene or plastic cones are easy to work with and perform quite well. Since they are reasonably rigid and extremely damped, plastic woofers have a controlled breakup, resulting in a smoother high end roll-off. Some may not sound as lively as their stiff cone counterparts, but well-damped plastic woofers can excel at midrange frequencies if engineered right.
Metal — Metal cones have the least coloration and distortion in the passband of practically all cone materials. Their downside are the un-damped resonances and severe breakup modes in the upper stopband. Aluminum has an exceptionally high stiffness to weight ratio although its damping characteristics are quite poor. Magnesium is kind of like aluminum, except it’s lighter and has less internal damping.
Kevlar — Kevlar is a fiber material often used to create body armor for police and military use. It can sometimes be very stiff, allowing the monitoring speakers to produce the intended sound and still stop moving once the sound is over. However, it should also be noted that since it’s very light and stiff, it can ring really bad depending on its design and fabrication. Studio speakers manufacturers Focal, Eton, Audax and Scan-speak often use this material as part of a sandwich structure.
Other types of woofer material include carbon fiber, ceramic, fiberglass, polyglass, polykevlar, hexacone, neoglass and several more.
To answer the question, there is actually no objective “best” woofer material for monitoring speakers. Manufacturers choose the material they think will provide their monitoring speakers with the closest to perfect sound reproduction. Moreover, the woofer material is not the only factor that goes into good sounding studio monitoring speakers. Other factors include the crossover, the cabinet, whether the speaker is ported or not, the listening environment, and personal preference. It is also highly desirable that monitoring speakers have a completely flat frequency response. If you don’t have enough knowledge to be able to properly take these factors into consideration, you might just want to check out this list of the best monitoring speakers on the market and pick one.
Once you get your monitoring speakers home, you should listen to them right away and especially listen to music you know well. You might also want to find a dealer that will let you audition these monitoring speakers in your home before you buy them, as placement is important and they can sound completely different at home. Choosing the right studio monitoring speaker that will suit your needs may seem daunting at first, but it’s definitely doable if you do your research and judge the sound with your own ears.