What is a midrange driver?

As we learned when we examined high-frequency tweeters, even in the early days of electrical sound reproduction, people discovered that a single full-range driver was not the best solution for every situation. As different parts of the musical frequency range have different needs, combining separate drivers dedicated to reproducing specific frequency ranges delivers an integrated and coherent musical performance.

The most common implementation is to combine a high-frequency tweeter and a larger mid/bass driver, creating the familiar two-way speaker. However, adding a midrange driver between the tweeter and the woofer can reap additional benefits.

So, what is a midrange driver and what does it actually do? 

What does a midrange driver do? 

As already mentioned, in very simple terms the function of a midrange driver is to fill the gap between the high frequencies delivered by the tweeter and the lower octaves produced by the bass driver. In technical terms, this can mean they cover a frequency range from the 200 Hz upper limit of a bass driver to the lowest frequencies of a tweeter, at around 2 kHz. Midrange drivers commonly cover a band from 200-300 Hz to 2 kHz or even as high as 5 kHz, depending on the implementation, and the treble and bass drivers with which they’re partnered. This allows those partnering drivers to be tuned so that the tweeter operates in a narrower “comfort zone”, and frees up the woofer to deliver just bass frequencies, rather than having to reach up to cover the midrange as well.

So why does the midrange matter? Well, in simple terms, it’s where most of the music happens. The midrange frequencies are the parts of the sound we’re most familiar with, like speaking or singing voices, as well as unamplified guitars, pianos and the like.

For example, the fundamental frequency of a typical male speaking voice is in the range of 90-155 Hz, while a typical female voice is 165-255 Hz – of course a singing voice extends the frequency range. We’re also very sensitive to the quality of voices: listen to speech radio and it’s easy to tell when something is “off” in the way voices are being reproduced, and to hear the difference between a studio announcer and a reporter calling in from an outside broadcast. 

While a piano can reach down to 28 Hz, most of the “right hand action” is in a band up to 4 kHz or so, while an acoustic guitar runs from about 80 Hz to around 1.3 kHz. A violin sits firmly in the midband with upper frequencies extending to 3 or even 4 kHz.

The limits of tweeter and bass drivers can be stretched downwards and upwards respectively, as they are in the common “tweeter plus mid/bass” two-way speaker design. But in this configuration, compromises are necessary. Many speaker designs handle this extremely well, but using a midrange driver allows the tweeter and woofer to be further optimised for their tasks. 

The use of midrange drivers in smaller bookshelf and stand-mount speakers is less common, mainly because of the lack of space on the front baffle holding the drive units. Many compact floorstanding speakers are also of a two-way design and can sound great, but where space and design/engineering budgets allow, the use of a midrange driver allows greater flexibility and resolution, creating an even more musical sound. 

Midrange vs. woofers and tweeters 

Tweeters and woofers are designed for their task – tweeters for very small, high speed movements, and woofers with a longer throw to shift more air and create the longer wavelengths of low frequencies. In the same way, midrange drivers need to be optimised for their task. They need much of the speed of a tweeter but must also deliver longer wavelengths, while maintaining precise dispersion – our ears are more sensitive to the directionality of the frequencies they deliver than the low frequencies from woofers.

Some speakers using multiple drivers use the same driver size and type for mid/bass and bass, altering the frequency filtering to suit them to their different tasks. In general, though, midrange duties are handled by drivers of smaller diameter than the bass unit(s), mounted below the tweeter assembly on the speaker’s baffle, and above the bass section. This also has the advantage of positioning the midrange driver closer to the ear-height of the listener – again, it’s all about directionality. 

Types and sizes of midrange drivers 

Some speakers simply use a smaller version of the cone-type drivers used for bass as a midrange driver, with various sizes being employed from as small as 3” (7.5 cm) all the way up to 6.5” (16.5 cm) or so. A larger driver will move more air and thus potentially go louder than smaller sizes. It will also offer better lower frequency extension, allowing the tuning of the bass drivers below it to be more dedicated to pure bass. However, a trade-off with a larger driver may be reduced upper frequency extension, requiring the tweeter to extend lower to hand over to the midrange unit.

As mentioned above, in multi-driver speakers it’s usual for the cone material of the midrange driver to be the same as or similar to that of the bass units, for better integration. Cone-type midrange drivers commonly use paper/wood fibre cones, usually damped in some way to stabilise their vibration, either by impregnating the material with a polymer or resin or applying a similar coating to the surface of the diaphragm. However, a range of other materials can also be used for these midrange cones.

An alternative found in some speakers, and especially favoured for some professional-use monitors, is a dome-type midrange driver, acting like a “big tweeter” to deliver the lower frequencies of the midrange. Again, a range of materials can be used, but popular among manufacturers using dome midrange drivers is the soft-dome design, featuring a cloth diaphragm stiffened with doping or surface coating to maintain its hemispherical shape. Dome midrange drivers are usually of 2” (5 cm) to 3” (7.5 cm) diameter, but some professional and high-end applications can push this up to 4” (10 cm) or even larger.

Unlike cone-type drivers, which have their magnet-and-coil motor driving the diaphragm from its centre, dome midrange units use a larger motor assembly that drive the dome from its circumference, in the same way that dome tweeters are driven.

To optimise the performance of a midrange driver, it’s usually mounted in its own sub-enclosure within the speaker cabinet, isolating it from the heavier vibrations of the bass driver(s). This also provides isolation for the tweeter operating above it, allowing all the drivers to perform their task without interference.

As mentioned above, a midrange driver is usually located below the tweeter assembly and above the speaker’s bass driver(s). Often, the midrange is placed close to the tweeter for better acoustic integration.

Pros and cons of dedicated midrange drivers – Do you need the extra driver? 

As we’ve seen, the use of a dedicated midrange driver can bring enhanced clarity to a speaker system, especially one using multiple drivers. Midrange drivers are also popular in applications such as studio monitoring, where especially close attention is paid to the reproduction quality of voices and instruments.

However, in many domestic situations, especially in smaller listening spaces, two-way speakers with a high-frequency tweeter and a combined mid/bass driver may well be more than adequate. They will also appeal on the grounds of smaller size and lower cost. And when the speakers are to be used with modest amplification, the resolution of a simpler two-way design may suffice. 

Conclusion 

As part of a well-designed multi-driver speaker, the benefits of a dedicated midrange driver are easy to hear: not only will it make voices and instruments clearer and more realistic, it will also allow the other drivers in the speaker to perform at their best. Whether you're evaluating studio monitors or high-fidelity home speakers, the presence of a true midrange driver often (but not always) marks the difference between good sound and truly immersive audio.

Discover DALI Speakers 

Explore DALI’s complete lineup of high-performance loudspeakers, including acclaimed floorstanding speakers, bookshelf speakers and custom-install speakers featuring low-loss midrange drivers that deliver outstanding clarity and realism. Whether you're building an immersive home cinema or refining a stereo setup, our advanced midrange drivers ensure vocals and instruments are rendered with ultimate precision and integrate seamlessly for a truly authentic musical reproduction. 

Visit your nearest DALI dealer and get ready to hear the outstanding, authentic sound of DALI speakers for yourself.