"Grotbox" (sometimes written separately as "grot box") is slang used by sound engineers and music producers to describe a device that simulates the performance of cheap speaker systems. Today, these include consumer devices such as radios, budget car stereos, portable speakers, smart speakers, computer speakers, and the now-obsolete mini boomboxes, among others.
Many sound engineers in the United States, Europe, and worldwide use various types of "grotboxes" to test how a studio mix will sound on lower-quality consumer speakers, which typically have a limited frequency range and sometimes (even today) monophonic sound.
Some experts argue, with good reason, that the high-quality, accurate frequency reproduction of studio monitors can mislead a music producer or mixing engineer regarding the "translatability" of the mix onto consumer devices. Even budget studio monitors and monitoring headphones nowadays are too good—an inadequately balanced recording can sound quite convincing on them.
That's where the danger lies—try listening to slightly underworked music with deep bass and low-frequency kick-drums on smartphone speakers or cheap computer speakers, and you might be surprised to find that neither the bass nor the kick-drum is properly audible on these devices.
The same thing can happen with other instruments and elements of sound design. There are still plenty of consumer devices on the market with tiny speakers and narrow frequency ranges. There are even mono devices, such as inexpensive radios. Strangely enough, ordinary people still frequently listen to music on these devices. Thus, music producers and sound engineers who rely solely on the notion that "everyone listens to pop music through headphones" may end up in trouble.
Predictably, smartphones came in second place for music listening time, accounting for 27% (meaning people listened to their favorite songs through headphones). Laptops and desktop computers took third place with 19%. High-quality consumer Hi-Fi audio devices accounted for 8%, portable speakers for 4%, and "smart" speakers for 3%. Another 4% went to other mobile devices. The data were collected from a substantial sample of 34,000 respondents aged 16 to 64 living in all major regions of the world.
Even if we assume that all users of desktops and laptops listen to music through broadband headphones or relatively good quality and fairly large desktop computer speakers, we cannot be sure that all radio listeners have such endpoints. Radio still plays through a wide variety of amplifiers and speakers—from cheap car stereos to portable radios with a single mono speaker.
Roughly calculating, we face the fact that anywhere from a third to half of music lovers still listen to music on God-knows-what—usually, on "booming" and "whistling" gadgets that should never be allowed near music recordings. Yet, this represents a significant portion of the consumer music market, and it can't be ignored.This means that modern music producers are not necessarily required to check their mixes for "translatability" on consumer devices, but they should certainly not neglect doing so.
Consumer speakers typically have small drivers that are physically incapable of reproducing the full range of musical bass frequencies. Additionally, cheaper drivers struggle to reproduce ultra-high frequencies above 12,000–15,000 Hz. If you will, “good” bad drivers can decently cover a range from about 80 Hz to 15,000 Hz. On the other hand, “bad” bad drivers may have an even narrower actual range—somewhere between 200 Hz and 5,000–7,000 Hz.
Furthermore, cheap consumer drivers (as well as amplifiers sending signals to them) distort the amplitude-frequency response of the music mix. In simpler terms, what reaches the listener's ears is not necessarily what’s actually in the music, but rather what the "amplifier-speaker" system was capable of delivering. Consumer audio devices can exaggerate certain areas of mid and high frequencies while muting others. As one might guess, low frequencies fare particularly poorly.
And here's the cherry on top: some devices only have a single driver. This means they combine the stereo signal into mono. If the producers and sound engineers didn't take care of something called "mono compatibility," parts of the signals from the two former stereo channels could end up out of phase when combined. Consequently, these parts cancel each other out, leading to strange effects at certain points in the track. This can result in entire instrumental sections disappearing from the arrangement or unpleasant—and sometimes amusing—sound distortions. In short, it's far from ideal.
Back in the 1970s, many sound engineers began pondering how they could control the quality of their mixes, keeping in mind the issues with consumer devices mentioned earlier.
People in the music industry went to great lengths to simulate listening to their mixes on consumer devices. They would play the mix, leave the studio room, and listen to it from the hallway. They’d do this with the studio door closed. Some would record a rough mix onto a cassette tape and then listen to it through a car’s monaural or stereo system. Others had models of multitrack recorders equipped with tiny mono control speakers in their studios, which they used to listen to the mix.
Eventually, someone came up with the idea of having special small, poor-quality audio monitors in the studio that were capable of playing in mono. In the United States, the Auratone 5C Super Sound Cubes became the most popular choice (eventually earning the nickname "cubes"). These compact and practical models were produced by a family-owned company founded by Jack Wilson in his garage in Chula Vista, California.
As audio technology progressed and high-fidelity studio monitors became the standard, the 5C cubes took on a new role. Their limited frequency range and compact design proved invaluable for checking how mixes would translate on everyday listening systems. This unexpected application cemented their legendary status in studios worldwide.
Word quickly spread about the unique properties of the "cubes," and they gained popularity across different continents. In some regions, producers and engineers adopted Auratone cubes, while others crafted homemade versions inspired by the originals, often in small quantities.
This tradition did not replace the venerable practice of listening to rough mixes on car audio systems. Later, they listened to them on portable stereos from popular Japanese manufacturers (cassette boom boxes). Then, they turned to cheaper, lower-quality (and sounding) boom boxes.
Around the early '90s, inexpensive desktop computer speakers made of plastic became widely available globally. In some countries, they were referred to as "tweeters" and used in studios similarly to the famous "cubes."
Today, there is a wide variety of consumer electronics that can play music. Mixes are tested on built-in speakers of "smart" TVs, on entry-level portable speakers favored by teenagers, smartphone speakers, and so forth.
The essence of the process is to hear the created music on the worst and lowest-quality speakers that potential consumers might use. The goal is to identify which instruments and parts of the recording "disappear" during such playback. Typically, cheap audio speakers "kill" the bass, some drum kit parts (mainly kick drums), low-frequency synthetic sounds, and part of the sound design. Also lost is a sense of "air" in the ultra-high frequencies.
Once a sound engineer discovers that some useful musical information is lost on these simulated consumer speakers, their task is to adjust the mix accordingly. Ideally, the correction should ensure that elements like the bass line, kick drum, and other essential arrangement components fit within the limited capabilities of the consumer speaker.
On these poor-quality speakers, "light" versions of recordings should still convey the drama, aesthetics, and music itself that was written and performed.
Today, several manufacturers worldwide produce lines of decent "bad" audio monitors inspired by the legendary "cubes." Some music producers and sound engineers prefer to always have something similar in their control rooms. Others use specialized virtual audio plugins (which have also been developed) that mimic the sound of both the "cubes" and car audio systems, iPhones, and other popular studio and consumer devices.
Five out of ten experts will tell you: "Want a quick way to find out what's wrong with your mix? Play it on your regular monitors, step out of the room, slightly open the door, and gradually move away from it, listening carefully. The mix should remain 'audible' at a distance of 10-15 feet from the door. The thing is, this quick 'makeshift' solution mimics the high-pass and low-pass filters common in many consumer devices. Additionally, under these conditions, the important frequencies that our brain has evolved to tune into reach the human ear better. If you can hear all the crucial parts of the music in this range and at this distance, chances are your mix works well for most consumer devices."
There is also a fairly simple technical solution for quickly simulating a "grotbox." On your project's master bus, insert a parametric equalizer and drastically cut off frequencies below 200-230 Hz and above 2600 Hz. The filter slope can be quite steep—up to 30 dB per octave. Listen to your mix and note which important parts of the arrangement disappear, become inaudible, or get overly suppressed by other instruments.
This method crudely but effectively makes your studio monitors sound almost like the worst speakers imaginable. If you also apply a mono-compatibility checking plugin on the master bus (switching the track to mono by summing the left and right channels), your speakers will sound so terribly that it's hilarious!..
Some music producers say, "The soul of music lives in the midrange frequencies." This statement not only sounds impressive and poetic, but there's truth to it. The perceived "fullness," "warmth," and physicality of a mix indeed come from musical and noise elements located in the midrange.
Ironically, it's in this same range where frequencies responsible for muddiness (around 200-300 Hz), "boxy" sound (around 400 Hz), "wooden" sound (around 1000 Hz), and so on reside.
Essentially, if within the radically narrow frequency band from 200 to 2600 Hz, you hear music rather than indistinct sonic mush, your mix is successful. However, the topic of the "soul of music" in relation to the frequency range deserves a separate discussion…
