Critical listening rooms have become an essential tool for engineers in the Automotive Systems Division of Bose Corporation. Bud MacLellan, Bose Automotive Engineering Support Group Manager, provided insight into what these rooms are, how they are used and how they help take the performance of our automotive systems to a higher level.
What is a critical listening room?
Bud: People listen to music in all sorts of environments and with different playback systems. Unfortunately, some of those setups don’t reproduce the music faithfully to the artist’s recording. So, carefully creating an optimal environment provides us with the purest and most objective listening evaluation possible. A critical listening room is a tool that tells you what the music is supposed to sound like, and precisely where the instruments are placed on the soundstage, so you get an objective frame of reference. The room has specific characteristics for optimal sound; it has few reflections and no parallel surfaces to avoid slapback echo, where sound bounces back and forth causing anomalies in the listening position. The speakers are placed in front of you, and the idea is for the speakers to deliver the music directly to your ears. It is also an invaluable tool for new engineers to “tune” or calibrate their hearing, so they acquire an objective reference point when developing new sound systems in vehicles. We also use these rooms to help new employees learn, in a totally “clean” audio environment, how music is supposed to sound.
Bud MacLellen evaluating a surround sound recording.
What prompted the creation of the critical listening rooms?
Bud: In the past, Bose used Symphony Hall in Boston for its listening training for classical music, as classical music was originally our mainly listened-to music. This enables sound engineers to understand what an orchestra is supposed to sound like, and thus, become what we call a “golden ear.” However, it was difficult to go from Boston back to Framingham, as your acoustic memory isn’t that long. This was when I came up with the idea to build our own room, so we could go back and forth between our cars and the room very quickly. As of right now, we have critical listening rooms at our facilities in Massachusetts and Michigan in the U.S., and in Germany, Japan and Korea.
What is a “golden ear”?
Bud: Our golden ear listeners are experts, highly trained at evaluating sound and music playback. They can listen and measure the quality of the sound. As with so many things during the early years of our company, Dr. Bose was the first and led the way.
I like to say there are three levels of listening skills:
- You can tell if the sound is good or bad but can’t tell why.
- You can tell if the sound is good or bad and can identify the regions of the sound spectrum that are problematic.
- You can tell there is something not quite right with the system and can identify the specific frequency range that is problematic.
The third level is “golden ear territory” in that we can act upon it. This is extremely important and helpful for sound engineers as they can identify the exact problems—some of them very nuanced—so they can make the necessary adjustments.
Joey Cirone, a Bose sound engineer, focuses as he listens to a recording on the stereo configuration.
What is Bose’s tuning philosophy?
Bud: Our goal is to achieve natural, lifelike sound. There are several things we want to accomplish when we tune our systems, and they’re all important. We want to have a full and balanced spectral response. Instruments and vocals are reproduced faithfully and with exceptional clarity. We also want to deliver an accurate and immersive soundstage. This means that the music is presented on the stage in front of you with the natural immersion that occurs in a well-designed concert hall. The sound should also be balanced in each position, so you feel like you’re in the sweet spot no matter where you’re seated in the vehicle. That’s why listening in the critical listening room is so important. We get a clean, objective reference of what the artist intended the experience to be. A reliable and time-tested method I like is listening to an acoustic performance. Our car system and the response that it produces should sound as close to that as I can possibly get. That’s our goal—to re-create what the artist intended the music to sound like, as best we can.
The sound engineer then compares the same music recording in a vehicle.
What speakers are in the room and why?
Bud: The room is set up as two different listening rooms. At one end, we have a surround setup to evaluate discrete surround sound. Our team built five speakers in the lab to ensure the best possible quality. This side of the room is helpful when constructing a car with surroundsound as these speakers have five channels and a wider soundstage. The opposite end is a stereo setup. On the stereo side, the speakers that we use are Genelec. Some may wonder why we don’t use our own speakers. The first reason is that Genelec is a very well-known and respected studio monitor. In addition, it is not a competitor of ours, and Bose does not specialize in studio monitors. Lastly, Genelec makes world-class speakers and has a very similar engineering philosophy to Bose, which allows us to accurately measure sound. Both sides of the room provide value to us when measuring sound and bringing it into cars.
The Critical Listening Room features several acoustic treatments and design elements
to ensure an optimal listening environment.
Why is a room like this important for Bose to have?
Bud: Our critical listening rooms are our qualitative measuring tools for sound. Not only can our teams go back and forth between the car and the room to see if the sound matches, but our OEM customers can as well. We invite them in so they can listen for themselves. As we then have a common reference, it’s much easier to determine together if the sound system we’re working on in their vehicle is sounding the way we all want.