Another aspect of room acoustics for home listening is RT 60 sound decay time. This should be used to determine how much passive treatment to use. Ideally in combination with room eq system like Dirac or Genelec GLM. Usually best to use passive treatments as much as possible to minimize the amount of active RQ needed, also attacking a link to using subs in small rooms to minimize bass problems, getting rid of room modes as opposed to creating more bass:
You're asking about a very important aspect of room acoustics: RT60 reverberation time. It's a key metric for understanding how sound behaves in a space.
Here's a breakdown of ideal RT60 times for home listening and recording studios, along with informative articles:
Understanding RT60
RT60 is the time it takes for a sound to decay by 60 decibels (dB) after the sound source has stopped.
- Too long RT60:The room sounds "live," "reverberant," or "echoic." Speech can be unintelligible, and music can sound muddy or smeared.
- Too short RT60:The room sounds "dead," "dry," or "unnatural." It can feel uncomfortable and lacks natural spaciousness.
It's crucial to remember that RT60 is frequency-dependent. You want a relatively even RT60 across the frequency spectrum for optimal sound. Often, low frequencies tend to have longer RT60s, which needs to be addressed with bass trapping.
Ideal RT60 for Home Listening Rooms
For home listening rooms (hi-fi, home theater):
- General Range: Most sources suggest a range of 0.3 to 0.6 seconds.
- Smaller rooms (e.g., less than 50 cubic meters/1,800 cubic feet): Aim for closer to 0.3 seconds.
- Larger rooms (up to 200 cubic meters/7,000 cubic feet): A range of 0.4 to 0.6 secondsis often recommended.
- Home Theaters: Some recommendations for home theaters lean towards the lower end, around 0.2 to 0.4 seconds, for clear dialogue and precise sound effects.
- Preference: Ultimately, personal preference plays a role. Some people prefer a slightly "livelier" room, while others prefer a "drier" sound.
Articles for Home Listening Rooms:
- RT60 Graph - REW (Room EQ Wizard):This article, while part of a software manual, provides excellent technical detail on RT60 measurement and recommended values for domestic rooms, including volume considerations.
- Reverberation Time - NTi Audio:This resource offers a table of recommended reverberation times for various locations, including recording studios and classrooms (which can give you a good reference for smaller, more controlled listening spaces).
- How do great sounding domestic listening rooms measure? | Audio Science Review (ASR) Forum: This forum discussion provides diverse perspectives and real-world experiences with RT60 in domestic listening environments, often highlighting that RT60 might not be the only or even mostcritical factor in small rooms.
Ideal RT60 for Recording Studios (Control Rooms and Live Rooms)
For recording studios, the ideal RT60 varies significantly between the
control room (where you mix and monitor) and the
live room (where you record instruments/vocals).
Control Rooms:
- Goal: Control rooms aim for a very precise and neutral sound. This means minimizing early reflections and achieving a relatively short, even RT60 across frequencies.
- General Range: Typically, 0.2 to 0.5 seconds is recommended.
- Smaller Control Rooms (e.g., <30 m²): Aim for the lower end, 0.2-0.3 seconds.
- Larger Project Studios: 0.3-0.5 seconds.
- Uniformity: It's crucial that the RT60 is as consistent as possible across all frequencies, especially in the midrange and high frequencies, to ensure accurate mixing and mastering decisions. A slight rise in the bass frequencies (e.g., up to 0.4 seconds at low frequencies when mid-range is 0.25 seconds) might be acceptable or even desirable in some cases.
Live Rooms:
- Goal: Live rooms often aim for a more natural, pleasant acoustic environment suitable for recording various instruments and vocals. The RT60 can be slightly longer than a control room to provide natural ambience.
- General Range: 0.3 to 0.6 seconds is a common target, depending on the desired sound.
- Acoustic music/Classical:May benefit from slightly longer RT60s (e.g., 0.6-0.8 seconds) to add "life" and "body" to the sound.
- Pop/Rock: Often prefer shorter RT60s for a tighter, more controlled sound.
- Flexibility:Many live rooms are designed with adjustable acoustics (movable panels, curtains, etc.) to allow for varying RT60s depending on the recording needs.
Articles for Recording Studios:
- Reverberation Time (RT60) in a Mixing Room - Record Mix & Master:This article provides an excellent overview of RT60 in mixing rooms, including calculations using the Sabine formula and practical tips for treatment.
- REVERBERATION - t.akustik:This article briefly discusses RT60 for control rooms (0.15-0.3 seconds ideal) and recording rooms (rarely exceeding 0.5 seconds), emphasizing the importance of early reflections and room modes over just RT60 in small spaces.
- Practical Acoustic Treatment, Part 3 - Sound On Sound:This detailed article covers various aspects of acoustic treatment, including RT60, its measurement, and provides useful absorption coefficients for different materials. It also discusses ideal RT60 for control rooms and studio areas.
- Are there any standards or guidance that can be referred to regarding target reverberation times within recording studio live rooms? : r/Acoustics - Reddit:A Reddit discussion where audio professionals share insights and experiences on setting RT60 targets for live rooms.
Important Considerations:
- Small Room Limitations: In very small rooms (typical home studios), the concept of a "diffuse sound field" (which RT60 is based on) doesn't fully apply at low frequencies due to modal resonances. Therefore, other measurements like Early Decay Time (EDT), C50, and C80 (clarity indices) can be more indicative of perceived sound quality in small rooms.
- Frequency Uniformity: Regardless of the target value, striving for a relatively flat RT60 across the frequency spectrum is crucial for accurate sound reproduction and mixing. Bass frequencies often require the most attention with dedicated bass traps.
- Measurement:To accurately determine your room's RT60, you'll need acoustic measurement software (like Room EQ Wizard - REW) and a measurement microphone.
By understanding these principles and using these resources, you can make informed decisions about acoustically treating your home listening or recording studio space.
PDF on the use of multiple subs:
http://www.gedlee.com/Papers/multiple subs.pdf
More papers from Dr Geddes:
http://www.gedlee.com/Papers/papers.aspx
No snake oil from Dr Geddes.