Outdoor Speaker Depot Blog
by OSD Audio • November 19, 2020
Home Cinema Speakers
In-Wall, On-Wall, On-Stands, Freestanding, In-Ceiling - What the heck?!
Things You Need to Do and Know
- Prioritizing Size and Looks (this is important because it starts to define your choices)
- Decide what Level of Surround Sound you want (this is important because it defines your layout and further refines your choices)
- Immersive - Up to 34 Channels
- Standard - 5 or 7.1
Immersive (Dolby Atmos) Home Cinemas
This is what Dolby says when it comes to mixing Atmos soundtracks:
Ideally, all monitors (with the exception of the subwoofer) should be of the same make and model to avoid any timbral shift due to unmatched frequency responses. If this is not possible due to budget or logistics, some monitor manufacturers produce models that are designed to match as close as possible the main models but in a form factor that is easier for ceiling mounting, either flush or on the surface.
Bass management, room correction, and time/frequency correction are essential for mixing and monitoring Dolby Atmos content.
What else does Dolby say?:
- Bass Management
- Bass management is essential for redirecting the lower frequencies to the speakers that can handle them (in most cases, a dedicated subwoofer). One of the features of Dobly Atmos is that all of the surround speaker channels are full bandwidth, including the height channels. This allows for accurate movement of a sound through three-dimensional space without any timbre shift.
- Correction and Calibration
- Compensation for room acoustics, delays for speaker position differences, and correction for individual speaker frequency response are all tools that can and should be applied if needed in order to maximize relative uniformity between all channels. Listening level calibration should be performed in order to align the individual monitor volumes and establish a listening environment conducive to creating a mix with a good dynamic range. Volume, phase, frequency, and time alignment of audio is always important in a control room whenever you have more than one speaker, and to an even greater degree in a Dolby Atmos environment.
Human Hearing, Bass, and Infrasonics
The generally accepted standard hearing range for humans is 20 to 20,000 Hz.
These represent sound waves with wavelengths of 17 meters (56 ft) to 1.7 centimeters (0.67 in).
- 16 to 32 Hz - 1st Octave - The lower human threshold of hearing, and the lowest pedal notes of a 32 ft pipe organ is 16Hz
- 32 to 512 Hz - 2nd to 5th Octaves - Rhythm frequencies, where the lower and upper bass notes lie.
- 512 to 2,048 Hz - 6th to 7th Octaves - Defines human speech intelligibility, gives a horn-like or tinny quality to sound.
- 2,048 to 8,192 Hz - 8th to 9th Octaves - Gives presence to speech, where labial and fricative sounds lie.
- 8,192 to 16,384 Hz - 10th Octave - Brilliance, the sounds of bells, and the ringing of cymbals and sibilance in speech.
- 16,384 to 32,768 Hz 11th Octave - Beyond brilliance, nebulous sounds approaching and just passing the upper human threshold of hearing
Human Hearing, Bass, and Infrasonics
- 8 Hz - 64ft Organ pipe - only two in the world - Atlantic City and Sydney - wavelength 140 ft in air at 68F, 145ft at 104F
- 16 Hz - Lowest note for tuba, 32 ft organ pipe, Bösendorfer Imperial grand piano, wavelength 70 - 73 ft
- 32 Hz - Lowest C on a standard 88-key piano, double bass, bassoon, wavelength 35 - 36 ft
- 64 Hz - Bass saxophone, cello, wavelength 17.5 - 18.2 ft
- 80 Hz - 1100 Hz Human voice, wavelength 1 - 14 ft
- Recording Studio Digital Mixing Consoles 20 - 20,000Hz +/- 0.5dB
To select the right speakers for your home cinema:
Decide if it is looks or sound or a combination of the two that you want - This does not mean compromise, it just directs you to the choice of speaker types.
Choose between 5/7.1 and immersive soundtracks. If you go for immersive you have to allow for ceiling speakers.
We are going to explore immersive because almost all new films are adopting this.
The Perfect Set-Up:
If you are starting with a blank canvas choose 11 identical speakers and 3 subwoofers.
The front right and left, plus all surrounds should have speakers at ear level and the center
should be as close as possible to ear-level.
Start with one subwoofer in a corner, one midway between center and left or right, and one
towards the rear of the room. Final positioning is dependant on measurements.
The left and right surround should on an axis with the primary listening position.
The rear surrounds should line-up with the front left and right.
The height channels are positioned depending on the seating layout, all seats should have
some degree of front height and rear height directionality, i.e., the rear height speakers should not be in front of the rear seats. On the other hand - if you are the only one who cares about this, make sure your seat is directly centered on all four height speakers.
Start with the Immersive height channel speakers because this will determine the choice of the other speakers
In-ceiling, On-Ceiling, or Off-Ceiling
Sometimes you cannot mount identical height-channel speakers on the ceiling, but if you have the height and choose the right speakers, On-ceiling speakers can be a good choice and they reduce the sound transference to other rooms.
If you can go In-ceiling, this is aesthetically the best choice.
If you have enough height and can make it work, Off-ceiling or stand-mounted ceiling speakers will get you closest to what most immersive recording studios have.
In-Ceiling Speakers are the least obtrusive
(They can have a back-box (cabinet) or be open)
Open-back, in-ceiling speakers, are not necessarily worse than box speakers. With box speakers you have cabinet resonances and, if poorly designed, poor frequency response.
In-Ceiling speakers have no cabinets to resonate and the bass response is determined by the acoustic volume behind the speakers, the bass roll-off will start sooner and be gradual-around 12dB per octave. With good DSP you can easily match this to your subwoofers.
In-Ceiling speakers with a back-box will have a steeper roll-off because they will typically be a sealed enclosure the roll-off will be closer to 24dB per octave. If the back-box is ported, the roll-off will start later, and be steeper at 48dB per octave. These are general rules for all sealed and ported speakers.
In-Ceiling speakers are typically dual concentric designs
(i.e., the tweeter sits in the center of the bass/mid driver.)
Is this good or bad?
Dual concentric designs have been around for a long time. Tannoy embraced this many years ago and placed the tweeter right in the center directly over the pole-piece/magnet where you would normally find the dust cap. KEF adopted the same design. Most in-ceiling speakers place the tweeter on a bridge, flush with the front of the bass/mid driver. Which is best. The Tannoy design has two challenges, magnetic interference, and horn-loading. The bridge design allows the bridge itself to interfere with the frequency and polar response of the bass/mid driver.
The advantage of either is a better, or more consistent, off-axis response. Why is this important?
Good off-axis frequency response is critical for good sounding speakers
With all mid and high-frequency drivers, when you move to the side of them, or above and below, the sound level starts to drop. Unfortunately with poorly designed drive units, it does this unevenly across different frequencies. You may say, “well, I’ll just point all the speakers directly at myself”. This is not just wrong for other listeners but, since a lot of what you hear is reflected sound (all of which is off-axis), it does not really fix the problem.
In a two-way design, both the tweeter and the mid/bass driver have different off-axis curves and this can introduce phase problems as well. Dual concentric and bridge designs avoid the phase problems because the drivers are aligned.
Now imagine a system where there are different speakers for the center, surrounds and height channels, add in the left and right, and you have 4 different on and off-axis response curves.
The choice between different speaker formats is largely dependant u[on aesthetics and practicality. The most important thing is to try and stay with the same speaker for all channels. If you love your two-channel-system keep it, and add an 11 channel system for immersive sounds, or at least add an identical 9 channels. Use 3 Subwoofers, use DSP to fine-tune a flat response to below 20Hz.
For further insight and explanation, you can always check out The Daily Hifi, The Hifi Summit Q4 episode where our own Sales Director Simon Spears takes you through this whole presentation
Entry Level - On-Ceiling suggested system HiFi Summit Special $899.99.
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