How Do I Test My 5.1 Surround Sound
Najla Ondik
If a subwoofer is used with limited-range main speakers, all 60 Hz tones should play at the same level through the subwoofer. (Hold SLM next to subwoofer) If full-range speakers are used, the 60 Hz tones should play through each speaker individually, though levels may vary due to standing wave or resonances in the listening rrom. The LFE signal is encoded 10 dB lower to account for the 10 dB gain in the LFE channel in the playback amplifer's bass management circuits.
If the decoder supports SBR, all four tones, 6, 8, 10, and 12 KHz should be heard (or seen on a sound level meter if you have high-frequency hearing loss). If the decoder is only decoding the AAC-LC portion of the bitstream, only the first two tones will be heard. This is at the encoded bitrate of 160 kb/s, at other bitrates the SBR crossover frequency used by the encoder will vary, resulting in more or less tones being heard. Missing tones in only one channel may indicate a speaker problem.
when your computer has 5.1 channel speakers connected or connects via HDMI to a 5.1 or better surround sound AVR or home theater system. Note that many browsers and media players (particularly on mobile devices such as the iPhone) will output a stereo downmix from these streams, even if they don't support multichannel output.
The AAC codec family has supported up to 48 channels of audio since its initial development through predefined channel configurations and a flexible escape mechanism. The predefined channel configurations from the 2005 version of the AAC standard are shown below, along with the additional configurations standardized in Amendment 4 of the AAC standard in 2013 shown in cyan tint:
This channel configuration value is specified in the AudioSpecificConfig structure of the AAC bitstream. When the channel configuration value is set to 0, the channel configuration is not predefined, but is explicitly described in the Program Config Element structure. This allows arbitrary channel configurations to be used. (For information on these structures, refer to the Fraunhofer Application Bulletin AAC Transport Formats or to the MPEG AAC standard: ISO/IEC 14496-3.)
Supplying the 7.1 configuration with the PCE escape method was necessary since the only predefined 7.1 configuration was the theatrical SDDS speaker configuration of five front speakers and two surround speakers. Thus, the more common BluRay 7.1 configuration with three front speakers and four surround speakers was specified using the PCE structure.
An amendment (ISO/IEC 14496-3:2009/Amd 4:2013) to the AAC standard also allows signalling the BluRay 7.1 configuration in the channel configuration field by using the value 12. An AAC decoder is also required to continue decoding configurations sent in the PCE.
More importantly, AAC lacked profiles requiring 7.1 support, with a level 4 or level 5 decoder only required to support 5.1 decoding. The amendment includes level 6 to require 7.1 decoding. Also, the amendment specifies a method for controlling the downmixing of 7.1 channels to 5.1 channels with controlled gains, much as the existing standard does for 5.1. The amendment also includes the extra loudness metadata currently specified in DVB into the AAC specification.
I have an old pioneer VSX-1021-K (7.1) receiver that I'm currently using but can't seem to make it just do 5.1...I can only do 5.1 with an option to put the rear speakers as the rears, or as rear surrounds. However I've noticed that some movies only use rear surround audio, or just the rear speaker channel but not rear surround, and sometimes both on newer movies.
Spoiler alert! Near the beginning of The Grey there is a plane crash from the passengers' point of view. We only have 5.1, with the surround speakers somewhat behind our heads, rather than directly to the sides as some people do. This creates a better sound image in our room:
During that scene there is sound all around us, with the kind of detail we might expect from many more channels, rather than 5.1. There were a minimum of 3 phantom channels down each side of the room, between the Right Front and the Surround Right, and Left Front and Surround Left, about 2 phantoms in the back of the room, as well as the usual 7 or so across the front of the room. So, counting physical + phantom, there were about 15 sound loci. There was even a suggestion of up and down, mostly up (all of out speakers have tweeters slightly above ear level). It sounded like we were surrounded by metallic walls, ceiling and floor which were breaking apart. So far, no other movie has provided such a convincing illusion in our room.
Holding the room and seating constant, the most important factor in providing how good the surround is would be how it is recorded, IMO. Some recordists and mixers take great pains to make sure it's good, others don't seem to care.
Others will suggest films with good surround treatment of music. Amadeus, Shakespeare in Love, Bohemian Rhapsody, the first crowd sounds at the very beginning of A Star is Born (2018) come to mind.
There are a few other things that may be different about our set-up. Because we have Klipschorns, the Right Front and Left Front speakers are placed in the corners, as opposed to the way they are shown in the diagram. The Klipschorns are 13.5 feet apart, tweeter to tweeter (16.75 feet wide, sidewall to sidewall). The front soundstage is a little wider, partly due to the surrounds and the Klipschorns painting the side walls with sound (sometimes). We sit about 12 feet from the center speaker, making the sound field just about 60 degrees wide. The 13.5 width doesn't conflict with the visual image width, because our projection screen is 130" wide ('scope 2.35:1). The center speaker (a modified Belle Klipsch) has had its distance electronically adjusted to the same distance as the Klipschorns by Audyssey (which does that in terms of time of arrival, down to 0.1 foot). The tweeters of the surrounds are a few inches higher than the front tweeters.
My go to scene for a demo for non atmos surround sound is in the first Jurassic Park when the trex is chasing the smaller dinosaurs and young Timmy says they are flocking this way. This scene on Blu-ray will rock a 5.1 or 7.1 setup. Every channel is very active.
I discovered this movie because Kathleen Battle sings the song whose leitmotif is featured throughout the movie. I think this movie would surprise a lot of people - it's not really about martial arts. This scene where we first see The Echo Game is pretty cool - Mei can't resist the challenge of The Echo Game, and it becomes apparent that she is not the "poor helpless blind girl" she pretends to be. Zhang Ziyi is gorgeous ...
Testing surround sound setups can be a lot of fun. One of my go-to movies for this is "Interstellar." There's a particular scene where the spaceship takes off, and the sound design really immerses you in the experience. You'll feel the rumble of the engines and the sweep of the music in all directions. It's a great way to check your system's ability to handle various channels and effects.
Also, if you're into checking out movies, you might want to see new movies out this week. You never know what exciting films are out there that can provide an amazing surround sound experience.
- Click the "Configure Speakers..." button in the bottom right of the window. Click the "Multichannel" tab. Then select "5.1 Surround" from the pull down menu. Click on each speaker to provide a test tone to make sure each is connect properly. Then click on "Apply"
- Last set is to go into the DVD Player to test it. Go to "Preferences" and click on the "Disc Setup" tab. Under Audio at the bottom of the window select "Digital Out - SONY AVAMP" from the drop down menu for "Audio output" *You now have 5.1 Channel Surround Sound from you Mac!
I have a follow-up question to this original post... I haven't tried any of this yet since I just ordered a new iMac and haven't received it yet, but will definitely try it out once it arrives (on my cheap RCAreceiver haha). I know it has poor reviews on Walmart, but honestly, I've had this for about a year now and absolutely no complaints. If configured properly, the device works flawlessly. Not the best speakers, but not bad... Definitely loud. Just don't know if it'll work with the new computer.
ANYWAY, my question is: As long as the setup from the original post works and 5.1 audio is outputted from the Mac, has anyone tried using a surround project with FCX with this setup and if so, how stable is it? This is my only reason for wanting to output in 5.1, but I just want know if anyone has encountered any problems with it.
Thanks for the response! I haven't been able to output in 5.1 because my iMac won't read the receiver correctly. It usually lists my recevier as "LCD TV" and only gives me the option of two channels. I guess I can fool around with it. It may be due to my TV actually being hooked up to the receiver at the same time as the iMac, so instead of just decoding audio, the computer thinks I'm trying to use my TV as an external monitor (which only uses two channel audio). In fact, now that I'm writing this I think that's my issue. I'll play around.
Looks great for DVD player, but how do I get iTunes to recognize the multichannel settings? Testing speakers in the midi setup worked to get test tones out of my surround and sub but no go with iTunes.
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