Rational Acoustics

March 4th, 2018, 12:22 PM

I am very new to SMAART and audio measurement in general, so the following is probably riddled with ill assumtions and wrong conclusions. However, I am amiss where the faults are, so I am posting it here, hoping to learn where I went wrong.

As a very simple first exercise I set out to level tops and sub of my living room soundsystem.

Initially, I set subs and tops to the same level to get a relatively flat response. Listening to music with this setting and comparing the tonality to that of relatively flat monitoring headphones, bass was more or less completely missing.

I increased sub level by 6dB, ending up with the attached traces (once measured at ear height, once directly on the floor). Even at this setting, I need to add a +10dB low-shelf to achieve the same tonality as the monitoring headphones.

While I think I understand that a flat system might not provide the tonality with regards to bass response that I am looking for, I am still really confused that I aparrently need a 16dB offset between sub and top level to match the tonality of the monitoring phones.

Is this to be expected? Or does this hint to some issue in my measurement procedure or hardware?

All Best,


March 4th, 2018, 03:33 PM
Good news, the short answer is that youíre on the right track; what you found is expected. Iíll let someone more experienced with mixing give you the long answer.

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Chris Tsanjoures
March 6th, 2018, 03:15 PM
Hi le.chris -

You are 100% going in the right direction. What you have stumbled upon is the effect of system drive level and that effect of perception of loudness (thing equal loudness contours). That at the level you are driving the system, it is likely that your +18 subs are exactly what is needed for the system to sound 'correct' for that room volume. I've reached out to a friend at Dolby for the cinema x-curve variance per level, as soon as I hear back i'll let you know.

As an experiment, if you have the ability to calibrate the mic input for SPL - you can measure your 'it sounds good here' tuning to the Dolby x-curves + subs, which are included in Smaart (thumb around page 80 in the v8 user manual). As you will see, with a broadband system at 72db, it is expected that the subs would range from +10 to ~+14. So anyway - yes, you are on the right track, and at the end of the day - if it sounds good it is good!

- C

March 8th, 2018, 12:28 PM
As Chris and Johnny said, you're on the right track. Attached is screen shot from Dolby AT5 analyzer (customized older version of SMAART that Dolby techs used), showing where we align main LCR speakers and where level of subwoofer is suggested (+ 10dB). "Flat" doesn't sound good to most people in most situations, and the majority of loudspeakers and systems are in fact designed or aligned to have a boost in the low end. For better or worse, that's "normal." Your headphones likely have a low end boost as well. Unless you need to conform to an exact playback curve (as in cinema or TV work), make it sound like you want it to sound. And yes also, measure and test your system at a decent level, loudness perception and equalization change with level. 986

April 6th, 2018, 04:11 PM
I have the ATMOS software on my Mac..... Has all the levels on the software... pretty basic though compared to a lot of DSP software. Its fixed IO so super simple.