The bass peaks just aren’t loud enough for full impact. Not to mention, brightness, dwell, resonance and all the sonic subtleties that make the difference between just being able to hear the track, vs. having the track invade your very soul - haunting you for an entire week.
So, - What the devil is this “headroom”?
You don’t hear the term “headroom” in our industry much. Check out this case study:
Worked in a machine shop as project manager in the mid 70’s trying to fund our fledging AV company. Had about 15 detail machinists, 10 welders, and 6 assemblers, all using pneumatic tools.
The compressor was driven by an old ‘68 GM 350 2bbl, delivering a realistic 170 or so horsepower. That motor was well over a decade in age and was run for 15 hours a day, 6 days a week.
No one was ever short on air power. The 60-year-old facilities guy kept the oil, coolant, and plugs changed, and toped. That motor was run well under its capabilities, we call that “Headroom”. The objective of reliability was met, heard from an old buddy, that motor lasted another 14 years.
To restate: the engine had much more capability than required, that is headroom.
How does headroom fit in today’s problem? Time to unwrap this a bit. A great starting question could be: “do you have any idea how much amplifier and cone area it really takes to drive immersive sub-sonic frequencies in your client’s theater room?” Also “how do you know?”
As your engineering DNA starts kicking in, terms like total room volume, room dimensions, surfaces, reflections, absorption, resonations, seating placements, acoustic room isolation, and budget are all competing for their proper prioritization in your theoretical design.
As Tony tells it, this author gets the feeling that he always brings a gun to the knife fight, so to speak, when specifying this component, he is most comfortable specifying more amp & speaker then most would think necessary.
When you default to a standard sub frequency speaker, one that you may have used in the past, you could be under-addressing this opportunity and missing out on what really sets you and your client’s home cinema apart.
Furthermore, you are potentially missing out on a truly great opportunity to immerse users into the wonder, amazement, and magic that is delivered by music and great cinematic art. Not to mention word of mouth recommendations that come with a great experience.
At its basic, core it is simple; it takes at least 110dB of clean and tight bass in a home cinema to get listeners to crack a smile. Many home theaters have plainly anemic bass that tops out at around 90dB at the needed frequencies, barely enough to get any reaction.
Solution: It takes horsepower and tuning: You need enough cone area, enough amplifier power, and multiple subwoofers that are placed for maximized room gain efficiency.
If you ever have a tendency to over spec on stuff this is a great place to start.
And then you need to carefully tune the gear, this takes some skill, so get up to speed on the relative delays, EQs and levels of the subs until you squeeze every last once of sound pressure across the spectral range of 20Hz to 100Hz.
Cannot be done without a spectrum or real-time analyzer, the right test signals, the right engineering talent, and without some time to make it all happen.