Originally Posted by BassThatHz
Not just theater of the month. This is the best overall theater I've ever seen in "my entire life"... thus far. DAMN SON!
If I had $2-400k to spend on a single room, I'd probably do something similar...
Soundproofing 1khz and up is easy as it only takes 3-4 layers of drywall or OSB to I bet the only time you can take all those 24's and open them up wide is when the wife is out shopping etc...
I couldn't imagine that she would "actually" let you pound them at even 1/4th of their full potential, at least if she is in the same room or even within 300ft of it.
I asked Keith to give a more detailed response. We took a lot of care to soundproof the theater so that my wife wouldn't be woken up in the middle of the night. The pictures I uploaded don't show the whole story. Anyway, I hope this will be interesting:
We start the design of an effective wall, ceiling or other barrier by creating a target Transmission Loss (TL) graph that quantifies how many decibels of TL are needed at what frequencies. To create that TL graph, we ask yourselves two straightforward questions:
1. How LOUD
should we assume it’ll be in the source room (the Theater) when the system is being “exercised” and
2. How QUIET
do we need it to be in the receiving room (the Master Bedroom in this case).
We get your target TL curve simply by subtracting the decibel values in #2
from those in #1.
Q1: How LOUD in the Theater?
KYD’s spec for the subwoofer element in the Hahn Theater was based on the premise that the installed system should be capable of linearly reproducing recorded LFE content throughout the 10-80Hz range at 120dB at all 15 seats. That’s an ambitious goal for a room whose internal volume is >10,000 cubic feet. (It’s not much of a challenge to get high dB results at low frequencies in much smaller rooms.) In this case, “linearly” means steady-state (not just peaks), free of audible distortion (generally agreed to be <10% total harmonic distortion in the subwoofer range), with no audible or measurable signs of power compression or non-linear artifacts (port chuffing, driver noises, etc.). I also wanted “useful” response down to 8Hz, which brings me to…
Reality Check: The Hearing Threshold:
It’s helpful to keep in mind that getting a subwoofer to play down to, say, 2Hz may make for interesting conversation among fellow audiophiles, but if the maximum reproduced level is below 120dB, it’s inaudible to persons of normal hearing. Per Moller and Pedersen, 2004, the hearing thresholds are:
Two of my acoustic engineers, Andrew and Luke, assisted by Kyle and Mike, ran in-situ tests just after installation of the custom UberSub system using calibrated Bruel&Kjaer (B&K), G.R.A.S., Larson Davis and Earthworks microphones feeding B&K and Larson-Davis sound level meters, an Audiomatica CLIO sound measurement system, and various sound analysis software packages from B&K, LDL, and AFMG.
During the August 2015 site visit the team verified that we’d handily met the 120dB design objective at 10Hz and above. In all cases the THD was <3% fo This result was expected, as we’d done extensive finite element (FEA) analysis during the design phase, and room gain measurements during White Box testing many months prior to the UberSubs being installed.
Q2: How QUIET does it need to be in the Master Bedroom, 20 feet away?
While the Theater was in full cry we wanted levels at the Master Bedroom, about 20 feet away, to be below the Sleep Disturbance threshold. Sleep Disturbance is a complex subject involving number of occurrences in a night, level above background, and other factors beyond the scope of the discussion here. But, as a useful approximation, the World Health Organization “Night Noise Guidelines 2009” specifies a 42dB LAmax threshold for sleep disturbance where the disturbed party is woken up at night.
Probably obvious here, but we didn’t use a Sound Transmission Class (STC) specification for this purpose, as STC doesn’t specify data below the 100Hz third-octave band, i.e. it’s pretty much a useless metric when dealing with subwoofer-generated sound transmission into nearby areas.
Insulation Measurement Standard:
For the Hahn project, our low frequency measurements were conducted according to the British Standards Institute (BSI) standard BS EN ISO 16283-1:2014 (Acoustics – Field Measurement of Sound Insulation in Buildings and of Building Elements). This standard establishes a method for low-frequency SPL measurement down to 50Hz. For the purposes of our testing, the frequency range was extended down to 12.5Hz.
Equipment and Technique:
Measurement equipment consisted of a Larson-Davis Labs (LDL) Model 824 Real Time Analyzer equipped with a G.R.A.S. 40AN ½-inch low-frequency microphone. The measurement system was calibrated with a LDL CAD200 acoustic calibrator before testing. The measurement setup meets all pertinent requirements of the American National Standards Institute (ANSI) for Type 1 (precision) sound measurement systems. Other equipment used in the measurements included pink noise source and audio amplifier with dodecahedron loudspeaker [seen in some of Rob’s photos in this thread], along with the Theater UberSubs to energize the room throughout the frequency range of interest.
One-third octave band sound pressure levels were measured within the source (Theater) and receiving (Master Bedroom) rooms from 12.5Hz to 8000Hz. Measurements were conducted using a manually-scanned microphone with a room averaging time of approximately 60 seconds. Four corner measurements were also conducted using a stationary microphone with an averaging time of 60 seconds.
The Theater to Master Bedroom testing was conducted by calculating the overall noise reduction provided by the building construction between the Theater and Master Bedroom. There are two primary wall construction types and a distance of approximately 20 feet separating the two spaces. Five (5) permanent sound-gasketed doors were installed at the time of testing. The overall noise reduction provided by this intervening construction was calculated as third-octave noise reduction (NR).
The noise reduction (NR) from 12.5Hz to about 50Hz was in the 45 dB range; above that, noise from the theater failed to exceed the ambient noise level in the master bedroom, so the actual NR at 63Hz-8000Hz is substantially higher than reported.
As the measurements show, with the LFE energized to the Dolby/THX Reference Level of 115dB (steady state, not just peak) by the UberSub system, the level in the Master Bedroom barely 20 feet away would read 33 dB(A), and is well below the Sleep Disturbance threshold.
Hope this helps. In the few days, I'll upload our final NCB rating graph...
Rob Hahn Theater build
An Evening With Rob Hahn