My Home Theater Design and Construction

The outside shell. External Kitchen Wall studs with rack room recess below and room door opening to its left hand side.

After years of using the family living areas as make do listening and viewing rooms I finally had the opportunity to build my own dedicated home theater, or as I prefer to call it My A/V Room, and so I started my home theatre design and construction project. The room is not a Home Theater in the classic sense of the phrase. It was primarily designed for listening to music with video projection more of an add on or after thought.

The following is the first in a series of posts presenting a fairly detailed description of my home theater design and construction. At the conclusion to the design and construction posts there will be an additional series of posts that review its acoustic performance in detail, the installation of an additional pair of subs with lots of details and dos’ and donts’ and other room ‘tweaks’.

Let me first of all say I am not a great fan of ‘pretty’ home theater rooms, if you have the need, time and budget that is fine, but that is not what I was looking for, nor was I interested in support for 3D. I wanted to put as much of my money, as I could, into the acoustics, and audio and video technology of the room.

Having my roots in both the professional music recording industry and secondly in broadcast video I wanted a room that gave me great music performance for stereo and 5.1 audio with support for 2.4:1 video and 11.1 film sound.

My Requirements

Due to an extensive remodeling of my home, I had the opportunity to add ‘my own piece of heaven’. A dedicated music room that supported video projection. It had to meet many criteria, some of which were:

Within budget – it was not elastic.
Acoustically well controlled before the application of any electronic EQ.
At least a 60dB sound reduction index (SRI) to the main home, as I like it loud at night. Well anytime actually!
A background noise rating (NR) of 20dB or better with HVAC active.
A flat reverb time (RT) of 0.2 secs. from at least 63Hz to 20KHz.
No windows for total light control.
No secondary decay. This is decay from another space within the room.
Acoustically symmetrical for all audio modes; stereo, 5.1, 7.1, 9.1 and 11.1.
The screen & projection system to support both 16:9 and 2.4:1 aspect ratios.
To support vinyl playback.
To seat three people.
The room’s technical systems to support:

Separate 100 amp 120VAC single phase supply; straight from the house main 200 amp board.

Separate safety ground from main house system.

Isolated technical ground system.

Balanced line levels to all active speakers.

SD/HD SDI support for most hardware, I hate HDMI and HDCP.

Green pure sine wave UPS, only active upon power loss– not double conversion due to audible noise.

Well that was a start for now. I also had to deal with the realities of the various building code issues such as an old in-ground pool, local streams and building lines that cut through where the room was to be built. These issues dictated the maximum room size if I was not to exceed the budget.

Construction Introduction

The room was to be part of a new renovation, not a separate building. So it was designed as a fully isolated ‘box within a box’ in order to reduce noise transmission, and to have its own low velocity ducted HVAC system. The noisiest equipment, the projector, was to be installed inside the room, its noise criteria (NC) rating was 27dB, but the room design supported its movement to an external placement if it became a noise intrusion.

The resulting available space provided for a room that had a finished size of 18’ 6” L x 12’ 8” W X 8’ H. These selected dimensions provide the most uniform spacing of all room modes and met a number (but not all) of well-known acoustics criteria. There are many pieces of free software that can be used to provide an idea of the basic acoustic properties of a room. One of the better programs, which is the one I often use, is Modewizard by John C. Griggs. It may be downloaded from Studiotips Acoustics Forums.

The resulting room dimensions and layout restricted the placement of subs to either two at the front 1/3 in from each side wall or four by adding one in each rear corner, (you will see why later). This is not the optimal placement as defined by a number of white papers but is just about second best. The other restriction that rapidly became apparent was that width speakers were never going to be possible so I deleted that requirement.

Acoustics & HVAC Introduction

Although my goal was to design the room to have acoustics similar to a recording studio control room, it was not practical/necessary to have the speakers raised above the floor as in many recording studio control rooms. This would have severely restricted the screen width and I did not want to use a perforated screen. Also due to space restrictions and access issues the door had to be almost in the center of a sidewall and the equipment rack needed to be located within the room on the same side as the door. This ‘rack room’ was also to form a plenum chamber for 30% of the HVAC air entering the room, besides cooling the equipment. The remainder of the air was fed through plenum chambers behind the front LHS/RHS speakers. The returns occurring from plenum chambers behind each of the larger rear surrounds. You may ask what is a ‘plenum chamber’? It is just a large acoustically lined space into which the ‘high’ velocity HVAC air enters and slows down. The air’s sound is absorbed and then it gently ‘filters’ out into the room at a very low velocity through a number of outlets.

Equipment

So what equipment was to go into the room? I purposely chose the main five speakers to represent types that were frequently used in recording studios and cutting rooms and that had a THX PM3 rating. All the satellites needed to compliment and closely match their frequency response and power handling with the crossover frequencies to all HF units ideally being the same. I already had a pair of subs that I liked and were a good match to the selected 11 satellite speaker system and had sufficient output to drive a 1900 cubic ft room. I say 11 satellite system, as there was to be two pairs of surrounds. The larger pair matched the front three speakers for 5.1 music, the second smaller side wall pair were film surrounds. Each surround pair was appropriately positioned to meet their performance requirements.

A/V equipment List:

5 Genelec 1038’s for music and film
4 Genelec 8040’s for rear and side film surrounds
2 Genelec 8030’s for film front heights (added later)
2 SVS PB12 NSD subs
2 SVS SB2000 subs (added later)
Gaines balanced line interface to drive the subs
Audyssey XT 32 Sub EQ for initial sub equalization (now removed)
SMS1 equalizer for initial sub EQ
3 ME30B one third octave equalizers for LCR EQ (added later)
Rane AD22d – for sub distance matching
Denon AVP-A1HDCI with Audyssey XT32 upgrade + Pro kit.
Denon DBP-A100
Denon DVD-3800BDCI + HD SDI mod
Denon DVD-5900 + SDI mod
Toshiba HD A35
Oppo 103
Thorens TD160S turntable + Hadcock GH228S arm + Lentek Entre1 cartridge and head amp.
iScan VP50 Pro with HD SDI
Darbee visual processor (added later)
BenQ W10000 with ISF calibration by Kevin Miller
Panamorph UH380 lens with automatic sled
Da-Lite Matt tensioned dual mask screen – 115” diagonal for 2.4:1.

Initial Room Layout

So what did the initial room design end up looking like? The following drawing shows the ceiling, wall and floor configurations, acoustic treatments and layout.

My Initial A/V Room Design and Layout

For those readers who don’t want to wait for and wade through all the posts and must have a little peak at the final outcome, click on the following links for a very brief look at the final results:

The next post in this series will review the rooms acoustic construction techniques, discuss why, and post foundation, floor and framing pictures.

Click here for all My A/V Room construction posts.

From Vinyl To Plastic

One man's quest for audio perfection