RealTraps - The Manhattan Home Theater

A treatment design for very small rooms

..BIG SOUND IN SMALL SPACES..

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Figures 1-3: The drawings above show top, front, and rear views of the room. Click the images to see them full size.
By Jim Lindenschmidt

This article provides a design for the ideal home theater in a small room. The room is 10x14x8 feet, which actually is quite roomy by some Manhattan standards! It's also a great concept for people who want to transform a spare bedroom, or part of a basement or garage, into a great-sounding space for a home theater or 2-channel listening room.

This design was implemented using Google SketchUp, a free 3D drawing program. The original SketchUp file is available HERE in a Zip file so you can explore the design for yourself and even make changes if you'd like.

The main function of this design is educational; we will outline the treatment plan and explain why each treatment item was chosen. Note that this article does not recommend electronic products - speakers, receivers, and so forth. This design will work beautifully for any type of audio system, creating a space in which even modest gear can dazzle you. Top

One thing you will notice about the room at left is there are no doors or windows. This is done intentionally, since doors and windows are rarely where we want them. However, if you are building a room like this from scratch, you should put the door on a side wall behind the seating. For existing doors and windows we recommend either stands for the traps, or having the Ideal Rear Wall Kit (diffusors on 2x2 foot MondoTraps) in front of windows. Another option for doors is to mount the panel using our Post Base Mounting method.

The chairs shown are large home theater chairs, but they could easily be a single sofa or a loveseat. A loveseat is preferable because then one person can sit in the center. However, in a well-treated room, being exactly in the center is much less important. This room has a surprisingly large sweet spot thanks to the lack of all early reflections.

ROOM LAYOUT AND REFLECTION CONTROL

The first thing to place in a room is the listening position. Here we follow the 38 percent rule as described in our article How to Set Up a Room. This places the seating 38 percent of the room length measured from the back wall. In this 10x14 foot room, that's 8' 5" from the front wall. This is a good theoretical starting point for the flattest bass response before bass traps and other treatment are added. Top

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Figure 4: This drawing shows the NARAS (Grammys) recommendation for ideal surround speaker placement. Click the image for a larger version.

 

"With all of the RFZ panels in place you will hear imaging and detail, dialogue clarity and dynamics, like never before."

Speaker placement is then based on the listening position. Following the NARAS setup recommendation for 5.1 surround sound shown in Figure 4 at left, the main left and right speakers are 30 degrees from center, and the rear surround speakers can be between 110 and 150 degrees from center. Because of the small size of this room, the surround speakers will likely be closer to the listener's ear than the main speakers. Therefore, a small delay is needed so their sound arrives at the listener's ears at the same time as sound from the main speakers. Most surround sound receivers or decoders let you set a delay for each speaker using the speaker distance setting.

You'll also need to experiment with subwoofer position. See our Subwoofer Placement article for one approach. A good starting point places the subwoofer near to one of the main speakers.

The Reflection-Free Zone (RFZ) concept should be familiar to anyone who has spent time on our site. If not, the article Creating a Reflection-Free Zone explain the basics. For this room we'll use a total of 8 RealTraps RFZ Panels - 2 on each side wall at the first reflection points to cover all 5 speakers, plus 4 on the ceiling. Note that the ceiling RFZ Panels are not shown. They are clustered together and centered in the room left-right as well as front-to-back. With all of these RFZ panels in place you will hear imaging and detail, dialogue clarity and dynamics, like never before. Top

SIDEBAR: IS TRULY GREAT SOUND POSSIBLE IN A ROOM THIS SMALL?

A setup like this is referred to as "near field" because the listener is very near to the loudspeakers. Some audiophiles believe they must be far away from the speakers to get a natural sound with realistic imaging and good impact. In truth, being close to the speakers gives the most natural sound because that minimizes the contribution of the room. It may seem counter-intutive, but when the small sound of the room is eliminated completely, music from the speakers then sounds much larger.

Small room ambience usually sounds bad because the reflections from nearby walls are very strong due to proximity. Reflections from nearby surfaces also arrive "early" which reduces clarity. Indeed, professional recording engineers often listen near-field for the same reason.

If you think about it, a wall that absorbs 100 percent of the sound is acoustically equal to a wall that's infinitely far away. In both cases sound goes toward the wall and never comes back to the listener. Between the absorption and diffusion used here, the room sounds much larger than it really is!

--Ethan Winer

CORNER TREATMENT

We have kept this as simple and effective as possible. All of the wall-wall corners have an Ideal Corner Kit - 1 Corner MondoTrap plus 2 TriCorners. Additionally, 6 more Corner MondoTraps are placed in the wall-ceiling corners. Rounding out the bass trapping is a single 2'x4' MondoTrap, resting on the front wall/floor corner. This trap is thick enough that it doesn't even need to be mounted - it simply rests on the floor at the wall-floor corner.

You can't really have too much bass trapping - the more you add, the flatter and more accurate the room becomes. The extensive treatment in this room ensures you'll have no boomy, unclear bass caused by room resonances, or lose clarity at mid and high frequencies due to early reflections. Top

REAR WALL TREATMENT

The rear wall uses 3 Ideal Rear Wall Kits, each containing a Diffusor resting on top of a 2x2 foot MondoTrap for even more bass trapping. There is not a lot of room to spread out the diffusors in this space. Diffusor arrays work best when the sequence in the well depth does not repeat, so we'll use a mixture of our Near and Far Diffusors since the two models have different well depth patterns. Because the Near Diffusors offer more bass trapping, and because the Diffusors are so close to the listener, we will use two Near Diffusors on the outside, closest to the corners, and one Far Diffusor in the center to break up the well pattern and give better overall diffusion.

Between the diffusors in the rear and the semi-reflecting membranes on the front of the bass traps, this small room will still sound spacious and definitely not sound too dead.

PASS THE POPCORN

The result of this setup is a small space that will sound much more even and controlled than larger, untreated rooms. The bass response will be tight and accurate, the sonic detail that will come from your speakers will mesmerize you, drawing you deeper into the music or the video. Even in a very small room like this, you can achieve exceptional, world-class sound! Top

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