Sony G90 manual Deploying the Troops RPG Room Optimizer Software, 59 by

Now that your head is swimming, choose

your dimensions. The actual dimensions you

select based on a ratio such as those listed

below will determine the exact frequencies at

which the modes will develop. Jim Thiel, the

engineering brain behind Thiel speakers, calculated the fol-

lowing set of ratios:

2.5	by 1.6	by 1	2.18	by 1.6	by 1
1.39	by 1.14	by 1	1.54	by 1.14	by 1
2.33	by 1.6	by 1	1.9	by 1.4	by 1
1.9	by 1.3	by 1	2.1	by 1.6	by 1
2.5	by 1.5	by 1	1.59 by 1.26		by 1

I chose to build a room that measured 33’3” long by 22’9”

wide by 8’9” high. That’s 3.8 by 2.6 by 1. At the time, I thought

it was permissible to double any of the numbers (it isn’t). I

place the speakers. Perhaps the best known is the Rule of

Thirds (put the speakers at the one-third points away from the

side walls and back wall). The Rule of Thirds is derived from a

superficial understanding of modal room characteristics. This

approach, which seems to work with dipole loudspeakers, is

less than optimal for dynamic coil designs.

There is no predictable location that works optimally for

all speakers and all rooms; the variables are too numerous.

Indeed, finding the absolute best location for a certain speak-

er in a certain room is extraordinarily difficult (unlikely, but

not impossible). Now, though, there is a useful tool to credi-

bly attack the location issue: Room Optimizer software ($99 a

copy) from RPG Diffuser Systems, Inc. You quickly learn,

when using Room Optimizer, that what is optimal depends on

where you sit, on the geometry of the speakers, and their loca-

tion. Fortunately, Room Optimizer will consider all those vari-

ables for you.

Diagram 1: Room Mode Calculator

by Allan Devantier

doubled two of them in the 1.9 by 1.3 by 1 ratio. Plug these

numbers into our Excel spreadsheet and the resulting plot of

modes looks something like Diagram 1.

Despite my mistake, the room ended up with a good

spread of modes (save for a pile-up at 50 Hz). Being somewhat

skewed myself, I chose not to build a perfectly rectangular

room (see Diagram 3, page 46) although I built it fairly rigidly

with studs that were on 12-inch centers and two layers of dry-

wall (the floor is concrete). I wanted an equipment room I

could walk into to change components and cables, and I want-

ed an opening from that room into the media room. I also

decided not to wall off the entrance to my office at the end of

the media room, leaving a floor-to-ceiling opening. Finally, I

have always suspected that rooms with bay windows or simi-

lar broken angles behind the speakers sound better. So I

framed in three-foot facets where the side walls meet the

front wall. If I ever get the chance to do it again, I would do it

a little differently – but that’s another story.

Deploying the Troops –

RPG Room Optimizer Software

Nothing is more important to good sound than where you

choose to place your speakers. Over the years there have been

numerous attempts at simple empirical formulae to help you

Room Optimizer, in simple terms, does the math for you.

It combines a modal analysis with a Speaker Boundary Inter-

ference Response (SBIR) analysis based on the legendary

work of Roy Allison. It is the combination of these two

approaches that makes Room Optimizer unique and useful.

Balancing the modal and SBIR analysis, Room Optimizer

searches out locations within your room for your speakers

and your listening location that will meet a certain threshold

frequency uniformity. See Diagram Two for a graphic repre-

sentation of a solution that Room Optimizer found for the

Salons in my room.

I will eschew a detailed technical explanation of how

Room Optimizer works and concentrate more on how well it

works and its limitations. Know this about it: It will “do the

math” on many thousands of locations, relentlessly honing in

on the optimal location within parameters set by the user.

Room Optimizer randomly selects a starting spot within user-

defined boundaries. This random starting point influences

Room Optimizer’s search for the optimal location. Once it has

a starting spot, it works around that location gradually refin-

ing the search. Different starting locations lead to different

final solutions. For this reason, it can and usually does come

up with different solutions when fed identical parameters.

Thus, it is worthwhile to spend some time at the computer,