General Asylum: REVIEW: Michael Green Designs Pressure Zone Controllers Other by Jim Bookhard

There have been three reviews, to my knowledge, which have been written on the MGD Pressure Zone Controllers. The reviews appeared in Positive Feedback, Home Theater magazine and at Soundstage! All of the reviews were positive, but having used these devices for about three years now, I realize that none of the reviews really tell how these devices work in the average listening room or home theater environment. So, I thought I'd try to explain a few things about these devices that the reviews did not get into, although the reviews were thorough and factually descriptive of PZC performance. One of the other reasons that I'm writing this review is that usually whenever I respond to a post here at the Asylum, or at other sites, on the usage of PZCs, I usually end up getting email with additional questions. Hopefully, this review will answer questions for those who are not totally aware of what these devices are. The review by Home Theater (February, 1998) was a shoot-out between ASC acoustical products, Echo Busters and the PZCs -- Home Theater designated the PZCs the winner, though all products in the shoot-out performed well. One thing which is not obvious and which was not mentioned in any of the reviews mentioned above is that these devices do need time for the "tuning" boards to break in completely. They sound good right out of the box, but their sound gets even better, as their wood cures, over time.

These devices are not really the successors to the "pillow" type acoustical products by MGD because they work on totally different principles. These devices also do not rule out using other acoustical methods out there, but they are incompatible with absorbent panels, traps, etc. Whether or not these devices are for you will largely depend on your room properties/construction materials and whether your room has any grossly unusual acoustical anomalies. The best thing for those considering acoustical treatments for their room is to look into the DIY type treatments, such as those by Jon Risch, companies like ASC, RPG, Echo Busters and Argent. In other words, do your homework before choosing any one method by getting as much "good" advise as possible and not just "guesses" by novices. Also, you should take the sonic signature of your current system into consideration -- does it sound dry, rich, lean, neutral, etc.

The PZCs do not require any special level of technical expertise on the users part to install, use nor to adjust them. But, a room should never be "self-configured" by a "first time user" of PZCs. You just need to follow some basic guidelines about getting started using them. Pressure Zone Controllers (PZCs) are variably tunable acoustical devices which, when installed in a music listening or home theater video room (or a recording studio, church, gymnasium, classroom), have the ability to variably alter the pitch and the amount of harmonics of the acoustical energy created in a room (i.e., if your room has a "dry" sound, you can add more natural richness to the sound by increasing the amount of harmonics produced by adjusting the PZCs). You can also balance out sound in a room (i.e., a soundstage which leans to one side or the other). In addition, they have the ability, through proper placement, to allow the user to build up energy in a particular area of the room or to tone down energy in a particular part of a room in order to produce musically correct harmonic structures.
A PZC consists of a wood tuning board which is attached to a open box design wooden frame. The frame is filled with a very small amount of acoustical burn material and covered all around by fabric. At the front mid point of the wood tuning board, which faces into the room, there is a brass tuning bolt which attaches to a tuning mechanism inside at the front of the box frame of the PZC. By adjusting this bolt (clockwise or counterclockwise) with a supplied Allen wrench, the user can vary the frequency at which the tuning board will resonate. In properly configured room, adjustments of an eighth of a turn of one of these bolts can easily be heard, by even an "untrained" ear.
Acoustical energy, created in a room by a loudspeaker, tends to build up near the intersection of surfaces of a room. Since corners of a room are comprised of three surfaces intersecting, much of a room's acoustical energy buildup usually will occur here. Also, the ceiling is the one area of a room which does not have furniture, carpeting, etc., so this is the least controlled area of a room, from an acoustical standpoint. There are a variety of sizes of PZCs, the most common of which are -- upper Corner Controllers, Mini Echo Controllers ( vertical and horizontal designs available), 36" tall Wall Mounted PZCs (vertical and horizontal designs), 48" Floor Standing PZCs which have their own base stands (with brass cones for mechanical grounding), Ceiling Controllers and 48" Wall Mounted PZCs. A "standard configuration" of PZCs does not exist. There will be a different configuration (number and placement) of the PZCs for every room. There are however, general common locations which need to be treated in a room. The one location users will always want to treat will be the upper corners of the room. Next, any areas of the room with an abundance of energy which needs to be better controlled should be considered as well as areas of a room with too little acoustical energy (i.e., rooms with lean bass or rooms with treble or midrange with insufficient harmonics).
The wall mountable PZCs mount by using drywall screws and plastic anchors (assuming a room with sheetrock walls). The PZCs which are designed to mount in the upper corners or the mid corner position of a room come with a pre-drilled mounting bracket which has the proper angles cut on the edges of the bracket to fit properly across a 90 degree corner -- these PZCs also mount with drywall screws. The tools you will need in order to install PZCs are a drill, drill bit (size of the wall mount anchor you choose), a ruler, a level, a pencil, a small hammer and a screwdriver. The PZCs mount like pictures onto the mounting screws and can be removed or taken down at any time. The front wooden tuning boards of the PZCs have a few options. You can choose from base coat (can be painted to match the color of the room), black and white. Cherry is available at an additional cost. The frame cloth color options are ivory, black and gray.

When a loudspeaker energizes a room, acoustical energy migrates to the room surfaces much the same way as water from a filled glass spills over -- some splashes up, some runs across the table over the edge and some just sits on the table. Acoustical energy will enter the frame of the PZC and resonate sympathetically with the wood tuning board in front (actually any acoustical energy coming in contact with the tuning board will do the same from the front also). So, acoustical energy is taken in at one frequency and released back into the room at another frequency, based on the setting you have chosen for the front tuning board.
Let me describe some of what you will experience with these devices. Let's say that you play a recording with a solo piano (to pick an easy example to understand). Picture in your mind what a real piano sounds like, noting the decay time of the notes and amount of harmonics of the notes produced by piano. You now listen to the recording of a solo piano. By adjusting the tuning bolt(s) in front of the tuning board of each PZC, you can vary the amount of harmonics and the decay time of the notes the recorded piano is producing until it matches what you know, in YOUR mind sounds like a real piano. Everyone hears differently (as we all also see differently), so what sounds real to you is what your brain interprets as "real". You can sustain decay time and create more harmonics if needed by allowing the tuning board to resonate longer (a "loose" setting of the tuning bolt). You can shorten decay time or the amount of harmonics produced by a tighter setting of the tuning bolt. Again, the variability of the adjustment of these devices allows you to shape the sound of any room environment. Also, some people like lean bass while others like rich bass. Neither is right nor wrong -- simply personal preference. Basically, these devices work by taking in acoustical energy, converting that acoustical energy into mechanical energy and then releasing the energy back into the room as acoustical energy, but at a modified frequency(s) and with a different length of decay.
Every room has its own sonic signature. That signature is dictated by many factors like construction materials, type and placement of furniture, carpeting, drapes, windows, doorways, alcoves, dimensions, shape, etc. Generally speaking, walls constructed from hard materials such as cinder block, plaster, concrete or gypsum (other factors not considered) will generally produce a bright sound, lean but tight bass, a relatively cooler midrange. Walls constructed of sheetrock have the potential to produce good sound in a home environment. Walls constructed of sheetrock over OSB (this has to be scientifically applied, not dimensions picked out of the air) produce even better sound. The PZCs can be adopted to all of the above room conditions because they are variably tunable. To a degree, they can actually "liven" up a "dead" sounding room. To a reasonable similar degree, they can tame bass boom caused by corner horn loading or add harmonics to a room producing lean bass. Remember, I said "to a degree". An acoustically bad room is an acoustically bad room. Whenever you are applying acoustical treatment, start out getting the room "prepared" for the best sound first. Eliminate all the negatives, within your personal acceptable limits of lifestyle, spousal approval, aesthetics, etc. If given a choice, use smooth leather furniture and keep the room as "live" as possible. It is always much easier to lower the pitch of a room than to raise it, so you should start out with as "live" a room as is possible.
In addition to the wall mountable PZCs which mount onto the wall surfaces, there are other devices (for those constructing a room from scratch) that do the same thing as the PZCs, but are mounted into the room surface structure themselves. There are In Wall Tuners, In Ceiling Tuners and In Floor Tuners. When these devices are used, an entire wall, floor or ceiling section reacts just like a PZC and this is what's called a "Tunable Room" (I did a review on the Tunable Room here at the Asylum). These devices can also be retrofit into existing rooms. The In Wall (mounts between studs), In Floor and In Ceiling Tuners are the same devices. Loosening the In Wall/Ceiling/Floor Tuners will increase bass response and harmonics because the room surfaces will "flex" more. So, with these devices you have ultimate control over your room acoustics. You do not need to use these devices with PZCs -- PZCs can be used by themselves to acoustically treat a room.
There is no such thing as a "standard" minimum configuration of PZCs, but based on my experience with them, you should at least treat the four upper corners of your room, at least as a start. The size of these devices (11"H x 6 ½"W x 4 ½"D) belies their effectiveness in a room up to 20' x 20' x 8'H (not that these are dimensions you want for your room; I'm talking about area of effectiveness, in my experience). You should not attempt to configure these devices for yourself, on your own. That's what the MGD hotline will do for you. They will configure your room based on room diagrams, information on construction materials, problem areas, etc., that you will be requested to supply and that they will discuss with you their recommendations for a configuration based on what you would like to accomplish with your room, what is aesthetically acceptable to you and what is within your budget. I put my current final configuration of these devices together over three years. Once you gain experience with these devices, the thing you will find is that you will be able to walk into a room and "feel" the room and what it needs. When you reach this level of experience with these devices, you can then start doing your own basic configurations. While listening you will develop a sensitivity of where energy is lacking in your room and where it needs to be tamed. The PZCs are incompatible with absorbent acoustical panels/materials of any type, but are compatible with RoomLenses. A good rule of thumb to gauge the sound quality of your current room is that if normal speech sounds good, music will sound good in that room. The PZCs will then allow you to shape the acoustic of the room to your personal preference. Once set up to your preference, they do not need to be readjusted unless you choose to do so or if you have an equipment change that alters the sound away from your preference.

REVIEW: Michael Green Designs Pressure Zone Controllers Other Review by Jim Bookhard at Audio Asylum