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A video journey into PS Audio's new music listening room
by Nyal MellorJune 05, 2013
PS Audio are rebuilding their music listening room and Paul McGowan, the CEO of PS Audio, has published a video blog of the journey.
In part 1 Paul talks about the center point of the new room - a pair of Infinity IRS 5 speakers which weigh almost one ton! These speakers are 7.5ft line arrays from the 1980s with separate mid/tweeter and bass array cabinets. It is very interesting that PS Audio are using a speaker that has long been discontinued as their 'reference' speaker. Why aren't they using a new currently available speaker like a Magico, YG, MBL, Rockport, Wilson?
In part 2 Paul talks about wanting to get the equipment out of the room and tidy up the system cabling. Amen brother! It's a mystery to us why most audiophiles tolerate the stack of equipment taking up valuable floor space with python like speaker and power cables on elevators to get them off the floor. In high end home theaters we place the equipment out of the room in a spare closet or purpose built equipment cupboard. You can also see the existing acoustic treatment which includes RPG Diffusor system and Acoustica Applicata DAAD diffusors.
In part 3 Paul talks about the room dimensions, the rule of thirds, the precedence effect and the effect of sound isolation on in room bass quality.
The PS Audio listening room was sized such that the room dimensions correspond closely to the Golden Ratio which is a ratio of 1 to 1.61. As an example if the height of the room was 10ft then the width would be 16.1ft (1.61x the height) and the length 25.9ft (1.61x the width). The theory behind this is related to the distribution of room modes. A room whose dimensions correspond to the Golden Ratio will have an even spacing of room modes which theoretically means more even bass. There will still be room modes and the room will still suffer from their negative effects, particularly in the sparsely populated modal region (below 100Hz) but they will not cluster around specific frequencies like they would do with dimensions that are squarer.
Whilst the Golden Ratio seems popular due to it's mythical properties proper studies by acousticians into room ratios have given other results. Louden, Bolt and Gilford all looked into room dimensions and came to slightly different conclusions. Thankfully Salford University have a good Room Sizing Tutorial which summarizes the key historical research as well as more up to date thinking on the matter. We at Acoustic Frontiers believe that room dimensions are important - call them a good starting point for good bass - but not that the be all and end all. Wall construction, acoustic treatment, speaker placement and listener placement still matter. There are also many ways to work around non-favorable dimensions such as using multiple subwoofers in mode canceling arrangements.
The rule of thirds is a generic speaker and listener placement methodology again to do with getting smooth bass response. The theory goes that the speakers should be placed one third of the way into the room and the listener two thirds of the way into the room. This puts both speakers and listeners in areas of moderate room mode activity. Paul however confuses the rule of thirds with the precedence effect and his explanation of the precedence effect is wrong. The ear/brain sums the direct and reflected sounds and that is what you perceive as the sound. See the first four paragraphs of our article on listening room reflections for a proper and correct explanation.
In Parts 4 and 5 Paul talks about Helmholtz absorbers and how they are planning to using them to absorb some of the lowest room modes at 25 and 37Hz. Broadband bass trapping that absorbs higher frequencies are briefly discussed and rejected as a potential solution which is true - very low frequencies would require a huge depth of absorption to be effective below 40Hz. However PS Audio's room will still have room mode issues due to the stiff wall construction - double drywall - which I believe they are taking care of using the freestanding Acoustica Applicata DAAD absorber / diffusors previously used in the room. Paul also talks about punching holes in his sound isolation shell to use the cavity between the ceiling rafters as a Helmholtz absorber...well that will work but now you have seriously compromised that isolation shell you spent so much time and effort building!
If this video has inspired you to create your own music listening room please get in touch - Acoustic Frontiers specializes in room acoustic analysis, acoustic treatment design and system setup and would love to talk about your project!