Improving the Sound of an Audiophile's Listening Room Through Acoustic Consulting

by Nyal Mellor March 29, 2015

Customer Profile

The client, Mr.Jackson, of Corte Madera (California, USA) wanted to improve the sound quality of his main two channel system. Here is what Mr. Jackson had to say about his setup before we started: "I had always known that getting good sound out of a room involved more that just good equipment. I was aware that there would be optimum speaker placement and an optimum listening position as well as room treatments, all of which combined would maximize even frequency response and dispersion and ultimately my listening enjoyment. My own, amateur efforts over the years included umpteen different speaker positions and the basic 2" absorber panels at first reflection points. Not to mention, numerous and expensive hardware upgrades in the quest for better sound. It was not until I purchased a Velodyne subwoofer with it's basic frequency measurement utility that I realized I had some serious room issues and would benefit from professional Help.

The happy client with a RPG BAD panel used for lateral reflection point control custom mounted to a RealTraps stand.

Project Overview

Authors note: This was actually the first project we ever did for a paying client! Mr. Jackson's system, like many of the clients we help, contains a lot of high end equipment (all in all over $60,000 dollars of equipment). This isn't unusual but we have assisted clients with more modest systems ($10,000 dollars invested).

• A Meridian 808.3 CD player with the latest apodizing filter
• A high end turntable
• VAC pre and power amplifiers
• Avalon Indra speakers
• Velodyne DD-12 subwoofer
• Crystal Cable interconnects and speaker cables
• Existing acoustical treatments from Echobusters

Mr. Jackson's room is quite typical of the clients we deal with on a day-to-day basis. Most of us do not have the luxury of dedicated listening rooms or home theaters - this room doubled as the principal lounge in his modest residence. The whole lounge / kitchen / office space of his residence is all open plan and he had a large 50" flat panel television positioned between his speakers. The lounge area is quite narrow and has windows along one side and an open fireplace (luckily not in use) on the other side. The left speaker was positioned next to the corridor leading to the office whereas the right speaker was in a room corner. As you can gather from my description this is not a straightforward space in which to get good sound! One of the happy positives was that Mr.Jackson's wife was accepting of her husbands audio habits and so allowed acoustical treatments to be used within the space. For more discreet installations we can get quite far by utilizing the ceiling for acoustic treatment and also by 'hiding' acoustic panels in plain sight.

Acoustic Frontiers Solutions

Room Acoustic Analysis - a review of the systems current acoustic design, done by performing critical listening using our reference recordings, taking acoustical measurements and reviewing the system against our set of acoustical best practices.

Acoustic Treatment Design - determining what acoustic treatment is required to solve the room acoustic issues. For this project we used absorber panels and combination absorber / diffusers (the BAD panel) from RPG. 4" thick panels were selected to provide additional bass absorption. The client and consultant had a number of discussions over e-mail and phone about different treatment options, the benefits of 4" over 3" panels and color choices. Due to the installation difficulties presented by the window, fireplace and open corridor adjacent to the left speaker we custom mounted these panels to RealTraps stands.

The room with acoustic treatment added

System Setup. During this step we systematically optimized system setup, first focusing on bass response and then on imaging / soundstaging.

• Subwoofer setup. Because the system had a subwoofer the first step was to determine the crossover frequency, slope and phase. Don was not using a crossover on his Avalon Indras and had complained about a certain muddiness in bass reproduction when the subwoofer was playing. Using acoustical measurements we determined the frequency response of the Avalons and their roll off. With this knowledge we set the subwoofer to roll in as the Avalons rolled off. Phase was a bit more tricky to setup since subwoofers often have longer group delays than main speakers and in the case of the Velodyne also have a time delay caused by the DSP processing. Since a two channel setup does not have an electronic delay we setup the phase by trial and error so that frequency response was smooth at the crossover.
• Speaker boundary interference optimization. The system had a deep suckout in the mid to upper bass due to coincidence of a number of speaker boundary related cancelations from the side walls, back wall and ceiling. To ameliorate these we analyzed the boundaries that were causing the suckouts and moved the speakers so that the cancelations did not coincide. Due to the room layout and practical considerations (e.g. distance of the speakers from the rear wall) it was not possible to fully remove the negative effect of these cancelations.
• Room mode optimization. Analysis of the acoustical measurements showed a couple of problematic room mode related resonances. The first step here was to find out if the current listener position was optimal. By taking frequency response measurements at the listening position and then at increments of 6" further and back we were able to find a better position 18" forward of the current position. Obviously we were limited by the practicality of speaker / listener distance - it has to be within a certain range and that range varies depending on the speaker in question, with multi-driver box speakers often sounding better at 12-13ft distance or greater. The second step was to utilize the equalization in the Velodyne subwoofer to remove the audible boominess of a couple of room modes. We used our own measurement system to analyze and set the EQ filters as the automated process in the Velodyne does not produce optimal results.
• Imaging / soundstaging optimization. During this step we tweaked speaker separation and toe in to optimize the balance of imaging precision versus envelopment. The preparation was to setup a grid on the floor spaced in 1" increments. Using this grid we were able to move speakers in a repeatable fashion - both closer together and further apart. The client remarked on how one could clearly hear the difference of a 1" change in separation to the overall balance of imaging precision versus the feeling of being enveloped in the sound.

The Results

These following charts show the improvement realized through acoustic treatment and calibration. You can see the response is a little flatter through the bass and the suckout from 50-100Hz is reduced in level. We also managed to remove a high amplitude reflection at about 18ms after the direct sound.

Energy time curves, before and after acoustic treatment

Frequency response chart showing before and after calibration results. You can see the dip from 50-100Hz is slightly filled in and the dip around 45Hz is gone.

Finally, what did the client think? That's the important thing - if they are not happy then we are not happy! In the clients words:

"The end result of Nyal's analysis and implemented strategies is a much more even in room frequency response (particularly in the bass region), and much cleaner, more focused and enveloping musical presentation. I heartily recommend Acoustic Frontiers for anyone seeking to improve performance of their stereo or home theater sound system"

And what did we think? We were very happy with the improvement in sound quality that was achieved for a relatively minimal investment - less than 10% of his system's retail value!

Whilst the finished room did not meet 'reference' standards from an acoustical perspective, it is virtually impossible to achieve that without a dedicated space. We had reduced the severity of the acoustical distortions caused by room modes, speaker boundary interference and strong reflections.

One has to realize that doing acoustic design and calibration for shared spaces is always a process of finding a compromise between aesthetics and performance. It is a process we find challenging and enjoyable.

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