Boston Section

The Boston AES chapter held the April 2001 meeting at Goodwin's High End, Waltham, MA. Ira Leonard introduced Alan Goodwin as the evening's speaker: "Ever since I can remember Alan Goodwin was an icon for good sound and hifi in the Boston area. Six years ago Alan settled in Waltham and really has been developing this ever since--and it gets better every week. As you'll see when you move around, there's more to happen. The stretched cloth room treatment didn't get done yet--but several rooms will be treated with it. And so you'll just have to come back to hear it and see it. But without further ado, here's Alan Goodwin."

A rewritten synopsis of Alan Goodwin's talk follows:

I built my first soundroom in 1974 and have been involved with building rooms both for my own purposes and for clients ever since. The first purpose-built soundroom that I ever experienced was in early 1974ãand among other things it had custom saw-tooth side walls to minimize slap echo. This was at one of my first really high end client's house in his basement. And the combination of that room and his high end stereo system really impressed me--as it was the best sound I had ever heard at the time. And since that first formative experience I always thought that saw-tooth acoustic treatment was a good idea. The first soundroom that I helped build in my first store, also in 1974, was a shoebox with the floor built at the front of more than one height. It also had double sheetrock, however at that time neither ASC nor RPG existed, and so whatever the acoustic treatment was had to be handmade.

In the 1980's both ASC and RPG came into existence, and I was privileged to spend time one-on-one with both Art Noxon and Peter D'Antonio in those early years learning about their respective approaches to acoustic room treatment and experimenting with them.

I first met Mike Blackmer in 1976--and at that time he was a audio technician. He became very interested in acoustics--and one day around1982 or so, he called me up and asked me if I wanted to attend an acoustics seminar with him in NYC. So I went with Mike to this 3-day Syn-Aud-Con conference on studio control room acoustical design. Basically in that one large room were, at the time, some of the most respected acousticians of the day from all over the world assembled all in one place. By immersing myself in this "world" I absorbed the concepts that were considered "cutting edge" at the time. It was a seminal experience for me in terms of my development and understanding of room acoustics for both the recording and the playback of music.

Basically from that experience I found that the pro audio people had developed the room acoustics pretty well--but that they didn't have the level of quality of equipment that the high end audio people had. And vice versa. So my idea became to combine the best of the pro world, which was the room acoustics, with the best of the high end world, which of course was (and is) the high quality equipment.

So it has now been 27 years that I have been thinking, off and on, about rooms in terms of sound isolation, shell size and internal ratios, and internal acoustic room treatment. However since building this facility in 1995, I have been really focused on this area much more.

When I went to plan this facility, I called every person I could think of that I had met over the past 20 years with acoustical expertise or experience to ask their advice. Of course I got all sorts of different opinions as to what they thought was best. So after many months of countless hours of talking and thinking, I finally made a decision about how to build the shells--and decided to experiment with different acoustic treatment for the interior of the rooms after they were built so that I could hear for myself what type of treatment worked the best.

There are a total of 6 listening rooms here. Each room is actually freestanding, in that each room has walls that are independent of each other and the ceiling for each room rests on the four walls. That way none of the room's walls or ceilings touch the exterior walls or roof of the building itself. And each room is basically independent of each other for good sound isolation. Five of the rooms are multilayered sheetrock with Decidamp damping material compressed between them--to form a constrained mode layer damping system of construction. Five of the rooms also have the perimeter skin isolated from the studs by application of Z-metal.

There are actually four sizes of rooms here: very small, small, 3 medium size rooms and a large room. The three medium sized rooms are all identical in terms of size and the construction of the walls, floor, and ceiling. The carpet is also identical. When I built this facility in 1995 my idea was to have these 3 identical rooms built to use them as my own in-house applied acoustics laboratory. That way I could treat each room differently and walk from room to room in order to "A-B" (compare) different room acoustical treatment. Treating the rooms and then listening and measuring, and then modifying or changing the treatment and listening and measuring again, really sped up my understanding of applied acoustics in the realm of "small room acoustics". (Large room acoustics, for concert halls for example, is slightly different.)

After a year or so of experimenting with my three medium size rooms, I treated this large room that you are now in. What is also interesting is that this large room is the same ratio of dimensions as the three medium sized rooms here. And so I initially took the same treatment scheme that I used in the medium room right next to this one and applied it in here. One thing I learned is that large rooms are more expensive to treat! But also, all things being equal, that a larger room (up to a point anyway) is to me preferential for listening to the playback of music.

For this particular room, after tweaking the first room treatment scheme for 9 months or so, I gutted the room and put in a new prototype of room treatment. After 6 months or so of tweaking, I gutted that and started work on a new type of treatment with Mike consulting to me. The results of which you can see here--and the third time's a charm! Everybody seems to like this room quite a bit. In fact we have had people from all over the country come here and say that this was their favorite room that they have listened in! And in my opinion Mike is a genius! Basically the room size and ratio were my decision--and the calculation of the angles and panel sizes you see here came from him. As for the shell construction and corner trapping--they are from Art.

In terms of room ratios, when I went to lay out the rooms, I found that the ratios of dimensions that people were using to design recording studios weren't suitable for residential usage for the most part. The reason is that by the time you got to a longer length, the ceiling became too high. An example of this is a typical room that is 10' x 14' x 19'. If you extrapolate that to a 25' or 30' room, your ceiling is too high for most buildings. And in many cases even 10' is too high as many rooms today are built with 8' ceilings plus or minus a foot or so. So I spent a lot of time calculating room modes for various room sizes and came up with one that has a more reasonable ceiling height. Generally we use ceiling heights between 8.5' to 11'. Although sometimes when working in a basement we are down to 7'!

There are also some features of the room that are not immediately obvious. Above the ceiling are some still-air boxes that Mike designed to quiet the HVAC system. And if you look in the rear corner you will see a trough that goes out of the room, down the hall, and into the next room. That was designed for microphone cables, so that we could record in here and have an uninterrupted passageway for the mic cables to pass to the listening "control" room next door.

The story on the room treatment is that this is the first room like this. Prior to this a small room using this kind of thinking was built for recording voice-overs. But for music this is the first one. Basically my idea was that I wanted a room that was symmetrical end-to-end and side-to-side.

Prior to this some the best rooms that I had heard music in were made for the speakers to only fire one way. And the front of these rooms was totally different from the back. Most of you are probably familiar with live end/dead end rooms. Or the type of room that is slightly fan-shaped; where you have many angled facets on the front and side walls and ceilings feeding diffusers on the rear wall. The goal of this second type of room design is to not have any direct reflections for the first 20 milliseconds or so in order to achieve a "reflection free zone" at the listening position. However none of these types of rooms are symmetrical nor are many of these easily tunable.

This room here is symmetrical as speakers, when listening in stereo, can be used at either end of the room with basically the same results. This is good for doing A-B comparisons. Also speakers work really well facing the width of the room. In addition this way we can do surround sound playback systems in here. I am a believer in a symmetrical sound field for surround playback. And the only way to achieve this is to have identical speakers all the way around in a symmetrically treated room.

In addition the room was designed for music recording. By tuning the room to be more live, this type of treatment lends itself well to recording live acoustical instruments. The only thing that I decided not to do in building the room was float the floor and the entire structure of the room on it. That would have given this room much greater isolation from traffic noise, which you can't really hear, but which microphones can pick up especially at the lower frequencies through movement of the earth from passing vehicles--even though we are 100' or so from the street out front.

The tuning of the room can be achieved by several methods including: rotating the corner traps, half of which are absorptive and half of which are diffusive. And by rolling up the large rug and removing it--as well as removing some or all of the black absorptive strips from the room. What is interesting is that when you do this, the room becomes progressively more and more live--and yet the sound is still controlled.

I can assure you that going to the effort and great expense to completely gut and retreat this particular room three times was a decision not taken lightly. And especially this last approach, being something that was never done before for music, was to some extent a leap of faith. However ultimately this was a labor of love--and I am very pleased with the results.

Now that this room has existed for a few years, we have measured it and spent countless hours listening in it. And at this point we now know how to make this design slightly better in future iterations. Learning is a never-ending process! And next on the agenda, all of the other rooms in here are going to be retreated--another never-ending process it seems!

- Ira Leonard