Is your listening room acoustically treated?

[David A]

I could see value in professional guidance PROVIDED you somewhere where there is a professional who specialises in small rooms because acoustically our rooms are quite small. Then there's the question of how much you want to spend. If you're embarking on a project of actually building a dedicated listening room from the ground up, then you've got a major building expense ahead of you and spending a bit more on professional advice is likely to be a significant part but not the major part of the total cost.

I suspect it's a different thing if you're just looking to treat an existing room. The only expense there, besides professional guidance if you get it, is going to be the cost of the acoustic treatments you install and professional guidance is going to be a much greater part of the total cost if you use to. If you're trying to cut costs, doing the job without the professional guidance is probably the major cost cutting decision you can make.

I'm in an audio club here in Brisbane. The only consulting acoustics person I know of usually works on jobs like school halls and much larger spaces and as far as I know he doesn't take on smaller jobs like home listening rooms. While he's the friend of one of our club members, an architect, and has helped that member on some of his projects I've never heard of him providing guidance for any other club member or audiophile. Let's just say that, depending on where you live, you may have problems finding someone local to help.

How hard is it to do yourself? I don't think there's a simple answer to that question.

There are some books you can turn to for advice. The first book I used was F. Alston Everest's "Master Handbook of Acoustics" and the other book I've used, and now prefer to rely on, is Floyd Toole's "Sound Reproduction/Loudspeakers and Rooms". Everest's book is more oriented towards building a home recording studio and/or editing room than towards home listening rooms. It goes into some depth on how sound behaves in rooms, how acoustic treatments work, and how to build your own DIY treatments. It does quote research findings, many of those findings coming from the research of Floyd Toole, but in several significant areas Everest's recommendations on how to treat a room are quite at odds from the recommendations Toole makes based on the same research. Rather than placing a lot of emphasis on the behaviour of sound in rooms, how treatments work, and how to build your own treatments, Toole tends to emphasise the research on how people respond to various aspects of sound in a room and what aspects of sound they prefer, and his recommendations for treatment are based on those studies of listener preference. A simple example of the difference between the 2 books is that Everest recommends treating first reflection points while Toole recommends leaving them untreated saying listeners tend to prefer the sense of spaciousness first reflections can provide though he also notes that recording engineers tend to have a preference for treating first reflections which probably explains why Everest's book, which is aimed more towards home recording setups, recommends treatment of those points.

When I first started experimenting with treating my own room Toole's book hadn't been written and I followed Everest's recommendations including treating first reflection points. I liked the results. When Toole's book was published I bought it and read it and found myself rejecting Toole's recommendations. It took me some years to start experimenting with Toole's recommendations and I was surprised to find I preferred them when I finally got around to trying them.

There is a big problem with both books when it comes to treating an existing room: they both discuss rectangular rooms and ignore irregular shaped rooms like L-shaped rooms (my current room is L-shaped) and neither devotes any time to discussing how to deal with asymmetrical rooms in general, open plan spaces, and things like windows in places which cause problems or open archway entrances from other areas (my room has large window areas on the front and back walls, 2 open archway entrances, and a corner on one leg of the L-shape is cut off at 45 degrees providing an angled reflective surface and 2 135 degree corners where you would normally have a single 90 degree corner).. Both leave you on your own when it comes to a lot of the things which can cause us problems when it comes to treating an existing room.

Guidance on the internet is a mixed bag. There's lots of advice on the sites of firms making acoustic treatments which tends to extol the virtues of their various treatments along with a "more is better" philosophy, obviously with an eye to sales. There is good information there but there is definitely a sales bias. Then there's advice from hobbyists like us, many of whom have strong opinions which don't agree with the research of people like Toole. One problem you come across is an argument about which is better, absorption or diffusion, with the people favouring diffusion making great claims for the benefits of a diffuse sound field. Concert halls have diffuse sound fields once you get a certain distance from the performers but they're much bigger than our rooms and it's impossible to create a genuinely diffuse sound field in a room as small as most of our rooms plus there's the issue that diffusion takes distance and time in which to develop and if you don't have enough distance between you and a diffuser you ain't going to get the full benefit from it and you may even hear unwelcome artefacts from it.

Another big issue is that the books I mention and pretty much everything I've read on the internet all seem to discuss the benefits of acoustic treatment in terms of correcting frequency problems, especially in the low frequency region. What you find when you start to play around with doing the treatment yourself is that how and where you treat the room also affects things like dynamic attack and how lively the music sounds, the sense of pace the music has (treatment in some locations can make the music seem to drag while moving those treatments to other locations can "perk it up"), and you can also make big differences in the way the soundstage and imaging are rendered. Sometimes moving a treatment from one location to another by a small amount, say 6" or a bit less to a foot or so can make a big difference in how the music is presented to you.

If you have a nice rectangular room and no problems with openings or window location and the like it's relatively easy to recommend a treatment strategy that will deliver good results BUT those results may not match with the recipient's tastes and preferences. To some degree those recommendations are also going to be based on speaker choice and placement and listening position placement. Change your speakers and/or their location and/or move your listening position and you're likely to find yourself having to move your treatments as well. A lot of the products sold to people like us are meant to be glued or fixed to the walls which makes it hard to move them if you change something and have to adjust your treatment locations, and impossible to use if there's a window or some piece of furniture where you want to place the treatment. Freestanding treatments are great for dealing with those issues but often far less attractive. On the other hand, having an air space behind an absorbing panel actually increases the absorption it offers and that means you need to treat less surface area of the room which will often result in a livelier sound.

When I changed my speakers from a 2 way rear ported standpoint to a 3 way front ported floor stander design nearly 2 years ago I had to move the speakers back about half a metre to the wall and start rethinking my treatment strategy to deal with the different way the new speakers loaded the room. The treatment placements I had been using prior to the speaker change worked reasonably well with minimal adjustments to their location to compensate for the shift in speaker position but I started playing around trying to get things working better. Moving my treatments was easy since they're all free standing but I played with their height on the stands and also started seriously experimenting with leaving first reflection points untreated and trying out other locations instead. After 22 months or so I think I've got things sounding much better but it's taken all that time because irregular shaped rooms like mine can be a real problem and, as I said, no one tends to give any ideas of how to deal with them. Would a professional acoustician have helped? I have no doubt they could have given me instructions on how to set things up but I'm not certain they would have recommended the setup I've arrived at and really like. There is no universally best treatment solution for a room, there's a whole family of good/best solutions which deliver different results and the *best* solution for your purposes is the one which suits your preferences. There's no guarantee a professional will give you that solution.

So doing it yourself can be easy or hard, take little time or a lot of time, little experimentation or a lot of experimentation. One thing you do get out of doing it yourself, if you spend at least some time playing around with placement of treatments and paying attention to the results that delivers is a much better understanding of what kind of sound you're looking for, what the room you have is contributing to the sound you're getting, and how to work with a room to get good results. That kind of experience is invaluable in my view but getting to a result you're happy to live with long term can take a lot more time and effort than you initially think will be involved. As i said, I've spent 22 months now playing with my room on and off since changing speakers and that was a real surprise. In the past with standpoints and my current room or another small room it's never taken me more than a few weeks to get things to the point where I was happy with the result.

This is probably too long a post in many ways but I hope it at least gives anyone who's contemplating acoustically treating their room an idea of what can be involved in the process, some of the things you can end up having to deal with in "real world" rooms rather than the idealised rectangular boxes that are almost always discussed, plus the idea that it can end up taking more time and work than you initially think may be involved. Would I do it again? Yes, but hopefully it would take me less time if I have to do it again because of some of the things I ended up learning this time around.