123.211.144.116
In Reply to: RE: Hmmmmmm... posted by KlausR. on July 04, 2009 at 06:35:34
I quite appreciate your point about reducing reverberation time and actually think I get more benefit from that than from the smoothing of room response I get from my bass traps. Given the non-rectangular shape of my room which results in 1 more axial mode than I would get in a rectangular room, plus some additional oblique and tangential modes as well, plus the 2 open archway entrances which open the room to other spaces, variation in level of room modes isn't as extreme in my room as it would be in a closed rectangular room. The gain in bass clarity from reduction of reverb time, especially at modal frequencies, is subjectively a stronger gain for me in my room.
But there's no way of getting only a single benefit from any absorption treatment. You can't reduce reverb time at bass frequencies without smoothing room response, and you can't reduce reverb time at any frequency without reducing the overall level of reflections relative to the level of the direct sound. Any change we make brings other effects besides the one or ones we're particularly chasing. It's quite possible that a person may have a preference for untreated first reflections but on balance prefer acoustic treatment at a first reflection point simply because gains elsewhere are more important to theme and outweigh what they might perceive as a loss from the reduction in early reflections.
While lab experiments can be designed to isolate specific effects, and the studies on the effect of treating reflections weren't done by treating reflections but by simulating them with a secondary sound source whose level was separately controllable to the level of the "direct" source, we can't isolate and treat individual effects once we start actually treating a room. Put in a given treatment and you have to accept all of the effects produced by that treatment and all you can do is to assess the overall result of that treatment compared to the original untreated sound and decide which you prefer. It may be hard to tell which effect is most responsible for someone's preference for one over the other.
In my case my preference is definitely for treatment at side first reflection points but those reflections have a big effect on the L/R symmetry of the sound you get and for the last almost 30 years now I've had my system in 2 asymmetric rooms, each with a different form of asymmetry. Treating the side wall first reflections in each case has resulted in significant improvements in the symmetry of the sound field and I respond strongly in favour of that outcome. I've also been an amateur musician and instruments and voices sound more "natural" to me when the direct sound is stronger than that of the reflected sound, but that's the way voices and instruments sound when you're standing next to them or playing them and the walls are some distance away. Musicians can't avoid listening in the near field and what sounds "natural" is the sound you're used to so it's not surprising that Toole comments that musicians tend to be more sensitive to side wall first reflections than others and prefer the level of those reflections much lower.
When I listen at someone else's place, in a symmetrical and untreated room, I don't have a problem with side reflections. The sound is simply closer in some ways to what I hear when I sit in a hall to listen to a live performance and the reflected sound is stronger relative to that of the direct sound than when I play myself or stand close to a performer, even in a normal sized living room. I don't find anything wrong with that but it doesn't have the same "feel" as music does when I'm the player or I'm in close proximity to a friend who's playing and those experiences are the ones which really inform what I regard as the "sound" of music, what seems "natural" to me. I suspect that if I ever manage to find myself in the position of having a rectangular, symmetrical room, I'd opt to treat the side wall early reflections just to get that same strong direct/weak reflected sound combination for the sort of music I mostly listen to which is small group and solo performers.
On the other hand, I do have a preference for untreated early reflections with symphonic and big band music, music which I've only heard from a position in the audience in a concert venue but that kind of music is music I don't listen to regularly. If it were my main fare in recorded music I'd be adopting a different approach to room treatment than I have, even in an asymmetric room.
So, my main point here is simply that I don't think it's possible to simply say that there's no need to treat early reflections because there's no evidence that they're detrimental. You can't treat early reflections without affecting some other things, including reverberation time at frequencies over the absorption range of the treatment, and there's no way in practice to restrict the effects of any treatment to the ones you specifically want. It doesn't make sense to me to say "don't treat early reflections because there's no evidence they're harmful". It makes sense to me to point out what the effects of treating those reflections is going to be on different aspects of the sound and to say to people that if you're chasing one or more of those effects, then that sort of treatment can help you get what you're looking for but if those effects aren't what you want then don't go that way which is the way I try to deal with these questions.
Too many of the people asking questions here, and even some of the respondents, seem to think that there's really only 1 way to treat a room and that any room treatment is always going to result in the same sort of audible outcome. That simply isn't the case and it is possible to steer the outcome in different directions by treating a room differently. Whatever we do, however, we end up with a "package" of outcomes that can't be individually treated with no effect on other outcomes. What counts in the end is whether a given "package" suits you better than another package.
You can certainly enjoy the reduction in reverberation time in your room from your ceiling treatment but it comes with a cost that includes significant bass trapping and a smoothing of the room's modal response which you can't avoid. There's no treatment that will reduce reverb time at low frequencies without also providing the effects of bass traps, just as there's no way to smooth a room's modal response without reducing reverb time. You have no idea of how things would sound in your room if you could reduce the reverberation time to its current level at each frequency while not affecting smoothness of modal response or changing the level of reflections you would get from the untreated ceiling. You can't achieve that reverb time result without those other effects and your preference for the results you're getting may be due as much to the benefits of the unavoidable bass trapping and reduction in ceiling reflections as it is to reduction in reverb time. You simply have no way of knowing because you can't get one without the other, just as I have no way of knowing how much my preference for treatment at lateral first reflections is due to their benefit in reducing L/R asymmetry in the soundfield in my room and how much is due to the change in balance of direct and reflected sound in my room because I, likewise, can't get one without the other.
I think your reading has taught you a lot about the trees but when we get to our rooms and what we can and can't do in them we're dealing with forests and a forest is something different to simply a given number of trees in close proximity to each other. The behaviour of forests is not simply a magnification of the behaviour of a single tree. You can't consider room treatment in terms of what its effect on one or more specific features will be in isolation from each other or ignore what other effects are going to occur and the way the different effects will combine depends a lot on the nature of the specific room. How we perceive those effects depends a lot on what our experience of live music is and what aspects of recorded music we find most critical to our enjoyment of it. Theory is most certainly a useful guide but it's certainly not a reliable predictor of overall results for a specific user of a specific room. It would be a better predictor if the relative strengths of different issues were the same across all rooms but they're not, and if we could control a single parameter within a room without affecting other parameters but we can't and neither of those things is going to change so theory is always going to have to be tempered with an appreciation that any given treatment won't produce the same effect in every room and that we can't change one characteristic without changing others at the same time.
David Aiken
Follow Ups:
Post a Followup:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2009, Audio Asylum, all rights reserved ]
[ Go Green ]
[ Take5 ]