The argument for/against room treatment

(...) So imo it's not a matter of reflections being good or bad - it's a matter of minimizing the bad ones while encouraging and cultivating the good ones. Imo the loudspeaker design itself can play a significant role here... you ever try horns???

Duke,

Perfect - every good book says the same. The problem is knowing exactly what are the bad ones and what are the good ones. And we can't simply say the bad ones are those that must be minimized and the good ones are that can be encouraged and cultivated. :oops:

IMHO small rooms (something less than 50 square meters) for stereo are more an art than a science. And as such reflects a lot the personal views and empathy of the acoustic builder. I have talked with a couple of acoustic people that completely disagreed with my views of stereo music listening in aspects such as illusionary room boundaries or layering, or even typical sound levels. Surely having them treating my room would be a complete disaster.
 
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When I "hatch" my future stereo I will start with no room treatment at all (except for carpet on the rear two-thirds of the room). (...)
Pick the proper carpet and add a thick felt underlay - an inadequate absorber can be worst than no absorption at all. As far as I see it, the first floor reflections are a NO for people wanting layering and real depth perception.
 
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Hi Duke, you sidestepped a bit from my original point, which was that treating the room will not make a stereo system sound more real. It is still easy to distinguish live from reproduced both before and after treating a room...

Yeah, well, I think my experience has been different from yours. I've heard room treatment make what I consider to be very significant improvements, which to my ears did make the system (and imo "system" includes "room") sound more real, BUT I think it still would have been easy to distinguish between live and reproduced sound. Maybe you and I use the term "sounds more real" a bit differently? Anyway I think I understand what you are saying.

The problem is knowing exactly what are the bad ones and what are the good ones. And we can't simply say the bad ones are those that must be minimized and the good ones are that can be encouraged and cultivated. :oops:

Here are my thoughts on what are the bad ones and what are the good ones, taken from that post and a previous one:

... not all in-room reflections are equally beneficial, nor equally detrimental.

The KEY lies in the ARRIVAL TIME of the reflections (assuming they are spectrally correct, or nearly so, to begin with).

The earliest reflections are the ones which most strongly present the playback room's undesirable "small room signature" cues, and are also the ones which degrade clarity the most.

The later reflections are the ones which most effectively present the reverberation tails on the recording, which convey the recording venue's acoustic space (whether said "acoustic space" be real or engineered or both). As long as they aren't TOO loud clarity is preserved.

Imo the KEY is to get a worthwhile time gap in between the first-arrival sound and the strong onset of reflections...

Let me get a bit more specific about that time gap, if you don't mind. According to Griesinger, the ear gets most of its important information from about 700 Hz to 7 kHz. Reflections which arrive before we've had time to clearly process frequencies in this region tend to degrade clarity. The amount of time the ear/brain system needs to clearly process signals all the way down to 700 Hz is 10 milliseconds, so this is why you see Geddes and his groupies (including yours truly) tossing this number around. Ten milliseconds corresponds to the amount of time it takes for sound to travel 11 feet. Not saying this is a hard target, but rather a fuzzy one, with improvement from having a reflection-free time gap which lasts for even longer.

I'm NOT claiming the above is an all-encompassing examination of reflections in home audio; there are other things besides timing which matter, such as level and spectral content and arrival direction(s). And the ear sums reflections in ways which are not necessarily intuitive. It's a big subject, but imo looking around the room at WHERE the early reflections will occur can be a good starting point as far as WHICH reflections are potentially the bad ones. Imo @Ron Resnick is on the right track with his plan to start with the first sidewall reflections.
 
Yeah, well, I think my experience has been different from yours. I've heard room treatment make what I consider to be very significant improvements, which to my ears did make the system (and imo "system" includes "room") sound more real, BUT I think it still would have been easy to distinguish between live and reproduced sound. Maybe you and I use the term "sounds more real" a bit differently? Anyway I think I understand what you are saying.



Here are my thoughts on what are the bad ones and what are the good ones, taken from that post and a previous one:





I'm NOT claiming the above is an all-encompassing examination of reflections in home audio; there are other things besides timing which matter, such as level and spectral content and arrival direction(s). And the ear sums reflections in ways which are not necessarily intuitive. It's a big subject, but imo looking around the room at WHERE the early reflections will occur can be a good starting point as far as WHICH reflections are potentially the bad ones. Imo @Ron Resnick is on the right track with his plan to start with the first sidewall reflections.
Hi Duke, when I say "sounds more real" I mean that it is closing the gap between what is heard live and what is heard reproduced. IMO, the room affects both similarly and doesn't close that gap. It can definitely make significant improvements in the enjoyability of the sound.
 
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To me, room treatment includes materials of wall, floor and ceiling. For two rooms which one has wooden floor, wooden wall and the other room has marble floor and concrete wall will sound very different even if they are the same size. Just like guitars made of different hardwoods will also sound different. If my room has too much window, I try to cover them with wooden blind. Adding a sofa in the room is also room treatment. So everything in your room is room treatment.

I agree with your paradigm that "everything in your room is room treatment".

One of the best-sounding rooms I ever set up a system in was at my parents' house, about twenty years ago. My mom had spent decades collecting old wooden furniture and had completely lined the walls of a large spare bedroom with it. There was just a natural-fiber throw rug on the floor, and then all this big wonderful quasi-random wooden diffusion lining all the walls, and a few lightly-upholstered wooden chairs to sit in. I set up an inexpensive system in that room for my step-father, and it sounded better than it had in my larger, dedicated, "treated" in-home showroom!!
 
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Maybe those student digs from the 70s with vinyl stacked precariously on creaking shelves, in and out of the walls higgledy piggledy, books piled floor to ceiling, magazines all over the floor, plants (cannabis, anyone?), etc etc, sounded so good with entry level hifi...the acoustics were inadvertently already top notch. And the stash was good as well.
 
After reading a lot of this I think that maybe some are thinking of the wrong experts. I know very little about designing a concert hall or a recording studio however neither of these have anything to do with my listening room. I have been in many and I really don't think their goals were mine. Studio's are a whole different set of parameters. When I was at Lyric we hired some "experts to help design and build the rooms, and they were built well, however sonically only one of the four actually sounded ok and even that one need a lot of adjustment to correct what the "experts" had done. I never was in love with the results!
My two cents here is
1). position the speakers and get them in the right place
2). position the seating in the right place
if one needs help doing this hire the right "expert" and by this I mean someone that set's up home high end audio systems not an acoustician who probably has no idea about any of this equipment and other things which will remain unmentioned
3). Use acoustic treatment like salt and add it a little at a time primarily at first reflection points. I like Art Novion absorbers and diffusers as they are not overbearing and look nice. I have been in so many over damped rooms UGGGH.
4) address bass issues last and again be careful what and how much you use. Bass traps or corner absorbers do help but can be easily over done.
5). All of this varies by each room size and dimensions and it is effected by what type of speakers are in the room. They all do not work the same and they are all not the same if different rooms!
6) the room should be quiet but not dead. it should have energy and slam. I want to remove echo and keep as much energy as I can. I do this by listening since I have never found that a set of measurements or a single measurement ever worked correctly for me.
7). News Flash - this takes some time to get right , its not like Boom its done.
8) it might need some corrections to speaker placement a few times ( usually subtle).

9). If you are going to build a room I suggest you talk to people that actually do exactly what you are doing. I have gotten a lot of good advise and help in my past endeavors from Norm Varney who does exactly what I am talking about and has done it for a very long time.

I have given you 3 really good resources for a path to success and I personally believe that these should be able to improve almost everyone's listening experience. I am sure there are others that I am not familiar with but I am confident in Jim Smith, Stirling Trayle and Norm.
If it was me looking I would talk to all three and then make my selection.
 
For me, listening to a system that feels refreshed, revealing and musical after less than £1.5k PETs install, I'm drawing a few conclusions.
My room was over damped with 3 no. GIK absorbers on front wall and 2 no. at R and L side wall reflection points. But too stark without them.
The PETs which major on diffusion w moderate absorption have absolutely improved the balance of sound.
However greater absorption was needed in the front corners and front central communicating hatch...here GIK traps weren't enough.
So less absorption/more diffusion on walls, more absorption in corners.
My confident verdict is that I've achieved a win/win situation w none of the negatives of over damping.
Bass is effectively heavier but more agile, allowing me to tune my subs down a tad while losing no impact, only gaining.
The other big winner is imaging. I'm getting a way more holistic soundfield, instruments better delineated, but no "greying" or "whitening" in tone or timbre.
I kinda got lucky here...very lucky.
My fairy godmother (member here PJWD) did all the planning...I just flashed the credit card and put the panels up as he suggested and where he suggested.
And hit a home run first time of asking.
 
Hi Duke, when I say "sounds more real" I mean that it is closing the gap between what is heard live and what is heard reproduced.
I think that is a generally acceptable definition but it does not adequately account for differences in what people are listening for.
 
You can think of the in-room reflections as the CARRIERS for the venue cues on the recording, in particular the reverberation tails, as these should be presented from all around rather than from only two discrete locations (the left and right loudspeakers, as would be the case in an overdamped room). So the in-room reflections do good things as well as bad things! But not all in-room reflections are equally beneficial, nor equally detrimental.

The KEY lies in the ARRIVAL TIME of the reflections (assuming they are spectrally correct, or nearly so, to begin with).

The earliest reflections are the ones which most strongly present the playback room's undesirable "small room signature" cues, and are also the ones which degrade clarity the most.

The later reflections are the ones which most effectively present the reverberation tails on the recording, which convey the recording venue's acoustic space (whether said "acoustic space" be real or engineered or both). As long as they aren't TOO loud clarity is preserved.

So imo it's not a matter of reflections being good or bad - it's a matter of minimizing the bad ones while encouraging and cultivating the good ones. Imo the loudspeaker design itself can play a significant role here... you ever try horns???

;^)
Duke,
What are your thoughts on "splash" speakers these days? As I recall some of your earlier speakers used midrange drivers behind the main speakers and pointed up to arrive >10mS from the primary speaker sound. Not too dissimilar from bipolar or panel speakers as I recall.

Evan
 
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Duke,
What are your thoughts on "splash" speakers these days? As I recall some of your earlier speakers used midrange drivers behind the main speakers and pointed up to arrive >10mS from the primary speaker sound. Not too dissimilar from bipolar or panel speakers as I recall.

Evan
Still doing it! We're calling it the "Space Generator" these days, as we're claiming that it increases the perception of the acoustic space on the recording.

The up-and-back firing driver (which contributes relatively late-onset reverberant energy) is the brainchild of Jim Romeyn, and is basically an evolution of the controlled bipolar radiation patterns I was doing for a while. It does several things better than my bipolars did.

Here's the backside of one of our current models; around front is another horn and a large prosound-style midwoofer:

13-602x1024.jpg
 
Pick the proper carpet and add a thick felt underlay - an inadequate absorber can be worst than no absorption at all. . . .

A thick felt underlay will be very absorptive. I did not think this can be prescribed automatically for all listening rooms.
 
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A thick felt underlay will be very absorptive. I did not think this can be prescribed automatically for all listening rooms.


Surely it depends on our priorities on depth and layering. Our perception of distance is created by the primary reflections of the natural event in the real floor and ceiling and timbre variations. If you spoil them with the primary reflections of your own room you pervert this information.

IMHO we should either keep the floor zone between listener and speakers either reflective ( bare for those who like the effect) or covered a with good absorber. Most carpets are an acoustic nightmare, with a ragged and incomplete absorption spectrum.
 
A thick felt underlay will be very absorptive. I did not think this can be prescribed automatically for all listening rooms.
The effective frequency bandwidth of a fibrous absorber is primarily a function of the depth of the absorber and to a lesser degree, the angle of incidence of the incoming sound source. A half inch thick carpet made from ideal materials (open weave jute backing, no plastic, wool fibers) will only act upon only the uppermost audible frequencies and thus not be very useful. You will have created a narrowband tone control which absorbs only the frequencies above 10kHz which impart a sense of airiness to a recording. We want to at least absorb down into the 5kHz range to kill the potential for a hashy, harsh slap echo between floor and ceiling. So I'll place a double thickness of 1/2" felt underpad beneath my wool rug to create an overall depth of 1.5" and broaden the absorption bandwidth usefully.

Here is the thing as I see it. Unless you are using a loudspeaker like a line array or horn based loudspeaker which is highly directional at mid and high frequencies, the primary floor reflection is a problem for all of us. You may be blessed with a room with high ceilings and the space to pull the loudspeakers out far away from the walls, far enough that primary wall and ceiling reflections are outside of the problematic 6ms range. But if you use any conventional wide dispersion loudspeaker design, the floor reflection will inevitably arrive in less than 6ms and therefore be a problem. If you use a multi-way loudspeaker the problem will be exacerbated. Your speaker's smooth frequency and phase behavior doesn't stand up outside of a pretty narrow +/- 15 degree vertical window due to lobing effects in the crossover between drivers. So that early floor reflection will have a jagged frequency response which will then recombine with the direct sound in an even more problematic fashion.

If it weren't so impractical to implement, I would place a pair of 3-4' square and 6" deep broadband absorbers at the primary floor reflections. I know a few other keen members here besides me have experimented with this. I suppose in a perfect world an all-out, ground-up, custom built room could incorporate large steel gratings in the floor beneath the carpet. These gratings would be centered in the anticipated vicinity of the primary floor reflections. Then you could place the deep broadband absorbers below floor level. You would have the performance benefit without the physical or aesthetic obstruction of a surface mounted absorber.
 
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