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Room Treatment to get Soundstage, Spaciousness & Imaging?
- Thread starter Cinema40
- Start date
It can also be a cancellation that occurs at the listening position.
My suggestion for OP is to try a listening position around 6.2 feet from the back wall, and the loudspeakers according to the listening position so they form an equilateral position. It's just a “rule of thumb”, but with a listening position 6.2 feet away from the back wall, he will sit at 38% of the room length, which sometimes works great.
What I strive for with my audio system is a fairly small listening triangle, as that gives me a high ratio of direct sound vs. room-reflected sounds. With a higher ratio of direct sound, you will hear more of the recorded acoustic space with less interference from the reflections that occur in the listening room. But, of course, the screen size in OP’s room will be a restriction for his setup, so the possible size of the listening triangle will have to be chosen with that in mind.
My suggestion for OP is to try a listening position around 6.2 feet from the back wall, and the loudspeakers according to the listening position so they form an equilateral position. It's just a “rule of thumb”, but with a listening position 6.2 feet away from the back wall, he will sit at 38% of the room length, which sometimes works great.
What I strive for with my audio system is a fairly small listening triangle, as that gives me a high ratio of direct sound vs. room-reflected sounds. With a higher ratio of direct sound, you will hear more of the recorded acoustic space with less interference from the reflections that occur in the listening room. But, of course, the screen size in OP’s room will be a restriction for his setup, so the possible size of the listening triangle will have to be chosen with that in mind.
I don't disagree, mine was just a possibility suggestion. A broad dip between 140Hz and 250Hz corresponds to quarter wavelength reflection distances between 35cm to 60cm. If this is the distance from speaker woofer to front wall/side wall/floor or a combination of all those, it's possible their individual nulls merge into one wide, continuous valley like that. Dirac refusing to boost the region can also be explained with non min phase SBIR nulls there.
- Thread Starter
- #67
You are both right. I am likely battling SBIR in that area and I may have an idea what may be happening based on these measurements (ignore above 1k as the mic wasn't positioned optimally) -
In both these measurements, the rockwool insulation on the side wall has been removed. Notice that the dip in the 160 to 200hz is reduced when the curtained is open. This is because in my room, opening the curtains means that a lot of heavy curtain is bunched up right next to the left speaker acting like an absorber. This should mean that I would fare better with a permanent absorber in that area right? Further, I can add another absorber besides the right speaker which should yield symmetry and better response in the upper bass/lower mid bass region for both speakers considering the distance to the side wall.
If you have some movable absorber panels or rockwool panels, you can easily test this theory?
- Thread Starter
- #69
Yes, It seems like a good weekend project to take up. I have been really avoiding moving the speakers all this time cause Dirac measurements are a pain to re do. 13 measurements every time the speaker in moved is not fun but I guess it's a small commitment for better sound!If you have some movable absorber panels or rockwool panels, you can easily test this theory?
Wesseling Audio Lab
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Was the mic and speaker in the identical position for both of these measurements
I would suggest getting the best possible result without Dirac at all first, so experiment with just pure direct / no room correction. Whichever setup works best, will likely also give the best result with Dirac.
So put differently; You don't have to keep re-running Dirac while experimenting.
- Thread Starter
- #72
Simply setting A<B<C in a geometric sequence and spaced smoothly I guess such that B/A = C/B otherwise reflections from the floor, side wall, and rear wall will all cancel out the same frequency.
Keith_W
Master Contributor
For frequencies that are omnidirectional, you will get 1/4 wavelength SBIR cancellation from every nearby surface. It is well known that you don't want two lengths to be equidistant or close to it, because the cancellations will be close in frequency - you will double the Q and double the depth of the cancellation.
Chris A
Addicted to Fun and Learning
I first read this thread early this morning. I've spent some time reading the responses and the advice given. But I fear that there has been so much advice given already that it is a lost cause to try to offer the OP suggestions to his dilemma. But note that I do still see a few things which aren't really being discussed:
There are several things that I think would be very helpful to the OP based on the above observations (plus a few others not mentioned).
Chris
- The OP is over focused on magnitude-only Bode response...but not also phase...and appears over focused on electronic correction means (Dirac. et al.). Physical treatments in-room are almost secondary thoughts before understanding and solving real acoustic issues.
- There are almost no discussions of "when reflections occur", outside of rather crude reverberation times (T20, T30, Topt, EDT). These RT curves don't really look very good (to be honest--they look overdamped and probably too deeply absorbed into the room--with no real difference between early reflections and later reflections).
- I didn't see impulse response or step response graphs of single loudspeakers, and the OP didn't post full .mdt REW measurement files (which I find are almost critical to help diagnose the issues)--only screen shots of two or three basic REW plots--basically repeated over and over with small variations. I see a lot of "L-R" measurements (i.e., both channels playing at the same time), which are never valid above the room's Schroeder frequency.
- The placement of the measurement microphone is not really discussed and its importance in capturing only minimum phase response from the loudspeakers--and not reflections combined with direct arrivals. (This is especially important when discussing subjective depth of imaging of a setup--to largely avoid mixing in room reflections into the measurements.) The listening positions look to be too close to the back wall.
- There is almost no discussion of the effects of loudspeaker directivity response and its effects on resultant breadth and depth stereo or multichannel imaging. This is a pretty serious omission, in my experience. I see little or no toe-in and immediate side-wall treatments to capture early reflections.
- There isn't any discussion on the effects of time alignment (in coordination with the preceding point on directivity control) on the subjective effects of large loudspeaker phase shifts on the perception of depth of imaging.
- (...this is a big one...) There is what appears to be very little discussion on simply looking at other setups that image in depth and breadth well, and any visually obvious characteristics of those setups that might contribute to at least partially solving his specific issues. I saw only one post that linked to these characteristics--largely ignored.
Helping the OP develop a useful mental model of what is a good setup looks like (and measures) and what has problems is at least as important as helping the OP solve his current issues. In fact, I believe it's more important to spend time on developing a useful mental model as to solve the immediate issue.
There are several things that I think would be very helpful to the OP based on the above observations (plus a few others not mentioned).
Chris
- Thread Starter
- #76
Hello Chris,
Thanks for your detailed response to my thread. If i may respond, I would like to add the following -
1. My current 5.4.2 was added in a room that was previously a Bose Lifestyle setup in a casual media room. Once I bought the gear, I knew that Dirac and other room correction options are the best bet for a room that's sub optimal in it's placement and treatment. Now that the room is being renovated, I am open to all expert advice on practical room treatment given the limitations of my room.
As to why I was overly fixated on Frequency response, I always considered that Dirac ART took care of impulse response and phase and the only thing I was supposed to look at was the overall frequency response measured since that was the adjusted and most discussed aspect. This is not right based on what I've read. What I understand from your comment, Phase etc need to be optimised in the room through room treatment, placement etc before Room correction is implemented right?
2. All measurements are L+R, I did not know that these are not valid above the schroeder frequency. I will take new measurements and share them tomorrow.
The mental model you speak about is exactly the guidance I am seeking. I have watched various videos from Poes Acoustics, Anthony Grimani, Audioholics etc. but haven't been able to reach an answer on what exactly should be done in my room considering the constraints. For example - One side wall has a large glass window in front of which there's a thick curtain which is supposed to act as an absorber. Now should the opposite wall have absorption based on that or not? This is one of many room treatment related questions I had for my room. Another example is Corner Absorption, as per what I've read you need a lot of depth to absorb bass frequencies in that region but then you have products like this that claim to address the 60hz to 500hz range which seems to be impossible considering the depth. So is corner absorption useless or should I still do something?
I get that people are looking to sell their products on the internet and promote them through whatever medium possible. Hence, I turn to forums for advice based on actual experiences. I will be trying the various options of toe in to see what yields the best sound and would kindly request you to please reiterate what post I may have ignored in your mention of "other setups that image in depth and breadth well, and any visually obvious characteristics of those setups that might contribute to at least partially solving his specific issues. I saw only one post that linked to these characteristics--largely ignored.". I may have mistakenly missed a very helpful post in my reading.
I don’t see this. The 1/4 wavelength SBIR cancellation heard by the listener occurs for the sound radiated directly towards the listener, not to the left or right (even if a cancellation occurs there as well). You will not get a «doubling» from the side wall. Also Q is a property of resonances, not of acoustic interference as SBIR.
Chris A
Addicted to Fun and Learning
Understand that I was generally speaking to the community of folks that have responded here to help expand the problem solving space. I was not focused on you specifically, but I was focused on your specific issue(s).
To help start you down that path on this subject of soundstage imaging:
- First think about how you hear the soundstage laterally, i.e., across the space between your left and right front loudspeakers--and possibly beyond each loudspeaker on each side. The microphones used by the recording engineer(s) capture not only the magnitude of the sound pressure level (SPL) vs. time at the single point in space that the microphone is located, but they are simultaneously capturing the phase of the SPL from each instrument/voice that is playing relative to each other.
- In order for you to hear a flat but wide stereo soundstage at playback time in your listening room (i.e., the "second room") of each instrument/voice spread out from the microphones, the second room's audio playback system (and room acoustics) play the complex two channels recorded to your ears, which has not only the combined SPL (i.e., the magnitude or SPL) of the recorded music channels, it must also do this at the right times--the phase of the recorded signals.
So this is the first requirement that includes phase fidelity in order to accurately reproduce the horizontal soundstage. If done well, the listener in the second room can literally point at the virtual instruments/voices horizontally, and to some degree, vertically (more complexity here as to why vertical soundstage is partially audible using only stereo).
- So to get a strong lateral soundstage image, particular attention must be paid to symmetry of things like acoustic driver responses (i.e., they have the same left-right channel magnitude AND phase response), room acoustic symmetry (left to right, floor to ceiling) in the form of reflections and refractions/resonances, amplifier and left-right transmission line (cable) voltage magnitude and phase, and electronic processing delays (within a microsecond or so, that is). In other words: phase, phase, phase, and magnitude, magnitude, magnitude...across the audible spectrum, for each channel. (This also is true for multichannel setups, like 5.1, etc.). It turns out that the left-right phase response symmetry of the loudspeakers and the electronics system across the frequencies has to be consistent, but not necessarily "flat" vs. frequency.
For depth of soundstage, something extra has to be present. And that is phase fidelity of the loudspeakers and (predominantly) reinforcing the direct arrivals from the loudspeakers and suppressing nearfield reflections that dilute the phase information that the human hearing system uses to perceive audio depth. The greater the magnitude and phase errors from the electronics...and especially, the in-room interfering acoustic reflections, the more dilution of the direct arrivals, and the lessened perception of depth of soundstage imaging there is.
So you have to pay particular attention to reducing "phase response tilt" of your loudspeakers (high frequencies to low frequencies) and in controlling nearfield reflections from just around (within 3-6 feet) of the loudspeakers themselves that interfere with the flat phase characteristics of the loudspeakers and driving electronics.
This is a subject that even AIs seem to have gotten wrong (in the past), I've found.
There's more, but for now, just exercising your mind's eye to these effects in order to use them spontaneously--that's important in order to understand what is occurring in-room and how to deal with issues that arise.
Chris
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It’s actually pretty easy when you think about it.
To hear more of the depth in a recording, the only information that can bring you more of that is the direct sound from loudspeakers, as that is the only thing that contains the information about the acoustic depth of the recorded space. You simply need a high ratio of direct sound compared to the reflective sounds coming from your own listening environment, as those reflections can only "blur" the recorded information, especially the finer details like the acoustics of the recorded space.
To hear more of the depth in a recording, the only information that can bring you more of that is the direct sound from loudspeakers, as that is the only thing that contains the information about the acoustic depth of the recorded space. You simply need a high ratio of direct sound compared to the reflective sounds coming from your own listening environment, as those reflections can only "blur" the recorded information, especially the finer details like the acoustics of the recorded space.
