The argument for/against room treatment
- Thread starter MadFloyd
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Hello pjwd. The speakers are on the slightly longer wall. Each tweeter is 51.25" in from the side wall. They are aimed straight ahead. The tweeters are 9'-3" from each ear at the listening seat which is centered about 14" from the rear wall.
Sbnx
I am not sure that is the case .. speakers well away from side walls can image well and give a large soundstage
I believe the soundstage is baked into the recording and speakers with good off axis behaviour reproduce it
I should add that ideally the delayed reverberant field is correlated with the directsound and provudes a nice even decay
Peter
This is amray trace a free online program - it allows you to click on a path and shows you the time delay with direct sound - that's the bar down the bottom - it shows your first side wall reflection about 4.7 ms delay - which is short but not too shabby - the ones before and after are from rear wall close to your seat and after that you are out to the 8ms zone or so
a high back seat and a couple of pieces of sculpture either side
would block it all and your fireplace probably deals to an extent with those wall behind speaker reflections.I also sit quite close to the rear wall - it is actually a pair of sliding doors and I expected a massive difference between open and closed but in reality it is only slight - perhaps because of my chair - its an Eames aluminium group lounge with the high back
Of course it may be just my head and ears blocking it
my room is similar front to back as yours but 23' wide - I recently relocated the speakers to long wall and it was a great improvement - I am now building the acoustic equivalent to your fire place between the speakers
its all very interesting to see what folks are getting good results with
Cheers
Phil
Bruce B
WBF Founding Member, Pro Audio Production Member
This is why I chose some of the best off-axis performing speakers available.
Lemme guess. Ummmm, pure evil?
Indeed the cacophony of waves would be most detrimentalLemme guess. Ummmm, pure evil?
but possibly for the fact of the two white dots that being rather strategically placed seem to leave a void in relation to those Waves in relation to the listening chairThe darkened area at that spot shows not the same color intensity as the waves crisscrossing fore and aft of said occupier.
Looks as if they may be leaving the listener with just the direct sounds and infinite reflections.
Interesting
BruceD
The idea that you don't need any side wall treatment is related to studies where having speakers that measures very well off-axis combined with sufficient distance to side walls, increases spaciosness and can be beneficial compared to treatment and absorption. But these studies are quite inadequate in several ways.
First of all they are not very conclusive, especially when it comes different music genres. It's mainly classical where late side wall reflections have been found to be preferred.
Secondly they don't take into the account how the rest of the room is treated. For example: Spaciosness can also be added with late arrival diffuse energy. These rearechers haven't explored different kinds of acoustic principles at all. And obviously in most homes there isn't a pefect reflective wall on both sides but there will often be furnitures, pictures, windows, etc. that creates a much different and complex impedance surface.
Thirdly, these studies don't really say anything about people prefer over time. Personally I've found that what I prefer in a short listening test, may not be the same as over time with different music material. Sometimes it can be impressive to have reflective side walls, but it get's fatiguing over time.
When it comes to bass trapping, there's basically no reason why that shouldn't always be better as long as they don't overdampen mids and highs.
Take note that reverberat time does not exist in small rooms. We need to apply other methods in these types of rooms. FIY: I work in the area of acoustics and small room acoustics is my expertise.
First of all they are not very conclusive, especially when it comes different music genres. It's mainly classical where late side wall reflections have been found to be preferred.
Secondly they don't take into the account how the rest of the room is treated. For example: Spaciosness can also be added with late arrival diffuse energy. These rearechers haven't explored different kinds of acoustic principles at all. And obviously in most homes there isn't a pefect reflective wall on both sides but there will often be furnitures, pictures, windows, etc. that creates a much different and complex impedance surface.
Thirdly, these studies don't really say anything about people prefer over time. Personally I've found that what I prefer in a short listening test, may not be the same as over time with different music material. Sometimes it can be impressive to have reflective side walls, but it get's fatiguing over time.
When it comes to bass trapping, there's basically no reason why that shouldn't always be better as long as they don't overdampen mids and highs.
Take note that reverberat time does not exist in small rooms. We need to apply other methods in these types of rooms. FIY: I work in the area of acoustics and small room acoustics is my expertise.
I would like to share an acoustic experiment I performed. I had may speakers and listening position such that the reflection from the side wall was about 7ms later than the direct sound. I played John Campbell's version of "Down in the hole". This is a pretty open and spacious sounding recording. I then placed a 2'X4' sheet of 2" thick OC703 at each of the sidewall reflections. I asked my spouse to listen and comment. I asked her what she thought when I put the panels in place. She said "Its like the sound just got all concentrated in the middle between the speakers". Her way of saying that the soundstage collapsed.
All I can say is that acoustic treatment is not all that expensive. Get a couple panels or make your own and experiment. If you like what it does then that is great. If not you are only out a couple hundred dollars. (Much less than the depreciation hit you just took when you sold that pair of cables for a different pair)
As a note: my room is dedicated, highly symmetric and well treated. My speakers have very good off axis response.
All I can say is that acoustic treatment is not all that expensive. Get a couple panels or make your own and experiment. If you like what it does then that is great. If not you are only out a couple hundred dollars. (Much less than the depreciation hit you just took when you sold that pair of cables for a different pair)
As a note: my room is dedicated, highly symmetric and well treated. My speakers have very good off axis response.
I agree. IMO the preference testing for this, as well as just in general, has a lot of issues and I believe they have reached some questionable conclusions as a result. I don't think it's worthless, but as you said, there are issues.
Stehno, I'm intrigued by your ability to play your system at an average of high 90's to low 100 dbs (if I have that right?). There is no way I could do that in my system from a 10' listening position -- maybe for awhile further back in the room (35') where I often listen while working, but I think it would over pressurize my room not to mention my second favorite organ -- my ears.
The last amplified concert I went to last year in a mid-sized club, was in the the 95-105 db range and while the sound quality was pretty good, it just felt like a damaging assault on my ears after awhile (and this was with ear protection).
So if you've managed to listen to reproduced music in a small room at those constant levels without doing serious damage to your hearing, and it sounds good, you've pulled off a miracle.
Yes. It's best to experience this rather than simply concluding based on some researchers. After all, there are many variables that come into play here.
I highly recommend using broadband treatment. A 2" thick absorber will only absorb really well down to approximately 600-700 Hz area.
Ideally you want to treat specular reflections evenly down to the Schroeder frequency.
100% agree. The panels I use are 6" thick. Corner traps are 2 ft X 2 ft.
What gas flow resistance did you use for the OC703? 20,000?
Here is an interesting fact I don't think most people are aware of. Up to about a 4" (100mm) the rigid fiberglass (such as OC703) is good. But once that panel gets beyond 4" then the fluffy insulation is actually better. Here is an example comparing rigid vs fluffy that is 6" thick.
But then again, most people think a 4" panel is thick.
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I have been fascinated with crosstalk elimination but never have found a way to practically implement it into a permanent listening situation. Using extra drivers or digital processing has always colored the sound too much for me, and using a divider panel is just plain impractical. I'm interested in the idea of a sophisticated stereo upmixer that can mix two channel into a 3 or more across the front configuration without degrading the quality. That would allow wide speaker positioning without holes in the soundstage. So far the only good results I've heard have been from stuff mixed originally to more channels, but if our ears can do it it seems good enough software should be able to determine the panning of sounds in a 2 channel mix and send it cleanly to the appropriately placed speaker.I heard these Polks at RMAF 2019... it seems to me the main advantage is the spacing between speakers is much less critical. In some circumstances this is a major advantage! The system's soundstaging and imaging was impressive but it's a narrow sweet spot. The Polks performance overall was better than expected but the tweeters are not that great, imo. Overall it was a cool demo but didn't have me looking into crosstalk elimination afterwards.
Unrelated to crosstalk, but if the recording has enough spatial cues and they make it through the speakers, the need for anything else seems to be reduced accordingly. If the spatial cues are from the recording instead of reflections, they can more convincingly portray the recording space. Personally, I like a greater proportion of direct sound but also the system needs to be capable of pretty high resolution to achieve a 3-D, immersive soundstage. I've also found that wider spacing between speakers helps.
All that being said, I'm pretty happy with the standard 2 channel setup and appropriate room treatments to tighten the bass and adjust early reflections to suite preferences. My own simple experiments with creating multi channel mixes and then downmixing them to stereo got me thinking that adding extra channels was a lot of work for a subtle
Good headphones don't sound dead to me like an overdamped room but the external imaging is non existent. The soundwaves need to travel across the head and ear and adjust accordingly to small head movements to be convincing. Now that I've learned to EQ a couple of my headphones reasonably well I do find headphone listening to be quite pleasurable but it's a separate kind of experience. I agree that the degree of ambient information embedded in the recording has an effect on how much room reflections are desirable. I've found playing with horns of various dispersion that close mic vocals can sound great with a really wide dispersion horn, but complex symphonic work recorded in ambient spaces sounds best to me with extremely narrow dispersion horns. The narrow horns were also able to create a full 180 sound stage at times. I've settled with an intermediate dispersion with good off axis response. Amazingly I haven't changed anything in months now!
The sound enters each ear separately and nothing acoustical travels across the head. Also, are you using head tracking to compensate for head movement? If so, how are you doing that?
Yes, understood. We don't need anything acoustical to travel across the head to get spaciousness - just decorrelation between left and right ears, which headphones can easily produce. I should add that this can't be just any decorrelation but a decorrelated signal that is similar enough to be recognized as the same sound. Two different people speaking in each earpiece won't produce spaciousness. But because we don't have sound traveling across the head the HRTF doesn't work, so head tracking and appropriate custom equalization is typically needed to get a convincing external imaging effect. I don't get external imaging with my headphones but I do get excellent tonality with some basic EQ, and it doesn't sound to me like I'm listening to speakers in an overdamped room, even though it's a near perfect anechoic listening experience. It sounds open and lively, and I'm assuming that's because of the lack of crosstalk allowing adequate left to right decorrelation. I know some people prefer to add crosstalk to their headphone listening. I've tried that and I don't like it. To me it flattens and dulls the sound and does remind me of an overdamped room. Listening in mono is not great on headphones either but my expectations are usually pretty low with mono.
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