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An Enticing Marketing Story, Theory Without Measurement?
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DDF
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I was pointing out that there are better choices than 8" thick absorbers if broadband absorption is needed. Why do you think perforated absorbers would be a poorer choice?
I didn't say it was a poorer choice. I said:
"All depends on the goal, but I wouldn't make sense using a perforated covering for a broadband absorber for the mitigation of early arriving reflections."
The reason is that a perforated absorber doesn't attenuate early arriving reflections as well as a traditional absorber.
DDF
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This hasn't been my experience when spec'ing, procuring, installing and measuring the effect of pegboard absorbers in rooms I've designed/built (not for personal use, but professionally).
Exactly what measurements are you looking at?
It's quite evident that a hard board (even with holes) will not attenuate as evenly as an absorber. Some of the frequencies will be scattered and reflected also, meaning the frequencies will not my mitigated as much as with absorption. A potential issue with pegboard, is that the narrow tuned frequency that the hole spacing supports is too high into the mid range.
A binary sequence like BAD panels provide diffusion and works better than a pegboard, but they still don't attenuate as well as an absorber.
??? That is like me asking for a meaning of a word and you tell me to go and read the dictionary.
Good thing though as I was going to quote their measurements anyway.
Here are the measurements for their popular modffusor:
First thing we notice is that acoustic measurements are stopping at just 3.1 kHz.
Second, that the acoustic product has frequency dependent alpha (coefficient of absorption or diffusion). In other words, they are a form of an EQ. In other words, the reflections are subjected to an EQ.
Third, even diffusers act like absorbers as the red line shows.
In other words, don't just slap these things on the wall because you think this is what "pros" do so you should too.
As a side note, you should know that both Dr. Toole and I know Dr. D'Antonio (founder of RPG and an acoustic research). Here is an example of importance in this context in Dr. Toole's book:
And compromised they are when listeners stick them right next to their ears.
Which means nothing in the context of strong room modes well below this frequency. And this is a whopping 8 inch thickness that most people will not use, nor tolerate in their listening rooms.
Here is my room which I measured during the Lyngdorf Room Perfect review: https://www.audiosciencereview.com/...measurements-of-lyngdorf-roomperfect-eq.6799/
The variations at 200 Hz and above are very little compared to what comes before it. Notice how EQ has knocked down the variations below 200 Hz, as confirmed in listening tests.
This is the room. I can't imagine sticking an 8 inch absorber on the walls:
The message here is simple:
1. Get a great speaker that has similar off-axis response to on-axis and has smooth frequency response.
2. Use EQ to much reduce the impact of the room at low frequencies.
3. Use some furnishing to knock down too high of a reverberation time (my carpet there and furnishing you don't see).
Absolutely superb sound can be had without turning the room into a working studio.
There are RPG diffusers that diffuse till 20KHz as well.??? That is like me asking for a meaning of a word and you tell me to go and read the dictionary.
Good thing though as I was going to quote their measurements anyway.
Here are the measurements for their popular modffusor:
View attachment 25470
First thing we notice is that acoustic measurements are stopping at just 3.1 kHz.
Second, that the acoustic product has frequency dependent alpha (coefficient of absorption or diffusion). In other words, they are a form of an EQ. In other words, the reflections are subjected to an EQ.
Third, even diffusers act like absorbers as the red line shows.
In other words, don't just slap these things on the wall because you think this is what "pros" do so you should too.
As a side note, you should know that both Dr. Toole and I know Dr. D'Antonio (founder of RPG and an acoustic research). Here is an example of importance in this context in Dr. Toole's book:
View attachment 25471
And compromised they are when listeners stick them right next to their ears.
Of course a diffuser absorbs as well. That's well known and how much it's also dependend on type and the number being used. Generally though one would recommend them for late arrival reflections. While you can use them for earlier reflections as well if you have the 3 x wavelength distance, that would not be as accurate as using an absorber or redirection.
You need to keep in mind is that complex impedance of boundary and furnitures changes the spectral content to a great degree. In that regard and combined with the destructive comb filter effect and image shift created by reflections arriving later than the direct signal, a well designed diffuser is a lot more neutral than no treatment and far more than spaced sources in multi channels.
But it's the better choice for late arrival reflections if accuracy is the desire. Part of the goal in many designs is to enhance spaciousness without creating the chaotic response of multi channel and create a space that is more similar to a concert hall where you have late arrival lateral energy. Diffusion correctly placed is the only way to achieve that without creating a mess. Is it 100% correct? No. But the result with no treatment and high gain reflections creates far more "distortion". These diffusers can be offered as deeper units with diffusion lower in frequency by the way.
You completely overlooked the context a 8" absorber was mentioned. It was in order to treat specular energy. Room modes is another area and I have never said a 8" absorber a good choice for that. You need to follow the train of thought in the discussion.Which means nothing in the context of strong room modes well below this frequency. And this is a whopping 8 inch thickness that most people will not use, nor tolerate in their listening rooms.
Here is my room which I measured during the Lyngdorf Room Perfect review: https://www.audiosciencereview.com/...measurements-of-lyngdorf-roomperfect-eq.6799/
The variations at 200 Hz and above are very little compared to what comes before it. Notice how EQ has knocked down the variations below 200 Hz, as confirmed in listening tests.
This is the room. I can't imagine sticking an 8 inch absorber on the walls:
The message here is simple:
1. Get a great speaker that has similar off-axis response to on-axis and has smooth frequency response.
2. Use EQ to much reduce the impact of the room at low frequencies.
3. Use some furnishing to knock down too high of a reverberation time (my carpet there and furnishing you don't see).
Absolutely superb sound can be had without turning the room into a working studio.
EQ doesn't work well other than where you the response is minimum phase. A simple frequency response doesn't not show that. If something works great it will also effect the time domain.
I can't debate against your priorities but IMO that would lead in most room to a mediocre result at best. That's not what I'm after.
I mean why in the world would we chase after electronics with ultra low distortion and at the same time live with huge "distortion" from our room? That makes no sense as the room contributes far more, something almost anyone knows who have some experience with acoustics. A lot of times differences between electronics will be drowned or masked in rooms with poor acoustics. It's actually when you have a well treated room those smaller differences become audible.
Sorry no. Leaving the side walls with bare makes no spectral change. You are arguing for acoustic products there which do change the response of an excellent speaker.
Comb filtering is not remotely an audible effect. See Dr. Toole's book or my article: https://www.audiosciencereview.com/...ds/perceptual-effects-of-room-reflections.13/
There is both psychoacoustic theory there and controlled listening test such as:
Comb filtering is more of a problem for our eyes than ears.
Really, what you state is the old understanding of acoustics. Much has changed in our understanding today. You reference RPG products. Here is what Dr. D'Antonio has to say about history of room acoustics:
This is more or less what you are still advocating.
Start of real research, controlled testing and inclusion of psychoacoustics.
And then we had key findings:
And:
His final slide is actually a graph based on research paper by Dr. Toole and Olive:
At typical levels of reflections we get "spaciousness and richness of timbre." It is not at all a bad thing.
So please don't keep repeating this stuff with "image shift" and such. What one imagines with sound travelling is not the same as what happens with the sound arrives individually and differently in each ear with the brain interpreting it. Ask someone if they like to sing in a shower or outside. The answer will be the former.
Chaotic response of multi-channel? Did you really say that? You can make an airplane fly from behind me to the front using stereo and your acoustic products?
The level of delay required for envelopment is too small in a typical of small room. With multi-channel though, it is trivial to create that using rear/side channels.
As to a concert hall, that is all diffused. There is no pin-point imaging. It is the same in any band you listen to. Walk up to a piano and stand next to it. What imaging are you hearing?
I can take a $500 surround system and beat any price stereo system in controlled test. It won't even be close. How the heck is the goal post lost this much?
To me that room looks very echoey - I can imagine how it would sound. The carpet is 'vestigial'.
Two audiophiles could seemingly have a conversation about room acoustics while in reality talking about completely different things. The person with the fully-carpeted living room would be mystified by the other's obsession with acoustics and measurement, being unaware that the other person listens to music in a bare, wood-floored echo chamber.
There's isn't much point in continuing this. You're overlooking and throwing away a lot of acoustic researchers and well know psychoacoustics and holding on to only one that primarily talks about preferences. I'm talking about accuracy and as mentioned before when it comes to preferences a lot aspect are in play and it becomes difficult. With accuracy it's a lot easier.Sorry no. Leaving the side walls with bare makes no spectral change. You are arguing for acoustic products there which do change the response of an excellent speaker.
Comb filtering is not remotely an audible effect. See Dr. Toole's book or my article: https://www.audiosciencereview.com/...ds/perceptual-effects-of-room-reflections.13/
There is both psychoacoustic theory there and controlled listening test such as:
View attachment 25497
Comb filtering is more of a problem for our eyes than ears.
Really, what you state is the old understanding of acoustics. Much has changed in our understanding today. You reference RPG products. Here is what Dr. D'Antonio has to say about history of room acoustics:
This is more or less what you are still advocating.
Start of real research, controlled testing and inclusion of psychoacoustics.
And then we had key findings:
And:
His final slide is actually a graph based on research paper by Dr. Toole and Olive:
At typical levels of reflections we get "spaciousness and richness of timbre." It is not at all a bad thing.
So please don't keep repeating this stuff with "image shift" and such. What one imagines with sound travelling is not the same as what happens with the sound arrives individually and differently in each ear with the brain interpreting it. Ask someone if they like to sing in a shower or outside. The answer will be the former.
I personally have never preferred side wall reflections with speakers that measures great off-axis and so does very few I know treat them broadband. Should we throw that experience away because one of Tooles studies slightly indicates a preference for side wall contribution with a certain type of music (classical)? Besides I listen in another type of treated room that Toole experimented with. You're drawing conclusions on a very thin premises and it's not related to accuracy.
If what you said was true, that would imply that there wouldn't be any need whatsever to treat control rooms or mastering rooms as long as used speakers with good power response, multiple subwoofers and EQ. Well, I don't think that would be a good choice.
Multi channel here was mentioned primarily for music and yes it will be very chaotic. That's due to the superimposed signal from spaced sources and comb filtering and lobing.
A concert hall doesn't have early arriving reflections but late arrival diffuse energy. That's very different and exactly what some acoustic principles are trying to emulate, and as already mentioned and proves you are partially wrong in you statement that "level of delay required for envelopment is too small ", the time domain behaviour of such a small room is quite identical to a large quality concert hall. That's crucial here.
When it comes to imaging, that depends on the recorded signal and mix. For accuracy the goal is to recreate the mix, whether that's pin-pointing or a more spacious presentation. Either way, you can also treat a room that gives the big and extreme envelopment for all types of music but it won't be accurate. It's sort of like adding second order harmonics from an amplifier. It may be pleasing but it's not accuracy. Which is fine though if that's the goal and desire.
I'll leave at that. I know based on what you have written on acoustics and psychoacoustics that we are miles from each other. We simply have to agree to disagree.
Edit:
FIY I'm working on speaker designs that measures extremely well off-axis. And as oppose to most speakers, they do it both horizontally and vertically. So they outperform most speakers with so called great power response. I would love to say in the advertisement that with these speakers you simply don't need any treatment! And I could make a package of 4 subwoofers to sell with. Financially this would be a heck of better deal for my personally. Selling a lot of speakers/subs is far easier than selling acoustics products (which is very time consuming) and that mark up is much higher.
But I feel I would be lying. I know the room still contributes a great deal. How people treat it, can vary though depending on room size, aesthetic requirement and preference.
Just think about MBLs omni flagship speaker which measured flat a certain height and compare it to a speaker with uniform but narrower beamwidth. Do they sound the same? No. They sound extremely different due to difference in the reflected energy. Or you can change the beamwidth on a Beolab 90 from narrow to wide (120 to 180 degrees) and immediately hear the difference. This proves that the room contribution is still very important to what we hear despite of the power response.
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I didn't mean to be offensive! But I do think it interesting that the fashion for bare wood floors (and surely it is a fashion and not something that an audiophile would deliberately specify for acoustic reasons..?) is a contrast with how people's rooms might have been in the past. In my mind's eye, the carpeted living room says "rich sound" while the bare wood floor and walls says "hollow sound". My own room is carpeted (over cement screed) and has heavy curtains behind the speakers (at night, anyway).haha @Cosmik you are so bad, man!
There is no 'echo.' The room is live. As I noted elsewhere, without anything in there it sounded fantastic with orchestral/classical music but was way too live for pop/rock. So I added the stand for the gear, on purpose selected that very thick and large carpet and seating, etc. you don't see. That got the reverberation time down enough that it sounds wonderful now. Certainly better than anything I deserve!
I am not a fan of either speaker. That aside, I don't know what point you are making. Of course changing the DSP settings in the Beolab makes a difference. And that diffused MBL sound which I have heard many times bugs me as it homogenizes all music to sound that way.
What? You have not references one research paper or controlled testing to back anything you have posted. So please don't keep saying pscychoustics this and that. You need to provide actual back up.
And let me get this straight: you are saying if I blind test two rooms and one is preferred over the other, I am supposed to think it is less accurate and I should go with the one I like less? What logic is that?
Humans have an internal fidelity compass when it comes to sound reproduction. We know if bass is too high or it distorts without a reference. Likewise, we know what sound we like because it seems more real to us. Your assertion that I should go by what makes sense to one's intuition about sound and reflections has been debunked in countless research papers and studies. It is all documented in Dr. Toole's book in exhaustic level including some 270 references. This is not some idle forum post you can brush aside with that starting comment. It is your position that needs validation, not the other way around.
You talk about psychoacoustics. Well, there is no better textbook on that than Zwicker and Fastl. And this is what Zwicker had to say on topic of reflections in his peer reviewed paper showing the improvement of speech in the presence of reflections:
”Using the loudness exceeded in 10% of the time as an indication of the perceived loudness, it can be expected that the speech is 1.2 times louder in the room with 0.6-s reverberation time and about two times louder in the room with 2.5-s reverberation compared with the loudness produced in the free-field condition. This increment in loudness is often very helpful for the intelligibility of speech in rooms as long as the reverberation time does not produce temporal masking, which reduces the audibility of faint consonants appearing in sequence to loud vowels.”
Temporal masking is the reason we don't want the room to be too live if we care about speech intelligibility.
Here is the introduction section of the Journal of ASA paper, ”The influence of spectral characteristics of early reflections on speech intelligibility,” by Arweile and Buchholz, dated 2011, on the same point:
”Early reflections (ERs) of a sound in a given environment are characterized by arriving at the listener’s ears shortly (approximately within 50 ms) after the direct sound (DS). They are integrated with the DS in the auditory system, i.e., within a certain time window their energy is added to the energy of the DS. With regards to speech intelligibility the DS and the ERs form the useful part of the speech signal, whereas late reflections are considered detrimental for speech intelligibility. Thus, the effective level of a speech signal depends on the energy of the DS and the energy of the ERs at the listener’s ears. ER [early reflection] energy increases the effective speech level and has been demonstrated to improve speech intelligibility (Lochner and Burger, 1964; Na´beˇlek and Robinette, 1978; Soulodre et al., 1989; Parizet and Polack, 1992; Bradley et al., 2003).”
Isn't this accuracy? Hearing and understanding words?
Again, all of this research is included in Dr. Toole's book with a simpler style that is understandable by people outside of the industry/research. Please read and understand it all before jumping into this industry.
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