[PhilNYC]

This new Audio Circle software doesn't pop up a box when I have new messages and so I never notice.  It's also much harder to see what is new and what I've already read. 

FYI - you can turn on email notifications by going to Profile->Personal Message Options....

[8thnerve]

As for not being able to hear early reflections, that's not exactly true either.  You certainly can hear VERY early reflections - things such as early bounce off a console, early bounce off a TV between 2 speakers, early reflections from speakers placed close to a wall.  Those things that are within say 5ms of the original signal.  You can also hear late reflections - that which we call echo.  It's the ones in between that are up for debate.  There is some research to suggest that those are in fact beneficial - for speech intelligibility - not necessarily for music.

I should clarify.  I'm not saying that you can't hear reflections.  I'm saying that you can't hear the reflections that are commonly defined as first reflections from side walls, ceiling, etc.  The reflections that you do hear are from corners because their sound level is amplified.  If you do some acoustic measurements and then take accurate laser measurements of the distances from the tweeters to the first reflection point to the microphone and run the equations based on the speed of sound, you'll find that the actual reflections you see from the acoustic measurements don't match up with the distance calculations.  In most small rooms, mine included, the first audible reflection comes from the front vertical corner at the ceiling.  That distance calculation does match the acoustic measurements.

Best Regards,

Nathan Loyer
Eighth Nerve

[8thnerve]

Meanwhile, the wave that bounced into the corner underwent a severe comb filter by collapsing into the 90 degree angle, and now returns and is amplified by the horn shape of the corner.  This wave is of much higher amplitude than the unabsorbed wave at the first reflection point would be and is also much more distorted.  Since the human ear can distinguish signals only so far below the sound of highest amplitude, this first reflection is for all intents and purposes, inaudible.

Nathan...based on this, could you conclude that if you treat the corner (a al a product like an Adapt Rectangle/Triangle) and reduce the amplitude of the corner amplification/distortion, then proportionally, a reflection at the first reflection point then becomes more audible?  From your comment, perhaps now the highest amplitude sound gets reduced by the corner treatment, and the first reflection suddenly becomes proportionally significant?

Yes, but I still believe that the sacrifice of high frequency energy is not worth it.  Also, I don't think we have a good conceptual structure of what sound is and these non-distorted reflections are not perceived as reflections by the human brain.  And before anyone says it's been proven that we hear these reflections, show me a case where the study did not involve a room with corners.

-Nathan

[8thnerve]

It's not quite that simple. There is a midrange frequency band where, for a given panel thickness, 100 percent of the sound is absorbed. As you go higher in frequency the surface becomes more reflective, especially for sound arriving at an angle. At some point the waves tend to bounce off the fiberglass, like a rock skipping over water on a lake. And at lower frequencies the material absorbs less as you describe. But it's not a continuous curve.

(Emphasis mine)  Exactly.  No matter how well it is designed, it will affect the frequency response in a non-linear manner.

That doesn't explain anything. According to what you just said above you use 705 rigid fiberglass. So how is that not absorption?

Because of the design.  The fiberglass is only exposed into the corner.  The front and sides are reflective.  The only energy that is affected by the fiberglass is the return energy from the corner.  None of this corner energy ever returns to the room as it is cycled back into the corner repeatedly.  No energy in the room has passed through an absorptive acoustic material.

Also, in the graph you posted, missing is how many of each type of product was used, and also how large the room is. Got some stats?

Yes, sorry for the oversight.  On the web page that this is located on: http://eighthnerve.com/methodology.html that information is in HTML so it didn't copy with that graph.

"These results were achieved with 4 Adapt Triangles and 6 Adapt Rectangles in a 15' x 13' x 8' room with sparse furnishings."

Actually, I partly agree with that. I believe what we hear most is the skewed frequency response caused by comb filtering. The reason early reflections affect "imaging" is because the response is skewed differently at each ear. So it's probably not due to phase shift and "time smear" (whatever that is) as so many people claim, but simple frequency response differences.

I partly agree with that as well.   I believe that the comb filtering that is relevant is primarily cased by the corners, but that there is a phase component as well.

Technically speaking, adding absorption into a room reduces the extra energy that lingers if it were not absorbed. The flattest response is in an anechoic chamber. Everything else is skewed compared to that.

I firmly believe that we'll be able to make a ruler flat room with no absorption very soon.  The only difference between the anechoic chamber and that would be that the chamber would be much lower in volume.

-Nathan

[8thnerve]

This new Audio Circle software doesn't pop up a box when I have new messages and so I never notice.  It's also much harder to see what is new and what I've already read. 

FYI - you can turn on email notifications by going to Profile->Personal Message Options....

Thanks Phil!

[bpape]

I think it's a matter of symantics.  If the treatments are minimizing amplification in the corner and are matching reduced reflections, they ARE absorbing one way or another.  The energy doesn't just disappear and doesn't get diffused into other axes.  It has to go somewhere and conversion to heat is the only place it can go.  It's just not the standard 'all the way to 20k' absorbtion. 

However, I contend that this is no different than straddling OC 703 or 705 across a corner with an FSK face on it.  Due to the larger size, the 2' wide 705 FSK panel will provide a more linear absorbtion curve than a 6" wide, 4" thick pc of the same material.  Is it perfectly linear?  No - not designed to be but it is in fact absorbing more at the bottom and mid than in the highs - which is where this discussion got started.

Also, if you ever do an impulse response measurement of a room, you can see exactly where the reflections are in time and hitting the refleciton points at those time points for first reflections absolutely does minimize those impulse 'blips.'  While you may not hear them specifically as an echo, you can absolutely hear/see the change in image specifity.  One of the biggest problems with people finding the appropriate reflections is that they only consider the full path.  What really shows where they are is the difference between the reflected path and the direct path.

Bryan

[mfsoa]

Perhaps 8th nerve is using a special kind of unidirectional fiberglass - Since it is reflective on one side, that must mean that it allows sound to pass through going toward the wall, yet magically knows to absorb it on the way out!?    And I guess since it is offset from the wall slightly, it also knows to let the sound in, but traps it effectively on the way out!?

I wonder, out of the total amount of sound energy absorbed by the 8th nerve corner treatment ("None of this corner energy ever returns to the room as it is cycled back into the corner repeatedly")(Wait - the reflective material is also unidirectional - Bonus!), what percent was absorbed on the way in, and what percent on the way out? My uneducated guess is that most of it happens goin' in, and the amount that comes out is proportional to the loss obtained going in in the first place. In other words, is the magic really the absorption of the return energy from the corner, or in keeping it out of the corner to begin with?

I don't mean to be too harsh on 8th nerve, I'm sure the products are superb and are a good value, it's just that the explainations seem a bit pixie-dustish and that we are dealing with something a bit more simple - As Tarzan often said: "Corner sound bad for room...Absorb corner sound..Room sound better...Tagging Flac files fun...Jane shake head again".

[Rob Babcock]

Listen to any small room with an adequate amount of Eighth Nerve treatments and you'll change your mind. 

Hey, maybe I would if you'd ever check your PMs!   Any of those summer deals left?

Sorry Rob.  This new Audio Circle software doesn't pop up a box when I have new messages and so I never notice.  It's also much harder to see what is new and what I've already read.  The sale page indicates to email me and that is certainly the best way to go.  I don't get PMs nearly as often.  If you are having trouble reaching me via email (meaning you've sent me two emails already, and the second one said, "Hey Nathan, where are you?") then shoot me a PM (and include your email address so I can compare) to make sure your mail isn't getting lost, but that shouldn't happen, I go through ALL my spam mail to make sure I don't miss anything.

At any rate, you have a PM. 

Best,

Nathan Loyer
Eighth Nerve

Yeah, I'm noticing that, too.  But I also did email you and didn't get a response.  Maybe it's your spam filter, or maybe a problem on my end.  Anyway, I'll check my PM.

[bpape]

I also want to clarify that I'm not bashing the 8th nerve product.  Having absorbtion in a corner is absolutely a benefit.  I've never argued any different - I just argue for something a lot thicker and larger (if you need/choose to use velocity absorbers as opposed to pressure absorbers) so it will work much deeper and yeild a more even absorbtion curve (at least we agree on one thing).

I only got involved in the discussion to clarify some overly broad, not quite correct statements. (ALL absorbers absorb more in the high end, our treatments aren't absorbers, you can't hear reflections, etc.).  I'm just trying to keep the explainations and the science behind what's happening correct. 

Bryan

[Ethan Winer]

Nathan,

> No energy in the room has passed through an absorptive acoustic material. <

I'm with the others on this - it doesn't make sense to me. But that's okay, not everything makes sense to me.

> I firmly believe that we'll be able to make a ruler flat room with no absorption very soon. <

Yep, right after the perpetual motion machine and an internal combustion engine that runs on water.

--Ethan

[PhilNYC]

I also want to clarify that I'm not bashing the 8th nerve product.  Having absorbtion in a corner is absolutely a benefit.  I've never argued any different - I just argue for something a lot thicker and larger (if you need/choose to use velocity absorbers as opposed to pressure absorbers) so it will work much deeper and yeild a more even absorbtion curve (at least we agree on one thing).

FWIW, in my old house, before going to a full 8th Nerve treatment, I was using a combination of bass traps (2 Echo Busters Phase 4 and 2 Bass Busters), corner traps (Echo Busters Corner Busters), and numerous 1st reflection panels (2" thick fiberglass panels from AcousticsFirst).  There is no question whatsoever that the 8th Nerve Adapt line had a far more positive effect on that room than the Echo Busters/AcousticsFirst treatments did...anyone from the NY Audio Rave who has been to my old house will atest to that.  I didn't do any measurements to see exactly what was happening, but the results weren't even close.  After putting up the 8th Nerve stuff, I did add the Acoustics First panels to the front wall, but honestly I don't think they had much effect at all after the 8th Nerve products were in place.

Obviously this was not scientific at all, but based on the physical dimensions of the 8th Nerve Adapt products (especially compared to the Phase 4 bass traps), they must be doing something differently than just bass trapping....

(disclaimer:  I'm an 8th Nerve dealer.  I'm also a reseller for AcousticsFirst)

[flintstone]

Nathan,

> No energy in the room has passed through an absorptive acoustic material. <

I'm with the others on this - it doesn't make sense to me. But that's okay, not everything makes sense to me.

> I firmly believe that we'll be able to make a ruler flat room with no absorption very soon. <

Yep, right after the perpetual motion machine and an internal combustion engine that runs on water.

--Ethan

I guess you missed this at CNN a while back: http://hytechapps.com/aquygen/hhos


Dave

[John Casler]

I firmly believe that we'll be able to make a ruler flat room with no absorption very soon.  The only difference between the anechoic chamber and that would be that the chamber would be much lower in volume.

-Nathan

Nathan,

Yep, right after the perpetual motion machine and an internal combustion engine that runs on water.

--Ethan

I have been reading this thread with interest.

What seems to be "left out" or maybe I simply fail to understand, regarding making a room "measure" flat with "reflection" rather than absorption is in TIME DOMAIN

If a musical instrument sound is produced by a speaker, the sound travels (distance/time/freq/Db/phase) and reaches our ear and then brain.  Then it continues to bombard us from various reflective surfaces, in a time frame "after" the original signal.

While playing test tones, this is not a problem since there is no time domain to remain true to, but with a cymbal, or a bass drum, late arrival room reflections are not and cannot be rebuilt or accelerated to join seamlessly with the original.

In the reflective claim of a flat room, is time domain considered, and if so, how is late arrival defeated.

And I cannot accept the concept that the brain will "ignore" or "reconstruct" the sound.  If the brain can hear the frequency combination of direct and reflected sound then it can certainly hear the differing arrival times.

Please know that I don't dispute the possibility of this sounding pleasant, or to some even preferable, but it is difficult to understand a statement of similarity of an Anechoic Room versus a Full Spectrum Reflective Room, when listening to music with "time domain" function.

And one last comment.  I make an extreme distinction between a two channel audio playback environment, and the goals involved, compared to trying to make a HT, and other venue type acoustic environments, provide accuracy, and enjoyment.

I see these all as having "specific" goals, that many times are not the same, and sometimes "quite" different.

[MaxCast]

Yep, right after the perpetual motion machine and an internal combustion engine that runs on water. Laughing

Do we need a combustion engine if we have a perpetual motion machine?

[bpape]

Phil,
I don't doubt that you may prefer the sound of the 8th Nerve to the other products you had previously.  Hard to say what the 'busters' are doing as they provide no specs.  Again, I agree that any treatment in a corner will provide a benefit - just a matter of how low.  I also don't know your old room, your system, how it was set up, etc. so any comment on my part with regard to that is uninformed at best.

Also understand that I deal with not only 2 channel rooms, but home theaters with subs that are doing 15Hz(seriously and at well over 100db - my personal sub will do 16Hz -3db at approx 114db though I never play it that loud), live and control rooms in recording studios, and smaller concert halls.  So I tend to look at things a little differently as I'm not just looking at things from how they perform in a 2 channel room.  That doesn't make my point of view any better or worse, just different.


John,
I agree.  There's a lot more to it than just frequency response.  Time dependent issues many times are ignored.  In my opinion, getting the decay times balanced across the spectrum is more important than the ultimate in 'flat' frequency response.  This is also why a 2 channel room and a multi-channel room are set up very differently. 

In a 2 channel room, as much as you don't want to, the room must help you reconstruct the spatial cues of the original venue (or the simulated one).  The trick is to keep it in line based on the volume of the room and keep it relatively even across the spectrum without killing it too much and making it sound dull and lifeless.

In a multi-channel room, you want a much shorter decay time (more dead) and you need the control spread throughout the space more.  Why?  Because you have 5 or 7 distinct channels that are recreating the ambient environment and surround field so you want less 'help' from the room.



Bryan

[Ethan Winer]

Dave,

> I guess you missed this at CNN a while back <

ROF,L. Let me know when they make a car that runs on water only.

--Ethan

[Ethan Winer]

Bryan,

> my personal sub will do 16Hz -3db at approx 114db though I never play it that loud <

You don't play it that loud? Why not?

--Ethan

[Ethan Winer]

John,

> If the brain can hear the frequency combination of direct and reflected sound then it can certainly hear the differing arrival times. <

Yes, when the delay is long enough. At short delays, less than 20 ms (or whatever) the main issue is the skewed response caused by comb filtering. I'm not disagreeing with you, because you hit the nail on the head! Time-based problems are at least as damaging as frequency response problems.

> I make an extreme distinction between a two channel audio playback environment, and the goals involved, compared to trying to make a HT, and other venue type acoustic environments, provide accuracy, and enjoyment. <

I know it's conventional wisdom that a 2-channel room should be more live than a home theater. But as I've added more and more treatment over time in my living room I've come to realize that one room can indeed sound excellent for both. It comes down to the opposing philosophies of whether the room should or should not impart its own character onto the reproduction. I have come to the conclusion that it should not. As soon as the room adds its own sound to the playback, you are no longer hearing what the mix engineers intended. The key is to avoid all early reflections. Once that's done you are hearing what the mix engineers intended. For the most part, and assuming bass and other resonances are also tamed.

--Ethan

[John Casler]

John,
I agree.  There's a lot more to it than just frequency response.  Time dependent issues many times are ignored.  In my opinion, getting the decay times balanced across the spectrum is more important than the ultimate in 'flat' frequency response.  This is also why a 2 channel room and a multi-channel room are set up very differently. 

In a 2 channel room, as much as you don't want to, the room must help you reconstruct the spatial cues of the original venue (or the simulated one). 

Hi Bryan,

Interesting.

Several things here, I would question:

I would suggest that there is "no way" to use an average sized room to "reconstruct" spatial cues.  Spatial cues, created "in room" (while they may be pleasing) are distortions to the original signal.  The "art" of establishing "decay times" in a room is the Acoustics Expert, "adding" (and there is nothing wrong with this if it is preferential) his artistry to the Sonic Experience being recreated.

Additionally, if the original recording has the subtle spatial cues of the original venue, then they are brought to compete with those of the room, and that competition is destructive to their sonic subtleties.

I would be less aggressive on this point with "Studio" recordings, but find you must treat for the one that gives you the most enjoyment, and accuracy (my preference).

The trick is to keep it in line based on the volume of the room and keep it relatively even across the spectrum without killing it too much and making it sound dull and lifeless

I find that interesting, especially the "dull and lifeless" idea.

In a two channel system, do you listen in the sweet spot, or out of that spot?

The reason I asked is that, the only place significant room treatment "reduces" HF, is "OUT of the sweet seat".  Obviously, this is because treatment is placed to reduce the negative effect of reflected sonics as they return to the listener in the listening position.

I might suggest that "fully treating" a room to reduce this "room distortion" will "never" make the sound "dull or lifeless" IN the sweet seat.  In fact, the opposite effect is true.

Reducing the room distortions, make the direct sound, more distinct, clear, and perceptible.  I have many times used the example of a completely dark room with a "pinhole" of light coming through the front wall.

It is CLEARLY perceptible, even as small as it is.

Now flood the room with reflected light, and you can't even see it.

The exact same thing is true of those delicate direct sounds.  If you want to hear "deeply" into the recording, you need to reduce room interaction to the barest minimum.

If you simply want to hear the "twinkle and tinkle" while dusting and walking around, then it must be sacrificed, at the listening position.  It is a sliding scale compromise.

If you are a "High Performance Listener" the choice is obvious.  If you wish to have both then you get to start "sliding the scale" of measured treatment.

In a multi-channel room, you want a much shorter decay time (more dead) and you need the control spread throughout the space more.  Why?  Because you have 5 or 7 distinct channels that are recreating the ambient environment and surround field so you want less 'help' from the room.

Bryan

Strangely enough, I have less issues with HT treatment because:

1) It has NO "Live Reference" due to most every sound being dubbed or foleyed, and subsequently we cannot design the treatment to the "true" sonic.

2) Even if we take the "in Theater Experience" as "the Live Reference", today's DVDs are not encoded with the spatial cues to reproduce the size and volume of a standard sized theater, so treating a room to allow for such seems like an exercise in futility.

3) I find that "because of the above" and that there are more speakers (6-9) that the sonic dominance of all those speakers in a moderately treated room (bass treatment withstanding) will give me a pleasing and reasonable result, in most cases, better than an actual theater.

Needless to say, my HT and Audio Systems are separate

[bpape]

Interesting thoughts John.  Again, you're thinking in terms of frequency response when you're addressing my 'dull and lifeless' comment.  I was speaking more of a lack of room ambience regardless of FR.  If I'm treating a room for a mix of 2 channel and HT use, I tend to leave the rear of the room a bit more live and use a mix of a bit of absorbtion mixed with diffusion as I described earlier.

I'll agree that you'll never get a residential room to create an original venue - much less all venues.  But I do think one can make it more capable without absolutely killing it.  To me, a completely dead room is very uncomfortable to be in and I find 2 channel music listening similar to listening to headphones.

One other thing, to me, the trick in being able to 'listen deeply into the recording' is by designing the room to be quiet - not necessarily dead.  This is why isolation is so important.  It's not all about keeping sound from getting out.  IMO it's more important to keep it from getting in and mucking up the ambient noise floor of the room.  A very quiet room with a moderate amount of treatment and good bass control will allow good, relatively smooth frequency response at many different spots in the room - not just one sweet spot.

Bryan