[_scotty_]

Rob,Owens-Corning 700 series semirigided fiberglass  boards are what you are looking for. They have a constant coefficient of absorption with frequency and their efficiency at frequencies below 250Hz is limited by thickness of the board. You can make a LEDE room that doesn't look like
what it is. This is what is frequently used in professional applications. The only draw back to this product is that it is not inexpensive.

[John Casler]

Not only that, but John G. McKendrick way back in 1896 gave a lecture in Glasgow that pretty much spelled out that when two waveforms collide, the resultant waveform is the sum of those two.  This almost always results in a waveform that is inharmonic with regard to either of the original waves.

My guess is that Casler just hasn't experienced playback in a good room that has been treated well, and not overly so.

Hi Hantra,

I don't see anything in my comments that would lead you to that conclusion.

I have probably been in, or set up, hundreds of rooms, including anechoic chambers and recording studios, booths and stages.

There is very little I haven't heard including a similar amount of "live" performances.

I have sat in on numerous recording sessions (helps to have a few "rock stars" around) and live and recorded music sessions.

And to clarify, I totally agree about intersecting boundary reflection and have it in my own system and suggest it, along with front wall and 1st reflection treatments.

While I have heard many acoustic treatments and combinations, I have never heard a room reflected/generated "primary" sonic that didn't detract from the performance, "if" one knows what to listen for.

The Sonic Hologram is a "delicate" animal, and while there are many pleasing sounds, none created by "reflection" can contribute to it in a way I have ever heard that didn't detract.

How many LEDE systems had you heard?

Both John and 8thnerve may be right in their assertions depending on the loudspeakers radiation pattern and its location in the room. What 8th nerve may advocating is a more even spectral decay in the treated room.The empirical test for the effectiveness of any room treatment,is an assesment of speech intellegibility and flatness of response at the listening position.

My preference has been for LEDE type rooms based on the loudspeakers
I have heard. If a precise recreation of the original waveform as captured by the microphone is to reach the ear the rooms contribution has to minimised. To many people LEDE rooms sound strange and people may become uncomfortable in them due to unfamiliarity. Most people cannot dedicate a room solely to listening to music or home theatre and a LEDE room is not the most aesthetically pleasing sight visually.

I think Scotty says it well.  

In fact the quote:

If a precise recreation of the original waveform as captured by the microphone is to reach the ear the rooms contribution has to minimised.

That sums it up for me, in one sentence.

And it should be evident that there are many steps from "NO treatment" all the way to a fully dedicated LEDE.

I certainly don't have an LEDE, but approach it as best I can in a functional living room.

In performing "treatment" I think the most important and critical areas are:

1) Points of "1st" reflection
2) All Intersecting room boundaries
3) Frontal Reflection
4) Bass Nodes

These are in no particular order, and really the order would depend on just how bad each behave in your setting.

I think 8thnerve's approach reflects a modification of sound treatment practices based on real world considerations and what level of decor alteration a customer will accept to achieve an improvement in sound reproduction quality.

I also agree here and again am not detracting from any Eighth Nerve product, method, or result  (just adding my own experience and opinion)

I too think they are attractive and effective tools for some of the "sonic grunges" we face

I will have to admit I don't understand how a sound wave impinging on a wall and causing a tympanic surface to resonate and reradiate a sound wave equates to laminar flow. A walls contribution to reradiation in this manner, and at what frequency it occured, could be easily measured with an accelerometer placed on the wall.

That too was my question in another thread.  

I'm not sure there is enough air movement to get laminar by definition.  

Correct me if I'm wrong here, but I think think the real comparison or use of the term has to do with the fact that laminar here is meant to potray "smooth" (undistorted) sonic waveform flow, while most sound becomes distorted by the turbulence created when it encounters various surfaces.

I think a little license is taken with the definition (as I understand it) but the term does offer the "smooth to disturbed" comparison.

Hope I guessed that close to correct.

And as a parting shot, I'd like to see more "focus" on treatments like those of Eight Nerve and Real Traps.  In the scheme of sonic bliss, no matter "how" you like your sound, you find many spend hundreds (if not thousands) on Cables and Interconnects, while ignoring the 2nd biggest factor to affect the sound of the system ....the room.

[8thnerve]

I will have to admit I don't understand how a sound wave impinging on a wall and causing a tympanic surface to resonate and reradiate a sound wave equates to laminar flow.

They don't.  But rereading what I wrote, I can see how that came across.  Here is the excerpt:

Laminar flow, the tendency for the wall surface to sympathetically vibrate with the sound wave, the combination of the returning sound waves with the incoming ones, all contribute to the sound that eventually hits our ears.

This meant to be read as 3 items, 1. Laminar Flow, 2. the tendency for the wall surface to sympathetically vibrate with the sound wave, and 3. the combination of the returning sound waves with the incoming ones.

Sorry for the confusion.  An "and" and some reorganization would have made it more readable.  My bad.

Also, I qualified the Laminar Flow statement earlier as being an analogy and not entirely applicable without modification.

[Ethan Winer]

Hantra,

> Let's say that you would get 5% broadband absoprtion from 3" of foam at all frequencies. <

It doesn't work that way. Even thin material like 1/2 inch of acoustic foam absorbs 100% above a certain frequency. What happens as the material is made thicker - or replaced with better material like rigid fiberglass, or an air gap is added - is the amount of "effective absorption" is extended to lower and lower frequencies.

> How is that different from just taking an old Kenwood EQ and pushing the knobs down 5%? <

One big reason EQ cannot solve low frequency acoustic problems is the inevitable peaks and deep nulls are very localized. Any correction you apply will fix only a tiny area, and will surely make other areas much worse. Another big problem with EQ is it does nothing to reduce modal ringing that muddies bass instruments. The reduction of ringing is just as important a feature of bass traps as is flattening the frequency response.

--Ethan

[Hantra]

Thanks for the explanation Ethan.