[JLM]

To sum up with I, 8th, Rob, and Ethan are saying:

High frequency sound is like a low energy laser beam (directional and with the right material encountered can reflect off of it).  It's these reflections that confuse imaging (when delay times are too short, say 0.1 milliseconds) and limit soundstage width to the room dimensions.

Low frequency sound is more like giant waves (that crash and flood against everything in the room).  These waves pressurize and overall room with the highest pressures in the recesses of the room.


8th:

So your products only address low frequencies, right?

Rob:

Thanks for quoting an authority figure to clarify what I tried to say.


Ethan:

Seems like if the recess in the room is small enough it should begin to act as a bass trap which act as a pressure relief.  But I don't know the theory behind bass trap designs.  I've seen some stuff on it that presented it as tubes with a closed end with open end to the room that are tuned to different frequencies, unfortunately I no longer have the link.

[Ethan Winer]

J,

> Seems like if the recess in the room is small enough it should begin to act as a bass trap <

What recess? A recess is not a bass trap. Unless it's packed full with fiberglass or an equivalent material.

--Ethan

[satfrat]

J,

> Seems like if the recess in the room is small enough it should begin to act as a bass trap <

What recess? A recess is not a bass trap. Unless it's packed full with fiberglass or an equivalent material.

--Ethan

         So the recess's in a Real Trap or the Furutech RWL-1 don't suppress but actually amplify the sound with their diffusion? (just wild thoughts being thown out here) Regards, Robin

[Ethan Winer]

Sat,

> So the recess's in a Real Trap <

You have lost me completely. What recess? I designed the MiniTrap and there's no recess I know of!

--Ethan

[satfrat]

Sat,

> So the recess's in a Real Trap <

You have lost me completely. What recess? I designed the MiniTrap and there's no recess I know of!

--Ethan

Sorry Ethan, I haven't ever seen your products so I have no  firsthand knowledge an was assuming that the design was simular to what I have. If you'll scan back in this thread, I described the product that I'm using for a DIY design possibility. I like what hear and was searching for maybe an explanation of why/how. With 45" long rows of hard styrofoam 1/2" thick and spaced 2 1/2" apart, troughs are made available for the sound to collect. Like I said, wild thoughts, I've been known to have them. I'll be looking foreward to meeting you and sampling your products at the NY Sterophile Show next month. Maybe I can learn something then. Regards, Robin

[Ethan Winer]

Robin,

> If you'll scan back in this thread, I described the product that I'm using for a DIY design possibility. <

Okay, now I see. That sounds like it's supposed to be some sort of diffusor. But if all the cavities are the same depth, it won't do anything useful as far as I know.

That is completely different from the absorption products my company sells.

And yes, please stop by our booth next month at HES and say Hi.

--Ethan

[8thnerve]

8th:

So your products only address low frequencies, right?

Not at all.  All frequencies are affected in different ways.  The absorption component is effective at all frequencies, and the reflection component is relevant to the higher frequencies.

[JLM]

O.K. 8th, still confused...

It makes sense to me that if pressure from low frequency sound waves builds in the corners (intersections of 2 or 3 walls) your pillows should go in the corners (as I believe you recommend).

But if high frequency sound waves act more like low powered laser beams (reflecting sound) it seems like absorption devices should be located at the first reflections points between each speaker and each side wall (1 on each wall for each speaker), ceiling, and floor (8 locations total), not in the corners.  Sure most rooms could use some absorption and the pillows would help to some degree no matter where you put them, but corner locations would seem to be far from ideal or highly effective.

[8thnerve]

O.K. 8th, still confused...

But if high frequency sound waves act more like low powered laser beams (reflecting sound) ...

More like is very different than like.  High frequency sound waves are still a far cry from light waves.  Our products attentuate very little at the highest frequencies, because frankly, you don't need much high frequency absorption.  Most rooms can barely pull off a flat response at 16K much less 20K or higher.  By eliminating a large portion of the 90 degree angles in the room, you eliminate the bad high-frequency energy, namely echo and distortion.  You don't want to attenuate the highs overall, just the problematic parts.  In many of our installations for customers with overly dead rooms, our products will actually increase the high frequency output overall, while reducing echo and distortion.

[JLM]

Thanks for the reply.

Yes, I used the phrase "act more like" understanding that high frequency sound waves don't simply/perfectly beam.

Could you share how the room pillows help with echo and distortion?

And could you explain why you wouldn't want absorption at first reflection points?

thanks again

[nathanm]

No offense but...discussing 8th Nerve's product philosophy sounds like a great topic for a new thread.  I just wanted to know what constitues a diffusor - is it JUST the shape or is it the shape + material? Does a chunk of foam really care which way its cut or what?  That's all I ever wanted to know on this matter.  Thanks!

[John Casler]

In many of our installations for customers with overly dead rooms, our products will actually increase the high frequency output overall, while reducing echo and distortion....

Hmmmm?

How can a *passive device* "increase the high frequency output overall"?

Even a horn doesn't increase output, it only delivers output more efficiently.

It would seem that the "output" can only be "increased" by an active
means.

Most rooms can barely pull off a flat response at 16K much less 20K or higher. By eliminating a large portion of the 90 degree angles in the room, you eliminate the bad high-frequency energy, namely echo and distortion.

I seem to be confused.  How can the "room" affect the ability of a "speaker" to reproduce a frequency, if nothing is between the speaker and the listener, except for phase cancellations caused by reflected sound?

Surely, again passive devices cannot "increase" a speakers frequency response, in nearfeild, on axis testing or measurement.

Employing out of phase "reflected" high frequencies cannot be a goal to accurate reproduction.  It would seem to stand to reason that reducing the "out of phase cancellations" of reflected frequencies via absorption would "improve" overall response.

I certainly agree that treating as much of the intersecting boundaries makes sense, but somehow I get lost with the utilization of "room created" sound from the original.

While I can possibly see the value of this in a "live venue" where "sound reinforcement" might be important, you lose me when you take what was recorded in a concert hall and do anything except try to reproduce the purity of the original signal.

[_scotty_]

John, this seems to be a conflict between LEDE in the home evironment and even decay spectrum in the room as a whole and not just in the back half of the room. The reproduced decay spectrum could be shifted away from flat by excess absorption of any frequency in the spectrum of reflected  sound. Comb filter effects can create deep nulls at specific frequencies and even more objectionable peaks of as much as 6dB when direct and reflected signals are in phase. Most of our listening room treatment efforts are directed towards the reduction of comb filter effects that produce audible colorations. For most of us we are only able to deal with geometric frequencies in our listening rooms and the low frequency problems are more intractable.

[8thnerve]

No offense but...discussing 8th Nerve's product philosophy sounds like a great topic for a new thread.  I just wanted to know what constitues a diffusor - is it JUST the shape or is it the shape + material? Does a chunk of foam really care which way its cut or what?  That's all I ever wanted to know on this matter.  Thanks!

Essentially a diffusor is a device that reflects sound with a non-flat surface.  A flat surface would be pure reflection.  Using the flawed light analogy, any reflective surface that is not flat will scatter the waves, causing diffusion.  The types of diffusion are many, but that is the basic guideline for a "diffusor."  For the record, I think diffusors are less effective than plain ol' reflection, but I am sure many will disagree.

[8thnerve]

Thanks for the reply.

Yes, I used the phrase "act more like" understanding that high frequency sound waves don't simply/perfectly beam.

Could you share how the room pillows help with echo and distortion?

And could you explain why you wouldn't want absorption at first reflection points?

thanks again

Well, we find that most distortion is caused by the 90 degree angles in a room.  By putting the Response products at a 45 degree angle in these areas, the sound is free to reflect off this area with less distortion and much of the distorted sound is absorbed by the product from the rear.

Echo is more complicated and we are still trying to understand exactly  why it works the way it does.  However, ask any of our customers, and they will tell you that when they put the product in the ceiling/wall corner adequately, echo is virtually eliminated.  Sorry, but that is a long and unfinished discussion so I will have to defer this time.

First reflection points.  We don't want plain absorption ANYWHERE.  Now, you could use absorption/reflection, like placing a Seam at the first reflection point (many of our customers do) and that is not detrimental.  The reason we don't recommend it is because it is far less effective than treating the corners.

[8thnerve]

John, please understand that your views on acoustics and mine are as far from each other as they possibly could be.  While I am happy to explain my methodologies, I simply don't have the time to go point to point in this venue.  That is much better accomplished over alcohol and tobacco with a  few evenings to spare.

However, since I can't resist...

How can the "room" affect the ability of a "speaker" to reproduce a frequency, if nothing is between the speaker and the listener,

In your listening position, a large portion of the sound output you are observing is room coupled.  Unless you are in an anechoic chamber, you are getting 6-12 db of room gain on average.  If a room is heavily damped, you'll get less room gain in the higher frequencies, causing a "reduction" in overall HF output.  By putting product in that reflects the HF instead of absorbing it, you "increase" the output.  And all that from a passive device.  

except for phase cancellations caused by reflected sound?

Methinks you are too concerned with this.  If you speakers are more than a millimeter different in distance, you would have more significant phase cancellation from the speakers themselves.  Few sonic wavefronts ever merge on a parallel plane, and the small portions that do are insignificant compared to the ones that simply cause interference patterns that are decoded by the ear/brain...  the Eighth Nerve that is!  I've been waiting to use that!

Employing out of phase "reflected" high frequencies cannot be a goal to accurate reproduction.  It would seem to stand to reason that reducing the "out of phase cancell ...

Again, it's either an anechoic chamber or it's not.  One step forward, two steps back.  The room is a contributor to your sound, like it or not.  Trying to stop the room from contributing is like trying to get the ocean to sit still because you don't like the sound of the waves, it's not going to happen.