[Ethan Winer]

Those were the days when bookshelf speakers were really put on bookshelves 

LOL, indeed. And often on different bookshelves, at different heights, and at opposite ends of the room.

One other thing I didn't see mentioned yet is that it's easy to measure the strength of reflections using software like Room EQ Wizard and ETF. This lets you see how well "beaming" type speakers and toe-in etc are actually doing what you hope for.

Another, less direct, way to assess the strength of reflections is to simply look at the frequency response at high resolution. In this case third-octave averaging is not appropriate because it hides the true extent of the peaks and nulls. The graph below shows the difference with and without side-wall absorbers in place.

--Ethan

[TRADERXFAN]

Well, the controlled directivity speaker setup is trying to avoid the timing problem, rather than the overall strength. So RTA will not provide any help with measuring success of this strategy.

[Kevin Haskins]

Those were the days when bookshelf speakers were really put on bookshelves 

LOL, indeed. And often on different bookshelves, at different heights, and at opposite ends of the room.

One other thing I didn't see mentioned yet is that it's easy to measure the strength of reflections using software like Room EQ Wizard and ETF. This lets you see how well "beaming" type speakers and toe-in etc are actually doing what you hope for.

Another, less direct, way to assess the strength of reflections is to simply look at the frequency response at high resolution. In this case third-octave averaging is not appropriate because it hides the true extent of the peaks and nulls. The graph below shows the difference with and without side-wall absorbers in place.

--Ethan

Have you read the Griesinger & Hidaka papers (1997)?    Toole's book talks about several of these studies and his conclusions are just the opposite of what is common practice.    They found a strong preference from listeners for soundstage illusions that correlate to the front stage as coming primarily from reflections < 80ms.    That would include all the early reflections and his conclusion was that absorbing first reflections is the opposite of what we should be doing.      I also found it interesting that in those studies that the results differed for professionals.   There was a preference from the mastering engineers for more directivity, or fewer early reflections that didn't correspond with the general population.   

[JLM]

Yes, the original concept of stereo was to allow for the creation of a 3D image.  (But soon marketing types realized that they could sell more gear, except for Klipschorns due to the fact that few real world rooms are symetrical and have two adjoining/usable corners).

I'm a LEDE fan (don't know what a EFZ is).  I agree that the bigger the room the better due in part to the longer delays between direct and reflect soundwaves reaching the listener.  I have six GIK 244 panels at front/side wall first reflection points plus in the front corners.  I'm a firm believer that room treatment should be done before any equalization.

I'm also a single driver fan.  At higher volumes few if any drivers exhibit pistonic behavior, so I don't understand the comment below.  A single sound source has no crossover problems while providing a more coherent presentation that optimizes imaging.  The whizzerless 8 inch drivers "beam" high frequencies to reduce room interaction.  I toe in (season to taste).  A Behringer DEQ2496 provides all the needed baffle step, zobel, and room correction (tweaking only).

My dedicated listening room is purely ala Cardias (room dimensions and nearfield speaker/listener setup).  Standing waves and room interaction are minimized. 

I also found that maximizing stereo separation helps with imaging.  To that end I use monoblocks.  With single driver speakers the result is purely equivalent to having "active" speakers.  (I heard a comparison years ago and became a huge fan of that concept too.)

A recent upgrade of DAC's has brought improved detail/resolution and as always that means better focused imaging.  But the image now extends past the speakers.

As always you'll be limited to the source material.

The bottom line is that anyone can hear the imaging.  Even the eyes of 8 year olds go wide open when they sit in "the chair" and experience the "stereo effect".

[woodsyi]

Yes "beamed" at you, if you want to use that word. Not exactly on axis, but that is just a finer point based on the designed response.

No smearing. Every detail is clearly heard. This also due to efforts expended to minimize diffraction on the speaker itself.

Don't be afraid. This is a good thing!  After the small window of time, <20 milliseconds, (when a reflection will cause smearing in our hearing) the reflections do come back around and everything sounds natural.  --Oh should add, the layout is to have the reflection strike the opposite ear, as we psychoacoustically process this differently from the direct sound to the "same side" ear.

http://www.gedlee.com/downloads/Cum%20laude.pdf
page 6

 

Alright, I read the whole white paper.  Give the man a degree with hightest honors. 

I can follow and understand the logic behind everything he wrote.  I still think 1st reflection treatment is a good thing even with directed speakers since ideal set up conditions don't always exist.  I have never been a fan of radical toe-in but then I never tried the Summa.  I have SP AV1 (wave guide) and they are definitely one of the most clean sounding speakers and they are only slightly toed in as they are about 20 ft away in my bedroom. 

Here is my finding with room treatments.  Early reflection point treatment (absorption or diffusion) cleans up smears to enable you to clearly locate instrument and give you width to the sound stage.  Holographic or deep sound stage was achieved with a rear wall diffuser.  Even though I listen near field, a big SRL diffuser (4' x 6' with 9" well depth of a prime sequence) in the rear wall locks in the sound stage.  Without it, I don't get the depth.  There is more to what we hear than just the direct sound.  I am thinking that even with the guided low dispersion speakers, controlling higher order modes stemming from bounces on the wall (as opposed to baffle related smear) will improve what you hear.  At least that's what I found in my room.

[JackD201]

EFZ (Echo Free Zone) is oft interchaned with RFZ (Reflection Free Zone) in normal parlance. It's actually a misnomer because obviously you're going to get some reflections enventually.  Normally it is used for near or at most mid field listening with the goal of providing as much direct sound as possible. What makes it different from LEDE or DELE is that normally first reflection points are first far enough to be well outside the Haas window and the the first reflections are redirected to a second reflection point that either uses absorption, diffraction or a combination of both to third and sometimes even fourth reflection points. The principle is to let the natural loss of amplitude to to the distance travelled of the sound wave to be the primary attenuator only after which heat transfer is used through a series of velocity or pressure devices. Hence because the time the reflected sound waves get back directly to the listening position the HF waves have lessened about 5dB for every doubling of distance travelled and even less because of the "catch treatments" they have to pass through. No  first direct reflections and no echo. The advantage is incident or non-direct first reflections from the first reflection points retain enough energy without the tizz of of a first reflection beamed too the ears. It is, come to think of it, a cross or compromise between the effects illustrated by Griesenger and Hadaka. Perfect for me because I'm a former pro and now just a happy listener.

Architecturally, throw the rectangle room model out the window. EFZ  designed rooms are symmetrical left and right but have ceilings and walls splayed at angles usually at a minimum of 2 inches for every 10ft. The room thus looks very irregular in shape. Think a more complicated wide trapezoid with speakers placed along the second widest wall, the front wall. The absence of parallel walls in itself provides relief from standing waves however corners now tend to have angles less or greater than 90 degrees in either axis that have to be filled as well.

Needless to say rooms such as this are designed from the ground up and are actually used extremely rarely in domestic settings. It is however used more and more frequently in today's recording control rooms where incidentally I grew very fond of the effects. They are very difficult to design and build making use of extensive ray tracing and modeling.

I'm now in the process of building a music room in my prime number configured basement of 3m H x 7m W x 11m L dimensions which pretty much guarantee no doublings and even modal distribution at a fairly easy to handle 180Hz. It is a hybrid of EFZ and LEDE in that I'm setting up my loudspeakers along the shorter front wall but the trapezoid is narrow instead of wide. Cutting costs I opted for a series of hung clouds instead of a complicated ceiling plan. Eventually starting position will be speakers 10 feet apart, 10 feet from the front tweeters to the back wall and 10 feet to the listening position forming a diamond consisting of 2 10 foot equilateral triangles This leaves about 6 feet from either redirected side walls.

[Ethan Winer]

Well, the controlled directivity speaker setup is trying to avoid the timing problem, rather than the overall strength. So RTA will not provide any help with measuring success of this strategy.

Regardless of strategy, you can still measure the frequency response arriving at your ears and decide if it's acceptable or not. For example, if you have highly directional speakers and plan to adjust toe-in to minimize splash off the side walls, a response test will show how well you're doing.

--Ethan

[Ethan Winer]

Have you read the Griesinger & Hidaka papers (1997)?

No.

They found a strong preference from listeners for soundstage illusions that correlate to the front stage as coming primarily from reflections < 80ms.

You mean like Bose 901s where most of the sound is reflected off the walls?

There was a preference from the mastering engineers for more directivity, or fewer early reflections that didn't correspond with the general population.

This corresponds with my own experience, where some audiophiles say they prefer a room that is more on the live side. But it seems to me this is a matter of "educating the consumer." I think it's safe to say that mastering engineers are highly skilled listeners since they (presumably) have a successful career of listening and making decisions based on what they hear. I've converted more than a few people after they heard the "reflection free" environment in my living room system. But personal preference varies, and nobody can say one way is right or wrong.

--Ethan

[woodsyi]

I like a lively room and that means I have to control the chaos.  You got to treat the room to scatter those waves.  You don't want those rascally waves organizing and unionizing - next thing you know is you got standing waves.  You don't want them standing.  Trust me, you've got to knock them down and keep them down with treatment.  Scatter them good is what I say.

[youngho]

They found a strong preference from listeners for soundstage illusions that correlate to the front stage as coming primarily from reflections < 80ms.

You mean like Bose 901s where most of the sound is reflected off the walls?

No, the direction, delay, and level of the reflections all matter, so the 901s would not do well on any of these counts in typical rooms.

Kevin didn't mention that the timbre or spectral content of the reflections matter a great deal, so the off-axis response and directivity of the speaker have to be good when considering Toole's suggestions regarding preservation of sidewall reflections for stereo listening...

[bpape]

Great point.  People tend to forget that the farther off axis you get, the more the tweeter output varies from ideal.  So, when you toe in a lot, your reflections are not only still there, but are also farther from the direct sound in terms of response curve.

Bryan

[jtwrace]

So, when you toe in a lot, your reflections are not only still there, but are also farther from the direct sound in terms of response curve.

Bryan

Does this apply to an electrostat as well?

[bpape]

It depends.  Due to their nature, they tend to null at lower frequencies off to the side.  Curved panels don't exhibit rolloff as much as flat ones.  Most ES's tend to roll off highs more in the vertical direction rather than the horizontal.

Bryan

[TRADERXFAN]

Great point.  People tend to forget that the farther off axis you get, the more the tweeter output varies from ideal.  So, when you toe in a lot, your reflections are not only still there, but are also farther from the direct sound in terms of response curve.

Bryan

The off axis response of a controlled directivity speaker should be designed to fall off evenly...

From my understanding, dome tweeters, don't do as well as compression drivers loaded in a horn/waveguide, in this regard. So, if that is indeed true, you have to specify what is being loaded in a CD device when you say that.

-but maybe I misunderstood to what you refer. Maybe you were talking about non-CD speakers, only?

[nathanm]

Room treatments can help, but if you really want a holographic soundstage you need to bite the bullet and invest in an R2 unit.  If you buy used, make sure it has a good motivator, though.

[Kevin Haskins]

Have you read the Griesinger & Hidaka papers (1997)?

No.

They found a strong preference from listeners for soundstage illusions that correlate to the front stage as coming primarily from reflections < 80ms.

You mean like Bose 901s where most of the sound is reflected off the walls?

There was a preference from the mastering engineers for more directivity, or fewer early reflections that didn't correspond with the general population.

This corresponds with my own experience, where some audiophiles say they prefer a room that is more on the live side. But it seems to me this is a matter of "educating the consumer." I think it's safe to say that mastering engineers are highly skilled listeners since they (presumably) have a successful career of listening and making decisions based on what they hear. I've converted more than a few people after they heard the "reflection free" environment in my living room system. But personal preference varies, and nobody can say one way is right or wrong.

--Ethan

I'm not trying to be a stinker.   I just figured I'd ask.       In all of these studies, the perception of space had a high correlation with "good" sound quality.    Obviously, "good" is a subjective call.    The point made about professionals was that we should be careful about our definitions of "good" because they might differ from that of our customers.   

[bpape]

Great point.  People tend to forget that the farther off axis you get, the more the tweeter output varies from ideal.  So, when you toe in a lot, your reflections are not only still there, but are also farther from the direct sound in terms of response curve.

Bryan

The off axis response of a controlled directivity speaker should be designed to fall off evenly...

From my understanding, dome tweeters, don't do as well as compression drivers loaded in a horn/waveguide, in this regard. So, if that is indeed true, you have to specify what is being loaded in a CD device when you say that.

-but maybe I misunderstood to what you refer. Maybe you were talking about non-CD speakers, only?

Yes.  Non-CD is what I was referring to.

[PhilNYC]

In terms of soundstage depth, I found that mine improved dramatically after I put diffusers on the wall behind my listening seat....

[Kevin Haskins]

They found a strong preference from listeners for soundstage illusions that correlate to the front stage as coming primarily from reflections < 80ms.

You mean like Bose 901s where most of the sound is reflected off the walls?

No, the direction, delay, and level of the reflections all matter, so the 901s would not do well on any of these counts in typical rooms.

Kevin didn't mention that the timbre or spectral content of the reflections matter a great deal, so the off-axis response and directivity of the speaker have to be good when considering Toole's suggestions regarding preservation of sidewall reflections for stereo listening...

Yes... and from the Hidaka (1997) the spectral content from 350Hz-2.8K is most critical.   Extend that a little and you have the midrange as the critical area.    Since there are very few loudspeakers that have constant directivity over that range, you see very uneven spectral content in early reflections.   It may be that, rather than the reflection itself that is influencing the preferences.   

[TRADERXFAN]

In terms of soundstage depth, I found that mine improved dramatically after I put diffusers on the wall behind my listening seat....

How far away was your seat from the wall?  I am curious about how much this distance matters to the results.