• Making speakers "disappear"

At any rate, Floyd and JBL are moving towards a narrower directivity, which seems to contradict the conclusions that you state.

And, the situation is more complex. The reverberant field depends on two factors, directivity or power response, which excites this field and the rooms reverberation time - absorbtion (I hate the concept of RT for small rooms, and its not too popular for big rooms either). I agree that people prefer a spatious sound, which can only come from a strong reverberant field, but that can be done with a directive speaker in a lively room just as well as a low directvity speaker in a deader room. The directive speaker however will have a far cleaner direct sound - early impulse response - and hence far better imaging, than the wider directivity speaker.

You see, putting speakers in the same room and comparing them depends a lot on the room. In a dead room people probably will prfere a wider directivity, while in a lively room they will prefer the narrower directvity. But I would suspect that a comparison between the better dead room combination and the better live room combination would result in a strong prferernce for the more lively room with the narrower directivity.

No tests of this nature have been done in a scientific manner, but my personal experience strongly supports this belief. And people (clients) always seem to like my rooms.

Finally, as I show in my white paper (see www.gedlee.com) constant directvity cannot be achieved in a small cabinet. Big is required for this to happen and I think that the current trend towards smaller systems is why even though the drivers are much better than ever, the sound is not any better and in many cases worse than the old days when "bigger is better" ruled.

Did you measure the polar response of your system to insure that it is CD?

After readin your comments, I'd be interested in your views on the LEDE idea...

First, CD from 350 Hz up at any reasonably narrow coverage is pretty much impossible. If you are talking about say 180 degree coverage, then I could believe it, as its pretty easy to get very wide CD coverage. The trick is CD coverage at about 90 degress or less, which is what is required to avoid early lateral reflections. This could almost never be done down to 350 Hz in a small room due to the source size. If you have data to show otherwise, I'd love to see it.

I strongly disagree that "lateral early reflections are all right since they are processed bi laterally by the ears". First, if the lateral reflection arrives at the same ear as the direct sound, then no amount of auditory processing can affect it since the two waves are mixed before they even enter the ear canal. A lateral reflection to the opposite ear from the direct sound is less offensive because of processing as you say. But, the opposite ear situation is the lsees common in most situations.

Vertical reflections cannot influence image since imaging is stricly a horizontal process. So the situation is this; vertical reflections mostly affect coloration and horizonal reflections mostly affect imaging, although they do also affect coloration. This is why I am of the opinion that horizontal reflections are the more damaging.

THX would presumably spec a lower directivity in the vertical plane because virtually all small rooms have a lower ceiling to floor distance than sidewalls.

In all my designs I correct for both, but it is my experinence that the lateral early reflections are the most critical.

About the Toole work. First, I don't think that his paper did show a preference for wider dispersion types. Would you please quote the article if you think that this is so - I have read and poses them all. Second, Floyd's work at the NRC never involved music, only noise and impulses. So determining a preference for directivity on music would not have been possible.

On page 343 he goes on to comment upon work by Kuhl and Plantz about how people such as recording engineers prefer directional loudspeakers for work, but tend toward less directional ones in their home.
The design criteria from which I took the directivity characteristics of my louspeaker system from come from Kates in the paper,"A perceptual criterion for loudspeaker evaluation", AES Journal Vol.32, No.12, 1984. On page 940 in the section "Floor reflection", he states as you do that a reflection coming from the same direction as the direct sound will have no binuaral echo suppresion, and shows that at typical listening distances will fall in the critical band and, "Thus we would expect floor reflection to be an important cause of colouration".
Your loudspeaker system I note has 90 degree vertical directivity, in which case early vertical reflections will be a definite feature.

Thanks for actually supplying supporting data for your position. This is Soooo refreshing to see in a world dominated by hype and voodoo! Science and audio seem to be unrelated on these sites sometimes.

For a 500 mm rectangle the lowest frequency for which the directvity could be 90° is 620 Hz. It will narrow above that. IMHO, to have CD from 350 Hz up with this source is not possible. At ;east not within the laws of physics as I know them.

I have often heard CD claimed and have sometimes tested this claim. Never has it actually been shown to be true. I posted my measurements to prove my claim, as it is the first, and only, time that I have actually measured a true CD system (at least above 800 Hz). It is one thing to make the claim of CD because it "should be" or "I think it is" and quite another to actually achieve it. That is why I am always skeptical of this claim until it has been shown with actual measurements.

The Toole references do not "prove" your point. They describe circumstantial evidence, but do not show a cause and effect relationship. Neither does the audio engineer reference. Perhaps the engineers can't afford high directivity speakers at home, and maybe there was something else in the speakers in Floyd's test that the listeners objected to. Who knows.

Yes my speakers are 90°, and yes it would be nice to have a narrower vertical coverage. But then the coverage would not match between the woofer and the waveguide and the resulting system would not be CD and would not have a smooth pwer response. I choose CD. I recommend and use floor absorbtion and ceiling dispersion to alleviate the vertical reflections in short height rooms. My room has a clean 10 ms of direct sound before there are significant reflections. This has also been measured and is posted on my site.

Thanks for the discussion.

I would dearly love to see these measurements since your claim does test my credibility. But testing at 15° increments only up to 45° is only a very approximate test. To me the data should be at least 7.5° increments and cover the range +- 90°. If these measurements are as you claim then this would truely be a breakthrough as I have never, in more than 30 years, seen such good performance from a midrange horn.