New study on loudspeaker placement

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I'm too dense to understand what he's trying to show. Wouldn't it be more helpful to examine the case of a central phantom image and show how moving the listening point to the left and the right affects the localization of that center phantom image (incorporating directivity data of different loudspeakers)?

Markus

That is precisely what it does show, or attempts to show.
 
Earl,

By the way, your Polar_map app is defunct for months now.

Markus

It works for some but not for others. Since it always works fine for me I have no way to debug it. I do know that it will only run if you run the install from within windows Explorer. Any attept at installing it locally will not work. Also it will not work in an OS setup that uses a comma for a decimal point.

Why yours is looking for files on your "C:" drive is baffling since there should not ever be anything local, its a web app.
 
Would be nice to see how the phantom center shifts with a shift of the listener.
Did you look at the equations in the paper that I've quoted?

The amount of shift is proportional to the color. Yellow is no shift and black pulls the image completely to the nearest speaker. There is no case, I checked, where the image reverses, i.e. to the left as one moves right, so it not necessary to describe which direction the image moves, just how much it moves and that is encoded in the color.

I don't recall any paper that you quoted unless you mean the Bauer paper.

As to the cross talk, think of the situation differently. The two curves on the bottom are the signals delivered to that point in space from the two speakers. These are the signals that will feed the ear signals, the inputs to the hearing system and not the ear signals themselves. This is in fact exactly the correct way to look at the problem because the ear signals, as correctly noted, will be highly variable and impossible for us to interpret, but exactly what the ear is used to interpreting. The only logical signals to look at are what is being shown.
 
I was more asking what you think the intensity difference needs to be for a working time-intensity trading effect. I've tried speakers with even higher directivity than the Nathan's and there was no trading effect.

It doesn't matter what the ideal is, it matters how well real speakers can do this and how best to set them up to achieve it. The theory says that this trade-off should work and for me and most others it does and it does it very well. Why it fails in your situation is not something that I can explain. Maybe your speakers are broken?
 
Administrator
Joined 2004
Paid Member
Hi Earl, I can help with the screenshots. I use a very good Windows screen capture software that's free. I'm not at home now, but will let you know what it is later today. PNG might be the best format for this.

Have you looked at the CARA software? It's a room placement software that does a lot. It may not do what you want it to, but it's worth looking at to learn what it's doing. What it does not do, is horns. :( But there may be a way to cheat that.

Looking forward to seeing what you've come up with.
 
Hi Pano

You should have read more carefully, the screen capture was solved. A lot easier than I thought. I am familiar with Cara, but it can't use the data that I have for the speakers directivity.

Saw Don Keele yesterday at AXPONA in Chicago. Heard his CBT speakers. Was a little surprised by the 104 dB MaxSPL rating. Seemed pretty low. In the small room it was loud enough, but I do not know how much headroom there would be .
 
Found the paper: Bauer B. B., ”Broadening the Area of Stereophonic Perception”, J. Audio Eng. Soc., Vol. 8, N. 2, 1960, pp. 91-94.

Also, Paul Klipsch made this recommendation back then in a paper or white-paper. My guess is that this technique was common knowledge amongst professionals. I sometimes wonder what other bits of wisdom have been discovered, forgotten, and (sometimes) re-discovered.
 
Administrator
Joined 2004
Paid Member
OK Earl, it did look like you had solved the screen cap problem, I posted "just in case." :)
I understand what you mean about CARA. I would love to be able to import real directivity data into it.

Keele's CBT starts to strain in a bigger room. It probably did not have a lot of headroom past what you heard. That becomes very obvious when you hear it next to Danely's SH-50 in the same space. But his CBT is a small speaker with small drivers. It does a remarkable job for its size.
 
It doesn't matter what the ideal is, it matters how well real speakers can do this and how best to set them up to achieve it. The theory says that this trade-off should work and for me and most others it does and it does it very well. Why it fails in your situation is not something that I can explain. Maybe your speakers are broken?

I've tried with other speakers and it also didn't work. The effect seems to be very fragile and signal-dependent:

attachment.php


From Rodenas et. al., "Derivation of an optimal directivity pattern for sweet spot widening in stereo sound reproduction"
J. Acoust. Soc. Am., Vol. 113, No. 1, January 2003
 

Attachments

  • Screen Shot 2013-03-09 at 17.32.02.png
    Screen Shot 2013-03-09 at 17.32.02.png
    35.2 KB · Views: 717
Also, Paul Klipsch made this recommendation back then in a paper or white-paper. My guess is that this technique was common knowledge amongst professionals. I sometimes wonder what other bits of wisdom have been discovered, forgotten, and (sometimes) re-discovered.

US Patent Nr. 3,759,345 By Borisenko, Sept. 18, 1973 is one of them. What he came up with really looks like it would be effective, but I would guess that for one reason or another never was commercialized.

Basically he proposes the mid-range drivers of a stereo pair of speakers with their radiation axes sharply directed towards the interior of the listening area and parallel channel waveguides to increase SPL roll-off off-axis.

-Pete
 
I've tried with other speakers and it also didn't work. The effect seems to be very fragile and signal-dependent:

From Rodenas et. al., "Derivation of an optimal directivity pattern for sweet spot widening in stereo sound reproduction"
J. Acoust. Soc. Am., Vol. 113, No. 1, January 2003

Not sure that I understand the graphs. Is this for a complete pull of the image to the nearer speaker? Or is this a just detectable pull? It's not clear. I don't have the JASA journals to read.

If its a complete pull to the nearest speaker then it is way off from Blauert. If it is the detectable level then it is completely consistant with Blauert and what I am doing. I have trouble believing that Blauert could be so far off.
 
Last edited:
I would love to be able to import real directivity data into it.

Where would you get that data? Its not something that you just go and look up somewhere. There would need to be a standard format and that doesn't exist (in simple form. There is a complex format for the l;arge modeling programs, but those, and the data sets, are way out of our l;eague here. I am trying to be pragmatic here.)
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.