New White Paper posting

[skeptic43]

Originally Posted by arend-jan

I'd like to create directivity plots like that for my own measurements. Any software out there that can do it?

More to the point: How did Mr. Geddes create those graphics? Don't recall seeing it explained in the white paper.

[MethMan]

Originally Posted by arend-jan

i'd like to create directivity plots like that for my own measurements. Any software out there that can do it?

arta

[gedlee]

Originally Posted by arend-jan

I'd like to create directivity plots like that for my own measurements. Any software out there that can do it?

My software is commercial, called Sigma-Plot, but publication quality graphics software like this is very expensive.

If you can send me the data in the correct format, I will plot it as along as I can post it as well. I'd like to create a library of real polar data measurements. But I don't want to have to clean up data and reformat it etc. It has to be in the exact format that I need.

Three *.txt files:

1) list of frequencies (suggest no more than 512 points)
2) list of angles (suggest every 7.5 degrees)
3) data of angles seperated by comma's with all angle data on one line

I can then plot this in exactly the same form as I show in the paper.

The data should be smoothed in frequency, but not more than 1/3 octave, but 1/10-1/6 works best. Unsmoothed data makes a messy plot because of the random noise in the data.

[gedlee]

Originally Posted by MethMan

arta

Will ARTA do that kind of resolution? Many of these programs don't do interpolation, but Sigma-plot does. And it does a good job. Some others that I have tried have not been very good.

[arend-jan]

thanks for the offer Earl, much appreciated. I'll be out of the country for the next three weeks, but after that I'd like to take you up on that offer.

[gedlee]

Originally Posted by arend-jan

thanks for the offer Earl, much appreciated. I'll be out of the country for the next three weeks, but after that I'd like to take you up on that offer.

I'd love to see a library of designs. That way, with real data at hand, we can get to what really matters and stop all this hand waving and guessing about audio performance. I just don;t have the resources to do any more than I have already done.

[MethMan]

Originally Posted by gedlee

Will ARTA do that kind of resolution? Many of these programs don't do interpolation, but Sigma-plot does. And it does a good job. Some others that I have tried have not been very good.

(It is a 250k tiff file. 1.6Mb bitmap file on request)

[gedlee]

Thats not bad. Certainly cheaper than SigmaPlot. Are the scales arbitrary? -90 > 90, 0dB > -36 dB?

Is this data available? I'd love to add this example to the paper if I could get the data set. And I'd like to compare my plotting with this.

Do you have any more?

[MethMan]

Not exactly. Angles are arbitrary (depends only on measurement angles done, up to 360deg). But, amplitude iso-contours seems to be fixed on 1/10 of range. OTOH Color palette can be "jet" (as it is) or B-W, contoured or none. Range is up to 40dB, IIRC.
Data is available, but this is first atempt of xo for my budget surround speaker. I can send them. If you want final version, you have to wait because I am short of coils.

[Key]

Hey Earl,
I like the paper. I think you have some good stuff in there. Some of it that you touched on I would be more tempted to make the whole paper about but that's just what I am fixated on I guess. This point kind of stuck out to me as something I don't think works.

"Recall now our discussion of image shift in a stereo situation where we
hypothesized that if the farther speaker could get louder as one moved
laterally while the closer speakers level decreased, that we might be able
to offset the time delay differences and maintain a fairly stable image
with listening position."

Thats a big "might". You can compensate with a delay for one side of the room but then you compromise the center and opposite side of the room. And I am pretty sure the delay (arrival time) is more important than the volume in terms of what will effect the stereo image. Also subjective reviews on other polar patterns than your own are very similar in this respect. Basically a report of a lack of shifting compared to the average loudspeaker. I am not sure it is exclusive to your design perceptually. I see why you could think that it is based on that physical alignment though. And yeah you could be right and that this sort of directivity is self compensating when moving around a room to a certain extent. I guess I just suspect there is something else going on.