I have gone through the explanation of paraline lens, where a 2:1 ellipse is used to create a linesource of height equal to the ellipse's major axis.
But I also think that the sudden change of direction of sound waves will also will result in filtering of high frequencies. I suspect this might be the reason why Danley line sources don't go till 20 kHz, while point source synergies do.
1) What parameter of the paraline determines the low pass characteristics?
2) What parameters determine the lowest frequency the lens can be used for?
3) What is the directivity of paraline sound at various frequencies? (Danley's site shows extreme wide dispersion of 120 deg but is I am not sure if this occurs evenly across all frequencies)
@Patrick Bateman @SpeakerScott , if you could be so kind as to...
But I also think that the sudden change of direction of sound waves will also will result in filtering of high frequencies. I suspect this might be the reason why Danley line sources don't go till 20 kHz, while point source synergies do.
1) What parameter of the paraline determines the low pass characteristics?
2) What parameters determine the lowest frequency the lens can be used for?
3) What is the directivity of paraline sound at various frequencies? (Danley's site shows extreme wide dispersion of 120 deg but is I am not sure if this occurs evenly across all frequencies)
@Patrick Bateman @SpeakerScott , if you could be so kind as to...
1) https://patents.google.com/patent/US20120328140A1/en
2) The size of the horn (mouth) that is connected to it, dictates down to which frequency pattern control is retained, together with the desired dispersion angle. A smaller angle requires a larger horn mouth. That is why the Danley SBH10 is so tall (10 degrees vertical dispersion), while it is not wide (140 degrees horizontal). Other than that, low frequencies require large volume displacements, which cannot be shoved through the small orifices of the paraline without turbulence.
3) Along the short side the exit behaves as a diffraction slot, so the dispersion is as wide as you allow it to be. This assumes that the slot is sufficiently narrow. If you connect the paraline to a 120 degrees horn, then the dispersion is 120 degrees. If no horn is connected, the baffle acts as a 180 degrees horn. Along the long side, the dispersion is whatever you design it to be, at least above the frequency mentioned in point (2) above.
Other than that, there are abrupt changes in expansion at (A) the location where paraline and horn meet and (B) the 2x 90 degrees turn within the paraline. Both cause impedance mismatches which cause sound to bounce back as it crosses them. Resonances and and an unpredictable pattern control are the result. I have no idea to what degree this happens. Apparently not at a level to be a problem for pro audio.
There are many ways to turn a point source into a line source. Search for 'line array waveguide' and you will find many. The 'v-dosc' is very similar to a paraline. The line array business is big and all companies do their best to protect their solutions with patents. I think that the paraline is not the best, but it might be the easiest to DIY.
If I remember correctly, the paraline material must also be stiff to avoid absorption at high frequencies. The 2x 90 degrees bends should be smooth.Paraline patent - description [0033] said:
2) The size of the horn (mouth) that is connected to it, dictates down to which frequency pattern control is retained, together with the desired dispersion angle. A smaller angle requires a larger horn mouth. That is why the Danley SBH10 is so tall (10 degrees vertical dispersion), while it is not wide (140 degrees horizontal). Other than that, low frequencies require large volume displacements, which cannot be shoved through the small orifices of the paraline without turbulence.
3) Along the short side the exit behaves as a diffraction slot, so the dispersion is as wide as you allow it to be. This assumes that the slot is sufficiently narrow. If you connect the paraline to a 120 degrees horn, then the dispersion is 120 degrees. If no horn is connected, the baffle acts as a 180 degrees horn. Along the long side, the dispersion is whatever you design it to be, at least above the frequency mentioned in point (2) above.
Other than that, there are abrupt changes in expansion at (A) the location where paraline and horn meet and (B) the 2x 90 degrees turn within the paraline. Both cause impedance mismatches which cause sound to bounce back as it crosses them. Resonances and and an unpredictable pattern control are the result. I have no idea to what degree this happens. Apparently not at a level to be a problem for pro audio.
There are many ways to turn a point source into a line source. Search for 'line array waveguide' and you will find many. The 'v-dosc' is very similar to a paraline. The line array business is big and all companies do their best to protect their solutions with patents. I think that the paraline is not the best, but it might be the easiest to DIY.
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2) The driver's parameters and excursion limit the LF response, the Paraline itself has no frequency limit.
That said, the lens can be considered to be short horn with a small mouth.
3) An example:
The top trace shows the equalized response of a single one of my 2008 2x8"/EVDH1MT Paraline.
The raw response of the HF section only (not shown) is +/- 6dB 200Hz to 16kHz.
Top traces are with 1.5Hz resolution, the rest use 1/24 octave resolution (Fixed Point Per Octave, FPPO) with a smoothing of "9". The traces are in listed in degrees off axis.
The 90 degree horizontal response is quite even, other than a narrow region centered around 1250 Hz, perhaps due to the 9.75" interior height of the horns parallel walls.
Vertical polars of this non-divergent Paraline drop from near 90 degree at 1000 Hz to around 10 degrees at 16,000 Hz. The VHF vertical pattern is so narrow I took the polars twice, after realizing the mic, at six feet away was about 2.5" off from dead center, causing a 3 dB drop at 16kHz.
Paralines can be designed for a more divergent HF pattern, the Yorkville Synergy series SA102 and SA115s are examples.
https://www.diyaudio.com/community/threads/yorkville-synergy-series-sa102.378449/
Art
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What in your opinion is the best line source solution?
Please help me understand why a line source's vertical pattern is narrow. By definition, it's line source and at least at the middle of the line source, directivity ought to be even isn't it?
@weltersys and @TBTL ,
1) How large or small can be the ellipse minor axis for , say, a 1" exit of a compression driver?
2) What are the allowable largest and smallest dimensions of the exit slot?
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1) The exit diameter of the compression driver would determine the minimum minor axis dimension.
There is no upper dimension limit for the ellipse minor axis, and it is independent of driver dimensions.
Practically speaking, dimensions are determined by output requirements. Fitting more drivers into a box to achieve more output requires shorter vertical dimensions.
For home use, a single driver could potentially provide enough output to drive a floor to ceiling Paraline.
2)The exit slot's vertical dimensions are virtually unlimited. The width determines the high frequency diffraction limit without (too much) destructive interference.
For 20kHz, the width should be no wider than about 17mm, 0.7 inch.
16kHz, 21.5mm, 0.85 inch.