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Old 15th June 2012, 07:38 AM   #2711
blo06 is offline blo06  France
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Quote:
Originally Posted by David McBean View Post
Hi Dan,

Making throat sound pressure data available is about as far as I am prepared to go :-). Diaphragm peak velocity and acceleration values are included in the diaphragm displacement chart sample results.

Kind regards,

David
oh yes !! with a nice diagram ?

Cheers.
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Old 15th June 2012, 04:30 PM   #2712
epa is offline epa  Netherlands
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Quote:
Originally Posted by mwmkravchenko View Post
Hey throat pressure is your friend. Very useful when designing near the bleeding edge of efficiency.
question about compression ratios.
what is a reasonable throat pressure for a mid driver.
in my model i have a 5:1 compresion ratio .throat pressure is 4500 pascal at p-max.
is this resonable for a mid pa horn?
are there other considerations?
Click the image to open in full size.
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Old 15th June 2012, 07:37 PM   #2713
Mark Kravchenko
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I'll look when I get to a computer. I can't run hornresp off a Samsung Note.
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Old 15th June 2012, 07:59 PM   #2714
GM is offline GM  United States
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Quote:
Originally Posted by epa View Post
what is a reasonable throat pressure for a mid driver.
in my model i have a 5:1 compresion ratio .throat pressure is 4500 pascal at p-max.
Seems like a lot for a paper diaphragm, but may be OK for other materials: Pascals to Pound-Forces/Square Inch Conversion Calculator

GM
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Old 15th June 2012, 08:34 PM   #2715
epa is offline epa  Netherlands
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hi gm
on this side of the pond whe use metric system
does it make a difference when the mid is crossed @150hz before the horn unloads and excursion go's up?
btw,@ p-max its "only" 3600pascal
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Last edited by epa; 15th June 2012 at 08:39 PM.
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Old 15th June 2012, 09:52 PM   #2716
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Default Yes!

Quote:
Originally Posted by epa View Post
question about compression ratios.
what is a reasonable throat pressure for a mid driver.
in my model i have a 5:1 compresion ratio .throat pressure is 4500 pascal at p-max.
is this resonable for a mid pa horn?
are there other considerations?
Click the image to open in full size.
For design of a midrange compression driver the following references constitute mandatory reading. These will lead you to others that are recent and helpful as well. A phase plug should be used to form the front compression chamber.
The compression ratio of [Sd]/[St] = 5 is a good starting point. Note that [St] is the total area of the phase plug slits, not the area of the horn throat that will be larger.

Regards,

WHG

Community Light & Sound M4 Driver

[1] A White paper covering the M4 and some notable installations:
http://www.communitypro.com/files/li...PAPER_TECH.pdf

[2] An AES article by Bruce Howze and Clifford Henricksen is available here.
AES E-Library A High-Efficiency, One-Decade Midrange Loudspeaker

[3] Technical Notes Volume 1, Number 30
Cone Midrange Compression Drivers (CMCD)
http://www.jblpro.com/catalog/suppor...=201&doctype=3
Phase Plug Design (Smith)

[4] File: ASAJ025-0305.pdf
Date: Mar-53
Title: An Investigation of the Air Chamber of Horn Type Loudspeakers
Author: Bob H. Smith
Publication: ASA-J, Vol. 25, No. 2, Pg. 305, Mar-1953
Affiliation: Division of Electrical Engineering, University of California
URL: Cookies Required
Abstract (1): The front air chamber design is treated as a boundary value problem which yields a solution of the wave equation for the general case in which the horn throat enters the air chamber in a circumferentially symmetrical manner.
Abstract (2): The following specific cases are analyzed: (1) the case in which the horn throat enters the air chamber by means of a single orifice, (2) the horn throat enters the air chamber by means of a single annulus of radius [r] and width [w], and (3) the horn throat enters the air chamber in [m] annuli of radii [r1],[r2],...[rm] and widths [w1],[w2],...[wm].
Abstract (3): The analysis reveals that the radial perturbations caused by the horn throat excites higher order modes. At the resonant frequencies of these modes the horn throat pressure becomes zero and the loudspeaker does not radiate. By suitable choice of annulus radii and widths the first [m] modes may be suppressed and the corresponding nulls in the output pressure eliminated.

[5] File: AESP1384.pdf
Date: Nov-78
Title: An Application of Bob Smith's Phasing Plug
Author: F. M. Murray
Affiliation: Jamse B. Lansing Sound, Inc., Northridge, CA
Publication: AES-P, No. 1384, Cnv. 61 (Nov-1978)
URL: http://www.aes.org/e-lib/browse.cfm?elib=2970
e-Library:
Abstract: The war of the phasing plugs still rages after more than 25 years. Compression driver phasing plugs have vacillated between annular rings, salt shakers, teardrops, and now radial slots again. When Bob Smith provided simple design criteria for optimization of the annular ring type, little did he realize how studiously he would be ignored.
Abstract: His design is now incorporated into a large compression driver capable of operating to the high frequencies where this design is important

Last edited by whgeiger; 15th June 2012 at 09:58 PM. Reason: correct AES URL
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Old 16th June 2012, 07:21 AM   #2717
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Quote:
Originally Posted by blo06 View Post
oh yes !! with a nice diagram ?
Hi blo06,

I have no plans to add charts showing diaphragm velocity and/or acceleration - values can however be sampled at user-specified frequencies.

The throat sound pressure chart is displayed by selecting Tools > Sound Pressure from the SPL Response window - see attached screenprint.

Kind regards,

David
Attached Images
File Type: png Pressure.png (74.0 KB, 194 views)
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Old 16th June 2012, 09:10 AM   #2718
epa is offline epa  Netherlands
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Quote:
Originally Posted by whgeiger View Post
For design of a midrange compression driver the following references constitute mandatory reading.
tnx
i gues i wil be reading for the rest of the day
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Old 16th June 2012, 11:50 AM   #2719
AndrewT is offline AndrewT  Scotland
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I grew up with pounds/square inch (lb/in˛)
and half converted to Newtons/square mm (N/mm˛) in my professional career.
But Pascals have never been "natural" for me.
Would I be admitting to being lazy by asking for an easy way to "understand" or get a feel for what Pascals means in everyday terms?

Yes, I am lazy, I am asking for an easy way into Pascals.
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Old 16th June 2012, 11:58 AM   #2720
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by whgeiger View Post
For design of a midrange compression driver the following references constitute mandatory reading.
I can gain read access to only two of the papers.
Is there a way to read any of the others? Without paying the AES for papers contributed by their Members !
Quote:
I guess I will be reading for the rest of the day
Probably not.
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