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caladois
04-26-2008, 12:44 PM
I just buy a pair of H5038. I really liked a compact system. Is there any chance to find the data sheet of this horn (curve and directivity) ?http://nsm01.casimages.com/img/2008/04/26//mini_080426072103264121995245.jpg (http://www.casimages.com/img.php?i=080426072103264121995245.jpg)

I was thinking of a two way system : JBL E145 and a JBL 2450. Am I realist ?

Earl K
04-26-2008, 01:31 PM
Hi Stephane,


I just buy a pair of H5038. I really liked a compact system. Is there any chance to find the data sheet of this horn (curve and directivity) ?

I was thinking of a two way system : JBL E145 and a JBL 2450. Am I realist ?

- I don't believe JBL ever published a separate "cut-sheet" for this horn . Someone like subwoof would know better than I if one was offered by JBL.

- This horns' 6 db down pattern is listed as 60° x 30° ( H x V ) in various "Pro" catalogues.

- They are a nice pure sounding horn / with quite high "Q" / & in my mind , they form the basis for original wave-guide school of curves ( I do own a pair of these H5038s ).

- Like a lot of so-called JBL wave-guides, they do have some measurable beaming .
- What's beaming ( well, IME & by my defination ) ? 1.5 db gradient steps of HF level change ( increase or decrease ) per 10° axial movement per some arbitrary frequency shift .

- For home usage, I'd recommend adding ( around the mouth area ) foam termination "lips" ( to mitigate the development of destructive diffraction effects / due to the almost 90° hard-edge termination at bell to flange ).
- With these foam snubbers in place, you'll be able to realize the potential for better imaging that these horns offer the owner .

- Yes, you can make something that sounds really nice with the component you've mentioned / especially if you swap a pair of 2450SL diaphragms into those drivers and "charge-couple" a custom HF contour circuit ( really just a series LCR placed across the drivers' terminals / after the parallel RC filter that's in series on the + side that provides the HF bypass ) .
- Study all the EverestOne ( E1) info for insights into how best to achieve maximum bass extension from a E145 woofer.

:)

ps ; track down the .pdf cut sheet for the 18sound elliptical horn/waveguide to get an insight into how the coverage pattern works ( or beams ) .

ahhh, here it is ;

caladois
04-26-2008, 03:01 PM
Thanks for reply. It is quiet amazing that JBL did not wrote a paper on this profile !

Hoerninger
04-26-2008, 03:14 PM
... (curve and directivity) ...

My investigations show the following geometrical curvatures:

Mouth diameter 2 inches (0,0508 m)
Horn length 0,3 m
two curvatures obtaining an elliptical mouth
with radius ya and radius yb by length x.

Frequency limits regarding the two curvatures 175 Hz and 289 Hz,
frequency limit regarding the mouth area 602 Hz
____________
Peter

Earl K
04-27-2008, 10:06 AM
Hi Peter,



- Frequency limits regarding the two curvatures 175 Hz and 289 Hz,
- Frequency limit regarding the mouth area 602 Hz

Thanks for those calculations . They are interesting .

Do you have another formula ( waiting in the wings ) that will average the three to help determine a low frequency loading limit ( or F3 ) for this horn ?

:)

caladois
04-27-2008, 10:15 AM
A few cleaning , and some different test with an older driver. I will start around 600hz. I can(t imagine this horn lower to 500hz as in Paragon ...http://nsm01.casimages.com/img/2008/04/27//mini_080427071022264121999053.jpg (http://www.casimages.com/img.php?i=080427071022264121999053.jpg)
The 2450 is supposed to have a larger frequency range.

Hoerninger
04-27-2008, 11:33 AM
Hi Earl,
... waiting in the wings ... (I had to look up for this expression first.)

I do not think so, my mathematical tools are straight forward and are placed in this forum (http://www.audioheritage.org/vbulletin/showpost.php?p=186821&postcount=1). The horn is simply too short, the little opening angles against the middle axis show this as well.

When I was thinking about an improved Paragon (not Paragon XXL;) ) I changed the smaller diameter of the H5038 mouth from about 13,3 cm to 50 cm and let the other one (nearly) unchanged with 25 cm (ratio 2:1). The horizontal dispersion is unaffected.

Due to the two different flare rates along the diameters of the ellipse the cut off frequencies are 290 Hz and 415 Hz. The cut off frequency calculated due to the mouth area, which is ernestly valid only for a circular mouth, is 309 Hz - just between the other two. The angles of the tangents against the middle axis are 62 degree and 34 degree, the desirable 45 degree is in between.

These calculations please me more than those from the original horn. It might be well sounding. Consider the length is the same compared to the H5038.
(But I do not know how to make a neat shape as DIY.)
____________
Peter

yggdrasil
04-27-2008, 03:58 PM
But I do not know how to make a neat shape as DIY.
____________
Peter

You could cutout the elipses on a large amount of wafers (wood boards), with the cutout calculated according to the wafer's distance from the throat. After glueing and drying a few wafer's you would have to sand the horn to get rid of irregularities caused by e.g. the vertical saw blade.

A lot of work, but the results could be just excellent.