Rons Austin A126 for the metric freak newbie - diyAudio
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Old 24th March 2007, 10:45 PM   #1
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Default Rons Austion A126 for the metric freak newbie

Hello all,

This is just a sum up of the information I gathered so far -- mostly from the very kind feedback from Dave and Ron (mostly from this thread: Horn Decision).


All the information here is under the caveat in the subject: Namely I'm a newbie (this is my first speaker build) and I'm just summing up the info avail from more authoritative sources.


1) Building plans

The most up to date building plans for the A126 are avail on Dave's site here: http://www.frugal-horn.com/ronhorns.html.

In that PDF I use the plans on page 3--5 (posted in the full-range.com forum) but with some addded corrections (below).

If I understood it correctly Dave is to redraw the A126 so better plans should be avail soon.

2) Drawings, pictures

I've created a web album at http://picasaweb.google.com/florian....ildingPictures

There are pictures of my 1:1 scale drawing of the horn profile with corrected metric dimensions (in mm). The assumed building material thickness is 18 mm.


3) CC volume.

Based on the above (corrected) plans the CC profile has an area of 10931.5 sq. mm. For a front baffle width of 155 mm that leads to a CC volume of 1.69 liters.

As posted by Dave in the above thread the way to reach the recommended 2.2 liters is to extend the CC by moving backwards the top part of the CC:

Click the image to open in full size.

Based on my calculations if the back of the CC (part 6 in the drawings) is slided backwards for aprox 50 mm the total volume of the CC becomes 2.18 liters.

Also, as noted in the thread above, the addition of the suprabaffle -- and the consequent cutting of a profile in the front baffle -- adds additional extra volume to the CC. Obviously, the exact added volume depends on the type of profile cut in the front baffle. E.g. for a rounded hole with a diam of 112 mm (as in the PDF drawing to hold the driver) the added volume is 0.166 liters.


4) Corrections to the building plans.

Now, this is the trickiest part. The corrections I've made to those plans are only based on my current understanding and I would highly appreciate if someone more knowledgeable (Dave ? Ron ?) could verify that this is OK.

- Corrections to the length of the internal deflectors (better name?) i.e. part 4 and 7 in the building plans. My assumption is that the horn throat width is to be (cuasi) constant at the horn inflections at the bottom of the speaker (part 4) and top of the speaker (part 7). IOW the distance to the different boundaries at those inflections should be cuasi-constant / increase smoothly -- as drawn at page 5 in the PDF.
If this is the case part 4 and part 7 have to be lengthened as 793 mm and 856 mm, respectively:


- Correction to the back of the speaker (part 12 in plans). The length should be increased to 522 mm. The correction is mostly to respect the horn mouth curvature in the plans (center and radius) and the 10 degrees horn expansion angle given for that part.


Click the image to open in full size.

- Corrections to the CC external dimensions on page 4 of the PDF. Some dimensions there are off (by some 4-5 mm).

Click the image to open in full size.

Again, I would be greatful if someone could ack that my assumptions wrt horn inflection and expansion rates are correct.

Best regards,

Florian
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Old 25th March 2007, 03:27 AM   #2
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Florian,

I haven't had a chance to go over you post, but you need to resave those images as gifs (i'll help if needed) -- the jpg noise really kills the clarity of the images.

These look like they will be helpful as i rework the plans.

dave
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Old 25th March 2007, 09:13 PM   #3
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Sure.

Here is the correction for page 3
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File Type: gif correction--page3.gif (34.8 KB, 1295 views)
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Old 25th March 2007, 09:15 PM   #4
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This is the correction for page 4
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File Type: gif correction--page4.gif (12.2 KB, 1183 views)
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Old 25th March 2007, 09:32 PM   #5
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Much clearer... thanx. Now that i have Aiko out of the queue (excuse the OT picture), A126 is the next horn plans for me to tackle between client jobs.

Click the image to open in full size.

dave
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Old 25th March 2007, 09:39 PM   #6
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Now that will be a boon. A good set of plans for the A126 is what the world needs. Oh yes.
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Old 15th April 2007, 07:50 PM   #7
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Default Updated plans, new CC

Well, let's get back some life into this thread. It took me quite some time to get all the stuff together (Dave's drivers got stuck in the customs, the birch ply took extra to deliver, etc).

First, some updates:

- Based on Ron's feedback about the shape of the CC now I've revised my plans again (see this thread: Question about the CC shape in A126)

Unlike Dave's mod, in order to get the required CC volume the CC was expanded by "pushing" at the same rate (i.e. 18 mm, or "one wall thickness") both the top side of the CC and the top sloped part.

The new CC shape and its dimensions (in mm) are detailed in the attached pic

(As above, updated high res pics of the plans + build are at http://picasaweb.google.com/florian....ildingPictures)

Suprisingly enough (or maybe not...) now the A126 CC resembles the CC in the A166 (yes, that was a coincidence, or -- as I like to think -- interpreting correctly Ron's design guidlines).

In the pic one can also notice the original (as per building plans), undersized CC.

Cheers,

Florian
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File Type: jpg a126_cc_resized.jpg (79.3 KB, 1032 views)
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Old 21st April 2007, 08:02 PM   #8
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Default Finally started building

Here is starting building the modifiled CC.

As you can see from the attached pic, newbies can cheat by both using dowels and mixing glue with sawdust to fill in those annoying 0.5 -- 1mm gaps here and there

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File Type: jpg p1060178_(800_x_600).jpg (33.5 KB, 958 views)
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Old 21st April 2007, 08:04 PM   #9
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building up the CC...
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Old 21st April 2007, 08:07 PM   #10
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and the final modified CC, with a 2.1 liters volume.


Again, it now reselbmes the one in the A166 drawing


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File Type: jpg p1060184_(800_x_600).jpg (49.1 KB, 943 views)
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