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: http://www.diyaudio.com/forums/showthread.php?s=&threadid=96999).
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.otel/A126HornBuildingPictures
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:
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.
- Corrections to the CC external dimensions on page 4 of the PDF. Some dimensions there are off (by some 4-5 mm).
Again, I would be greatful if someone could ack that my assumptions wrt horn inflection and expansion rates are correct.
Best regards,
Florian
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: http://www.diyaudio.com/forums/showthread.php?s=&threadid=96999).
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.otel/A126HornBuildingPictures
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:
An externally hosted image should be here but it was not working when we last tested it.
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.
An externally hosted image should be here but it was not working when we last tested it.
- Corrections to the CC external dimensions on page 4 of the PDF. Some dimensions there are off (by some 4-5 mm).
An externally hosted image should be here but it was not working when we last tested it.
Again, I would be greatful if someone could ack that my assumptions wrt horn inflection and expansion rates are correct.
Best regards,
Florian
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: http://www.diyaudio.com/forums/showthread.php?s=&threadid=99769)
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.otel/A126HornBuildingPictures)
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
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: http://www.diyaudio.com/forums/showthread.php?s=&threadid=99769)
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.otel/A126HornBuildingPictures)
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
Attachments
You could try this to make the turns..... I used an epoxy mortar (1 part epoxy: 1 part sand mix) , followed by body putty to smooth out the surface. The epoxy mortar allows the application of lifts up to an inch and one half , but as it begins to set up, it becomes difficult to smooth as seen in the first photo. If you don't need big lifts, less sand makes smoother applications. The body putty (polyester resin for auto repair) smooths it over and allows adjustments in the dimensions. It would be good to make a template of the turn to place in the open end. Much easier than using a rasp. later on.....Also, if you need to use a rasp or sand paper, there is a certain moment , in the curing, where the removal of material is relatively easy to manage.
Attachments
Thanks for sharing....
Still, I'm not so sure about treatment of the horn folds...IIRC ron's attitude towards folds treatment was not so favorable.
Yet still, it may very well be that rounding the corners with some sort of mortar is beneficial.
The only question is of doing that via lining with cloth or rounding it up with mortar. Or both ?
Ron ? Dave ?
Thanks again for posting the pics. Highly appreciated.
Still, I'm not so sure about treatment of the horn folds...IIRC ron's attitude towards folds treatment was not so favorable.
Yet still, it may very well be that rounding the corners with some sort of mortar is beneficial.
The only question is of doing that via lining with cloth or rounding it up with mortar. Or both ?
Ron ? Dave ?
Thanks again for posting the pics. Highly appreciated.
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