1803B horn plans available?

**Cal Weldon** · February 1st, 2013, 06:58 PM

I wonder if Alan used the measures before I corrected it this morning. You remember I had trouble with "was that 3/8 or 5/8" last night? Maybe he can check that because it was right at number 4 where the correction was made, so...

I'm not a bettin' man but...

**Cal Weldon** · February 1st, 2013, 07:02 PM

Here is the scan of the waveguide. Notice the taper down (compression) on the side view.

EDIT: Site won't let me upload it, sorry.

**Cal Weldon** · February 1st, 2013, 07:19 PM

Here a pdf of the waveguide ID measurements. You can see there is no exponential curve as might have been expected.

I look at the numbers and I think something is strange around the 2" mark. It seems to open quickly and the even out. I don't remember seeing that. I will have to recheck. I am guessing because it was so far down the mouth that I measured it at the wrong spot or more likely, the measure at the 1" mark was wrong.

The slight compression in the side view does not occur on the top view.

**VolvoHeretic** · February 1st, 2013, 11:08 PM

If you made a template out of thin poster board, rough cut it to the outside shape of the horn cell and filled in the voids with masking tape, re-cut, and re-taped, you would wind up with an exact profile of the horn curve. Next, take a good straight on picture of the template with a tape measure laying next to the pattern, post it, and I can scale it in AutoCAD and repost an exact, one to one scale PDF that anyone can printout and use for their pattern.

Edit; What would be even better is if you could use paper, and make a pattern of the inside of the cell wall following the curve (the floor of the cell). It’s all trial and error, but you should be able to come up with a very accurate curved pattern of paper you could lay on a flat piece of plywood, which when cut and then curved would have the finished compound curve and shape you need.

**alancohen** · February 2nd, 2013, 12:07 AM

Originally Posted by Audiomind

I am assuming you are referring to the fact your line on the graph is a little longer than the 24.5" inches the cell should be?

No, I meant that the vertical and horizontal axis have to be in scale to be correct. Excel just prints numbers. The distance between 1 and 2 on the horizontal needs to be the same as 1 to 2 on the vertical. I don't know how to make Excel do this.

**Panomaniac** · February 2nd, 2013, 12:17 AM

I posted the 1005 profile over on diyAudio. When I ran an exponential horn in Hornresp, it came out the same has the 1005 segments. I don't think there is any magic to it.
EDIT. Here is what I measured:
And Now For Something REALLY BIG - Page 70 - diyAudio
and here is what I calculated
And Now For Something REALLY BIG - Page 72 - diyAudio
and a photo
And Now For Something REALLY BIG - Page 65 - diyAudio

**VolvoHeretic** · February 3rd, 2013, 05:57 PM

I am not a member of diyAudio, so can't open the files. If you took a picture perpendicular of an outside view of a horn cell by placing your camera as far away as you can get and zooming in (to minimize distortion) along with a tape measurer for scale, I could calculate the profile and along with the paper template of the cell wall you could come up with a very accurate template to start carving on some wood with. I do this all of the time for forensic engineering work whenever any buildings falls down, except usually the dorks taking the photos, shoot them from some stupid artsy angle which makes my job miserable.

The template of the cell wall following the flare curve could just as well be made following the outside of the cell.

**Altec Best** · February 3rd, 2013, 07:35 PM

Originally Posted by Cal Weldon

Just had a nice long chat with Audiomind. Sounds like the project is a go. Can't wait to see pics of the progress. I'll have to go home now to see if I have some inside callipers to measure the inside of the waveguide.

Hey Cal you would probably need some kind of calipers like this..

Inside Calipers Large No Name Inside Calipers Opens to 24" | eBay

**Altec Best** · February 3rd, 2013, 07:46 PM

Originally Posted by alancohen

Speaking of "inside the waveguide", if I make a multicell horn I'll be using my 802G drivers. I assume all Altec multicells were made for large format CDs. How does this affect me?

Alan you will need a 21216 adapter.

altec 21216 adapter | eBay