The naked cells models I've seen have all been identical cells. I could not tell with the few tar-filled I've seen.
All cells on the 1803 are true and plumb. All terminate on the same radius curve as the front, making the center of the diaphragm the focal point, so once the sound leaves the waveguide it travels equal distance to enter all cells.
That's not right. The focal point is just behind the mounting flange, inside the waveguide, about an inch or so.
Stepping into the middle of this conversation here are a few of my thoughts, Determining the length and final mouth size should be the easiest part of this equation. Whether it is a single cell horn or a 16-cell multicell the mathematics will be the same. As long as you are following the model of the equal cells you just divide the cross-sectional area at any point by the number of cells.Where is it written in stone that the cell need to be rectangular or squared in shape? Remember that when they made the original Altec Multi-cell horns that there was a limit to what materials they had to work with. This also limited what they did with the cross-sectional shape changes. There are many other ways that the shape change can happen and inner and outer cells can be different in cross-sectional change while the overall expansion rate of combined cell area is identical for the final cutoff frequency.
Nowhere. I've often thought about hex cells, like a honey comb, or a combination of shapes, like the skin of a football. (soccer).
Attachments
LOL, then it would want paying to play music - even then it would do it badly....... unless it was made in South or Latin America
Just to make sure I'm with you, you mean in a triple row horn the edge to edge measurement on the central set of cells is wider than the same measurement taken along the top or bottom of the horn because of the curve?
I'm sure its not but there is a book called 'JRKO is a moron and 4 sides is already making his nose bleed' 😉
An there goes my nose bleed again 😀
Does axial length mean the distance between centres, from throat to mouth? I get the mouth area (in the 1005's case 6.25"x6.25"=39.0625") and maybe axial length (15" for the 1005) Is it throat area that I then need then to calculate the flare?
Thanks for all the effort into this guys - once I've got my brain round it I'll be glueing my fingers together in a flash!!
Yes but this applies to two rows as well. Note that some connections at the mouth of the cells are 'fat', some are 'tapered' and some are 'skinny'.
So in any horn of this type, the center will be wider than the lower rows independant of the number of rows.
Correct. I found my old expo spreadsheet, so post the mouth, throat, axial length of the various horns or input them into HR or similar.
GM
Absolutely! Back in the '60s I designed slot car parts for awhile and we had this huge, old plastic molding machine, but for all its size it couldn't make parts much bigger than a motor end bell, but I had audio wet dreams about a house size one that could mold massive multi-cells made from Delrin with 64 or more cells starting with ~0.2" diameter throats.
GM
GM,
What is your idea behind so many cells? How wide a dispersion pattern are you trying to produce?
Slot cars now that is going back. I had some myself and went to my local track to run the cars. I'm curious why you would think to use Delron for a horn lens, wouldn't be my first choice for a material. And attaching the multiple cells together would be a real bear. It isn't a very stiff material but is high density for a plastic.
What is your idea behind so many cells? How wide a dispersion pattern are you trying to produce?
Slot cars now that is going back. I had some myself and went to my local track to run the cars. I'm curious why you would think to use Delron for a horn lens, wouldn't be my first choice for a material. And attaching the multiple cells together would be a real bear. It isn't a very stiff material but is high density for a plastic.
x = axial length distance from throat where area doubles.
0.75" square throat:
length 15.496
multiplier 6.117
length (x) 2.533
k 0.274
Am 39.063
At 0.563
Fc 295.00
SoS 13,548.00
1" square throat:
length 15.498
multiplier 5.288
length (x) 2.931
k 0.237
Am 39.063
At 1.000
Fc 255.00
SoS 13,548.00
I just found out that converting/inputting the areas and length into HR displays Fc in the F12 window [though insignificantly different due to conversion, different SoS than the one Altec listed] and allows one to choose axial length 'x' when exporting the design data, saving one from oddball fractions, so seems the easiest way overall to get all the layout particulars.
GM
Hopefully improving a multi-cell’s overall performance and particularly its HF response over existing designs.
??? Wasn't trying for any particular polar response per se, just that starting with a smaller throat yields a smaller mouth for a given axial length, so it takes more cells to get ~ the same polar response, throat, mouth area as an 1803/whatever.
Again, it was just a 'pipe' dream of a ~20 yr old whose manufacturing, materials knowledge was pretty much limited to what he had learned to that point from hot rodding motorcycles, cars along with a several year stint working in an intense design engineering environment that covered architectural, structural, mechanical and topography, which taught him enough to help design all aspects of slot car parts/assembly; so naturally he would have fantasized a horn molded as a single piece [not individual parts] using a material he had some ‘hands on’ knowledge of.
Delrin had already been proven a suitable material for injection molding of motor end bells and spur gears due to its damping ability over a wide HF BW while maintaining sufficient rigidity, heat resistance at a low weight and didn’t audibly ‘ring’ in my rather crude testing, so seemed a good enough material.
I guess I could have gone 'over the top' by fantasizing using Bakelite, though being just a ‘pipe' dream, I didn't waste my time giving any real thought to any design details as it seemed much too far-fetched/expensive a venture in my rather creatively challenged mind to ever become a reality.
Since this is apparently more your area of expertise, what material would you have specified circa 1967 [and today] for a one piece molding of a multi-cell to cover the 300-20+ kHz BW?
GM
Why oh why am I so freaking stoopid?!
GM I thank you in blind faith for the post below on the two throat variations. Unfortunatly I'm an idiot and despite looking thru the HR help section I dont get most of the info you've posted.
I'll have a glass of wine and then try using HR itself to see if I can make it squawk
James
GM I thank you in blind faith for the post below on the two throat variations. Unfortunatly I'm an idiot and despite looking thru the HR help section I dont get most of the info you've posted.
I'll have a glass of wine and then try using HR itself to see if I can make it squawk
James
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