Jim,
There are several ways to expand the throat area: custom draw the channels to have a wider throat if you want to keep external dimensions the same; increase depth of channel, or grow whole cabinet. Note that some compression is ok, if ratio of throat area to Sd is greater than 75%, it's probably ok. For low Qts, high Bl drivers with low xmax, you might want more compression to load driver and reduce excursion. It should be modeled - a simple model in HornResp with a conical horn for first section to exponential horn near mouth wirh
appropriate dimensions for driver chamber will tell you a lot about excursion of cone.
If you are using the plan from planet10's pdf diagram, I think the the throat width is 0.9 in for the 27.6 in cornu. That is 2.3 cm wide not 17 mm wide. This gives a throat area of about 57 cm^2 for a 5 in deep channel. This about a perfect match for your driver if you wanted no compression. You could probably go as thin as 4 in and be ok.
What are the T/S params for your Altec driver?
Good luck!
Xrk971
Nice work. Did you notice something something pretty significant? The resulting horns closely follow an exponential length/area law. You can model single-spiral (divided 4 ways) Cornu horns in Hornresp using a single exponential section, and the multi-length horns like the one in your post in AkAbak. I'll modify (simplify) my AkAbak model accordingly.
I posted a fibonacci pentagon concept (5 equal horns), i tcould easily become a circle. It needs detailing.
dave
Don,
I have re-spun the cornu generator to make a reasonably sized horn than I can build: 24 in x 3.5 in deep, driver chamber cross sectional area of 148 cm^2, chamber volume of 1312 cm^2, channel lengths of 147 cm and 104 cm long, the throat cross sectional area (both) is 31.3 cm^2 - which will provide a mild level of compression for the TC9FD Sd of 36.4 cm^2. The horn mouth area is 2168 cm^2 I am still doing the bifurcation. See attached plan. I did a simplistic sim in HR for each horn independently and then combined them after the fact to see if the bumps and valleys help cancel out. I still plan to to use the TC9FD with this. I am still unclear how to specify the channel width as function of distance in Akabak for the true cornu. Thanks for trying this in Akabak.
Regards,
Xrk971
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Thanks Xrk971!
All I know about the Altec 405A is what I found on the Altec site--which is nearly useless. And I haven't the tools to measure the T/S parameters. Which is why I want to try a quick, inexpensive, flexible design.
Cheers, Jim
Short of pulling them out this seems to be the only pic I have of them. They were originally used as tweeters in the 'Toolbox' as it is similar to a FAST system.
Don't let my wife see this pic or I'm in trouble. I tell her I always cover the table.
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