George Roland Posted July 2, 2007 Share Posted July 2, 2007 I reference this to Altec 290-16Ks that I have just acquired, but these are pretty "generic" questions.In looking over Altec's info sheet on multicellular horns, I see that there are "horns", "throats" and "adapters". For example, the 1505B horn is shown connected to one Y-shaped 30172 throat and two 30546 adapters and 290 drivers.The next page is a multi-part diagram showing throats, adapters and drivers that can be assembled along with gasket specifications, horn dimensions, etc.If I am reading this correctly, the 290 driver, in a single driver configuration, is shown needing to be connected to a 30162, 30210 or 30166 throat.What would determine which of these throats one would choose?These three throats vary in depth from 4 1/2" to 7 1/2". Doesn't this effectively lengthen the horn? Does this not matter to the sound quality? Is the hole through this throat tapered like a horn or is it a pure cylindar?Another issue is that I see the horns recommended for the 288, 290 and 730 drivers referred to as being for "1.4 inch" drivers. To what "1.4 inch" does this refer? My 290's voice coil is ca. 2.8" in diam. and the opening of the screened section where the sound emerges is ca. 1 1/16" in diameter. It is nowhere near 1.4inch, which would be almost an inch and a half.Third question: if I wanted to make a 300Hz wooden tractrix horn for my 290, how would I know what the size and shape of the opening at the driver end of the horn should be? What about a throat?Many thanks, George Quote Link to comment Share on other sites More sharing options...
jorjen Posted July 2, 2007 Share Posted July 2, 2007 George.....check your other horn thread. Quote Link to comment Share on other sites More sharing options...
djk Posted July 2, 2007 Share Posted July 2, 2007 Its pretty simple really. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> The exit of the driver where it bolts up with a horn and/or throat adaptor is 1.4, and there is a rubber gasket that fits in a step milled into the driver. If you didnt get this gasket when you bought your drivers, you can order them from Great Plains Audio. The 45* 30546 adaptor is only for use outside, you dont need it. The 311-60/90, 511-E, and MR II series horns have a 1.4 entry and do not require a throat. The multi-cells and bigger MR series horns require an application specific throat for each model. When making a rectangular horn figure the entry to be a 1.4 square. The driver mounting plate should have a 1.4 round entry and a 1.4 square exit. The thickness of this piece should match either the taper rate of the throat stub inside the driver, or the taper rate of your horn. The taper rate inside the driver is about 200hz, ie: the area doubles about every 4 inches. The area of a 1.4 hole is 1.5386in^2, a 1.4 square is 1.96in^2, or roughly a 27% increase in area. A 1 thick board would work well, a ¾ would be OK if the horn taper rate is 280hz or higher. I would use something easy to work with like basswood. Use a round rasp to smoothly contour the 1.4 hole to the 1.4 square. Since youre using a tweeter, this transition is not critical like it would be on a wide-band driver like the 288. Quote Link to comment Share on other sites More sharing options...
George Roland Posted July 3, 2007 Author Share Posted July 3, 2007 djk, Thank you for this detailed explanation. It is very helpful. George Quote Link to comment Share on other sites More sharing options...
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