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In Reply to: RE: Do I need tweeters ta all? posted by Gandra1 on October 16, 2010 at 08:25:10
My ears are 31, and I get by fine without tweeters. When you look at the graph, keep in mind that what you see at 10K and 3.5K are humps/resonances in the response (that I think are less audible a little off axis). Compare 15K more to 6-7K (as a baseline), and you'll realize that extend fairly high. I think you actually get more extension than some big popular soft domes.
IME, most fullranger folks that use high frequency help do so as much to broaden the dispersion up high as to extend the absolute response (when it comes down to it, not a great deal happens above 15Khz). "Add some sparkle" if you will. Many also seem to enjoy the "phase-y" sound you get when a super tweeter is spaced well away from the fullrange driver. I don't dislike the addition of super tweeters, but I am perfectly happy without them. If you decide you need them, there are fairly inexpensive options.
Now, what enclosure are you thinking of? You know that the box needs to be perfectly tailored to the driver, and computer simulation has allowed "t-line" design to progress considerably in the last few years. I attached a pic of and link (sorry, its another forum, but it is the only place I have it posted) to a t-line/tqwt sort of thing for the BetsyK. I'd be happy to talk more ideal boxes and the need for tweeters anytime you want.
Paul
www.wildburroaudio.com
Follow Ups:
Generic T-line - the size was determining factor.
Did you run any computer models? How did you arrive at the dimensions? That isn't much box volume for the BetsyK. Is the path the same depth in each fold, or does it contract? Do you know the path cross sectional area and length off hand? I could toss the numbers into Horn Response for you to get some idea of how it will behave.
Paul
The "pipes" are uniformly 3.5". Th bends will have ceramic tiles, at the 45°, and spaces filled with concrete. The length of 11+' will be filed with the acoustic foam.
The instructions? From the vintage Vivian Capel's book "Loudspeaker design." T-line for the full range driver(s) with the similar spec's to his, in his example.
I plugged it into Horn Response, which isn't the perfect tool for such a thing. But, I think I can interpret the results well enough. My biggest worry is the giant suckout at 100hz. I think a great deal will depend on stuffing. Were I you, I'd rig a way to listen to it without attaching the final side. Thick weatherstrip and clamps. Then play with stuffing: density and placement.
You probably won't like this idea, but I'd also skip the tile and concrete. First, you need all the box volume you can get. Second, those corners will help to keep midrange frequencies from traveling down the line, which in my mind is quite desirable. You don't want midrange coming out of the terminus if you can avoid it. The bass that you are trying to reinforce with the line won't care a bit about the reflectors. The wavelengths we're talking about are too long to be affected either way, so better to have volume and midrange filtering. At the very least don't worry about the tile until you've made certain that the box will suit your needs (by clamping a side on and listening).
Finally, let me know your results! I sure would appreciate some pics over on my forum. And if this little box works well, I bet others will be interested in duplicating it.
Paul
Thanks Paul, I sure will keep you posted about the findings - I am relieved I wont have to use concrete and tiles. :)
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