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70.21.126.31
hey all--
i've been working with a 2 way system for a while honing my crossover-- now that i'm feeling pretty confident about it-- i'm going to start the final frontier of adding in a supertweeter.
for now-- i'm thinking of using something like a fostex ft17, the 100ht, ft 96, possibly the eminence apt series, or the selenium st 300.
not looking for world busting performance-- mostly a view into their possibilities, and some practical experience putting it all together.
any ideas as to something which doesn't have to be perfect (but hopefully not sonically horrible)- with the specs of:
not to go too far beyond 20k (most of the fostexes are out..)
efficiency of at least 99-100db.
prefer the diaphragm NOT be titanium.
i'd really like at least an 80 degree dispersion..
oh yeah.. 8 ohm, preferable.
the rest of the system is altec 414-8b's, bms 4552nd's, and the supertweet'll probably cross in, first order, i'm guessing somewhere around 10-12k-ish, judging on what i've got 'measured' (in quotes, because i'm NO old hand with the RTA!).
i'm also not loathe to the idea of putting a compression driver on an appropriately sized tractrix horn or a small waveguide-- although to start with, a turnkey combo would be great...
thanks for the input!
d.
Follow Ups:
The 4552nd is a 1" compression driver right? I can't see why it can't be made flat to at least 15khz or so. For some reason I thought you were running a 2" driver and a big(ger) horn and for that I could see a super tweeter being needed. I'd suggest finding out what you can hear up to and measuring what your driver/horn is actually doing. For me, my ears are only good to around 15khz so I am happy with what I can get from my 1" driver alone.
Russ
the graph works for a particular horn, which isn't my own, and is probably farcical as well.
the horn shrieks horribly in the upper mids. maybe it's 'linear' on that horn, on that graph, in whatever instance they measured it at, but i doubt highly that anyone was LISTENING to it. it may be extended.. but it ain't usable if you have human ears and like music (!). it rolls off very smoothly past 2k on up-- which is exactly what i want it to do. if i pick it up at about 5-7k with the tail end of a 1st order with the supertweet-- it should fill in fine.
different application, i spose.
d
meanwhile-- yup it's a 1" throat-- but a 1 3/4" driver. crossover's about 1.2k -- theoretical lower threshold is 500hz.. but i doubt that's not marketing too.
i'm not too worried about the uppermost octaves-- hence my wanting it to roll past 20k-- but i do need something to carry the top octave and the next down. far as i'm concerned-- it can be down some-- but just not the 18-20db down that i've got currently! like i was saying-- it's mostly an experiment.
thanks russ-
d
Maybe this?
One thing I have been asking myself for a while is: Is the linearitiy of this graph due to the horn, the driver or is it a fake? The graphs of all 1"ers I know show a falling response similar the one that can be seen for the mentioned BMS driver on the company`s site.
I'd say the horn used is a factor. But I can't read french so who knows what I am really looking at.
Did you see the waterfall on the 2nd page? It looks to me like they get flat on axis because it "beams". But honestly, I am not qualified to answer your questions. Maybe someone else can help the both of us to reach a better understanding on how to read the given info.
Russ
A waterfall plot (CSD) doesn't show if a driver beams. It shows how its energy decays with time. In this case it looks like there's a resonance around 16kHz or so (typical). However, yes, the driver / horn does beam. Any compression driver and horn combo that has flat on-axis response that has not been eq'd to have that flat response is beaming, as all drivers have a power response that rolls off above some frequency. In this case, they show 30 and 60 degree curves and you can see the roll off at high frequencies starting around 3-4kHz. Other than that, it looks like the driver / horn combo (whatever it is) has nice smooth response.
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