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Possibly an underdamped resonance but, except for level, foils that similar shouldn't sound noticeably different. Have you measured impedance? Maybe the protection circuitry in your amp is kicking in with the slightly lower impedance?
is it that you can hear the resonances in the aluminium? I was running my little 4 by .5 inch from about three hundred hz, and sometimes it would sound like a fly caught inside. i hope to be able to beat that with a wider ribbon... we shal see.
tade said:
yea it sort of sounded like that... flapping in the wind... but the xover is 24db at 2.5 khz
I noticed that my annealer cut two needle size holes in this ribbon... this probably isn't the problem though
nope no protection circuitry...
this amp is 2 ohm stable and this xfrmer is for 4 ohm nominal
I need to go get a DMM and do some testing...
Aluminum solder and silver solder paste similar to products on this website might be of interest to ribbon builders for making electrical contacts. There may be better solders available, as well as silver filed epoxy.
http://www.solder-it.com/solderpaste.asp
Some ribbons builders put dampening material like wool or foam rubber at the top and bottom ribbon clamps to absorb resonant vibrations. For large, wide bandwidth ribbons, this type of "shock absorber" can keep the ribbon from tearing at hard end clamps.
http://www.solder-it.com/solderpaste.asp
Some ribbons builders put dampening material like wool or foam rubber at the top and bottom ribbon clamps to absorb resonant vibrations. For large, wide bandwidth ribbons, this type of "shock absorber" can keep the ribbon from tearing at hard end clamps.
I just realized i have a source of five micron mylar from capacitors! this and the fact that i plan to use a quarter inch magnet gap. this should give me uber high efficincy right? The ribbon will be four inches long. which would give me a whole inch of area for tweeting. should be plenty? ill post some pics. i am also planning on using as much of a full sheet of MDF for just two two ways. should be fun!
I realized my mistake.when i said mylar i meant foil. My mistake. it doesnt seem terribly difficult to work with too either.
sorry to say, i didnt understand your last post lcholke.
i have some pics of the ribbons i built:
http://www4.ncsu.edu/~tkwolick/ribbon/front.jpg
http://www4.ncsu.edu/~tkwolick/ribbon/rear.jpg
Note the channels carved away on the rear to allow the driver to breath. Also note the all wood construction of the ribbon. no magnetic return path. i suppose i just used really strong magnets and a narrow gap. 1/4 inch. i am using small oak block to hold the ribbon and pasta underneath for good spacing.
right now i am using household aluminum foil. ill put the nice stuff in later. they sound reall good.
here is an amusing ribbon video. i think that was a test tone.
http://www4.ncsu.edu/~tkwolick/ribbondeath.wmv
right now the ribbon is running crossed over at 3 khz and run through a one ohm resistor. is this destroying my amp? basically shorting it out?
i have some pics of the ribbons i built:
http://www4.ncsu.edu/~tkwolick/ribbon/front.jpg
http://www4.ncsu.edu/~tkwolick/ribbon/rear.jpg
Note the channels carved away on the rear to allow the driver to breath. Also note the all wood construction of the ribbon. no magnetic return path. i suppose i just used really strong magnets and a narrow gap. 1/4 inch. i am using small oak block to hold the ribbon and pasta underneath for good spacing.
right now i am using household aluminum foil. ill put the nice stuff in later. they sound reall good.
here is an amusing ribbon video. i think that was a test tone.
http://www4.ncsu.edu/~tkwolick/ribbondeath.wmv
right now the ribbon is running crossed over at 3 khz and run through a one ohm resistor. is this destroying my amp? basically shorting it out?
tade said:
you probably have <25% of the magnetic strength you could have if you had a return path
I used giant 1" thick N50 magnets and even with a return path the magnetic gap COULD be better IMO
did you graph your ribbon in FEMM to see what kind of gap you actually have??
no, i do not know what the strength of the magnets are. is that important to get results? yes, i think the way for me to increase efficiency is to use better foil and decrease gap width.
tade said:
are they cermanic or neodymium??
makes a big difference
how thick are they?
using 4-5 micron foil would help... but... it's really cheap to go the magnet route
from the pics I think your magnets are less than 1/4"... which is very very small if they aren't N40-N50 Neo's...
actually they look less than 1/8" thick...
I would say that given that... if they are ceramic you probably have a gap strength of <.2 T.... if that were increased to 1T like my LCY's are you could expect up to 8db increase in efficency... and MAX SPL as well
something like .25"-.5" N50 magnets would be quite nice in bumping up efficency
I wouldn't shorten the gap...
though this increases magnetic strength... it decreases ribbon area and therefore decreases efficency... probably by the same amount it increases efficency
they are neodium, but their exact makeupill have to check on. they are two rows of quarter inch cubes. i think sixteen per side.
tade said:
if they are less than N40 you might wanna look into upgrading there... and making a U-shaped magnet circuit should drastically increase efficency
i could get more efficincy, but do i need to? i think they are a bit better than my 80db/w woofers. i suppose better magnets will make it a bit quicker. but i doubt enough to worry about this pair.
Hi tade,
I ran some simple calculations on your 4" x 0.25" x 4 micron ribbon which estimate that a steep crossover at 4.3Khz will likely be necessary to reach 110db/1m SPL transients with a 0.2mm Xmax. (my rule of thumb for home ribbons)
The FEMM simulations in this thread show positive data for tweeter ribbon designs having a heavy iron frame with cross-bracing to complete the magnetic circuit. Ribbons ~ 0.5" wide, ~ 6" long are typically used for 2-way designs with LR4 at 1.5Khz. A 0.5" wide 5 micron ribbon should reach 30Khz.
A tweeter bezel is often only 0.25' - 0.3" thick quarter round, or a 30 degree angle diffraction cut. Deeper bezels quickly start to act like a wave guide and start to control dispersion - which you may or may not want to do.
I ran some simple calculations on your 4" x 0.25" x 4 micron ribbon which estimate that a steep crossover at 4.3Khz will likely be necessary to reach 110db/1m SPL transients with a 0.2mm Xmax. (my rule of thumb for home ribbons)
The FEMM simulations in this thread show positive data for tweeter ribbon designs having a heavy iron frame with cross-bracing to complete the magnetic circuit. Ribbons ~ 0.5" wide, ~ 6" long are typically used for 2-way designs with LR4 at 1.5Khz. A 0.5" wide 5 micron ribbon should reach 30Khz.
A tweeter bezel is often only 0.25' - 0.3" thick quarter round, or a 30 degree angle diffraction cut. Deeper bezels quickly start to act like a wave guide and start to control dispersion - which you may or may not want to do.
tade said:
you need a magnetic circuit... and thicker magnets and a wider gap
as it stands that ribbon can only play to 4khz or so... you need it lower
aim for .5" wide
should get you closer to 2khz HP
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