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Old 8th July 2005, 07:09 AM   #1
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Default Improving on the LCY uniform dispersion ribbon

At first I wanted to modify the LCY 130 tweeter... but after I figured out that doing so would only really leave me with the original mounting flange (everythign else would be changed) I decided to save the $400 for a flange and build my own...

Goal:
1 T field across the gap
Uniform (dome like) dispersion.. with little to no beaming even into 10khz... very wide dispersion is key
true ribbon (alum) 5 microns thick
at LEAST 95db efficent... hopefully more (we'll see how far I can push this)
ability to play to be crossed at 1.5khz with a 24db/octave slope while maintaining good power handling...

I'll be playing in FEMM trying to come up with stuff... linesource please help

refer to here http://www.e-speakers.com/products/lcy-components.html for graphs that I want this to look like... but BETTER! and the ability to be crossed at 1.5khz or LOWER while maintaining a nice power handling.
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Old 8th July 2005, 03:34 PM   #2
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anyone???
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Old 12th July 2005, 11:13 AM   #3
10K2HVN is offline 10K2HVN  United States
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honestly, at what distance do you listen to your speakers at?

sitting position to standing position is about ~30 inches; 30 inches at a further distance doesnt really change the angle at which the speaker is pointing at you, much...

and how often, do you move up and down while your actually listening..?

when youre moving around (doing stuff while trying to listen to your music) does 16khz to 20khz really matter that much?? because your not really intensely listening because youre doing something else too...

i think, in-part, because of the ribbons shortness, it has a better vertical response (and the mini horn loading).

if you make the ribbon any shorter, youll probably gain better vertical response, but at the cost of less cone area and it turn, this will also effect the efficiency (less) and lowend extension.

like any driver, when you increase cone area, you usually gain efficiency and lowend extension but lose topend dispersion. and when you decrease cone area, you lose sensitivity and lowend extension, but gain topend dispersion.

your wanting all the strengths and none of the weakness's, which is a good thing but like in life, theres always compremises.

find out which you want more and either go for a conventional tweeter, or go ribbon tweeter.

honestly, the vertical response doesnt bug me at all, its very good!
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Old 12th July 2005, 04:05 PM   #4
lcholke is offline lcholke  United States
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Default beaming

It looks like LCY made the super tweeter to fix the high frequency dispersion problem. I am not shure why, but beaming occurs when the driver is the size of the wavelength. This is also the point where the mechanical efficiency stops rising. The only reason I can think of is that when the wave length is smaller then the driver, the driver can get hold of the air and push it. I think a rough analogy is the transition that happens when a boat moves from no wake speed to above it. That is why the large drivers beam at lower frequencies.

-Linc
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Old 12th July 2005, 05:04 PM   #5
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Default Re: beaming

Quote:
Originally posted by lcholke
It looks like LCY made the super tweeter to fix the high frequency dispersion problem. I am not shure why, but beaming occurs when the driver is the size of the wavelength. This is also the point where the mechanical efficiency stops rising. The only reason I can think of is that when the wave length is smaller then the driver, the driver can get hold of the air and push it. I think a rough analogy is the transition that happens when a boat moves from no wake speed to above it. That is why the large drivers beam at lower frequencies.

-Linc

right... there is a distinct difference to me between large dispersion fields and small ones from the tweeter... without a doubt the advantage of a dome/LCY ribbon is that you can move about or be off of the center and have good sound...

also a HUGE advantage is that with larger dispersion, it feels like the room is filled with far more music than with a small field, at least to me...

beaming is an issue that I'm pushing to avoid at all costs in my setup
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Old 17th July 2005, 08:23 AM   #6
10K2HVN is offline 10K2HVN  United States
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Click the image to open in full size.

Hows that for vertical off-axis response!
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Old 17th July 2005, 04:22 PM   #7
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The LCY ribbon seems to conform to a US Patent that I read about a year back. It uses the same slit in the ribbon which is why I suggest it may be the same design...

I saw their ribbon but am very puzzled by their front flange - it seems all wrong to me, but there may be mechanical reasons for its design, I dunno. If I owned one, I think the first thing I'd do is to try to replace and change the front flange.

The sharp transition right in front of the ribbon itself seems wrong. But, this may provide just enough diffraction to broaden up the polar response at highish freqs. (...method to the madness)

If you can build ribbons (not so easy) with suitably light and strong and very thin foil, and have a large chunk of neodymium magnets around (like a pound or so - ~1/2 kg) and have a FEM program to get the flux through the gap, ur good to go!

Seat of the pants will probably work, although you may not hit that 95db goal...

Oh, the somewhat square aspect ratio of the LCY ribbon probably contributes to its apparently good polar response, although I'll bet if you actually have one and measure it, it's no where as good as they claim.

For most rooms 20- 30 deg dispersion is more than adequate, believe it or not. The "problem" comes in when the dispersion is not axisymetric, as with a typical ribbon - the horizontal is usually fairly wide, but the vertical is not. And, they don't shift (the vert & horiz) at equal rates either. This makes it audible if you move through the vertical axis.

Having owned some of the very finest small ribbon mid/tweets, I've found the vertical dispersion to be of practical concern - not in the ideal listening position, but everywhere else.

Of course in some situations the heresey of turning the ribbon 90 degrees works nicely!

It's still a project worth trying, if you like building...

BTW, I tried emailing the mfrs, but they never responded... I was interested in importing the unit at the time.


_-_-bear
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Old 17th July 2005, 04:33 PM   #8
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Oh, you can't get it to cross at 1.5 khz.

That would require a larger ribbon = higher mass, worse HF dispersion.

You can build TWO ribbons - one larger for the 1 - 7 kHz range, and the little one for the top... that's "legal".

To keep the output up you run into the problem of the distance between the magnet poles is increased if the ribbon aspect ratio remains the same, but the size is increased, meaning lower flux = lower output.

Which is why ribbons that run down that low are usually much longer and still relatively thin in width - to keep the output up, and the gap from being too wide...

Department of no free lunch.

The LCY ribbon simply will not have enough Xmax to run at 1.5kHz - or for that matter any lower than they spec it at now. You can be sure they are pushing matters as it stands!

The power handling is a function of the thermal limit for the thickness of the aluminum foil and its length, nothing more. So, you will only melt the aluminum beyond a certain power limit, no matter what else is going on. Make the aluminum foil ribbon longer, and that changes the power handling at the expense of polar response, mass and standing waves on the ribbon, etc...

Still no free lunch...

_-_-bear

PS. the gap to the sides of the ribbon also plays a role in the highest freq that can be reproduced...
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Old 17th July 2005, 10:58 PM   #9
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Quote:
Originally posted by bear
Oh, you can't get it to cross at 1.5 khz.

That would require a larger ribbon = higher mass, worse HF dispersion.

You can build TWO ribbons - one larger for the 1 - 7 kHz range, and the little one for the top... that's "legal".

To keep the output up you run into the problem of the distance between the magnet poles is increased if the ribbon aspect ratio remains the same, but the size is increased, meaning lower flux = lower output.

Which is why ribbons that run down that low are usually much longer and still relatively thin in width - to keep the output up, and the gap from being too wide...

Department of no free lunch.

The LCY ribbon simply will not have enough Xmax to run at 1.5kHz - or for that matter any lower than they spec it at now. You can be sure they are pushing matters as it stands!

The power handling is a function of the thermal limit for the thickness of the aluminum foil and its length, nothing more. So, you will only melt the aluminum beyond a certain power limit, no matter what else is going on. Make the aluminum foil ribbon longer, and that changes the power handling at the expense of polar response, mass and standing waves on the ribbon, etc...

Still no free lunch...

_-_-bear

PS. the gap to the sides of the ribbon also plays a role in the highest freq that can be reproduced...

thanks bear...

I have a pair of these LCY's coming ... I might return them if I decide to DIY... but I'll take some internal pics for you...
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Old 18th July 2005, 03:59 PM   #10
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Ok... would like to see the pix...

Where did you have to go to buy a pair??

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