Stackable ribbon module - Page 2 - diyAudio
 Stackable ribbon module
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Planars & Exotics ESL's, planars, and alternative technologies

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
diyAudio Member

Join Date: Apr 2008
Location: Rapperswil at Lake Zürich
Quote:
 Originally Posted by brunob Which cavity do you have in mind? Could you elaborate? Thanks
The ribbon hangs between the two magnet rows, Those magnets are spaced between maybe one and five cm from each other, depending from ribbon.

Then we have the magnet depht, maybe 2- 4cm, depending on magnet size.

Those both values fome a cavity , which make reflections and form the resonance. The structural integrity of the ribbon itself is also not to forget.
Say the space is 3 x 4 cm, the F res will be somewhere around 5-7 Khz and can be easy up to 6 dB.

To lower the effect you can put the ribbon more forward to the front of the magnets and use magnets with less depth and most important, make the edges round to optimize the diffraction and use magnet formed like pole shoes.
Or you can use a tank circuit, but this will cost you efficiency and money for parts.

diyAudio Member

Join Date: Mar 2005
Location: Erlangen, Germany
Quote:
 Originally Posted by Groove-T The ribbon hangs between the two magnet rows, Those magnets are spaced between maybe one and five cm from each other, depending from ribbon. Then we have the magnet depht, maybe 2- 4cm, depending on magnet size. Those both values fome a cavity , which make reflections and form the resonance. The structural integrity of the ribbon itself is also not to forget. Say the space is 3 x 4 cm, the F res will be somewhere around 5-7 Khz and can be easy up to 6 dB.
The two 20 cm long magnet rows are spaced by 1.2 cm.
The magnets are 1.5 cm deep.
Could you predict the frequency of the observed dip (measured at 4 to 5 KHz) ?

Quote:
 Originally Posted by Groove-T To lower the effect you can put the ribbon more forward to the front of the magnets and use magnets with less depth and most important, make the edges round to optimize the diffraction and use magnet formed like pole shoes. Or you can use a tank circuit, but this will cost you efficiency and money for parts.
When I move the ribbon more forward to the front of the magnets (the ribbon is about 1 -2 mm deep from the top) then the dip increases by 4 - 5 db , but the frequency remains the same. On the other hand, when I move the ribbon more backward, close to the back of the magnets (the ribbon is then about 13 -14 mm deep from the top), then the dip disappears.

Also, when I place the measurement microphone very close to the ribbon (less than a few cm, I don't remember exactly), then the dip disappears (the ribbon was placed in the middle the gap).

Adding wings to the side of the ribbon decreases the frequency of the dip and increases the intensity of the dip.

Decreasing the height of the ribbon, from 20 to 5 cm, does not affect the dip.
Increasing the distance between the two magnet rows (=wider ribbon gap) does not affect the dip (distances tried: 1.0, 1.2 , 1.5 and 2.2 cm).

Bruno

diyAudio Moderator R.I.P.

Join Date: Nov 2005
Quote:
 Originally Posted by brunob On the other hand, when I move the ribbon more backward, close to the back of the magnets (the ribbon is then about 13 -14 mm deep from the top), then the dip disappears. Bruno
I use felt behind the ribbon
and its placed in line with front of magnets, with waveguide

 14th October 2011, 12:47 PM #14 diyAudio Member     Join Date: Apr 2008 Location: Rapperswil at Lake Zürich Hi Bruno Sorry, im no expert. What i wrote is from experience with Apogee Ribbonspeakers and what they wrote in their patent letters, how to reduce those and other effects. But they had pretty long ribbons, between 60 and 200cm, so the effect is maybe different. But what is astonishing, the cavity resonance gives usually a broad peak, not a dip. So maybe i am on the wrong path. I did not read correct first, what you wrote. Sorry. My german is better for sure. Just as an idea: What happens with a longer ribbon and lesser tension? Your dip is apx. 4 khz, giving a wavelength around 8cm. Last edited by Groove T; 14th October 2011 at 12:52 PM.
diyAudio Member

Join Date: Mar 2005
Location: Erlangen, Germany
Concave line array in progress

I started building a concave line array that will be made of 8 ribbon units.
Height: about 170 cm. Listening distance : 138 cm. All units will aim at this distance.

I have never seen and heard such a design (if you know one, please post!).

- unusual large vertical listening angle => huge image
- unusual large surface for a tweeter: 24 x 8 = 192 cm2

Disavantages:
- only one listener

Each unit will use several layers of 0.8 micron aluminium foil.
XO: 1000 Hz, first order with a planar.

Bruno
Attached Images
 2012-04-01 11.22.18.jpg (318.7 KB, 254 views)

diyAudio Member

Join Date: Jun 2005
Location: Fort Worth, Texas
Quote:
 Originally Posted by brunob I started building a concave line array that will be made of 8 ribbon units. Height: about 170 cm. Listening distance : 138 cm. All units will aim at this distance. I have never seen and heard such a design (if you know one, please post!).
Bill Waslo(Liberty Instruments) wrote a 3 part article in Speaker Builder magazine back in 1998 on design and construction of a focused-array ESL.

I seem to recall Bill summarized the listening experience as "you are there" rather than "they are here".
Definitely a very large single listener setup.

You might contact bwaslo here on DIYaudio if you want further details on his design and listening impressions of the concave line array.
Attached Images
 Waslo_FA_ESL.jpg (47.1 KB, 244 views)

diyAudio Member

Join Date: Mar 2005
Location: Erlangen, Germany
Quote:
 Originally Posted by bolserst Bill Waslo(Liberty Instruments) wrote a 3 part article in Speaker Builder magazine back in 1998 on design and construction of a focused-array ESL. I seem to recall Bill summarized the listening experience as "you are there" rather than "they are here". Definitely a very large single listener setup. You might contact bwaslo here on DIYaudio if you want further details on his design and listening impressions of the concave line array.
Thanks. I have sent him a PM inviting him to write a post.

Bruno

diyAudio Member

Join Date: Jun 2007
Quote:
 Originally Posted by brunob Thanks. I have sent him a PM inviting him to write a post. Bruno
very interesting, any news?

I would like very much to see vertical polar plots of such a focused array

diyAudio Member

Join Date: Mar 2005
Location: Erlangen, Germany
Focused array

Quote:
 Originally Posted by graaf very interesting, any news? I would like very much to see vertical polar plots of such a focused array
Bill did answer me but unfortunately, he did not post here. I hope that he will not mind if I post his answer here - IMO this is unique and valuable information that is worth posting.

"Those were made about 12 years ago and were listened to for only about a month. The very narrow sweet spot finally got on my nerves and the family didn't appreciate them dominating the room so much. I gave the panels and other parts away a few years ago.

I've pretty much gone to the opposite extreme - omnidirectional for a while, line array dipole, and now controlled directivity (waveguide). I don't have anything much to say about the focused arrays except they were like really big headphones, but not as convenient. They did play really loud, though, lots of gain from focusing.
"

Bruno

diyAudio Member

Join Date: Mar 2005
Location: Erlangen, Germany
Triple layer stacked ribbon

I (re)made a triple layer ribbon. The three ribbons are stacked on top of one another with a about 0.5 mm space. They might touch each other at some places. (PS: this driver is not easy to build - the foil is very thin and very fragile).

Ribbon width: 15 mm
Length : 200 mm
Thickness: 0.8 microns (no typo here)

The three layers are connected in parallel.
Measured resistance with one layer: 0.61 Ohms
two layers: 0.31 Ohms
three layers: 0.20 Ohms

The total ribbon surface is 3 x 30 cm2 = 90 cm2.

FR measurements:
Microphone ECM8000 - pseudo calibrated using a calibration file found on the web
Amplifier: Panasonic SA-XR 58
Microphone distance: 53 cm
No level calibration.
Software: Arta

Important: no transformer was used. A 8 Ohms resistance (Mundorf) was connected in series with the ribbon. This means that the total current that flows through the ribbon(s) barely changes with the number of layers. With a transformer that is optimized for each driver resistance, I would expect that the 3 layers ribbon would be more sensitive.

The bottom measurement is a 9 microns corrugated ribbon. Its electrical resistance is 0.09 ohms. I use it as my reference.

The plot shows a decrease of the FR above 10KHz with the increase of the number of layers. There is about a 3db loss at 20KHz for 3 layers.

Bruno
Attached Images
 3L sept 2012.png (28.3 KB, 104 views) 20120923_164505.jpg (247.6 KB, 103 views)

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post SpinMonster Planars & Exotics 15 11th April 2011 08:27 PM endangeredaudio Vendor's Bazaar 0 5th March 2010 03:03 PM lduarte1973 Multi-Way 3 16th June 2009 08:50 AM ingrast Digital Source 0 12th September 2004 09:24 PM DJG Swap Meet 0 12th December 2002 11:01 PM

 New To Site? Need Help?

All times are GMT. The time now is 12:17 PM.