Go Back   Home > Forums > >

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

On the Distortion of Ribbon Speakers
On the Distortion of Ribbon Speakers
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
Reply
 
Thread Tools
Old 3rd October 2021, 05:20 PM   #11
Marveloudio is offline Marveloudio  Germany
diyAudio Member
 
Join Date: Jun 2004
Location: X
The original designer Alain Bernard is dead now ... info about Raven ribbons use Google Images/Pictures ... I found this one but not sure if it is still in production :

Line Source – Raven Design Studio

With iron-pole ribbon designs , some say dynamics are suppressed , sounds true to me because of the induced currents in the iron pole (remember virtual current is very high on the secondary XFormer winding) which reflects back on the ribbon that has very low driving force (BL - Factor) ... and all modern ribbon designs have neodym magnets on the sides!

Btw - seems due to economic wars the prices of neodymium will probably eXplode in the next months ...

Ribbon design is a tough job!


ps: .. some info about misc ribbon designs ... Speakers - Ribbons

Last edited by Marveloudio; 3rd October 2021 at 05:27 PM.
  Reply With Quote
Old 4th October 2021, 03:20 PM   #12
lupi is offline lupi  Italy
diyAudio Member
 
Join Date: Mar 2011
Hello Marveloudio
I have no direct knowledge of the Raven's ribbons. What I can say is that they are limited in band from 800 Hz and up, and I don't like to put crossovers, which become the weak link in the chain. However the object of this forum is to experimentally investigate the mechanisms of ribbons distortion, and I don't think Raven gives any information about it, apart from the usual bla bla: "our ribbons are wonderful, wonderful, the best in the world" etc. . The influence of induced currents, or that is the same, the modulation of the magnetic field by the current in the ribbon, will be the topic of the next posts.

But first please measure if the transformer contributes significantly to the total distortion ... and any static magnetic field should be avoid due to partial saturation. [/ QUOTE]

In post # 3 I have already specified that I don't use transformers
  Reply With Quote
Old 13th October 2021, 11:57 PM   #13
lupi is offline lupi  Italy
diyAudio Member
 
Join Date: Mar 2011
At this point I wanted to verify if the modulation of the magnetic field by the current had something to do with it. Not that I believe it possible, because according to the simulations I made the variations of the field due to the current in the ribbon are irrelevant, but since it is a hypothesis advanced by some I decided to verify it.
So I made a comparison between the distortion of the same ribbon mounted first on a motor with a magnetic field of about 0.1T obtained with 5 mm thick magnets and then on another with double the magnets (10 mm total thickness) and an adequate increase of the section of the iron closing the magnetic field, therefore with a magnetic field about double, of 0.2T. In this situation 2 things happen:
1) the same current in the 2 cases causes a percentage variation of the magnetic field smaller in the motor with a higher magnetic field
2) for the same SPL produced, the current in the ribbon on the motor with a higher magnetic field is much smaller
Therefore, any effect of modulation of the field by the current should be substantially less, for the same SPL, in the motor with a higher magnetic field.
To be sure of the results I checked the magnetic field simulations with measurements. In the following I will call motor A10 the one with double magnets and compensated with shaped pole pieces, and motor B10 the one with double magnets and flat pole pieces, while A5 and B5 resp. the motors previously called A and B.
For the sake of brevity, I define the axes as shown in the figure: red = X, green = Y, blue = Z
Origine
Motor A10
(10x25d35_3d1)
10x25d35_3d1_field (magnetic field in the plane YZ, and X=0)
Motor B10 (10x25d35_base)
10x25d35base3d_field (magnetic field in the plane YZ, and X=0)
Attached Images
File Type: jpg origine.JPG (56.8 KB, 83 views)
File Type: jpg mot 10x25d35_3d1.jpg (116.0 KB, 81 views)
File Type: jpg 10x25d35_3d1_field.jpg (121.9 KB, 83 views)
File Type: jpg mot 10x25d35base.jpg (84.9 KB, 79 views)
File Type: jpg 10x25d35base3d_field.jpg (172.7 KB, 79 views)
  Reply With Quote
Old 14th October 2021, 12:04 AM   #14
lupi is offline lupi  Italy
diyAudio Member
 
Join Date: Mar 2011
Note that the range of colors in both plots is from 0T (blue) to 0.25T (red) in 21 colors
Since in the simulations I noticed that the tolerance on the dimensions of the pole pieces is quite small, for safety I measured the Bx component with a Hall probe, both for Z = 125mm, (center of the motor) and for Z = 10mm (near 1 end ) by moving the probe along Y (direction of movement of the ribbon) I measured Bx on 3 values of X: Resp. 13.5, 8.5 and 3.5mm, in order to cover the entire width of the ribbon (27mm)
. The purple color refers to the measurements at Z = 125mm, while the brown color is for the measurements at Z = 10mm. In the 2 graphs I have kept the same scales for ease of comparison
Motor B10
10x25d35base_meas
Motor A10
10x25d35 3d1_meas
Attached Images
File Type: jpg 10x25d35base_meas.JPG (76.8 KB, 12 views)
File Type: jpg 10x25d35_3d1_meas.JPG (61.1 KB, 10 views)
  Reply With Quote
Old 14th October 2021, 12:07 AM   #15
lupi is offline lupi  Italy
diyAudio Member
 
Join Date: Mar 2011
At this point the engines are characterized and I can move on to the measures. I have used several ribbons, but since the results are the same, for the sake of brevity I will report the measurements for only one. The width of the magnetic field is 35 mm, while that of the ribbons 27 mm to avoid turbulence problems in the gaps.
C21A su 5x e 10x_base_SPL
C21A su 5x e 10x_base_THD
C21A su 5x e 10x_comp_SPL
C21A su 5x e 10x_comp_THD
Attached Images
File Type: jpg C21A su 5x e 10x_base_SPL.jpg (108.4 KB, 19 views)
File Type: jpg C21A su 5x e 10x_base_THD.jpg (115.0 KB, 20 views)
File Type: jpg C21A su 5x e 10x_comp_SPL.jpg (61.3 KB, 17 views)
File Type: jpg C21A su 5x e 10x_comp_THD.jpg (65.1 KB, 21 views)
  Reply With Quote
Old 14th October 2021, 12:15 AM   #16
lupi is offline lupi  Italy
diyAudio Member
 
Join Date: Mar 2011
I don't see significant differences in THDs, with the same SPL, so I conclude that:
The modulation of the magnetic field by the current in the ribbon, if any, is negligible.
As for what some claim, that iron pole pieces reduce distortion with a mechanism similar to that of the copper ring on moving coil speakers, it definitely seems to me like a propaganda fable.
So I ask myself: If the primary cause (s) of the distortion of a ribbon is not the non-uniform magnetic field (excluding low frequencies) nor the modulation of the magnetic field, which is it? The only culprit remains the ribbon, you want the non-linear suspensions, you want the ribbon's selfmodes, so on and on. If any of you have ideas about it or criticism of what I have written, it is welcome, as I am going to start investigating the ribbon itself (I still don't know how)
  Reply With Quote
Old 14th October 2021, 10:19 AM   #17
esl 63 is online now esl 63  Sweden
diyAudio Member
 
Join Date: Aug 2010
Location: Hisingisland
You shall drive the ribbons with an transconductance amplifier NOT a voltage amplifier.
The current is the factor that gives the force to the ribbon, not the voltage.
Try to add 20 ohms resistor in series with the ribbon and redo the distortion measurements.
Or built a current feedback amplifier directly...
  Reply With Quote
Old 14th October 2021, 05:00 PM   #18
lupi is offline lupi  Italy
diyAudio Member
 
Join Date: Mar 2011
Hi esl 63
Thanks for the suggestion. I had already noticed, on occasion, that putting an R in series decreased the distortion, but only in some cases, while in others it increased it. Then I thought about some setup anomalies, but now I'll do some systematic comparative measurements. I am not totally convinced, as being the ribbon impedance similar to a pure resistance, a current driving should not make a difference compared to a voltage one. Furthermore, with current driving, the damping effect of the movement of the ribbon would be lacking and therefore perhaps the transient response will not be the same. But it's worth a try. Thanks
  Reply to this post

Reply


On the Distortion of Ribbon SpeakersHide this!Advertise here!
Thread Tools

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 Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Radian - Ribbon Drivers/Ribbon Coaxial - Has anyone used these? WhereitsAT Multi-Way 14 30th September 2021 09:45 AM
Ribbon Tweeter Distortion angsuman Multi-Way 60 8th July 2019 03:57 PM
DIY ribbon info requested (constructing a ribbon unit) SpinMonster Planars & Exotics 15 11th April 2011 08:27 PM
Fountek ribbon tweeter 3cm2 ribbon black square alumunum faceplate lduarte1973 Multi-Way 3 16th June 2009 08:50 AM
Ribbon distortion jirka Multi-Way 4 2nd October 2006 08:22 AM


New To Site? Need Help?

All times are GMT. The time now is 12:38 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki