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DIY ribbon dipole tweeter, reductio ad minimum
DIY ribbon dipole tweeter, reductio ad minimum
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Old 23rd August 2016, 11:10 AM   #361
middle is offline middle  Italy
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Quote:
Originally Posted by JonasKarud View Post
Cheer up, Middle, I've tried your scheme with splitting the membrane, and it did not lower the distortion.

In fact, the sound was pretty bad. A better way is to increase the membrane thickness in the middle third of the width of the membrane, increasing the flow of current where it's needed.

But the best sounding membrane I've produced is an ordinary 5 uM one with Gerrits cable corrugator.

A peculiar fact I've found in my experiments, is that a 10 uM membrane sounds almost as good as a 5 uM membrane if you're using a Metglas transformer, and that 5 uM membrane have a tendency to get tiresome in the highest octave when Metglas driven!

Will you show that experiment?
I would like to see if scheme is complete or only cuts or stripes

a better way is....

It is a tale or what?

increase the current is a good one...increase were the tickness is greater is a new one!

Do you mean the current has two different velocity going trought ribbon?
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Old 23rd August 2016, 01:10 PM   #362
Tesla Audio is offline Tesla Audio  Croatia
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Quote:
Originally Posted by Gerrit Boers View Post
What's the reason for making the ribbon 30cm long? what is the intended crossover?

regards,

Gerrit
Hi Gerrit
reason why ribbon is 30cm long is that it sound much better then small one.
As you can see on picture I have Ravens 2. membrane is about 8mm wide but it doesn't sound so good as my 30x2,5 cm. I use double magnets on each side to get homogenous magnetic field. Lundahl transformer used initially but later changed with my own amorphous.
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Old 23rd August 2016, 02:16 PM   #363
Gerrit Boers is offline Gerrit Boers  Netherlands
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Originally Posted by Tesla Audio View Post
Hi Gerrit
reason why ribbon is 30cm long is that it sound much better then small one.
As you can see on picture I have Ravens 2. membrane is about 8mm wide but it doesn't sound so good as my 30x2,5 cm. I use double magnets on each side to get homogenous magnetic field. Lundahl transformer used initially but later changed with my own amorphous.
Any measurements?

My first ribbon was 40cm. I found the narrow vertical directivity to be unacceptable and the ribbon was also very sensitive to draft.
I used purely objective (my Clio system is level calibrated) criteria for evaluation:
- frequency response
- harmonic distortion (k2-k5)
- cumulative spectral decay
- multitone (distortion) spectrum
- directivity (5 degree steps)
Using these measurements I arrived at the current design. I still have some ideas for improvement I'll have to try but it's not the season for driver experiments
Here's a multitone spectrum for my ribbon compared to the Seas Millennium tweeter as used in the Linkwitz Orion (my previous system):

ribbon-seas-millennium-multitone.png

Although the levels are not exactly the same the difference is obvious. Guess which one sounds harsher?

regards,

Gerrit
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Old 23rd August 2016, 02:56 PM   #364
kevinkr is offline kevinkr  United States
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DIY ribbon dipole tweeter, reductio ad minimum
Middle it appears that you are using the report button inappropriately when the correct response would be to use the post button. The report button is reserved for reporting violations of forum policy and other problems, not requests for objective testing evidence. Thank you.
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Old 24th August 2016, 11:33 AM   #365
Tesla Audio is offline Tesla Audio  Croatia
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Quote:
Originally Posted by Gerrit Boers View Post
Any measurements?
Hi Gerrit
during my experiments with ribbon I only measured frequency response. I remeber that curve was flat but I never saved file.
I've used double magnets 1cm wide with air gap 2mm between and 5micron foil. All this should ensure homogen magnetic field and less bending during movement. And also less distortion. I remember when someone asked Linkwitz why is not using ribbon in their system his answer was distortion. Did you measure and compare distortion between ribbon and Seas?
Does many long peaks in your measurement means harsher? What is your subject opinion which one sound better? You said that your previous system was Orion. Which one is now?

BR//
Tesla
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Old 25th August 2016, 10:24 AM   #366
Gerrit Boers is offline Gerrit Boers  Netherlands
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If I recall correctly Linkwitz does not use ribbon because of the limited vertical dispersion and the fact that there's no dipole ribbon available. The Raal dipole ribbon is not a true dipole in the sense that the level is 6dB down at 60 degrees, because of the width of the frame the dispersion will be much greater.

Here's the harmonics measurement for the Linkwitz Orion measured at 50cm halfway between the dome and the mid:

orion-50cm-harmonics.png

The harmonics for my ribbon with the Neo10 at 50cm measured mid ribbon (because the distance is so small and it is measured mid ribbon the response is not flat)

Di3-right-4th-ribbon-50cm-mid-ribbon-harmonics.png

As you can see there are a few peaks where the ribbon/Neo10 combination performs worse than the Orion but when it comes to the higher harmonics the ribbon clearly is the better performer.

The multitone spectrum shows both harmonic and intermodulation distortion. The test signal consists of 14 sine waves starting at 1kHz (actually rounded to the nearest FFT bin), these are the peaks above 60dBSPL. Everything below 30dBSPL is distortion, harmonic distortion of the sine waves and also all kinds of intermodulation distortion. If you look at the range between 10kHz and 20kHz you see that the baseline for the ribbon is still visible, with the Seas tweeter there are so many distortion peaks packed close together that the baseline is no longer visible and seem raised by about 20dB at 15kHz.
The 2nd harmonic of the first tone is 2kHz thus everything below 2kHz is intermodulation distortion only. It's a shame that the levels do not match in this area but it certainly looks like the ribbon seriously outperforms the dome when it comes to intermodulation distortion.
All this intermodulation distortion will add harshness to the sound and my guess would be that the closely packed high frequency peaks will result in increased sibilance.

My current system is described here: The Totem of Tone, an active 3-way dipole and active subwoofer
It's a significant improvement over the Orion, especially with respect to directivity, and it is even a bit smaller.

regards,

Gerrit
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Old 25th August 2016, 12:38 PM   #367
Tesla Audio is offline Tesla Audio  Croatia
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Gerrit
your The Totem project is very nice with many details. Where did you find NEO10? In Europe is impossible to find it. For bass driver I think better choice is speaker with higher Qts (less equalisation). AE is best but also impossible to find in Europe.
Similar to your NEO10 I've started in parallel another project as you can see it here:

http://www.diyaudio.com/forums/plana...ge-ribbon.html

How did you compensate bass vibrations in your Totem. I found that plate which hold bass driver vibrate and produce own sound. Therefore my front plate plexiglass is physically isolated from plate which hold bass speakers.
BR//
Tesla
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Old 26th August 2016, 07:26 AM   #368
Gerrit Boers is offline Gerrit Boers  Netherlands
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Good luck with you project!

The system is one and a half year old now, I got the Neo10 about two years ago from ProRaum but they do not have them anymore.

The baffle with the two woofers is a sandwich made of aircraft quality plywood and lead, four layers of plywood (each 6mm consisting of twelve layers of wood) and 3 layers of 3mm thick lead. With the drivers the baffle weighs 30kg, this in itself reduces the vibrations significantly. Because of the lead there's no resonance in the baffle itself. Mid and high a mounted on a separate frame, not directly coupled to the baffle.

regards,

Gerrit
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Old 25th March 2017, 03:21 PM   #369
JonasKarud is offline JonasKarud  Sweden
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In order to make the magnetic field more linear between poles in a ribbon speaker, i did some experiments with small help magnets with the help of a simulation program, see pictures.

The ordinary magnets are 10x10x40 mm, and the small help magnets are 3x3x40 mm. The help magnets are held in place by their own magnetic force, so no problems there....

Quite an improvement with the help magnets....

I'm going to test this in reality, I'll be back.....
Attached Images
File Type: jpg medmags.JPG (456.7 KB, 468 views)
File Type: jpg With&Withouthelpmags.jpg (98.4 KB, 453 views)
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Old 27th March 2017, 01:40 PM   #370
Tesla Audio is offline Tesla Audio  Croatia
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Jonas
small magnet is not necessary. Piece of metal is enough or double magnets with space 1mm between.
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