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my ribbons full range in CB
my ribbons full range in CB
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Old 1st August 2017, 12:22 AM   #11
lupi is offline lupi  Italy
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Join Date: Mar 2011
I have put in the box only ribbons with Alu thick 80 um. With Alu 10 um I have not tried, given the results of the simulations.
Ribb2 in box 40 l: Alu 80 μm, 4 strips in series, with depron, side suspension paper impregnated with silicone rubber, mic at 3 cm, 0.43W input, uncalibrated system.

ribb2 box-30dB.jpg

The position and heigth of the peak on the low has a good similarity, considering the uncertainties about parameter values, with the one provided by the SW "UniBox". Very good software.
At this point I put in front of the amplifier a modified notch filter for low correction and a order 1 filter for high correction. The result below:

ribb2 box-30dB_comp.jpg

Aside from some peaks on the THD that tell me I have to adjust something (however they are under 35dB), I will have to change the compensation on the highs with a second or third order. I'll do it later. For now I'm fine. Another ribbon made as ribb2:
Ribb3 = ribb2 except that I made cross engravings in the depron about each cm, in box 40 l and with electronic compensation, mic at 4 cm, 0.43W input, calibrated system
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File Type: jpg ribb2 box-30dB.jpg (102.1 KB, 81 views)
File Type: jpg ribb2 box-30dB_comp.jpg (102.8 KB, 42 views)
File Type: jpg ribb3 box-30dB_comp_cal.jpg (100.5 KB, 28 views)
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Old 1st August 2017, 09:43 AM   #12
bentoronto is offline bentoronto  Canada
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my ribbons full range in CB
Quote:
Originally Posted by lupi View Post
Aside from some peaks on the THD that tell me I have to adjust something (however they are under 35dB)..
Great thread, astonishing performance both frequency and distortion, thanks.

Not a much of a problem to have speaker artefacts at -35dB; that's wonderful.

B.
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Old 1st August 2017, 11:37 PM   #13
lupi is offline lupi  Italy
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Thank you Bentoronto
Lupi
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Old 2nd August 2017, 01:05 AM   #14
lupi is offline lupi  Italy
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Now a look at the directivity.
Ribb3 in CB 40 l, mic at 20 cm, 0.43W input, with electronic compensation, calibrated system, red: 0 , green: 30 , blue: 45 smooting = 1/12

ribb3_angle.jpg

I had to do the measurement with a mic at 20 cm because at higher distances the responses are altering too much. I have walls and close objects, and putting even 8 cm thick absorbents does not work.
Curves begin to differentiate around 3000Hz, and at 10 KHz the 45 curve is about 8 dB below 0 . I could calculate the dispersion by the width of the tape, but I wanted to do the same because I was hoping to improve it with an acoustic lens or a diffuser.
Instead, I only got a slight improvement with a lens made of soft foam polyurethane, but most attempts have come about unacceptable holes between 10 and 20 kHz. So I left the idea of the lens and I'm considering making the final ribbon less wide, 30 mm, even considering that I heard from this 100 cm^2 ribbon bass full, clean and robust, very satisfying. So even if the final ribbon will have 277 cm^2 rather than 370 will still be a good improvement over what's now already good.
I'm not a fan of omnidirecctionality, and I think a bit of directionality is right, but I would prefer that the curves begin to divide over 5 KHz
There is also the possibility of making the tape a little longer, eg 130 cm. I have to think about the problems involved
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Old 2nd August 2017, 02:07 AM   #15
bentoronto is offline bentoronto  Canada
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my ribbons full range in CB
Those speakers are wonderful. No reason to hear with your eyes by looking at curves.

1. There's nothing playing that is worth hearing over 10kHz (even if anybody could hear it... and almost nobody can really check their >10kHz hearing properly whatever they may falsely think).

2. 45-degrees is larger angle than covering your whole room!

3. 8 dB in the context of all the variation in room sound and human hearing is trivial perturbation.

Didn't we have some big arguments in this forum about beaming recently? An insignificant matter, in my opinion, and hardly worth bending speakers out of shape to combat beaming.

B.
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Last edited by bentoronto; 2nd August 2017 at 02:09 AM.
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Old 3rd August 2017, 12:09 AM   #16
lupi is offline lupi  Italy
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Hi Bentoronto
Your words encourage me and, in principle, I agree with what you said. That is why I ask you the following question, on which I am thinking now: If you were to make a ribbon and should choose between 4x92 cm and 3x130 cm, what would you choose?
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Old 3rd August 2017, 06:07 AM   #17
Thomas Spilcker is offline Thomas Spilcker  Denmark
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4 x 92 or 8 x 45 cm. Power in one point.
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Old 3rd August 2017, 07:14 AM   #18
gentlevoice is offline gentlevoice  Denmark
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my ribbons full range in CB
Hi lupi,

Quote:
All the 80 um ribbons I made, with many variations, fell like that on the highs. Since theory states that weight affects performance but not frequency response, I have sought the reason for these results,
Some other diyaudio member, I don't remember who nor in which thread, made some measurements on various thicknesses - and thus masses - of membranes and found a clear correlation between HF extension and thickness. Those that were thinner had (much) better hf extension. Made on electrostatic speakers so inductance may not matter here (?).

Cheers,

Jesper

P.S.: Given a fixed drive force I would also expect higher masses to cause a drop in HF response. Just consider moving 1 kg quickly back and forth with the same force as moving 1 gram. The 1 gram item will be moved much further.
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Old 3rd August 2017, 11:45 PM   #19
lupi is offline lupi  Italy
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Hi Spilker.
Please can you be more explicit? I'm not familiar with how to say in English
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Old 4th August 2017, 12:17 AM   #20
lupi is offline lupi  Italy
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Quote:
Originally Posted by gentlevoice View Post
Hi lupi,



Some other diyaudio member, I don't remember who nor in which thread, made some measurements on various thicknesses - and thus masses - of membranes and found a clear correlation between HF extension and thickness. Those that were thinner had (much) better hf extension. Made on electrostatic speakers so inductance may not matter here (?).

Cheers,

Jesper

P.S.: Given a fixed drive force I would also expect higher masses to cause a drop in HF response. Just consider moving 1 kg quickly back and forth with the same force as moving 1 gram. The 1 gram item will be moved much further.
Hi Gentlevoice
Perhaps in the case of electrostatic speakers it is as you say, but in the case of this ribbon it is certain that the fall on the highs is due to the inductance. In fact, if you look at the 80 um ribbon impedance curve in the previous page, and consider what is said in the context, that is, the curve is slightly shifted in up, at 10 KHz the impedance is twice as high as 1 kHz, so the inductance certainly causes a decrease of 6 dB at 10 kHz. As a further test I made a measurement by putting 1 ohm in series, and the curve was almost flat up to 20 KHz
Sorry, bat what is said in your P.S. applies to all frequencies, not just for those high ones. The theory is right.
Cheers
lupi
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