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Old 19th September 2012, 03:23 AM   #21
Few is offline Few  United States
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Location: Maine, USA
Adding resistors in series can present an easier load to the amplifier, but it also dissipates energy as heat instead of sound. You end up throwing away watts (energy/time). If you have watts to burn that's fine. If not, maybe there are more elegant solutions.

The studies I've seen suggest that ribbon corrugations don't improve harmonic distortion performance. Of course some say harmonic distortion isn't a meaningful indicator of speaker performance so you can decide for yourself whether that information is useful.

I would expect that damping the *ends* of a ribbon would reduce the magnitude of its low frequency resonances but would likely have less effect on the higher frequency ones---the ones you're most likely to hear with the suggested pink noise test. Using felt to control resonances will probably have more effect at low rather than high frequencies as well. I think other approaches will be more effective if you have "crinkling" sounds to eliminate.

Few
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Old 20th September 2012, 08:10 AM   #22
hanski is offline hanski  Finland
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Thanks for all tips guys. Based on the replies, I started thinking that maybe my ribbons are too wide. The idea behind my 70mm wide ribbons was to get some bass extension.
Now I'm a bit more experienced and I know that narrow ribbons without a wide baffle are no real bass transducers.

So I brought back my 40mm wide ribbons. The side by side comparison with 70mm ribbons showed that 40mm wide had more pleasant sound (both foil only ribbons).

Then I started experimenting with adding series resistor with 40mm wide ribbon. I added 0.1Ohm at a time and the sound cleaned up the more I added resistance.
So maybe my SE amp was not so good after all. The simulations showed low distortion numbers, but I haven't done any real measurements. Or it might be so that speaker cable inductance had too big role with 0.2Ohm ribbon resistance. I don't really know.

With 1Ohm series resistor the sound was much more clear than before. The downside was that about 80% of amplifier power was lost to resistor and SPL was low. I realized that it's not possible to continue with class A SE amp anymore. So I wired up my Hypex UCD amp (the specs say 1Ohm load impedance is ok). Side by side comparison showed that UCD amp had different sound compared with class A amp. I couldn't agree with my self which one was better, because both amps needed a bit different ribbon equalization to sound more similar with each other.
Oh well, maybe it's time to order a pair of Hypex Ncore modules..
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Old 20th September 2012, 02:28 PM   #23
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Location: wigston leics england
Quote:
Originally Posted by Few View Post
Adding resistors in series can present an easier load to the amplifier, but it also dissipates energy as heat instead of sound. You end up throwing away watts (energy/time). If you have watts to burn that's fine. If not, maybe there are more elegant solutions.

The studies I've seen suggest that ribbon corrugations don't improve harmonic distortion performance. Of course some say harmonic distortion isn't a meaningful indicator of speaker performance so you can decide for yourself whether that information is useful.

I would expect that damping the *ends* of a ribbon would reduce the magnitude of its low frequency resonances but would likely have less effect on the higher frequency ones---the ones you're most likely to hear with the suggested pink noise test. Using felt to control resonances will probably have more effect at low rather than high frequencies as well. I think other approaches will be more effective if you have "crinkling" sounds to eliminate.

Few
So can crossovers, even more so. Full range planars are the way to go for the easiest way to get the full range of music.Simple as well.
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Old 20th September 2012, 02:42 PM   #24
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Quote:
Originally Posted by hanski View Post
Thanks for all tips guys. Based on the replies, I started thinking that maybe my ribbons are too wide. The idea behind my 70mm wide ribbons was to get some bass extension.
Now I'm a bit more experienced and I know that narrow ribbons without a wide baffle are no real bass transducers.

So I brought back my 40mm wide ribbons. The side by side comparison with 70mm ribbons showed that 40mm wide had more pleasant sound (both foil only ribbons).

Then I started experimenting with adding series resistor with 40mm wide ribbon. I added 0.1Ohm at a time and the sound cleaned up the more I added resistance.
So maybe my SE amp was not so good after all. The simulations showed low distortion numbers, but I haven't done any real measurements. Or it might be so that speaker cable inductance had too big role with 0.2Ohm ribbon resistance. I don't really know.

With 1Ohm series resistor the sound was much more clear than before. The downside was that about 80% of amplifier power was lost to resistor and SPL was low. I realized that it's not possible to continue with class A SE amp anymore. So I wired up my Hypex UCD amp (the specs say 1Ohm load impedance is ok). Side by side comparison showed that UCD amp had different sound compared with class A amp. I couldn't agree with my self which one was better, because both amps needed a bit different ribbon equalization to sound more similar with each other.
Oh well, maybe it's time to order a pair of Hypex Ncore modules..
My receiver goes down to 4 ohms, and my full range planar has 3.7 ohm input +7 and 15 ohm inputs. The diaphragm on its own is 3.7 ohms which is OK.It is full range and is 16" x 37" in size.I have built A4 sized full range as well.I have various valve amps which have 4 ohm outputs and they drive my planars quite well. Using 12 um mylar and 3 mm aluminium tape has increased the sensitivity as well.A taught diaphragm certainly gets rid of funny noises.
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Old 21st September 2012, 08:27 AM   #25
hanski is offline hanski  Finland
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Thanks Jamesbos,
someday I should build also a planar magnetic speaker according to your recipe.
Planar magnetics have many benefits compared to end supported foil only ribbons.
Amplifier friendly impedance being one of them.
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Old 22nd September 2012, 08:58 PM   #26
hanski is offline hanski  Finland
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Hello all,
I'm designing a new corrugation gear.
I'm aiming for more corrugations per cm than my current ribbons and more sinusoidal corrugation pattern. The present ones look like a triangle wave.
Picture below..

Any suggestions what to aim for?
Attached Images
File Type: jpg gear.jpg (69.1 KB, 406 views)
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Old 22nd September 2012, 11:04 PM   #27
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don't bother with corrugations especially if you want a full range speaker. I NEVER DID AND I am quite happy with my full range planars. Much more inclusive than ribbons. You don't need crossovers with full range. Which only waste sensitivity and need a lot of sorting out. I think ribbons are a waste of space. Still this is only my idea other people may disagree. Each to his own . But after years and many designs, I have come to this conclusion.
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Old 22nd September 2012, 11:51 PM   #28
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Default Ribbons ...

The only book currently available about

Ribbon Loudspeakers Theory & Construction
by Justus Verhagen (Author)

published by Audio Amateur Press - was $24.95 when first published ...

Other suggestion is to use Plastic Film Capacitor Aluminum Foil - Unroll a quality cap and get a life time supply !

Jim
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Old 6th October 2012, 10:25 PM   #29
hanski is offline hanski  Finland
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Thanks Torroid88, I ordered the book.

I noticed that this company uses different corrugation style than Apogee (fewer corrugations per cm):
Mono and Stereo: Miro Krajnc SoulSonic Wave loudspeaker

And this link says they use 8um thick foil only ribbon:
http://1pekingroad.com/zaspx/replies...e&orderby=desc

I have attached a picture of my 40mm wide / 11um thick ribbons that seem closer to Soulsonic corrugation style. They also have resonances that can be heard with pink noise test and seen in measured frequency response.

Any tips where to get 40mm wide and about 8um thick alu foil?
My foil/film capacitors that have 8um foil are only 10mm wide.
Attached Images
File Type: jpg rib2.jpg (93.2 KB, 334 views)
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Old 11th October 2012, 08:56 AM   #30
hanski is offline hanski  Finland
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While waiting for the book to arrive, I took frequency response measurements from left and right channel ribbons. Below are unequalized ribbon responses.
The measurement mic was 10cm distance from ribbon.
Anyone care to comment about the ~2kHz resonance?

My differently corrugated ribbons all have this kind of high Q resonance. Only the frequency and amplitude varies. Ribbon tension affects to the resonance frequency and amplitude.
Attached Images
File Type: jpg channel l ribbon.jpg (66.0 KB, 301 views)
File Type: jpg channel r ribbon.jpg (67.8 KB, 289 views)
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