The Sound of Shimmer

[Ron Resnick]

When I think of the sound of "shimmer" I think of the sound of gently bushed cymbals.

But some members refer to the "shimmer" of metal ribbon drivers as an undesirable artifact of the natural operation of a metal ribbon driver.

What is "ribbon cavity resonance"?

I do not recall this issue ever coming up before.

Please explain . . .

 

[cjfrbw]

Ribbons will more typically 'beam' and sometimes need a notch filter i.e. a filter that operates to reduce a particular frequency band.

Shimmer is an optical word applied to sound (visual and aural are connected by reflex pathways, no biggie) but I have always thought of it as not such a bad thing. Recorded high frequencies CAN shimmer, and if it is not there when on the recording, it implies harmonic truncation.

Ribbons are typically suspended free form in space, so the issue of 'cavity resonance' would have to be explained, since the cavity would be the room itself from what I can glean. This is the nature of dipoles and is not a bad thing when set up properly, as it can create a very deep image. Some tweeter foils are enclosed at the back, and could have cavity resonance I suppose.

 

[morricab]

When I think of the sound of "shimmer" I think of the sound of gently bushed cymbals.

But some members refer to the "shimmer" of metal ribbon drivers as an undesirable artifact of the natural operation of a metal ribbon driver.

What is "ribbon cavity resonance"?

I do not recall this issue ever coming up before.

Please explain . . .

ribbons can distort pretty heavily when used outside their comfort zone or when pushed really loud and perhaps this is where you start to get a "crinkly" sound like you hear when you scrunch up aluminum foil (basically what a ribbon is made from). True ribbons that are backed with plastic (mylar or kapton) seem to have a wider range without this "breakup" sound...like Apogee or Alsyvox ribbon mid/tweeters. That being said the orignal Apogee Full Range and Scintilla used pure metal ribbon mid/highs and didn't sound particularly metallic (but sometimes I thought I heard a hint of it). Small ribbon tweeters can typcially not be used very low or they will sound distorted. A large ribbon can go down to a few hundred Hz and sound very very good but I am not sure how low the absolute distortion is.
I have some BG planar drivers that have a cavity resonance that is a function of the design of the housing/magnets around the planar magnetic driver...it requires a notch filter to remove it (recommended by BG). For a true ribbon, I am not sure how applicable this term is...but there are still semi-enclosed spaces around the ribbon and the gap between the ribbon and the magnets that could create a kind of "cavitation" effect that resonates...it is not the driver itself resonating but a cavity (like the body of an instrument) in the design of the whole driver.

 

[bonzo75]

Does shimmer have jump factor?

 

[morricab]

Does shimmer have jump factor?

The impact on a cymbal will be have a different frequency/dynamic envelope than the "shimmer" of the cymbal decay...the jump is likely to come from the impact not the decay...

 

[Audiophile Bill]

I played around with two vintage (different) ribbon tweeters of late - both had a metallic colouration that was easily discernible and did not blend well with the paper cone driver below it.

My opinion (fwiw) is that all driver materials and cabinets can be heard.

 

[Zero000]

or a true ribbon, I am not sure how applicable this term is...but there are still semi-enclosed spaces around the ribbon and the gap between the ribbon and the magnets that could create a kind of "cavitation" effect that resonates...it is not the driver itself resonating but a cavity (like the body of an instrument) in the design of the whole driver.

The true ribbon part of Apogees are surrounded by a very hard reflective surface i.e. the magnets themselves. I did try to put a thin self-adhesive foam layer on top of the magnet surface to see what effect some damping would have.

I chickened out when I started to try and do it. It really needs to be done before ribbon install. If at all.

The back aperture on mine are horn flared. Not like a standard Duetta. It's really interesting the effect that has. I seriously think the front aperture on Duetta should have been more flared. Mine are, but not to quite the same effect as the rear.

 

[Zero000]

I played around with two vintage (different) ribbon tweeters of late - both had a metallic colouration that was easily discernible and did not blend well with the paper cone driver below it.

My opinion (fwiw) is that all driver materials and cabinets can be heard.

I agree. Which leads you to the conclusion that you want the same driver material for the full frequency range. Full range ribbons and electrostatics satisfy that.

Material disparity causes issues that reduce the coherence of a speaker and that's confirmed with what you heard.

Kapton or mylar damping of the foil has to reduce metallic colouration but some trace is there.

 

[cannata]

A typical application:

 

[Audiophile Bill]

I agree. Which leads you to the conclusion that you want the same driver material for the full frequency range. Full range ribbons and electrostatics satisfy that.

Material disparity causes issues that reduce the coherence of a speaker and that's confirmed with what you heard.

Kapton or mylar damping of the foil has to reduce metallic colouration but some trace is there.

Yes exactly, Justin.

 

[cannata]

The difficulties of integration have more to do with drivers dispersion pattern (cylindrical vs. spherical), then drivers materials (although that is a factor as well). For best integration, you should stick to the same type of drivers typology and material.

 

[marty]

A typical application:

View attachment 55017

Wow, this seems like a weak attempt to correct sonic deviation that may create more problems than it solves. There is no question the reactive impedance of the driver is altered, which means the crossover parameters must necessarily be altered as well. It may have a sonic benefit, but it is also possible it has unanticipated sonic consequences that are less than ideal. As usual, the sonic results should be one's guide, but this is hardly an elegant approach.

 

[Zero000]

The difficulties of integration have more to do with drivers dispersion pattern (cylindrical vs. spherical), then drivers materials (although that is a factor as well). For best integration, you should stick to the same type of drivers typology and material.

Everything is a compromise and has flaws. You just have to choose the flaws you prefer.

 

[cjfrbw]

Wow, this seems like a weak attempt to correct sonic deviation that may create more problems than it solves. There is no question the reactive impedance of the driver is altered, which means the crossover parameters must necessarily be altered as well. It may have a sonic benefit, but it is also possible it has unanticipated sonic consequences that are less than ideal. As usual, the sonic results should be one's guide, but this is hardly an elegant approach.

Here's the notch filter clump for BG ribbons to bring down the 5k beam.

 

[NorthStar]

That's a cool looking notch.

 

[Folsom]

Wow, this seems like a weak attempt to correct sonic deviation that may create more problems than it solves. There is no question the reactive impedance of the driver is altered, which means the crossover parameters must necessarily be altered as well. It may have a sonic benefit, but it is also possible it has unanticipated sonic consequences that are less than ideal. As usual, the sonic results should be one's guide, but this is hardly an elegant approach.

Nonsense. This fear has less legitimacy than anti-vaccination concerns. Any speaker designer knows exactly what it does to the response, and anyone that knows anything about how electricity works can tell this is no more a "problem" than a single order capacitor in any given speaker.

What doesn't make sense is listening to a stereo with a huge resonances in the tweeter region because it's migraine, teeth grinding, aneurysm inducing painful to listen to.

 

[Folsom]

BTW certain BG tweeters can be made to have much better response by threading the outside sides with some yarn. Danny Richie figured this out and use to order them with a material pre-applied, but BG got bought out and now they're a pain to deal with so you have to do your own. The response is just much better.

 

[jeff1225]

I once knew a stripper named Shimmer.

 

[NorthStar]

Was she "notchy"?

 

[Folsom]

Should this topic maybe have something to do with sibilance?