Mylar backed ribbon trace pattern.

Jump to Latest
H

hellokitty123

Member
Joined 2017
#1
I've spent the last week or so messing around with ribbons after buying some .5 micron mylar, a bunch of silver leaf, and a number of kitchen foil ribbons I etched down from sodium hydroxide.

I'm trying to make relatively small a nearly full range desktop speaker.

I've noticed that mylar backed silver leaf is noisy below 1k due to having no stiffness it just "crinkles".

Etched kitchen foil is either too stiff and has resonances that are seemingly nigh impossible to remove or it's not stiff enough and becomes noisy in the low frequencies.

I use a fine embosssing pattern combined with 1mm wide and deep spring corrugation.


I tried putting 3 strips of etched corrugated ribbon on silver leaf backed mylar to add some structure to the mylar backed silver leaf but the mylar noise still just crinkles away anywhere it is exposed.


I recall someone telling me once that I should put traces on mylar backed ribbon to damp resonances, meaning there is a way to do it without noisiness.

What sort of trace pattern do ribbons use exactly? I spent a couple hours looking and could only find AMT patterns.

My mother has a one of those shillouete cameo things so I could use that for tracing.

Thanks and appreciated. 🙂
 
#2
Most of the quasi-ribbon designs use tensioned Mylar (or whatever film type). The free span, mass, and degree of tension determine the resonance frequency of the membrane.

Is your Mylar 1/2 mil or 1/2 micron? Typically, electrostatics and planar magnetics use between 3 and 12 micron film.

If you were doing a very low mass ribbon for high frequencies only, a minimally tensioned very thin film/foil combination is more desirable.

If you're trying to do a more full-range design, a thicker diaphragm with higher tension is typical.
 
#4
I have .5 micron and 3 micron mylar and the 3 micron is much more noisy than the .5 micron at low frequencies.
My main issue is that either mylar sounds like shaking a plastic bag at low frequencies when used with ultra thin foil or with strips of foil and if I tension the plastic bag sound away then it resonates like a drum.
Clearly people use mylar so I must be doing something wrong.

Also the patterns in the threads you linked seem to be flat coils. How does it work when the current is not flowing 90 degrees from the magnetic field in the same direction?
 
Last edited:
#5
Resonating like a drum is what you get with an undamped, stretched membrane. If you look at most of the commercial designs, they typically take one of a few approaches to deal with it: 1) frequency limiting them to a band away from resonance, 2) distributing resonances so they are more pleasing, or 3) adding damping to suppress resonances.

I'm not sure what you're asking about on the flat coils. The north and south poles of the magnets alternate and the conductive pattern ensures that the field orientation is proper for each gap. The cutaway view on the Magnepan site shows the basic magnetic circuit.

Magnepan

The top and bottoms where the circuit returns run doesn't have much impact since the stray magnetic field is minimal compared to the intended gap.

Another speaker you may be interested in seeing is the Sonigistix Monsoon desk speaker, which is similar to what you seem to be shooting for. It also includes a damping pad on one side of the diaphragm. This is an acoustic resistance device (not in contact with the diaphragm).

I fixed buzz in Sonigistix Monsoon planar magnetic drivers
 
Last edited:
#6
I used a construction method involving non-stretching kapton tape as the main diaphragm and stretch wrap as a surround of sorts. I have home and desktop versions that have been working well for several years so the construction seems to hold up well. The frequency and Q of the fundamental resonance are low enough so that they are not problematic.

Link: here

Few
 
#8
Perhaps the link was killed by my iPad as I created it. I’ll paste it again below, but if it’s still problematic you can search on diyaudio for diy planar magnetic etc. as shown in the url below:

DIY planar magnetic + open baffle woofer array

The kapton tape is largely covered by the aluminum traces and has adhesive on one surface, so the combination leaves a pretty quiet result. If I wave a free diaphragm in the air by hand there is no crinkling sound. The stretch wrap surround probably contributes as well.
 
#10
Interesting. I guess kapton doesn't make sound at 13 microns or is it a kapton thing in general?
How is it that a 13 micron diaphragm sounds good?
As far as I've heard, anything over 7 microns seems to sound quite noticeably worse and anything hovering around 1 micron sounds best.

I'd like to hear your opinion.

Also can you explain this "surround"? I don't quite understand it.
Thanks.
 
#11
To the long edges of the Kapton tape I adhered stretch wrap which connects the kapton diaphragm to the rigid frame (sort of like the surround of a woofer). The kapton doesn't stretch. The surround makes it easier to put some tension on the diaphragm without driving the fundamental resonance higher than I wanted it (I run the planars down to 200-300 Hz).

Semi-quantitative "rules" about diaphragm thickness and sounding good or bad are a bit too simplistic, for my taste. There are many variables at play and things don't suddenly sound good, or bad, when some thickness threshold is crossed. I use my planars for tweeter and midrange duty and their perceived sound and measured performance are both what I classify as "good." But this is DIY so clearly you should do whatever floats your boat. I would never argue anyone should do what I did; just sharing in case it's helpful.

Few
 
You must log in or register to reply here.
Top Bottom