No one side only. I use a water based universal glue from casco to glue it to the panel.
Going back reading old posts, you find some pearls, such as this, Analysis of Flat Panel Speakers.pdf
an excerpt,
an excerpt,
Reading Glenn E Warnaka patent of 1966 you linked, I noticed,
and, reading the underlined words brought a smile. Remembering the developing of the 'transverse technology'...
Smiling aside, Warnaka is very thorough.
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I've always wanted to hear these speakers in person but they are super rare. https://www.audioexchange.co.za/technics-sb-afp10/
So there is always youtube.
So there is always youtube.
Glenn E Warnaka thoughts. From the patent kindly linked by Veleric. #8,377
- Thus, the most important characteristic of a panel for sound radiation is not its overall bending stiffness, but the bending stiffness of its cross section.
- At some excitation frequency the bending wave length will exactly equal the trace wave length (or projected wave length) of the exciting wave. This means that a crest of the exciting wave will exactly coincide with the crest of a bending wave, and the transverse bending Wave speed equals the speed of sound in air.
- At this condition, all the energy of the exciting wave, except for that small portion lost by damping in the panel and at the edges of the panel and by reflection, will be transferred to the bending wave.
- The lowest frequency for which this wave coincidence can occur is called the critical frequency.
- When wave coincidence occurs, the panel becomes transparent to the exciting wave.
- The transmission loss through the panel drops to a very low level, and the exciting wave may pass through the panel readily and be efiiciently radiated from the other side as a sound wave.
- The loudspeaker makes use of the efficient coupling between transverse bending waves and sound waves in air which exists at and above the critical frequency of the panel.
- The critical frequency of the panel should be adjusted to be the lowest bass note to be produced by the speaker for best results. However, acceptable results can be obtained with some loss in efficiency if the critical frequency is in the low bass range but is somewhat higher than the lowest bass note to be produced. In this case, fairly efficient coupling can still exist even if the transverse bending wave speed is slightly below the speed of sound in air.
- The critical frequency of the panel may be adjusted in two ways. First, different critical frequencies can be obtained by changing the square root of the ratio of the mass of the panel to its bending stiffness. Secondly, the voice coil and magnet assembly can be set at different angles to the panel. In this way, the trace wavelength can be changed and different critical fre quencies will be produced.
- In order to reproduce the lowest bass musical notes, the ratio of the mass of the panel to its bending stiffness should be as small as possible.
- Lightweight honeycomb panels and panels employing similar spacing type cores as well as rigid plastic foams which have very low mass and high stiffness are well suited for use in this type of loudspeaker. Any type of panel construction used should, of course, have low internal damping to insure maximum efficiency.
- Conventional cone and piston type speakers to produce sound, they must be capable of rather large motions, particularly at low frequencies, to be efficient sound radiators.
- With the wave coincidence type of radiator, however, the panel must be stationary on the average in order to function properly. That is, the panel must not undergo any appreciable overall motion or its performance will be degraded.
- Ideally, the only movement of the panel should be the distortion of the panel cross section due to the transverse bending waves. To the extent that the impulses from the voice coil cause the entire panel to move uniformly in a pumping action, the energy will be taken away from the bending waves.
- There are two basic types of edge termination which will prohibit overall motion while permitting the proper cross-sectional distortion to occur. The most obvious is a rigid clamping method. In this case, the inner and outer peripheral edges of the panel are bolted or cemented to a rigid frame.
- In the modification, the panel is supported by a soft elastic suspension. In this case, the natural frequency of the suspension should be much lower in frequency than the lowest frequency to be produced by the radiator. The panel would be well "isolated' and would not be influenced by the motion imparted by the voice coil.
- In this modification, brackets are attached to the corners of the skins, and are connected to the supporting frame by soft springs. The natural frequency of such a suspension would be only a few c.p.s. This is so "soft' that the panel could be easily displaced by external disturbances.
- Large displacement of the panel would degrade the performance of the loudspeaker, and damage the magnet and voice coil assembly. With the soft suspension, other common methods for guiding voice coils could be used.
- In the case of the rigidly attached panel, no special guiding is necessary, since the panel is stiff enough to locate the voice coil relative to the magnet.
- Of course, it is also important that the edge termination used does not add significant damping to the system which would tend to attenuate the bending waves.
- It is not necessary that the dimensions of the panel be as large as the lowest sound waves to be radiated. The important characteristic is the low ratio of the unit mass to the unit cross sectional stiffness.
- The panel doesn't have to be flat. It is only desired that the shape of the speaker introduce no discontinuities or sharp bends which would tend to produce large reflections, attenuations, or distortions of the bending waves.
Sandasnickaren,
Just a regular sound Wav file I use the REW RTA to do the harmonic analyzes.
Again Many thanks in advance.
Cheers
Yep, first he said "modal behavior isn't just fine, it's great!" and then later, "oh yeah, it's even better if we eliminate modes, by the way" Fun, fun fun!
Eric
To be clear, the understanding of transverse bending waves in plates goes back at least to Love in the 1890s, but the dubious "invention" of transverse waves in gasses is much more recent!
Eric
My own suspicions were confirmed when Audiofrenzy mentioned Bertagni.Sure, @spedge is the sharpest here, and he was right!
Veleric mentioned "I've used that too (Frost King). You may even have suggested it to me!" That reminded me, who was writing about Frost King Weather foam in the early days here.
Eric
I was thinking of getting a more powerful exciter for the 6mm proplex panel.
I want to see how it will perform with the right amount of power.
But are there any good sounding powerful exciters that can reach 20k ?
And I mean flat to 20k, not minus 10db or more.
I might have to use 2 or more of my 10watt exciters if none are available.
And do I go along the flutes or across them or go from corner to corner.
I'll have to test using double sided tape.
Steve.
I want to see how it will perform with the right amount of power.
But are there any good sounding powerful exciters that can reach 20k ?
And I mean flat to 20k, not minus 10db or more.
I might have to use 2 or more of my 10watt exciters if none are available.
And do I go along the flutes or across them or go from corner to corner.
I'll have to test using double sided tape.
Steve.
Proplex is stiff only on one direction, on th eother, you can just break it. Best find a honeycomb sheet, which would be stiff on both directions.
They only have cellular polycarbonate, not exactly honeycomb. Is yours cellular as in the image above?
"In gasses" is most probably to hoodwink the patent reviewer(s).
I'm sure the Herger patents would stay in the application state in US forever.I doubt it. If somebody wants to waste money patenting a useless idea, I'm sure the US patent office will be happy to take it. Plus I doubt that patent attorneys were ever really obliged to understand the technology to that extent. And modern wage slavery being what it is, the attorneys probably don't even have time to read the patents."In gasses" is most probably to hoodwink the patent reviewer(s).