Usually/commonly the glue used is urea formaldehyde, which is a hard glue and therefore helps with the hf
Other common types are phenolic resin (phenol/formaldehyde) and melamine, both of which a hard types.
PVA and similar home user glues are to soft to give a good result I believe
Eucy
Hello Christian.
If I remember correctly, the instructions for pva says that at least one surface should be porous to allow the water to escape.
Gluing the exciters onto aluminium seems to work because the exciter foot is so thin, and I use a hair dryer to help it along.
It still takes about 5 days or more to fully harden to produce hf above 10k.
Keeping the panel warm helps.
Gluing a high density 5mm eps sheet to a 40cm aluminium sheet was not a good idea.
it turned the eps into a heavy damping layer.
it was a waste of a good eps panel.
i think i used evo-stik for that panel ?
Steve.
If I remember correctly, the instructions for pva says that at least one surface should be porous to allow the water to escape.
Gluing the exciters onto aluminium seems to work because the exciter foot is so thin, and I use a hair dryer to help it along.
It still takes about 5 days or more to fully harden to produce hf above 10k.
Keeping the panel warm helps.
Gluing a high density 5mm eps sheet to a 40cm aluminium sheet was not a good idea.
it turned the eps into a heavy damping layer.
it was a waste of a good eps panel.
i think i used evo-stik for that panel ?
Steve.
Thank you Eucy. Some months ago, I made one. The distance being, better I make a new one...
Hello Christian.
You mentioned earlier about bending waves and reflected waves.
Are you taking into account the direct radiated sound from the coil area.
This area is a pulsating sphere area, and acts similar to a cone speaker on a open baffle.
The size of this area changes depending on panel weight and stiffness.
With My 1inch x4ftx4ft panel most of the sound seemed to be coming from the exciter area as it was louder.
The panel rolled off at about 10k but the exciter area is capable of reaching 20k if care is taken.
I have shown pictures of my 7ft panels demonstrating this.
The blending of the direct radiated sound with the defuse sound of the panel will modify the response to some extent.
Do your measurements take this into account?
More interesting to me would be the response from one side of the panel from front to back.
The back left side should be a mirror image of the front left side, but with the exciter being an interference.
Also are the high peaks for 80° coming from the panel or the exciter area, probably both .
I removed a large peak above 10k from one of my 3mm ply panels using blu-tack , i believe, but found the panel as a whole was still producing the above 10k peak.
All the best .
Steve.
You mentioned earlier about bending waves and reflected waves.
Are you taking into account the direct radiated sound from the coil area.
This area is a pulsating sphere area, and acts similar to a cone speaker on a open baffle.
The size of this area changes depending on panel weight and stiffness.
With My 1inch x4ftx4ft panel most of the sound seemed to be coming from the exciter area as it was louder.
The panel rolled off at about 10k but the exciter area is capable of reaching 20k if care is taken.
I have shown pictures of my 7ft panels demonstrating this.
The blending of the direct radiated sound with the defuse sound of the panel will modify the response to some extent.
Do your measurements take this into account?
More interesting to me would be the response from one side of the panel from front to back.
The back left side should be a mirror image of the front left side, but with the exciter being an interference.
Also are the high peaks for 80° coming from the panel or the exciter area, probably both .
I removed a large peak above 10k from one of my 3mm ply panels using blu-tack , i believe, but found the panel as a whole was still producing the above 10k peak.
All the best .
Steve.
Hello Steve,
Not clear in my mind for now. I would say that the bending waves are what you put under the direct radiated sound
One explanation for the extension is the "drum effect". The central area limited by the voice coil as its own resonance. The diameter being similar to the usual dimensions of a tweeter, there is a possibility it radiates from the axis to a wide angle. In the measurements, it seems linked also to the coincidence frequency. Is it a coincidence or something not explained?
The measurements are at 1m from the panel. They can't identify the source or the type of sound arriving.
Sorry but I don't see your proposal. A drawing? For the next measurements, I think to make them along the full circle on 360° and not only a half one.
A single measurement can't explain the origin. As you propose some additional measurement with a counter-measure against the vibration of the central area can give more clues. On the PS panel for example, the central area was stiffened to eliminate the drum effect.
I have measurements not shared for now where I stuck a rubber cylinder at the axis on the front face. It is rubber seal for tap. It is almost the voice coil diameter and a mass of 1g. The goal was to modify the behavior of this area and also to see what is the influence of an additional mass (1, 2, 3g...). This need a bit more work to be shared.
Christian
aagas, can you please provide the thickness of the aluminum on your aluminum composite panels?
I have the history file of this thread just open on my laptop. See from post #2688 for dimensions, drawing.
The panel thickness is 3/8" (9,5mm) @aagas : correct? The aluminum foil thickness is not in the file but the overall weight is : 13lbs each (what is in the file :
70 3/4" high x 20 1/4" wide (1,80 x 0,51m) 3/8" (9,5mm), aluminium honeycomb 4.53kg/m²
@spedge : Steve, going to the area of the posts, #2688, I see you wrote that the Podium panel is for you in the heavy panel. On my side, I have 0,44kg/m“ for Podium (I don't remember what was the source...) where a plywood 3mm will more 1.5kg/m². Do you remember your source?
Christian
Thanks Christian. Since we've been discussing alternate ways of making a composite aluminum panel, I'd like to start with the aluminum thickness that aagas has, since he has been very pleased with them. Steve, how thick was the aluminum that you bonded to the 5 mm EPS? Was it too thick, given the poor results?
Hello,
Here is a new version of the previous directivity test document : some wording change (directivity plot instead of spinorama) and more links about spinorama/directivity.
Christian
Here is a new version of the previous directivity test document : some wording change (directivity plot instead of spinorama) and more links about spinorama/directivity.
Christian
The aluminium thickness was 0.5mm and the eps was a high density panel.
Maybe I should have tried gluing a second sheet of aluminium on either side of the eps to make a sandwich panel.
This would have improved its performance but my exciters would not have driven them well enough.
This would have been too heavy for my liking as well.
Similar to the podium sound I would think 🤔
By the way, The sound of the podium panels is very good , excellent even.
But heavy panels have a certain sound that might be improved by the addition of a ribbon tweeter or maybe the thin film layer I was experimenting with.
Steve.
I don't know and have no way to measure the thickness of the panel skins. That did given the tensile strength of aluminum, I've recommended using the thinnest possible aluminum skin that isn't foil. Something you can't crumble up in your hand.
Steve,
Yeah, at least from an efficiency/sensitivity perspective, the strategy that makes sense would be to try aluminum on both sides, to create a light, stiff panel. What benefit were you hoping for by gluing the aluminum on only one side?
Eric
Steve, I think 0.5 mm is too thick. A beer can is 0.1 mm. I think the paint/ink on the outside of the can would suffice as a primer coat (scuff it a little). I agree that a sandwich panel would be best.
Bruce
Eric.
I had no strategy.
The panel was too heavy and wobbly.
So i replaced the second aluminium plate with the eps.
this made the panel lighter and more rigid.
I ended up with an over damped panel.
the glue i used added more weight and damping to the panel.
adding a second sheet of ali would have made the panel even heavier.
it was a failure and i moved on.
Steve.
Hello Christian.
The sound from the exciter area will be far louder than the rest of the panel and will be full range.
This area acts in the same way as a full range cone driver.
Except that the edge of the cone area is connected to the panel.
Using the stone in the pond analogy.
The large splash in the middle is the direct radiated sound and the smaller ripples are the travelling waves moving through the panel.
The drum effect is a distortion in the centre of the coil area causing peaks and dips in the hf frequency response depending on the size of coil.
How you would remove this distortion would depend on the panel material being used.
For me it would be interesting to see the 0° point at the edge of the panel with the + 90° in front of the exciter coil.
And the -90° point behind the exciter.
How similar would these two sides be on the plots.
They should be identical, but in reality they will not because of the exciter mounting.
When I measured an eps panel that was beaming heavily to the walls I held a large cushion close to the panel to prevent the centre radiation going to the wall and microphone.
This blocked the peak in the response.
Putting the cushion on the wall next to the panel stopped this peak being reflected back from the wall to my seating position.
No more ear ache 👍
Steve.
I'm tempted to try the new Xcite XTB40 160w bass exciters, on sale atm. It does look like it then becomes a 2 way panel system as they don't play 1000Hz up. Also thinking if the panel is being used for bass as well the room placement may be less flexible as it's basically an open baffle woofer with the rear wave cancelations etc.
JoskaNZ
Some of my panels can go down to 40hz using my 10watt exciters no problems as long as they are not pushed too hard.
Some music has very strong loud bass.
The problem is going to be finding a panel that can handle being shaken so hard Without loosing control.
It would be nice if the manufacturer showed the exciter working on a panel that could handle that amount of power.
They must have tested this ?
Steve.
Some of my panels can go down to 40hz using my 10watt exciters no problems as long as they are not pushed too hard.
Some music has very strong loud bass.
The problem is going to be finding a panel that can handle being shaken so hard Without loosing control.
It would be nice if the manufacturer showed the exciter working on a panel that could handle that amount of power.
They must have tested this ?
Steve.
Hi Steve,
Yes if they showed their test panel and suspension it would help get a better idea of how they come up with the response data.
I have also made canvas panels that can play to 40Hz but as you say they get noisey when pushed to higher SPL especially in the bass. I guess the bass requires more pistonic motion like a normal speaker so it comes down to the suspension of the panel more.
Yes if they showed their test panel and suspension it would help get a better idea of how they come up with the response data.
I have also made canvas panels that can play to 40Hz but as you say they get noisey when pushed to higher SPL especially in the bass. I guess the bass requires more pistonic motion like a normal speaker so it comes down to the suspension of the panel more.
Steve
I'm struggling to understand this statement.
Are you saying that some of your panels will produce 40hz at a level consistent with the other frequencies and therefore be usable at full range?
If so you have achieved the holy grail.