The surround is attached at the mode 0 inflection point and allows the pistonic component, so coupling it to the panel will be expected to affect that, but maybe the transfer to the panel will add to the overall bandwidth. That's the aim/hope anyway.. I'll just have to try to be clever about it and take a balanced approach (🤭).
Also, conceivably, it would/should be easy to use at least 2 drivers/panel, increasing the panel bending effect, and reducing the load on an individual BMR driver
Time and testing will tell as usual
Eucy
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Ok, I see where you're coming from.
Maybe the approach would be to glue an inertia ring where the surround would be (off-set from the edge of the radiator?) and thereby retain the mid/HF performance.
I would suspect in that case that the LF component of the signal would transfer to the panel.
Is that what you have in mind?
Maybe the approach would be to glue an inertia ring where the surround would be (off-set from the edge of the radiator?) and thereby retain the mid/HF performance.
I would suspect in that case that the LF component of the signal would transfer to the panel.
Is that what you have in mind?
Exactly that... maybe a full ring on the BMR with segmental attachments to the panel..
Yes. I read somewhere epoxy density is 1.1kg/l (1.1kg/dm³) so 110g/m² for 0.1mm thick.
Is it correct?
Are there rules of thumb about the glue thickness and some practical tricks to master the thickness and so the added weight?
In a recent test (I have almost no knowledge in resin or epoxy glue) I prepared a certain weight of epoxy glue, weight prepared knowing the surface and targeting the thickness (0.05mm?) then I apply the quantity on the whole surface. Is it the way to do it?
It could work for any glue.
An other question is : it was a 2 hours epoxy glue. Is this suitable according to the mechanical properties needed to glue a skin?
Christian
I do not agree that this is a horrible recording.
It is a very good recording of the church acoustics.
I have made many recordings in churches from my phone.
Mainly church organs , the sound is coming from everywhere, I love it.
I presume you want to increase clarity of speech, the spoken word.
The recording of the gregorian chant would normally have acoustic reverberation already in the recording, so you are getting a double whammy of reverberation ?
You can also hear the crickets or whatever they are in the background.
This is not a cheap horrible cell phone recording, but a recording of bad room acoustics.
Looking at how tectonic set up their panels ,they seem to only use two sets of panels or stacks to fill large areas.
Could this be to remove the delay line, which adding more spaced out panels will make it worse for intelligibility?
Especially for the people at the back?
Just a thought.
Steve.
HI Christian,
I also have rsther limited experience with resin, mainly because it eats the EPS that I usually work with, so I don't use it very much.
But I believe the rule of thumb is that whatever the weight of the fibre is, you need the same weight of resin to bind it properly to its substrate. This is probably because a heavier fibre is thicker and obviously needs more resin to embed the fibers in the binding agent.
This could be another good reason not to use CF, but rather a solid skin such as aluminum (or tracing paper?) which does not need to be fully embedded in a binding agent, but can be effectively glued down with a thin layer of adhesive.
For my next tests I might use ALU/EPS/ALU glued with epoxy resin (applied with a putty knife) or probably PU glue which expands to fill the gaps.
Solvent glues are just too difficult to work with.
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Seriously Andre... Unless you've successfully used this before I'd stay right away from it for this purpose. It'll expand as you say, but it generates significant force in doing so and will create air bubbles and push your surfacing away from the core unless it is severely and evenly constrained in a press
Eucy
Spedge, I never said it was a horrible "recording".
Regardless of the recorder's quality if you choose a horrible soundtrack, horrible room acoustics and horrible speakers it will equal horrible sound. 🤣🤣🤣
I totally agree with the Tectonics set up for PA application. Not just time delay but the more speakers you place around the room the more rear wall reflections, while less speakers around the room equals less room reflections its just common sense. Combine that with crosstalk cancellations etc you will lose voice intelligibility. PA is all about voice intelligibility. Placing speakers all around the room like its a movie theater is not the right application for PA. Instead the speakers should be in the front of the room. A single (can be stacked like line array) speaker placed in the front in the middle of the room will have the least amount of room reflections like my single (stereo) DML panel. A least you can see it Spedge, you would think Andre being into PA DML's would know this but I guess not. lol
Look at this tectonic vid using a SINGLE panel showing how far a DML's sound can travel while still maintaining great clarity/coherency.
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Agreed Eucy, it is a difficult problen to address. But I am using a press.
25W units:
I'm my experience the DAEX25Q-4 is okay. It obviously cannot handle as high power as the DAEX30HESF (40w driver), but seems to sound better. The 30HESF delivers a very aggressive midrange on lightweight panels.
DAEX25FHE-4 has a similar wide-band performance to the 25Q-4, but is theoretically more efficient.
40w units:
The DAEX32EP-4 Thruster seems to be a very nice sounding driver, but I have not used it yet in multiple configurations.
The MegaBass DAEX32QMB-4 does not deliver MegaBass on lightweight panels.
Maybe the 32QMB and the 30HESF have to be used on heavier panels for them to deliver acceptable sound, but because of such a heavier panel they will lose efficiency.
Bottom line:
For my next panels I'll be looking at 32EP-4 Thrusters, 25FHE-4's and 25Q-4's.
Has anyone tried Dayton's 8 ohm exciters?
Aramid fibres may have something to offer to improve the tensile properties of a panel. Tensile strength said to be better than glass along with an improved modulus.
Aramid fibres may have something to offer to improve the tensile properties of a panel. Tensile strength said to be better than glass along with an improved modulus.
I have not tried 8-ohm exciters because of their high inductance specs. I'm not sure that I want to waste money on a driver where I suspect beforehand that the HF is probably lacking.
In terms of tensile strength, I think CF is strongest, followed by Dyneema, and then Aramid/Kevlar.
But Dyneema is the lightest. So strength vs density puts Dyneema at the top.
Keep in mind that absolute strength is not the main priority for DML panels because the panels are not stressed to their breaking limits. It's elasticity that's important, Young's Modulus--stretch per unit force.
I have previously used 22g/sqm CF tissue, 50g/sqm Dyneema and 60g/sqm Kevlar as skins on three different 10mm EPS test panels with cold glue as the adhesive; But same as other experiments, the lighter the panel, the more efficient is the mid range, and only DSP EQ will flatten the response.
Of course, the orthogonal spring solution might also flatten the response at expense of efficiency, as usual.