Hello Hibren,
Very good questions and wording! Your questions sound close to mine. I appreciate reading about mechanical impedance and impedance adaptation. This is something in my knowledge in electronics, for the panel, I understand the principle but I have no idea about the possibility to make some measurements/tests to approach values.
The information that free FEM software can't model properly the edge termination is not a good news.
About measurements, any input to approach the peripheral suspension characteristics is welcome.
About the panel impedance, it is approximated in many paper as resistive but seems not true on all the frequency range. Here also more information welcome
Christian
"Professional tool with expensive add-ons", can you state what tools these might have been? As an engineering student I have access to a fair few programs for research purposes, definitely something I'd like to research, at least in my free time
Christian
One other odd way of centring a vented exciter is to mark the centre spot on the panel with a black marker 'spot' - then light it up from the side with a torch/phone, and having applied the glue or whatever, you can actually sight through the vent hole quite well, follow the exciter down with your eye (ala spyglass) and you will be able to get the hole on the marked dot.
Cheers
Eucy
Eucy.
With the vented exciters I would center them by using a thin wooden stick through the hole ( or anything none magnetic).
After applying the glue to the exciter foot You simply slide exciter down the stick into position, after obviously placing the stick on the centre dot.
Steve.
With the vented exciters I would center them by using a thin wooden stick through the hole ( or anything none magnetic).
After applying the glue to the exciter foot You simply slide exciter down the stick into position, after obviously placing the stick on the centre dot.
Steve.
Hi burntcoil.
Long time no hear.
I just got back from France yesterday and thought of you while I was over there, wondering which side of the channel you were on?
Do you still have dml projects going on ?
Steve,
These were at about 1.5 meters from each speaker and about the elevation of the exciters.
Eric
Hi Steve
Yep... Good idea... Are you up to trying a dome?... I'd like to hear your feedback 😁
Eucy
Christian,
Be careful not to draw such a broad conclusion.
The LISA FEM, for example, can model some types of edge terminations perfectly well, such as simple (hinged), clamped, or free edges, and also can model the addition of masses around the perimeter (or anywhere else). But there is indeed no facility for introducing and evaluating the addition of damping either at the perimeter or within the panel itself.
Eric
Perhaps something like this (no idea what it costs):
https://www.3ds.com/products-services/simulia/products/wave6/
as described here:
https://www.researchgate.net/public...zing_the_Off-Axis_Radiation_below_Coincidence
Eric
It's hard to do a good job making a nomex core with a wet layup instead of prepreg. I tried the method from the EC video myself but failed miserably. I think I used too little epoxy and the skins didn't really stick to the nomex.
But I also wonder if the cells in nomex are perhaps too large for a very thin layer of either CF or FG to avoid buckling of the skin on the compression side. That would lead to much lower than expected stiffness, and hence disappointing efficiency.
Eric
I did actually get the skins to bond, using a very minimal amount of epoxy as in the ES video. Stiffness seemed similar as when he shows trying to bend his plate.
It is very possible my plate could have been better, and it will be interesting to try the carbon to see how much it is the material or technique. But I think I will get some more fibreglass to practice with first since I haven't managed to make a whole complete plate yet.
Thank you for pointing this paper Eric.
Wave6 is from Dassault Systems. Among the products : Catia, Enovia, PLM... Basic tools for car, military, aeronautic industry.
Christian
pixel1,
You can actually just gently press the exciter (with the release film still covering the adhesive) to the panel with your hand. Another thing I've done is to orient the panel horizontally and place the exciter on top. Adding a bit weight on top (with a buffer of foam between) can help keep the exciter from bouncing.
What I've been doing lately, however, it to use an extra exciter as a test exciter. The test exciter is one that's been used before and no longer has the adhesive on it. I apply a thin double sided tape to the panel at the test position, and then attach the test exciter to the tape. It's easy to gently pry the exciter off the tape with a small putty knife. Often I apply the double side tape in a strip, and that allows me to test any position I want along the length of the strip.
Eric
pixel1
Somewhere back in my posts I describe my process
A strip of wide masking tape is applied to the panel, the exciter is then glued to the tape. The tape can be peeled off with the exciter and even repositioned without re-gluing (if you're careful)
Read back for a more detailed account
Eucy
hilbren,
Do you have an idea of what you plan to look for with the accelerometers?
I suspect that a microphone placed very close to the panel surface might give similar information as an accelerometer.
Eric
I use double sided tape as it is very quick and easy for instant measuring.
Not for long term use though.
The sound will be pretty much the same as using glue, but the HF tends to roll off above 10k.
I would be very careful about using this method on the lower grades of EPS ,as it would pull off the surface beads when removed .
The double sided tape will also slowly peel off with time, with the weight of the exciter pulling it down.
You might get a better HF response with the masking tape and glue method?
But with a longer waiting time for the glue to dry.
I do sometimes wonder whether the manufacturers use the double sided tape to dampen some of the noises in the coil area?
Some panel materials suffer more than others in this area.
Steve.
Eric.
Do you use the method of moving the microphone up and down and across the panel in peak hold mode , to get more of an idea of what the panel is putting out into the room, this can be done at various distances ?
I was curious about the HF dip in response above 10k with 2 speakers?
Steve.
Do you use the method of moving the microphone up and down and across the panel in peak hold mode , to get more of an idea of what the panel is putting out into the room, this can be done at various distances ?
I was curious about the HF dip in response above 10k with 2 speakers?
Steve.