Hello Trenth.
No I do not like to damp the sound of the panel's I listen to.
I built the rigidly mounted ply panels about 15 years ago.
I struggle to call these panels damped, as the rigid mounting does the opposite.
The rigid mounting actually increases the loudness of the panels.
It is my impression that rigid mounting increases the strength of the reflections from edges of the panel.
My small 10watt exciters struggled driving the unmounted 6ft panel to ordinary volumes, but were fine driving the rigidly mounted panels without overheating.
Eric has noted that his foam mounting increases the low frequencies but rigid mounting increases the sound of the whole panel frequency response as shown in my posts of the panel responses.
I did try using a smaller panel size but it started to sound very glassy and hard similar to the sound in an indoor swimming pool .
I have mentioned to Christian that it is not easy trying to stop a 3mm 6ft panel from moving once you have set it in motion.
Especially at a low frequency drum mode.
I used angled Cross braces to break up these modes , similar to not having parallel sides, which worked quite well.
But the frequencies still have to travel their path.
Holding my hand on the panel does also help reduce these reflections.
Best not to excite those frequencies in the first place, so a higher xo is my answer to that problem.
Steve.
No I do not like to damp the sound of the panel's I listen to.
I built the rigidly mounted ply panels about 15 years ago.
I struggle to call these panels damped, as the rigid mounting does the opposite.
The rigid mounting actually increases the loudness of the panels.
It is my impression that rigid mounting increases the strength of the reflections from edges of the panel.
My small 10watt exciters struggled driving the unmounted 6ft panel to ordinary volumes, but were fine driving the rigidly mounted panels without overheating.
Eric has noted that his foam mounting increases the low frequencies but rigid mounting increases the sound of the whole panel frequency response as shown in my posts of the panel responses.
I did try using a smaller panel size but it started to sound very glassy and hard similar to the sound in an indoor swimming pool .
I have mentioned to Christian that it is not easy trying to stop a 3mm 6ft panel from moving once you have set it in motion.
Especially at a low frequency drum mode.
I used angled Cross braces to break up these modes , similar to not having parallel sides, which worked quite well.
But the frequencies still have to travel their path.
Holding my hand on the panel does also help reduce these reflections.
Best not to excite those frequencies in the first place, so a higher xo is my answer to that problem.
Steve.
"rigidly mounted" meaning screwing the plywood directly to the frame here? Is this the setup you're talking about?
I think I will get some thinner plywood (mine is currently a 2' by 4' sheet of 1/4 inch thick, which is too big and heavy I think) and I'd like your tips on building the best ply panel I can.
Interesting Steve- The attached FR graph shows a 900x600x3mm ply panel (can't go above 1m with the software at present) with both SSSS and CCCC mounting (blue is free, purple rigid) and a 5W input. PeTTaLS doesn't reflect an increase in volume beyond 1kHz, with a very lumpy response below that. The same goes for 10W input.
Eucy
Hello Trenth.
Yes , I would also glue the panel as well, I did not do this for my panels as it was an experiment, I'm afraid the ply 6ft panel does suffer from buzzing at low frequencies.
I made a video for Christian the other day and I had to turn the 6ft panel upside-down as it was suffering from exciter sag , not surprising as it has been standing in the corner for some years , this sorted exciter buzzing but not the loose joints 😀.
I also noticed this post of mine on this same page.
It shows how I removed the hf peak from the central exciter coil area using paper strips, the hf now looking good up to 20k.
But the panel itself was still radiating the large hf hump above 10k in all directions.
But the tape did improve clarity and detail of the sound coming from this central area.
So it is not just about reducing the hf peak.
Steve.
Hello Eucy.
I was relaying the sound I could hear between the unmounted panel and the clamped panel.
How this would show up on your computer simulation I do not know.
The unmounted ply panel response was smoother than the mounted panel ,if I remember correctly , which was annoying, but the added presence to the sound was worth this.
I also used weights to remove some of the suck outs and deviations on the 3x2 ft panel.
All those weights(AA batteries) have fallen off over time as they were held on with blu-tack.
It is easy to alter the sound of this panel by placing my thumb on the panel in certain places, spreading the sound from the exciter area to where my thumb is.
I may make a youtube video of this but I am not sure how well it will come across on the video.
Steve.
I was relaying the sound I could hear between the unmounted panel and the clamped panel.
How this would show up on your computer simulation I do not know.
The unmounted ply panel response was smoother than the mounted panel ,if I remember correctly , which was annoying, but the added presence to the sound was worth this.
I also used weights to remove some of the suck outs and deviations on the 3x2 ft panel.
All those weights(AA batteries) have fallen off over time as they were held on with blu-tack.
It is easy to alter the sound of this panel by placing my thumb on the panel in certain places, spreading the sound from the exciter area to where my thumb is.
I may make a youtube video of this but I am not sure how well it will come across on the video.
Steve.
I am probably not the best person to guide you on ply panels as they are not my favourite material.
1/4 inch is a little thick for a dml panel, my 10watt exciters would have trouble driving it.
The more robust Aliexpress exciters I believe drive thick panels better.
I have the 5mm panel with an Ali express exciter attached, I could post this also on YouTube if you wish to have a look and listen .
Steve.
Trenth.
I just remembered a very thin 1.5mm 6ft x 2ft offcut that I demonstrated to Christian on a WhatsApp video.
It was a 2ply with both grains going down the panel length.
It could not support itself properly.
But I did make a couple of good recordings of them.
I was very impressed with the sound of this panel.
So I do , come to think of it, actually like the sound of very flexible ply panels.
They have a very lively horn loaded sound to them, unlike the 5mm ply panels.
I even bent them over into a dome while I was playing music, the trouble was that I over did it and it split 😃
This was me just playing around with different materials.
I Don't think I can send the videos to youtube because of copyright .
Sorry.
Steve.
I just remembered a very thin 1.5mm 6ft x 2ft offcut that I demonstrated to Christian on a WhatsApp video.
It was a 2ply with both grains going down the panel length.
It could not support itself properly.
But I did make a couple of good recordings of them.
I was very impressed with the sound of this panel.
So I do , come to think of it, actually like the sound of very flexible ply panels.
They have a very lively horn loaded sound to them, unlike the 5mm ply panels.
I even bent them over into a dome while I was playing music, the trouble was that I over did it and it split 😃
This was me just playing around with different materials.
I Don't think I can send the videos to youtube because of copyright .
Sorry.
Steve.
Below are extracts of my paper about directivity showing the plot of the different plywood I tested.
First is 5mm in both directions, along and across the grain. A strong radiation in all directions is visible but much above 10k
Below are 2 different 3mm poplar plywood, both across the grain. A peak is here also but with less level around 45°.
Next is a 2mm basswood. The peak is lower
It might be in the family of what you have detected.
Christian
Is it also what we can conclude from the directivity plots? In my opinion, yes.
Christian
I'm sorry, I don't have the necessary knowledge to interpret these results. Could you help me understand a little bit?
Those heatmap visualizations, what do warmer and cooler colors represent? Is a warmer color representing places of the panel that move more?
That SPL graph - is the ideal graph a flatter one?
Those heatmap visualizations, what do warmer and cooler colors represent? Is a warmer color representing places of the panel that move more?
That SPL graph - is the ideal graph a flatter one?
The colored maps are directivity plots. They show the SPL at different angles (usually we see only the on axis SPL). Horizontal axis is the frequency, vertical is the angle with 0° the on axis, 180° being full rear. The color is the SPL level. The graduation is from low to high SPL dark blue, blue, green, yellow, orange, red.
So orange to red areas show peaks according frequency and direction of radiation.
The 5mm and 3mm plywood were not measured from the rear side so the plots stop at 90° (full left and right).
Maybe I should have remove the plot below. The curve LW20 is the average value of +/-20° window so almost the on axis.
Christian
PS : the 2mm measurement was probably "corrupted" by a too large spine... which would explain it is not as smoothed as the 3mm on the left. It is something I understood after those measurements. The 3mm on the right is from my current plywood panel with a full foam surrounding suspension.
Finally, I just managed to upload pictures of my 1.5mm panel.
I am still having problems uploading pictures.
In the last photo you can clearly see the split (crack) in the panel created by over bending the panel.
I picked this up free from my local DIY store .
It is probably the inner core of a ply panel that was used for packaging.
Steve.
I am still having problems uploading pictures.
In the last photo you can clearly see the split (crack) in the panel created by over bending the panel.
I picked this up free from my local DIY store .
It is probably the inner core of a ply panel that was used for packaging.
Steve.
Attachments
I went mad and posted the 1.5 mm panel I recorded for Christian, I'd look quick as it could be copyright protected!.
Listen using good headphones.
Steve.
Listen using good headphones.
Steve.
The copyright is OK, so hopefully this will be too.
Thanks Steve, for sharing. As a matter of interest - you experiment with such a diverse collection of different panel materials and sizes - how do you determine the exciter position for each panel?
So, is a more desirable full-range panel one with a balance of red and blue areas?
These make sense, the biggest weakness of my current 1/4 inch panels are the highs for sure - they have decent low end actually but seem to seriously lack body and the sparkle. I will do a thinner speaker setup soon.
Also, that wider panel appears to have a greater range of SPL, can I interpret this as being more balanced?
These make sense, the biggest weakness of my current 1/4 inch panels are the highs for sure - they have decent low end actually but seem to seriously lack body and the sparkle. I will do a thinner speaker setup soon.
Also, that wider panel appears to have a greater range of SPL, can I interpret this as being more balanced?
As a result of my Long Term Interest in Densified Wood Board Material, I was also learning about the delignifying process carried out on Wood to allow for a material to be produced that can undergo much more compression as a material.
The above led me to my becoming aware of Translucent Delignified Woods that are produced and being promoted as an alternate materials for light collection.
Due to intrinsic properties contained in certain wood sheets/films produced as a Delignified Wood Product, there are structural elements that makes the Wood Board an attractive Glass Replacement, hence offering potential to be used for the DML Panel ?
The following is an extract from the Link.
The Link is quite recent as a Paper, and will introduce others to the concept of why there is an interest in recent times for the production of Delignified Wood Sheet / Films.
In a further research effort [75], delignified Canadian white maple template was infiltrated with an epoxy resin embedding carbon quantum dots and cured at room temperature.
The so-obtained composite films (0.5 mm thickness) exhibited high optical transmittance (about 91%), water absorption stability (weight gain rate below 9%), good longitudinal tensile strength (about 140 MPa), and UV-shielding properties (Fig. 10).
https://www.sciencedirect.com/science/article/pii/S2949822824001527
@spedge I believe the 1.5mm Panel you have is from the pre veneer method where the Tree Truck is put on to a Larger Lathe and the Growth Rings are unpeeled to produce the Veneer to make a Ply Wood.
The link will show the methodology referred to.
https://extension.okstate.edu/fact-...er-lumber-lvl-as-a-construction-material.html
The above led me to my becoming aware of Translucent Delignified Woods that are produced and being promoted as an alternate materials for light collection.
Due to intrinsic properties contained in certain wood sheets/films produced as a Delignified Wood Product, there are structural elements that makes the Wood Board an attractive Glass Replacement, hence offering potential to be used for the DML Panel ?
The following is an extract from the Link.
The Link is quite recent as a Paper, and will introduce others to the concept of why there is an interest in recent times for the production of Delignified Wood Sheet / Films.
In a further research effort [75], delignified Canadian white maple template was infiltrated with an epoxy resin embedding carbon quantum dots and cured at room temperature.
The so-obtained composite films (0.5 mm thickness) exhibited high optical transmittance (about 91%), water absorption stability (weight gain rate below 9%), good longitudinal tensile strength (about 140 MPa), and UV-shielding properties (Fig. 10).
https://www.sciencedirect.com/science/article/pii/S2949822824001527
@spedge I believe the 1.5mm Panel you have is from the pre veneer method where the Tree Truck is put on to a Larger Lathe and the Growth Rings are unpeeled to produce the Veneer to make a Ply Wood.
The link will show the methodology referred to.
https://extension.okstate.edu/fact-...er-lumber-lvl-as-a-construction-material.html
JohnnoG.
It would be nice to have a clear material like glass but without its weight and rigidity.
Glass is too rigid.
The two sheets of veneer that make up the panel I have shown on YouTube run in the Same direction, so it is more rigid in its length than across.
Which helps it stand up by itself, a little.
I was ment to cut this into smaller panels, but never got around to it.
It was a nice surprise that the large panel worked so well.
Steve.
It would be nice to have a clear material like glass but without its weight and rigidity.
Glass is too rigid.
The two sheets of veneer that make up the panel I have shown on YouTube run in the Same direction, so it is more rigid in its length than across.
Which helps it stand up by itself, a little.
I was ment to cut this into smaller panels, but never got around to it.
It was a nice surprise that the large panel worked so well.
Steve.