lordtarquin'
When I made my canvas panels, I used acrylic paint instead of pva. When diluted to 40 or 50%, it becomes quite watery. The canvas is very flexible after drying, but the color coverage was very complete. They sound very nice, going down to 40 Hz easily. You might want to consider this instead of pva if you don't want the stark white look.
When I made my canvas panels, I used acrylic paint instead of pva. When diluted to 40 or 50%, it becomes quite watery. The canvas is very flexible after drying, but the color coverage was very complete. They sound very nice, going down to 40 Hz easily. You might want to consider this instead of pva if you don't want the stark white look.
Jaxboy
Interesting idea. I had wondered whether to do this. My final OB bass units will be solid black MDF, so something to match may be nice.
I'm going to try a pair per channel wired in series first, my thinking being that I can get the same total air movement with less air movement per panel.
Steve
With the 300 XO, it's largely buzz free. I've found that the corners are the main culprit, so need to find some way to address this. When I've sorted this, I'll do a full sweep & post the result. There's certainly usable output down to 60hz and probably lower.
Simon.
OK. Here's the 20hz-20khz plot of my canvas panel after a thin coat of dilute PVA has been applied. Please don't read too much into it - there's lots of buzzing and flapping at lower frequencies (below where I usually cross over).
I need to find a way of preventing the canvas vibrating against the wooden frame. Ramming butyl rubber into the gap is reversible, but glue gun probably isn't.
Pictures of the panel to follow when I've uploaded them from the camera.
I need to find a way of preventing the canvas vibrating against the wooden frame. Ramming butyl rubber into the gap is reversible, but glue gun probably isn't.
Pictures of the panel to follow when I've uploaded them from the camera.
Attachments
Canvas panel resonance problems
Steve
I've stuffed some butyl rubber in the gap between canvas and frame. However, I think the issues run deeper than canvas vibrating against the frame. As I do a frequency sweep, there is a whole set of resonances that occur, with the worst occurring below 300hz. In the first attached audio file, I've run a tone of 137hz. The canvas is oscillating at a very different frequency in addition to that being played. There also appear to be odd resonances occurring on the ply insert.
The second audio file is a 30 second 20hz-20khz sweep.
I've still not uploaded pictures from my camera yet.
Simon
Steve
I've stuffed some butyl rubber in the gap between canvas and frame. However, I think the issues run deeper than canvas vibrating against the frame. As I do a frequency sweep, there is a whole set of resonances that occur, with the worst occurring below 300hz. In the first attached audio file, I've run a tone of 137hz. The canvas is oscillating at a very different frequency in addition to that being played. There also appear to be odd resonances occurring on the ply insert.
The second audio file is a 30 second 20hz-20khz sweep.
I've still not uploaded pictures from my camera yet.
Simon
Someone mentioned he was using a mini-dsp equalizer on the panels.
Can you say which brand and model it is?
I am not thinking of using digital eq in the DML panels, but on a small full-range single speaker box, 4" driver, to see if I can get something up from the lower frequencies.
The comments from Lordtarquin on what is happening on the panels below 300Hz seem to quite clearly show that is the lower limit of DML designs. I'd concentrate on how to extend or flatten things up to 20KHz. Without eq, of course.
Can you say which brand and model it is?
I am not thinking of using digital eq in the DML panels, but on a small full-range single speaker box, 4" driver, to see if I can get something up from the lower frequencies.
The comments from Lordtarquin on what is happening on the panels below 300Hz seem to quite clearly show that is the lower limit of DML designs. I'd concentrate on how to extend or flatten things up to 20KHz. Without eq, of course.
Lordtarquin.
I can't really tell much from the test tone and frequency sweep.
Can you play music that sets off the buzzing?
The canvas and ply panel should play cleanly down to 40hz as long as there is no boosting of frequencies or playing at disco levels.
You could use something like a stethoscope or a short piece of tubing ,let's say about 2ft or so,to trace the buzzing source.
Just place one end or the tubing (garden hose for instance ) to your ear and move the other end around every nook and cranny on the panel and exciter.
This has helped me in the past.
How did you glue the ply and exciter to the panel?
What type of frame do you have , the canvas should not be able to come into contact with the frame except at the very outer edge?
Steve.
I can't really tell much from the test tone and frequency sweep.
Can you play music that sets off the buzzing?
The canvas and ply panel should play cleanly down to 40hz as long as there is no boosting of frequencies or playing at disco levels.
You could use something like a stethoscope or a short piece of tubing ,let's say about 2ft or so,to trace the buzzing source.
Just place one end or the tubing (garden hose for instance ) to your ear and move the other end around every nook and cranny on the panel and exciter.
This has helped me in the past.
How did you glue the ply and exciter to the panel?
What type of frame do you have , the canvas should not be able to come into contact with the frame except at the very outer edge?
Steve.
Calmart
I use a miniDSP HD. There are 10 bands of EQ per output channel and 10 bands for each input chanel. I previously had the standard miniDSP but it only has five of each. I use a calibrated UMIK-1 for measuring purposes, and REW to do the measuring and creation of the equalisation files.
Steve, they are artist panels from Mr Amazon. The canvas only comes into contact with the frame at the raised (curved) edges.
What I observed is that the at certain frequencies, the whole of the canvas panel was oscillating at a very different frequency from the one being played. The exciter is Gorilla glued to the ply which is glued to the canvas. The test tones were played at about the same volume as I would listen to music - not disco levels, but 'sensible' ones suited to large scale orchestral music. Above about 300hz, there is less of an issue but it's still not as clean as I would like.
I tried a brace for the exciter too. This improved things a bit.
I'll dig out my better half's stethoscope!
Brand, model? Is it small?
I would need a simple one with one or two bands at most, to take care of the lower octaves, below 200Hz. This full range does not get too low.
Calmart
Yes, it's small. Link here for the basic one: Active Crossovers: miniDSP 2x4
I tried various mics, but the UMIK-1 has been easily the best.
Yes, it's small. Link here for the basic one: Active Crossovers: miniDSP 2x4
I tried various mics, but the UMIK-1 has been easily the best.