the crate material was best guessed as a three ply poplar or similar? with what thickness? Approx. 3/16"?
No.... More versatile, water resistant, and maybe a stronger bond to most materials
So is the shellac finish simply foe aesthetics or is it intended as a stiffening skin or is it both? ThanksHi Christian:
I think you are correct wrt the poplar ply - It will be hard to surpass with more complicated and costly materials.
Shellac = French Polishing yes.
I'm far from an expert in this but I have achieved quite good results with a very basic approach. I'm also after a satin finish not a mirror gloss one.
One issue with poplar is that it has a very bland finish - it's very pale and the grain pattern can be uninspiring. I initially only had Gold/Orange shellac and I thought that it would end up too yellow by itself so I tried first applying a very light stain to the ply which worked OK but I think could be avoided by using a mix of Garnet (dark) and Gold shellac instead.
So I bought flake shellac in gold, garnet and platina (blonde). The flakes keep indefinitely if stored in a dry cool place unlike premixed shellac.
3:1 Alcohol / Shellac mix by weight is a good middle mix (just a bit thinner that a "2lb cut' but you can try different ratios. I thinned out the first coat somewhat for penetration.
I didn't do any grain filling - I relied on judicious sanding back between coats which worked OK - I wanted to avoid too much junk in the panel and I don't mind a trace of grain showing. One luthier uses West System epoxy to seal the back and sides of open grained woods but not the soundboard ()
Application- I have tried the traditional cloth method but it's difficult and takes much practice. I found that with practice I could brush it on quite well. When brushing you have to be quick and only brush with a forward or backwards motion, not both, work from one end to the other as evenly as possible across the panel and avoid going back over wet areas. Apply enough to the brush to get a wet finish and as soon as you start to use the brush load up - dip again and go - it's important to get a flow going so you end up with an even wet coat. I used a 30mm wide brush and stored it in a jar of alcohol between coats.
I haven't tried spraying, but it seem to be an ideal candidate as it's very thin and is easily cleaned out afterwards. Maybe I would revert to spraying if my panels were larger - long narrow panels would still be easily paintable however, it's when they start getting wider that makes it a bit more difficult, but you could probably just use a wider brush
It dries very quickly - I help it along with a heat gun on a low setting waved over it if I'm in a hurry.. make sure it's not dusty if you do that.
You can sand back after each coat dries. I use worn 240 grit paper or fine wet and dry paper.
I applied 4 coats sanding between each, and to remove the gloss after the final coat (which after 4 coats is still a bit uneven) I rub down with grade 0000 wire wool which blends the finish and gives a satin look.
I found the shellac finish is surprisingly tough - tougher I think than acrylic lacquer, so I believe it's and excellent way to finish timber in general - I applied it also to some pine feature strips and it turned out great. It's only drawback is sensitivity to moisture on tables etc but that doesn't apply in this case. It's stood the test of time on musical instruments so that's good enough for me.
Oil - I used no oil - I haven't had any issues with the finish on vibrating panels so I can't see the need for oil.
Go for it Christian
Good Luck
Eucy
Steve with respect to your thin card panels it would be very helpful for those (in world wide locations) who may want to replicate your work if you could provide some basic information about the card stock A visit to a art supply shop could provide information as to card stock thickness weight /stiffness/density etc. from paper suppliers so that others can purchase material to replicate your results. For those like me I can go down to the recycle bins in my apartment bldg and pick out what ever samples there which appeal to me but I too might like to make one just like yours so I have a reference. At the beginning of a building journey it is always nice to have a reference. Thanks
@Eric, @homeswinghome, et al,
I've been trying to get my teeth into LISA FEA, thanks for the very helpful guides, Eric. I've been having fun modelling different shapes with different properties.
Two questions:
1. How would I model a panel assembled from different materials, for example a polycarb plate with a hole in it, and an aluminium disc inside that hole on which the driver is mounted.
2. How would I use LISA to find the coincident frequencies of different panels? None of the equations I use give me consistent or believable results. I've been having arguments with ChatGPT regarding this, and we've eventually agreed to disagree....
Steve what about a veneer in a pie pattern made up of wedges where the grain orientation alternates between straight from outside to centre to across the pie shape? in this way a three layer lamimate could be made where centre disk is offset by one slice from the top and bottom layers?
Steve what is overall dimension for this panel along with the thickness please? The Shirley Horn clip does sound good thanks. Would you say that your double 0.5 mm small card panels (I think they were around 6 - 8" dia ?) do they sound like this?
Steve are you bonding the package label sides together so the sized and print surfaces (probably provide some additional stiffness) are in the middle o the ply? then normally two full strength coats of PVA on the exciter side of the panel and two half strength coats of PVA in the front side? Have I got the recipe correct? Does exact panel size make much difference? What would you normally make the size format ratio? I think you mentioned 6x9 inches? I want to build a panel like this first to see what it will sound like. Thanks for answering my questions.
I've been playing with DML's for about fifteen years.
It is my opinion that one exciter per panel yields the best results.
Here is a photo of a prototype pair. I used corrugated plastic for panels. (Not the best material.)
stacked four panels isolated from each other. One exciter per panel. All panels were suspended
with duct tape.
They sounded pretty good and had plenty of volume. Bass was decent to 70hz.
It is my opinion that one exciter per panel yields the best results.
Here is a photo of a prototype pair. I used corrugated plastic for panels. (Not the best material.)
stacked four panels isolated from each other. One exciter per panel. All panels were suspended
with duct tape.
They sounded pretty good and had plenty of volume. Bass was decent to 70hz.
Attachments
wow that is amazingly smooth response so this is full range and goes down to what 40Hz.? what size would the material need to be to go down to only 100 Hz.? What material is proplex and how does it fair so far as efficiency goes and what exciter was used? Thanks. (does it sound as good as it looks?)
Steve these sound wonderful with lots of energy but they are well composed. so is this the white soft ps foam or the higher density expanded foam? what size were these panels? thanks.
I was co founder of Higwood Audio, we developed a planar magnetic travelling wave transducer using 150 gage HS Mylar it used wave traps at the outer edges and acoustic filter/loading across the panel it was driven by a single layer voice coil 1.25" dia and had a small centrally mounted dust cap to extend response. A heavier diaphragm would have been nice. We also terminated such diaphragms with polyester silk screen mesh which has very high loss and is available in a wide variety of weights. Some damping was added to the silk screen.
Hi Moray
I'm very interested in this... Can you please provide more detailed info on the construction
Thanks
Eucy
Edit...I found an article and realised I also had the patent downloaded... Will re-read with interest
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Our patent was applied for just a short time before the original Manger patent and blocked them. Manger contacted us asking if they could licence the technology or failing that suggested the two companies merge. We declined both options, at that time we were just too busy with a start up company. Our speakers were marketed under the Sumo Audio name. Things did not work out with Sumo which was too bad and we merged with Meitner Audio in Montreal. The speakers were then called the Melior 1and 2 along with an in wall speaker and some hybrid models but those were after I left the business Ed still lives in Calgary and runs EMM Labs with his son.
The Highwood panel had the voice coil placed in the centre of the panel for a specific reason, we did not use a spider on our motor rather we use a magnetic fluid in the v gap a a liquid bearing to replace the spider. This necessitated keeping tension on the vc as even as possible during motion. The DuPont Mylar HS is a biaxially oriented film which helped keep the vc stable. Hope this helps and is of interest.
The Highwood panel had the voice coil placed in the centre of the panel for a specific reason, we did not use a spider on our motor rather we use a magnetic fluid in the v gap a a liquid bearing to replace the spider. This necessitated keeping tension on the vc as even as possible during motion. The DuPont Mylar HS is a biaxially oriented film which helped keep the vc stable. Hope this helps and is of interest.
Hi Moray... Seems like the technology has some issues ??.. The hybrid 6 and the Melior 2 weren't given very favourable reviews ... Can you give some insight into the experience you have with these?, and maybe what could be/ should be done in hindsight to improve the performance
Also, how much thicker do you think the membrane should be...Drafting film is at least twice as thick as the material you used (.003 to .005 in). It is also relatively heat stable (IE non shrink)
Thanks
Eucy
Also, how much thicker do you think the membrane should be...Drafting film is at least twice as thick as the material you used (.003 to .005 in). It is also relatively heat stable (IE non shrink)
Thanks
Eucy
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the hybrid products were produced for very little time and were conceived by Ed Meitner. By the time the Melior 2 came about Ed was experimenting with the panel design and it is what it is close but no cigar, We did later make improvements to the Melior 2 but I don't remember if those ever were reviewed. The initial issues with the Melior 2 was bad motor brace design with an X brace that did not work. Vertical or horizontal braces both woked well.
I would say that a diaphragm of at least 2.5 mil or 3 mil would be a good place to start and play with the tension but I would try diaphragms up to 4 or 5 mil thick just to see. For an exciter I would experiment with polyester silk screed mesh. I hope this helps.
I would say that a diaphragm of at least 2.5 mil or 3 mil would be a good place to start and play with the tension but I would try diaphragms up to 4 or 5 mil thick just to see. For an exciter I would experiment with polyester silk screed mesh. I hope this helps.
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how many excites are used and what wattage is the exciter? I would love to have enough information to replicate these panels when I get back home. I also want to experiment with smaller satellite panel to see how they sound. Thank you.
View attachment 1072279 light size panels
Thanks Moray
Those thicknesses would bang straight into a thick acrylic dml panel which has been covered here previously, and which would be utterly different to the thin skin Mylar/exciter interaction.
I don't understand what you mean by your second last sentence : "For an exciter I would experiment with polyester silk screed (screen) mesh. "
Eucy
not mm but Mil which is 1/1000 of an inch, these are thin films. I was suggesting that if I was going to use an exciter to drive a thin film DML panel my choice would be to first experiment with using silk screen mesh rather than a Mylar film. The mesh has very much more internal loss (compared to a film) so modes might be better controlled. Of course this necessitates having a stretching jig. One of my favourite early panels was a line source dimension was about 12"x48" it had a 1 mil (1/1000") Mylar diaphragm tension was just short of its breaking point and used a vertical 4 ohm copper voice coil in the centre of the diaphragm and a matching magnet structure with ceramic magnets and steel pole pieces. The winding of the voice coil were all going in one direction by means of a wiring harness so signal entered vertical wire number one of the coil travelled up the panel connected to the harness which returned the signal via the frame well out of the magnetic gap to the next wire in the coil and so on so that signal flow of all the wires in the VC were all in the same direction. I hope this is of interest.
my take away from watching the IT video regarding corner rounding was that while it did little to the actual response of the panel it did shift the response upward. That meant that peaks and dips in the response were then no longer matching from one panel to the other so their effect on the sound was not doubled up with a pair of matching. The suggestion was to have a pair of panels one with rounded corners the other without. A small but nice touch (attention to detail) so long as you can live with the look.