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-   -   How to construct a cube louver (Acoustat) (http://www.diyaudio.com/forums/planars-exotics/164430-how-construct-cube-louver-acoustat.html)

pforeman 3rd April 2010 09:28 PM

How to construct a cube louver (Acoustat)
 
Could someone give me some insight into how Acoustat types are constructed. I believe I understand most of it.
what I'm mostly confused on is.
Do you make one side of a cube louver by applying the wires to the louver, apply the spacers to the cube louver, then glue the stretched membrane to the spacers, repeat for the back side cube louver.
I thought the Acoustat was somewhat dis-assembleable? If so, this would be permanent.
Is there a better way?
Thanks
Paul

david yost 4th April 2010 12:05 AM

Here is one half of a panel: http://www.justrealmusic.com/images/...02_01%2031.jpg

And one showing the coated diaphragm: http://www.justrealmusic.com/images/...02_01%2020.jpg

pforeman 4th April 2010 12:41 AM

Thanks for the pictures. I take it the first photo which has a glue-ish looking substance on the frame (wood ) is where either the spacers or membrane is attached?
Paul

david yost 4th April 2010 01:34 AM

The flat surface you see is the spacer. Acoustat used rigid plastic for these and the whole "sandwich" was glued together -- I have seen a series of pictures online that covered the whole process, but I can't remember the site.

I have never tried to take a panel apart, but I guess these pictures prove it can be done.

Few 4th April 2010 03:23 AM

Try http://www.diyaudio.com/forums/plana...ry-photos.html.

Few

david yost 4th April 2010 08:15 AM

Thanks, Few

Your link leads to a dead end, but you put me on the right track. Here is a live link:

Acoustat, Acoustat Factory, Photo Tour

moray james 4th April 2010 09:55 AM

You might want to consider using acrylic louvres rather than the much cheaper styrene louvres. The acrylic will cost a lot more but the quality of the material is much higher and will be longer lasting. You can practice on styrene louvres and then do your final build with acrylic. Note you will have to use different adhesives and solvents than you do with the styrene. If you are doing a simple proof of concept experiment or you don't have a lot to spend then simply use the styrene. It will give you acceptable results and last a long time. The advantage to the acrylic material is that it is much stronger is better self damped and is more stable and will not get brittle with age as the styrene does.
Acoustat panels were not intended to ever be disassembled. With the acrylic you can easily go with a 3/8 inch thick louvre rather than the 1/2 inch styrene Acoustat used. Styrene louvre is also available in 3/8 inch thickness which works well too. If you use a wire with a thinner but stronger dielectric then you can use more wires per inch than Acoustat did which will yield a more efficient panel. You can use threaded rod to make a winding jig. !/4 - 20 threaded rod will give you 20 wires per inch perfectly spaced. If you just want to go with 5 -6 wires per inch as Jim did then just drill holes in the end row of the louvre and thread the wire. Not my first choice but it works.
You could also try drilling small holed into the end row of the louvre through both parallel walls of the first cube then insert a 3/4 inch finishing nail into the drilled hole and use that as a solid hook to wrap the wire around (you will need one nail for each loop of wire so say six per inch). Once the wire has been bonded down simply pull the nails out and the adhesive will hold the wires in place.

Few 4th April 2010 04:32 PM

Sorry, that link appears to be a dead end. Try this instead.
Few

speedracer5 4th April 2010 05:39 PM

I've only had experience with Acoustat for about six weeks to two months now but here are my observations nevertheless.

First: Acoustat plastic louver panels look like they should not work at all and are truly an unlikely creation considering how most Estats are made today IE metal stators. I know this may sound like and ignorant statement to those familiar with the history of stats, but to the uninitiated it seems like an "unlikely and ponderous craft".

Second: they do indeed sound incredible. Incredibly smooth and more dynamic than comments I have heard previous to hearing them and then picking up a few sets of different models. They make bass. Deep bass into the 30's.

Third: The louver/wire loop grid construction is both brilliant and compromised. As much long term durability as these have proven to have, every single loose panel (out of the speaker) I have inspected has several problems and most seem to be associated with the glue-up process and the plastic construction materials.

Mechanically as a structure even when brand new and in a working set of speakers it is my contention that the panels physically cannot maintain rigidity under the acoustic force that these panels are capable of. Simply put the grid itself vibrates and distorts. This also could cause many electrical reactances that I am not qualified to analyze. But suffice to say that more rigid construction would be a great advantage to the "seminal" design of the original Acoustat panel.

Furthermore, I have seen glue seams partially or even fully split on the long sides and of course the known loose wires that come unstuck to the grid causing several "buzzing" or vibration conditions to occur. I have not had enough time with these to fully "see" with my eyes all these problems, but with the stack of used panels I have I'm sure to be tracking down little annoyances for awhile yet.

Lastly (for this post at least) Every panel has wrinkling in the corner of the mylar that is near the electrode connection to the panel. Looking at the construction photos on the TAC site, the wire and self adhesive metal tape that is used to secure the wire to the dark colored static coating is the probable cause/problem. I can make a bet that the "relaxing" of this compound "stack" of dissimilar materials and adhesives as well as the frame glue loosening is causing the corner wrinkle to occur. Later panels in the Spectra series I have not seen so I do not know if that problem was fixed in later model of the same panel.

I write all this detail because I believe that a truly un-compromised, 8 or 9 inch by 45 inch Acoustat panel has not been tried. Most have gone the route of smaller panels and "segmenting" the diaphragm into smaller subsections. I believe it would be a worthwhile goal to produce a much "better" and improved Acoustat type panel with much more rigid structure and the same or similar electrical and physical geometry that would allow a truly full volume, full range presentation from this fine sounding design, and not have to deal with the little niggling problems that the aging panels present. The volumes I played a pair of Model 3 at truly astounded me, and the smoothness and coherency at those volumes as well as deep bass were a surprise to me. However loud bass transients caused some "snap, crackle, and pop", yet I do not think that the speakers were necessarily arcing especially since I was sure that there were some stressful buzzing doing a mild sinewave sweep from 30Hz to 300Hz. I think more rigidity and an improved insulation might help.

Also in another thread I asked if anyone knew just what the coating mixture on Acoustats are and nobody seems to know. The TAC site is vague but describes it as carbon black and dissolved polymers. Some place write that the coatings resistance was changed to better hold a constant charge. With all the good press that King Estats from China are getting at $6K to $8K per set I'd thing a "BETTER" Acoustat sounds like a fairly easy and cheap way to DIY a really nice stat. A clear "see through" speaker that needs a "CONE" to have 30Hz bass does not sound like my cup of tea. The bass that 3 panels per side of 30 year old Acoustats has shown me enough that you can build a full range stat and not need it to be 8 feet tall and 4 feet wide and cost 20 grand. Besides most of us do not have rooms big enough for Sound Lab. I'll follow this thread and share what I learn as I tear apart a bad Acoustat panel.

moray james 5th April 2010 04:17 AM

first the wire /grid stator design that Jim Strickland came up with was and is a brilliant piece of design work and it does a far better job than one would expect. You need to go back and look at what the retail price was of these unit to partially understand why specific design choices were made. The speakers were very inexpensive too much so as the company never made enough money and eventually went bust as a result.
As far as longevity and build quality goes Acoustats are the best that have ever gone to market. That's not to say that they could not be better but they delivered the goods in spades and most are still running.
Regarding repairs of loose stator wire you can use Testors model cement which is specifically designed for styrene they also have a citrus based cement which is more expensive but is totally non toxic which is nice and it works well. Use a thin wire to wrap the loose wire back into position twisting tight from the outside of the grid. Make sure the wire you use to pull the stator wire into place is not directly over the point where you need to apply your fresh glue. Several applications are usually required to get the stator wire locked well into place then remove the twist tie wire ad move on to your next repair. Please note that this is an ok fix if the stator wire has not jumped too far out of its home spot. Sometimes stator wires that pop loose actually make contact with the diaphragm and if this happens on the conductive coating side then you will most certainly have arc holes in the insulation of the stator wire. Getting the wire back into place and bonded down is good and help a lot but you have to understand that this is a patching process not a full repair. You are patching things up not repairing them. Sometimes this kind of fix does the job but you cannot count on that. These are old worn speakers and you have to keep that in mind.
The reason for the wrinkles in the corners of the diaphragm is simple. These diaphragms are made of DuPont Mylar HS65, which is a 0.65 mil thick heat shrink Mylar. The film is shrunk to tension and will over time and use stretch and get loose in the corners where the most tension is. You can re tension the diaphragms to as new tension with a heat shrink gun (carefully).
There is no issue with the resistive coating used from a physical point of view it is the best bonding coating I have ever seen though it is heavy. The coating is not as resistive as one would like but "thems the breaks". It sticks like wet poop to a blanket which is no small feat considering the blanket is Mylar with a surface tension of about 45 dynes per cm sq that's smoother than plate glass. This compound was made by a chemist who worked for one of the big magnetic tape manufacturers and he never told anyone what it was and when he died Acoustat had a heck of a time to replace it. Newer coatings are available which are far more resistive which is good or you can go the old tried and true method and used the nylon coating that Quad used the recipe is on line in a number of places. That will get you into the gig ohms of resistance and last a long long time.
There are lots of ways to modify an Acoustat to improve it but most are a lot of work and that effort is better spent on designing and building a new and better panel. You want many times more wires per inch to increase efficiency. You want to keep the DCR of your stators as low as possible which means connecting them electrically at each end. This can be done on an Acoustat to benefit but it is a genuine PITA to do I have done a bunch of these but it is not fun and you cannot get paid enough for the grief. Building new panels with Acrylic louvre is the way to go stronger better damped easier to work with easier to glue way longer life span. You can buy louvre in 1/2 inch thickness (with 1/2 x 1/2 cube dimensions) and you can get it in 3/8 inch thickness also with 1/2 x 1/2 square openings. The thinner material to me is better. If you use 3/8 Acrylic the stator will be as strong or stronger than the factory 1/2 inch styrene units. To your concerns of strength yes the panels could be stronger but they are better than a flat perf metal stator by a good margin and only a curved perf metal stator is really stiffer but then it has issues of its own. I have seen a set of Acoustat 2 plus 2 frames which had been wedge clamped to the ceiling to keep them rigid actually crack the 1 inch thick MDF frames of both speakers exactly in the middle of the frames (on both sides) where the two vertically stacked panels meet. If I had not seen this with my own eyes (I repaired these myself) I would not have believed the story. I have also seen the panels actually tear the lag bolts used to mount the panels out of the fir strapping in the frames. These things are very strong. Could they be better? Yes. Would they benefit from improvements? Yes. It is a lot of work but I think that the work is justified.
I do not believe that ESL's should be used for making bass. That's not to say I don't think they can make bass because they can. It is just that it is not a realistic or practical from either a domestic or performance point of view. You can make better cleaner deeper and physically smaller bass cabinets with a dynamic driver and do it for less expense. You end up with better overall performance and far less compromise than going full range ESL. A tall line source ESL which is narrow will provide very good horizontal dispersion and image. I would not build as wide as Jim did as he was trying to get bass out of his panels. You need to ditch the heavy HS diaphragms for thin stretched skins. You will get a stable panel (something the Acoustat had issues with) more output and better dynamics along with improved distortion figures. You can make a stat make bass but it involves a lot of trade offs. Better to get the job done the easiest and cheapest way and obtain better results. Hybrids are the way to go as far as I am concerned. C grade Mylar and other polyester films are available to the diy builder down to 3 microns in thickness (6 is probably the most practical to work with though).
If you want to see if your Acoustats are arcing get close in the dark and play your torture test disk. I would bet you they are the PVC dielectric is simply past its prime in a very harsh environment it has done a good job it's just time for fresh panels. A close physical instection in good light will probably reveal a number of small tiny pin holes in your diaphragm which are easiest to see when they are in the area of the diaphragm covered by the black resistive coating. If you find any pin holes then you have physical proof that your panels are arcing. Wire stators are tricky to build and to keep the stator wire dead flat on the louvre surface is something you just have to learn by doing. Styrene louvres are not flat to begin with either so you can see that there are going to be issues with some panels just working better than others. The harder you push the panel as far as bass response goes these issues become more problematic. When you lighten up on panel excursion then those problems go away and you can concentrate on making your panels play louder not deeper.
If you want a boost for your speakers add a couple of extra multiplier steps to your HT supply and get the voltage after the load resistor up to about 5 Kv or more if your panels will take the extra charge. This only costs a few dollars and makes a big difference as does a good noise filter for the HT supply. Hope this has been of assistance. Regards Moray James.


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