Some More Questions On ELS Design
I'm finalizing my ELS design and I have decided to make 2-way full range speakers. I already have a sub woofer composed of 4-15" Tempest-X woofers in a true infinite baffle that is equalised flat down to 20 Hz.
The ELS panels for the range of 40Hz to about 6000 Hz will be 60"X10" with 1/8" SD spacing (two per speaker). The Tweeter panels will be 60"X3.5" with 1/16" SD spacing and will be positioned between two bass/mid panels. The speaker will be bi-amped and the crossover is a Behringer DCX2469.
I've got all the material except the perf steel which I can pick up locally. I'm planning on 18 gauge steel, 1/8" holes, 40% open for all the panels although I may consider using aluminum. I already have a large roll of 1/4 mil mylar that I bought about 30 years age when I built my first Sander's style ELS's as published in the Audio Amateur.
I'm debating with myself whether to use the inner tube method for tensioning the mylar or heat shrink. I've got a high end heat gun that has digital temperature control. Because of the size of the panels, I would have to cut and bond two inner tubes to use that technique.
Anyone have comments or suggestions?
I would use inner tires.
Very Good !!!
I use the heat shrink method on my panels.
Once you get them running, You may find that you can use a much lower crossover frequency.
On my 3.5" X 9.5'" panels I have a .075" D/S and I have been able to get down to the 200hz to 300hz range with no problems and I like them very much.
My next panels will be 5.5" X 96 (2 x 48") with around a .1" D/S in order to crossover at around the same area and still have enough D/S to not bottom out on the mid bass peaks and low frequency vocal passages.
6000khz is quite high and when you get them running you will find a whole lot more enrichment in the sound of things below that !! Trust me !!!! :)
When I first got mine running again with a single 8" sub crossed over some where in the 350hz to 800hz range with a cobbled passive crossover I was just floored and blown away !!!
There is a picture of it posted in these threads and just recently reposted as well.
My little panels have a resonate frequency in the 70hz to 90hz band and with a 300hz steady tone at full displacement is enough to put anyone out of the room.
I would try to get at least a 50% open area material if not close to 55% becuase by the time you get a thick enough coating you wil be down into the 40% to 45% open area.
Even though the will sound fine I have found that anything less than this will start to take away from the transparency effect and higher end detail.
I use a different material for my stators so it is hard for me to give some exact details.
Maybe some one whom has tried larger sized holes can chime in here.
It seems that 5/32" holes are the norm and some have even used 3/16" but I wouldn't go any bigger than that as it may start dropping the efficiency of the panel.
Good luck and keep us posted on your Build !!
P.S I am using 4-12's and for 4-10's and soon 6 more 8" subs for my bass system, at the moment I am very happy with the results( just for reference ),nothing special just some good ole' drivers. :)
I'll give the inner tube method a try if I'm successful in gluing two of them together.
As far as crossover frequency is concerned, I'll experiment with that once the speakers are built. What are your thoughts on a tweeter panel mounted between the two bass panels? Is this the ideal location or should it be mounted on the inside of the two bass panels? The tweeter will have a 3-1/2" membrane width. Do you think it will help with horizontal dispersion?
Yes I have been contemplating such a design.
It is a method that has been used before I have seen many different versions from the older famous Qaud and a few DIYed systems aswell.
I was thinking about doing a 2" to 3" wide tweeter panel in between two of the 5.5" wide ones that I have planned.
As I am tight on space (narrow room) I am sure sure that one of each will be enough per side.
I only have 66" center to center for them to fit in and my listening position is 12' to 14 feet away.
If I had more room I would definitely give it a try,and, if I were to use them in a full range system with no woofers.
As that type of setup seems to appeal to me.
But I will determine if I will need it in my application after I get them built as well.
I forgot to mention that I did prefer my little 3.25" wide panels over my 8" wide panels when it came to dispersion.
Although the wider panel had a better lower end kick to it due to its width.
I haven't listened to those panels since I had built them in 2003.
And I had just got the little ones running again last year.
Although I did do a side by side comparison back then I still remember their characteristics and found myself listening to the smaller width panels more often as it was easier not having to hold my head in a vice.
But the refurbishing process I did on the little panels last year surpassed any performance issues I had experienced in the earlier days.
The main reason I chose 5.5" for this build was to to utilize the full width of my material of 12.5" with little waste.
And to add a little bit of surface area for the lower frequency's and hopefully won't be to directional at around 8khz to 16khz otherwise I was going to build two pair of 3" to 4" wide X 48"long panels like you had mentioned (interesting,he,he).
Basically a longer version of my little panels that I have grown to be so found of at this point.
I will have them running within the next week and in stereo for the first time since 2003 as well as a digital crossover system using VST's on my computer and my 2in/8out Gina24 24bit card.
I am so excited a can barely type.
So, Yes I think that your 3.5" wide membrane will do good as I am very aware as to what to expect from it.
I am about to finish up my variable supply finally after another year has gone by so that now I can get back to designing building and testing these things,Not to mention, Longing for their incredible sound.
Now I'm getting excited. Just ordered the perforated steel. 20 gauge 3/16" holes on 1/4" centers and 50% open area. eight pieces 9.5"x60" and 4 pieces 5" x60". I'll pick them up on Thursday.
I played with some 1/4 mil mylar last night to see how my heat gun worked for heat shrinking. Setting the heat for 450*F and holding the tip about 1-1/2" above the surface the mylar shrinks nicely. I may forgo the inner tube method and just use heat shrink.
Hot air is only good to a certain extend. You can never get the same tension from using hot air as compared to mechanical tension. You can try it. Some people have some successes, but a lot of people don't like it either.
Agree with Wachara C. you have to stretch to the point of film plasticity and shrinking cannot generate that tension. Diaphragm tension is what provides stability under drive and if you want to run wide or full range and run as high a static charge as possible shrinking is not quite enough. Best regards Moray James.
I agree with W and MJ - mechanical tenisioning is the way to go!
If you think the "bike tube"-method is going to take to long to build, a flat surface and a fish scale is another way to get high even tension.
Good luck with your build!
I've already built a stretcher table for the inner tube method, but since it is so large (64"X26") I need to glue two inner tubes together. So far I have not been able to do that without air leaking. I've ordered some different rubber glue and I'll keep trying.
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