OHM Acoustics "Walsh F" Speaker remakes

[BudP]

Hi again Bob,

I find that, indeed, I am not uninterested in mass damping schemes.

The thought decanted into my awareness is primarily for an Open Baffle speaker. Imagine a rectangular frame with openings to allow pouring of sand into this rectangle once it is skinned. Skin with constrained layers of mahogany single ply with viscous glue as the layer constraint and each laer growing in size and changing from a rectangle into a musical instrument style of French Curve terminus edges.

Your spaces with lead balls are distributed through out the ply layers to ensnare energy pulses that excurt beyond a single ply skin and the final ply has the EnABL pattern applied for final surface control.

The back side would also be constrained layer skins but would devolve in size to provide a shaped back bezel with a longer path length than the front side, to encourage a back angled phase skirt for the null zone.

All drivers would be mounted to MDF rings, held in place with thin dowels and supported by the sand and outer ply skins.

In my brain, the various layers reduce the systemic resonances layer by layer and the curlicued final shape provides a non symmetrical path length, further limiting the creation of standing waves.


Ed,

I meant to say that I take a finished cabinet, apply the pattern with flat clear acrylic paint and then cover only the pattern with the conformal coating. That the conformal coating material, not the pattern paint, was the mad to bubble material mentioned, with out excuse nor seeming remorse for it's criminal behavior.

Bud

[Ed LaFontaine]

Hi Bob,
...as an aside there is music and truth in what you share with us....and no lack of humor in the harsh reality we wrestle with, to wit:

No other choices are allowed on this dirt ball

I just love that.

I'm sorry I wasn't more clear expressing my interest in veneer. I envision rectangles of veneer attached to the raw wood of the baffle in the EnABL pattern. This followed by the application of a "normal" cabinet finish. I'm including in this the concern of a designer: whether to "hide or accentuate" the pattern. The veneer could be the same species as the baffle or chosen to offer a contrast.

My question was a suggestion (sorry again...no wonder it didn't translate) to substitute and apply an EnABL pattern made from wood rather than brushed on, and then apply the cabinet finish, hence my concern for the thickness of veneer exceeding what is appropriate for the pattern to be effective.

[rcavictim]

Originally posted by Ed Lafontaine
Hi Bob,
...as an aside there is music and truth in what you share with us....and no lack of humor in the harsh reality we wrestle with, to wit:

I just love that.

Ed, That was most poetic but you have miscredited me. You meant to address this praise to our friend BudP.

[rcavictim]

Bud,

Out here in the country we find a thick and dense rubber matting called `cow mat` which is placed on the dirt floor in a barn to add some comfort for the critter1s feet. Cow Mat, about 5/8-3/4 inch thick, would also be a good thing to place on a concrete floor in front of an electrical work bench. I have looked at it with the idea of laminating it on the inside of a MDF speaker cabinet to act as dual layer vibration control. Maybe instead of what you went on to propose above it would be easier and almost as effective in practise to just cut an open baffle out of Cow Mat the shape of a large sunflower. Yellow paint optional. A triangular jutted edge is a proven method of reducing standing waves at the terminus of a surface. I have used it with great success to improve bandwidth and Z match (lower VSWR) in my microwave antenna work.

Yes, must figure out how to turn a snow drift into electricity.

Re: my moniker.....
I could have called myself ThomsonCSFvictim, but that is not nearly as clever or schmood, plus I saw that sham and have not allowed myself to actually become a `victim`. I like and continue to collect and be impressed with the stuff RCA developed in the `good old days` of vacuum toobz including a bunch of their fine 1940`s television receivers and 1950`s color television receivers (they effectively invented the NTSC system we use today). As an indefatiguable punster, in all the fractured manufacturer trademark and poroduct names I ever came up with and there were many, Black and Blacker, Hell and Bowel, Empirical Whip, etc., rcavictim was my fave.

[Ed LaFontaine]

That trip to the Patent Office was worth it (search for # 5304746).
Having read through it the first time I've found most of my questions answered. It is heady stuff in that what is being offered is outside of the box I've been in.
I had to put down the urge to ask "How could that happen?" several times in order to push through it. I'm gonna step outside and read it again before posing more questions.
Regarding my misallocation of credit due Bud, sometimes Mongo just kicks poetry right off the porch.

[BudP]

Hi Ed,

I know exactly what you mean. In the usual best pea patch manner, I am quite self absorbed when on one of these rampages. There are more we haven't discussed yet. It is only when I can catch my breath and stand back, that the fear sets in.

Questions like "How could this be" are usually for later. "What have I done" and "are they are gonna commit me over this one" are early candidates. Trust me, the EnABL thing is not the most unbelievable activity I have going on here. It is the only one I was ever foolish enough to patent. The rest of the non mainstream plants from this here pea patch just twist your head around and the only sound that will come out of your mouth is vooooodooooooo.

I am just getting around to enjoying the thoughts Bob offered a little earlier. The one about using pre-splatted cow barn padding to make pointy ended, yellow colored flower petal, Open Baffle, speaker boards from, does appeal, once you get over the mental pictures and olfactory expectations. That, Empirical Whip and Black and Blacker are very resonant here in the Pea Patch of the mad, out on the upper left crust of the united snakes....

Thomas tells me privately that he is working the problem of application. Spending money like grandpaw at christmas and having great fun.

Bud

[Lynn Olson]

Originally posted by rcavictim
Bud,

Re: my moniker.....
I could have called myself ThomsonCSFvictim, but that is not nearly as clever or schmood, plus I saw that sham and have not allowed myself to actually become a `victim`. I like and continue to collect and be impressed with the stuff RCA developed in the `good old days` of vacuum toobz including a bunch of their fine 1940`s television receivers and 1950`s color television receivers (they effectively invented the NTSC system we use today). As an indefatiguable punster, in all the fractured manufacturer trademark and poroduct names I ever came up with and there were many, Black and Blacker, Hell and Bowel, Empirical Whip, etc., rcavictim was my fave.

I own one of the late generation RCA 36" HDTV's - which although having crapped out in the analog-TV tuner section, displays 480i, 480p, and 1080i from the cable box just fine. (The TV is actually a giant multi-sync crt monitor, with the screen losing sync, blacking out and making a loud "clunk" when the sync rate is changed.)

What's really crazy is the corporate history - the set and the owner's handbook say "RCA", but it was made when Thomson CSF owned the brand. And of course Thomson is the French government-owned company that developed - wait for it - SECAM color, the notorious "System Against American Method" that is completely and totally incompatible with NTSC. (While by contrast the German Telefunken PAL system is an elegant refinement and further development of NTSC color.)

And just to mix things up even more, RCA was a prominent participant on the long-running ATSC effort to develop digital HDTV. Not that I can recommend buying one - although the color is nicer than Sony color (which seems to use non-standard phosphors and colorimetry), the reliability is nothing to write home about. But the monitor part of the set soldiers on, sharp and with good convergence, so I'm not planning on buying a 1080P microdisplay set any time soon.

[rcavictim]

Lynn,

Well if we didn`t get lucky once in a while life wouldn`t be much worth living now would it.

You mentioned colorimetry. RCA invented the tricolor kinescope tube and the first ones had phosphors that did the right colors. Unfortunately they weren`t all that efficient, the red being rather poor and consequently the electronics driving the red gun needed two triodes parallelled up to give that one gun more drive current. That gun would usually go flat before the other two rendering these CRT`s short lived. The colors had correct colorimetry however and the tube could reproduce a proper yellow (this seems to be a good test). The early correct but dim phosphors appeared in the 15GP22 (1954), 21AXP22 metal cone (1955) and finally the 21CYP22 (1957-1959?) CRTs. The last one was phased out in the very late 1950`s, replaced with a much brighter tube the 21FBP22 and shortly thereafter 21FJP22 (a 21FBP22 with a bonded safety glass). Although brighter by a large amount the colorimetry of the phosphors, particularly the red were slightly wrong. They won`t make a nice yellow. This tube was then used by all the TV manufacturers (RCA held the patent and issued liscenses) until the venerable 21 inch round color tube was replaced by the various rectangular tubes starting circa 1966/67. Since my vintage TV collecting ends with the last of the round CRT`s I don`t know what happened since. I have sets in my collection which use the first three color CRT`s but have only seen a color picture briefly on the 21CYP22 equipped set. I need to restore that one so I can really see what the proper colorimetry looks like.

I guess this went a bit off topic.

BTW, my apologies for the typos I did not catch like poroduct.

[R. Jamm]

Hi c2cthomas

How’s breaking in the Mamboni speakers coming along? Please report

[c2cthomas]

Hi R Jamm,

I will finish building up the 2nd test speaker tomorrow. On this 2nd speaker I have reduced the height by 4 inch's from 28 inch to 24 inch. The reason for this is that with the 28 inch speaker I notice a "richer" sound when I stand up and my ear is above the baffle and speaker frame - so I am trying to get that same richness when I am sitting. I thought of reducing the height even more but was afraid I would lose to much bass response. I'll know tomorrow when I finish building unit number 2.

I must say that the Pioneer 10 inch mid-woofer doesn't seem to take much to break in - about a day seems to it! My Fostex 167's took a solid week - heck they were so tight when they were new that I had to kick up the amp to around 90db's just to get 'em moving and then back it off to mid level and just let 'em cook. The Pioneer fired up right away and seemed pretty good from the get-go!

I am still amazed by the openness of the sound these units produce! Taking the speaker box pretty much out of the usual scheme of being a "box" that "aims" the direction of the traditional speaker is nixed and these things - they sound similar to OB designs - very open sound and very smooth.

I'm looking around for a different tweeter than my Heils - just to see what is out there in today's world. My current thinking is to use a tweeter that is good from say 3 khz up to above 18 Khz and mount it in a similar configuration as the Pioneer (reduced in scale of course) and flip it upside down so the magnet of the tweeter would be back to back with the magnet of the Pioneer. I'll work up a sketch and put in a later post to show what I'm thinking of.

I'm also thinking that the baffle the Pioneer sits atop of is a bit to wide because of the 14 inch SonoTube I'm using. So I'm considering putting a dome shaped baffle on one of the test units and doing some EnABL patterns to see how that helps smooth things out.

One thing that I'm still very sure of - for the cost and ease of construction this is one heck of a speaker!

I FINALLY got my Micro Gloss delivered at the local hobby shop so now I can start doing some of BudP's EnABL patterns!!

The stencil experiments just did not work out well at all - although I still want to try a couple of things. Right now it looks like the way I'll go with applying EnABL is to use Speedball Calligraphy Pens - sizes A0 thru A5 (square, flat tip on the A series) and the Polly S acrylic paint. I'll print out a pattern on regular paper and trim it down to a size that I can tape to the speaker near the area to be treated and use it as a guide. Then it's a careful touch with the correct sized Speedball tip and whack-o - my speaker cones have been EnABLed!

BTW - the problem with the silkscreen stencil was that the Polly S paint is so thin that it would creep underneath the edge of the screen and blot out around the edge of the pattern. It could make for a rather interesting "ink blot" test (perhaps something I should be considering ) but not a very good application of BudP's EnABL pattern.

I noticed on another thread that there is some discussion of BudP getting his own EnABL thread going here sometime soon. Congratulations Bud!

My suggestion is to put an EnABL pattern all the way around the edges of it in order to keep things smooth and dump off all distortions and distractions. But then I guess that most of the stuff I'd post would wind up in the bit bucket! :bs:

Attached is a photo of test tube #2! I will report on the findings!