DIY Walsh Driver

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Hey J and Glorocks and all

The L. Walsh patent is ingenious.
I've cobbled together many prototypes and, they all sounded good.
The design is omni by nature and, any problems with that could be overcome I believe.
Lincoln Walsh never mentioned to term 'bending wave' in his patent. Although that is a correct descriptor I guess he assumed the reader understood transverse waves on a conical diaphram.
The wave velocity on the diaphram must be supersonic for all intended frequencies. The propagation velocity drops linearly with frequency.
Since wave velocity on a cone depends on bending stiffness a thin pliable cone might not even attain mach 1 even at high frequencies. Just wanted to clear that up. So, for wide band useage one would need an very stiff cone.

G (c)
 
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A Walsh driver is just a regular speaker where you are hearing the back wave sound instead of the front. The sound is not beamed at you the same way as the conventional configuration. It appears to be less efficient because it is radiated 360 deg. You would need a very strong motor and a very light cone to achieve high efficiency. That is not too hard to do but, at lower freq the wave propagation becomes evanescent. To overcome that you would need an extremely high bending modulus cone to start with. Graphene aerogel...? 3D printed
 
...the Ghost wanders in...

Hi C(G), Glo, 'n all the other fans of All This. *S*

'Bending wave'....I'm not a fan of the term since what the cone does is recreate the 'ripples' into the gas environment we like to 'air'. My take is we're wandering about in a low-drag pool of substance. 'Bw' could be applied to a frequency pulse traveling down cone; but, again, it's a ripple...

LF control can be controlled, as you point out, by the enclosure. You're inferring that you've been looking at an approach. Kewl...*G* I'm still looking @ acoustic suspension with an eye on minding a resonance. If I can 'park' it where it'll help vs. hinder, bingo....

3d print aerogel. A worthy target, but I suspect the $ for the prototype would induce mental implosion; dups wouldn't be distinctly less. I got a reply from a German firm that indicated a 2mil Al or Ti might be possible.
I just haven't had the time to reply with a 3d file for further discussion, but it's in the ToDo to follow up on it....

Went to PE to register for the Open/Unlimited contest, but their roster is already filled and closed. 5 entrants, 2 hrs. boils down to 10~15 of performance time after set-ups.

Asked to sign up for '21.

Still going to go in '20, if only to scope it out. Bringing earplugs, you bet. ;)

Meanwhile, because it was quick 'n dirty to do, took the Utah pair of woof 'n horn and set it up with the woof in a proper OhmCo configuration. The woofer could use a proper enclosure; can 'IT' be tubular vs. rectilinear? This combination shows promise of a sort. Either way, it's entertaining to FW. *G*

(Brazen ploy, to keep C/G in endless contact with the keys of his calculator...*L*)

...anyway....YouTube test pattern...*s* Back to the Shadows again....*poof*
 
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Thanks J. I was beginning to think I was a thread killer.

I don't like the term bending wave because to me it implies flexibility and compliance. Both of which counter wave propagation velocity which the Walsh patent depends on.

For the patent to work there needs to be supersonic wave propagation speed on the cone itself. With current technology this won't be possible with the lowest frequencies because transverse waves are dispersive. I once did a thumb nail figure for cone velocity and I got mach 30 something for the highest frequencies. At that modulus low frequencies would still be supersonic and thus coherent for the intended purpose. Full range operation is suggested for this invention. For that to happen IMO one would need a 3D printed cone structure of ultra high modulus material in some type of matrix form.

Some type of enclosure would still be needed to counter phase interference (w transmission line/waveguide).

G(c)
 
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In addition: I will say that the need for wave coherency will drop as frequency drops due to the wavelength increase. But, I think a starting point would around 700 Hz for the coincidence frequency. This 'crossover freq' would be within the region of information importance and of the enclosures ability to mode control low freq resonance.
 
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Now, That makes too much sense...

....and does explain Why the original Ohm Walsh's' had the 2 & 3 segment cones....
The titanium closest to the voice coil; not the lightest choice but outstanding strength to withstand the pistonic motion of varying degrees and speed.
The aluminum mid-cone: a lighter material medium to deal with the nuances of mid-frequencies, where most voice and instruments 'live'.
The paper 'base' cone: acting as the 'transfer medium' where radial radiation becomes pistonic for the bass frequencies, which require major excitation of the air medium. Literally, an air 'pump', moving mass quantities of molecules into waves....
And, as noted, acted as a damping medium to control high & mid frequency reflections back up the cone from the terminus of the cone edge. Lincoln W. posited some sort of 'damping medium' @ the surround to inhibit the back waves, including some sort of liquid or such....
Imagine..."Pardon me...I'm greasing my speaker's surrounds. They've been sounding a bit 'off' of late." *L*
700 hz seems about right....my AMT's prefer crossing over in that neighborhood to the woofers, with my sub around 200~300. These seem to vary dependent on 'source material'; voice varies with the performer's 'range', instruments ditto.
Watching my RTA's (one for input, a second 'listens' to the room with a calibrated mic) and sndpeek (displaying a spectrum, waterfall, and lissajous simultaneously which can do either) confirms this. And my ears and eyes seem to confirm this....IMHO, natch *G*.
Throwing active eq into the mix, one can nudge things about to taste so to speak. My ears indicate to me that my Walsh seem to like a mid-range 'shallow' that transfer nicely to the woofers and sub.
The age of my ears prefers augmenting the highs starting about 7K. Above that, hfq that I can't actively hear seems to add a near-tactile 'shine'. I can only refer that to the 'dog whistle effect'; there's 'something There that I can't hear directly, but 'there' none the less.....*shrug*

BTW, if anyone could 'kill a thread' it'd likely be me. *L* Wandering 'off subject', posting my eclectic musical mush that's way far away from dead white Europeans, and generally obscure attitude towards high $ equipment, aps, and adds. *L*
There was a near-insane TV ad for the SquattyPotty, featuring a unicorn that excreted an apparently delicious 'soft-serve'. At that point I considered the ad too weirdly amusing to be taken seriously, although the basic point of th SqPty is quite sound.
I suspect that I come off like that to some. ;) It's a gift. *LOL*
 
Jerry,

Concerning the PE Loudspeaker competition at the MWAF each year: You can register before the meeting but they do accept walk-in entries on the day of the event. Just get their early enough to sign-in and you should be golden. Five entries in the open/unlimited is low for the usual turnout. The actual duration of the judged evaluation is about 3 minutes but the open/unlimited entries do take a few minutes to set-up as they do take additional time to stage.

Although I did not attend (or enter) the loudspeaker contest at the MWAF this year, my Modified CBT24 speakers won the open/unlimited category in 2018. You can read about them at:

My New Line Array--It's a Modified CBT24

Jim
 
What goes around....

Hi Jim, and thanks for the big hint. ;) I'd somewhat resigned self to going to '20 just to meet with a forumfriend, check out the unlimited comp, and attempt to not fry my 'designated speaker budget' for the next decade. *L*

As it occurs, spouse is supportive of my venture to the event, competitive or no. Perhaps this is a side effect of a chance purchase of a pair of SMGa Maggies that she's enamored of their sound; this moment of weakness I hope to take advantage of...

To elucidate: "Those go in the living room....Deal?"

OhKay. Message received.... (After shy of 40 years, One Learns. *L*)

Took a side jaunt to your forum post, and the PE vid of your competition win (Congrats!). As for my 'what goes around' comment, what first drew me to DIY was an interest in line arrays. This was running parallel to Walsh drivers and what could perhaps be accomplished in a DIY approach....

It's obvious what won out in that regard. Ultimately, I wanted to investigate If I could attempt to create a variant of the original Ohms of the '70's that had less 'footprint' in a room, departed from the typical 'box' format, but could (at least) approach the response of a legend...

A tall challenge, to be sure. But I like to attempt the improbable with next to nothing... ;) So far...I'm perhaps overconfident, but willing to fail brilliantly. *L*

Just having a group of audioholics give a yay or nay at my venture will be an opportunity to get some 'quality feedback'; something I lack here in WNC.

(If you find yourself in the AVL area, PM and I'll pencil you in for an audition. I'm a tee shot from the Biltmore Estate...if I played golf...*L* We've got good food and what's becoming an incomprehensible number of breweries if that's a side interest....)

Anyway....it's be a kick to have the PE judges run the set-up tests on omnis, since they're known to be 'difficult to measure'. I'm hoping to not only have a pair but a self-powered sub to accompany them.

Just to make the concept that I'm working on an entirety. I'd like to have the 4 'satellites' with the sub that Really 'pushes the concept', but since it's typically pairs being demo'd....I'll play nice. *G*

But thanks again for the tip. Maybe we can meet in some fashion at some time. ;)

(Besides...*L*...now I owe you One).
 
Ruthless....

...esp. since I've never met anyone named Ruth...but that's beside some other point...*G*

This is what happens when I'm left with a pair of vintage Utah 2 ways. Crude (pardon the dirty PVC columns; 'spoof' in progress...) but effective in showing that one can make an omni out of almost anything. The horns are BRIGHT, given their efficiency; the woofs need a tad of damping, the columns need some legs to ensure no undesirable trips to the floor...not to mention some TLC re the algae removal. But they mate to the sub nicely and play well with my current Walsh...

20190918_011816.jpg

20190918_011924.jpg

Fun distractions...;)

And, given 'current information'....all else is moving along at it's own pace 'n space. *S*

I wonder, and am open to any comment on:

Has the MWAF open competition ever had an omni submission?
 
Jerry, the MWAF competition is typically held in a very large meeting room--lots of space to all walls and ceiling so it should be perfect for an omni. I linked a photo of me presenting my Modified CBT24 speakers at the 2018 MWAF. Notice the space around the speakers with the three judges seated at a table in front about 12-15 feet away from the speakers being tested.

You are welcome to visit with me in Cookeville (on I-40 about half way between Nashville and Knoxville) if you pass through this direction.

https://midwestaudio.club/wp-content/gallery/mwaf-2018/DS56585.jpg
 
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*G* Thanks for the pic, Jim. I've generally been under the impression that line arrays tended towards taller dimensions. It allows me to have a better handle on the heights of the variant versions. My current Walsh are *mmm* 'bout 6" lower than your CBT's. I expect the version I'd present will be +/- 3" shorter, dialing them in for proper dispersion for a seated listener.

It's great to 'get a clue' as to the presentation space; the back wall reflections may raise some commentary but I'd hope that the judges will take that into account in their impressions. Since omnis radiate 360 vs. 120~180 their perceived 'loudness' tends to be thought lower than a direct radiator.(*) This may be a reason why the original Ohm/Walsh got the 'sounds great @ 200w., blows @ 201' tag. I'm approaching that by employing drivers built for abuse in that regard. *S*

And thanks for the invite for a visit. It might be awhile until I could be out your way, however. The last time(s) I passed through on I40 was to travel to & from D/FW on an installation nearby, or to visit an old friend who 'commutes' every summer to a family farm in Metropolis,IL from San Luis Obispo, CA. But one never knows....*S*

*= I get around that by tending to have 4 in a surround array; as I've noted, what happens 'in the middle' can certainly be loud enough for most. *G*

Anyway, I runneth off at the keys as usual. Thanks for the pic and the info, and have a good week as we wait for Fall to fall....;)
 
Finally getting around to playing with hf drivers above the 'full range' drivers I have....

With 3 pairs of various combinations, I ought to be able to stay out of some trouble....

..and stay in trouble with the other trouble..*L*

Just a glutton for hassles....;) At least these are self-inflicted...I can walk away when miffed....;)
 
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