Ohm Speakers, thoughts?

Dale,

Would you mind sharing some photos of your re-creations?
Also, if it doesn't involve giving away any secrets, would you mind discussing the improvements you have made to the original designs (both A & F)?

Sean,

The following is quoted from a Six Moons' review of Ohm's Walsh Micro speakers.

Ohm Acoustics manufactures two very different types of loudspeakers - the usual cone'n'dome variety (certain models incorporating different ideas on dispersion) and their claim to fame, a complete line of speakers using the Walsh driver based on the work of the late Lincoln Walsh. Years of refinement have created what Ohm calls the CLS or Coherent Line Source driver. Picture a typical cone woofer elongated in depth akin to a megaphone - but not quite. Now point this driver downward so that it fires into the top of the speaker's enclosure. Sound propagates off the back of the driver rather than front, and by virtue of its open-air surroundings, in a 360-degree rather than narrow-directivity dispersion pattern.

States Ohm Acoustics on the subject: "The CLS system uses an inverted cone driver with the speaker coil driving the peak of the cone. The sound vibrations travel from the top down and out to the rim.

By using a cone material in which sound travels faster than it does in air (supersonic) and by carefully aligning the angle of the cone, the driver generates a vertical wave front, radiating sound equally in all directions like an expanding drum. Because the inverted cone driver radiates in all directions, it sounds the same in all directions." In other words, the driver is naturally time-coherent and omni-directional. But Ohm feels that, with certain circumstantial exceptions, an omni-directional response in the treble is undesirable. Rear-wall reflections at these frequencies can become confused with the original sound and consequently blur imaging. Hence, in addition to the CLS main driver, Ohm adds a "super tweeter" mounted vertically at the Walsh driver's top and angled inwards so as to cross its main axis well in front of the listener. This tweeter is reportedly pressed into service around 8 kHz which eliminates a crossover network anywhere near the critical 2-6kHz range where human hearing is most sensitive to discontinuities.

IF the description is true to the design, I find it hard to believe that the CLS driver is not a derivation of the original Walsh driver and is just an inverted speaker. True, the Ohm F's had a longer ~12" cone (not including the motor), but it also covered the complete audio range (37 - 17,000hz). The new CLS cone (I am talking about the Walsh 5 Mk II) is only ~5" - 6" tall (hard to tell from the drawings) and only covers the claimed 20 - 8,000hz range.

Think of it this way. If you took a full range driver, mounted it into a cabinet ABW (ass backwards), would it still be able to produce the mid to high frequencies as a correctly mounted driver?

I am not saying I am right. There just seems to be too many inconsistancies posted. Just trying to find the "truth" (if that is possible).

Sean,

Glad you are looking at this thread again.

Not being one to accept all claims, I decided to do some investigating. First, I wanted to find out just what constituted a Walsh loudspeaker. I looked up the Patent #3424873 (in case anyone is interested) and began my research.

The following is from the Abstract:

"Abstract of the Disclosure
The coherent-sound loudspeaker is a development derived from a theoretical concept of ideal sound reproduction by means of a conical diaphragm operating as a wave transmission line. Such a conical diaphragm will produce sound as it would be produced by a small cylinder pulsating radially with every portion of its area moving in and out simultaneously, and in phase with the input audio signal. This is coherent sound.
The requirements of the theoretical concept are closely approached by a sound producer of the following character:
(1) The angle of the conical diphragm, measured from a plane perpendicular to its axis is quite high, causing the speed of the mechanical vibratory waves in the diaphragm to be greater than the speed of sound in air, and to have a component in the desired direction of sound radiation equal to the speed of sound in air.
(2) Absorbing material absorbs the wave energy in the diaphragm to eliminate or minimize wave reflections from the non-driven end, so that a vibratory wave transverses the diaphragm substantially only once.
(3) Sound is radiated to the listener only from the convex side of a vertical conical diaphragm to obtain full frequency range, high quality sound omnidirectionally from a single radiator."

Four models are mentioned in the patent. Models B and J's diaphragm were made of felted fiber. Models L and M's diaphragm were made of aluminum. Other variations between the models are described. If you want to know more about them, lookup the patent (it's in file DImg-11.tiff).

Quoting from the results:

"The low end of the useful frequency range of all of these loudspeakers is approximately 40 cycles per second. The upper end was about 14,000 c.p.s for Models B and J, 16,000 c.p.s. for Model M and 34,000 c.p.s. for Model L. The frequency range of the Model L extending to 34,000 c.p.s., well beyond any person's audibility limit, confirms the theory that this new loudspeaker can be designed for any frequency range desired, although at some sacrifice of efficiency for wider ranges."

Throughout the patent, several items are mentioned to "fine tune" the design. One item is the basket for the driver. Normal drivers usually cover 30% to 100% of the convex side of the driver. A Walsh driver should be obstructed by less than 20%. The only other item I will mention is that the angle of the conical driver must be at least 50 degrees.

From the patent, I have concluded that only the Ohm A and F meet these criteria. The Ohm G is a hybrid version and is therefore not a true Walsh loudspeaker. (as you have already said) All of the other models are not "true" Walsh loudspeakers.

However, a Walsh driver can be "designed for any frequency range desired". So the claim that Ohm's "Walsh" line of speakers use a Walsh driver could be true.

I had asked a question earlier (please see prior post) that if Ohm is not using a Walsh driver, how could they reproduce the midrange using a downward firing driver? (still looking for an answer) I went looking for any photos that would help verify Ohm's claim and I came across these Ohm FRS 11's (I think).

From Ohm's website:

"The FRS-11 is a tall square tower with each corner cut about 2''. One of the cut corners displays the Ohm logo near the top, just below the grill. The FRS-11 is a true Walsh speaker designed for small to medium sized rooms. They create a precise stereo image from a very wide Sweet-Sweep. We call the effect Full Room Stereo and we named it after this benefit."

Looking at the picture, if indeed this is an unmodified FRS 11 (except that the diffusion cans have been removed) there is no Walsh speaker/driver to be seen, and it is truly just a conventional woofer/tweeter combination.

My question now is, is it ethically, morally, politically... correct to keep calling the line a Walsh speaker?

Line, Sean,

Your welcome. As I stated before, I am just searching for the truth.

Line:

One thing I would like to say, is that the cans are not diffusion cans, they are as transparent too sound as grill cloth is.

Sorry, I have to agree with Sean on this one. I know of no grill (cloth or metal) that does not affect the sound in some way. (of course I have not heard all speakers with and without grills; I could be wrong, I could be right!) ; )

Sean:

As far as the Ohm G goes, i think that it is a Walsh driver by basic design, but i'm not sure about the flare rate on the cone. It obviously has a LOT less surface area than the Ohm A or Ohm F Walsh drivers. The "standard" cone driver that you see in the G cabinet is a passive radiator, not a driven woofer. I've never seen one of these in person though, so i'm kinda sorta guessing on this one based on photo's / technical info that i have.

Yes, the Ohm G does use a Walsh driver but is not a "true" Walsh loudspeaker since it uses the energy from the concave part of the driver to power that passive radiator. (I am being a stickler to the original parameters of the patent)

I also have some Walsh "tweeters" that Infinity made, but i've never tinkered with them.

I almost bought a pair of Infinity's with the Walsh tweeter back in '76. I wish I had, it would have saved me money on a Transcriptors Skeleton turntable! (They were both part of a system I was pondering at the time)

If anyone is curious about the Walsh Loudspeaker, I encourage you to take a look at the patent (see previous post). There is a lot of technical information there but there are also things such as:

" A single very large coherent-sound loudspeaker might be built to serve a stadium of 100,000 listeners with high quality music and voice. It might have a vertically oriented conical diaphragm with an angle of 60 to 80 degrees, a diaphragm diameter of approxmately 60 inches and a height of 60 inches. The diaphragm might be of a composite aluminum and elastomer to substantially attenuate 16,000 c.p.s. waves in a vertical distance of 3 to 6 inches, and 4,000 c.p.s. waves in 12 to 14 inches, to obtain good diffusion of sound vertically. It would inherently have uniform diffusion in all directions horizontally. Its frequency range might cover 60 to 16,000 c.p.s. and it could handle well an electrical input of 500 watts with extremely low transient effects and other types of distortion. Its uniformity of response might well be about 1 db over the rated frequency range."

I would love to see this become reality! Any takers?

Also, any takers on my question; is it ethically, morally, politically... correct to keep calling the line a Walsh speaker?

If anyone has any doubts about what exactly constitutes Ohm's new version of a "Walsh" speaker, check out John Strohbeen's Patent #4440259. It is all spelled out. (Click on the images button to see the drawings)

Warning! Ohm posting that failed to, well post. (Sorry, some of this was written 2 days ago and I am trying to catch up.)

This is a recreation of what I think I said:

Line:

Jamscience, now we can argue over...'Is John actually marketing what he had patented .

No way, no, no, NO! And my Mom says you can't make me! ; )

BTW, I think someone just put up a pair of 4XO's on eBay.

Lngbruno:

What was the MSRP of the F’s back in the mid to late 70’s?

According to Ohm:

Production Period 1972 - 1984
Nationally Advertised Price originally $900 - $3995 per pair

Question - What is preventing a Manufacturer from building an authentic Ohm F again?

Is it the licensing?
Is it the technology?
Is it the patent?
Is it the cost of producing them correctly?
What is it?

IMHO it is the cost associated with building them.

I am not a lawyer or a telephone sanitation engineer, so please excuse any mistakes I may make and feel free to correct them.

The patent ran out in 1989 (20 years if you keep up with the maintenance fees). (I personally believe it should be 42 years) :) If I understand correctly, once a patent is up, anyone can create that object according to the patent. If you modify it in any way, you have to apply for another patent or risk having someone or corporation competing with you using your modifications.

I have a problem with Ohm's excuse of running out of craftsmen to build these speakers. People can be trained to produce just about anything. It's just a matter of time and money. I also realize that it does cost a lot more to have something built by hand instead of by automation. John Strohbeen's patent refers to the cone and voice coil in the original Walsh patent as being expensive to manufacture. My take on this (and this is only opinion) is that the bottom line was being eaten up and to justify continuing to produce a "Walsh" speaker, a new design was needed to be equal in performance but less costly to make. Whether they succeeded is a matter of opinion.

Why does Ohm still use the Walsh tradename? IMO because they own the trademark indefinitly (as long as they pay the maintenance fees) and because of brand recognition. At least German Physiks had the cojones to name their driver by the inventors name; DDD (Dick Dipole Driver) yet give credit to Lincoln Walsh. Ohm could just as easily name their driver the SCD (Strohbeen Coherent Driver) or even the STD (Strohbeen Transmission-line Driver). OK, maybe that last one might be a marketing mistake!

Sean:

This type of design would have to be hand built using custom parts i.e. minimal off the shelf componentry. As such, it would be a relatively large economical undertaking for someone to attempt as compared to starting up a speaker company that uses off the shelf parts. On top of that, the market for such an item isn't all that big in the grander scheme of things, hence the lack of anyone jumping in with both feet.

Having said that, i can see this type of thing taking off if someone were to build "one off" products out of their garage. That is, IF they could achieve the type of results that we know this design to be capable of AND doing so with a high level of consistency. I have thought about this myself, but not too seriously. Sean

Maybe after creating a new prototype, an ingenious mechanical engineer could build a machine for mass producing these speakers (or at least cut down on some of the handwork. Of course one would have to charge outraegous amounts of money for these. (maybe in the range of $15,000 - $40,000) I don't know if there would be a market for such an expensive speaker? Would anyone buy a $40,000 speaker? ; )

When I hit the Lotto, I'll be giving you a shout!

Lngbruno:

I think, even built by hand, these speakers wouldn't be as expensive as was stated above.

Actually, I was being facetious. (just thinking of those 60" cones!) The real problem is recreating what has already been done. It's one thing to modify an old Model F; it's another one to build it from scratch. Just a crude guess would be (per pair):

Materials - $2,000.00 - $3,000.00
Labor - $2,500.00 - $3,000.00
Outsourcing (for things that you could not afford to do as an individual) - $2,000.00 - $3,000.00
Testing and breaking in - $500.00
Things not thought of - $1,000.00

Total cost - $8,000.00 - $10,500.00

Plus the cost of getting a new patent for any new improvements. $????.??

Am I anywhere close to the mark Sean?