Ohm Speakers, thoughts?

Here is a link to a description of the 'bending wave DDD driver'
http://www.german-physiks.com/NewFiles1/DDD.html

That post didn't look like a joke, so I did a little research too find out just how fast sound does travel in some of these materials and here is a little of what I found...>>

In general, sound travels fastest through solids, slightly less fast through
liquids, and slower through gases.

This is because the particles (atoms or molecules) in a solid are touching
each other and rather fixed together. That is why a solid is "solid." Since
the particles are bonded together, a sound wave moving one, immediately
transfers the motion the one touching it. A sound wave hitting one, is
almost immediately transferred to a neighbor.

In a liquid, the particles are touching each other, but they are not fastened
to each other quite so strongly as they are in a solid. Some of sound's
energy is wasted pushing the particles around because they can slide past
each other. Some of sound's energy is wasted that way and that is why it
moves slower.

In a gas, the molecules are rather far apart. For sound to travel through a
gas, the molecules must move quite a distance before they collide with other
molecules. Sound energy cannot move as quickly when the molecules are not in
contact with each other.

Here is another from a different site...>>

In air at room temperature, sound travels at about 340 metres per second. In water, sound travels about four times as fast as it does in air, while in steel, the speed of sound is about fifteen times as great as in air.

Here is one I found interesting,..Why do we sound like Donald Duck when we talk with helium...>>

We talk like Donald Duck because sound travels faster through helium and, in effect, shrinks our heads.

When we speak, the sound speeds from voice box to lips. Since sound travels faster in helium, the sound reaches our lips sooner with helium than air. It’s as if the path were shorter. The faster sound speed raises the resonant frequency of our vocal tracts. We, sort of, become Oz Munchkins with high squeaky voices.

Every pipe, from our vocal tracts to an empty Coke bottle, has a resonant frequency. Blow air across a bottle. The deep sound we hear is the bottle’s natural frequency in air. Fill the bottle with helium and blow across the top. Now, sound travels faster and the tone sounds higher. The resonant frequency of a tube depends on the length of the tube and the speed of sound through it. The faster the sound speed, the higher the frequency.

Well anyways, I bought my first pr. of Ohm speakers from a big box store called ABC Wharehouse purely on what I was hearing out of them, and at that time I did not know what was going on under that can, just liked what I was hearing.

Some 15 years latter, I started hearing something that I should not be hearing out of one of them, so I opened it up and found the surround tore and replaced it with a new one. I left the can free so I could slip it on or off any time I wanted to. "And yes, I always wondered what they would sound like with the can off." So, many times I would listen for a different in sound between the can off and on, and I could 'not' here any difference.

The driver is not a mass projection driver; this is very apparent when it is looked at. They look hand built, and I believe they are. This tells me that this driver is NOT ordinary. No; I can not know what is going with this driver by looking at it. The cone is some sort of plastic, the magnets look massive, and the can is essential to protect some kind of (what I believe to be) some kind of sound absorbing material that is placed is certain places. The driver is not pretty, in fact, I think it is ugly, but it can't be seen anyways.

I don't have the XO's anymore because I upgraded too the Walsh 5 Mk-2 drivers and mounted the on the original trapezoid cabinets. I do not know what the new divers looks like with the can removed.

Now Ohm does have models that are box speakers, and I would bet that the drivers in them are production speakers, (not hand built).

Sean, I have a question for you...Do the F drivers have a spider? I think that they would have to.

http://fullrangedriver.com/forum/viewtopic.php?pid=6485

If you read this thread, you'll find someone else commenting on the type of drivers used in newer production "Walsh" series. For the record, i never posted to this thread in any way, shape or form, even if one of the participants shares the same name.

As a side note, there's a "funny" story pertaining to the design motivations behind Decware's "Radial" speaker mentioned in this same thread.

John, the owner of Van L Speakerworks ( aka Chicago Speakerworks ) had previously verified to me that newer "Walsh series" used conventional design woofers firing face down into the cabinet. He has re-foamed many of these drivers over the years.

Yes, the F uses a spider. Sean
>

Sean, I appreciate you sharing your knowledge, but there is something I don't understand after reading this quote from the German-Physiks files.

The transmission line type has commonly employed a steep, straight-sided cone and a fairly conventional voice coil and magnet assembly. But where it differs from an ordinary mass loaded cone is that the diaphragm is securely anchored at its mouth and flexed by the motions of the voice coil rather than pushed to and fro. Sound propagation is normal to the slope of the cone rather than parallel to the path of the voice coil in the gap as is the case with a mass loaded cone.

The diaphragm is securely anchored at its mouth. Wouldn't this mean that there is no spider employed ? And is sounds as though there is no surround employed ether.

What I am trying to get at is; the F's do employ a spider and a surround, and I am wondering if the sound emanating from the F's is a mix of conventional speaker sound and transmission line sound. What do you think? Am I missing something?

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?