Ohm Speakers, thoughts?

As I recall the driver was made of metal for a couple of inches at the top (near the voice coil) and this part of the driver supplied the high frequencies. In other words, the HF did not propogate all the way down the cone. So, although there is no electronic crossover, there is a mechanical crossover, a point that I stress for all single driver designs.

The Ohm A's used two different sections of cone and the F's used three different sections of cone, all seemed together mechanically. The Ohm A's had a larger cone with a non-linear flare rate whereas the F's had a smaller diameter cone that maintained the same flare rate for the length of the driver. The differences in materials, cone mass and driver geometry all add up to differences in radiation pattern, transient response, etc... As such, even though the A's and F's are TRUE "Walsh drivers", even they differ from one another in design and performance.

As a side note, the Ohm G used a smaller version of the Walsh. Due to the cabinet design, the radiation pattern was not nearly as omni as the A or F. This not only changes the sound that one hears, but also negates many of the spatial properties that make the Walsh design special.

Due to using a smaller cone with the reduction in piston area, Ohm was looking for a way to augment the bottom end of this driver. They did this via the use of a passive radiator. Passive radiators have the slowest transient response of any vented design*. As such, the bass on such a design typically sounds very "heavy" i.e. thick and powerful, but lacking in definition due to slower rise times and a lack of damping i.e. excessive "ringing" once excited.

While passives are great for HT use where "earth shaking" bottom end is more desirable, they really have limited use in a "hi-fi" system. Passives are, once again, another form of venting that achieves "quantity" over "quality". Sean
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Sean, I purchased my first pr. of OHM WALSH on Nov.3 1987, the 4-XO's. A Technical White Paper came with those speakers to explain too the purchaser how they operate and here is what it says in part....

This cone is fabricated of special materials which have a super-sonic velocity of sound propagation. By engineering the cone angle and propagation velocity properly, a coherent, cylindrical sound field is synthesized in the air around the cone; the listener, in fact, receives simultaneous sound.

As described previously, the apex of the cone is initially dent, and a sound-wave originating at the apex moves into the air at 1100 feet per second. Similarly, every point on the cone contributes its output at exactly the right time for ALL the wavelets to coherently merge into a cylinder, as shown in Figure 3. Wherever the listener sits, all the sound produced by one pulse reaches the ear at the same instant. There is no "time-smear" or "time-delay distortion". END QUOTE

That is a description of a Walsh driver; the angle of the cone is just different from the F's angle because the material used to make the cone is different. The speed in witch sound travels in materials is dependent on what kind of material is being used and the cone angle has to be adjusted accordingly. This is why the angle of the cone in the newer Walsh drivers is different from the F's cones.

Just because the newer Walsh drivers are not mounted on a sealed cabinet does not change the fact that the driver itself is operating as described above.

What Eldartford said:...That there is a mechanical crossover at the point where the two dissimilar materials meat, is indeed a crossover.

Line: Stop reading and believing the propoganda put out by various manufacturers and start learning for yourself.

Pull your Ohm's apart and find out what you've really got once and for all. Once you find that out, maybe then you can tell us what the "special materials which have a super-sonic velocity of sound propagation" really are.

I'm not certain that i'm ready to hear or experience a "sonic boom" up close and personal. Sean
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Sean, The term "super sonic" literally means faster then the speed of sound in "air". Sound travels faster in solids then it can in air. Therefore the sound wave traveling down the cone material of a Walsh driver, is at "super sonic" speeds. This is a scientific fact. How much faster the wave travels down the cone depends on the material being used to form the cone and the speed determines the angle of the cone. The correct angel lines up all the waves generated in the air to form a single coherent sound source, with no time-smear or time-delay distortion.

Sound travels at different speeds in different materials such as steel, plastic, water, air, etc. No, it does not create a sonic boom because there is nothing traveling in the air itself at "super sonic" speeds, the wave is traveling down the material. This is how the F's work and all speakers that work on Walsh's principal.