Ohm Speakers, thoughts?

Hi Jamscience,
Sorry I haven't gotten back sooner.
I have remained pretty faithful to the old design in order to maintain a baseline. However, I have hopefully improved on the voicecoil, making it substantially lighter and able to withstand more power. My newest coils will be in production very soon, up to now, I have hand made each and everyone. I am also working to improve the suspension and dampening of the cone.
As for pics, I am happy to share some, just drop me a line at my home email...dale@hhr-lasers.com.

Hi Guys,
For what is worth, I am now offering the Ohm Walsh F+ and A+ by Dale Harder, in limited productions, with exotic hardwoods and some 30+ improvements beyond the original models. Some of the improvements are: New cones, improved magnets, stiffer spiders, lower weight high power voice coils, box stiffeners and resonance control, Cardas gold connectors, silver Litz wire leads. I also refurbish completely, older models and upgrade them, cabinets and all.
If your interested please contact me for info, pictures, etc. dale@hhr-lasers.com 440-888-2163
A new web site is forthcoming.
I will also be offering new and refurbished high power tube amps and full range ribbon systems.

Regarding the Ohm Walsh F and A Loudspeakers. The purpose of this guide is to provide potential buyers and users much needed clarification and information regarding the magical and little understood Ohm Walsh model “A” and “F” Coherent Wave Transmission Line Driver/Audio Speaker from the 70’s and 80’s. I will not go into details of the previous guides here, but I will attempt to clarify many misconceptions and incorrect information which has arisen throughout the years. Let me begin by saying, unfortunately, not only have these speakers had a tremendous amount of misinformation disseminated throughout the years, but there are also many dangers presented by perhaps well meaning individuals whom attempt to recone these old units and sell them on e-bay and various audio markets as “working” or “refurbished”. This is the furthest from the truth, for no one, not even Ohm Acoustics, rebuilds these any longer. So far as I know, and it is my humble opinion, but, I am currently the only person in the world that can build these units from scratch or refurbish the old units, including cabinetry and some 30 upgrades to materials and performance specifications. I am here to tell you in no uncertain terms that these speakers represent some of the most sophisticated and difficult to build audio transducers ever made and mass marketed while still representing some of the finest musical reproduction capabilities of any speaker ever devised ranking easily amongst the finest speakers in the world for decades. The capabilities of these drivers, when properly executed, have been known to rival and compete with many “cost is no object” systems such as full range ribbons, Apogee, Quad ESl’s and Infinity’s super IRS standard systems, costing $60,000 in the 70’s. At the time of their final production in 1984, the Ohm F model commanded as much as $4,000 retail and the “A” model commanding $6,500. The drivers truly representing the word “exotic” and the cabinetry bordering on works of art. As many others have stated the driver of the “F” model consists of a steeply inverted cone standing some 12 ¾” in height with a slant of 75.5 degrees. The cone is constructed of two metal foil sections and one paper section. The top third is made from titanium foil having a thickness of .0025”, the mid section is made from polished and tempered aluminum foil, (Not Stainless Steel), having a thickness of .003” and finally the last section is made from felted paper having a thickness of .025”. The finished cone weighs an incredible 124 grams. I would like to mention that aluminum foil off the shelf from “Reynolds” will not do the trick here. While the above materials represent the bulk of the cone, the magic of their function lies in fact in the treatment and correct assembly of each section. To be brief, the top titanium section has a special treatment applied to its internal surface that acts as a sound absorber, a stiffening agent and cone nodal breakup control. It resembles grey modeling clay, but it isn’t, and lasts a good deal longer. However, be aware this material is critical for proper operation and it does dry out and crack after 15 to 20 years, so it should be replaced. Reconers never do this, let alone know the proper materials to use. Next, the Aluminum section is also treated internally and externally in several special ways. Externally, the cone has ribbing lines running vertically for the entire length of the aluminum section that have been scribed into the aluminum at precise intervals, depth and angle. This ribbing helps to make the cone stiffer, but also is used to “tune the cone”. Internally, the foil is covered with a specially selected grade of “open cell” damping foam of precise thickness. The foam runs the entire length of the aluminum section and covers about 1/3 of the titanium. One of the most important things overlooked or not attempted by refurbishers is the replacement of this special foam. One reason is because it is very difficult to remove the old and then equally difficult to replace the new. In addition, this foam is not readily available off the shelf. If the foam surround is decayed from aging, as all units now are, then the internal foam is decayed as well and MUST be replaced regardless of weather it looks OK or not. Typically this foam crumbles or rots turning into “gooey” fragments and falls of in gobs if touched. It is used for damping, control of cone ringing and control of the speed of the wave front traversing the cone. The final cone section of the “F” model, the paper is perhaps my favorite when it comes to being misunderstood and overlooked. The bottom third felted paper section servers many functions, but is most responsible for producing the lower bass frequencies of the driver. A close examination reveals lots of slits cut into the paper and what looks like silicone seal applied to the internal side of the cone. My favorite story is perhaps one I read of an individual that sent his speakers to be repaired only to find upon their return that the silicone had been applied to the slits that he had so carefully had peeled off, thinking that someone before him had placed it their as some sort of repair. He was incensed and demanded a full refund because he felt the speaker had been incorrectly repaired. Here again, this sealant MUST be there and must be applied correctly. A closer look will reveal 4 rows of slits placed horizontally in exacting positions across the cone surface. These slits control cone break-up, provide a properly terminated high loss transmission line and prevent reflected sound from the cone annulus from returning back up the cone and interfering with the oncoming wave. Further, the paper is treated with a properly positioned internal “ring” of paper that is also a stiffener and produces a density change in the material. Finally, the paper portion is terminated with another paper “ring” that is cut and glued to the main paper body, again producing a state change and acoustic signature. Now that we have a basic understanding of the driver’s conical section, let’s examine the remaining and very critical suspension and compliance portion of the Walsh Driver. The suspension of this transducer consists of some very familiar parts, namely a foam surround and a spider roll as is commonly seen in many piston driven speaker assemblies. As many of you may know the stiffness of the spider and the thickness of the surround as well as the type of materials used, combine to form a system that controls the driver’s acoustic parameters. These parameters are based upon some of the Thiele and Small calculations and are critical for the system to produce the desired frequency response, desired bass roll off, total system impedance, high end response and box functions. The suspension is designed to work with either a ported or sealed enclosure. Changing any of these components represents significant changes to the overall system performance and can make or break the speaker’s ability to reproduce realistic sound. Trust me when I say, that not just any old “off the shelf” foam surround or any spider of the same size and color will work in the proper function of these drivers. It will not! Any reconer or refurbisher that try’s to use stock parts will obtain marginal performance at best. I would also mention that reusing the old spider is not advisable since most have been stretched considerably due to the weight of the cone pulling it down for many years . The surround not only suspends the cone and correctly centers it, but is also provides for critical damping of the acoustic wave as it reaches the end of the cone and thus prevents most of the acoustic energy from being reflected back up the cone. The spider serves to center the voice coil and provides mechanical resistance to the driver’s motion. This mechanical resistance couples with the voice coils DC resistance to produce the speaker’s total impedance or load to the driving amplifier. Will it play you ask? Yes, the speaker may play, and it may even sound acceptable to some, but it will be far from optimal and therefore far from being one of the finest speakers in the world. More than likely, the speakers will sound dull, lackluster, even muffled in the high end. The clarity will suffer on voice reproduction and choral groupings. The bass will be dull, slow and lack articulation. The difference is a hand made sports car compared to a small compact model. Once again, to my knowledge, I am the only person in the world that has these items made to order and to my specifications so as to be compatible with the originals and or the enhanced new units that I build. Finally, we come to the very heart and soul of this phenomenal driver, namely the voice coil. The voice coil is not only responsible for providing the electrical impulses that are transformed via. the interaction between the electrical input signal and the high energy Alnico magnet, but it also represents the power handling ability of the driver and its ability to produce the highest frequencies as well as the lowest simultaneously. Unlike any other driver, this single voice coil must be capable of functioning over the entire audio range of 20 Hz to 20 KHz. and beyond. This transducer is made from a very thin anodized aluminum ribbon wire with a rectangular cross section that is wound on the tall edge and adhered to the inside of an anodized aluminum former. The coil consists of a single layer and must withstand extreme temperatures approaching 300 degrees C during operation, and yet, it must also be extremely lightweight, since the mass of the VC represents the critical mass of the moving system that must be accelerated or decelerated in order to pluck the cone and produce the highest frequency sound waves. The original goal was to have a VC that weighed less than 4 grams. Because of this, the Walsh driver is the only speaker in the world that can successfully pass a square wave retaining more than 95% of its original shape. I would like to point out that there are also variants of this coil that are used in different “F” cones and also the Big brother Ohm Walsh “A”. Having said this, please understand that there are NO substitutions for these coils and the use of any other type of coil, wire, winding, form etc. from presently available stocks will not work. As with the other parts, I make these coils to order and have them expertly wound to my specifications and application. While I have endeavored to present the Walsh “F” in considerable detail, one may infer from this information that the Walsh “A” functions in much the same fashion and in theory this is true. However, the “A” is an entirely different version of the Walsh principal in action, having a cone with a nominal 18 inch size. This driver is only slightly taller than the “F”, but has a dual flare cone and is made entirely of metal foils. The top section of the cone employs a 3 inch voice coil similar to its smaller brother, but of a nominal 8 ohm impedance. The top portion of the cone is made from thin titanium foil and employs a steep angle of 75.5 degrees. While this section is somewhat longer than the “F” cone, where the titanium meets the aluminum section the cone flares abruptly to a cone angle of 62.5 degrees. There it continues to the entire extent of the cone body and ultimate diameter of approximately 14.5 inches. As with the smaller “F”, the cone is terminated by a special cloth pleated surround, designed to do exactly what its foam counterpart does in the “F” model. The actual size of the driver is a misnomer and is more truly measured at 16 inches to the outside of the surround and 18 inches to the driver frame. The cone is completed with treatments to its inside with putties, foams, diamond shaped hash markings for stiffness and for tuning. The “A” represents an unbelievable work of art, form and function. Sonically, it has no equal with the ability to go subsonic and produce thunderous bass while simultaneously producing the full subtle air of voice and delicate articulated highs. Not bad for a cone that weighs more than 346 grams. In conclusion I would like to reiterate that the Wash “F” and “A” Transmission Line drivers are extremely difficult to build, highly complex in their execution and make considerable demands on construction techniques and materials even today. In fact, just to show how much thought went into the design of these speakers consider this…every glue in every joint was chosen for it sonic properties as well as its merits as an adhesive. I would like to share you with a little back round on myself. My name is Dale Harder and I reside in Parma Ohio. I am an Aerospace, Laser, Electro-Optics and Audio engineer, and have been in these fields for more than 30 years. My long love affair with the Ohm Walsh Speakers started in 1972 and to my knowledge I am currently the only person in the world that can still build true “Walsh Style” drivers from scratch or refurbish the old Ohm Walsh units including cabinetry. I have devoted much of my life to improving upon this series of speakers purely for my own enjoyment. I would also like to state that I am in no way connected with Ohm Acoustics nor they with me at the present time. The information that I have given is from my own learning and experience and while I have endeavored to be accurate and true, I assume no responsibility for any of its use or content. Further, I do not manufacture these speakers under the name of Ohm Walsh “A” or “F” as that would be a trademark infringement. I simply emulate the Walsh principals. I do however manufacture new drivers and complete speakers or refurbish older units with some 30 + improvements using the Walsh "A" or "F" as a base guide. The new speakers are called the Walsh TLS-I and TLS-II Lastly, I Do Not sell parts for do-it-yourselfers, sorry, so please don’t ask. I hope this has shed some light on these unique speakers. Thanks and Good listening, Dale Harder. dale@hhr-lasers.com

Gentlemen,
I think you have completely missed the point of my long treatise and the purpose of adding to this thread above. There is no comparrison to the old Walsh "F" or "A" relating to the current products.

The current products consit of two standard pistonic drivers, one being an iverted woofer and the other being a dome tweeter. This arrangent borrows a very small likeness to true Lincoln Walsh design and for lack of a better word "tricks" your ears into hearing somewhat onnidirectional sound, when in fact, it is only 180 degrees in dispersion. The back wave is suppressed from the woofer and the tweeter fires only frontward at a 45 degree angle to the norm.

The current product uses a complicated crossover network and is not truly time and phase aligned nor is the sound coherent. The Walsh principal, IMHO, is the finest speaker principal ever discovered, only the implimentation of that discovery has ever been lacking. Had it reached its full potential almost all piston drivers would be gone.

This is not to say that Ohm Acoustics has not done a fine job with what they currently offer, but true Walsh drivers they are not.

A Walsh speaker consists of one steep angled cone made to behave like a transmission line. It has no phase or time distortion, emits in a full 360 degrees and the sound wavefront is fulluy coherent just like a laser beam. There are no crossovers whatsoever. Placement is not super critical and the sound stage does not wander. If there is a sweet spot, then it is extremely wide and very, very accomodating.

The Lincoln Walsh discovery lives on in my NEW presentation of the "Waslh TLS" series of drivers and systems.

Please undertsand once again everyone that I am in no way bashing Ohm Acoustics products. In fact, I have a long love affair with them and they are the ones that did start this thing in the begining. They hooked me in 1971 and I have been hooked ever since.

In Honesty, the only other speakers I have ever heard that turned my head for a moment was the Apogee line of full range ribbon drivers and their new predecessor. But here again, not worth $50K.

John Strohbeen has done very well with his current line of products and they are quite affordable. They have even borrowed upon some of the sonic merits of the original Walsh ideas. But, none the less, they are still piston drivers. Albeit, the woofer has been made to behave like a bad transmission line, which is exactly what the original Walsh idea was. That is not a bad thing, just another avenue.

The true transmission line drive exists only in a trucated version designed by German Physiks or Ikonoklast. The latter utilizing the Walsh tweeter design and the G.P. design resembeling more of the Old Ohm G product. But IMHO, not worth $21,900 for the cheapest model.

By the way, there is a new kid on the block nipping at Ohm's heals with an new entry in the omni market very similar to the current Ohm products made by Rountree Acoustics. (Not Roundtree) It's called the Omnimon. Covered in Stereophile mag this month. Also online.

Regarding the Walcott speakers.. just another piston driver firing into an omniball for dispersion. Not a walsh driver or anything similar.

I have been a speaker engineer and desingner for most of my life and I have made all manner of speakers including exotic plama drivers. But to my dismay, the worst design of all, the piston driver has for wahtever reason prolifferated. It is a bad idea that just won't go away and hence my steadfast approach to the Walsh design.

Anyway, my whole point is to make people aware that this style of speaker is available again, hopefully with some improvements. For those whom loved this sound and its capabilities I hope I can fill your needs. For others, perhaps in time. If not, this is a big world and to each his own. I guess I view buying a set of speakers much like finding a wife. Finding a good match is never easy, but always worth the effort.

That is why we all share our love of this hobby and persue being audiophiles. The love of music.

As always, good listening.
Dale

Wow! You guys have been busy, LOL. I go away with the flu for about 5 days and the post has gone crazy. Heheheh.

Anyway, barely feeling alive, but will chime in..

Answers to some of the questions previously asked...Regarding my versions and rebuilds...

Freq response is down to 30 Hz, actually lower, but conservatively rated. Free air is at 25 Hz.
High end is extended to above 20KHz.
Nominal impedance is 6 ohms.
VC's will handle 150 watts RMS at 300 Deg. C.

I do not recommend them for levels sustained above 96 db with HEAVY base passages, without heavy base they will do 98 to 100 easily. This is at 12 feet from the speakers! I find them to be plenty loud. This level I attain using less than 10 watts. These speakers have an Xmax of about 10 to 12 mm. Exceeding this will damge them as with any driver blown beyond its limits.

The original drivers were not truly designed as underhung motor assemblies and some were pre-loaded. The weight of the cone and the sloppy spider caused the VC to hang out of the magnetic gap and seriously reduced the efficiency of the speaker and its capabilities. Proper underhung design and a few tricks to deal with the weight have changed this problem and now the speakers get quite loud with minimal inputs. They do sound best however when driven with amps capable of considerable dynamic headroom.

I would recommend a room of at least 300 sq. ft. for the TLS-I and 500 sq. ft. or more for the TLS-II.

I do not recommend less than 100 watts per channel TUBE or 300 watts SS for the TLS-I and much more for the TLS-II. (Or the F's or the A's) They do not need it to voice or even sound good, but the dynamic head room works wonders. They just open up.

The best room placements I have found seems to be about 8 feet from center to center of the cones and at least 3.5 feet away from the rear wall and 3 feet from the corners. Corner bass traps and rear wall reflection control works well. Placing a flat screen TV on the wall or between them may cause some issues, or degrade sound.

The soundstage depth can be controlled somewhat by the closeness to the rear wall.

BTW, John Strohbeen is not the original designer of the A's or the F's. Lincoln Walsh discovered the concept and the founder of Ohm Acoustics, Marty Gerstin designed the A's with Walsh's help. The firt "A" was released in 1971 just after Lincoln Walsh passed away. Sadly, He never got to see or hear his creation. Marty Gerstin, then went on further refine the A's and to develope the "F", relesed in 1972, as a little brother to the "A". Again, further refining the concepts gained from the originals. The "F" was smaller and easier to drive, but did not have the full sonic merits of the "A's" which had and have no comparrison.

Though the cones were 3 times as heavy and they were very power hungry, they could produce bass that would involuntarily relieve a person as well as cause some damages to home objects. Yet they had a very delicate and nuanced high end. The later coment was not necessisarilly documented by Ohm, but was experienced by others and myself in the early years.

Marty is also responsible for designing the unsual and special voice coils that made the "A" and "F" possible. This concept was pattented as well.

John Stohbeen, the former owner of Tech Hi-Fi aquired Ohm Acoustics from Marty between 76 and 78. Through some of Johns efforts, the "F" was redesigned and or went through changes, until it was retired in 84. John then came up with and patented the idea now embodying the current Ohm products.

The most unfortunate problem now plaguing most people is that there have not been any of these speakers remaing in pristine condition or properly rebuilt from which to compare current product or the originals. The others whom have actually heard the originals are relying on fading memories, as these are 30 to 35 years ago.

Even I can't remeber those experiences, except to say that the original "A" and "F" set me on this path and BLEW me away forever.

Refurbished and upgraded F's start at $6K, ...A's at $13.5K
New TLS-I @ $8K.....New TLS-II @ 15K

Good listening to all,
Dale.

Thanks for the compliments and encouragement. I truly appreciate it. I extend an open invitation to anyone whom wishes to make the journey to my shop and home for demo's and tours.

Regarding the last comment on the castors... I have found that the single greatest improvement that I could render to these speakers (night and day improvement) was redesigning the base and adding the very high quality metal cones. Coupling these to the floor cleaned up the entire sound accross the board. Perhaps you can try it with the other products.

Parts Express sellls some very good quality cones from Dayton Audio and very attractive as well. These will keep you in budget. I would recomend the heaviest cones that run about $20 for a set of 4. Believe me, it is the best $50 you will ever invest.

For those whom may be interested, I presently use:
Conrad Johnson preamps, mono block tube amps, Jolida JD 100A CD transport, A Luxman turntable with Premier MMT fiber arm and varous styli. I employ dedicated 30 amp lines with their own power conditioner and ground system, silver interconnects of my own design and various speaker cables, such as 4TC, 8TC and siver, some of my design too.

I have aslo successfully employed some of Carvers magnetic field amps in place of SS amps to power my creations.

Great listening.
Dale.
dale@hhr-lasers.com

Gentlemen,
I have read your discussions on the Ohm Walsh A and F drivers with enthusiasm. Didn't think anyone still cared.
I am new to this site.
Anyway, for what it is worth, and to my knowledge, I believe I am the only person in the world that builds F's and A's from scratch to this day. I have studied these drivers and their principals for the last 30 years. I am the only person that hand winds voice coils, makes complete cabinets, magnet assemblies and complete cones from new materials. I use the same materials as the originals and some improvements. My drivers are meticulously assembled in every detail. In addition, I refurbish old units as well. I have spoken with many people over the years whom claimed to be able to re-cone or repair these marvels, but NO ONE has ever done so as the original. My name is Dale Harder. I can be reached at dale@hhr-lasers.com