Reagrding the Ohm Walsh F & A Now Walsh TLS-I, II

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 written 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. My 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 beautiful and unique speakers. Thanks and Good listening, Dale Harder.
Thank you Dale for your very informative post, I enjoyed reading. I have heard various Ohm speakers but never the big model "F" and was always very curious to their sound as in the 70's they were a landmark/legend. I wish I had a pair!
Dear Xiekitchen,
Now you can have a pair of small or large, either rebuilds with upgrades or new TLS-I or II's. Contact me at or 440-888-2163 aft 6 pm. est or most any time otherwise.
Thanks for the kind words,
Dale, it's obvious you put a lot of effort into this. However, breaking it up into appropriate paragraphs would make it easier to read.
Sorry Pryso,
I agree, I actually did have it paragraphed, but when it transferred it changed to this format. I'll see what I can do.
Ladies and Gentlemen,
Many of you have asked, so...
I am happy to announce the birth of our new web site. It has been a long time comming. Please be kind, it is still undergoing some growing pains. LOL.

Good listening to all.
I found your site interesting and informative.

Congrats on the web site!

I'm in process of reading through it.

I've got modded Ohm F cabinets from Ohm with Walsh 5 series 3 drivers that pop on and off.

Could your re-furbished Walsh drivers work well with these without mods? I would love to give them a try!
Thank you both for the kind words.

Mapman, Please give me a call evenings after 5:30 pm est and we can discuss your needs. Use the number on the web site.

Well, I could really use a government bailout, but I guess I will just have to wait in line!

Otherwise, I'll be looking forward to an opportunity to hear your creations someday!

Enjoyed the website thoroughly!
It is wonderful to see a rebirth of the original Walsh speakers; it took a lot of dedication. One of a kind in design and there looking good. I hop the hear them some day, I am about a 90 miles or so from you.
Hello Line...
Thanks for the wonderful compliments.
Please come and visit! It is well worth the effort.
My home is an open show room set up for clients and myself.
Just give me a call.

Good listening,
Hello All,
Looks like we have neglected this thread for some time.

As most of you know, we have been very busy for the last few years with our new Walsh "Style" TLS products and a lot of the progress and coments can be seen on the virtual systems thread.."My Walsh Dream".

In the meantime,... just thought you might enjoy a "few" comments from some of our clients around the holidays of 2010. These and others will be added to our review page on our website.

Hi Dale:
“Happy holidays and new year to you and Yin.
I've actually begun writing my speaker review. The problem is, that I'd rather listen to them than write about them.”
Brad Powell 12/26/10

"Merry Christmas Dale...BTW the new TLS-I speakers are awesome. Just as I remember them."
Bill Gonzo 12/24/10

“I've been the proud owner of a set of TLS-1's for almost 3 months now. To be brief They are simply astounding..... the descriptions can be endless. Silky smooth mids and highs, quick, tight, punchy sometimes startling bass. Dale's passion and knowledge of these"instruments" are unrivaled. He is willing to sit and listen to any questions about these speakers you may have for him. You can either go out and listen to a pair of speakers at his home showroom, or you can contact Dale Harder and purchase them direct. Thanks again Dale,...for everything.”

John S. (Ocean County, N.J.) 12/23/10

“I love my Walsh speakers they are by far, the best that I have ever heard in my life and they are not even broken in yet! I am definitely a satisfied customer.”
Hope all is going well for you!
Tony Pierco 10/21/10

We are always open to you comments and ideas. Thank you for your support.

As always, great listening to all.

Dale Harder
HHR Exotics
Great advertisement.

Saved you $6.

Frugality is an admirable trait.

A few words on sensitivity, max output capability and power handling would be appreciated.

Thanks in advance,

Gee Dale, love what your doing, but that was just plain cheesy.
I'd like to see this thread stirred up with user input on the TLS models based on listening sessions from some of the various OHM/Walsh fans on A'gon somehow.

I think there is a captive market for these here based on expectations. The trick is to deliver some user assessments here that compare these with other more well known and popular designs.

Dale, A'gon should be a great and cost effective resource for building market for these with just a little of the right kind of investment, if that is what you are interested in....

I personally would even be willing to travel a bit perhaps with some advance planning if that would help to get a listen!

Dale, how about exhibiting at teh upcoming Capital Audiofest? I went last year and I think it is perhaps just the right size venue in a good customer target area for you at this stage.

I will do everything I can to be sure to attend again this year if I know there will be new Walsh based speakers to hear there!

Your stuff should be highly price competitive with most of the better stuff I heard there last year! Could be a nice win!
Map, I assume the Capital Audio fest is around the DC area? I would love to hear Dales gear too. I probably wouldn't make it to the Audiofest, but I shouldn't have any excuses, Ohio isn't too far for me to roam and drop in on Dale at some point.

Dale, if you are reading any of this, I am wondering how many of your TLS unit's have been sold at this point. I wish you all the best in your efforts of continuing the manufacture of this type of driver and the technology to do so. Tim
"Map, I assume the Capital Audio fest is around the DC area?"

Yes, in a wonderful 19th century mansion public venue in Rockville, MD just outside DC.
Oh really. That's about 45 minutes from me, not counting typical DC area Summer traffic.

Think I might need to add this to my calendar...
Hello All,
Sorry I have been absent, I seemed to have missed this thread.
I will try to respond to a few questions.

Marty in response to your querries,...

Sensativity is around 88 to 89 db per 1 watt input. Power handling, well that can be somewhat misleading and there is no standard in the industry to my knowledge.

However, the voice coil can easily handle 250 watts and the speakers will handle 300 watt peaks. Sustained power or average power is quite a different thing, however

I routinely run 95 to 98 db sound pressure level in my 300 square foot room measured at 10 to 12 feet from the speakers, using a very high quality Sound Pressure level meter, RTA and various other test instruments.

Free air frequency response is from 24.5 Hz to 22 Khz. I purposely roll the TLS-I off at at about 29 Hz to prevent damage to the driver. Cone excursion (Xmax) can reach 1 inch. (+/_ 12mm)

The impedance curve is almost ruler flat without rise as it aproaches the high end and is ALMOST a pure resistive load on the amp. The sharp impedance peak is at 24.5 Hz typically. This is aided by the fact that there are no crossovers what-so-ever, be it mechanical or electrical.

Sorry if you felt my posting of some of my clinets comments was cheesey. I did not mean to offend anyone. I posted these after several others asked me to post some comments.

Stir Away...LOL. You and anyone else are cordially invited to vist anytime. Bring a friend, bring a spouse, bring your music.

Frazeur,...Regarding your querry of how many sold, some have been private sales that I can not divulge, however the number is around 24 pair.

I was unaware of the other show venue you mentioned. I will look into it.

Great listening to all.
Thanks for your response Dale. Very interesting. I do hope someday to get over to your neck of the woods and have a listen to them! Tim
I had the pleasure of meeting Dale and his wife and listening to these remarkable speakers. First, you are not going to meet a more interesting person. His experiences and accomplishments sound as though they were accumulated over multiple lifetimes and his knowledge of audio is amazing.

His continued work and improvements on an already great design are evident because the TLS-I speakers are perhaps the best speaker I have ever heard. Now I cannot say that I have listened to every speaker and I'm sure others have listened to many more, but I have been fortunate to listen to Magnepan, Thiel, Wilson, Avalon, DeVore Fidelity, Vandersteen, Swan, Joseph Audio, Usher, B&W, Martin Logan, Salk, Aerial and Anthony Gallo Reference. And I'm sure I forgot a few. I have always enjoyed a large, open sound that goes well beyond the dimensions of the speaker. Also, I have always placed a premium on accuracy of the mid and high frequencies because way too many speakers sound incredibly harsh. Let me say these speakers do very little, if anything wrong. I enjoy a wide range of music and my mother has played the piano for over 40 years and I know what I like and dislike. Of all the speakers I have listened to, this is the first speaker that doesn't beam the music at my head or force me to listen in one specific position that drastically changes with every inch I move. When listening to a piano, it sounds incredibly large and dynamic and for the first time, I was listening to speakers that understood that. This was the first time I have listened to a pair of speakers that I thought I could turn down the lights and kickback with a drink and simply enjoy the music without thinking of swithching speakers, amplifiers, cables, ...; well you get the idea.

For those also in this hobby and for those that spend A LOT more for speakers than the TSL-I's do yourself a favor and contact Dale. We all know you can spend a lot more for speakers and will end up with many of the same problems associated with conventional speakers. And yes, I understand the room plays a big role. But these speakers sounded better in his room with minimal room treatments relative to some other very expensive speakers in highly treated rooms I have been in. Worst case scenario, you'll talk to him for hours and come away just impressed as I did.

These speakers had the best aspects of all the other designs I have heard without the beaming, small critical listening area and they present the music in a lifelike manner. I walked between the speakers and it sounded as though I was on the stage with the artist. Walk into the next room and it sounds as though the artist is in the next room. No matter where you were, the sound did not disappear. Articulation, accuracy, soundstage, air; it was all present. These speakers will let you know the integrity of the recording, as most speakers do at this level. And it's a shame how bad many of the recordings have become. But after talking to Dale, I now have a plan on how I can ensure I'm getting the best possible recordings.

Now I am a critical person and realize there are others out there that are much more knowledgeable than I am, but listening to these speakers brought the actual instruments and artists into the room and more importantly, brought back very fond memories of my mother playing the piano. And that is what it's all about. This was the first time a pair of speakers made me forget about the pair of speakers and simply enjoy the music. Now I have known people to switch equipment pretty frequently. And that's fine because they like equipment, technology and change.
But for me, it's the fact the equipment got out of the way and the artist took center stage. I was not fortunate to hear the original Walsh designs and I think it's a shame more manufacturers have abandoned or disregarded this type of speaker. Just because something is difficult it doesn't mean it should be ignored and I applaud Dale for improving a legend. If you can't tell by now, Dale's speakers are amazing and you owe it to yourself to contact him and listen to his designs.

Associated gear
Jolida, Conrad Johnson PV-11, PS Audio

Similar products
Magnepan, Thiel, Salk, Wilson, Swan, Usher, Gallo and a few more I'm sure.