This is a synopsis and some do's-and-don'ts regarding these  amazing loudspeakers. I will try to limit my comments and just hit the highlights since there is so much depth in the subject of these speakers. For a much more in-depth discussion of the construction and properties of these speakers I suggest you read Dale Harder's eBay Guide titled "Ohm Walsh F". And if you're really serious, you can read a copy of Walsh's original patent [No. 3,424,873] from the USPTO archives.

Theory: The Walsh speaker, actually introduced in 1973 / 74 (I sold the first pair to be sold locally to an architect in SF back then)  is based on transmission line theory. Briefly the concept is that the acoustic wave generated by the driver, travels down the tapered cone and terminates in the resonant cavity (bottom enclosure) with no reflections running back up the cone which would cause standing waves, intermodulation distortion [IM] and cancellations, seriously degrading performance. Note that the speaker is faced down toward the floor, with the driver sitting on top at the narrowest part of the cone and the wide end of the cone is at the bottom coupled to the sealed enclosure. The radiating surface is then the backside of the cone when compared to a 'standard' speaker and thus radiates an omnidirectional wavefront [i.e. 360 deg] out into the room. That was a unique design concept and was patented by Lincoln Walsh and is major factor in the incredible aural imaging qualities these speakers have. It is a real shame he did not live to see it become reality. Further unique characteristics are, these were the first and only speaker of the day to be  (a) phase coherent and (b) without passive or active crossovers, the crossover was in the construction of the cone itself. Later KEF and other manufacturers, like those utilizing air-motion-transformers and 3-way systems with the speakers in separate  enclosures and staggered on the depth axis to imitate "time alignment" in an attempt to achieve the same effect. Flat panel electostatic technology, like KLH Model 9, actually did achieve good time alignment but suffer from narrow spacial imaging, they also tended to be very bright and harsh. They were basically huge capacitors. The Walsh was the one true phase coherent speaker and was achieved by a simple and ingenious technique: The slope angle, or taper, of the cone was calculated such that the wave traveling down the cone face was in phase with the acoustic wave emanating out into the room, thus achieving phase coherence. In other words the resulting wavefront [radiating into the room] was in coincidence across the spectrum. That brings us to the crossovers, or actually, lack thereof. There are 3 sections in the vertical cone, arrived at after long and laborious testing. The high frequency material is a titanium alloy (which contributed to their high cost, and ultimately their being pulled off the market as being too costly and labor intensive to produce), the second is tempered aluminum [not stainless, as I previously stated]  for the midrange and the 3rd is heavy paper cone material for low end. The high frequencies radiate outward at the top, titanium (smaller diameter) end, the midrange from the aluminum section, and the bass at the lower paper part of the cone. This speaker was hailed as having the smoothest frequency response of any speaker (+/- 4dB down to 20Hz) in that era.  By the way, prior to Ohm Acoustic launching the Model F, they  launched the humongous Model A, which I have never seen or heard [but would love to] other than in print. The responder who mentioned the point about how power hungry the F's are is correct. It should also be pointed out that an amp with very high damping factor is also a big plus, in that the speaker mass on loud low end passages needs heavy dampening to keep it from "ringing" and will result in making that beautiful musical bottom end really come alive, not just a whump, so common in today's systems.

Cautions: One important point, be very careful in choosing an amp for these speakers - they hate DC (e.g. driving the amp into flatline distortion or DC generated during power on/off). Any direct coupled output amp can easily destroy these drivers, they seem to be hyper-sensitive to DC.  I have been driving mine since 1977 with 2 MC 275's tube amps, each strapped for mono. With the transformer coupling on the outputs of the MC's, I have never blown a driver, even though I have driven the amps into distortion many times. Other people I know with Direct Coupled amps have blown the drivers and I believe you cannot get replacements anymore.  [I wonder how many F's are still out there making music?]. The foregoing might be a little contradictory. Using a transformer coupled output as I do, while it does protect the speakers, they do not have a very high dampening factor as the transformers prohibit it. Generally Direct Coupled amps have the highest and best dampening factor but with the risk of driver damage. If you listen at moderate levels, it's not really a concern. And of course there are amps with built-in preventative circuitry to limit or eliminate DC on the output but these are very pricey as far as I know. I ran mine for a time on Yamaha P-2200M studio amps and I could hear noticeable improvement, esp. in the bottom end but I eventually went back to my beloved McIntosh amps.

Repair: I did replace the surrounds a few years ago. I bought a set from a vendor in Audio Mag for $20 and they worked just fine. It's a job that requires a day and a no-hurry mindset but is not technically hard to do. The most important part is the positioning of the new surround on the cone before it's glued AND the positioning lower surround to the speaker frame before it's glued to make sure the alignment of the cone inside the voicecoil is perfect. If it is not done right, piston coil will rub inside the driver and then you'll have real problems. I used masking tape,  after applying it to my jeans to take some of the stickiness out of it, for temporary attachment until the correct position was found. I tested position by gently pushing the cone up into the voice-coil several times to ensure free, easy movement. I rechecked this several times as I  progressed. Once positioned correctly I used contact cement for an adhesive. Let the cement cure overnight and you are done. Take your time in removing all the old glue and gunk too.  Doing good prep is essential and it is the most time consuming part of the job, aside from aligning the cone on reassembly. Feel free to contact me if have further questions/comments.  Btw, surrounds are easily found on the web these days but use care in choosing a set. A high quality, low mass material is the most desirable. If you do replace your surrounds please send me an email with your results.

Placement: Back in the 'good old days' when I had the perfect listening room for these, the ideal set up I found was the following. An ideal room will be about 12 - 15' across the front wall. Place each speaker in the left & right corners but pull them out about 1 foot from each wall diagonally [1 foot to the back and 1 foot to the side] making sure they equidistant from each surface, play with this distance until you find a sweet spot, which will be defendant on the acoustics of the room they are in. At some point, the imaging will come alive and you'll see what all the hooorah is about. Oh yea, one other thing I did but you probably won't want to do, I drilled two 1/2" holes cattycorner in the bottoms of the enclosures and ran a two 1/2" x 6" lag bolts in each speaker down into the hardwood floor - really improved the bass, didn't help the home value so much tho'.... [but they never got stolen either!]

CV: I  have been in the  pro audio/video industry for over 35 years, recording albums, designing, building and maintaining many recording facilities, custom consoles and equipment for some of the best known performers. You can see an article and photos highlighting a device I built for Neil Young called the "Whizzer" for his Deluxe on pages 187 -189 in Tom Wheelers new book "The Soul of Tone - A History of the Fender Guitar Amp"