History on ohm A's and F's.

The Peter Dicks driver parts ways with the Ohm driver in several ways. First of all, it was modeled more accurately. While Walsh was a genius (and so was DaVinci), he was unable to accurately model the concept in a way that would make it reliable. Dicks was able to do that.

Dale Harder of HHR Exotic Speakers has been refurbishing Ohm A's & F's for quite some time now. He completely replaces the cone surrounds, new cone material with a lighter mass, and voicecoils using newer materials and technology. He now makes his own versions(TLS I & II) of the Walsh drive speakers and claims that he has solved the power handling and voicecoil issues of the past with a new driver that is more efficient and durable. Here is a list of the improvements(.pdf) he's made on the original designs with his new speakers. TLS I & TLS II specs(.pdf). Here are pictures from his website of how he makes the new speakers.

Dale seems to have more hands-on experience and knowledge of the Walsh designs than just about anyone out there. I'll send him and email and get him to join this discussion.

Hello Darkmoebius, all...

Thank you for inviting me back to the discussion . I am a little disappointed that I was basically ignored on my last posting of the 23rd, so I just stayed out of it.

Furthermore, It upsets me that some people just refer to me basically as the “repair guy”, when I produce a brand new and fully viable line of Walsh “style” drivers known as the TLS series. www.hhr-exoticspeakers.com

True, I have remained closely akin to the original designs, but where else can you find a true single driver capable of covering the audio range without crossovers, ports, and supplemental drivers of any kind.

Note: I also have full carbon fiber cones and high energy Nd magnets system on the drafting board, but they are a ways off yet.

Anyway, my frivolous comments are as follows…Bending wave schmendig wave…piston schmiston…it’s just a matter of semantics at best. So what if the GP vc is elastomerically connected or mine is hard fixed. I can do that with silicone. Bottom line, the vc still controls the movement of the cone and the cone is launched forward in a bending wave fashion or a pistonic fashion depending upon the wavelength. Additionally, the mass of the vc controls the upper end and transient response. GP still uses an Aluminum edge wound vc same as mine. And both drivers are made of Titanium foils exactly the same size. T/S parameters still apply as well.

I agree with Mapman, The old design “F” and “A” or my new design TLS remain full bandwidth drivers while GP avoids the issue of drivers being destroyed by overdriving them by utilizing a separate bass driver and crossover system with a Helmholtz resonator and an MDF box. The bass on my drivers simply blows away the GP series in all but the best of their line. (this is not my sole opinion, but as supported and reported to me from other listeners)

I applaud DDD and all they have accomplished, but the True full range Walsh “style” speaker is FAR from dead.

Can you overdrive and crush my drivers like a bear can…Yes, you can. Can you overdrive and short out the best electrostats? Yes, you can? Can you overdrive the best ribbons of the day such as Apogee or Analysis? Yes, you can. Finally, can you launch a 15” or 18” piston driver across the room? Yes, you can. Just short out the amp or drop your needle on your record and see what happens.

As far as ear deafening sound, 98db in a small 300 sq ft room is quite loud, with peaks going far above that. What more can you ask of a single 12” driver or an 18” driver. At a price point of $8.5K or 16.5K vs. A Wilson Alexandria with 6 drivers, some of which are 13” and 15” and at more than 6 ft. tall. Or, the MBL Extremes requiring a huge room and sub station to drive them at a price point of $200K. They are all still multiple driver systems with huge crossover networks and they SHOULD play louder than a single 12” driver. I don’t know about you, but I would rather have the resolution and engaging sound rather than ear destroying volume levels especially in a smnall room.

One of my clients, proceeded to utterly destroy a brand new set of TLS-I’s with no less than a 600 sq. ft. room and a pair of 1KW amps… Geee…go figure and they were amazed when I refused to cover this on warranty.

This unfortunate event has led me to “choke” design a new series of Walsh “style” subs with 15” and 18” drivers crossing a roughly 50 Hz utilizing active crossovers. So it will relieve some of the stress placed on the full range drivers and volume levels will soar. But, am I happy with using a crossover or compromising the time and phase coherency of the original drivers… NO! I am not. Still this is quite a feat and requires an extreme amount of engineering.

No, these are not available yet…soon, but they are not cheap and they are not small.

Also, I would like to mention that my drivers incorporate subsonic filters that roll of quickly to help protect the low end excursions. Still, no loss of performance here.

Here again Ladies and Gentlemen, it is all about what you can afford to spend, your actual rooms sizes, system and WAF. I do not want to get into any kind of a “pissing contest” nor would I ever belittle any one else and their experiences. I think we are all very fortunate to live in an age when so much is possible and so much has been accomplished technologically. It is all about one thing, Enjoying music, and this love has brought us all together. How much better can it get!

Sorry for my ramblings, if I failed to answer any questions, please ask me here directly. If I know the answer I will gladly post it, if not, I will give it my best to look for it.

Good listening to all, Dale

Dale,

98db in a 300 sq ft room from a single full range driver sounds pretty appealing to me!

This is as good or better than the original As and Fs, right?

Considerably better.
My measurements were made in the far field at 10 to 12 feet from the pair. 95db to 98db was routine.

These volumes were with less than 10 watts average on my system. Though I can not accurately measure the peak demands.

I use Antique Sound Labs DT-200 Hurricane mono blocks that have been highly modified. IMHO, these tube amps are pretty dynamic and have lots of head room. The Walsh drivers sound very open and articulate on these. I find that tubes are a good compliment for speakers. More so than anything but the best SS amps.

BTW,for those who don't know, I forgot to mention that I am also a rep for Piere Sperry's Mapleshade products. Mapleshade is a great producer of fantastic CD's and a wide selection of some very fine accessories including plinths, wood bases, equipment racks and ribbon cables. Pierre also gives away an enormous amount of FREE set-up and tweak info. www.mapleshaderecords.com

Dale

I don't know how many Ohm A's and F's were sold, but due to the power requirements and various other reasons, I doubt they were exactly ubiquitous. Let us remember that the OHM Walsh A's and F's are now over 35 and 25 years old respectivley. Furthermore, due to their unique design, I would think it would be fair to reason that some may have compromised by less than qualified repair efforts. I seem to recall that both Dale Harder and Bill Legall of Miller Sound have made claims that they have solved some of the issues re: the OHM A's and F's, including the alleged reliability issues. I'd imagine that many speakers of that era might need some maintenance. According to the Ohm web site, it was not failure rate that made them abandon the true Walsh drivers, but rather an inability to replace the skilled labor force that had been lost. The original titanium DDD driver was reputed to be somewhat delicate as well.
I will admit that I am not the least bit qualified to make an accurate assessment, but it appears to me that the new OHM's appear to me to be much more similar to a pistonic dynamic driver than to a true Walsh driver. Perhaps, it's just me, but I find Ohms web sites use of audio buzz words to be confusing if not indeed misleading.
I don't mean to condemn the German Physiks offerings. That the lower frequencies, that most consider to be percieved as omni-directional in nature anyway are passed on to another driver may appear to be less elgant, but doesn't perturb me. The newer carbon fiber drivers appear to be a very good evolution. If I could personally justify the expense of these designs, they would certainly be at the top of my short list.
I can't help but wonder if either or both German Physiks or Dale Harder could manage to use a sub that maintains time and phase coherence in the same way that some manufacturers of more traditional cone and dome speakers have, with their Walsh inspired concepts. Or better yet, develop a larger perhaps differently tappered Walsh like driver to be truely full range? And while your at it (Ha!) let's not forget the dynamic contrasts that allow for appropriate loudness are an integral part of music, for both headbangers and "serious" music afficandos.
I sincerely encourage those who choose to pursue the development of these types of speakers, and I would like to to especially encourage the development of ones that could be afforded by the masses. Good luck!

Dale,

I would absolutely love to hear a set of your speakers. I think that the promise of the Walsh concept has not yet been 100% fulfilled, but I remain a big fan of the concept (which is why I became the importer for German Physiks).

Where are you located?

Hello Unsound...
Please go back and read my responses of earlier today especially regarding the sub. This would be my first post on the 27th.

Regarding the Ohm numbers, sources have said that about 10,000 F's were made and around 60 A's. I do not have this on full authority, however.

Ohm basically stopped making the units because of the warranty policy they maintained. It was no problem, "no questions asked". "Blow 'em up and well repalce 'em". So many people just got very rambunctious and kept on turning them up until they blew up. Hey why not?! Ohm will replace them. They could easily have trained other people to make them, but it was easier and more cost effective to just let them disappear.

Not to mention they are exceedingly hard to manufacture, just like the DDD's are.

You are indeed correct. Ohm's use of the Walsh buzzwords are somewhat ambiguous, but there is some Walsh concept in their new products.

Csommovigo...Thank you..
You are invited at anytime to come and see, feel, touch, hear and enjoy.
I am 5 min from Cleveland Hopkins Airport in Parma Ohio.
This invitation is open to anyone. Just give a call and I will gladly set up a time for you.

I also agree, the Walsh concept has much more developement left in it.

Dale

Hi Dale,

Thanks for the invite. I'd like to come for a visit after the frost! ;-)

Chris

Dale, thanks for your reply. I read your earlier posts. What am I missing?

My design and implementation of a true Walsh sub...

"I can't help but wonder if either or both German Physiks or Dale Harder could manage to use a sub that maintains time and phase coherence in the same way that some manufacturers of more traditional cone and dome speakers have, with their Walsh inspired concepts."

Not that I really want one, but I find the need for some people who just can't keep their hands off the volume control.

As well as carbon fiber cones and Nd mag structures.

all to come, but it will take some time and money.

My design and implementation of a true Walsh sub...

Now, that's breaking new ground on this old design. Can't wait to hear more about it.

Dale, perhaps you could give us some technical insight into the perceived weakness/problems of the original Walsh drivers and how you have corrected or improved them. Especially, regarding output level and efficiency.

Darkmoebius, there is more info here.

http://forum.audiogon.com/cgi-bin/fr.pl?cspkr&1194658277

Hi Darkmoebius,

If you will go to the wesite www.hhr-exoticspeakers.com and look at the bottom of the "Products" page you will see a picture of the new TLS-I. Just above this picture is a hot link that will take you to a new page that fully expalins all the upgrades and design changes I have implemented on both the remanufactured units and the new TLS-I and II series.

I have done my best to address the issues that have been sent to me throughout the years from Ohm product users and I continue to work on new upgrades and designs daily. There is no rest for the wicked you know.

Dale

As a huge OHM F fan/owner I really enjoy the Q"s an A"s on this forum. I"m not sure who rebuilt my pair of F"s, but my eyes/ears tell me they were done correctly. The sound is just awesome in my 20x13x7 (audio room) which opens to a wet bar and half bath through a 7ft opening. My pair of F"s have a top end with plenty of detail/shimmer that is neither hot nor too recessed, leading into that glorious mid range. Female vocals are in room, singing to me. Bottom end has a natural foundation with good attack, enough thump as to not need a subwoofer.

I agree, OHM F"s are NOT for headbangers who think they need 110db to enjoy music. My pair sounds quite nice around 90-95db, from a Belles 55 preamp (subsonic filter engaged) to a VSP gold power amp (totally recapped) thanks again (audionut66@comcast.net) beautiful job!

In closing ... if your OHM F"s don"t sound correct, then they were repaired incorrectly. My all-time Favorite!

Just a question from a naive reader: wouldn't the transition from a wave-bending mode to a pistonic mode in a single driver result in an audible "crossover" effect, although perhaps much less audible than a well-managed crossover between two separate drivers?

Lewis,

There is a transition from wave bending at higher frequencies to pistonic at lower, I believe.

Not sure I'd call it a "crossover" necessarily. Not sure to what extent that transition is audible or discernible to the human ear. Maybe others might know more?

The F driver had three separate sections covering different frequencies with different materials comprising each section. I believe I've heard reference to the 2 cut-over points between sections referred to as the physical equivalent of an electronic crossover, similar function, totally different technology/approach.

Also it is not clear to me the exact specifications in regards to at what frequencies and to what extent at each the driver operates pistonically versus bending wave.

I think it would be accurate to say that the modern Walsh drivers used by OHM operate more in the pistonic mode than wave bending in that wave bending is associated with higher frequencies I believe and the modern OHM CLS Walsh drivers use a supplementary tweeter. German Physics DDD drivers on the other hand operate at the high end of the frequency spectrum supplemented for the most part by conventional woofers, I believe, which is an opposite approach.

Getting a single Walsh driver to do it all or as much as possible without destroying itself at high SPLs would seem to be the name of the game in general.

Lewis,

Without presuming too much technical knowledge of my own, I suspect that the opposite happens. Since the dispersion pattern of the Ohms is always (nearly) omnidirectional, there is a sense of "continuousness" to the speakers. Whatever discontinuity that might be a result of your observation seems to be subsumed by this effect. At least to my ear.

Also, I would guess that the transition may be gradual, with some frequencies being partially reproduced by both bending and pistonic motion. Such an arrangement would be akin to very low order (presumably well less than first order) crossover. Such schemes usually mask transitional issues, although they can certainly introduce other artifacts. By the time response is primarily pistonic, you may well be at a frequency low enough that most listener's sensitivity is reduced. Similarly, BTW, the cross to the tweeter is so high in frequency that -IME- most listeners will be relatively insensitive to that hand-off.

Maybe John S can comment further.

YEs, I'd really love to understand the pistonic/wave bending thing in more detail in regards to the CLS Walsh driver.

OHM CLS must be doing some wave bending in the mid range and up, though clearly not at the very top end where the super tweet works. The cls high end response extends beyond 16-17Khz which I think is approximately where the F ended.

I'm assuming wave bending is at least part of what propagates sound outward horizontally from the rear of the downward firing cone as opposed to up/down (pistonic) using the cabinet to tune the low end, but I do not know for sure, just how smooth, dynamic and "coherent" the resulting sound is, particularly in the mid-range. The very generalized diagrams I've seen on the OHM site showing how the CLS driver works seem to indicate this.

I sent an email to Dale Harder who rebuilds classic Ohms and now manufacturers brand new A & F equivalents(HHR Exotic Speakers) with a number of modern improvements. He may be one of the only people who can properly answer that question.

Hopefully, he'll be able to chime in with some good info

Dale did chirp in on this thread earlier regarding his designs and German Physiks specifically and his comments are worth repeating here.

Though their Walsh driver designs all vary, I suspect what he says regarding how each are similarly voice coil driven regardless of resulting pistonic or bending wave propogation of sound applies to the OHM CLS as well, but this is just my assumption based on what appears to be similar physics and design elements in play in the case of each.

Dale said:

"Bending wave schmendig wave…piston schmiston…it’s just a matter of semantics at best. So what if the GP vc is elastomerically connected or mine is hard fixed. I can do that with silicone. Bottom line, the vc still controls the movement of the cone and the cone is launched forward in a bending wave fashion or a pistonic fashion depending upon the wavelength. Additionally, the mass of the vc controls the upper end and transient response. GP still uses an Aluminum edge wound vc same as mine. And both drivers are made of Titanium foils exactly the same size. T/S parameters still apply as well."

IMHO, each vendors Walsh design varies based on targeted market.

GP targets the very high end audio market.

Dale Harder is a champion of the concepts of Lincoln Walsh's driver and is a champion of carrying the original OHM designs into the future with a focus on quality and value.

OHM has always and continues to focus on providing the best sound possible as cost effectively as possible to the masses.

Hello Darkmoebius, thanks for the invite to add my two cents.

Sorry this has taken so long. After a few email and many days...

While this is "some-what of a complicated subject", I don’t believe there is a Direct answer, but rather a conglomeration of processes taking place that influences the final outcome. So, in a rather lengthy fashion, bear with me as we try to pick this apart.

I would say that a standard crossover being either passive or active in nature is obviously more of an electrical device acting directly upon the input signal rather than a mechanical device, though to be fair it can also impart a mechanical signature as well.

That being said, the electronic crossover by nature, IMO, tends to directly interact with the incoming signal and adds or subtracts its influence over a broad range of frequencies, and *in most cases these can be herd* as a distinct change in the original signal. The original frequencies may also be altered by adding odd order harmonics and distortion components and are then passed along down the chain.

In the case of the Walsh driver or the DDD driver the electrical input signal has no crossover elements to deal with and therefore remains as true as possible to the original signal. Obviously the voice coil has some losses, however the resistive losses and the conversion losses to a mechanical movement *if implemented correctly* will not alter the signal characteristics, but simply tend to produce a replica of the original albeit somewhat smaller, i.e. less amplitude. There are other factors as well, but we shall ignore those for the sake of brevity.

Now the rub,…the Walsh and the DDD drivers actually have up to 4 separate modes of behavior all happening at one time.

The lowest frequency range of its operation can be described and predicted by the use of the Thiele/Small Parameters. (This is useful in designing the proper cabinetry to mount the drivers)

The next frequency range takes place up to the Coincidence frequency. (The Coincidence Frequency is best described as the frequency at which the velocity of the wave traveling through the cone reaches that of sound in air, or approximately 1120 ft / second.) It is this band where the cone tends to move mostly in the pistonic rage.

The next range is where Pistonic movement is progressively replaced by Bending Waves. Eventually the range progresses to where the cone is functioning entirely as a bending wave converter.

Remember, all of these ranges are overlapping in nature and do not have a very defined band or point that is distinct by nature or equivalent to just a couple frequencies. It is due to this dispersion and the shape of the cone that the Coincidence frequency range is distributed over a broad frequency range rather than occurring at a single frequency.

Let me interject for a moment regarding the Walsh driver and the three distinct metal, paper bands. A common misconception is that the low, med and high frequencies all “boil” off the cone only on the related areas, i.e., the high from the Titanium, the mids from the Aluminum and the lows from the paper. This is actually not the case. The actuality of fact is that the wavelength determines where the wave will exit the cone and it also determines which of the four modes mentioned above the waves are functioning in. The segmented metal/paper cone sections were really derived to offer a substantial change in material density and stiffness, which in turn controls the speed with which the traveling wave moves through the material. It was also an attempt to control modal patterning.

Finally, moving beyond the Bending mode of operation we come to the range where the first standing waves begin, and this is to be avoided if possible as this is where modal breakup and loss of cone control begins.

OK, now that I have expressed that entire load, you can see that there are an extreme number of factors taking place in this type of driver.

Now, in the course of testing a driver such as these, we may feed in signals consisting of sine waves and or square waves (hahaha, just try that with a piston driver) and try to get an idea of the frequency response of the driver or of the overall system consisting usually of multiple drivers. The real rub here is that music is a complex signal consisting of many waveforms and harmonics and is anything but a sine wave.

Now, consider this, the many hundreds of waveforms being generated that may make up a single instrument or note are actually boiling off the cone at different places all at the same relative time. Since they are not all exiting the cone surface at the same place and since theoretically they have not been altered in any fashion it would be extremely hard to *“hear”* a crossover point or region. (BTW, the waves reach speeds of up to 5 times the speed of sound traveling through the cone)

And so it is, when we look at a frequency response curve of a Walsh or DDD driver we see for the most part a continuous curve. When we look at a multiple driver system however, we see many curves all interrelated with their crossover points and the regions these respective drivers cover on either side of these crossover points.

When I do a test of a Walsh driver using a sine wave generator and slowly look at the waveforms from 20 Hz to 20 KHz there are usually no points in the curve that correspond to say the actual crossing of the paper or metal boundaries. Most of the nonlinearities occur from actual cone construction techniques and these are usually minimal if done correctly. In fact, this is a great way for me to find defects and correct them or to hand tune the cone for best linearity. Now if a cone is made of one single material then there are no physical material changes to act as varying points of density or stiffness, but other methods must be employed to accomplish the same end result.

Hmmm, come to think of it, the Walsh style driver does not suffer from Doppler induced distortions either.

It has been said that it is possible to hear the crossover point or region on the DDD system because it uses an augmented low end with a standard piston style driver and external crossover. This I can well imagine, but in all fairness I have not heard it for myself.

Here is some further food for thought. The very highly acclaimed and very expensive (50K+ and 200K) MBL 101E and the 101 Extremes are one of the few drivers utilizing true coherent 360 degree sound much as the Walsh and DDD. However, these systems utilize FOUR separate drivers with four crossovers. In addition, the drivers are either stacked or separate as in the case of the subs for the Extremes. Now imagine the crossover influence that must be present there vs. a single driver with no crossovers, not even mechanical.

So the long and short of it gentlemen is that I have yet to hear or perceive a crossover induced distortion on a True Walsh Driver.

PART II Back to the original question....

"wouldn't the transition from a wave-bending mode to a pistonic mode in a single driver result in an audible "crossover" effect, although perhaps much less audible than a well-managed crossover between two separate drivers?"/_ -- could you explain if there actually should be a *theoretical* crossover effect at the transition point vs your first-hand inability to hear one.

After talking with DM on a personal e-mail he prompted me to add the following...

In order to better answer the original question....

What I believe is happening is that folks are "getting hung-up on the idea that there are actually transitions in the modes of operation." Here again, remember we are not dealing with sine waves but rather complex waves and harmonics at any one give time.

While one part of a wave may be indeed transitioning a boundary layer per say, I rater doubt that all of the waves are at one moment. Further, just because the wave is transitioning from say a bending wave motion to a pistoic motion, does not mean that its waveform or sound is changing. The wave is still boiling off the surface of the driver cone in the same fashion and exiting the cone at some finite angle relative to the wavelength. It is still leaving the cone and producing a wave pattern similar to the stone making waves in a pond. The wave is not dependent upon the driver moving air forward or back as in a piston cone of say a regular 12" cone.

It is these ripples that are coming from the piston driver moving air in a forward or rearward wavefront that are affected by Doppler shift and beaming. The Walsh style cone does not suffer from either of these characteristics.

So, IMHO, I do not believe that you would be able to hear any crossover shift under normal circumstances.

I hope this helps to shed some light on the subject gentlemen.

Good listening to all.
Dale

Dale, thanks so much for your (one of the most I have seen) detailed accounting of how the Walsh driver works.

I've always considered the Walsh driver a truly a unique and vastly under-appreciated piece of engineering work IMHO despite my limited understanding of the physics and engineering behind it.

I'm glad there are people like you, Strohbeen and the others out there devoted to keeping it alive and moving forward to the benefit of music lovers everywhere!

07-22-09: Mapman
Dale, thanks so much for your (one of the most I have seen) detailed accounting of how the Walsh driver works.

I've always considered the Walsh driver a truly a unique and vastly under-appreciated piece of engineering work IMHO despite my limited understanding of the physics and engineering behind it.

I'm glad there are people like you, Strohbeen and the others out there devoted to keeping it alive and moving forward to the benefit of music lovers everywhere!

Dittos

Dale,
I have enjoyed following your progress over the last couple of years with your walsh refinements. First, do you have any working versions of the "A" type? I only see finished F's on your site. Also, I have to disagree with you concerning doppler effect. You mentioned earlier that there are several modes in operation simultaneously with this kind of driver. I have noted that the pistonic action causes the entire driver to move at lower frequencies which may cause the other frequencies to be affected. When I had my F's and they were driven reasonably loud I noticed this, first with a playback of reggae music. (BMW live disc). When "family man" hit those low notes, the whole driver would shake and cause Bob Marley to sound like he was gargling. No, the amps (2 bridged Dyna ST-400's) were not anywhere near clipping (less than 100W peak transients) when I noted this effect. If this is not doppler effect, then I would like to understand what it is. Best Regards.

Hello Spikedart,

Yes, we do have some re-manufactured A's and the new TLS-II series as well. The A set is available for $13.5K and the new TLS-II's are by order only starting at $16.5K

Unfortunately, I do not have a lot of time right now, but I suspect that the sloppy movement you may have encountered was due to the very soft almost silken spiders and poor support the original F's suffered from rather profusely.

It surprises me sometimes just how the old units played, since most of the time they were hanging half way out of the magnetic gap and flopped around like a flag in the breeze.

Our new units are not like that at all. Still they retain +/- 1/2 inch of X-Max travel when needed.

At some point I will address the movement of a piston driver both compressing and rarefying air in its movement and producing a positive or negative wave front at far less than the speed of sound. In comparison, the Walsh style driver is around 5.5 times the speed of sound

Until the next time...
Good listening to all.
Dale

Spiked,

IIRC, the doppler effect is the pitch shift that results when a sound source moves toward (or away) from you (at relatively low speed). A train whistle is the usual example. If a speaker's driver produced this problem, I'd think that you would get a slight "quiver" around a vocalist's pitch. Given the short distance (and oscillating path) that a driver travels, it would be barely audible at worst.

I wonder why you are ascribing the "gargling" vocal problem you heard specifically to this? There are surely other possible wayward behaviors that would cause what you heard - a flaw in the surround comes to mind. I'm not sure that this is ever audible in loudspeakers, even if the drivers are pointed at you and "qualify" for doppler shift. However, since the Walsh driver moves vertically, it would seem even less applicable. The horizontal "travel" on a Walsh driver is virtually nil. What's your thinking on this one?

Marty

Sure sounds like IM distortion to me!

Yes, However I believe that the IM distortion is the end result which is preceded by doppler frequency shifts of midrange audio frequencies produced by the cone that is also producing low audio frequencies. Wonder how this is mitigated in Mr. Harder's updated designs? I noted this issue with both older F's and in a brand spankin' new pair straight outta Taffe Place. I have wondered if insufficient wave termination might also add to this effect. The newer F style versions appear to have the same surface pattern and termination materials as the original (an assumption). I wonder if other patterns have been used or if there is a way to calculate them. Anyone applied Bud Purvines's enABL process? Does this work?

Spike,

Which Marley live recording?

Were the Fs possibly being over-driven? It was not hard to do this with Fs from what I have heard.

If the source was vinyl in particular, was it possible that low frequency noise (rumble, etc.) was present? That might contribute significantly to a problem as you describe if so.

Hi Mapman,
It is the Babylon by Bus album, specifically remembering "Punky Reggae Party" as the worst offender, which I had recorded to maxell XLII tape with an Akai glass head tape deck using DBX NR. Shouldn't have been any appreciable rumble since it went straight from Technics SL series TT, w/ Ortofon Concorde cartridge through an Apt-Holman preamp with subsonic filter on, into the deck. I had a pair of Dynaco ST-400 bridged amps driving the F's, so probably (definitely) no clipping. I am sure the soft spider contributed to the excessive cone movements, but when the bass notes hit, you could see those cones really dance, and that's when the distortion set in.

Spike,

My educated guess is that the Fs were starting to be overdriven at that point, which as I understand it was common and easy to do with the Fs, and their acknowledged achilles heel that Strohbeen tackled by switching to the CLS design with Walsh driver not as wide range as the F Walsh driver.

I may still have a similar cassette recording of Babylon sitting around. I'll have to give it a play on the latest and greatest Walshes from OHM and see if I hear anything. I have not noticed the sonic artifact you describe on any CLS OHMs I have owned, however.

Spike,

Is it also possible that the cassette recording was audibly distorted, oversaturated or something along those lines?

In general, cassettes were never a great medium for capturing low distortion recordings with good dynamics.

OR maybe a combo of cassette recording distortions combined with OHM F overdrive?

Mapman,
the F's were definitely being overdriven at times. I often played them as loud as I dared with bass-rich material and had considerably more power on tap than they could safely handle. I would watch the cones achieving very large excursions; probably exceeding the limits of the surrounds. I am sure that this also contributed to the distortions I heard. If you have listened to a pair of these being played then you are also familiar with the visual performance they can provide. The actual source material is largely irrelevant; the BMW recording is simply the one I remember most clearly. If there was music combining loud, low bass notes with midrange such as voice or saxophone, this issue could appear. I myself have 4 pairs of the later Ohm walsh speakers and have not noted this phenomenon with any of them, even at high volumes.

Hello All,

For your enjoyment, I have posted my 2 channel system in the "Virtual Systems" under "Ever Evolving" titled "My Walsh Dream". Though my site has been viewed well over 400 times in the last week, (reset once by AG, with a system glitch), no one has left a single comment. Please take a moment to check it out and leave your constructive input.

I am working as hard as I can for the benafit of all Audiophiles everywhere to maintain the highest level of sound quality, system integrity and value driven products as I possibly can, especially in this dreaded econmic downturn.

As always, good listening to all.

Dale