Ohm Speakers, thoughts?

7p62mm thank you very much, yes this helps quite a bit.

Unsound, 7p62mm described the newer "Walsh" series. My only comment to what was stated is that it does not use what is historically known as a "Walsh Driver". Instead, the newer designs use a conventional woofer that is loaded face-first into the top of the box. What you hear coming out of the "can" is the backwave of the driver i.e. the sound leaking out of the holes in the drivers' basket. The front wave of the downward firing woofer is vented from within the box. Since there is limited cone exposed through the drivers' basket and upper mids and treble are highly directional, they augment the woofers high frequency output with a tweeter.

In comparison, the original Walsh driven Ohm A's and later version called the Ohm F's use very different drivers from the newer versions. While both use one full range driver ( no tweeter or crossover network ) that radiates 360* horizontally and looks like a "pylon" or "road cone" mounted on top of a sealed box, the designs are quite different from each other.

The A's used a greater flare rate near the end of the cone and somewhat resemble the old horns on Victrola's. The cones were made up of two sections ( top and bottom ), each one making use of different metalic materials that were internally damped. The suspension was rubber based. As such, the surrounds do not decay and would not need "refoaming" unless ripped, etc... Efficiency on the A's was said to be in the very high 70 dB range. I'm guessing somewhere around 78 db's or so from what i've read about them. Impedance was spec'd at 8 ohms but later models were much, much lower impedance. As such, it was a phenomenally tough load to drive, especially with the amps that they had available back then. As far as i know, there are VERY few pairs of these remaining.

The F's were basically an attempt to refine the A's. The cones on the F's have a more linear taper and make use of three different materials and arranged in a top, middle and bottom section. Each material was selected for specific attributes within specific frequency ranges. There are even "slashes" that were strategically cut into the bottom section to help break up standing waves along the length of the cone. While the impedance is rated at 4 ohms nominal and 3 minimum by the factory, they actually average closer to 2.5 ohms and dip below 2 at low frequencies. Efficiency was factory rated at about 87 dB's but my experience says something closer to about 82-83 dB's or so. Once again, these were tough loads for most amps back then ( and even today ) to deal with. I have run into problems with some very well respected amps trying to drive these.

Both of these speakers take a tremendous amount of power to function at their best. I remember an old review of the F that stated "anything less than 60 wpc is just not suitable". Personally, i think that an amp that can do at least 300 wpc at 2 ohms without a fuss would be the minimal requirement. Even with that in mind, i have had amps that were rated for 400 wpc @ 4 ohms begging for mercy with these speakers. Obviously, this pushes a LOT of amps out of the equation and proves that not all amps are created equally, regardless of specs.

As to sound, both the A's and F's ( when running right and in good condition ) are known for tremendous low frequency output. I recently had a set doing FIVE Hz ( !!! ) at high output levels. It sounded like a helicopter was inside the house : )

Soundstage is phenomenally wide and deep with a very natural presentation. Notes tend to effortlessly float in the air. This is probably related to the dispersion pattern and fact that you have one driver producing all the sounds in phase with each other.

Midrange sounds very cohesive and seamless, as all the primary notes & harmonic overtones from both instruments and voice are reproduced with no crossover points or multiple drivers to disturb the signal. Highs are very crisp and clear with bell like qualities. Most of that may be attributable to the metalic section of the cone. To minimize "metalic ring" like you get with metal domes, they applied a thin layer of glue and foam inside the driver itself. Not only does this help to absorb high frequency reflections and standing waves inside the driver and box, it also damps the metal membrane.

There were quite a few revisions during the production run of these speakers. Some obvious ones were the design characteristics of the frame used for the driver. I have two sets of these and they are visibly quite different from each other. Other things not noticeable from the outside were the types and quantities of internal damping materials.

These speakers are limited in terms of SPL and dynamic range. They work best for listening at low to medium levels. They can play at higher levels, but attempting to do so for an extended amount of time will almost surely result in either the amplifier or speakers coughing up smoke. Keep in mind that i like "LOUD", so my "medium" listening level might not be the same as yours. Either way, when used within their limitations, they do some things that most other speakers can only dream about. That is why i own TWO sets of them : )

The last Ohm's that i know of that made use of what i would call a "Walsh driver" would be the Ohm G's. These were a short lived model that did things very differently from the earlier "Walsh" speakers. Not only was the height and radiating surface of the driver reduced, the materials used were quite different. Besides that, the Ohm G made use of a passive radiator design rather than a sealed box. This was obviously done to augment low frequency output but also maintain a small amount of damping for the driver. I guess that they were trying to use a smaller, lower mass Walsh to achieve greater high frequency capabilities. By doing so, they ended up losing both mass and surface area in the attempt. Both of these are major factors when it comes time to reproducing deep bass. Anything after the G is simply a "Walsh" in name for advertising purposes.

Obviously, this is just my point of view. Take it for what it is worth. If anyone is interested in further info on "vintage" Ohm's, drop me a line. Sean
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Sean, first let me say that I aways enjoy your posts. They are detailed yet succinct. You have the ability to share your impressions with out resorting to hyperbole. To the best of my limited knowldege they are acurate and technically sound. To top it all off you can write. The professionalism of many so called experts palls in comparison. Your response to a query about a classical radio station in Texas drew my awe.
Of all the various incarnations of these speakers, which are your favorites? Which ones might you suggest as worthy of a hunt? Are any of the current models a consideration?
I have been toying with idea of using these speakers set up along the long wall 50% out from the back wall, 25% out from the side walls with the listener midway and against the opposing long wall lined with some absorbing padding directly behind the listener with an all TacT system. Have you any thought on this scheme?
As always, thank you in advance.

Sean,

I think that you are mistaken about the design of the newer Ohm drivers. The reason that I say this is from reading Ohm's literature and from listening to the speakers. If the can was just a woofer/tweeter combination then you would not get the line source type of sound from them. That said I agree with your comments about the speaker's performance. The area where they come up short is that they won't deliver high SPL's. If you try to overdrive them then the protection circuitry will start to kick in. (This happened to me last night. I was running a high blood alcohol level and cranked it up too high). My thoughts about correcting this is to add a separate sub woofer to handle the low end. Unfortunately I can't afford to do this at present. Gold at $350 will change my life. Check out DROOY, HGMCY, and NEM. Take care bud.

7p62mm, i wish i still had the digital pictures of what the insides of those "cans" looked like. I'll just say that i'm NOT "guessing" at what is inside of them.

I have also discussed this with a local dealer. Not only is he a former authorized Ohm dealer, he is known nation-wide for speaker repairs. As such, he has seen the "guts" of many speakers, including the later "Walsh" drivers. In his own words, he stated that the Walsh series used a "conventional" woofer and was not anywhere near the speaker that the A's and F's were. Knowing what was inside of them and also hearing the lack of performance ( compared to earlier models ), he had a hard time selling them. As such, he dropped the line. I think that this may be a large portion of why Ohm can no longer be found in dealerships.

I do have one question for you. Given the overall height of the original F driver, which is 16" tall, what kind of "Walsh" could you fit inside that little mesh "can" ? Now figure out how you're going to mount both a tweeter and crossover components inside that can. Believe me, it's NOT pretty or even well executed.

If you are feeling brave ( don't do it while "relaxing with a drink or two" ), take your "sealed can" apart. While this will affect your attitude of how you look at those speakers after doing that, it should not alter the level of respect that you have for how they sound or their presentation. If you are happy with them and what they do for your musical enjoyment, my suggestion is to STOP looking at threads like this and start listening to more music. I need to take my own advice and do the same thing. I think that we would all be a lot happier. Not only that, i could actually spend time getting things done and quit blowing so much money on stuff that i don't really need : )

Unsound, thanks for the kind words. I do what i can with what i've got. Obviously, that means that i've got too much "unproductive" time : )

I've often wondered about doing something similar to what you discuss. It is something that i will probably check into in the future. Right now, i just have too many other projects going on to consider it.

As to what model i would strive for, i think that this is obvious. I would look for a GOOD set of Ohm F's. Only problem is that many ( if not most of them ) will need an overhaul or have been physically damaged to the point of no return. The foam will have rotted, voice coils may be damaged, the spiders ( part of the driver suspension ) will be sagging, etc... As such, you would be looking at quite an undertaking should you want to take on such a project.

Most people that have these speakers or do purchase a pair have probably never really heard what they are capable of. Those that have will not part with them. Even with the less than optimum performance that they will deliver in the average installation, it has been stated about them ( and i quote from a review ) "The Ohm F is an extraordinary loudspeaker. It has only one driver, which acts as a pulsating cylinder, translating the electrical impulses of the operating amplifier into sound without disturbing the phase relationships of the impulses. What this means in terms of sound quality is remarkable. The "coherent" sound produced by this speaker is clear, full and undistorted. It may well be the finest speaker on the market, and is certainly without a doubt among the top few. It requires a tremendous amount of power to operate: amplifiers of less than 60 watts per channel are just not suitable. But given the proper associated electronics, the Ohm F is capable of providing almost absolute realism in the listening room."

Keep in mind that even most "expert" and "professional" speaker repair facilities HATE working on Walsh drivers and some won't touch them with a ten foot pole. The second pair that i bought was just about ruined by an extremely well respected and well known "speaker rebuilder" and tube gear manufacturer. Even with as poorly as the speaker was performning when he was done with it, it impressed him enough to try and design his own version of it. He is currently marketing them on a direct purchase basis and claims that they work like no other speaker.

I have since had the second set repaired but not without consequence. Needless to say, i don't have many kind words to say about the first "expert" that worked on them. I have thought about starting to repair these drivers myself, but i would first need to find a pair or two of "basket cases" to experiment with. I'm not about to "gut" the two pair that i have for the sake of advancing my knowledge of them. Sean
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