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HORNS
If you have never heard, at the very least, a speaker system with a properly designed and integrated midrange horn, you are in for a real "shock and awe" experience. Most people just don't have the space for a bass horn- they are very large indeed. So, if you want to explore using horns, the lower midrange is a reasonable starting point.
The problem is, finding a properly designed midrange horn and driver. Properly designed in this context means, "good for ultra fidelity audio." Properly integrated means not relying on eq's, filters and other to patch up what was a mess to begin with. Choosing the right horn and driver combination from the start avoids this pitfall.
There are two main issues. One is with the horns themselves. The other is with drivers, modern and vintage. Let's look at the horn issue first.
Almost all vintage theater or pa horns have big problems when used in a home environment. They are usually very wide in their directivity, for example. These horns were meant to evenly spread sound to cover all of the audience. Personally, I love the big RCA multicells which allow one to enjoy music virtually anywhere in the Mill's main listening room, (which you can see over at the Mill System section.) But notice that there is a conical horn sitting on top of those multicells. Its there because it sounds more open and natural in the upper midrange- which is what it's (properly) designed for. It's a conical horn and conicals were never used commercially because they do not load down low as well as other profiles, such as the exponential, hyperbolic, or even the tractrix. Because the conical horn has to be larger than its relatives to accomplish the same frequency extension, it was ignored commercially. No one either noticed or cared that it sounded the best of all the profiles. Here is a comment from Bill Woods, designer of AH! Acoustic Horn Company, as to why that is:
"Conical horns have one unique characteristic that sets them apart form other horns. The horn walls are straight, with no curvature. This type of horn profile has the least amount of deformation to the wavefront. Once you curve the wall of a horn,
the wavefront is confronted with multiple angles of reflection, disrupting the sound. Kind of like a billiard table with a curved bumper. You just can't easily control the direction of the ball, with the pool table disrupting the motion of the ball. For the above reason, a conical horn also has near perfect phase, so that the sound from the mouth of the horn arrives in a homogeneous pattern."All OMA designs are conical. They are also beautifully made, using classical materials and design. No brightly colored plastic, fiberglass, and its ilk to be found here. Only solid castings of aluminum and bronze, and solid, real hardwood, hand finished with non synthetic coatings like real, flake shellac and oils.
The other issue with horns is the drivers to use with them. DIY'ers have for decades realized that there is a plethora of great sounding vintage compression drivers which can be used with horns to great effect. But modern manufacturers of horns for hi fi have a big problem. They can't rely solely on vintage drivers to make their product. They have to resort to pro sound drivers, which just sound wrong or much worse, used in this application. Bill wanted to make horns for people who had those great vintage drivers. Actually, you can use these horns with any drivers you wish. If you like the sound of beryllium or titanium diaphrams, putting them on a conical will give you back just that sound.
If you would like advice as to what drivers to search for, OMA can give you very precise information on just about anything you might find on the vintage market.
OMA is currently offering a true 300hz conical horn, the OMA300, a 250hz flare rate conical horn, 50 degree dispersion, to be used with large format compression drivers such as the Cogent DS1428, the RCA MI1528B, the RCA permanent magnet series MI9584, 9548, etc, the JBL 375, Altec 288, Vitavox S2, etc.
This horn is extraordinarily innovative on many levels. The first is the throat casting.
The cast throat, available in either aluminum alloy or bronze, is designed to accept virtually any compression driver ever made, even the Western Electric 555 which has a very small threaded throat of 5/8". This is accomplished by machining the ends of the casting down to the correct step, to which an aluminum waterjet cut mounting plate is attached. You simply indicate the driver you wish to use when ordering the horn, and we make the correct mounting plates. The throats are available in regular or polished finish, and aluminum or bronze.
The wooden section of the horn is composed of 12 "petals" of solid Pennsylvania hardwood- either walnut or cherry. These are completely cut and built by hand, using a technique of joinery known as splining, in which a long tenon of the wood attaches the two petals to each other. Because of the complex angles involved, this is an extremely difficult piece of woodworking. The horns are then finished with hand rubbed crystal shellac, or with an oil finish. No synthetics here.
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| OMA300 300hz conical horn in solid Pennsylvania walnut, shown in hand rubbed crystal shellac finish. All horns come with the throat casting machined for your driver. Casting shown is the hand polished version for the Cogent DS 1428 Loudspeaker. | ||
The horns can be employed to approximately 300Hz. The AH300 is the only wooden conical horn being offered anywhere to my knowledge.
Pricing (includes mounting plates for your drivers)
Horn Dimensions- Length (without driver): 24.5" Diameter of mouth: 26"
Price per pair of finished horns, ex. shipping- $4500
With polished throats add $575
Contact us for prices and more information
Photos © OMA