Product Review - Anthony Moore Ambience Ribbon Hybrid Series; Planar-Magnetic Speaker - May, 1996

By John E. Johnson, Jr.

Anthony Moore Ambience Ribbon Hybrid Series; Planar-magnetic speaker; 46" five leaf ribbon mid-range/tweeter, 7" bass reflex cone woofer; Crossover frequency 420 Hz, third order; Frequency response 29 Hz - 15 kHz; Sensitivity 86 dB/w/m; Power handling 125 watts; Black grille cloth with solid wood frame; Size 5' 3"H x 17"W x 14 1/4"D (Panel plus woofer enclosure) 1 3/4"D (Panel only); Weight 75 pounds each; $4,950/pair (Rosewood); Other woods available include golden oak, jarrah, teak, mahogany, and walnut; Anthony Moore, Ambience Speakers, Back Corringle Road, Newmerella, Victoria 3886, AUSTRALIA; Phone/Fax 051-54-2576; USA Distributor: Music Labs USA, Inc., P.O. Box 148, Denver, New York 12421; Phone 607-326-7689; Fax 607-326-3436; E-Mail [email protected].

There has been much discussion on the Internet about the use of dipolar and bipolar speakers in home theater configurations. The planar-magnetic design represents the dipolar speaker in its purest sense, as the ribbon is open at the front and the back in an equal manner. Usually, a cone woofer is also used, because the ribbon cannot move enough air at low frequencies. In the case of the Ambience, the woofer is a 7" long throw cone in a 23 liter bass reflex enclosure (MDF painted black) tuned to 32 Hz. The 2" flared port is on the rear. The crossover frequency is at 420 Hz. This is higher than some other planar magnetic models, and the result, in our opinion, is that the ribbons will last longer (the ribbons tend to stretch out with use over the years, attenuating their accuracy). Planar-magnetic ribbon speakers work on the principle of having a corrugated metal foil strip that is suspended tightly between powerful permanent magnets. There are two types of planar-magnetic speakers. One, the true ribbon speaker, has the foil itself suspended with tension at the ends of the foil. The other, called quasi-ribbon, has the foil attached to a plastic membrane, and it is the membrane that is suspended with tension at the ends. The quasi-ribbon is sturdier, but it has less high end transient response, because the total mass of the foil and plastic membrane is greater than just the foil, and it cannot respond as quickly. The Antony Moore is a true ribbon speaker. When the musical signal current flows through the foil, the magnetic field created around the foil causes the foil to be attracted or repelled by the permanent magnets depending on which direction the current is flowing in the foil. The movement of the foil back and forth creates the sound. This is called a line source driver.

One has to have a taste for not only the dipolar sound, but planar-magnetic designs in order to appreciate a speaker like the Ambience. We have long had a taste for both, and the Ambience is a superb example of the best that such speakers can be. Planar-magnetics can be had for much less money, but the craftsmanship on the Ambience is worth the extra price. Our review units had solid planks of Australian Hardwood stained to Rosewood, serving as the frame. Hardwood veneer is expensive, but solid planks of it? Wow! In Australia, it is against the law to cut down native wild rosewood trees for use in furniture (can you blame them?), so other hardwood trees are grown specifically for this use. The difference is that the wild trees are much older and have a deeper color to them. The grown-for-furniture trees have the grain, but not the deep color. So, by application of stain in the finishing stage, the color of the wild tree is approached. That is what was done to our review samples. Specifically, they are made from "Shining Gum" stained to the Wild Australian Rosewood color. The speakers are large enough, that photographing them from a distance to show the entire speaker would not do them justice. Therefore, we took our photo up close with the reflected light angled so that you can see not only the grain texture, but the deep color (see photo). By window light, they appear almost violet, but by incandescent, they are burgundy, and exquisite.

Most of us here like deep bass, and I assumed that a 7" woofer would not really deliver the kind of bass that we prefer. Also, I did not think I would like the crossover at 420 Hz, since the cone woofer would be carrying a good proportion of the human voice spectrum (male voices anyway). I argued these points before we even accepted the offer to review the speakers, but we were reassured to just wait until we heard them for ourselves. We were not disappointed.

The Ambience speakers have very high resolution of detail, significantly more than our reference planar-magnetics. In fact, our reference speakers sounded a bit nasal when compared directly, and of course were much deeper in the bass region because they have four 12" woofers (dipolar arrangement) in each speaker. However, the bass in the Ambience was much tighter and cleaner. The sound stage of the Ambience extended about 3 feet on either side of the panels, when the speakers were 8 feet apart and toed in at 15 degrees. And, like all planar-magnetics, they have a very deep sound stage from front to back. They need to be several feet out from the wall to achieve this.

Voices were very natural. No chestiness, even with the cone driver handling those pesky 120 Hz frequencies in an enclosure that was not heavily damped. Tony Bennett and Enya never sounded better. Like all line drivers, we could hear the high frequencies beating if we moved our heads vertically. This occurs because the entire length of the ribbon is emitting the sound, and the waves interact, causing augmentation and cancellation, depending on where the listener is. They are also very dependent on room acoustics, so careful placement is necessary. All dipoles are like this. The woofer produced some audible harmonics when <20 Hz sine waves were played through the speaker.

These speakers are great in the home theater environment. Line drivers produce an incredible sound stage for movies, and, for example, in the early minutes of "The Return of the Jedi" where Vader emerges from his ship after landing in the space port, the sounds of the steam were presented in a way that a conventional speaker just cannot do. Of course, the driver has to be able to really take the intense movie sound track signal and deliver without harshness. The Ambience delivers, and how! Just make sure you have plenty of muscle to drive them though, as they have a relatively low sensitivity (86 dB/w/m).

Frequency Response Tests were performed. It should be noted that with dipoles, half the sound energy is emitted from the rear, so any response test is complicated with the room acoustics, no matter how close the microphone is placed to the speaker. The response test results were as follows:

Near Field, one meter, left channel only, microphone on axis with center of panel:

Far Field, 10 feet, left channel only, microphone on axis with center of panel:

In summary, the Ambience hybrid planar-magnetic speakers are superb. The price is steep, but the construction quality warrants it, and although they may have been designed with CDs in mind, laserdiscs can really strut their stuff with these babies next to the "tube". Count me in.

John E. Johnson, Jr.
Editor-in-Chief

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