Listening #167: Auditorium 23 Hommage Cinema loudspeaker

Keith Aschenbrenner, proprietor of Auditorium 23, based in Frankfurt, Germany (footnote 1), has long been associated with the people and products of Shindo Laboratory: From the early 1990s until the EU's 2006 implementation of the RoHS 1 regulation, which banned the sale of various old-style electrolytic materials—and thus most of Shindo's products—Auditorium 23 was the brand's European distributor and, arguably, one of its most empathetic and enthusiastic retailers worldwide. Throughout that time, and continuing through to today, Aschenbrenner has also worked as a designer and manufacturer of Shindo-friendly ancillaries and loudspeakers.

Those speakers have included some popular models, such as Auditorium 23's Rondo and Solovox models, both built around full-range drivers from the French company Phy-HP. Yet Aschenbrenner—who, for years, listened at home to a pair of vintage Western Electric 555 field-coil compression drivers loaded with large, ungainly horns—has continued his efforts to design new speakers that, in his words, help the listener "rediscover the qualities of the amplifiers that Ken Shindo was making." It's worth noting that the amplifier designs of the late Ken Shindo, and those of his son Takashi Shindo, are uncompromising in that they're suited only for very efficient loudspeakers. (With few exceptions, the output sections of all Shindo amps are optimized for 16-ohm loads.)

Somewhere along the line—perhaps 10 or so years ago—Aschenbrenner hit on the idea of a speaker that could combine his preferred 555 compression driver with a modern horn of more modest size, supplemented with similarly efficient bass and treble drivers. That concept now exists as the Auditorium 23 Hommage Cinema loudspeaker ($49,995/pair without field-coil power supply), but to get there required a great deal of work and more than a little luck. "When people would ask me what I am listening to at home, I would be very open and honest. [But] it was my dream to make something like the Cinema, with a very long horn."

Hoping to find a substitute for the exceedingly rare and expensive Western Electric 555—even broken samples go for $5000 and up apiece, while functioning 555s with original diaphragms have become nearly impossible to find—Aschenbrenner turned to his and Shindo's US distributor, Jonathan Halpern, of Tone Imports. In 2010, Halpern had just signed on as the US distributor for the Chinese manufacturer Line Magnetic, which in turn announced that they would manufacture a faithful replica of the 555, to sell for $4950/pair. Although other companies have made compression drivers that were similar to the 555, and some now make 555 replicas of their own—the latter including the respected Japanese brand GIP and at least one or two others—Line Magnetic's 555 replicas would be the first to be offered commercially.

As Aschenbrenner told me, "In 2011, when Line Magnetic came on the market, we decided to try [to make a speaker that uses their 555], thinking, Well, if it's a failure, it's a failure." He then enlisted the help of physicist Uwe Meyer, his design partner on other loudspeaker projects, and set to work. They came up with a folded midrange horn that's over 43" long, yet is contained within an area just 19" deep. The Line Magnetic 555 driver is fastened to the horn's throat by means of a cast-bronze coupler shaped at an angle of 80°. This hands off to the first of three wooden horn segments, starting at a cross-section of approximately 1" and exponentially increasing in size. A 180° bend leads to the second horn segment, which leads, through another 180° bend, to the third and final segment, the mouth of which is 15" wide and 15.5" high. The horn itself is made entirely by hand, mostly of European spruce, with select hardwoods used for some parts. According to Meyer, "the ratio of heavy to light woods and the thickness of all materials had been proved to be very important" to the sound. All surfaces of the horn are given what appears to be a hand-rubbed oil finish. (When I unpacked the Cinemas, the first thing I noticed was the distinct, pleasant aroma of linseed oil.)

The result is a horn that, in combination with the 555 compression driver, has an effective range of 200Hz–7kHz. As for the Line Magnetic driver itself, Aschenbrenner praises its unit-to-unit consistency—in contrast to the original, no two of which seem to sound exactly the same—and its sound quality in absolute terms: "I have four original Western Electric 555s. Now they are on the shelf."

Compression obsession
Looking at the Hommage Cinema from the side, you could be forgiven for thinking that its 555 driver is loaded with a single-segment, unfolded horn: Most of the bronze coupler and all of the horn's first two segments are concealed within a wooden tray whose tapered sides are shaped to match the curves of the visible portion of the horn. The tray, which is covered with thin padding and fabric, gives the horn a flat bottom, to which are fastened four bronze feet, each 1.5" in diameter, with hollow centers and stiff felt washers. The feet fit neatly atop four corresponding pegs built into the top of the Cinema's bass cabinet, which measures 27.5" high by 14.75" wide by 16.5" deep. (The bass cabinet is supported by four adjustable feet—similar to but larger than the midrange horn's bronze-and-felt feet—that add about 2" to the speaker's overall height.) Much of the bass enclosure is upholstered in the same manner as the base of the midrange horn, although on portions of the front and rear surfaces, there's no wooden structure immediately behind the fabric: in these areas, the Hommage Cinema's bass cabinet appears to be an open design.

That was confirmed by Keith Aschenbrenner, who described the loading of the Cinema's two bass drivers—one 12" woofer and one 7" woofer—as being unique: "The large woofer is loaded on one side with a horn, and on the other side with a port. So it is a dipole, but with a complex [loading] structure to minimize the output—to deliberately limit, acoustically, the high-frequency output of the large woofer. The small woofer is on an open baffle, with perforations, for air movement. [Thus] we adjust the rolloff of the two drivers differently."


As for why the Cinema uses two dissimilar woofers, Aschenbrenner points to the challenges of making a full-range loudspeaker work in rooms of different size and character: "It is due to the interactivity of low frequencies and the room. These two different-size woofers are chosen because, if you have two woofers [of the same size] and there's a problem, there is double the problem. Having two different woofers minimizes the failures of similar woofers." He says that the large woofer reproduces fundamentals down to 50Hz, while the small one gives the Cinema its ability to re-create the "flavor and character" of recorded music. Uwe Meyer added that "the acoustical crossover frequencies are between 150 and 200Hz for the 12" driver and a bit more than one octave higher for the 7" driver."

Each Cinema bass enclosure contains two 50W, solid-state, class-AB amplifiers: one each for the 7" and 12" woofers. Each amp has its own input transformer, driven by the signal from the user's speaker cables (as opposed to line-out cables from the user's preamplifier), and each has its own user-adjustable level control, labeled Volume Woofer 1 (12" driver) and Volume Woofer 2 (7" driver). Next to those knobs, on the speaker's rear panel, are banana-style inputs for the system's main speaker cables, plus separate pairs of output jacks, also bananas, for directing the output of the Cinema's built-in amps to the 555 midrange driver and 597A treble driver.

The 597A is itself an interesting beast: As with the original 555, Western Electric patented the 597A in the late 1920s, and introduced it to the cinema-sound market in 1929. Also like the 555, it was a field-coil-energized compression driver with a lightweight aluminum diaphragm—yet the 597A, which is designed to reproduce frequencies up to 10kHz and beyond, is loaded by its own integral, 5"-long, exponential horn, the shape and color of which bring to mind the telephone used in all six seasons of Green Acres. (Indeed, as the sole supplier of equipment to AT&T and the developer of countless historically significant developments in the parallel fields of telecommunications and sound reinforcement, Western Electric referred to all of their earliest cinema-sound drive-units and speakers as loud-speaking telephones.)

Original samples of the Western Electric 597A are even rarer and more costly than the WE 555—at present, the going rate seems to be $10,000 and up for a single 597A. Consequently, the 597A used in the Hommage Cinema is a replica, also manufactured by Line Magnetic (and sold separately for $5950/pair). (For this accomplishment, the Chinese company appears to have been beaten to the punch, by GIP, as well as an independent designer-builder known only as Mr. Ogawa, whose work Aschenbrenner admires.) This is fastened to the upper edge of the Cinema's bass enclosure by means of a simple L-bracket, with the suggestion that the user install the speakers with their tweeters on the outer sides of the cabinets. (As originally conceived, the Cinema's 597A was mounted on a structure atop the housing of the 555 driver; this was ditched in favor of the side mounting.)

As specified by Western Electric, the original 597A and 555 drivers required 7V DC each to magnetize their field coils, used in place of permanent magnets. Like other contemporary manufacturers of field-coil loudspeakers, Auditorium 23 has noted that some degree of variance from the 7V norm is not only acceptable but, in some domestic installations, desirable. Thus the field-coil power supply included with each pair of Cinemas allows the user to adjust the voltage, in 0.1V steps, from approximately 4V to at least 8V. (It may go higher than that, but I wasn't comfortable trying.)

The Cinema's standard field-coil power supply, the NT1 ($5495), was designed by Claus Jäckle and built in Germany by his company, AcousticPlan. The NT1 measures 8" wide by 7" high by 12.5" deep and is built on an aluminum chassis, covered on top and on two sides by a distinctly cool-looking—in every sense—steel-mesh wrap. Inside are a big transformer, big capacitors, two big rheostats for adjusting voltage—each controls the voltage for one pair of output jacks, and it's up to the user whether to assign each of the two pairs to a given speaker or to let one pair do the tweeters and the other the midrange drivers—and two big selenium stacks for rectification. As with all of the AcousticPlan electronics I've seen, the NT1 is beautifully styled, with a machined aluminum front panel and machined aluminum control knobs, all finished in a matching shade of dark gray; these elements are executed so well that the NT1's entire front end looks as if molded or cast in a single piece.

Footnote 1: Auditorium 23, Thüringer Strasse 4, D-65824 Schwalbach, Germany. Tel: (49) (0)6196-402-516-8. Web: US distributor: Tone Imports. Web:

Anton's picture

I will seek out this piece of kit to hear, but one question from last month's column will remain sadly unanswered...

"And how was it that companies in the 1930s could offer, for reasonable prices, technologies that all but a few modern manufacturers declare are "too expensive"?"

55K is still well north of what most of us, I suspect, can reasonably toss around.

Herb Reichert's picture

high resolution - voice articulating - audio reproduction was a matter of national, commercial, and strategic importance. Think cinema, telephone and international communications -- Low distortion audio was the NASA space program "rocket science" of its time -- cost was not an object

"And how was it that companies in the 1930s could offer, for reasonable prices, technologies that all but a few modern manufacturers declare are "too expensive"?"

Severius's picture

I'm watching the world series as I type this, in which the Chicago Cubs appear for the first time in 71 years. A baseball analogy seems appropriate here:

A.Dudley* has been absolutely, positively, unquestionably perfect in during his stint at Stereophile - batting 1000.

Heck - he's even managed a metaphysical 1001.

Not once; not one single, solitary, infinitesimal split-atom-nanosecond in time/space -or even beyond it - has The Prophet ventured anywhere near to auditioning anything but the most non-linear, midfi-to-ultra-low-fidelity rubbish available [short of blaster PA systems - but there's still time], while sneering and spitting on actual high-end gear - when not actually stooping to defecate on the very notion of it.

Why? Cause high-end gear doesn't have any - oops, aint't got no [I have to remember to adhere to the Atkinson/Stereophile Manual of Style - see below] - humaneth. Humaneth.

Adopting and paraphrasing Aleister Crowley's dictum, The Prophet has proclaimed that Humaneth Shall Be The Whole Law.

The wilder the frequency response curve, the grittier the distortion - all distortion - the more piercing, the more punishingly painful the sound - the more Humaneth the device in question has and - according to The Prophet's - the better it it is.

In the present case [uncannily consistent, as noted above], The Prophet's singled out the following axis of praise"

"Treble extension was noticeably less than one associates with modern loudspeakers, manifesting in lessened air and sparkle with some recordings. (That didn't bother me often...]". And why should it? Who needs some thing as prissy and effete as high frequencies anyway, unless they're really screeching - as is the case in many of The Prophet's favorite fullrangers.

"Bass notes were, again, a little more rounded than I think is absolutely neutral...(But that didn't bother me, either...]". Of course not. It ain't jack if it don't thump [learning good usage quickly from the 'Phile's Pulitzer Prize winning journalists].

Most important is that the devices - whatever they may be; amps, loudspeakers, FM tuners, anything - lack that most hated, the most Harry Pearsonesque of all attributes: imaging and spacial depth of image. Those depraved items prevent you from hearing the musicians. Humaneth means " keeping my attention focused not on the sound of the hall or the artifacts of the recording technology, but on what the musicians were doing".

Because, those are mutually exclusive categories. You jest can't hear the music if your gear's actually reproducing the hall and placing the musicians in three dimensional space. That's totally that depraved, windbag, Harry Pearson high-end swindle crap.

Being at least partially hearing impaired really helps your own personal Humaneth. And, timing. Timing. Ragged, low-fi sound with great "timing". That's really important.

For his coup de grace, The Prophet demonstrates his considerable writing skills, which in turn demonstrate his powerful intellect, by using profanity. After all, what would a Dudley piece be without adolescent expletives? But, The Prophet's no ordinary pimply sixteen year old imprisoned in an sixty-year-old fart body. No sir. Here, The Prophet enlarges our language with a brand newly made up profanity: "fuckery". As per Atkinson's Manual of Style.

Exactly what you want your kids/grandkids/nephews reading as you try to introduce them to the dying field of high-end audio.

As is typical of The Prophet's faithful disciples [and who isn't one?], "Anton" above praises The Prophet for his "Wonderful Review, Good Perspective". Yes. Completely.

*The Holy Prophet of Audio, who'd every utterance and incoherently formed thoughts are sacred and of which all of us are unworthy.

HammerSandwich's picture

Perhaps you should have posted a bunny photo instead.

Jason Victor Serinus's picture

Thank you so much for your succinct commentary. I want to marry you and have your baby. But since I'm past childbearing age, I shall instead make do by posting a bunny photo on my wall, dressing it in Holy Prophet garb, and calling it Peter Severius. Perfect for Halloween. Hmm... I could even dispense treats dressed as the Holy Severius.

Severius's picture

Severius! is my actual nom de guerre.

But, your site doesn't allow for punctuation in screen names. You may look up my internet audio legacy on, and even better on the original [although all of that original site's gone].

-Neward Thelman, aka Severius!

Anton's picture

Art probably poops bigger internet audio legacies than you after eating corn.

Severius? What don't you just smite The Prophet with your magical lightning bolt +20HP?

Here's a little help: change your name to The Severius. ;-P

Anton's picture

So, who on earth wants his/her kid, grand kid, nephew, niece, etc. to have to sit through your fist shaking equivalent of "You, Art! Get off my lawn!"

LOL, Audio Crank.

These types of speakers can sound awesome, in case you are too good to listen to different things.

If you ever leave your lair....The epitome of this type of sound, I think, is often produced by a company called Silbatone at Hi Fi shows.

They use nearly 100 year old speakers matched with Silbatone electronics that are honestly startling in terms of their musicality and 'rightness.' Even other manufacturers walk around saying WTF (ask your nephew to translate) about how good those babies can sound.

Our hobby is about listening and finding pleasure, and this sort of speaker is simply one way to enjoy.

For your nephew: Please tell your uncle to shove the "The Prophet" stuff up his ass. Now, go listen to as many different Hi Fi set ups as possible, don't listen to your crank uncle, and have fun. If you ever want to so bitterly piss and whine about something as harmless as a column about a vintage styled horn speaker, please refer back to my first sentence in this paragraph. Cheers!

Uncle Severius, I think your up-tightness extends to your tympanic membranes. (I have a hunch you can't spell Harry Potter character names, either. Either that, or I'd wager you have a fine little 1:64 scale fully painted Warmachine toy.)

Severius's picture


Anton's picture

Astute of you!

John Atkinson's picture
Severius wrote:
Treble extension was noticeably less than one associates with modern loudspeakers, manifesting in lessened air and sparkle with some recordings. (That didn't bother me often...)". And why should it?

It did bother me when I listened to the speakers at Art's before measuring them for a follow-up review to appear in our January issue. In that follow-up, I do suggest that something like the tweeter used by Zu Audio would be sensitive enough to match that superb-sounding horn-loaded midrange unit. However, in his "Manufacturer's Comment" in the January issue, Keith Aschenbrenner explains that using such a tweeter would not be historically appropriate.

John Atkinson
Editor, Stereophile

rschryer's picture

No one is telling you what you should like or read, Severius. IF AD's writing offends you, turn the page. Just try to have some fun, okay? This is a hobby, not a debate on abortion.

dalethorn's picture

Horns are fascinating, and not just because they're incredibly efficient. The efficiency is certainly a part of it, in that you're hearing the amps at probably a much lower power level that they were designed for, or if they were designed for very low power use, a unique kind of amp. I imagine that one of those AES acoustical engineers could describe a number of ways those horns move air differently than cone speakers, or even electrostatic speakers, and how they sound different as a result. I've heard only the Klipschorns, in the 1970's, and they were impressive.

domainedujac's picture

Pleasures are dear and difficult to get.
Feasting the eye, fat grapes hung in the arbour,
That the fox could not reach, for all his labour,
And leaving them declared, they're not ripe yet.

Johnny2Bad's picture

Anton asks " ... "And how was it that companies in the 1930s could offer, for reasonable prices, technologies that all but a few modern manufacturers declare are "too expensive"?" ..."

Well, they were not "reasonable prices" back in the 1930's in the first place. They are rare because no-one, with rare exception, could afford them and the associated amplifiers. Most people played records on a turntable with an acoustic, not electric, horn. And few people could afford those.

Herb Reichert's picture

the Western Electric 12A to be the first "electric" loudspeaker (ca. 1927?). They are LARGE wood horns and were driven by the WE 555 field coil compression driver refered to in AD's story. They are extremely rare but I auditioned a pair recently and (to my ears) -- no loudspeaker driver ( today or yesterday) delivers a lower distortion midrange.

Just sayin'

Herb Reichert's picture

It was 1926 - "Vitaphone sound system for motion pictures used a new speaker developed at Bell Labs. Wente and Thuras designed the Western Electric 555-W speaker driver that was coupled with a horn having a 1-in. throat and a 40-sq. ft. mouth; it was capable of 100-5000 hz freq. range with an efficiency of 25% (compared to 1% today) needed due to low amp power of 10 watts. The power amps were 205-D. Older loudspeakers were balanced armature type, but the newer 555-W speakers of the Vitaphone were moving coil type." sorry

BTW: these were not sold to end users. They were leased....for five years. Uses were instructed to destroy the 12As at the end of the lease period. Each 12A horn had over 100 seperate wood parts - none of which possessed a right angle. How much would that cost today?

Svein01's picture

Dear Art,

I love your review and I hope I get to enjoy music trough the Auditorium 23 HC at one point in time. I personally own a Avantgarde Acoustic Duo Omega (G2) that plays in harmony with a pair of Thöress 300b SET amplifiers and a Cary SLP-05 as preamp. I have enjoyed many audio systems, but with the Avantgarde horn speakers being conducted by the Thöress I swear I can see the reflections of my own image in Miles David´s trumpet on the Kind of Blue album, or see the smallest movement of the skirt of the blonde girl sitting next to me is the club at Frank Sinatra´s album Sinatra At The Sands.

Why am I writing this romantic, personal praise of my own system? Simply to encourage you to write a review of a what I consider to be a modernistic take of Auditorium 23 HC, the Avantgarde Acoustics Duo (or indeed the Avantgarde Acoustic Uno, witch I have not listen to myself). It would be very interesting to get your thoughts on this speaker, and while I am no big fan of comparison test, it would be interesting to get your thoughts on the travel horn speakers have gone true since the classic Western Electric days to modern, highly engineered and scientific based horn speakers like the Avantgarde Acoustics.

And if you do decide to test or simply listen to the Avantgarde Acoustics, I highly encourage you to listen to them together with the Thöress 300b, for your own listening pleasure.

Best regards from Norway

domainedujac's picture

•Ask the right questions about value; “we tend to overvalue the things we can measure and undervalue the things we cannot.”

domainedujac's picture

My Japanese friends called these 1930s Western Electric tube creations "talkie amps," for the millions of movie houses, telephones, radios, and PA systems they were designed to power. During the Great Depression, "speech intelligibility" was of immense strategic, economic, and political importance. In America, audio engineering was to the 1930s what the A-bomb was to the 1940s, what NASA was to the 1960s, what railroads were to the 1830s. Just imagine, the world's best minds and $$, all focused on accurate, "mirror-like" audio reproduction.

Herb Reichert, STEREOPHILE

Surge's picture

I wanted to like A23 when I was shopping for just this type of speaker. I don't care much for Shindo, but I have a full Kondo Japan setup, using the 8W Souga, M77, Sfz, SME V8 Kondo wired tonearm, and all Kondo silver cabling.
I would never run a LM Chinese driver in such a setup. To be honest, the cost of the speaker should be $5K, max, to justify such a low end driver.
Plus, the horn shape is just plain wrong. Look around, no other respected horn speaker design uses that non-symmetrical shape.
Looks nice, but again, at $50K we expect much more.