Have you ever listened to a "Voice of the Theatre"?
Have you heard it with Kilimanjaro-Series field-coil speakers?

Altec Lansing 288

Most of us who’ve listened to a VOTT have shrugged our shoulders. I believe this has to do with the enormous model and cabinet variations in the marketplace. And with the drivers...

The Alnico 5 type permanent magnet, which was perfected during the war, was the most important driver feature in the loudspeaker industry at that time. Cooler operation, no need for separate field supplies, and one-third the weight of ferrite magnets were the advantages. But was there something earlier, something before the much sought after Alnico 5?

I assert that many of the audiophiles and connoisseurs don’t have the faintest idea how good a VOTT can sound. Years ago I was invited to Vienna Vibes, and decided to build a VOTT 825 enclosure precisely to the original drawings using spruce ply instead of pine (because of the disposability). I bought a pair of Altec 1505-B horns and outfitted everything with special designed field-coil drive units. For a network I used my universal model (available) dividing the spectrum at about 1500 Hz. The result was more than impressive; and it was instructional for everybody. The last night, a friend of mine and I listened to the complete Studio album "Nothing Lasts... But Nothing Is Lost" (2005) by Shpongle, an English psychedelic music project. The music was truly "like nothing you've ever heard before", and was real magic!

Voice of the Theatre 825 with Kilimanjaro-Series A515 and A285

Voice of the Theatre 825 with Kilimanjaro-Series A515 and A285
successors are available: A1500 and A3000

The A515 and the A285 (successors A1500/A3000) walk on air in the 825 enclosure. These drivers feel so comfortable in a VOTT that I go into a state of rhapsody when I hear them. Naturally I'm committed to my drive units. 

But what is so thrilling about these 'worn' enclosures? 

Lansing Monitor 500, Shearer Horn

The "Shearer Horn", with drivers from the Lansing Manufacturing Company, had become the movie standard in the late thirties. Virtually every loudspeaker manufacturer in the industry was offering a similar concept. But John K. Hilliard published design papers on the "Shearer Horn" system; and by 1945 the problem of time delays between several drive units was addressed. It was then that John K. Hilliard and Jim Lansing introduced their "Voice of the Theatre" speaker system. 

The principal deficiency identified by Jim Lansing and John K. Hilliard was referred to as a lack of presence. This was attributed to a dip in the mid-bass response between 250 and 500 Hz, radiation from the rear of the speaker system, phase discrepancies due to a long, folded horn path, and cabinet resonance.

VOTT A4, single 210
Altec Lansing Voice of the Theatre, VOTT, A5

The model A5 was for Deluxe Presentation Theaters

The primary solution to these problems lay in the design of a radically new bass horn enclosure. For the first time, a bass cabinet was developed that fully enclosed the drivers and eliminated rear radiation. The enclosure front loaded the bass drivers in a direct, flared horn as opposed to the previous folded designs. This eliminated the mid-bass dip caused by dissipation of higher frequencies in the horn folds. However, the front horn was not large enough to propagate bass frequencies below 100 Hz. The solution was to port the cabinet to allow it to act as a vented enclosure down to 50 Hz. The Academy of Motion Picture Arts and Sciences immediately began tests of the new system that confirmed the sonic improvements, and by 1955 the Academy adopted the VOTT as the industry standard for motion picture playback. 

VOTT A5 (825) and A7 (828)
Seiteneinsicht VOTT 825

Voice of the Theatre 825 cabinet partly opened. You can see the braces and you can also see that the bass driver’s voice coil is located in the same vertical plane as that of the high frequency unit. No phase problems, no delay.

Vertical plane of bass and hf unit means in phase

Such big systems normally have the acoustical centers of their different drivers far apart and the units are often not mounted in a vertical plane. Thus making it impossible to listen to music sitting relatively close to the speakers. This is completely different here and makes the concept unique and precious.  

A825 811B DSC0008

A825 with Altec 811-B  horn and Kilimanjaro-Series A801 drive unit…
…maybe the most natural  composition – for sure the smallest

VOTT with A3000 and 1005B horn

Wolf von Langa VOTT 825 enclosure w/white lining and 1005B horn,
A3000 and A1500 field-coil drive unit

Altec 1505-B, 30166 bronze adaptor, Kilimanjaro-Series A285, VOT 825, Kilimanjaro-Series A515, and Altec N-500C

Altec 1505-B multicell horn w/30166 bronze adaptor, Kilimanjaro-Series A285 drive unit (precursor of A3000), VOT 825 enclosure made of fir ply, Kilimanjaro-Series A515 (precursor of A1500C), and Altec N-500C network and others

vott DSC0024

Horn braces and glue blocks

vott DSC0030

…adjusting the height of the drive unit to have the correct imaging in listening position…

vott DSC0031

vott DSC0041-1

Comparison of A284 and A285 on an Altec 1505-B horn

A825 DSC00071

A825 battens and horn curve


Batten position



A285WVL DSC0006

Kilimanjaro-Series A285 center pole, pure iron

Kilimanjaro-Series A3000, pure iron, medium current field-coil, aluminum diaphragm 8 Ohms

Kilimanjaro-Series A3000, pure iron, medium current field-coil, aluminum diaphragm 8 Ohms

Christine von Langa - Roedlas 54 - D - 91077 Neunkirchen a. Br. - Phone +49 (0)9192 996926 - E-Mail: listen(at)wolfvonlanga.com -
WOLFVONLANGA produces unique field coil loudspeakers and drive units. As a manufacturer we solely use the highest quality materials.
We deliver worldwide unique loudspeaker technology. All WOLFVONLANGA products are developed and handmade in Germany.
WOLFVONLANGA is a registered trademark.