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Lake TechnologyTheaterPhone Surround Headphone Monitoring Hardware and Software

Australian company Lake Technology has developed an effective method to monitor discrete 5.1 surround sources over standard headphones. Lake has licensed its breakthrough technology to Dolby Labs, marketed under the trademark "Dolby Headphone."

Australian company Lake Technology has developed an effective method to monitor discrete 5.1 surround sources over standard headphones. Lake has licensed its breakthrough technology to Dolby Labs, marketed under the trademark “Dolby Headphone.”
Product PointsApplications: Studio, post production, multimedia

Key Features: Hardware version features six channels of balanced analog TRS 1/4-inch I/O, 24-bit/48 kHz converters, and line outputs for headphone distribution amps. Both versions feature three listening environments and A/B switching between 5.1 and stereo down mix.

Price: HSM6240: $1099 TDM plug-in HSM5.1: $499 list.

Contact: Lake Technology at 916-624-7500, Web Site


+ Convincing multichannel reproduction

+ Many pro uses

+ Solves many logistical surround monitoring problems (cost, space, noise)


– Latency could be “near the edge” of usability for studio overdubs, and in-ear stage monitoring.

The Score: An innovative and effective method to monitor discrete 5.1 surround sources using standard stereo headphones.
This technology has already been incorporated into a broad range of consumer-oriented products including notebook and desktop computers, airline in-flight movie systems, and home theater products, with many more to come. Lake is now targeting its TheaterPhone technology for professional audio applications in two flavors: a standalone hardware unit (HSM6240, $1099) and a ProTools TDM plug-in (HSM5.1, $499).


Both the hardware and TDM plug-in versions of TheaterPhone accept discrete 5.1 channel inputs and create a near-correct spatial image over standard stereo headphones. As one might guess, providing this type of time-based effect, without all kinds of comb ‘filtery,’ ‘phasey,’ ‘flangey,’ artifacts, is a Herculean task for digital signal processors (DSP)-a feat that Lake pulls off succesfully.

The single-rackspace hardware version utilizes 12 1/4-inch TRS-balanced connectors on its rear panel for 5.1 channel inputs and pass through, permitting insertion in a 5.1 monitor path. Two RCA jacks provide -10 dBV unbalanced output of the “binaural” signal and two 1/4-inch TRS stereo jacks allow two sets of stereo headphones to be plugged in on the front panel. A small switch on the rear panel allows selection of +4 dBu or -10 dBV for the discrete 5.1 connections.

Front panel controls include headphone volume, a bypass switch and buttons for selecting the three different room simulation modes. Power is provided via a outboard wallwart adapter. Non-U.S. voltages can also be accommodated.

The TDM plug-in includes two different versions, one for insertion on individual channels, and one for insertion on a 5.1 mix fader. Pro Tools version 5.1 or greater and Macintosh OS9 or greater are required.

The TheaterPhone TDM version uses an entire DSP chip on Pro Tools Farm/Mix cards. When inserted, the pop-up window resembles the front panel of the hardware unit and provides the same set of functions, except via mouse click. TheaterPhone includes three different “modes” of operation: DH1 emulates a dry, well-damped room, similar to a good control room. DH2 emulates a larger playback room, with added early reflections. DH3 emulates a large theater or dub stage.

In use

For 5.1-channel surround playback, you need a multichannel amplifier, five calibrated main loudspeakers and a subwoofer. Elementary, right? Now think of all the applications where that many speaker components are inconvenient, too costly or logistically impossible to setup.

Using Lake’s TheaterPhone, all you need is any pair of stereo headphones, and you are monitoring in 5.1! I’m not saying that this will take the place of a properly calibrated 5.1 channel system for mixing, but the applications are numerous where a full setup is not feasible. As of this writing, I am still finding more uses for both hardware and software versions of this unique DSP algorithm.

Here’s a great one that my colleagues and I came across late in the review process. As you may know, in addition to my studio work, I teach post-production audio at the Conservatory of Recording Arts in Tempe, Ariz., which is Digidesign-certified to teach the Pro Tools 135 and 235 curriculum. We just upgraded a few weeks ago to the new version 5.1 of Pro Tools. Since I’ve been involved in surround sound and mixing for several years now, I was talking with Chris Gough, our Pro Tools’ department head, about how exciting this will be to have 5.1 mixing on that platform.

Well, Chris wasn’t quite so excited. “How can I have students on six or seven Pro Tools rigs in the same room monitoring in 5.1?” Even if it were possible to set up 35 or 42 loudspeakers, what a chaotic mess – yikes! Well, with the purchase of several copies of the TheaterPhone plug-in, many students in the same room can be listening in 5.1 on headphones simultaneously.

I have to give credit to Keith Morris, one of my colleagues and a veteran in live sound and FOH engineering, for coming up with another novel application of TheaterPhone. When he heard we had the HSM6240 box (hardware version) on campus, he came running over and grabbed it for his “in ear” monitoring class.

Using Lake’s box, Keith has been experimenting with all kinds of new “in ear” mixes. How about having the drum kit mixed “behind” you, so your lead vocal, guitar or keyboard is in a different position from Front Left, through Center, to Front Right. TheaterPhone excelled in providing a spatially separated sound stage for live monitoring.

Another use for TheaterPhone is for location surround recording. For instance, I wish this unit had been out last year, when I recorded a live choir concert using 5-channel miking. I had no way of monitoring the surround image due to venue restrictions (no time or place to set up 5.1 monitoring with loudspeakers.) I had to “guess” by auditioning various microphone positions in stereo. I had to rely on my previous experience in 5.1 miking, since I didn’t have adequate monitoring.

I also used the TheaterPhone for another novel use: providing spatial headphone mixes for overdubs in the recording studio. I’ve worked with several R&B/hip-hop artists over the years. These sessions often required heavily layered vocals. During tracking, I would naturally build multiple vocal passes panned left and right so the singers could hear the current pass in the middle of their phones. This makes it much easier for players to hear themselves as the mix builds.

With multiple auxiliary sends into TheaterPhone, layers of vocals, keyboards, guitar parts, etc. can be panned out into many spatial positions. One caution: a session keyboard player felt that the processing latency was noticeable to his live playing, but not any more than when playing on stage. For him it was “near the edge” of staying in tempo, but he was still able to lay down several overdub tracks with no perceptible problems (Lake states processing latency of the TheaterPhone systems is in the 12- to 15-millisecond range.)

As far as the different room simulation modes mentioned above, I preferred the DH2 position, which adds more “room” type of cues to the algorithm. However, other engineers and musicians favored the essentially dry DH1 position. For my uses, I didn’t find any application for DH3 position, which simulates a large theater or dub stage. Even after auditioning some great DTS and Dolby Digital 5.1 movie soundtracks, I still preferred the DH2 position.

Earlier, I mentioned that the HSM6240 has a two-channel output of the virtual binaural mix. You may already be ahead of me. Yes, you can take this output and record it, burn a stereo CD, DAT tape, etc., which would allow you to send a 5.1 mix to anyone with headphones, or make your own compilation for portable CD or cassette playback. I asked Gary Lynn about possible commercial implications of the resulting binaural stereo track. He said that Dolby and Lake are aggressively pursuing license arrangements for manufacturers of consumer playback equipment, so that virtual 5.1 headphone monitoring could become ‘standard fare’ for DVD playback and home theater electronics. Beyond personal use, anyone desiring commercial applications should contact Dolby.


Experiencing virtual surround in headphones is one of those experiences that is difficult to write about and explain. The creative geniuses at Lake Audio have taken DSP-powered surround monitoring into new and uncharted territory. I hope you have the chance to experience this soon.