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December 1993: Volume 2, Number 4


Canadian Broadcasting Centre: The Tour


AES What's Inside

AES This Month's Meeting Preview

The Audio Facilities of the Canadian Broadcasting Centre

by Tom Shevlin

The waiting is over! The time has come for the tour you have all been asking for. On Tuesday night, December 7, 1993 at 7:00 PM, the Toronto Section of the AES will convene in the Barbara Frum Atrium of the new Canadian Broadcasting Centre.

The focus of the evening will be the audio facilities of CBC Radio and TV in their new Toronto home.

While some shows have been aired from the Broadcast Centre for over a year, many of the most exciting audio installations are only coming on-line at this time. These include several multitrack rooms featuring Neve consoles (analog VRs as well as all-digital Capricorns) along with Sony 48-track digital recorders. A sure highlight is the Radio Drama Studio with its wide choice of both fixed and variable acoustical environments. A probable inclusion is the large and comprehensive sound reinforcement system used for the Friday Night! and Royal Canadian Air Farce TV shows in Studio 41, as well as being portable for use in the field.

A number of the Radio studios which have been in use for some time are of a smaller scale but no less interesting. These include; the Digital Editing Suite, where CDs for public release are edited by (your AES section committee membership secretary) Peter Cook; the Specialized Packaging Studio, otherwise known as "the Son of Studio H", the well-publicized all-digital pilot project from the old Radio Building; the still-under-development Desktop Radio tapeless networked Radio news production system; and the E.A.R. (Experimental Audio Room) Studio, recently described in detail in these very pages. Radio MCR (Master Control Room), the digital audio nerve centre of both the building and the English Radio Network, will also be revealed, along with the production and broadcast studios for your favourite CBC radio programs.

Both TV and Radio production management have been extremely cooperative in helping to prepare this tour, due to the high regard in which AES is held. As compared to the usual "tourist" event, they realise that not only must they be ready for a larger number of participants, but that the technical content must be in much greater depth. To this end, they have provided experts for each station of the tour who are not only users of the facilities, but who also in most cases took part in the long design process for them.

One of the consequences of touring a busy production centre is that there may be omissions forced by heavy activity. While we are sure that most areas will be open to us on tour night, we have already had to make special arrangements outside tour hours to see one of the most interesting facilities of all, the Glenn Gould Studio. This facility, while originally inspired by the church buildings where 2- track field recordings of chamber music were made, has evolved into a multitrack broadcast/recording/live-event all-purpose studio with sound reinforcement capability in the audience area, as well as reception and hospitality facilities, all of the above rentable by the public. While extreme levels of production activity prevent its inclusion in the official tour, the area should be available for viewing for those who can arrive early, between 5:00 and 6:30 PM on the evening of the tour. For those who wish to hear the superb acoustics of the hall for their primary design purpose of chamber music performance, there are free concerts of this genre most Thursdays at noon. (Note: as your Chairman had rather a lot to do with the electronic aspects of this facility, he would be more than pleased to greet you there on tour night.)

Due to the large expected turnout, the Section committee would welcome several volunteers to assist in the presentation. Your duties would be simple but important. Please call your section Chairman if you are available.

The Centre is located near the Union Station and St. Andrew's subway stops, as well as the King streetcar. Nearby parking is available, though not of the free variety. Check in at the security kiosk and proceed to the Atrium upon arrival.

Make plans now for what is sure to be a most interesting evening!

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AES Last Month's Meeting Review

HiFi Sound Reinforcement and White Radio: A Community Affair

by John D Fourdraine

On 16 NOV 93 the AES Toronto Section hosted the combination of a tour of White Radio, and a lecture by Community President and Chief Engineer Bruce Howze. Pizza, beverages and GO transit pickup were available to the members and guests, (approx. 80), compliments of White Radio.

After an introduction by AES Chairman Tom Shevlin and White Radio President/Owner David Martin, he and National Audio Manager Doug Stimpson led us through the offices, repair shop, Enforcer P.A. workshop, and 55,000 sq. ft. of warehouse piled high with Community, Bogen, Telex, Belden, etcetera product. Many questions were answered, and it became clear that efficient and economical buying, stocking and selling is best left to experts, and that White Radio is very active in the high-quality sound field.

Community Professional Sound Systems' Bruce Howze then gave a fascinating lecture, starting with his early 60's experiences in concert sound reinforcement, using heavy, bulky and fragile movie theater equipment. This led to his philosophy of optimizing everything and his first product in 1969, a low-compression horn design, to reduce the well-known distortion inherently generated in a horn throat.

A thorough review of the design mathematics followed, illustrating why a low-compression wide- throat short-flare design has less distortion than the omnipresent alternative. Simply: air is nonlinear because the limit of compression is infinite, and the limit of rarefaction is only one atmosphere (a vacuum) ; therefore, anything which lowers compression in a high power horn design will reduce distortion.

Community horn designs have less than 3 to 1 compression (diaphragm area vs. throat area) compared to the usual 10 to 1. Some designs approach 1 to 1! Compression reduction (by itself) is easy to implement, but obtaining high efficiency is then a problem, for loudness and low dynamic compression require an efficient design, avoiding thermal complications, and thus a high acoustic output. A larger magnet structure is needed, for example.

By optimizing everything, a high-power, low-distortion, wide-band loudspeaker then evolves naturally into : a sub-woofer which can really pump air, a low-midrange driver which covers this crucial region seamlessly, and a tweeter which is then small enough to go to 18KHz, with smooth response.

Community addressed all those concerns, resulting in the state-of-the-art M4 midrange driver: 200-2500Hz, 200 W RMS, 110 dB out/1W input, excursion 0.125" p-p. This via a 4.5 inch voicecoil on a 6.5" cone/dome of aluminum/urethane sandwich construction, capable of supporting a man, which weighs the same as a standard 8" medium power loudspeaker cone; a sample was passed around.

Another example: the M200, 2" VC, 75W RMS, 400-4000Hz driver. Fringe benefits include: No need for a phasing plug, thus room for larger excursions; the diaphragm seals the magnet structure at the front; ferrofluid can be employed as needed. Further optimization includes precise time-alignment of drivers on a rigid fiberglass horn/baffle structure, as in the RS series loudspeakers, which makes tight specs on horizontal and vertical dispersion possible. This, in turn, permits proper arraying with minimized phasing interference. Size and weight are also minimized in the RS series.

Many dozens of audience questions were answered by Mr. Howze throughout his lecture, with his design philosophy evident: very direct, clear and efficient answers. The audience got quite involved in the subject matter, for loudspeakers are where "the rubber hits the road" and are still the weakest link in a high performance sound chain.

Multi-driver horns with manifolding, and voice-alarm systems were discussed, e.g. Community makes a 70% efficiency horn design, which can project intelligible speech for miles, albeit at high distortion and narrow bandwidth. Manifolding adds extra throat lengths, thus distortion, to gain redundancy. Many slides were shown of Community array installations in churches, stadia, and concert halls, with a thorough question and answer discussion of each, such as cluster vs. distributed systems.

After the lecture, we had a demonstration in the warehouse, with one RS 220 (200 Watt) loudspeaker, and its system controller, via a 600 W. RMS amplifier. It was difficult to make the very loud, very clear speech distort at a 200 ft. distance, demonstrating the (controller) protection action.

An enjoyable and very enlightening time was had by all, and we thank Devy Breda for setting-up this meeting, the management and staff of White Radio for the tour, refreshments and services, and Mr. Bruce Howze for travelling here from Chester, Pa., and his excellent lecture.

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AES A Survey of the Opinions of Members of the Toronto Section AES Audio Community

Toronto has one of the largest and most dynamic sections of the AES. In order to continue, and improve the AES at the local level, we would like your responses to a few questions:

1) Do you attend AES monthly meetings? Sometimes Always Never

2) Do you attend the AES Yearly conventions? Sometimes Always Never

3) Do you read the AES journal? Sometimes Always Never

4) Do you read the monthly Newsletter? (Hello?) Sometimes Always Never

5) What recent meetings have interested you?_____________________________


6) What topics would you find interesting for section Meetings?

Equipment presentations Very Somewhat Not Interested

Digital Technical Discussions Very Somewhat Not Interested

Recording Technics Very Somewhat Not Interested

Factory Tours Very Somewhat Not Interested

Installation Tours Very Somewhat Not Interested

Career planning, Discussions Very Somewhat Not Interested

Analog Technical Discussions Very Somewhat Not Interested



7) What topics would you find interesting for future Newsletters?

Equipment announcements Very Somewhat Not Interested

Technical Discussions Very Somewhat Not Interested

Recording Hints & Tips Very Somewhat Not Interested

Classified Advertising Very Somewhat Not Interested

What members are up to Very Somewhat Not Interested



Personal information

Area of interest:

Recording, Sound Reinforcement, Consumer Electronics, Education, Research & Development, Acoustics, Other_______________________________________________________________

If you have any comments, criticisms, please use this time to direct it to us. Please Fax results to 416 569-3122

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Logo Copyright 1993, Audio Engineering Society Toronto Section Bulletin

Articles may be used with the Author's Permission. Contact the Bulletin Editor: earlm@hookup.net

Editor: Earl McCluskie Assistant Editor: Anne Reynolds Layout Editor: Lee White

The Bulletin is prepared in print by Lee White, and on Horizon and the Internet by Earl McCluskie.