Note how the QLS, on the left side of this photo, has a vertical line of tweeters next to a similarly placed line of midrange drivers. (Just for future discussions on the upcoming PS Audio speakers based on Nudell's Magnum Opus design also note the small woofer above the bigger one—the first implementation of Arnie's midbass coupler which will be one of two centerpieces of our new design). Now, compare that to the 4.5 with its three vertical EMITs (Electro Magnetic Induction Tweeter) and line of 4 EMIM (Electro Magnetic Induction Midrange) planar midranges. These form a quasi-line source for the midrange and appear to be the basis of a line source attempt for the tweeters—yet that would be only partially correct.
The tweeter array form Infinity's first (to my knowledge) implementation of a progressive crossover: a line source moving to a point source. At low frequencies, all three tweeters are operating together to match the top of the midrange line source. As the music goes up in frequency the outer two pair progressively turn off leaving only the single middle "point source" tweeter for the high frequencies. Thus, the 4.5 combined a quasi-line source midrange with a progressive crossover point source. The advantages of this are a far less abrupt transition from line source to point source.
More tomorrow.
Quasi line source
by Paul McGowan
In yesterday's post, I told you about the QLS, Infinity's first line source loudspeaker. As a reminder, line source loudspeakers, though rare because of the expense of all the required driver elements, are fundamentally different radiators than point sources and—because thankfully many of my readers work hard to keep me accurate as well as precise—I should point out there's no such things as a true point source (an infinitely small radiating source) and very few true line sources (like the Infinity IRS and Genesis One).
Following the '76 introduction of the QLS, itself not a full-height line source but the closest thing Infinity had ever attempted, Arnie and company launched what few people remember: a quasi line source called the 4.5. Here's a picture (from the website David's Audio) of the 4.5 and the QLS together.
Note how the QLS, on the left side of this photo, has a vertical line of tweeters next to a similarly placed line of midrange drivers. (Just for future discussions on the upcoming PS Audio speakers based on Nudell's Magnum Opus design also note the small woofer above the bigger one—the first implementation of Arnie's midbass coupler which will be one of two centerpieces of our new design). Now, compare that to the 4.5 with its three vertical EMITs (Electro Magnetic Induction Tweeter) and line of 4 EMIM (Electro Magnetic Induction Midrange) planar midranges. These form a quasi-line source for the midrange and appear to be the basis of a line source attempt for the tweeters—yet that would be only partially correct.
The tweeter array form Infinity's first (to my knowledge) implementation of a progressive crossover: a line source moving to a point source. At low frequencies, all three tweeters are operating together to match the top of the midrange line source. As the music goes up in frequency the outer two pair progressively turn off leaving only the single middle "point source" tweeter for the high frequencies. Thus, the 4.5 combined a quasi-line source midrange with a progressive crossover point source. The advantages of this are a far less abrupt transition from line source to point source.
More tomorrow.
Note how the QLS, on the left side of this photo, has a vertical line of tweeters next to a similarly placed line of midrange drivers. (Just for future discussions on the upcoming PS Audio speakers based on Nudell's Magnum Opus design also note the small woofer above the bigger one—the first implementation of Arnie's midbass coupler which will be one of two centerpieces of our new design). Now, compare that to the 4.5 with its three vertical EMITs (Electro Magnetic Induction Tweeter) and line of 4 EMIM (Electro Magnetic Induction Midrange) planar midranges. These form a quasi-line source for the midrange and appear to be the basis of a line source attempt for the tweeters—yet that would be only partially correct.
The tweeter array form Infinity's first (to my knowledge) implementation of a progressive crossover: a line source moving to a point source. At low frequencies, all three tweeters are operating together to match the top of the midrange line source. As the music goes up in frequency the outer two pair progressively turn off leaving only the single middle "point source" tweeter for the high frequencies. Thus, the 4.5 combined a quasi-line source midrange with a progressive crossover point source. The advantages of this are a far less abrupt transition from line source to point source.
More tomorrow.
Paul McGowan
Founder & CEO
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Table of Contents – Issue 211
It’s safe to say that every Copper reader grew up with Radio Shack, especially if you’ve ever burned your fingers on a soldering iron. Now, every Radio Shack catalog ever...
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Table of Contents – Issue 211
It’s safe to say that every Copper reader grew up with Radio Shack, especially if you’ve ever burned your fingers on a soldering iron. Now, every Radio Shack catalog ever published can be accessed on the website, www.RadioShackCatalogs.com. A sister site, www.alliedcatalogs.com, features catalogs from Allied Radio going back to 1929. Both sites offer a wealth of additional material including advertisements, vintage TV commercials and much more. They’re incredible treasure troves of audio history.
The music world has lost two songwriting legends with the passing of Kris Kristofferson (88) and JD Souther (78). Kristofferson wrote iconic songs including “Help Me Make it Through the Night,” “Sunday Morning Coming Down,” Me and Bobbie McGee,” and also had a successful acting career. JD Souther struck gold with his “You’re Only Lonely,” and penned many hits for the Eagles and others.
In this issue: B. Jan Montana says the Titanic’s musicians knew…about life and its meaning. Adrian Wu has a report on the Hong Kong High-End Audio Visual Show. Wayne Robins has a conversation with Perla Batalla about her album, A Letter to Leonard Cohen: To a Friend. Batalla sang in Cohen’s band for years and knew him well. Rich Isaacs has the latest installment in his series on test records and demo discs. I talk with singer/songwriter extraordinaire James Lee Stanley about his new album, The Day Today, and review the Hyeseon Hong Jazz Orchestra’s wonderful new Things Will Pass album, with an interview from the composer. Paul McGowan continues his look back on 50 years of PS Audio. Ray Chelstowski offers a tribute to the late JD Souther and interviews the masterful blues guitarist/singer Kenny Wayne Shepherd.
Harris Fogel has thoughts on quality, style, and class, in audio and elsewhere. We cover the latest release from Octave Records, The Art of Hi-Fi, Volume 06: Guitars. Rudy Radelic covers The Vinyl Beat and new reissues from Black Sabbath, Idris Muhammad, John Lee Hooker, War, and more. I continue my series on playing in a rock band with advice on getting mentally prepared for a gig. PMA magazine designs the ultimate listening chair. Ken Kessler keeps spinning reel-to-reel tapes. PS Audio earns positive reviews from Hi-Fi News and Alpha Audio. We conclude the issue with potent portables, playlist priorities, and calavera.
Contributors to This Issue:
Ray Chelstowski, Frank Doris, Harris Fogel, Rich Isaacs, Ken Kessler, Paul McGowan, B. Jan Montana, Olivier Meunier-Plante, Rudy Radelic, Wayne Robins, James Schrimpf, Adrian Wu, Peter Xeni.Logo Design:
Susan Schwartz-Christian, from a concept by Bob D’AmicoEditor:
Frank DorisPublisher:
Paul McGowanAdvertising Sales:
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