Introduction
McIntosh Acoustic Engineers have refined the line source Column Loudspeaker concept to provide superior quality midrange and high frequency sound reproduction in a full range system.
The High Fre- quency Section utilizes a patented Column Design1 with multiple four inch Midrange LD/HP2 Magnetic Circuit Design Drivers and one
inch soft dome Tweeters. Refer to figure 1. Since the audio power fed to a column is distributed among all the drivers, each driver does not have to work as hard, resulting in greater power handling capability and a dramatic reduction in distortion. The Sound Waves from the Column produce a Cylindrical Wave Front with a stable symmetrical hori- zontal sound dispersion to minimize undesirable floor and ceiling re-
flections that could detract from
astable sound im- age. Refer to figure 2.
In the illus- tration the
Loudspeaker on the left side produces a Cylindrical Wave Front and the Loudspeaker on the right side produces a conventional Spherical Wave Front.
The Low Frequency Section of the System consists of two 12 inch Woofers. They have a large magnet assembly and long
cone ex- cursions with very low levels of har- monic dis- tortion and frequency response down to 16Hz. Re- fer to fig-
1COLUMN Pat. No. 4,267,405
ure 3. The Woofer also incor- | LD/HP |
porates McIntosh’s Patented |
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LD/HP2 Magnetic Circuit De- | Conventional |
sign with shielding to greatly |
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reduce any external magnetic |
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field. Extensive investigating |
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and testing resulted in a new |
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design concept which utilizes |
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a pair of aluminum shorting |
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sleeves in the magnetic cir- | Figure 4 |
cuit. Refer to figure 4. The sleeves virtually eliminate the negative influence of the fluctuating voice coil field on the permanent magnet 
field. This results in
lower distortion due to more linear mag- netic flux in the
voice coil gap. Re-
fer to figure 5. Ad- ditional benefits are
less volume com- pression due to im- proved heat transfer
through the sleeves and a cooler operating voice coil. Both measurements, as well as critical listening, reveal ten times less distortion than previous designs. A good example of this low distortion is incredible smoothness and clarity in the reproduction of the human voice.
The Crossover Networks used in the XRT30 Loud- speaker Sys-
tem are de- signed to en- sure an even frequency re- sponse over the entire au- dible range. The Low Fre- quency Cross- over Network is a Third Or- der design uti- lizing Capaci- tors and In- ductors with high current
capacity. Refer to figure 6. There are three different types of low loss (DCR) Inductors in the network, each one cho- sen not to exhibit any core saturation even at high power
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