AR(Acoustic Research) AR-LST

Commentary

A speaker system designed to withstand sound reproduction under severe conditions for testing and research in the frequency range from 30 Hz to 20 kHz.
LST stands for Laboratory Standard Transducer.

The unit is the same as the one used for AR-3a.
There is a 30 cm cone woofer in the low range, four 3.8 cm domed mid-range units in the middle range, and four 2 cm domed tweeters in the high range. Each of the four mid - and high-range units is used to increase the allowable input and is connected in series and in parallel.

The network circuit is equipped with a tapped auto transformer that can control 0 to 6 dB in 1 dB steps, and each unit is connected to the auto transformer tap via a 3-circuit 6-contact selector switch to adjust the output level.
The auto / transformer also has a 5,000 μ F capacitor inserted in series to prevent unnecessary load fluctuation to the amplifier near the lower limit of the frequency band where the inductive reactance of the transformer decreases.

Position 1 of the selector switch provides a response in which the output of the tweeter increases by 2 dB relative to the output of the woofer, and the sound output gradually increases as the frequency increases.
Position 2 provides an almost flat response, while positions 3 and 4 provide a response in which the low-frequency level is 2 dB higher than the mid-range level.
In addition, positions 5 and 6 are close to the response when the AR-3a level control is in the normal position, and position 6 has a 2 dB lower response than position 5 in the level of the tweeter area.
The mid-range output level is designed to maintain a constant level so that the sound quality does not change when the switch position changes.

In the AR-LST switch positions 1 and 2, the high-frequency output of the tweeter shows a fairly high response. In the case of LST, four tweeters are used to divide the input into two parts. However, care must be taken to prevent excessive input in the ultra-high frequency range (such as fast forward or rewind of the tape recorder without reducing the volume).

Built-in protective fuse.

Model Rating

Method	3-way, 9-speaker, acoustic suspension system ・ Bookshelf type
Units Used	For low band : 30 cm cone type For Middle Area : 3.8 cm Dome Type x4 For High Pass : 2 cm Dome Type x4
Impedance	4 Ω (varies depending on the position of the selector switch)
Sound quality switching	6-Step Selectable
Allowable input	180W for 10 seconds 60W (30 seconds) 32W (Long Continuous)
Distortion Factor (at 10W input)	5% or Less (40 Hz) 2% or Less (100 Hz)
Crossover frequency	575 Hz, 5 kHz
External dimensions	Width 689x Height 508x Depth 248 mm
Weight	40.5kg