Design and Construction
The XLS340's are a moderately tall, thin column array of drivers adaptable to floor or wall mounting with an optional in-wall mounting kit also available. The cabinets are made of extruded aluminum and are equipped with mountings for screws to attach, including floor bases or wall mounting brackets. The cabinets also are internally braced to further increase cabinet rigidity. Included with the bases are both flat caster and cone floor supports allowing for placement in either hard floored or carpeted rooms. With the base installed, the total weight of each speaker is a substantial 69 pounds. Both the base and the cap appear to be constructed of MDF and covered with what the users manual describes as a "thermal vacuum formed durable surface in a textured black finish"; sounds like a rather elaborate euphemism for vinyl to me.
Use of extruded aluminum cabinets has several advantages. The cabinets are a thin profile design with the intent of wall mounting the XLS340's alongside flat panel TV displays as an option. Using aluminum with this constraint allows for thinner cabinet walls to maximize internal cabinet volume for bass response, and yet still be stiff enough to minimize cabinet vibration modes. Also, in consideration of placement near a TV, all of the drivers have shielded motor structures for use near all TV types.
Enclosures are a sealed design consisting of a five tweeter array and a 6 ½" midrange driver mounted at the top of the cabinet below the tweeter array, and dual 8" woofers mounted towards the bottom. The tweeter array is a soft dome textile design, while the midrange and bass drivers appear to be polypropylene cones, but the product documentation does not specify. McIntosh uses the same midrange driver and tweeter array for all the speakers in the XLS line. The goal here is to voice match all the speakers for flexibility when selecting between models for use in multi channel applications.
McIntosh states that multiple drivers were used to increase the power handling capabilities of the speakers. Precision crossovers are said to provide even frequency response with +-2dB specified in the product literature. The crossover network also features an automatic, solid state protection device in the event of an over load.
The tweeters used in the XLS340's are described as a Bessel Function Tweeter Array that McIntosh says allows each driver in the array to operate at lower individual power but still perform as a point source with broad dispersion characteristics with lower distortion. On the back of the cabinet, above the speaker terminals, is a pair of jumpers to optimize the phase relationship of the array for left, center, and right channel applications; presumably this is how the Bessel function is utilized as there is little by way of explanation in the product documentation. Also, the array is said to be insensitive to horizontal or vertical alignment allowing placement flexibility without compromising sound quality.
Another design feature cited by McIntosh is the patented LD/HP motor structure used for midrange and bass drivers: U.S. patent number 5,151,943 : "Low Distortion Dynamic Loudspeaker. The voice coil pole has aluminum shorting rings at each end that are said to extend the linear operating range of the magnetic field which increases the linear excursion capabilities of the drivers, reducing distortion by 10dB. McIntosh also points out the added benefit of increased heat dissipation in the design that in turn, increases the power handling capabilities of the drivers. It is interesting to note, I could not find any information on McIntosh's web site that could lead me to the actual patent, but I did find it on the site of Roger Russell, former Director of Acoustic Research at McIntosh Laboratory, on a page for the vintage XR250 speaker system , the product for which the patent was originally applied. It is also interesting to note that this web site reveals the considerable history of the products and personnel who have made McIntosh what it is today, little of which is available on the company site.
Inside, the cabinets are filled with a treated cotton damping material on all sides. The crossover network is mounted on the inside face of the MDF baffle between the midrange and woofers. Drivers feature cast baskets and magnet covers with 18 gage internal wiring.
The cabinets are internally braced using wooden dowels attached at midpoint of the front baffle coupled to the back of the aluminum enclosures at several locations.
