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JX92S SYSTEMS
A feature of the JX92S is its 'designer' tailored polar response. The axial response above 2kHz exhibits a linear rise. The response at 30 degrees off-axis shows a complementary fall. The power response, therefore, is substantially level. If the loudspeakers are positioned so that the axes cross well in front of the listening area, this achieves remarkable stereo imagery.
The JX92S is highly adaptable to a very wide range of enclosure designs, from elaborate, horn-loaded cabinets to simple, ceramic pots. Whilst it is not feasible to detail all the possible options, the following guidelines will assist the home constructor in achieving a system which is simple to construct but superior to the majority of commercially-built loudspeakers using conventional units.
The LINKS page details other designs available on the web, although we should stress that we have not heard most of these.
3 litre IB enclosure
The smallest 'full range' system using the JX92S. A closed box, 15cm sides all round, constructed of 18mm MDF and completely filled with acoustic wadding is all that is required to make an excellent stand-alone mini monitor. It will provide a remarkably balanced sound and can be either free-standing or wall mounted.
Where a full bass extension is required the 3 litre system should be augumented by a matching, passive bass system using a first order roll off centred at 112Hz (e.g. a series 9mH inductor). The JX92S system should continue to handle the full frequency range, with no bass roll off circuit required.
8 litre reflex enclosure
For many applications a more traditional design may be preferred. This offers an outstanding performance for its size and offers an ideal entry level system for the smaller room. The enclosure should be lined with acoustic wadding to a depth of 30-40mm, keeping well clear of the vent.
The internal volume is 8 litres, which can be built as an internal size of (HxWxD) 30 x 15 x 18cm. The vent should be 3cm diameter x 11cm long.
If configured as a closed box system, completely fill the interior with acoustic wadding.
VTL transmission line enclosure
The VTL elicits the ultimate low frequency performance from the JORDAN JX92S full range drive unit and provides a superior standard of sound quality to many larger, conventional multi-way systems. This has been carefully designed to offer the positive qualities of the TL whilst maintaining an elegant and domestic-friendly appearance. The broad shape enhances the sound and makes it easy to place against a wall. The system is capable of operating from 45Hz to 20kHz.
The only acoustic wadding necessary with this enclosure is a piece of felt or foam, lining the rear wall of the driver cavity. A slot should be cut in the felt to match the hole in the rear of the JX92S magnet assembly. No wadding is required in the line itself, although some constructors have adjusted the sound to their own taste by placing a small amount of wadding in the vent opening.
A PDF of the VTL design is now available via this link. An alternative, bass reflex version of this cabinet can also be built and full details can be downloaded here.
Frequency compensation
Due to the excellent frequency range, efficiency and low distortion of the JX92S, the bass performance in small enclosures can be enhanced by the use of a simple passive network in series with the driver, comprising a serier resistor 'R' with an inductor 'L'. Values for different box volumes are given below.
The circuit will further enhance both the phase and impedence characteristics. There will be an efficiency loss of 3 - 4dB but since the initial driver efficiency is 88dB, this is not too serious.
|
vol |
3 litres |
8 litres |
VTL |
|
R |
4.7 ohms |
4.0 ohms |
4.0 ohms |
|
L |
1mH |
1.5mH |
2mH |