Bookshelf speaker kit SEAS IDUNN with cabinet kit, speakers and passive crossover en kit

Two-way demi column bass-reflex speaker, with 18 cm woofer and horn dome tweeter, birch plywood cabinet 18 mm thick, passive crossover.

Named after Idunn, a Norse Goddess of youth.
The Idunn consist of an 18 cm long throw woofer with a Curv cone made of woven polypropylene - U18RNX/P ,
and a 27 mm aluminium/magnesium dome with a DXT ® lens - 27TBCD/GB-DXT


Enclosure and stuffing :

The Idunn loudspeaker is based on a standard 20 litre vented cabinet. This cabinet was chosen to give people an easy start to building a loudspeaker. See PDF file for cabinet drawings. Ask your local loudspeaker dealer if he can help you obtain this, if your not thinking of building it yourself. The important thing to remember when you are building this, is to keep the baffle width and internal volume of the original enclosure. Adding braces to stiffen the cabinet is a good tip for the advanced builder to take the loudspeaker just a little bit further.

The amount of stuffng and port tuning is based on measurements and extensive listening. The cabinet is filled with 250 g of stuffing. The stuffing is distributed evenly in the box, but kept away from the port openingto allow free movement of air. This to ensure that the air flow noise stays as low as possible. The port length is 16 cm including the flanged end and the inner diameter is 5 cm. This gives a port tuning of 38 Hz providing a smooth low frequency roll-off.


Drive units :

U18RNX/P is a 18cm(6.5") High Fidelity woofer with an injection moulded metal chassis, intended for bass reflex and transmission line designs. New Curv cone, a woven polypropylene with excellent internal damping together with perfectly matched moving parts gives a smooth, extended frequency response. Large magnet system gives good transient response, and the bumped back plate together with the very long, and light weight copper clad aluminium voice coil allow for extreme coil excursion with low distortion. Bullet shaped phase plug reduces compression due to temperature variations in the voice coil, avoids resonance problems which would occur in the volume between the dust cap and the pole piece and increases the long term power handling capacity. Extremely stiff and stable injection moulded metal basket, keeps the critical components in perfect alignment. Large windows in the basket both above and below the spider reduce sound reflection, air flow noise and cavity resonance to a minimum. This driver uses Seas SpiderRing ® technology.

27TBCD/GB-DXT is a HighDefinition aluminium/magnesiumalloy dome tweeter with DXT ® lens. An optimally shaped dome and awide SONOMEX surround, both maufactured by SEAS, ensure excellent performance and consistency. The compensation magnet increases the sensitivity and reduces the magnetic stray field and allows use in close proximity to CRT screens. A fine mesh grid protects the diaphragm. Stiff and stable rear chamber with optimal acoustic damping allows the tweeter to be usedwith moderately low crossover frequencies. This revolutionary DXT ® tweeter addresses the major issues regarding directivity control in traditional loudspeaker designs. DXT ® solves several well-know issues regarding; directivity control, off-axis response, integration with midrange units and baffle diffractions.


Crossover :

The crossover is symmetrical with a 2.2kHz crossover frequency. The crossover point was chosen so that the directivity of the drivers make the overall power response extremely smooth, as can be seen in the measurements. Complexity of the crossover was held as low as possible witout sacrificing any of the audible perfomance. This is possible to achieve, because of the drivers very smooth response. On the woofer there is a simple 2nd order network, and on the tweeter there is a equally simple 3rd order network and an L-pad to trim the tweeter sensitivity. Together they align the phase of the drivers excellent and a gives a smooth interdriver transition. The rolloff of the drivers is steep enough to alow them to work effortless even at high power levels, thus maintinaing the smooth and detailed sound quality at all levels and allowing them to be as dynamic as possible.

Complementary specifications :
- Crossover cutoff frequency : 2.2 kHz @ 12 dB/octave for low-pass and 18 dB/octave for high-pass
- External dimensions: H:530mm, W:230mm, D:265mm
- Load volume : ~20 Litres