Seas Loki MKIII Coaxial Kit - Each

Seas Loki MKIII Coaxial Kit - Each
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Price: $242.00


  • Buy 10 - 10,000 and get an additional 10 % off
Manufacturer: Seas Prestige
Product ID : loki-kit
Weight: 9.00 lbs
Manufacturer: Seas Prestige
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Seas Loki MKIII Coaxial Speaker Kit - Each

Recently updated to version III!

Seas Loki MKIII Brochure PDF

Named after the Norse god Loki, a shape shifter which corresponds well to how versatile this loudspeaker is. The Loki consists of an 18cm coaxial driver. The woofer is made with a TPX cone and the tweeter is a 25mm soft dome.
Designed by Diego Ivars and Håvard Sollien at the SEAS R&D laboratory.

The Seas Loki MKIII is a single 7" coaxial driver speaker system from the highly regarded Seas Prestige line. The driver used is the SEAS Prestige T18REX/XFC (H1353) 7" Coaxial.

Consider the Loki MKIII Kit in a stereo pair for music listening, or as a hi-end surround sound solution. Also makes a wonderful center channel.

This is the most versatile and easy to build speaker kit that we offer. With the tweeter coincidently mounted at the base of the woofer cone, the Loki provides a point source presentation. There is no traditional “sweet spot” for the listener; the soundstage is broad, and the imaging excellent. In addition, the speaker can be laid on its side without any lobing issues. 

The crossover for this system has been designed by Bjørn Magne Idland of the Seas R&D team. The updated network is less complex than the original, and specifically engineered for this Madisound speaker kit. Crossover slope is 12db/octave on both the mid/bass and tweeter. We conducted hours of listening tests between the original and updated crossover design. While we are still a fan of the original, the newer design proved more balanced in its presentation and worthy of implementaton in this generation Loki MKIII kit.

Coaxial driver Information:

Bass and midrange frequencies are carried by a PP/TPX (clear polypropylene type) cone ideally matched to a special adaptive rubber surround. This results in a very smooth frequency response from the mid woofer.

The coaxially arranged precoated fabric dome tweeter has a low resonance frequency, and integrates with the cone driver to a point source.

The cone of the woofer acts as a horn loading for the tweeter, and the chassis of the dome unit represents the throat of this horn. The tweeter is located where you would expect to see the dust cap on a traditional driver. The woofer cone moves independently around the tweeter.

Assembled Crossover Information:

The Loki MKIII kit crossovers are professionally assembled with high quality parts throughout. The tweeter section uses a ClarityCap CSA along with Mundorf MOX resistors. The woofer circuit utilizes a Sidewinder 16 AWG air core inductor. Upgrade options include Mundorf M-Cap Supreme for the tweeter, and Goertz Copper Foil 14AWG inductor for the woofer. Please inquire by email if you require a specific combination of parts that is not shown as an option above.

The crossover is symmetrical with a 2.9 kHz 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 kept at a minimum without sacrificing any of the audible performance. This is possible to achieve, because of the drivers very smooth response. The crossover is a simple 2nd order network with an L-pad on the tweeter to match the sensitivity. Together they align the phase of the drivers excellently and gives a smooth inter-driver transition. The roll-off of the drivers is steep enough to allow them to work effortlessly even at high lower levels, thus maintaining the smooth and detailed sound quality at all levels and allowing them to be as dynamic as possible.


The below measurements are taken in free field at 1 metre on tweeter axis. As seen in the figure the average sensitivity is 82dB. The black curve shows the response with the tweeter connected with opposite polarity.
The deep and symmetrical notch, when the tweeter is connected with inverse polarity, shows that the drivers are in-phase across the whole crossover region.

The off-axis response of the Loki is shown in the next picture. Here we can see that the power response is relatively smooth for the whole frequency range. The advantage with the coaxial driver is that we get a radially symmetric dispersion without the common lobing issues you get from inter driver spacing in loudspeakers with multiple drivers.

The last picture shows the 2nd and 3rd order harmonic distortion with an output of 96dB at 1m. The overall distortion is low and without any large peaks. This makes the reproduced music very clean and without colouration.

Cabinet Information:

Recommended bass reflex cabinet is 12 liters (.43 ft3) with dimensions of 8" wide x 15” tall x 11" deep. Front or rear port this enclosure with a 2" internal diameter x 6.5" long port tube. 


While creating a wonderful sound stage and imaging in an ideal setup on speaker stands, the LOKI also excels in non-traditional arrangements. We have auditioned the speaker in many unusual locations (on-wall, in ceiling, bookshelf, unevenly spaced, up in the warehouse rafters, etc) with very acceptable performance in every case. This is the most forgiving speaker for difficult locations that we have heard, so don't be afraid to get creative.

We can say without hesitation that the Loki offers audiophile performance in a small and convenient package.


  • 8 ohm impedance
  • 82 dB sensitivity w/ BSC
  • Frequency response: 46Hz (@-3dB) to 25kHz ported, 75Hz (@-3db) sealed
  • Power handling: 80W Long Term, 250W Short Term
  • Ported cabinet dimensions: 8" wide x 15” tall x 11" deep

Each Kit Includes:

The parts list below is what a typical build of this kit will require. If you are starting from scratch you should consider purchasing the optional accessories package. If you already have stock on some parts, review the parts list to make certain you have what you need.

Optional Accessories Package Includes:

  • (1) 2FLARE - Precision Flared Port Tubes - front or rear port
  • (1) DB-CUPS - gold plated binding post input cup
  • (4ft) Supra Classic 1.6 - tinned oxygen free copper internal speaker wire
  • (.1lb) Acousta-Stuf - fluff & fill behind coax driver
  • (1/2pc) Foam Sheet - cut & line internal walls
  • (1) QC110B Quick Connects - for - tweeter tab
  • (1) QC110R - for + tweeter tab
  • (5) QC205B - for + woofer, crossover & input cup tabs
  • (5) QC205R - for - woofer, crossover & input cup tabse
  • (6) OXSOCKET8X1 - mount driver to baffle
  • (4) OX6SOCKET6x3/4 - mount port flare to cabinet
  • (4) OX6OVAL3/4 - mount input cup to cabinet
  • (4) OX6PAN1/2 - mount crossover inside cabinet
  • (3ft) Foam Tape - airtight seal of driver and port flare to baffle
Optional Cabinet Includes:
  • (1) Cherry wood veneered enclosure 
  • Full accessories package as listed above 
  • Ordering with this option provides you everthing you need to make a completed speaker!

LOKI MKIII Cabinet - Front w/o Grill Cover

Rear Side of Cabinet

Cabinet w/ Grill Cover

Center Channel w/o Grill Cover

Center Channel w/ Grill Cover

Please note that this item is sold each, order as many or as few as you need.

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Product Reviews

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Reviewed by Seren2
09/27/2012 - 03:09:36 PM
Loki Kit
'Our goal was to make a small system using a Yamaha mini 20 watt receiver. We started with 4.5 inch full range pioneers from parts express, and didn't love it. Then I tried 4.5 full ranges Fostex's in the same cabinet designed for the pioneer and it was better. Super efficient but only sounded great when we cranked them up. We started over with the LOKI kit. Huge difference four times the money as the Fostex but 10 times the sound. Nice rich base, detailed highs and nice voices. The boxes are a little bigger, but nicely proportioned. We were so excited we are trying the Madisound Eton 11.2 and I think I'm going to try Thor!!! We've had great service and advice and are going to have some fun with these kits. Loki is really nice and a small size. It's really nice to have such excellent cabinet drawings and crossovers. I've built many speakers over the years but these kits are the Best!! All the engineering is done. Just plug and play.' Review by william bancroft. Posted by Madisound.