SEAS Excel Bifrost Kit - Pair - Parts Only

SEAS Excel Bifrost Kit - Pair - Parts Only
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Price: $1,425.00


  • Buy 10 - 10,000 and get an additional 10 % off
Manufacturer: Seas Excel
Product ID : bifrost
Weight: 25.00 lbs
Manufacturer: Seas Excel
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Seas Excel Bifrost Kit - Pair - Parts Only
Price shown is for a PAIR

Bifrost Cabinets from Taylor SpeakersThe Seas Excel Bifrost is a  top of the line 2-way speaker kit utilizing the T29CF-002 “Crescendo” Tweeters and W18NX-001 7” Woofers. These drivers represent the highest end offerings from Seas of Norway. Detailed information on this kit design can be found on the Seas website.

BiFrost Datasheet PDF
BiFrost Enclosure PDF
BiFrost Cabinet Parts PDF

The T29CF-002, known as the “Crescendo”, is the flagship tweeter in the Seas Excel lineup. This Ultra High End 29mm soft dome tweeter employs a wide SONOMEX surround and high efficiency HEXADYM magnet system. Building on the success of the famous “Millennium” tweeter, Seas has once again raised the bar with the “Crescendo”. In addition to world class performance, the Nextel painted machined aluminum face plate with chrome plated brass center ring makes this one of the most visually appealing tweeters we know of.

The W18NX-001 is the 7” paper cone mid/bass woofer of the Seas Excel line. A Nextel coating is applied to the front side of the cone to provide added stiffness, while a special coating is also applied to the rear of the cone to reduce cone resonances. With such features as Adaptive Surround, copper clad aluminum voice coil, and heavy copper rings mounted both above and below the T-shaped pole piece, this driver is defined by its excellent transient response and very low distortion. The chrome plated solid copper phase plug and Nextel coated cone are a perfect cosmetic match to the “Crescendo” tweeter.

We are offering the Bifrost kit with assembled premium crossovers. The low pass circuit uses Goertz Copper Foil 14awg inductors in series with the woofer. The high pass circuit uses a Mundorf Supreme Silver/Oil  capacitor in series with the tweeter. This component selection was carefully chosen to best match the drivers and design of  this system. High quality resistors, caps and air core inductors are used in the remaining circuits. All Bifrost crossovers come assembled on a Matrix Double circuit board and are bi-wire/bi-amp capable. Alternate series capacitors for the tweeter (high pass) circuit are available on the drop down menu above.

If you are interested in high quality custom cabinets for this design, Madisound would like to recommend Lee Taylor & Co. Contact Lee to discuss veneer options and pricing. We feel his cabinets for this design look stunning, are very well constructed, and attractively priced. Floor standing tower and stand mount monitor versions are available.

Crossover Schematic:

The Bifrost Kit includes:

Optional Bifrost Accessories Package includes:

You may select this accessories package along with kit purchase, or buy your parts individually. Kit pricing reflects a 10% discount to all drivers, crossovers, and optional accessories.

Crossover options:

  • Goertz Copper Foil 14awg inductors & Clarity ESA Cap
  • Goertz Copper Foil 14awg inductors & Mundorf Supreme Cap
  • Goertz Copper Foil 14awg inductors & Mundorf Supreme Silver/Gold/Oil Cap
  • Goertz Copper Foil 14awg inductors & Mundorf Supreme Silver/Oil Cap*

*Default premium crossover for the Bifrost kit. Pictured above.

Enclosure design:

The woofer T/S parameters are found in the datasheet. This data was entered into the driver editor in the LspCAD software from IJdata. Using the “Table Lookup Optimizer” with 0.3ohms entered as added series resistance (dc resistance of inductor in series with the woofer) the QB3 alignment suggests a box volume of about 14 liters. We have instead chosen to make the box a bit larger than this and aim for an EBS alignment. The simulation shows the frequency response in a cabinet volume of 18 liters, with a port tuning at 42 Hz.


The measurements are done in a free-field anechoic chamber at 1 meter on tweeter axis with an input voltage of 2.83 volts.

The green curve shows the system response with the tweeter connected with reversed polarity. The cancellation confirms that the drivers are in phase around the crossover region.
The system sensitivity is considerably lower then what is found in the two driver’s datasheets. This is intentional, and necessary to compensate for the so called “baffle step / spreading loss”.  For further information see:
Average sensitivity is 84dB SPL @ 1 meter with an input voltage of 2.83 volts. The measured axial frequency response variation is +/- 2dB between 71 Hz and 22 kHz. Minimum impedance is 7.5 ohm at 180 Hz.

The horizontal off-axis plots show a smooth response for the axial, as well as 20 and 40 degree angles.  

Distortion at 90 dB SPL / 1 meter. Blue: 2nd harmonic - Red: 3rd harmonic.

High quality components results in a system with low distortion. 

For users with simulation tools that wish to make adjustments to the crossover, or use the data for other purposes, we have made the raw driver response in the Bifrost cabinet available for download here.

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Product Reviews

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Reviewed by bdbender4
bdbender4 bought "SEAS Excel Bifrost Kit - Pair - Parts Only" on our website
11/15/2016 - 09:26:59 AM
SEAS Bifrost follow-up
After listening to these speakers for a week or two, I experimented with the port tuning, as per the original designer's notes. I built these speakers in pre-made 26l cabinets, pre-finished and with curved sides, with the correct baffle width. I had noted that Troels Gravesen used a slightly larger cabinet for this woofer in one of his designs, so I looked at his port tuning information as well.

Madisound supplied a very long port tube, and flares for both ends. I ended up trimming this down to an effective length of 3.5", and a flare at the outer end only (due to internal cabinet restrictions). This really opened up the sound in the upper bass, which had sounded a bit thin and restricted with the long tube.

Personally, I believe that high-excursion speakers and fancy capacitors both do break in, and I think these are in that process. At any rate, these speakers are clear, detailed, not harsh at all, image well in a "field of sound out in the room" sense, and are starting to have good dynamic range at the low-to-moderate listening levels I prefer these days.
Reviewed by bdbender4
bdbender4 bought "SEAS Excel Bifrost Kit - Pair - Parts Only" on our website
10/20/2016 - 10:52:28 AM
Excellent speaker, top-notch drivers

In the past several years I have built three Madisound kits, all two-ways.

First was the (now discontinued) Eton S-7, and I did a review for that at the time. Very clear sound, the damped magnesium tweeter was the best I had heard at that time. My ex-wife now has those, something smaller to replace some older Snells I gave her. (My stepson now has the Snells.)

More recently I built the SEAS A-26, mostly out of nostalgia since I am old enough to remember the original Dynaco A-25s, although I had KLHs at the time. These have that room-filling sound that a large full-range driver gives, and they work well with a single-ended tube amp that I have. Not really "hi-fi", but I was very impressed with the SEAS 1.5" fabric tweeter. That in turn encouraged me to try another fancy SEAS fabric dome.

I just finished this kit, and it is still breaking in, but these drivers are worth the expense. They replaced Focal 826s, which are very good speakers (I upgraded the crossover capacitors), but the difference in clarity and ambience was immediately apparent. I don't have a fancy vocabulary to describe sound, but using a Wyred4Sound amp and a small self-equalizing Velodyne sub this is a great-sounding system. Should quell the kit-building jones for quite a while!