MT Series


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Handmade in USA
Current lead times are 10-15 business days to machine and assemble Fi products


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The Special Edition 2021 Black FiDay MT Series of Fi subwoofers is designed to meet the needs of the serious competitor and and monster basshead.

SKU: MT Categories:

The 2021 Black FiDay special MT Series of Fi subwoofers is designed to meet the needs of the serious competitor and and monster basshead. With a massive 4″ voicecoil for increase thermal capacity, we designed the rest of the motor via FEA to optimize the proprietary US steel (water jet and machined in house at Fi when your order is placed). Using three ultra-high grade Y35 magnets, a flux flow derived back plate geometry, and a solid pole with aluminum sleeve and aluminum compression cap, there is plenty of thermal capacity in the MT Series. Our Fi designed heavy 5 spider pack coupled with our special 144 tinsel count leadwire to keep the moving assembly under control at extreme excursion levels. The reworked surround geometry on the 12″, 15″, and 18″ models optimizes cone area vs excursion yielding the most output vs excursion. The 2021 Special Edition Black FiDay MT Series is designed for competition use and monster daily driving systems requiring high linearity and extreme power handling. From a punishing low end to the subtle nuances in your favorite reference track, the Special Edition MT Series delivers!

  • Dual 1 and Dual 2 Ohm

  • Extra heavy aluminum basket

  • Wrap around gasket

  • Kraft pulp fiber reinforced cone

  • Dual layer wide foam surround

  • Standard heavy duty stitched Push or Hybrid terminals

  • 144 tinsel count leads

  • FEA optimized motor

  • Ultra Flux density design

  • 4” diameter 4 layer coil

  • Triple stack magnets

  • Five extreme 10″ spiders

  • Stage 2 Aluminum Cooling

  • Machined in house at Fi
Weight 92 lbs
Dimensions 20 × 20 × 16 in

Thiele-Small Parameters

  MT  12 MT 15 MT 18
Coils DUAL 1 | DUAL 2 DUAL 1 | DUAL 2 DUAL 1 | DUAL 2
FS 34.3 Hz | 34.3 Hz 32.2 Hz | 32.6 Hz 31.7 Hz | 32.1 Hz
RE 0.75 | 1.49 0.75 | 1.49 0.75 | 1.49
QMS 7.93 | 7.83 8.52 | 8.43 9.91 | 9.79
QES 0.36 | 0.38 0.38 | 0.40 0.45 | 0.47
QTS 0.35 | 0.37 0.37 | 0.38 0.43 | 0.45
MMS 408g | 404g 444g | 435g 516g | 503g
CMS 0.53 | 0.53 0.53 | 0.53 0.68 | 0.68
SD 480cm^2 | 480cm^2 810cm^2 | 810cm^2 1210cm^2 | 1210cm^2
VAS 17.17 l | 17.17 l 49.0 l | 49.0 l 95.4 l | 95.4 l
SPL 84.6dB | 84.4dB 88.1dB | 88.1dB 90.2dB | 90.1dB
BL 19 N/A | 26.1 N/A 19 N/A | 26.1 N/A 19 N/A | 26.1 N/A
XMAX 33mm (One Way) 33mm (One Way) 33mm (One Way)
RMS 4500W 4500W 4500W

Technical Specifications

  MT 12 MT 15 MT 18
Overall Diameter 12.500” 15.625” 18.500”
Cutout Diameter 11.125” 14.125” 16.750”
Mounting Depth 10.00” 11.00” 12.250”
Driver Displacement 0.19cuft 0.21cuft 0.26cuft
Ported Box 1.8-2.5 cuft 3-5 cuft 5-8 cuft


Subwoofers & Recones are dispatched via FedEx Ground. Small goods such as sticker packs, various apparel items are shipped via USPS. Upon dispatch of your goods, order status will be updated from “test/pack” to “shipped” which is accompanied with tracking details.

General Information

All orders are custom made to your selected options.  Each order is machined from raw steel and hand made after it is ordered.  This normally takes 10-15 business days, but due to unforseen issues it can take longer. We will note much of this directly on the individual product pages and try to update this weekly.  There are a couple of times a year that we simply can not keep up with sales and these “normal” time lines will not be in effect.  These times normally include Black FiDay and tax season.  During these times we will run batch orders per series and not individual orders.  This increases our overall efficiency, but can put your order into a later build date.  Fi will maintain reasonable communication should an item take longer than our normal 15 business days to make during our normal build seasons.  Often we will post through Facebook and Instagram our batch sequences to give all customers a better time line.  We also note for each item the current lead times (which can be longer than our normal 10-15 business days. Should an item take longer than normal, all refund policies still are in effect.

Delivery Location

Items offered on our website are only available for delivery to the verified billing addresses in the US and Canada. We also accept orders from international customers who are shipping to addresses on an individual basis.  All items will ship direct from our Las Vegas, Nevada location.

Delivery Time

An estimated delivery time will be provided to you once your order is placed. Delivery times are estimates and commence from the date of shipping, rather than the date of order. Delivery times are to be used as a guide only and are subject to the acceptance and approval of your order.  Deliveries will be made through FedEx Ground unless otherwise noted.  Delivery times in the US generally take from 1 to 5 business days depending on how far you are from our facility in Las Vegas, Nevada

Unless there are exceptional circumstances, we make every effort to fulfill your order within [15] business days of the date of your order. Business day mean Monday to Friday, except holidays.

Date of delivery may vary due to carrier shipping practices, delivery location, method of delivery, and the items ordered. Products may also be delivered in separate shipments.

Delivery Instructions

We will only ship to the customers billing address.  No exceptions.  All orders are shipped with direct signature required.  We will not ship orders without direct signature, sorry if this causes any inconvenience.  Fedex will send an email to your customer supplied email address once the order has shipped.  This normally happens after 6PM PST on the day it is picked up.

Shipping Costs

Shipping costs are based on the weight of your order and the delivery method. To find out how much your order will cost, simple add the items you would like to purchase to your cart, and proceed to the checkout page. Once at the checkout screen, shipping charges will be displayed.

Additional shipping charges may apply to remote areas or for large or heavy items. You will be advised of any charges on the checkout page.  

All shipping rates are pulled directly from our FedEx rate chart.  We do not charge extra over our actual cost from FedEx.  Fi also pays from its own pocket for DSR (Direct Signature Required) and Insurance for any order over $500.

Damaged Items in Transport

If there is any damage to the packaging on delivery, contact us immediately.  A claim will need to be filed with Fedex.  In contacting us please have your order number (it has been emailed to you and is on the shipping label) and your tracking number (emailed to you and on the shipping label) ready to expedite the claims policy.


If you have any questions about the delivery and shipment or your order, please contact us.

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