Product was successfully added to your shopping cart.

You have no items in your shopping cart.

Helix Ribbon MTM

Quick Overview

High end 7" MTM.

* This kit ships for free *


Availability: In stock


From the designer:   These speakers have very flat response and I think they will be very popular. You can make an entire home theater system with these speakers. They have an elegant crossover for textbook roll-offs and a nice summed response.

The 7" hexcore woofers are very easy to work with and had even less break up peak than the manufacturing sheet indicated. With only two parts I get baffle step compensation and a beautiful knee and roll-off. The crossover is LR4 at 2.2 kHz. Very nice. The motor, frame, and cone, are almost identical to the ***** brand.  The fountek ribbon is exceptionally flat, shows no real diffraction at all due to the horn-loading, and can cross at around 2.5 kHz.


Product Notes: 

The Helix Ribbon MTM makes for a great full range monitor style speaker for those that love the sound of ribbon tweeters. It uses a custom high end woofer with a 3 layer cone. The middle layer is a hexagon matrix similar to a honeycomb that gets 'sandwiched' between the two other layers to make for a strong light weight cone. I'll upload some more photos soon. I was able to get a smaller batch of these made at first to see how people liked them, but the price shown on woofers might have to go up a bit when they're made again. The list price is supposed to be much higher. That may or may not change the price of the kit later. 



Product Highlights:

  • Waveguide loaded ribbon tweeter.
  • High end woofers with 3 layer sandwiched hexagon matrix.
  • Smooth and detailed sound.
  • Timbre matched to the single woofer version (coming soon).


Minimum order is 2 speakers: If you ordered one in the past and need one for a center, please contact me. Kits are sold as full kits, sorry no substitutions or subtractions. Don't forget binding posts, terminal cups, or speaker spikes if you need them because they can be shipped for free with any kit or flat pack purchase.

Shipping Note: Most speaker kits currently ship for free, but flat packs normally do not.  We try to get your order packaged and shipped in 5-8 days depending on how many orders have come in.  Please read the 'Frequently Asked Questions' section for more information.

  1. My favorite build so far. review by Aaron on 2/11/2018

    As soon as Erich mentioned on the AVS forum that these were coming I knew they'd be my next speaker. I've built Jeff Bagby's Denham and Quark speakers along with about 6 other kits from other designers over the past 5 years. They've all been nice and I usually enjoy them for a while then gift them to my friends, family, or coworkers because I just like building and listening to different speakers. But these are going to stick around in my living room a bit longer than the others.

    I've heard Fountek ribbons before, but not this particular model. It's at least as good as their other models, but something stands out to me that I can't put my finger on, maybe because it's horn loaded I don't know. The woofers are interesting looking and when tilted the right way you can make out the honeycomb outlines that are used in between the two layers of what I'm guessing are carbon fiber or kevlar. The crossover was straight forward and pretty easy to assemble. Eric said an assembled crossover option would be available, but I've done enough to know the ins and outs of soldering parts together correctly and didn't want to wait.

    I did not order the flat pack because I enjoy woodworking. Parts fit the front baffle perfectly and the hardest part of the cabinet build was the port holes. I recommend precutting them on some thin wood as a trial before cutting them on your back panel. After assembling the cabinet I tried some fluffed up denim insulation glued to the rear wall along and a decent handful of polyfill behind each woofer. I fluffed it up and would consider it a light fill in the upper and lower section of the cabinet. I didn't add any polyfill behind the tweeter or around the ports and my braces keep the polyfill from moving into the middle of the cabinet.

    Sound quality is quite high on these. To my ears these are the nicest sounding DIY speakers I've built yet. Smooth midrange, good bass response, and something special about the ribbon tweeter that just keeps me listening. Jeff and DIY Sound Group have a winner here. One recommendation if I can, please consider a rotated tweeter version for a dual woofer horizontal set up in case someone was interested in a center channel down the road.

Write Your Own Review

How do you rate this product? *

  1 star 2 stars 3 stars 4 stars 5 stars


Speaker Kit Information


  Model:      The Helix MTM
  Designer:      Jeff Bagby
  Frequency Response:      40hz - 20khz (+/-3db)
  Power Range:      10 - 150 watts
  Sensitivity:      91db - 2.83v/1m
  Impedance:      4 Ohm
  Tweeter:      Fountek NeoCD3.5H
  Midrange:      N/A
  Woofer:      Denovo 7" Hexcore woofers
  Enclosure Type:      Ported
  Dimensions:      9.5" W x 23.5" H x 13" D
  Kit weight (no cabinet):      N/A
  Assembled weight:      Varies

Price Break Down:

2 - 7" Denovo Hexcore woofers: $165.10
1 - Fountek NeoCD3.5H ribbon tweeter: $64.80
1 - Set of crossover parts: $30.35
2 - 2" adjustable ports: $6.36
1 - 3/4" thick CNC cut front baffle:  $12
1 - Set of screws and gaskets:  $1.50

Packaging Material: $3.00

Paypal Fee: $8.49

Retail Cost: $291.60

Discount Cost: $280.00 and shipped for free.

Please read the 'About Us' section for more information on pricing structure and quality parts used.

Specific Helix MTM Assembly Notes:

Your enclosure should be built with 3/4" thick material with two horizontal "window pane" style braces to the dimensions listed.  It is recommended that you lightly stuff your enclosure with polyfill withough blocking the ports.


Recommended Tools and Supplies:

  • Quality wood glue like TiteBond.
  • At least 2 clamps 24" wide or bigger.  
  • Soldering Iron and solder unless there is an optional assembled crossover for your kit.
  • Wire cutters
  • Screwdriver
  • Drill to predrill all screw holes.
  • Sanding block or power sander.
  • About 8' of speaker wire to connect your woofers and tweeter to the crossover board.


General Tips:

    Crossover Assembly: 

  • VERY IMPORTANT - Inductors are the parts that look like small rolls of copper wire. Notice that the two ends of wire are silver and have been 'tinned' with solder. Those are the parts of the inductor that you should be soldering to, so don't cut it off to get to the copper colored portion.  Inductors should not be installed directly next to each other on your board.
  • None of the crossover parts have a positive or negative side so it doesn't matter which way they are facing when you assemble your crossover. 16-18 gauge wire is thick enough to use for your crossover or to go from your crossover board to the woofer or tweeter.
  • Your crossover can be assembled on a thin piece of MDF or pegboard if the kit doesn't come with a circuit board.
  • It doesn't matter where you put the crossover inside your speaker.  You could mount it on the outside if you wanted to.  
  • Normally you wire red wires to positive and black wires to negative.  If (and only if) your crossover schemtaic has a note saying 'Inverted Polarity', that means you need to connect the negative from the crossover to the positive on the tweeter and positive from the crossover to the negative on the tweeter.  This is only done on some tweeters, not woofers.
  • Click Here for a good assembly video by Matt Grant.


     Screws and Gaskets:

  • Predrill all screw holes with a bit that's slightly smaller than your screws to prevent the wood from splitting.  Most screws are #8 panhead and you can use a 7/64" or 1/8" drill bit.  Overnight Sensations use a #6 panhead so you can use a 3/32" bit.
  • VERY IMPORTANT:  Protect your woofer or tweeter when installing screws because you don't want the screwdriver to slip and puncture one of your components....that will ruin your day!  Consider putting your free hand next to the screw to cover up the edge of the woofer or tweeter.
  • If your kit comes with gasket tape, it should be applied to the back of the waveguide. Peel the paper off the back to expose the sticky side and slowly work it around the perimeter on the back side of the part.  Some woofers will need gasket tape as well.


     Stuffing or Lining the Speaker Cabinet:

  • If your speaker or subwoofer is a sealed cabinet, most designers recommend that you lightly fill the inside with polyfill (pillow stuffing).  If you don't have polyfill, then you can line the walls with 1" - 1.5" thick light weight open cell foam (like acoustic foam) or fiberglass insulation.  You can also use 2-3" recyled denim insulation that can be bought at Home Depot.
  • It's okay to cover up your crossover with the polyfill, insulation, or foam.
  • If you're using a ported enclosure you should lightly fill the cabinet with polyfill and be sure not to block the ports.  If you do not have polyfill then line the walls with 1" - 1.5" thick open cell foam (like acoustic foam), 2" - 3" of denim insulation, or 2" - 3" thick poly batting.
  • Some of the speaker designers like to lines the walls of their ported enclosures with a 1" - 1.5" acoustic foam, and then lightly fill the remainder of the cabinet with polyfill.  If this is a required method, it will be listed at the top of the page under 'Assembly Notes'.


Links to Build Threads for this Speaker:

Frequently Asked Questions:

* Does the baffle come with roundovers?  Answer:  No.  If you really need roundovers, please send me an email and I can try to put them on the edges for you.

Also Purchased