Ion - DIY 2-Way TMM Tower Speaker Project
Adam McCall  
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Ion - DIY 2-Way TMM Tower Loudspeaker Project
The Ion is a wonderful 2-Way tower loudspeaker that has been designed to produce a very warm and natural sound. It achieves this by using a pair of Audax HM170CO woofer-midranges drivers with a TangBand 25-1372SC tweeter in an TMM configuration and using a 3rd order crossover point at 4000Hz. The Audax HM170CO woofers produce very warm natural tones up through the upper midrange. With the TangBand 25-1372SC tweeter the highs are crystal clear, detailed but far from harsh. Bass response is excellent too! The Ion speaker is a very challenging build but it comes with a huge payoff! These have quickly become my favorite loudspeakers.
General Tower Loudspeaker Information:
- Tang Band 25-1372SC 1" Tweeter
- Inverted Titanium Dome
- Audax HM170CO 6" Woven Carbon Fiber Mid-Woofers
- 3rd Order X-over at 4000Hz w/ Impedance Correction
- 4ohm Nominal Impedance
- 128 Watts RMS
- Freq Response 60Hz-20kHz
- Sensitivity ~93 dB / 1W / 1m
- 37.5" x 8.5" x 11.5"
- 60lbs each est
- Solid MDF and Oak Construction
- 1.5" Wall Thickness w/ Oak Side Panels
- Textured Graphite Finish/Stained Hardwood
Enclosure and Crossover Design - Ion 2-Way TMM Tower Loudspeaker
A bass reflex (ported cabinet) enclosure is used for the tower loudspeakers. The overall size of the speaker box enclosure is 37.5" x 8.5" x 11.5" (953 x 216 x 292 mm) and each finished loudspeaker weighs about 60 lbs (27 kg). The enclosure drawing for the Ion speakers is shown below (click drawing to enlarge).
Figure 1: Enclosure Drawing - Ion 2-Way TMM Tower Loudspeaker
To come up with the enclosure design for the speaker I used Bass Box Pro Version 6 to simulate the frequency response. The X-Over Pro 3 passive network design program was used to design the crossover, impedance equalization network and L-pad circuits. The frequency response and impedance plots generated for the enclosure and crossover are shown in Figure 2.
Figure 2: Simulated Frequency Response and Impedance Graphs - Ion 2-Way TMM Tower Loudspeaker
A 2-Way passive crossover network using a 3rd order Butterworth filter at 4kHz is used along with an impedance correction network. The crossover schematic is shown in Figure 3.
Figure 3: Crossover Schematic - Ion 2-Way TMM Tower Loudspeaker
Crossover Components - Ion 2-Way TMM Tower Loudspeaker
C1 = 3.9 uF, Polypropylene, internal resistance 0.00736 ohms
C2 = 10 uF, Polypropylene, internal resistance 0.0051 ohms
C3 = 15 uF, Polypropylene, internal resistance 0.00435 ohms
L1 = 0.15 mH, Air Core (18AWG), internal resistance 0.16 ohms
L2 = 0.3 mH, Air Core (18AWG), internal resistance 0.26 ohms
L3 = 0.1 mH, Air Core (18AWG), internal resistance 0.13 ohms
Rp1 = 1 ohms, 10W, non-inductive
Rp2 = 33 ohms, 10W, non-inductive
Rp3 = 1 ohms, 10W, non-inductive
Rp4 = 27 ohms, 10W, non-inductive
Req = 3.3 ohms, 10W, non-inductive
Ce = 12 uF, Polypropylene
A photograph of the assembled 2-Way passive crossover network for the Ion Loudspeaker is shown below.
Photograph 1: Assembled 2-Way Speaker Crossover Network
Construction Notes - Ion 2-Way TMM Tower Loudspeakers
The Ion 2-Way TMM Tower Loudspeaker will be a challenging build. The best approach is to take your time and be patient. DON'T get wrapped up in all the super precise dimensions; they are impossible I know, but have been provided for reference. I suggest to start off by cutting all of the raw material for the baffles/outside panels and braces but a bit longer than needed. Sandwich your panels together to achieve the noted 1.5" thickness; while keeping in mind to leave a 1" clearance on both the far outside edges. [Note: 1" = 1-inch = 25.4 mm] I suggest setting yourself up a small jig on a work table and cut out a few 1" wide pieces to ensure you're good and square. And then cut the 22.5 degree angle and achieve your needed length that way. The angled corner pieces do the same for, but do not fully assemble by adding the piece that is furthest to the inside of the cabinet till after the 22.5 degree angle has been cut.
Photograph 2: Cut Panels and Bracing for Ion Loudspeaker Enclosures
Regarding the port; it is two 1.5" holes in the rear through 3" of MDF. Assemble yourself a 1.5" thick piece which can accommodate the port holes and attached to the rear baffle and then drill out the port holes.
Photograph 3: Ion Speaker Box Port
Make a total of 4 braces, but make them a bit long. You now want to assemble all the outside panels using PL400 adhesive and strap clamps (using tie downs is ok too, I did). Insert the braces at this point too; trim shorter if needed (but keep them equal length to ensure squareness). Allow the adhesive to set. Now take measurement for your side panels and build them. Depending on your choice of lumber you may want to choose a 1/2" thick hardwood and back it with 1/4" MDF. There is then a 3/4" MDF rib that runs the full length for support. Pre-drill your holes for the side panels into the cabinet! Following these steps will help eliminate some headache and ensure a desirable end result. Below are some photos of the construction process.
Photograph 4: Speaker Box Assembly
The speaker box has been assembled and is primed using Kilz Oil Based Primer before being painted.
Photograph 5: Apply Primer to Speaker Boxes
After the primer has dried, the MDF panels are painted using cans of Rust-Oleum Textured Spray Paint
Photograph 6: Painted Ion Speaker Boxes
Materials List and Costs - Ion 2-Way TMM Tower Loudspeakers
A list of the parts and materials used for this project and corresponding cost (US dollars) is provided in the tables below. Table 1 shows the speaker parts ordered from Parts Express (USA).
| Parts Express # | Description | Qty | Price (each) | Cost |
|---|---|---|---|---|
|
264-858
240-725 100-072 100-074 091-1247 255-206 255-218 255-202 260-540 260-317 |
TB 25-1372SC 1" Titanium Tweeter 3/8" Toe Spike Set 16awg Black Primary Wire 100ft 16awg Red Primary Wire 100ft BPA-38SN Binding Post Satin Jantzen .15mH Air Core Inductor Jantzen .30mH Air Core Inductor Jantzen .10mH Air Core Inductor Gasketing Tape 1/8"x3/8"x50' Acousta-Stuff Polyfill 1lb bag |
2
2 1 1 2 2 2 2 1 2 |
$95.80
$4.25 $14.70 $14.70 $8.48 $4.26 $5.60 $3.80 $6.49 $10.80 |
$191.60
$8.50 $14.70 $14.70 $16.96 $8.52 $11.20 $7.60 $6.49 $21.60 |
Table 1: Speaker Parts from Parts Express
The remaining speaker parts including the Audax HM170C0 6.5" driver were ordered from Madisound and are shown below in Table 2.
| Madisound # | Description | Qty | Price (each) | Cost |
|---|---|---|---|---|
|
MATRIX
MOX33 MOX27 MOX3.3 MOX1 MOX3.9 PX15 PX10 PX12 HM170C0 OX10PAN1 OX6OVAL3/4 OX8PAN1 |
Circuit Board Matrix
Mundorf 33ohm MOX Resistor Mundorf 27ohm MOX Resistor Mundorf 3.3ohm MOX Resistor Mundorf 1.0ohm MOX Resistor ClarityCap 3.9uF PX Poly Cap ClarityCap 15uF PX Poly Cap ClarityCap 10uF PX Poly Cap ClarityCap 12uF PX Poly Cap Audax HM170C0 6.5" Woofer #10 1" Phillips Pan Head #6 3/4" Phillips Oval Head #8 1" Phillips Pan Head |
2
2 2 2 4 2 2 2 2 4 16 14 100 |
$7.00
$2.50 $2.50 $2.50 $2.50 $4.10 $10.50 $6.70 $8.30 $99.10 $0.08 $0.06 $0.07 |
$14.00
$5.00 $5.00 $5.00 $10.00 $8.20 $21.00 $13.40 $16.60 $396.40 $1.28 $0.84 $7.00 |
Table 2: Speaker Parts from Madisound
Materials for the speaker cabinets were purchased from Home Depot and are listed in Table 3. You will be able to find the materials for the speaker cabinets at most home improvement stores.
| Description | Qty | Price (each) | Cost |
|---|---|---|---|
|
3/4" x48" x 96" MDF Sheet
1/4" x 48" x 24" MDF Sheet 1/2" x 48" x 24" SandePly Kilz Oil Based Primer 1 qt Rust-Oleum Textured Spray Paint 16 oz Wood Glue 1" Drywall Screws - 1lb Wood Filler PL400 Adhesive |
1
2 2 1 8 1 1 1 2 |
$23.00
$6.00 $10.00 $6.48 $4.98 $5.49 $6.00 $10.00 $4.98 |
$23.00
$12.00 $20.00 $6.48 $39.84 $5.49 $6.00 $10.00 $9.96 |
Table 3: Cabinet Materials from Home Depot
Speaker Parts: $800.59 (Parts Express and Madisound)
Cabinets Materials: $132.77 (Home Depot)
Total Cost: $933.36 US
Photograph 7: Finished Ion Tower Speaker
Summary - Ion 2-Way TMM Tower Loudspeakers
I really love these Ion Speakers! They have met and exceeded my expectations. The speakers play very warm and clear. They have a very full and open midrange all the way down. The highs are very clear, articulate and direct. They have a great presence down in my office; curious to see how they do in the living room. I didn't find the midrange spike shown on the simulations (Figure 2) to be of any real concern; it certainly isn't annoying or painful to listen to and doesn't show up in the measured response. In the crossover shown the tweeter has been padded by 1.6dB and the woofer has a 2.64dB L-Pad. This setup sounded best for my room. The measured in-room response of the Ion speakers is shown below (click response plot to enlarge). The large peaks and dips that appear below about 500Hz are the "resonant room modes" which are caused by standing waves.
Figure 4: Measured RTA Response of Ion TMM Tower Loudspeaker
For more information about myself and photos of other speakers I have built, check out my website at AM Audio. Also, be sure to check out my other speaker projects, the 1.618 HiVi 3-way Tower Loudspeakers and matching 1.618 HiVi Center Channel Speaker and HiVi SP10 DIY Subwoofer build.