Designer:

Dan Marx

Project Category:

Tower Speakers

Project Level:

Intermediate

Project Time:

20+ Hours

Project Cost:

$100-$500

Project Description:

This is a 4-way, 7-driver tower speaker (WWMMTMM), using all Dayton Audio drivers. Currently being used in a small home/garage theater setup, but also sounds great in 2-channel stereo mode. Incorporates a 3D-printed interchangeable mid/tweeter baffle which allows the speaker to be easily modified or updated with different drivers as the years go by.

Design Goals:

Build a massive multi-driver tower speaker for home theater and 2-channel use where a subwoofer is optional. Targeting a neutral in-room response using a completely passive crossover. In-room correction to be handled by the AVR as required. Incorporate some 3D printed parts just for fun.

Driver Selection:

Driver selection came about purely by accident when I ran across 2 pairs of DA175-8 7″ aluminum cone woofers and 2 pairs of ND90-8 full-range drivers at my local Goodwill. Drivers were in mint condition and being sold for a song. So I bought all 8 drivers with a plan to build something cool with them one day, though at the time I didn’t know what. I ended up adding a pair of DSA215-8 woofers and an ND20FB-4 soft dome tweeter to make these huge 4-way tower speakers. Maybe an unusual driver combination but it actually worked out great.

Enclosure Design:

The enclosure is basically 3 enclosures in one. The ND90’s share about 2 liters in a sealed enclosure inside the enclosure for the DA175’s which is about 9 liters, all which sit inside a ported enclosure of about 72 liters for the two DSA215’s. Wood is 3/4″ MDF with the sides finished in 1/4″ Birch ply. The ports are rear-firing to leave space on the front for all 7 drivers. The enclosure is 49.25×11.5×14.5 (HWD) and weighs about 100 pounds. The mid/tweeter are mounted to a 3D printed baffle which can be removed from the main speaker as needed. This allowed me to rear-mount the ND90’s and flush-mount the ND20FB-4 tweeters
perfectly with a simple 3D print. This piece can be designed to house other mid/tweeter combos, allowing options to change up the overall design down the road. One of my favorite parts about this speaker.

Crossover Design:

The crossover was designed real-time with measurements of each driver in the finished enclosure in-room at 1M using REW. Final crossover is shown here and made of poly caps, iron core and air core inductors, resistors and electrolytic caps (for the really big values). All crossover slopes are 12 dB/octave except for the 8″ woofers which ended up being 18 dB/octave. Crossover frequencies are about 200 Hz, 900 Hz and 2.6 kHz. Response is generally flat from 30 Hz to 20 kHz on axis. Speakers sound best with no toe-in.

Enclosure Assembly:

This was a fun enclosure to build. I made all the cuts based on a cut-sheet I had made so assembly was just gluing all the pieces in their respective locations. I used 18 gauge brad nails and my nail gun to hold it all together along with the wood glue. There’s some bracing in the larger cabinet, but the two smaller internal enclosures are braced just by design of having them nested in each other. I used plenty of acoustic foam damping material, in addition to pink fiberglass, poly-fil and some cotton batting. The sides of the enclosures are 1/4 Birch ply and stained Early American. The front top and back are spray-paint black and the entire enclosure is finished in a satin Polyacrylic. The driver holes are back-chamfered and were all cut using a Jasper Circle Jig. Best product ever BTW. In all, spent quite a bit of time cutting, assembling, sanding and finishing these speakers, since for me this is one of the most fun parts of DIY speakers.

Tips & Tricks:

N/A

Conclusion:

Speakers turned out better than I could have hoped. It’s a bit of an unusual driver combination, but with the crossover kind of matching each driver to its sweet spot, I really can’t complain with how it sounds. I’ve mostly been listening to just 2-channel audio with them but they also sound great with movies too. They’ve got great bass, clear mids, and sparkly highs. Really enjoying them as my main system for now.

About the Designer:

I’ve been designing and building speakers since I was kid and Parts Express has been on this journey with me every step of the way. Thanks Parts Express! I have lots of other speaker projects on my web site at www.danmarx.org.

Project Parts List: