Project Time: 8-20 Hours
Project Complexity: Beginner
Project Cost: $100-$500

Project Description
4 driver, 3-way floor standing tower speaker

Design Goals
The goal of this project was to build a pair of speakers that would produce sub woofer-like bass for use with my vintage 1978 integrated amplifier.

Driver Selection
• Dayton Audio DC25T-8 1″ Titanium Dome Tweeter Part # 275-045 – 8 ohm, frequency response 3000Hz to 20,000Hz, sensitivity 93dB
• Dayton Audio RS125-8 5″ Reference Woofer Part # 295-353 – 8 ohm mid-woofer w/aluminum cone, sensitivity 87dB, frequency response 65Hz to 5400Hz
• Closeout model 930064 8″ Heavy Duty Woofer with Rubber Surround Part # 299-363 – 4 ohm, 80 watts each, frequency response 35Hz to 1500Hz, extended frame for greater linear excursion

Enclosure Design
• ¾” five ply cherry vinear plywood left over from a previous project.
• Cabinet size OD of 40”H x 11”W x 14”D.
• Heavily braced interior cabinet
• Midrange and tweeter are isolated from the woofers
• Woofer area volume (minus all bracing) ~1.58 cu ft.
• High density polyfill acoustic dampening material
• Rear mounted flared port tuned to ~38hz (2½”ID x 8½”L cut to 4½” L , Part # 260-478)
• Gold plated banana binding posts (Square Speaker Terminal Cup 4″, Part # 260-284)
• Pre-built crossover – 625Hz and 5000Hz
• All connections to binding posts, crossover and drivers are soldered

Enclosure Assembly
Construction – For several years I’ve had some ¾” five ply cherry vinear plywood left over from a previous shelving project. The price was right and the pieces were already partially cut making them easier for me to handle than a full 4’ x 8’ sheet. I choose a cabinet size of 40”H x 11”W x 14”D. I began by cutting the pieces to the approximate sizes using the radial arm saw. Then I finished them on the table saw.
I purchased some metal corner brackets and installed 4 of them in the back corners of each of the cabinets to help hold the units together and square while I continued to assemble them. Using Liquid Nails, I glued battens to all the inner seems to hold, seal and increase the cabinet strength. I cut and installed a shelf creating a sealed upper compartment for the mid and tweeter speakers. I located the shelf about 1/3rd the length of the cabinet. The volume of this compartment is such that it does not need to be ported for the midrange. A large brace was added in the woofer compartment connecting the cabinet side walls to further reduce vibrations. I also cut small triangular pieces and glued them in all of the front facing corners where the front baffle would be attached. This provided additional strength to the enclosure and more surface area for gluing the front baffle. Next, I determine the layout of the drivers on the front baffle. I made thin card board templates for each speaker based on the size of each driver. The actual cutouts were smaller and these dimensions can be found on the specification drawings from the driver manufacturer. Three and four inch hole saws were used on a drill press for cutting the midrange and tweeter driver holes. A jigsaw was used to cut the woofer holes which were 7 1/8” diameter.

Crossover and wiring terminal location – I determined the best location to mount the crossover would be under the internal shelf that isolates the midrange and tweeter from the woofers. Removing the upper woofer would provide access to it if necessary in the future. The placement of the crossover, lead to locating the wiring terminal near the center of the rear panel. This worked out well since the only place to mount the port tube was likely going to be on the backside near the bottom of the enclosure.

Tuning Port location – I decided to locate the port on the back of the cabinet. Matt at PE calculated the port size. I provided him with the woofer cabinet volume and the part number of the woofers. Using Bass Box Pro and the woofer specs, Matt determined a 2.5” x 4.5” flared port would provide a tuning frequency of 38 hertz.

Wood finish – I wanted the cabinets to be black but the wood grain to remain visible, so I didn’t want to use paint. So, after much consideration, I chose Minwax Polyshades black satin. This worked pretty well. One coat was used on the cabinets and 2 coats on the front baffles. A clear coat of Minwax polyurethane sealer was applied a few days later.
Polyfill acoustic dampening material – The polyfill was stapled to the inside walls of the cabinet and to the back of the driver baffle.

Crossover and driver installation and wiring – Standard 16 gauge speaker wire was soldered to each of the driver connections on the crossover. A small hole was drilled for routing the midrange and tweeter wires to the upper compartment. Each driver connection was soldered to ensure no lose connections later on. Prior to mounting the drivers, speaker gasket tape was applied to the woofers to make an airtight seal. Gasket tape was pre-applied to the midrange and tweeters from the factory. The drivers were then carefully positioned on each of the front baffles and pilot holes drilled for the screws. A hand screw driver was used to install the screws. More control of screw pressure is achieved by hand tightening vs using an electric drill. One slip with a drill driver and a woofer or the finish on the baffle can be ruined.

Final assembly – Liquid Nails was used for gluing the baffles, side walls, back wall and all other support pieces. Ten large clamps were used to hold the units while the glue hardened.

Crossover Design
Prices on pre-built crossovers range considerably as well as the quality of the components that go in to building them. I wanted high quality components, such as metalized polypropylene capacitors in the upper frequency ranges and good quality inductors. I considered building my own but with being my first scratch build, I decided to purchase a pre-built crossover.

After extensive searching, I purchased from eBay a pair of pre-built crossovers with cutoff points of ~625Hz and ~5000Hz. These crossovers use high quality components. They have 8 ohm mid and tweeter impedance and switchable 4 or 8 ohm woofer impedance. This option allows for series wiring of a pair of 4 ohm woofers or parallel wiring for a pair of 8 ohm woofers. The crossovers have individual speaker fuse protection as well as top of the line inductor coils and metal film capacitors specifically designed for audio use. Standard 16 gauge speaker wire was soldered from the crossover to each of the driver connections.
• 3-way, 2nd order (12dB) reverse polarity
• 625 Hz/ 5000 Hz
• 8 ohm tweeter/8 ohm midrange/8 ohm woofer (w/option for 4 ohm capability)
• band pass gain ~ 2.5 dB
• spread ~3 octaves
• all precision metalized film capacitors in the midrange, tweeter and low pass signal paths
• utilizes both air and iron core copper wound inductors
• all driver paths are individually fused

Conclusion
I was very happy with the final product. Being my first build, I feel I could improve on the cabinet construction appearance which I will on my next pair of towers. However, I feel I met my goal of building a speaker with sub woofer-like bass when used with my vintage integrated amplifier. The sound quality and bass produced greatly exceeded my expectations. On the construction end, the enclosures are very solid. The black finish matches my other home theater components. Currently the speakers are connected to to a Russound two input, 6 speaker out speaker switch so I can run them through the vintage amp and my AV receiver.

About the Designer
Since my teenage years, I have been interested in electronics, specifically stereo equipment, speakers, amps, etc. I still use my 1978 integrated amplifier as my primary audio source for playing CDs and vinyl. I like the simplicity of the vintage equipment along with the build quality, real aluminum knobs, aluminum face plates, the feel of quality. The pursuit of better quality is what drove me to try building a set of speakers. Thank you Parts Express for your support in this hobby.

Project Parts List