Home > 2-way, Tower/Floor Standing > Introducing the 2-WMT BY: DJ Puuri

Introducing the 2-WMT BY: DJ Puuri


2-WMT Design Objetives

  • Under $800
  • 2-way studio monitor for critical listening
  • Largest of bandwidth as possible
  • Low Harmonic Distortion

Key Design Features

  • Eton 25 SD1 textile dome tweeter
  • Tang Band W6 1721 6.5″ Underhung Midbass Drivers
  • Low crossover point of 1500Hz allowing for exceptional clarity in vocal consonant range
  • Vented tower design allowing for extended low frequency performance
  • Durable red mahogany/matte black finish

Technical Specs

  1. Frequency Coverage 55Hz-14K +/- 4dB
  2. Max SPL 83dB SPL with 20dB Headroom
  3. f3=55Hz f10=20,000Hz

Description

The 2-WMT is a 2-way studio monitor tower. The design of the 2-WMT makes it ideal for critical listening at an affordable price. A vented tower design allows for extended low frequency coverage.

Overall Design Goal

The objective of this project was to design and construct a 2-way speaker system. This system would serve as a studio monitor. In order to adequately serve as a studio monitor this system should provide the listener with a few key features.

1. A bandwidth coverage of as close to (20Hz-20K) as possible

2. The frequency response should be as flat as possible across bandwidth

3. Low harmonic distortion

Key Technology

Cabinet Construction

The cabinet for the 2-WMT is a combination of 3/4” 11ply birch plywood and 3/4” MDF. This combination was instituted for two specific purposes. The plywood had proven beneficial acoustically in past designs. The MDF would allow for the distinct look the finished cabinet displays. The cabinet features a triple layer front baffle. The outer two layers are MDF while the inner layer is 11ply Birch. This was done with the intention of having an interior of all 11ply birch. The rear of the enclosure is double layers. The inner most layer once again is 11ply birch. The outer baffle and rear of cabinet are MDF this allows for the sleek matte black finish. The rear of the cabinet is also designed so that it can be removed. This allows for access to all system components. To battle resonance inner bracing was installed every 16” from the bottom of the cabinet connecting to each side panel. This allows for the use of a single layer on each side.
Diffraction issues where accounted for in the cabinet design. The front baffle includes a 3/8” round over on both edges. While both the tweeter and woofer are flush mounted to the baffle.
Being as the woofer features a underhung design the inner two layers of the baffle have been carefully treated. They have been rounded over inside the woofer mounting hole. This insures full linear excursion of the woofer. With sound waves being free to move off the rear of the cone. The cabinet features a durable red mahogany finish on sides and top with the baffle, base, and rear being matte black.

Driver Characteristics

The Eton 25 SD1 tweeter was chosen for its smooth frequency response and low frequency extension. This would allow for a crossover point of 1500Hz. My max SPL requirement of 83 dB SPL at one meter is accomplished with this tweeter.

The Tang Band W6 1721 6.5″ woofer was chosen for a number of reasons. These features all allow for low frequency extension. This woofer has a linear excursion of 8mm, this is almost double that of most 6.5″ woofers. The narrow design of the cabinet along with the triple layer baffle made using the W6 wise. It features a underhung motor design. This would allow it to operate smoothly in a relatively compact space.

Cross-over

A cross over point of 1500Hz was established so that it would be bellow the vocal consonant range. (2K-5K) In order to make the two drivers work together in this system, The tweeter was roll off with a 1st order butterworth at 1500Hz with a 8dB pad on it. The woofer was rolled off at 1000Hz with a 3rd order butterworth. A 10dB baffle step circuit was design and implemented at 1140 Hz. This was placed prior the low pass circuit on the woofer. The woofer exhibited a bit of a bump from 500Hz to 1200K. The baffle step circuit smoothed this out nicely. The overall crossover design allows for a +/- 4dB difference from 55Hz to 14K. With all parts being purchased for just over $100.

Other

A port tuning of 60Hz with a 2″ wide and 4″ long port was established thru use of a port tuning calculator. This was adjusted during testing to around 50HZ. The final port was 2″ wide by 6″ long. This allows the frequencies down to 20Hz to be present. This system along with some acoustic treatment allows for a very full bandwidth. Which is quite incredible given the use of single 6.5″ woofer in each cabinet.

Creative Commons License
2-WMT by Duane(DJ) Puuri is licensed under a Creative Commons Attribution 3.0 United States License.
Based on a work at dipuuri.wordpress.com.
Permissions beyond the scope of this license may be available at http://dipuuri.wordpress.com/wp-admin/post-new.php?post_type=page.

Design Documents

  • Design Proposal
  • Drafting
  • Testing Report
  • System Tests
  • Full System Frequency ResponseFull System Harmonic DistortionFull System Step ResponseFull System Phase ResponseFull System Off Axis Response (Purple to Green=0,15,30,45 degrees)Full System Cross Over Response Woofer and Tweeter Frequency Response With SummationTweeter Performance


    Tweeter Frequency Response
    Tweeter Harmonic Distortion
    Tweeter Step Response
    Tweeter Minimum Phase Response
    Tweeter Off Axis Response (Purple to Green=0,15,30,45 degrees)

    Woofer Performance


    Woofer Frequency Response
    Woofer Harmonic Distortion
    Woofer Step Response
    Woofer Minimum Phase Response
    Woofer Off Axis Response (Purple to Green=0,15,30,45 degrees)
    Other Tests Of Interest


    Impedance

    Left Right Difference

    Port Tuning (Blue calculated port 2"D 4"L, Green port installed 2"D 6"L)

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