The time has come to dream up a name a new speaker design. In the past, we have enlisted your help in coming up with speaker names. Veracity, SongTower and Pharos are a few names chosen from ideas submitted in threads such as this.
We worked on this design with Jeff Bagby, a very talented designer and author of a number of software programs for speaker design. Here is a pciture of the speaker in question this time around...
The design is an open baffle midrange as you can see in this photo showing the 2" thick front baffle...
Here's another close-up...
Here is some information on the design to spark your thought process...
Technical description:
This is a very high-end three-way loudspeaker implementing relatively high sensitivity and an open-baffle design to the midrange.
One of the greatest sources of coloration in the midrange is caused by the internal reflections of the cone’s rear output off of the midrange enclosure’s rear wall and back into the cone. In many designs these reflections are handled by loading the midrange into a large sealed box stuffed with damping material, or possibly using a transmission line to capture midrange energy and direct it away from the cone. Although these methods can be successful, in this design these reflections are eliminated by removing the midrange enclosure altogether.
In dipole designs there is a cancellation that occurs at low frequencies whose wavelengths are relative to the baffle width. In the case of a dipole, equalization is usually required to raise the driver’s low end output to compensate for the cancellation. In this case however, the midrange’s operating band is primarily above the cancellation frequency, so it is simply referred to as an open-baffle midrange, rather than a dipole.
The midrange employed is a 6.5” PHL unit. The PHL is a high-end professional driver with high efficiency and high output capability, yet it has enough linear travel to remain linear through its entire operating range at high power levels keeping midrange distortion very low. As with any dipole / open baffle design there is a null in the response 90 degrees off axis to the sides of the speaker. This means there is little to no midrange energy to the sides of the speaker that can reflect back to the on-axis first arrival sound. This helps to maintain purity in the midrange that must to be experienced. The midrange’s rear radiation is much stronger than a conventional monopole mid, but if the speaker is at least a couple of feet from the wall behind it this only adds a sense of depth and openness to the presentation.
The woofer section is a traditional monopole vented box with a large 4” flared rear-mounted port. The woofer is a custom-made 12” Lambda woofer implementing a damped paper cone, large cast frame and massive motor assembly which weighs in at 27 pounds. The motor has a copper Faraday sleeve which runs the entire length of the voice coil. This sleeve significantly reduces voice coil inductance and associated distortion making this driver one of the lowest distortion 12” woofers available today, and an inductance normally associated with a 4” driver. The motor also provides the voice coil with a very long linear travel as well, which allows for rather high bass output capability. This is a woofer that can support the lower midrange with clarity and authority and at the same time provide true deep bass with high output.
The tweeter selected is a Morel MDT33; a triple-magnet 28mm dome tweeter with extremely linear on and off-axis response and very low distortion. It also possesses relatively high sensitivity for a dome tweeter. In terms of frequency response and distortion this tweeter is among the best dome tweeters ever made, and is an excellent sonic match for the midrange and woofer in this design.
Technical Specifications:
Frequency Response: 30-30kHz +/- 2 dB
Nominal Impedance: 8 ohms.
Sensitivity: 93 dB/2.83V/Meter
Crossover: 450Hz Second Order Acoustic In-Phase Linkwitz-Riley (Woofer to Midrange)
and 2.5kHz Fourth Order Acoustic In-Phase Linkwitz-Riley (Midrange to Tweeter)
The cabinet is 46 ½” H, 15” W and 12” D.
The front baffle is 2" thick and all panels are 1" thick with substantial bracing in the woofer section.
Here is a frequency response graph...
Hopefullly this is enough to get your creative juices flowing.
- Jim
