Bookshelf Speakers

Phase Technology Premier Collection PC-3.5 LCR Speakers


Introduction to the Phase Technology PC-3.5 Speakers and Driver Technology

This Phase Technology Premier Collection Bookshelf Speaker is a rather unique product. Most bookshelf speakers are two-way designs with a single small woofer. The advantages of a three-way design are well known as illustrated in my measured results to follow. A few bookshelves are three-way with a single small woofer. This speaker has two 6.5" woofers. Its low end can match a floor-standing with similar-sized woofers. Usually this driver deployment is found in speakers designed for in-wall applications where the vertical center channel is behind the screen.

The speaker's footprint is not much larger than a typical two-way bookshelf. The height is not much larger, so it works in any application where a floor-standing speaker is not viable. The weight is higher with the extra drivers in the box. The speaker has curved side panels, which enhance its appearance. The sides curve inwards slightly at the speaker front. The modest 7" width of the front baffle reduces diffraction effects. Phase Tech also claims the curves reduce cabinet resonance.

The design and size of this speaker makes it classified as an LCR (Left, Center, Right) speaker, although Phase Tech lists it on their website as a center channel speaker.


  • Design: Three-way, Ported
  • Drivers: One 1" Soft-Dome Tweeter, One 1.5" Soft-Dome Midrange, Two 6.5" Woofers
  • MFR: 36 Hz - 22 kHz
  • Sensitivity: 91 dB
  • Nominal Impedance: 4 Ohms
  • Dimensions: 22" H x 7.9" W x 12.3" D
  • Weight: 28 Pounds/each
  • Price $1,000/each USD
  • Finishes: Black Gloss, Natural Cherry
  • Phase Technology
  • Secrets Tags: Speakers, LCR Speakers, Bookshelf Speakers

The Phase Tech Premier Collection line comes in two finishes: cherry and high gloss black. Phase Tech reports the cherry has a natural finish and then they are coated with a satin extremely durable polyurethane coating. The high gloss black has 8 layers of hand sanded and polished clear polyurethane coating on top of black polyurethane. The high quality finish extends to the front panel, allowing the speaker to be displayed without the grill in a typical home environment. The grill is held on by magnets making it easy to remove before a listening session

The midrange and tweeter assembly rotates for vertical or horizontal (center channel) placement. I tested the assembly in its vertical deployment for both two- and three-channel deployments. You can go to the Phase Technology web site to see the assembly rotated to the center channel position. I am not showing it here to prevent confusion with regards to what deployment of the PC-3.5 was used for this review.

The history of Phase Technology has been discussed in prior Secrets reviews and is available at

Phase Technology is best known for its soft-dome driver, which is the star attraction in the PC-3.5. In 1959, Avery Fisher contracted with the founder Bill Hecht to produce speakers for Fisher. As Ken Hecht, Bill's son, tells the story, the Fisher speakers with conventional hard domes were constantly being damaged at HiFi shows as people poked at them. Avery Fisher wanted a mock up of the tweeter with a soft dome that would not be damaged at the shows. The mock-up, to Bill's surprise, actually produced sound. In 1964, the large Fisher XP-10 floor-standing speaker with a soft dome tweeter was introduced to critical acclaim. Numerous variants followed, but Fisher became more intent on putting lots of drivers in low-cost boxes limiting what Bill Hecht could produce. Hecht, not wanting to be tied to the fortunes of one company, began operating under the United Speaker Systems brand and sold OEM drivers to many companies. With the soft dome under patent protection (3,328,537), the business grew rapidly.

United Speaker Systems sells complete designs to the public under the Phase Technology brand, including the state-of-the-art active speakers called dARTS. The DSP code and the hardware are custom designed by Phase Technology, putting the company in a league with larger manufacturers of professional audio monitors. The speaker, under review here, is one step down from the dARTS system and is passive. An explanation of the name Phase Technology will become evident in the measurement section.

Figure 1 shows the midrange - tweeter module of the PC-3.5. You are looking at soft dome drivers with 48 years internal development. Placing the drivers close together reduces interference effects associated with non-coincident drivers are minimized. In turn, the speaker has good vertical radiation patterns even with the crossover between the midrange and tweeter at a high 4.5kHz. The small distance between the midrange and tweeter is possible as a result of the novel aspects of the Phase Tech driver design. There is no waveguide on the midrange (figure 1). Dome midranges normally have a waveguide to improve efficiency at the cost of wide dispersion.

Note the domes have no protection over them. To prevent damage I recommend the grill be put in place whenever the speaker is not in use.

The woofers are also of proprietary construction. The flat-piston is evident in the accompanying photos of the complete speaker at the top of the review. Figure 2 shows a side view of the solid flat piston driver. The back of the cone is a conventional cone shape, which terminates to a spider and voice coil. The cone is a solid molded material Phase Tech calls Rigid Polymer Foam (RPF). The cone is coated with glass fiber in the front and Kevlar in the conical back. Phase Technology patent (4,566,178) for the RPF driver addresses the unique assembly requirements of the Solid Piston. Most woofers are assembled by centering the voice coil from the front of the speaker before the dust cap (the dome shaped piece in the center of the cone) is glued on. Solid Piston RPF drivers do not have a dust cap or a means of getting to the voice coil from the front so Phase Technology invented a "reverse assembly process" that uses computer aided manufacturing to assemble the woofer from the rear.

Phase Tech says the complete cone is about half the weight of a conventional polypropylene cone. The alignment of the flat front positions the wave launch to start at the front baffle, which is important in the crossover to the midrange as we will see in the measurement section.

The design issue is that the three-3 dimensional structure is more complex to model than a simple cone. Reducing resonance in the cone is thus more difficult. The measurement section below appears to show the resonance of the woofer is comparable with that of a standard driver for a speaker in this price range. For additional details, a YouTube video of Ken Hecht demonstrates the driver's construction. The woofers have butyl rubber surrounds and a cast aluminum alloy baskets.

Speaker systems with high performance to price ratios are often equipped with custom house drivers. Surprisingly, one value-oriented company, well known for driver innovations, introduced a new set of speakers at CES with drivers from an external source. This is clearly not the direction in which Phase Tech will to go.