Great Vintage Loudspeakers

Great Plains Audio is pleased to announce the most significant advance in the famous 604-series of loudspeakers since the advent of the constantdirectivity horn: The GPA Model 604-8H-II Two-Way Loudspeaker System.
The Model 604-8H-II is a two-way loudspeaker that is designed to provide unsurpassed reproduction of the audio spectrum over a wide frequency range with extremely high efficiency. When connected to an appropriate crossover unit and installed in a proper enclosure, the GPA Model 604-8H-II Two-Way Loudspeaker System reproduces the entire spectrum of human hearing with naturalness, extremely accurate phasing, and excellent stereo imaging.

A True Point-Source Speaker

Actually two loudspeakers in one, the Model 604-8H-II is comprised of an extremely efficient low-frequency loudspeaker and a high-frequency compression driver/horn assembly that are coaxially mounted together. This method of magnet construction is what makes the Model 604-8H-II sound so good - since both it’s low and high frequency signals emanate from the same vertical AND horizontal planes, extreme accuracy of reproduction and spatial separation are attained.

Digital Ready

“Digital Ready” is a phrase heard often in the audio world. Part of what makes digital records so impressive is the amount of low-frequency content they contain. Most loudspeaker designers, in an attempt to make it possible for their products to be able to “handle” the demands of digital audio, utilize large, heavy voice coils, inarticulate suspension systems, and cones that weigh far too much to be able to reproduce the middle of the audio spectrum accurately. In addition, this approach results in loudspeakers that require large amounts of audio power so that they may operate. Not only that, but the majority of designs of that type have voice coils that “overhang” outside of the magnetic field. The benefits of constructing a loudspeaker in this manner are many, the most notable ones being a significant loss of control of cone movement, which reduces the ability of the loudspeaker to articulate sounds accurately.
The GPA Model 604-8H-II Two-Way Loudspeaker System does not require design and construction techniques such as these in order for it to be able to respond to the demands of digital music and sound effects. Instead, the Model 604-8H-II utilizes a lightweight cone with a highcompliance suspension, and the low-frequency voice coil remains in the magnetic gap at all times. When combined with the largest motor structure ever used on a 604-series loudspeaker, these features allow the Great Plains Audio Model 604-8H-II to exhibit cleaner, more natural response, tighter low-frequency control, and the most accurate low-frequency sound reproduction found in any other system of its type available today.

Superior HF Reproduction

The focal point of the high-frequency section of the Model 604-8H-II is the diaphragm/voice coil assembly, the design of which is critical to accurate sound reproduction. Even though many manufacturers today try to claim they have discovered a superior method of high-frequency reproduction, Great Plains Audio has chosen a different paradigm. By utilizing only the finest, time-tested materials and manufacturing methods in the construction of it’s high-frequency section, including: (1) an all-metal aluminum dome structure; (2) a tangential compliance; and (3) a voice-coil of 1 3/4-inch edgewound copper clad aluminum ribbon. These features assure superior sound reproduction of the frequencies above crossover in the Model 604-8H-II.
In order to assure that the sounds being generated by the diaphragm leave the loudspeaker in proper phase alignment, the Model 604-8H-II uses our exclusive RADIAL-WAVE™ phasing system, which ensures maximum high frequency reproduction while maintaining proper phasing and smooth overall response to beyond 20 kHz.
When operating, the audio waves leave the high-frequency diaphragm, go through the RADIAL-WAVE™ phasing system, enter an exponential throat where they are conducted through the center of the low-frequency pole piece and into our small constant-directivity horn. Most horn designs tend to narrow their dispersion patterns as the pitch goes up. Our horn design doesn’t have this problem. It produces the same dispersion pattern throughout it’s bandwidth. The result at the listening position is a startling, nearly 3-D stereo image that exhibits superior latitude in the seating position.
These different parts of the Model 604-8H-II - the low-frequency section, the high-frequency diaphragm, the RADIAL-WAVE™ phasing system, the small constant-directivity horn, and the powerful FerriteV magnetic assemblies - all combine in the Model 604-8H-II to create a loudspeaker capable of uniform, peak-free reproduction throughout the range of human hearing, thus making it ideal as the loudspeaker of choice where natural, unadulterated sound reproduction is required.