KLH Model Five Speaker Test

Tall, to the limit narrowed floorstanders are not going out of fashion, but they are losing their undivided power. Born as an elegant alternative to oversized hi-fi cabinets, now they themselves are falling victim to the cyclical development of fashion – and the classic forms of acoustics of the 70s are returning, causing bright nostalgia even for those who were not yet born in those golden vinyl days.

It is not surprising that the American brand KLH, founded in the middle of the last century, decided to pamper today’s music lovers with the revival of acoustics that gained crazy popularity with their grandparents.

Closed box discoverers

KLH Corporation was founded in 1957 in Cambridge, Massachusetts. One of its founding fathers was sound engineer and businessman Henry Kloss. By that time, he had already worked at Acoustic Research together with the inventor Edgar Vilchur and participated in the development of speakers with a closed acoustic design.

Surprisingly, it is a fact: engineers learned how to correctly use a closed volume to build speakers later than they came up with a phase inverter. For a long time it was not possible to make friends with a dynamic head with a blind box, since the elasticity of the air ate up a significant part of the energy of the diffuser.

It was possible to reduce the pressure gradient by drastically increasing the volume of the case, but there was little point in inventing another hefty cabinet. By the way, the word “closet” is by no means a metaphor: high-end (for those times) speakers were really huge, and some people really slammed the speakers right into the wardrobe doors.

Vilchur was the first to guess that the air spring should not be pacified, but used for the benefit of sound. Therefore, he made the suspension and the centering washer of the speaker as soft and plastic as possible. By itself, such a driver practically could not work, but in a closed box, its membrane acquired the necessary support.

In addition, it turned out that as a return spring, air is much better than any rubber or paper corrugation. It does not age or wear out, but the main thing is that it has a high linearity of dynamic characteristics. To further increase the damping, it remained to fill the case with sound-absorbing material, and voila – in 1954, the “acoustic suspension” design was born.

It was he who was chosen by Henry Kloss for the flagship speakers of his KLH brand. Why? Yes, because as an engineer and a businessman all rolled into one, he was well aware that listeners are in dire need of a radical increase in bass quality with relatively compact acoustics. True, a well-damped driver could not boast of high sensitivity, but by the 60s, amplifiers had already managed to pump up muscles, and they had made significant progress in the fight against distortion.

Linen and walnut

The original KLH Model Five speakers were produced from 1968 to 1977, and in those years managed to become one of the best-selling speakers in the United States. Over time, new favorites appeared on the hi-fi scene, and KLH miraculously did not sink into oblivion, becoming part of the Japanese Kyocera. But in the end, the company was lucky: in 2017 it was acquired by another veteran of the American audio business, David Kelly.

He moved the company’s headquarters to Indiana, where he started a storm of work on a completely new line of speakers. Among them there were many narrow bass-reflex towers familiar to us, but since last year a remake of the famous Model Five has occupied a special place in the catalog.

Externally, the acoustics have not changed much. The cabinets are 66 cm high and 35 cm wide, assembled from 19 mm ultra-rigid MDF boards and finished with natural veneer. Choose from West African mahogany or darker and more contrasting walnut. The speakers are hidden behind old-school fabric grills, adorned 54 years ago with a die-cast zinc badge with the KLH logo.

Linen fabric in different finishes differs in texture, however, if desired, the desired screen can be ordered separately. On the front panel, the grills are fixed with magnetic latches, and the owners of the original version had to tinker with Velcro.

Author’s variation

I have no doubt that all the technical documentation for the original “fives” has been preserved, but the developers had the common sense not to make an exact copy of the speakers half a century ago. Indeed, over these decades, dynamic heads have reached a completely different level of development and production, and it would be strange not to take advantage of this.

For example, the original tweeter diaphragm was a 1.75-inch paper cone, the baskets of the woofer and two midranges were pressed from thin and soft sheet metal, and their magnets were, by today’s standards, very low-power.

The modern version of the KLH Model Five received an HF driver with an inch aluminum diaphragm on a rubber surround. Diffusers MF and LF remained paper, although the speakers themselves, of course, are different. There is not much information on them, but they got cast aluminum baskets and powerful ferrite magnets for sure. And the upgrade also made it possible to get by with one 4-inch midrange instead of two.

Taking into account the new heads, the crossover was also redesigned. Now it uses core coils made of modern ferromagnets and Mylar capacitors.

More than alive

The speakers were tested in conjunction with the AMC XIA100se amplifier. Its output stages are built on MOSFET transistors and the plasticity of sound evokes associations with lamps. Meanwhile, this integrated circuit does not take up power – 2 x 140 W (4 Ohms), which will not be superfluous for acoustics with a sensitivity of 87.5 dB in a free field. The source was a TEAC NT-505 network player, speaker cables – Analysis-Plus Oval 12.

The sound signature of the “acoustic suspension” made itself felt literally from the first bars. Constantly listening to bass reflex designs, you simply cease to realize how multifaceted, embossed and tonally adjusted the bass range can be. The low-quality 10-inch woofer, suspended, in fact, on 50 liters of air, additionally “thickened” by a volumetric sound absorber, is envyingly energetic and really very linear.

This is understandable, because the bass is not tightened to the resonant frequency of the phase inverter and does not fall behind it from a cliff with a steepness of 24 dB per octave. The closed box has its own specifics. The absence of a resonator tube provides a smoother decay (12 dB / oct.), However, due to the difficulty of lowering the resonant frequency, it usually starts a little earlier. Model Five’s frequency response extends from 42 Hz to 20 kHz with 3 dB unevenness, and reaches 32 Hz at the level of -10 dB.

Particularly impressive were the low frequencies on Sia’s Color the Small One. In some places, it contains several heterogeneous bass parts at once, and they are written juicy and from the heart. The loudspeakers played them tight and varied, with a fast attack, but without excessive pressure on the higher-frequency part of the phonogram.

I deliberately started the story about the sound of deliberately old-school acoustics with a modern progressive album that has nothing to do with either jazz or rock and roll. I really wanted to emphasize that in the modern musical context, with its hypertrophied basses, the acoustic suspension is even more relevant than 50 years ago.