MANUFACTURER'S SPECIFICATIONS:
System Type: Three way, with vented enclosure.
Drivers: Three; one 3 1/2-in. tweeter, one 4-in. midrange, and one 10-in. woofer.
Crossover Frequencies: 1 and 4 kHz.
Control: One calibrated, rotary, tweeter-level control.
Finish: Natural wood, American walnut.
Size: 14 in. W x 13 in. D x 36 in. H.
Weight: 55 lbs.
Price: $189.95.
The Fairfax FX-350 is a three-way loudspeaker system using a 4-in. cone tweeter, a 4-in. midrange, and a 10-in. high-compliance woofer in a vented enclosure. The woofer handles the range below about 1 kHz, while the tweeter takes over above 4 kHz. This is a floor-standing model, finished in natural American walnut with a matching sculptured foam grille. The removable grille is secured with press-type fasteners to the front of the enclosure.
Speaker connection is made to well-marked 5-way connectors mounted in a recessed cavity in the rear of the cabinet. A single rotary, tweeter-contour control is placed in the same cavity and is fitted with a pointer knob to assist in balancing by means of engraved dial calibrations.
Good tactile cues are offered by this arrangement, so you can adjust the control by reaching around the back without the need to move the enclosure. This facilitates adjusting the sound to suit individual tastes.
The enclosure is sturdily built and can safely take the load of a lamp or other item which might be placed on its convenient 36-in. height. However, as with any piece of fine furniture, the wood top should be protected from possible abuse.
The Fairfax FX-350 is covered by an unconditional five year warranty against defects.
Technical Measurements
The measured impedance is shown in Fig. 1 for three positions of the contour control. The center position of the control potentiometer is referred to as "zero" on the Fairfax dial plate. This position is called center in Fig. 1. The other two positions are maximum clockwise, which gives highest tweeter level, and full counterclockwise, giving lowest tweeter level. This lowest impedance occurs at the maximum position control setting and is about six ohms.
Fig.1--Impedance for three positions of the tweeter contour control of the
Fairfax FX-350.
Since it is unlikely this position will be used, the Fairfax can be considered as an 8-ohm system based on the rest of the frequency range.
Fig. 2--Anechoic one-meter frequency response for one-watt drive and three
tweeter control positions.
Fig. 3--Anechoic one-meter phase response corrected for woofer, midrange,
and tweeter acoustic positions.
Fig. 4--Three-meter room response.
Fig. 5--Horizontal polar response for three tweeter control positions.
The woofer section shows the characteristic double peak of a vented enclosure. The lower peak occurs at 15 1/2 Hz, which is low enough to be down in the frequency range of record warp components. This suggests that a preamplifier rumble filter should be used to prevent subsonic energy from causing the speaker cone to experience large excursions which could in turn result in muddiness at high sound level should the cone go out of the linear gap region. The minimum impedance occurs at 27 Hz.
The anechoic amplitude response is shown in Fig. 2 for the same three control positions as those of Fig. 1. Dips occur at around 1.2 kHz and 4kHz for this axial pressure response.
The low bass holds up well down to below 60 Hz, then falls off at around 18 dB per octave. The alignment indicated by the impedance and pressure amplitude show that the low bass might tend to sound slightly heavy, particularly when mounted against a flat wall, due to the acoustic damping of this design. If this happens, a more balanced bass can be achieved by a conventional tone control rolling off the low bass by a small amount. In order to verify the bass alignment used by Fairfax, a close microphone measurement was used on the cone and vent to deter mine frequencies of loading. The cone SPL peaks at 80 Hz and dips at 27 Hz, while the vent peaks at 60 Hz. This verified the one-meter SPL measurement of Fig. 2. The general strength of the woofer compared to the higher frequency drivers indicates a direct sound which will be strong in mid bass.
The phase response in Fig. 3 shows that the bass and mid range are in phase with each other, while the tweeter because of its forward acoustic position-leads by 180 degrees. This plot is made in three parts, from 100 Hz to 1 kHz for the woofer, from 1 kHz to 10 kHz for the midrange, and 10 kHz to 20 kHz for the tweeter. The response is non-minimum phase around 1.5 kHz, 4 kHz, and 10 kHz for this one-meter position.
Figure 4 is the three-meter test which generally is a better indication of the timbre of early sound when heard in a conventional listening position. The on-axis and left channel stereo measurements are shown displaced 10 dB on this plot for clarity of presentation. The measuring position is one meter above the floor and three meters from the front of the speaker. The center reference position of the tweeter control is used for this test. These results show that the top end will be down in level when the speaker is used in a conventional stereo position. It will be necessary to use a fair amount of treble boost to bring the extreme top end up to a level equal to the midrange.
Fortunately a conventional tone control starting to boost at 1 kHz can substantially correct this condition for the normal listening position. A better solution, if it is possible, is to rotate the speakers toward the listening area. Because of the bass alignment, this works well in combination with moving the speaker into the room and away from a wall for more uniform bass.
The polar energy pattern, shown in Fig. 5, also indicates that more sound energy will be obtained with the speakers rotated toward the listening position. However, there is some polar fingering and you might wish to try several positions for best sound. The tweeter contour control has calibration marks of -3,-2,-1, 0, +1, +2, and +3. These marks cover 180 degrees of the control shaft rotation and are the likely index positions for an owner to use, rather than the extreme clockwise or counterclockwise positions. The +3, 0, and-3 positions were used to obtain the polar data of Fig. 5. If the set is mounted against a wall, this plot shows that the left channel stereo speaker will be somewhat hotter than the right for narrow speaker spacing but will be equal for wide spacing.
Harmonic distortion measurements are shown in Fig. 6.
High sound pressure levels are achieved at E1 (41 Hz) only at the expense of moderately high distortion. Tones in the octave above that frequency, however, are handled readily with low distortion. In fact, the measured distortion at 110 Hz (A2) is as low as many of the better amplifiers at normal sound pressure levels, which is extremely good.
Intermodulation distortion, shown in Fig. 7, is also commendably low at all power levels up to the maximum test level of 100 watts. What modulation that does exist is mostly amplitude modulation. The A4 tone (440 Hz) has about 1 dB average reduction at 100 watts drive compared to 0.1 watt. The crescendo handling ability of the same driver is quite good, and instantaneous noise peaks of over 400 watts can be handled without noticeably affecting inner musical voices. The sound should be clean without any strain on peaks even up the limits of most super power amplifiers.
Figure 8 is the energy-time plot for the first two milli seconds of sound arrival. The leading edge of transients are sharp and clean but diffractive scatter from the enclosure housing takes its toll after the first half millisecond. Be cause of the substantial volume of sculptured foam used by Fairfax in the grill of the FX-350, a measurement was made of the transient response with and without the foam in place. Except for less than half a dB drop in level for the first one-tenth millisecond, the foam doesn't change the response in the slightest.
Fig. 6--Harmonic distortion for musical tones E1, A2, and A4.
Fig. 7--IM distortion of A2 (440 Hz) by E1 (41 Hz), mixed one to one.
Fig. 8--Energy-time response.
Listening Test
Two different positions were used in listening to the Fairfax FX-350. In one position the speakers were placed flat against a wall and in the second the position was away from the wall and angled in toward the listening position. The balance, particularly mid bass, was better when the system was away from the wall. The difficulty with a wall placement was a prominence of middle bass frequencies which could not be adequately controlled by conventional tone controls without causing an unnatural loss of extreme low bass.
When properly placed, the bottom end is solid with only a small tendency toward hangover marring an otherwise excellent performance. When listening at brisk levels, however, warped discs can cause muddy bass due to excessive cone excursion. Therefore, use of a rumble filter when playing discs is recommended by this reviewer.
The extreme high frequencies are down in relative level. This reviewer found that a +3 tweeter level position together with a treble tone control touch-up restored spectral balance. It is better to bring the tweeter control up partway and then touch up with the tone control, instead of using maximum tweeter level, because too much tweeter causes a top end bite which can be unpleasant with some listening material.
Pipe organ sounds good on the FX-350. All but the deepest pedal register is there, and general sonic balance on middle and upper registers of the organ are good. Stereo center-image solo vocalists, both male and female, are quite good.
However, choral groups appeared to this reviewer to lack stage presence and depth primarily because of the top end drop which reduces sibilants. Rock sounds fine on the FX-350 and good gut-thumping kick drum can be obtained even with the speakers away from the wall. An attractive speaker which will blend with most any listening environment, the Fairfax FX-350 can suit the sonic requirements of most listeners.
-Richard C. Heyser
Ed. Note: We understand from Fairfax that a new version of this speaker has incorporated a 5-inch midrange designed to help improve vocal stage presence.
(Audio magazine, Nov. 1974)
Also see:
Fairfax FX-300 Speaker System (Equip. Profile, Nov. 1972)
Fairfax FX-300 speaker (ad, Feb. 1974)
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