Ken Dibble concludes this short series with a review of the JBL 4425 and compares the results with the Urei 809 reviewed last month.

Last month we discussed the country cousin relationship between these two West Coast studio monitor loudspeaker systems, set out the tests and the criteria to be applied, and reviewed Urei's new baby monitor, the 809. This month, it's the turn of JBL's baby: the 4425.

JBL4425

General Specification
Drive unit compliment
Single 2214 30cm lo/mid cone driver with 2342 bi-radial constant directivity HF horn and 2416 titanium diaphragm compression drive unit.

Crossover
Internal passive 2-way, 12dB/oct, 1.2kHz.

User Controls
Mid-level, HF level.

Cabinet loading
Direct radiating 54Ltr tuned reflex.

Impedance
8Ω nominal, 6Ω minimum.

Fundamental Resonance
34Hz

Termination
Screw terminals/4mm sockets

Power Rating
200W with band limited pink noise to IEC-268:1 or 1 kW 10mS peak unclipped.

Sensitivity
91dB for 1 W at 1m.

Dispersion Angle
100° x 100° nominal.

Dimensions
635mm high x 406mm wide x 310mm deep (375mm deep to include horn flare).

Weight
26kg

Finish
Oiled walnut cabinet with slate grey horn panel and dark blue fabric grille.

Price
£937.25 each suggested retail, including VAT.

Design Concepts and Presentation

Like the Urei 809, the 4425 also represents an attempt to provide a small but highly specified studio monitor based on the success story of a larger system. In the case of the 4435, it is derived from the JBL 4430 and 4435, but employs scaled down components. The system is intended for use in smaller control rooms and in other demanding audio production applications. Smooth accurate frequency response, flat power response and high power handling, combined with constant directional characteristics are the design objectives and as with the Urei, the 4425 also comes as left and right handed versions to maximise accurate imaging.

In total contrast to the Urei however, the 4425 is finished to a very high standard, with oiled walnut veneer to the cabinet sides, smart slate grey top panel carrying the horn and crossover control panel and blue stretch fabric covered detachable grille. Even the front rim of the drive unit chassis is black painted and finished to provide that little sparkle when the grille is removed. It is an altogether superbly presented and finished loudspeaker, quite in keeping with the long held traditions of this manufacturer.

Constructional Aspects

The enclosure is of 18mm high density chipboard and has no further bracing except for a horizontal webb across the top which supports the compression driver unit, thus relieving stress at the horn neck. Also, there's appreciably less internal absorption than with the Urei, with just a thin scrim of low density fibreglass quilt over part of the back and the four sides. Whereas the Urei has a single, short square reflex port, the JBL sports two smaller circular ports, each with a cardboard tube duct at least half the internal depth of the cabinet. So there is an immediate and obvious difference in the way the two enclosures are tuned.

The 2214 lo/mid driver and the horn flare are the front loaded and secured by machine screws engaging with tee nuts recessed into the chipboard.

The 2214 driver itself is visually identical to that fitted to the Urei 809, having the same chassis, the same cone, and a similar foam plastic front suspension. The magnet too is the same symmetrical field ceramic unit, including the hole through the pole piece for location of the co-axial horn unit in the case of the Urei, but in this instance, the screw thread to facilitate mounting the compression driver on the back of the magnet plate has not been cut. Also, whereas the Urei unit has the third spider suspension point at the base of the horn flare, the 2214 is a conventional single spider arrangement.

There does however seem to be a difference in suspension compliance, the 2214 being noticeably higher compliance than the unit fitted to the Urei, and would therefore be expected to exhibit a lower free air resonance. Such a difference would account for the different reflex tuning system employed.

The HF horn is of the now familiar JBL 'baby's bum' bi-radial, constant directivity design and is moulded from acoustically inert high impact structural foam. The 2416H compression drive unit is a recent development from JBL and is an attempt to provide good high frequency performance from a moderately priced unit with a standard european 1.375" x 27tpi screw thread coupling. It features JBL's latest titanium dome and diamond suspension technology and, unusually in a driver whose design parameters are governed by cost constraints, the diaphragm and phasing plug are in a compression chamber at the rear of the magnet assembly. That fitted to the 4425 is a bare bones version of the commercial product with no cosmetics, but does seem quite a nice unit. Exactly the same unit is fitted to the Urei 809.

The crossover appears to be a fairly complex affair and is mounted on a PCB attached to the back panel of the cabinet so that the screw terminals protrude through an appropriately placed cut-out. Apart from the user controls and a large laminated iron cored inductor (presumably the series inductor in the lo/mid leg of the network which is separately mounted to avoid undue strain on the board), all components are on the one circuit board and appeared to be of an adequate quality and rating, with those Mexican capacitors much in evidence.

Test Results

Figure 5 shows the impedance/frequency curve. It can be seen that the lowest value reached is 12Ω, compared with a value of 6Ω given in the maker's specification. I really can offer no justification for this anomaly, as the 4425 was measured immediately after the Urei 809, on the same equipment and the same set-up, and was checked for accuracy afterwards. But 12Ω was the figure produced each time. In other respects, the general characteristic is very similar to that recorded for the 809, including a similar system resonance at 60Hz, and apart from that, it's value is in close agreement with the curve given in the manufacturer's literature.

Again, two amplitude/frequency curves were taken at 1W at 1 m in order to avoid confusion in illustrating the effect of the mid and HF level controls. Figure 6a shows the mid-range variation available with the HF control at its maximum (flat) setting whilst Figure 6b shows the high frequency variation available with the mid-range control set at its flat position. According to the control panel calibration, the range of control provided should be between +2dB and -8dB in the case of the mid-range level control and between flat and -7dB in the case of the high frequency control, and it would seem as if this is in fact what is happening.

Using the upper curve of Figure 6b as the nominally flat response curve, the sensitivity works out at 91 dB, which is in exact agreement with the maker's specification, and the useful frequency response at 45Hz-17kHz, which again is close to the maker's figures.

Figure 7 shows the amplitude/frequency response at 6dB below rated power (in this case 50w RMS sine wave) and indentifies the second and third harmonic distortion components. It can be seen that there is a small flurry of activity below about 200Hz amounting to some 1.5%-2% in all, and then the usual rising distortion normally associated with compression-type drive units, rising to around 10% above 10kHz. Nothing untoward here.

Figure 8 shows the horizontal polar response characteristics at 800Hz, 2kHz, 5kHz and 10kHz and it can be seen that the 4425 certainly lives up to its constant directivity design objective, with no more than a few dB deviation from the stated 100° Figure throughout the range. The asymmetry is due to the HF horn being offset to one side of the baffle panel. This really is quite an achievement in such a small loudspeaker system and demonstrates excellent control.

Unlike the Urei co-axial design, where drive unit displacement has to be compensated for electronically, in the case of the 4425 the two drive units are physically aligned one above the other, thus resulting in a system which is naturally time-aligned and therefore does not require special correction. According to the maker's literature however, a 0.4mS time delay is introduced due to the phase response characteristic of the crossover network, but according to research carried out by Blauert and Laws, this is well below the level of perceptibility. In practice, the measured data at 1 metre was 3.4mS for the LF driver and 3.3mS for the HF driver, showing a time alignment error of 0.1 mS.

Tabulated Test Data

Auditioning

Standing alone, the 4425 is an impressive loudspeaker, with particularly clear, well dispersed highs and impressive low frequency performance, if a little on the woolly side by comparison with my regular home hi-fi loudspeakers. But without being able to identify the reasons why, it seemed to me unexciting for some reason.

The first thing to strike home is the laid back, smoother subjective response of the 4425 when compared to the strident aggression of the Urei. The high frequencies in particular are more open than with the Urei and the bass is more forward, but it somehow lacks the attack and that uncanny impression of presence and loudness which characterise the Urei sound. Also sadly missing is that imaging accuracy.

With the JBL, the strings sound sweeter, the bass more rounded and full, and it sounds just as good on a Shostakovich symphony as it does on Dire Straits, making it obviously a better all-round choice, but gone is that screaming Knopfler guitar break in the live recording of 'Sultans' or the raucus rasp of Mel Collins' sax in 'Two Young Lovers'. To me, after the Urei 809, it is rather tame by comparison, but to others, the sweeter sound of the JBL was the more acceptable of the two.

As far as a studio monitoring application is concerned, it does not seem to have that absolute accuracy and imaging quality of the Urei either. But we must put all this into perspective. Had I not been reviewing the Urei at the same time, I would have rated the 4425 very highly, and it's indeed an excellent loudspeaker in all respects. It's just that the Urei 809 has something extra that really brings rock and roll music to life and sends that little shivering sensation down the spine at times. (You know what I'm driving at.) But that's not all; it has this phenomenal accuracy and definition as well which must render it just about the best small studio control room or near field monitor going.

Conclusions

Because of its very smart presentation and because its performance characteristics do not seem to favour any particular type of programme material, it will have a wide variety of applications outside the studio control room and would be equally acceptable in the smartest of playback lounges, editing suites, presentation studios, offices or homes.

Like the Urei, it's audibly better when driven by a large power amplifier and for studio use, it will benefit from active room EQ in addition to its inbuilt response contour controls, excellent though these are for more general applications.

The maker's literature is first class and includes a far more detailed specification than we have published within this review, with virtually all electrical and acoustical data amplified by no less than 24 graphs! The performance characteristics are fully described and the technical foundation and limitations of the data given is stated. And, interestingly, apart from that impedance anomaly, the data given is extremely close to our own laboratory resultsand observed details.

The JBL 4425s cost £937.25 each including VAT.

Further information can be obtained from: Harman UK, Professional Products Division, (Contact Details).