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Questar QA3 Active Monitors


The QA3s are active speakers, with integral amplifiers and an active crossover. They're also diminutive in size and light in weight. These factors make them perfect for situations where monitoring has to be set up quickly and without fuss; you simply have to plug in a mains cable and the line level input and switch on.

Many of us will have been attracted to the advantages of speakers of compact size and levity before, but miniature speakers usually live up to expectations along the lines of there being 'no substitute for size'. With a judicious active approach though, this needn't be the case: the QA3s are claimed to be substantially flat from 55Hz to 22kHz and yet manage to reach up to 108dB (SPL). Given the size of the standard black ash finished cabinet, (420 (H) x 230 (W) x 245 (D)) this sort of performance simply isn't possible by other means.

Electro-Acoustics



The mid-bass drivers are a 6½" SEAS unit (pronounced SEE-AS) with a Bextrene cone, loaded by the sealed main enclosure ie. infinite baffle. The tweeter is a Scanspeak, but without the Ferro-fluid, which is intended to increase the PHC (power handling capacity). Designer Steve Craigie is well aware of this benefit, but felt that the fluid audibly damps the top end response.

The likely advantage of this general combination (ie. a 6½" driver instead of the usual 8" or 10" unit) concerns beamwidth in the midrange. By making the mid/bass driver's cone smaller, and/or by bringing in the tweeter at a lower frequency, dispersion in the 800Hz to 3kHz region can be enhanced, where it narrows most. The overall result is to make beamwidth - or dispersion if you prefer - more constant at all frequencies, which is good for stereo imaging and off-axis listening.

Electronics



Amplification is one of the chores that the QA3 user shouldn't have to worry about. Perhaps you're curious though? The mid/bass section employs two amplifiers driven in bridge mode to give 60 watts. At first sight, less power is assumed to be necessary for the tweeter, with it being driven from a single 20 watt amplifier card. Taking as our starting point the concept that transients in the top end can equal peak bass levels, (even if the mean MF level is down 10dB, or more), then the amplifiers should be of roughly equal size if premature clipping is to be avoided. However, the tweeter's nominal sensitivity is higher than the 6½" driver's (by around 4dB) which enables Questar to use a (cheaper) 20 watt amplifier card without risk of crunching the top end.

Incidentally, the amplifiers are based on a Hitachi power op-amp, which should spell reliability, aside from ruggedness and true Hi-Fi performance.

The crossover is two way, -24dB/octave, with a B4C alignment, that is, 'slightly' Chebyschev. The idea here is to utilise the moderate electrical phase shift and slight peaking to compensate for an opposing acoustic phase error between the drive units. On the frequency response graph, this has the effect of filling in a mild suckout (dip) around the crossover point. Steve Craigie used a gated Bruel and Kjaer measuring system to look at the group-delay; that's the overall acoustic 'phase curve', across the audio band. It may sound like a hi-tech gimmick, but put in sensible hands, this equipment should permit the designer to quickly and precisely tune the crossover to match the drivers.

An advantage of active speakers, discussed previously in HSRs 'Control Room' series is the fact that we can opt for dedicated EQ to flatten the speaker's response. The QA3s take advantage of this; there's an EQ network on the output of each crossover. And with each EQ being buffered by its remote power amplifier, a simple passive network suffices.

Listening Tests



The first thing to be said about the quoted 108dB maximum SPL is that it's a quiet one, by which I mean the QA3s do not sound loud - until you attempt conversation, that is. This is a reflection of low levels of intermodulation distortion (IMD) inherent in active speaker systems. The absence of IMD reveals lots of detail you wouldn't otherwise have heard. IMD also operates psycho-acoustically triggering 'excess SPL' flags in our hearing apparatus, which are linked to stress mechanisms. A small amount of distortion is necessary if we want a 'buzz', for through IMD and the 'Too much SPL' flags, loud music has the ability to inject adrenalin into the bloodstream. All too often though, excess IMD totally jams the mechanisms, with very negative results, such as hearing damage.

The secret of the QA3s then is to reduce IMD by an order of magnitude. After a while, the ears adjust to the new SPL v IMD equation. With QA3s, you hear 108dB (SPL) with the level of intermodulation products that would occur at around 93dB (SPL) on conventional speakers - hence the apparent 'low' level at first hearing. Meanwhile, the psycho-acoustic/stress mechanisms can have a rest and regain their sensitivity. All this is reflected by lack of fatigue. You won't tire quickly of these units on these grounds, provided you're not entirely hooked on the 'buzz' to be had from a raunchy, intermodulation-saturated sound. Sadly, I suspect most of us are, and there will doubtless be a strong temptation to wind the gain up past the point where you can hear the bottom end beginning to clip because the QA3s don't sound loud enough, even if your SPL meter averages 108dB.

Anyhow, lack of fatigue arising out of clean sound is something to take into account if you're likely to be working on a session through to 6.00am, with a bad cold and a long since emptied coffee jar.

As to colouration, there was an (ill-defined) discrepancy in the low mid/high bass, and the QA3s are undoubtedly on the bright side, viz. with prominent high treble. The critical mid region, though, is without blemish, a fact reinforced by a superlative horn sound; the absence of fatigue after several hours at high levels, plus the fact that mild tonal aberrations only become readily apparent on percussion and bass. All of these comments relate to personal taste of course, but the QA3s are unlikely to audition well if your penchant is for the bass end. Moreover, you'll need to sit dead on-axis for the correct bass perspective.

The low bass performance demonstrated control typical of carefully designed direct radiators - be they sealed or Thiele. The cones bottom very softly (not with a sharp crack), and on most material, maximum level will be the point where you can hear the cones begin to bottom. For listening, an AMP-01 precision analogue control unit was in use, and this has a switchable 'zero-option', with quasi-direct coupling in this position, ie. no effective LF filtering at all. This is an extreme test, but the fact that the QA3s lived through numerous bangs and crashes augers well for immunity to 'live' bass. At the same time, it's inevitable that raw bass will need to be monitored at lower-than-usual levels to avoid cone bottoming, but given this, you should not need to fear actual damage.

There is more to attaining good stereo than using a small cabinet, a small diameter driver in the mid, a flat response at the crossover point, and a cogent group-delay, but these are doubtless the primary needs, and the QA3s embody all four of them.

But sadly, the stereo imaging is not as good as the theory predicts - it's good in the domain of depth, but restricted and not as stable as it could be. To be fair, it's above average, but one would expect results not too far removed from the AKG LSM50 given accurate phase-alignment between the QA3's two drive units.

Of all the speakers reviewed so far, the QA3s are undoubtedly the best at fine details - sounds deep in the mix, pitch relationships and subtle sounds from acoustic instruments are all rendered with precision. Obviously, the converse is true: they're very bad at hiding the details you may not want to hear, which should be all to the benefit of your mixing skills. Anything competently mixed on QA3s will withstand close scrutiny.

Electro-Mechanics



The QA3's sensitivity is quoted not as the usual 1 watt @ 1 metre = XdB SPL, because this expression doesn't make a lot of sense with active speakers. Instead, it's given in terms of (line) input level, full acoustic output occurring with around -2dBu (600mV) going up the input. When reading desk metering, it may be scaled directly against each other, eg. -2dBu = 108dB SPL @ 1m, -12dBU = 98dB SPL @ 1m, -22dBU = 88dB SPL, etc.

Input is via a phono connector, which is not good, but unfortunately the crazed Hi-Fi market into which the QA3s are primarily aimed displays a total lack of awareness when it comes to using decent connectors - such as XLRs. On the plus side, you probably won't need to worry about wiring up nasty phono plugs, as Questar supply a pair of high quality, 5 metre phono-to-phono cables with every pair of QA3s, and it's easy to snip the phono plug off one end, and fit the necessary jacks or Cannons for linking up to the console outputs.

Input impedance is 68k, so no loading problems should be experienced - even with the relatively high impedance outputs on some oriental gear, which might be placed between QA3 and console output. Having said this, any high impedance input will pick up lots of hum/buzz/RF interference, particularly with a 5 metre 'aerial' attached, so when unplugging, (and assuming you don't switch off first) ditch the speaker-end of the lead(s) first.

On the rear panel, there's an on/off rocker switch, the mains fuse, and an IEC Euroconnector. Suitable mains leads are supplied, by the way.

The bass/mid driver depends on an airtight seal between the chunky aluminium rear panel (which also acts as a heatsink for the amps inside), and the enclosure, so perhaps it's a good idea to resist the temptation to look inside unless you've got some mastic handy, and you're prepared to spend 15 minutes cleaning down and resealing the surface afterwards.

For best results, the QA3s should be spaced a couple of feet from the wall, but positioning isn't critical, and you may prefer the slightly 'hot' bass response that comes from placing them in a corner or flush with the wall. Imaging was not improved in the nearfield so much, as is usual, and a working distance of around six feet seems optimum.

Conclusion



The QA3s excel in detail and clarity, and can offer analysis whatever musical diet you feed them. The midrange and top-end performance is outstanding at this price level, and as £399 effectively buys the complete monitoring outfit in one go, sheer value for money will be the number one qualification for many readers.

Price of the Questar QA3s is £399 inc VAT (although a substantial trade discount is available to 'professional' customers only).

For further details contact Steve Craigie, Questar, (Contact Details). Matching stands are also available for the QA3.



Previous Article in this issue

Tape Reversal

Next article in this issue

Quantec Room Simulator


Home & Studio Recording - Copyright: Music Maker Publications (UK), Future Publishing.

 

Home & Studio Recording - Feb 1984

Donated & scanned by: Mike Gorman

Gear in this article:

Monitors/Speakers > Questar > QA3


Gear Tags:

Monitor Speakers

Review by Ben Duncan

Previous article in this issue:

> Tape Reversal

Next article in this issue:

> Quantec Room Simulator


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