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Inside an AV receiver 2 - Loudspeaker tuning

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Inside an AV receiver 2
Inputs and outputs
Video connections
Signal processing
Loudspeaker tuning
VHF tuner and power amps
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LOUDSPEAKER AND ROOM TUNING

Premiere in this role within modern AV receivers is the Audyssey loudspeaker tuning scheme, that equalises levels and applies distance compensation. It works well. Audyssey have since introduced additional DSP based processing schemes claimed to improve sound quality in their MultiEQ XT room correction system.

 

Most receivers also have on board artificial acoustic effects such as Hall, Club, Church and even specific venues such as, from Yamaha: Roxy Club (L.A.), Hall in Vienna, Hall in Munich. Yamaha collected this acoustic data in the 1980s, so you won’t find modern venues like the 02, or halls once behind the Iron Curtain, like the Mariinsky Theatre!

 

So called ‘loudspeaker tuning’ can mean anything and here the power of modern DSPs is used, or misused, to apply a wide variety of effects, much like graphic equalisers of yore. Our listening tests show that they can enhance some recordings, but not others and are a blunt instrument that are not worth the effort of use (selection can be tedious). Importantly, none of these tuning systems compensate for low frequency room modes, our measurements show, so bass quality and problems like ‘room boom’ are not counteracted. Direct and Pure Direct bypass options remove all processing and consistently offer the most natural sound.

 

Audyssey loudspeaker tuning

Using a small microphone at the listening position, connected to the receiver by a long lead, Audyssey adjusts the loudspeakers of a surround-sound system, equalising their level at the listening position and applying time compensation for distance. It also senses the presence, or not, of a subwoofer and whether to apply bass management.

Our repeated use of Audyssey fitted to receivers on review show it works well. However, it makes the Surround loudspeakers ‘obvious’, swinging attention to the rear channels. Whilst we check Audyssey tuning effectiveness, we prefer to tune manually, using our ears, not even our Bruel & Kjaer SPL meter.

 

Audyssey MultiEQ XT

This system Audyssey claim “removes the distortion caused by room acoustics”, working in both time and frequency domains. Our listening rooms are fully analysed, treated and well balanced. The Audyssey MutliEQ fitted to an Onkyo TX-NR1007 receiver raised midband energy, rolled off upper treble and had no affect at low frequencies, our measurements showed (long term averaging using a third octave analyser, of a music sequence). Listening correlated well with measurement: the sound was apparently clearer and more forward, but it wasn’t even or balanced and with some recordings sounded too shouty and aggressive. The immediate apparent effect was seemingly one of improvement, but over a longer term the unbalance became obvious. Direct or Pure Direct was an easier and more fulfilling listen. Audyssey MultiEQ XT is best suited to cinema dialogue, where a midband lift will enhance intelligibility.

 

 

TONE CONTROLS & GRAPHIC EQUALISERS

Buried in the menus, most receivers have bass and treble tone controls and seven band graphic equalisers. Small amounts (up to 3dB) of boost or cut may well help correct loudspeaker imbalances, but room effects are not usually so amenable to such simple adjustments. At low frequencies there is too little frequency band resolution to have any useful impact on room modes, which are high Q and cover a narrow band of frequencies. Currently, this is a missed opportunity in AV receivers.

 

graphic-eq-menu

 

Graphic equaliser menu of a Marantz SR8002 receiver, showing nine band equaliser. The 63Hz band is set to +1dB to lift bass a little.

 

 



 
Comments (1)
AV receiver technology guide
1Thursday, 21 July 2011 09:06
Ian Walker
Very easy to understand & well written.

Look forward to similar articles on other subjects.

Ian Walker

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