Take Pioneer's VSX-AX4ASi, strip off a few inputs, lose the second zone remote and shave £150 off the price - and what have you got? Yup, the new VSX-AX2AS.

Blink, and you miss the differences between the two inside and out. Features like HDMI switching, video upscaling, an iPod dock cable and Advanced MCACC RoomEQ are common across the two. They have both been breathed upon by AIR studios, with standing wave, reverb and phase control, and both wear a THX Select2 badge.

So what's different? Around the back there is one less HDMI input, now down to three, and one less audio input. And the removal of both iLink and USB ports might be a pain if you have a top-spec Pioneer DVD player or a perverse desire for playing compressed music files from a USB drive.

Pioneer also claims 10W per channel less power on the VSX-AX2AS. That puts it down to 170W - our Tech Labs reveal it is 175W - identical to the AX4...

That model had 'issues' when I reviewed it a few months ago, so I accepted the near-identical AX2AS with some trepidation. I liked the AX4 for its power and features, but the MCACC RoomEQ had the electronic equivalent of a bad hair day, applying bizarre filtering that left the sound with dry bass and ear-syringing treble. Would I be in for more of the same?

Simple setup

Setup is delightfully straightforward, and if you want to go for the full auto-everything mode it takes hardly any time at all. The auto setup applies all the usual speaker checks, including relative volume levels, distances and size, runs the MCACC across all channels, applies the reverb and standing wave control and saves the data to one of six memories.

From here you can delve into the manual modes to tweak every setting - which, given the sheer number of filters, channels and adjustments could take you an ice age.

Sadly, the menus and graphic plot displays are all dull monochrome, but if you get the urge you can export the data to a PC using Pioneer's free download software and an RS232 cable. This gives colourful 3D plots of the output of each channel and suggests why some anomalies occur while offering ideas on how to avoid them.

The AX2AS and AX4ASi are essentially the same beastie, so it is no surprise that without the MCACC trickery switched on they sound like two peas in a pod. The robust, potent and slightly forward character remains, as does the trouser flapping LFE and tight upper bass. It likewise falls just short of greatness, lacking the last ounce of space and the wide open soundstage of the best at the price.

Yet the AX2's MCACC adjusted plots showed some variation from the AX4, thankfully. It still insisted on applying at least -4dB to every channel, which Annoyingly makes it relatively quiet at any given volume, but the bass-end fi lters are considerably more even-handed and the MCACC's tonal corrections don't conflict with the reverb and standing wave control quite so much.

The cavernous bass is better than ever and the subterranean heartbeat during the opening of Pirates of the Caribbean 2 is moving, both emotionally and physically. Stripping away your room's natural bass reverb and limiting the effects of standing waves makes for real drumskin-tight bass.

Any congestion of sound in the midbass is cleaned up by the filtering, leaving a sparkling soundstage. This effect is equally sublime through the dialogue, which becomes better focused and locked hard in the middle of the soundstage.

But it's not all roses. An increasing output from 1kHz upwards pushes the balance from forward to bright and if you have remotely aggressive speakers the sound is going to tear you to shreds at high volume. Splashes of sea swell sound more like a bag of irate snakes, and high frequency effects have a piercing quality that does wonders for clearing the sinuses, if little else.

The answer is to dive into the manual MCACC filters and start to trim the settings. In my room, adding 5dB gain to every channel's overall volume put the volume back on an even keel. Skimming 2dB of gain from the top three filter points for each channel meanwhile tames the tonality nicely.

Scratching the surface

This is a very coarse adjustment and even a cursory tweak following this indicates there are plenty more benefits to be had from fine-tuning. Now, if only my deadline was about six months away, I could probably say more...

I had only just got the straightjacket back from the dry cleaners since the departure of the AX4, and the AX2 is pushing my buttons in just the same way.

The MCACC has the ability to turn certain facets of the AX2's sound into sublime, awe-inspiring home cinema heaven, but getting the balance right in your room, with your speakers is far, far removed from the auto set-up promise.

To elicit the very best from it will require your time and patience in copious quantity. That makes the VSX-AX2AS a cautious recommendation.