To address the single most important factor influencing home theater system performance, room acoustics, AudioControl have introduced the DIVA, a 7.1 equalizer/processor that's equally at home in two-channel systems as it is in fully-blown 7.1 installations. Nigel Pond scratches the surface of this incredibly complex product and discovers another AudioControl success story...
Thanks to Sue Morgan of Nicoll Public Relations, Tom Walker and Chris Kane of AudioControl for their help and for providing the review sample.
AudioControl DIVA Multi-channel Equalizer/Processor Review
We often get asked questions about equalisers on the SMR Forums - which is the best to get, how to integrate them etc. The consensus reply usually is to consider first whether you really need one, then weigh the pros against the cons. The problem with equalisers is that they have a lot of historical baggage to overcome. Most so-called "hi-fi" systems of the 70s and 80s had built-in "graphic equalisers" (usually with slider type controls on fixed center frequencies and bandwidths with adjustable amplitude, so the adjustments form a "graph" of the frequency response). Consumers loved them because those slider controls made them feel like a recording engineer, like they had some real control over the sound that came from their speakers, but, frankly most of those equalisers were junk, and few consumers knew their real purpose or how to use them correctly, so they deservedly got a bad reputation. The home theater revolution of recent years has raised the bar for affordable quality audio reproduction and with it the equaliser has staged something of a comeback, but this time more knowledgeable consumers are demanding more from them and manufacturers are producing the goods. What's more, advances in 'DSP' chip technology now allow EQ functions to be carried out in the digital domain, giving many more options and precise control over the process than is possible in an analogue device. Even so, many enthusiasts, myself included, have been somewhat reluctant to take the EQ plunge for fear that inserting another box into the signal path would do more harm than good. However, when AudioControl made the offer of a review sample of their top of the range DIVA, the new 24 bit, digital, programmable audio correction system, we could not resist. My home theatre system is set up in a partly finished basement, open on one side and with exposed rafters and so is an ideal "difficult" environment to test such a processor. Another big plus for the DIVA is that it is 7.1 channel compatible right out of the box so it will match up nicely with any THX® EX/DTS ES (matrix or discrete) processor. I am not aware of any similar product which provides EQ for any 7.1 system in one unit.
AudioControl has been in the sound analysis and correction business since 1977, in the home audio, car audio and industrial audio sectors, so they have a great pedigree. Their Bijou 7 channel analogue equaliser is, I believe, one of only two equalisers certified by THX® for home theatre applications, then there is the highly regarded Rialto and their Richter Scale electronic crossover/equalizer/analyzer which has been around since the early 80s. And let's not forget their SA-3052, a real time analyser well-known in the professional audio field.
It is impossible to set up a complex piece of equipment like the DIVA without some means of analysing what the system is doing. As my only measuring device was a trusty Radio Shack analogue SPL meter, AudioControl agreed to send along a couple of other goodies for me to use in setting up the DIVA. The first was the aforementioned SA-3052 RTA and the second, their new IASYS system analyser. Right on schedule a big box arrived from AudioControl containing all three items.
The DIVA is a very attractive piece of equipment, my review sample was the silver/aluminium version (black is also available), understated looks that belie the unit's capabilities. It is the usual 17" across (19" rack mounting hardware is available) and 2 standard rack units high (3˝ inches), so it will be equally at home in a standard 19" pro rack or home entertainment centre. The front panel is relatively straightforward: an on/off button; a graphical VF display; 7 horizontally aligned "main function" buttons; 3 vertical "menu soft keys"; and a large multi-function control knob. The rear panel is even more minimalist: 16 RCA jacks- 8 input and 8 output (a version with balanced inputs and outputs has also recently been introduced); power cord connector; power fuse; RS-232 connector and IR flasher jack. The unit also comes with a remote control which enables the user to perform set-up and user functions from their armchair. The processing is done by 24 bit Crystal analogue to digital converters on the input side, 24 bit Crystal digital to analogue converters on the output side and a pair of Motorola 56303 DSP digital audio processing chips in between to do all the really clever stuff.
Installation and Set-up:
Hooking up the DIVA is very straightforward: it is simply inserted in the signal path between processor and power amplifier, so in my case the 7.1 channel outputs from my Lexicon MC-1 were connected to the corresponding inputs on the DIVA and the 7.1 channel outputs from the DIVA connected to the appropriate inputs on my power amplifier. It is worth pointing out that the DIVA is not designed to be used with an integrated receiver/processor/amplifier unless it has a pre-in/out loop as it has to sit in the signal chain between processor and amplifier. The range of EQ adjustments available in each of the DIVA's configurations is set out in the accompanying table.
Once I had the unit hooked up and switched on, I left it in one of its default 7.1 channel modes while I read the manual! I should mention that the DIVA has 18 preset modes for various channel configurations from 2 channels all the way up to 7.1 channels. Switching between modes I could hear the differences between them, so I was eager to do some proper set up. I used a tripod at my main listening position to hold the calibrated microphone that comes with the SA-3052. The microphone has a long cable allowing the RTA (and the operator) to be set up in a position well away from path from speakers to microphone. For set up I used the test tones from 'Video Essentials', which are full range. It took me a while to get the hang of using the RTA but after a little trial and error the process becomes relatively straightforward. The RTA allows the user to store the response curve in memory and even to average out several readings (for example from several listening positions). Using the stored readout I could then adjust the EQ settings of the DIVA to smooth the curve out. A combination of the rotary control and the menu soft keys allows the user to select the appropriate frequency band and to cut or boost it. Chris Kane from AudioControl advised me to cut the peaks first then boost the dips - so that's what I did. It took me a little while to get the hang of using the DIVA's controls, but I soon got used to it. Once in "equaliser mode" (activated by pressing the appropriate main function button), the control knob is used to select the frequency to be corrected, pressing the knob then puts the knob into adjust mode and the knob is rotated to dial in the required amount of cut or boost.
After a few attempts I had the equaliser settings for the left channel just about as accurate as I could get them, so that the equaliser display looked pretty close to an upside down version of the RTA display. I continued the process for all 7 main channels and sub channel. I should point out here that the range of adjustment available for the side, and rear channels is not as wide as it is for the left, right and center. Despite the presence of those Motorola chips, there are limits to the DIVA's processing power and the trade off for more channels is less EQ flexibility for the "less important" channels. I have to confess that the first time I tried to setup the DIVA, in my haste to get to listening, I forgot to actually save the adjustments I had made. After a few uncharacteristic curses, I did the whole thing over again but this time saved to one of the DIVA's empty memory "slots" for future recall.
At this stage I did not tinker with the other parameters as I was anxious to listen to the results of my configuration. So I sat back with the DIVA remote control in hand. The remote has one button to bypass the EQ processing and another to defeat the other processing options, so a "before and after" comparison is easy to do. Even with cable TV selected on my Lexicon MC-1, I could hear a difference with the DIVA's processing engaged, in the lower mid-range especially, which is the area that showed up as most problematic on the RTA. Our local digital cable system does a better job with the audio feeds on the premium channels, and watching movies on HBO again showed audible differences again mainly in the lower midrange.
Switching to DVD sources I spun 'The Matrix' in my DVD player and again there were noticeable differences with EQ processing, again mostly in the lower midrange. A few days later I decided to check out the other processing options. First the parametric equalizer. Although after the initial set up the RTA did not reveal any large peaks or troughs still to be dealt with, I spent a little while twiddling with the parametric EQ. It only has two bands of equalisation, but the frequency on which each is centered is selectable by the user as is the width of the frequency band - very useful for taming a nasty peak. The DIVA also has a very comprehensive set of high-pass and low-pass filters that are capable of greater adjustment than probably any processor around. I did experiment with these, and they really are very flexible. However I have my MC-1 set up to use Lexicon's Bass Enhance feature which requires the processor itself to do the bass management, but the DIVA's settings can be disabled to avoid duplication of crossovers. Dolby Digital processors have built in compression to reduce the difference in levels between the quietest and loudest parts of a soundtrack. Most processors only have one or maybe two settings which are applied equally to all channels. The DIVA goes much further. It has separate compressors for each of the left, center, right and sub channels and the user can set individual settings for each channel. Additionally, the sub can be set to "hard" or "soft" (or left at "normal") according to whether you like your bass punchy or "fat". This would be useful in environments like an apartment for the purposes of maintaining good relations with the neighbours! I dialled in some temporary settings and played some DVDs with wide ranging soundtracks. The processing bypass on the remote allowed instant comparison and, as expected, the DIVA can tame the most "difficult" soundtracks. There are also options for limiters for each channel - useful for protecting your speakers, particularly subwoofer, from extreme output levels if your processor does not have limiters built in. The final set of adjustments are delay settings for each channel, and again they are more flexible than those in most processors. So if you are intent on setting up the delays perfectly for that one sweet spot in your system, the DIVA can do it easily.
Although it is difficult to do A/B comparisons between the DIVA in the system and out of it, the DIVA did not seem to be degrading the sound performance to any great extent - a tribute to the quality of the a/d and d/a converters. I did however notice that with the DIVA in my system I was getting some hiss, particularly from the rear channels in my 7.1 system. After exchanging e-mails with AudioControl's Tom Walker and Chris Kane, I was able to reduce the hiss by boosting the levels into the DIVA (by increasing the output levels of all my speakers to maximum in the MC-1's options) thus increasing the signal to noise ratio. Having made that change and with my system running at the usual volume level the hiss was less perceptible.
Just before I returned the DIVA to AudioControl, I decided to try it out in 2-channel mode. In two channel mode a far greater range of adjustment is possible than in 7-channel mode - the processing chips can devote all of their processing power not being used for the center, surround and sub channels to providing more, narrower, frequency bands for adjustment. Once completed I sat back and listened to some of my favourite CDs. Musical reproduction was very well "rounded" and again I could detect no audible sound degradation from the a/d and d/a processing within the DIVA.
The DIVA must be the most flexible audio processor on the market today. Notice I didn't say Dolby Digital® or DTS® processor, because it does not "decode" any audio format, but it is a very sophisticated processor of the output from those decoders and any other stereo or multi-channel analogue output. This processing power has a price - the DIVA lists at $9,000 so it is not for everyone. But if you want the ultimate in system flexibility and control then the DIVA is the processor for you. Or, for example, if want an add-on to improve the capabilities of an existing tried and tested system, the DIVA should be top of your list.
More information can be found upon the AudioControl web site.
Last updated January 1, 2001
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