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Product Review - AudioControl BijouTM THX Equalizer - January, 1997

By Stacey Spears

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AudioControl Bijou Home THX Room Equalizer; Seven channel equalizer; Left front, right front, center, left sub, right sub, left surround, right surround; Frequency response 20 Hz - 20 kHz plus 0, minus .25dB; Harmonic distortion 0.01%; S/N 109 dB; Maximum output 6 Vrms; Size 4.75"H x 17"W x 11"D; Weight 12 pounds; $995; AudioControl, 22410 70th Avenue West, Mountlake Terrace, Washington 98043; Phone (206)-775-8461, Fax (206)-778-3166; WWW: http://www.audiocontrol.com

Introduction (
The Standard Equalizer Intro)

*** Warning *** Equalizers ("EQ") are not the "end-all, save-all solution." Care should be taken in proper speaker placement and room treatment before ANY equalization is performed. Remember EQ's are intended to help provide a flat response from your loudspeakers, NOT to redesign the them. Now that I have said that, I can begin.

I have never been on the 'Anti-EQ' front. My point of view is that if both the film and recording industry can and do use EQ's to correct for small problems, why can't I? The problem lies not in the EQ but in the way in which it is used. Whenever I visit the home of someone who owns an audio system with an EQ, the EQ controls usually resemble a V pattern: the low and high frequencies are boosted and the midrange is cut. When I ask them why they have it set that way, the response is, "That is how it is supposed to look." Look? I end up playing some music for them, then during the middle, I hit bypass and they are usually shocked at how much better it sounds with the EQ off. They have never listened to it this way because out of the box they adjust the EQ and never listen to any other way. Of course, not all of them like the change when I bypass the EQ. They prefer their system to sound like a mini truck! "Boom, Boom, Boom." The problems represent an improper use of the EQ, due to lack of experience and or test equipment to properly set them up, and secondly, most EQ's that come with rack systems are poor in quality, killing the signal as it passes through.

Enter AudioControl

AudioControl has been building high quality EQ's and Analyzers since 1977. They know that in the high-end world of audio that if their products do anything harmful to the audio signal, then they won't sell. The Bijou is the second Home THX Equalizer to come to market. It is the first THX EQ to be equipped with surround channel equalization, and it is also the first consumer EQ to have 1/6th octave control for the subwoofer channel. Other features of the Bijou include:


The layout of the Bijou is as follows: There are 11 bands in 1/3 octave intervals for each of the Left, Center, and Right channels from 80 Hz to 800 Hz. The Left and Right surround channels each consist of 8 bands in 2/3 octave intervals from 100 Hz to 6.3 kHz. There are 12 bands in 1/6 octave intervals for the subwoofer (one set for two sub's). Also located on the front is the Power On/Off button and the EQ bypass button. On the back are 7 RCA connectors for input and 7 RCA connectors for output. There are also 2 DB-25 jacks, one for input and one for output. Lastly, there are a 200 Watt unswitched outlet and a non-detachable power cord.

The Installation

Over the past few months, I have had the Bijou in two systems: One (System A) has 4 full range speakers (Front L/R, Surround L/R), a smaller Center Channel and a powered subwoofer. The other (System B) is a full THX speaker package, 3 identical L/C/R, 2 Dipolar surround speakers and a subwoofer. In both installations I used a THX certified surround processor and a THX certified 6 Channel Amplifier. System A is optimized for both Music and Film and is equipped with AC-3, while System B is strictly for film with no AC-3.

System A
: I used 3 pairs of interconnect cables from the Surround Processor to the Bijou and 3 more pair from the Bijou to the power amplifier. The real problem when using an EQ is that you must have double the normal interconnects. With a 2 channel music system this only requires one more pair, but with home theater you will need 3. This can really hurt the pocket book with "Audiophile" cables. DB-25 cables are available from any computer supply store or catalog, for less than $10 each. I am sure that high end audio DB-25s will be available shortly from numerous audio manufacturers.

System B
: I used 3 pairs of interconnect cables from the Surround Processor to the Bijou, and 1 Monster DB-25 cable from the Bijou to the Amplifier. Since the surround processor is not equipped with DB-25 output I have had to use separate cables. Since the Bijou has them, this allowed me to use the amplifier's DB-25 input. I think this was a really cool way to go: 1 big cable, very little wire mess. One note, my power amplifier "only" provides 6 channels, and the Bijou can pass 7 channels through the DB-25, two subs sharing a common ground. If I were to use two subs I would have needed an additional cable (either running to a separate amp or a powered sub) along with the DB-25 terminated cable.

Now that the hookup is complete, the fun part can begin. Calibration, while not that difficult, is VERY time consuming. The instruction manual, or Owners Enjoyment Manual as AudioControls calls it, is very easy to understand and gets you going very quickly. The manual is a general overview of the calibration process, and therefore I recommend obtaining the "Home THX Audio System Room Equalization Manual." I contacted the THX division through their home page and within a week I had the latest version of the manual. This manual goes into detail with examples on how to fine tune your EQ.

To get started properly you will need a Real Time Spectrum Analyzer. I use the AudioControl SA-3050A RTA which has all the requirements needed to properly setup an EQ and is very affordable. I also used my trusty old Radio Shack SPL meter, a microphone stand, some masking tape (to mark the spots where you place your mic stand), and a pink noise source. The SA-3050A is equipped with a generator, but I used the THX WOW disc for this (Chapters 8-11).

There are a few settings on your RTA that must be correct before you begin:


The actual installation in each system took a few hours. It consisted of measuring, adjusting, and then re-measuring. The utmost care should be taken to ensure that you do not go crazy with the sliders. You want to make the adjustments as little as possible. A 1 or 2 dB variation between frequencies is ok.

There were some variations for setup that I used between the two systems:

System A
: I used stereo mode for setting up all the channels. I had to do some interconnect swapping (I used the main Left and Right outputs) for the surrounds and again for the center and subwoofer. This was done because Pro-Logic limits the information in the surround channels, and AC-3 is capable of full range for all 5 channels. The main and surround Left and Right speakers were full range and the Center was cut off at 80 Hz through the control of the surround processor. I used the Subwoofer to help with the center and also as the .1 channel for AC-3.

System B
: This was the ideal setup for the Bijou. The Subwoofer handled all of the information below 80 Hz, and the Left, Center, and Right dealt with information above 80 Hz. The surround speakers were THX dipolar. I did all the measurements in Pro-Logic mode. Since the processor was not capable of AC-3, I was not worried about full bandwidth measurements in the surround channels. Eventually when AC-3 is added to System B, I will still be using the dipolar speakers. I will just ensure that bass management is properly being used, and the Bijou will still be good-to-go.

The Bijou in Action

The Bijou is compatible with AC-3 since it allows for separate adjustments for all the channels. It just does not cover the full spectrum for every channel. Just like the Rialto reviewed in November 1995, it is optimum for Pro Logic/THX, and not AC-3. Most of the problems I encountered were in the 100 Hz - 1 kHz range, so this unit does work for AC-3, but it is just not ideal. I would like to have seen 5 channels in 11 bands of 1/3 octave instead of the 3.

System A
: With the front speakers, all of the corrections were only necessary and possible in the 80 Hz to 800 Hz range, and everything was virtually flat above 1 kHz. The surround channels were a little trickier to work with since I only had half the bands. There were a couple of bumps that I could not get to, but in the end, the improvements were very noticeable. My center channel was a different make than the left and right speakers, and using the Bijou, I was able to bring them a little closer together (tonality). There was also better dialog intelligibility all around. I was also able to improve the tonal balance across the entire front, where the TV normally messes things up (reflections off the face of the picture tube from the center channel speaker output).

System B
: This system integrated with the Bijou much better. I followed the THX approach to the 'T'. I was able to dial in all 5 channels, with very little trouble. The Bijou really shined here; again dialog intelligibility was improved and I was able to correct for the TV's tonal effect on the center channel.

The 12 band 1/6 octave control over the subwoofer was really powerful. There was one major problem however, and that was the limit of the 1/3 octave analyzer; I wish a had a 1/6 octave analyzer. :-) I was in complete control when it came to the subwoofer. Bass was now tighter and more defined. The EQ has the ability to control 2 subwoofers with the 12 bands, but I only had one sub on hand at the time of the review.

There was no noticeable noise or hiss when the EQ was switched in (no music playing). I really had to press my ear against the speaker to hear anything. As with all EQ's, you have unavoidable phase shift, but since all channels are passing through the EQ there were no noticeable effects.

There is no better audio feeling than being able to sit down and listen to music or watch a film and forget about the actual hardware that is providing it for you. With the new release of, "The King and I", it was really nice to have characters walk from one side of the screen to the other and not have the tonal character of their voice change as they moved. Even with three perfectly matched speakers (as in System B), this was not possible without proper equalization, because of the different boundaries surrounding each speaker.

Conclusion

I found that proper equalization provided by the Bijou has added new depth to my listening systems. I was able to better control System B because of the way in which that system was configured. System A benefited as well; I just did not have as much control as I would have liked. If you are looking to extract the most from your home theater system, then I recommend you give the Bijou a test drive.

Stacey Spears


Copyright 1995, 1996, 1997 Secrets of Home Theater & High Fidelity
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