Product Review -
AudioControl Rialto Home Theater Equalizer - November, 1995
By John E. Johnson, Jr.
AudioControl Rialto Home Theater Equalizer; Seven channel equalizer/crossover; Left front, right front, center, left sub, right sub, left surround, right surround; Frequency response 20 Hz - 20 kHz plus or minus 1 dB; Harmonic distortion 0.008%; S/N 113 dB; Maximum output 7 Vrms; Crossover factory setting at 90 Hz, 24 dB/octave; Size 2.5"H x 17"W x 11"D; Weight 10 pounds; $579; AudioControl, 22410 70th Avenue West, Mountlake Terrace, Washington 98043; Phone (206)-775-8461, Fax (206)-778-3166
Mention the word "equalizer" to most audiophiles, and they will laugh. It immediately brings to mind the $59 special. On the other hand, many fine amplifiers have no tone controls on them, and colorations resulting from less than ideal room situations for most speakers give a sound that leaves something to be desired. Now what? Well, get an equalizer that is built with the same quality as the hi-fi rig. AudioControl falls into that category.
When AudioControl first invited us to review their products, I was one of those who laughed at the mention of "equalizer" too. Now I'm not laughing.
What is the purpose of an equalizer? All you have to do is hear a hi-fi system where the sound has a little too much mid-range, or is too bright at the top end, perhaps somewhat thin here and there, and you will know where the equalizer comes in handy. Now, of course, an audiophile can always use tube traps to reduce problems in the 100 Hz - 500 Hz range, and wall treatments to tame the frequencies in the 500 Hz and above range, but this is not a simple task, and the problem might exist in just one narrow region. Again, enter the equalizer.
The AudioControl Rialto is designed for use in home theater surround sound systems, and is the first 7 channel equalizer ("EQ") on the market. For the front left and right channels there are 11 bands (one set for both channels) in 2/3 octave intervals from 160 Hz to 16 kHz. For the center channel there are also 11 bands (one set) in 2/3 octave intervals from 160 Hz to 16 kHz. For the rear surround, there are 5 bands (one set for both speakers) from 150 Hz to 12 kHz. There is also a separate subwoofer set of 7 bands (one set for two subwoofers) in 1/3 octave intervals from 25 Hz to 100 Hz. The subwoofer bands may be switched into the front left/right signal path where they can be used to equalize the low frequencies of those channels, in which case, the subwoofer inputs are not active, but the subwoofer outputs (two RCA line level) are active at factory setting of 90 Hz crossover frequency and 24 dB/octave slope. The subwoofer bands can be switched out of the front left/right and in line with two subwoofer inputs (two RCA line level), in which case the front left/right are controlled by only the 11 band set, and the two subwoofer inputs are fed to the 90 Hz - 24 dB/octave crossover-filters and to the subwoofer outputs. All EQ circuits can be bypassed for comparing EQ with no EQ. There are also PFM (Programmable Frequency Match) filters for the front left/right and subwoofer circuits, factory set at 25 Hz, 18 dB/octave, for filtering out subsonic frequencies that might be undesirable. Lastly, there is a "Wide" mode for the front left/right channels that blend certain portions of these channels to give an effect of a wider soundstage.
On the front of the unit (see photo) are the on/off push-button as well as push-buttons for the equalizer in/out of circuit, subsonic filter in/out, wide mode in/out, and the sliders for the EQ bands. The bands may be adjusted for plus or minus 12 dB at each band. There is an on/off LED for power, but not for the other functions (EQ in/out, subsonic filter in/out, wide mode in/out). Although it is not necessary for lights on the sliders themselves, I feel that there should have been LEDs for the functions listed above. It is impossible to tell from across the room, which function is in or out of the circuit.
On the back are RCA line level input and output jacks for the front left/right, center, and two rear surrounds. There are also two input and output RCA jacks for two subwoofers. The switch for putting the subwoofer EQ bands in the front left/right channels or to the two separate subwoofer inputs is also located on the back. There are output level controls for front, center, surround, and subwoofer. Also on the back is an input gain switch for high output surround sound processors. The power cord and an un switched (200 watt) AC outlet complete the back panel.
The instruction manual is easy to understand and thorough. It has several diagrams for the numerous configurations that it might be used for. Although it describes usage in a digital 5.1 system (such as AC-3), and it could be used in such a system, the EQ bands are not full range in all channels (AC-3 is full range in 5 discrete channels, and limited range in the low frequency effects - subwoofer - channel), so it really is optimum only for Pro Logic, and not AC-3. On the other hand, we have found that most EQ problems are in the range of about 100 Hz - 3 kHz, so this unit will be all right for AC-3 situations, just not ideal.
The sliders for the EQ bands are variable resistors that are connected to op amps. The op amps serve as inductors, and there are fixed value capacitors for each band as well. The signal path does not entail one op amp after another, but rather, each band op amp influences the signal as controlled by a master op amp.
In use, we found that the AudioControl Rialto was very handy for about half the home theater speaker systems we have tested. In other words, half the speaker systems sounded fine with no EQ (and thus, one should not be placed in the signal path just for the heck of it), and the other half (in our listening opinion) needed some EQ here and there. This was usually a mid-range nasality in the center channel that was controlled by reducing the 250 Hz - 1 kHz range, although the front left/right was in need of high frequency reduction, and the surrounds in need of some high frequency boost on occasion (Dolby Pro Logic mode). The subwoofer bands were also useful, but mainly in controlling the front left/right channel speakers when they were in the circuit, rather than modifying actual subwoofer tonalities. We found no use for the subsonic filter, nor did we notice any difference (single blind) when the "wide mode" was switched into the circuit. The only use for the subsonic filter would be in the case where your speakers cannot handle very low frequencies, and since modern films can contain some really low stuff, this might be utilized. However, it seems a waste to be filtering out program information, and we feel it would be more prudent just to get a good sub that can handle 20 Hz (and lower!). We measured the Rialto's output at 1 kHz (volume level setting for 80 dB SPL at 1 meter from the center channel speaker) and found that, with the EQ out of the circuit, the output was 82 dB, which dropped to 80 dB when the EQ was switched in, with the 1 kHz slider set at its 0 influence detent. With the 1 kHz slider for the center channel moved all the way to the top, the output increased to 92 dB, and with the slider all the way down, the output decreased to 70 dB.
There was a small amount of hum and hiss introduced into the sound when the EQ was in the circuit, but we had to put our ears next to the speakers to hear it. There was no apparent (audible) degradation of the sound by using the EQ, although something would probably be detectable on an oscilloscope. There is some unavoidable phase shift in using any EQ (audiophiles' hair is now standing on end), but we found that whatever phase shift was occurring, did not become audibly apparent (perhaps due to it being the same in both channels being adjusted). Also, the Rialto is designed as a "minimum phase device". Because there are so many interconnects required for this EQ, we decided that it would have to work satisfactorily using inexpensive cables. Therefore, we tested it with a lot of Tandy Gold Patch cables (the EQ goes between the processor and the power amplifiers, or for receivers, between the pre-outs and the amp-ins). They did just fine. Of course, you can always just buy a bag (a BIG bag) full of your favorite high end interconnects, but . . . . mucho $$$$.
In summary, I have changed my mind about the use of EQ in home theater. As long as a good quality EQ is utilized, you should have no complaints. The AudioControl Rialto is such a unit, and we recommend that you audition one if you are not satisfied with the tonality of your present home theater speaker system.
John E. Johnson, Jr.
© Copyright 1995, 1996, 1997 Secrets of Home Theater & High Fidelity
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