Last April, I was fortunate to be one of the first in the world (thanks to Mike C and to the proximity of the Philippines to Taiwan!) to get hold of an SVS AS-EQ1. This device provides “room correction” technology that is focused on subwoofers.
Why is “room correction” important? That is because no matter how good our equipment is, we listen to it in a particular room and that room (its dimensions, furniture, acoustic treatment or lack of it) will adversely affect the reproduction of sound, especially as it is perceived by the listener. For example, one hears the direct sound from the speakers but then one will also hear the reflected sound as the sound waves bounce against the walls, floors and ceilings - this tends to “muddy” the sound. Also, the dimensions of the room will cause certain frequencies to resonate and sound much stronger than others – these resonant frequencies tend to overpower the other frequencies and make them less clear; you hear less detail.
The AS-EQ1 uses Audyssey MultEQ technology. While some may dismiss MultEQ as just another one of those parametric equalizers, it really is much more than that. I would summarize the features of MultEQ, including its application in the AS-EQ1, as follows:
1. Similar to the function of a parametric equalizer, it flattens the frequency response of your speakers, albeit in a more or less automatic way. You just need to know a couple of tips on where to set the mic and adjust the subwoofer volumes, and there is a huge “Audyssey Set-up Guide” over at AVS Forum for this purpose. As contrasted to the typical parametric equalizer, however, MultEQ uses an Infinite Impulse Response (IIR) filter as opposed to the typical Finite Impulse Response (FIR) filter. Also, while most parameteric equalizers use a maximum of 9 adjustable bands, MultEQ uses hundreds of taps to produce its filter, thus making it more precise. The flattening of the frequency response has a huge effect on sound quality. It provides more detail and widens the sound stage. When you flatten the frequency response of subwoofers, you may also be surprised that a side effect is that the sound from all your other speakers seems to improve. This is because if your bass is not flat, it can get really loud and then drown out the sound from the mids and highs.
2. MultEQ significantly reduces “ringing” by applying a correction filter, not only for the frequency but also for the time domain. “Ringing” is a phenomenon similar to “ringing a bell.” When you ring a bell, you hear its sound for a very long time because it continues to vibrate (unless you put your hand on it). The same thing happens with sound in a typical room. The energy of certain frequencies (especially bass) will tend to stay in the room for a long time and this is an inaccurate reproduction of that sound. Furthermore, it will contribute to the drowning out of the other frequencies. When you hit a note in a bass guitar and you release your fingers, you should stop hearing sound. If you continue to hear sound because of “ringing”, that is inaccurate. When you reduce “ringing,” the bass notes sound much “tighter.” The sound of the bass drum should be strong, immediate and then stop; it shouldn’t sound “bloated.” MultEQ works like magic in reducing “ringing.”
3. MultEQ provides the accurate distances of each speaker to the listener. This is very important so that the AVR sets the proper delays for the signals to each speaker, which results in the sounds from all speakers arriving to the ears of the listener at the same time. This may sound very simple but for subwoofers, it is not simple at all. The reason is that subwoofers often have internal circuitry which causes a delay in the reproduction of the signal. Thus, the “acoustic” distance of the subwoofer may be farther than its physical distance and this difference may easily be in the area of 6 to 8 feet (which would be a difference in time of 6 to 8 milliseconds, and that’s audible). Without MultEQ, I’m really not sure how one would know the actual “acoustic” distance of the subwoofer and if you don’t get it right, you have that phenomenon of a “slow” sub (the bass notes are delayed). You often hear people say that this sub is “slow” and that sub is “fast.” I think what they really should say is that the subs have differing electronics which add different delays to the sound and which should therefore be properly compensated at the AVR.
4. MultEQ also provides the accurate levels for the various speakers so that their volumes are balanced. This is a relatively simple task for ordinary speakers if you have an SPL meter but not so for subwoofers, which are notoriously difficult to get right. Using an ordinary SPL meter, the reading for the subwoofer may easily be 6 db wrong, and that’s a huge number.
The SVS AS-EQ1 provides all of these MultEQ features, with the addition of its having at least double the filters of ordinary AVR’s, and its capability to handle 2 subs (or more). Setting up two subs, especially if they are not co-located or they are of different brands/models, is very difficult to get right. The AS-EQ1 makes this process rather simple. In my case, I actually have four (4) subwoofers which are grouped into two (2) adjacent pairs. Finally, similar to the AVR versions of MultEQ, the SVS AS-EQ1 requires you to set up a microphone and “ping” the speakers at different positions. While the typical MultEQ AVR version can do 8 positions, the SVS AS-EQ1 allows you to use up to 32 mic positions, which thus results in a more accurate reading of the room characteristics and consequently a more accurate filter.
The procedure for setting up the AS-EQ1 is quite simple, especially if you are used to the MultEQ technology. Lately, there has been some confusion about matching the levels between the subwoofers and the other speakers but this has largely been sorted out at the AVS Forum thread on the AS-EQ1.
How does my system sound with the AS-EQ1? I think that the improvement has been pretty phenomenal although I guess that some of it has to do with my having 4 subwoofers, because that gives me a lot of flexibility. The AS-EQ1 also makes it easier to experiment with sub positions. The AS-EQ1 shows you the frequency room before and after calibration. Too many people have posted these graphs so I won't bother. Let's just say that the response is nearly perfectly flat from 20 hz to 100 hz, which is perfect for me.
I have always preferred to judge bass quality with music material, rather than movies (explosions, bullets, cannons) because normal people are more familiar with music. We know what a bass guitar or a double bass or bassoon sounds like. I’m not sure many of us have heard a 50-calibre machine gun in real life. Thus, my favorite test material for bass is the HD-DVD of the concert of Cream at the Royal Albert Music Hall in 2005, track 12 (Stormy Monday), starting at 62:45. This is a pretty amazing sequence because Jack Bruce plays a bass guitar sequence, stepping through notes for up to 2 octaves. If those notes have an even sound, the frequency response is pretty flat – and with the AS-EQ1, the notes were incredibly equal in volume. This same track also shows Jack Bruce doing some effects, basically vibrating his fingers. This is quite common for lead guitars and its quite easy to hear the effect in the higher frequencies but for bass guitars, it’s very difficult to notice the effect. With the AS-EQ1, you could ever hear even that nuance – the detail is amazing. Finally, also on the same track, the drummer (Ginger Baker) has some loud thwacks on his drums and with the AS-EQ1, it sounds so tight, with very diminished “ringing.”
Having said this, how does movie material sound? My latest reference is the Bluray of the Incredible Hulk, the scene which includes the pulse cannons. That sequence has a large variety of deep and rich bass sounds – Hulk’s hand hitting glass, Hulk’s feet stomping on the ground, armalite rifles, 50-calibre machine guns, Apache helicopter cannons, pulse cannons, all sorts of crashes, etc. Let’s just say that with the SVS AS-EQ1, you can feel tremendous bass volume and depth. It is so strong that the room pressurizes so you can feel the bass. Yet, you can still hear a lot of other sounds clearly, including dialogue. The bass is balanced, it doesn’t overpower the other frequencies.
Overall, the SVS AS-EQ1 is a great product. Worth every cent.
