A tale of three rooms, one subwoofer EQ: Why your room matters, and how bass correction can affect far more than what you might recognize as "bass".

This last autumn, SVS visited with our exclusive European and UK resellers and customers. Toting an early production prototype, of the AS-EQ1 sub EQ with me, I spent one afternoon examining its performance with Kent Home Cinema staff who graciously let me hammer their gear. The results were illuminating, even for us. Doing "field work" with customers around the world is rarely without surprises. Getting out from behind the desk for this sort makes our products better after all.

Set in an old brick three story building, the fine folks at Kent Home Cinema (on line they're Subsonic Sounds) have a rather swanky set of demo rooms. SVS subwoofers and speakers are well represented, but there is a mix of gear from all sorts of brands, including speakers and receivers most of us use every day. With a PC13-Ultra, sound meter and stack of music CDs I spent time in three completely separate and dedicated home theater rooms (they call them "home cinema" there otherwise we seem to speak the same language). From left to right above then I auditioned rooms. Call them 1, 2 and 3. Observations and results are further discussed below.

Room 1 open and airy main demo room: Beware the "perfect" room. They require less money.

The first room was the large and open main demo area at KHC. Wonderful Triad main speakers, and a PB13-Ultra stuck in a closed corner near the primary seat on some very nice leather "cinema" chairs. Just as SVS would typically recommend to customers. I checked channel levels using the Onkyo receiver test tones and set up the AS-EQ1. Of course I was hoping to start off things by showing how profound the audible results this box delivers. Thus I measured more room locations than I might have. So 26 positions were run, more than enough to tackle tough acoustics.

A word on procedure: I tend to bring up the AS-EQ1 results screen, even before I spend much time listening. Call it sneaking a peek at the questions to the test, if you will. But this afternoon instead I simply hit "play" and jumped right to "A/B" (that is "On" and "Off"). Oddly, I didn't hear anything at all at first. Back and forth a number of trials on a typically revealing B-52's "Funplex". Only after several punches at the GUI engaging and disengaging the filters (which takes about 3-4 seconds to transpire) could I hear the bass tighten, still, rather subtle overall. Damn. What could be wrong? It sounded darn good either way.

I finally checked the results seen above. From about 20-80hz was arguably the best natural bass response I'd seen in a room. No wonder there was not much shift from on to off. There should not be much change in a room like this. And while the AS-EQ1 is smart enough to improve things further still, it also won't "fix what ain't broke". Ian the General Manager noted with some irony, "yes, pretty subtle that". Indeed.

The morning papers had the first UK bank failures, and the news got worse as the day unfolded. Surely I could find a good old-fashioned messed up room like we make here in America? I didn't have to go far.

Room 2 small chic room : If you don't like your speakers you might dislike them less with flat bass .

This was more like it. Seen above, the chart came from a small dedicated room sure to have excessive deep bass gain, walled in brick, and with speakers I'd never heard or seen before. Given the stupendously good response in the room prior to this, I was unsure which way this trip to the UK would go. First the banks.....

Again I level matched with the Onkyo AVR test tones, then ran just 12 measured positions, finally showing bass response most audio enthusiasts can appreciate, but not in a good way. As I'd hoped, here was a room with some issues. There was a large measure of mid-bass "suckout", and response down low was capped with rather ugly peaks sure to resonate the radiators. Worse, for upper bass integration, there was plummeting response coming on as early as 50hz. This should sound pretty horrible when switching the AS-EQ1 off and on. And it did. Poor deep bass balance was audibly rectified (low resonance being downright painful with Blue Man Group) and the nasal overtones of Kate Pierson's vocals were gone from Funplex thanks to the bass harmonics returning to the fore. "Much improved" was the consensus immediately.

But these speakers were entirely unknown to me and frankly, as they say, "not my cup of tea". Playback levels were modest as a result. Still, the General Manager of KHC now noted a big shift and improvement, as did I. Switching On/Off was unmistakable with "on" clearly preferable, eyes closed even. Anything with mid-bass content seemed to literally enter or leave the room in the few seconds it takes for the FIR filters to fully engage and correct dynamic program material. The effect was eerie even if now familiar to SVS working with the AS-EQ1, neatly showing graphically the change you are hearing. But since I wasn't very comfortable with the sound of the mains, and endeavor to not break other people's gear with high SPL runs, I moved on to room 3. Dinner was not far off and I was fairly anxious to find a bigger bass challenge, plus a space where I could crank things up a bit more yet not disturb normal business.

Room 3. Where do these stairs go? : More space, speakers to pound on. And ... bass response from hell. Perfect.

Stairs? Of course, "they go up!". Room 3 was at the top of the building, always a workout carrying a PC13-Ultra. But I was resolved to show a room more akin to the norm, with the problems powerful subs can reveal, quiet, loud, or in between. The exercise was rewarded. Of the three, "the room from hell" was the shakiest by nature, being on the highest floor, with mid-bass that tanked hard, about 35-40hz, and never looked back. The low bass bloat was as egregious as the previous room, just hugely corrupting octave to octave coherence of the sound stage. Room two was bad, this was worse still. About what I've come to expect from most mid-sized home spaces.

The best part in this run was finding speakers I'm familiar with. KHC had thoughtfully put a 5.0 set of SVS S-Series speakers in this room. Searching for audible acoustical problems at low SPLs is all well and good, but never miss a chance to crank things up when you actually want problems to jump out at you. Given the PC13-Ultra's power, and the good boundary spacing the mains enjoyed in this larger area, the room should have lit up nicely after a level check. And it did, "Off" and "On" shifts in bass quality were gloriously revealed at all SPLs, well above what was run in room 2.

With the sub EQ "Off", Kate Pierson seemed to be singing through a kazoo in this room, completely devoid of the high bass harmonics and warmth her voice has in the heavily processed sound B-52's are known for. And the very low frequency synth bass ( recorded quite loud in amplitude) served to largely obscure the kick drum and bass guitar. Again, instruments would seemingly walk out of the room when the AS-EQ1 was off, and right back in again when "On". The very spotty response from chair to chair was notably absent. By now the staff were as wide eyed with "On" and "Off" as any audio OEM wants to see.

At the end of the day, results held fast with months of previous use in venues in the USA: Once you hear what your eyes are showing you, there's no mistaking bass balance has far more effect than you may have realized. In a room such as these (well, not counting the freakishly good "Room 1") you might cheat once or twice, and sneak a look at the EQ's green (on) status LED shift to red (off). Or, look at the GUI on the user's laptop. But after one or two trials, you virtually stick your fingers in your ears when the AS-EQ1 is toggled to "Off".

The change in a space like room 2 or 3 is about as subtle as a board up side the head then. Graphic results make it easy to visualize just what is happening. Even so, having done scores of spaces, these are solidly "average" when it comes to bass response. "Room 1" thankfully proved to be an aberration in Kent, just as it would be here in America. Best of all, the SVS solution seemed not to care at all what side of the Atlantic it was on.

Ron Stimpson, Co-Founder, SVS