My good friend, and President of REL, John Hunter, perhaps knows more about subs, room placement, and stereo "stuff" than the next ten people on the planet combined.
He sent me this detailed missive that I wanted to share with you.
"Brief anecdote, a few years back during product development of REL's 212/SX (2 active forward firing, one rear passive mounted high in the cabinet and one down firing) showed real improvements in room smoothing. The use of the 4 drivers was done to drive the room as evenly as possible, but one never knows if it all works till the end. During one of our final tuning sessions, we noticed that as we moved around the room-mostly from our primary 12’ and further back in the room from the average sub location that things seemed incredibly smoother. The normal room peaks at certain locations that are traditional trouble spots barely seemed to be there.
So I did what I generally tell the general public not to do (one is subjected to all manner of well-intentioned but often ill-informed and backed up by little experience measuring of speakers or subs in the far field) which is to not try to do far field measurements. There are a thousand variables, and one has to be able to draw on thousands of experiences to understand what could be a tiny error of mic position or even cancellation from another object in the room. But what we were experiencing was clearly a massive improvement. So I grabbed my trusty sound pressure level meter and measured with and without the sub in.
What I recorded that day is still our all-time record for peak/valley reduction. This was in a weird location approximately 5’9” off the floor and I went hunting in the general locale (well off the centerline of the room and at a height that anyone seated to listen would never hear it) to find it just to get a maximum reading. But we work in the room everyday so we know its ticks. Without the sub, playing one of our standard test cuts, we recorded a 16 db (to lowest reading) peak-to-valley measurement. With the final version of the 212/SX we recorded a 5 db peak-to-valley. That was using a single 212/SX, a pair nodule have doubtless been even better. Anyone who knows anything about room acoustics will tell you that an 11 dB improvement is insanely impressive.
On its own, this wasn’t something we actively were chasing. Quite the reverse, we had designed the 212/SX to be our highest output biggest sound field single sub, perfect for someone who wants to get a pair underneath a pair of great speakers but doesn’t have the patience or budget to consider one of our 6-packs. Amazing with large scale speakers, large panels like Maggies or SoundLabs come to life because the subs have enough surface area to produce a sound field that is as large as the panels are throwing.
I share this not to brag on the 212/S, others have already done that for us. This is shared more in the spirit of validating Paul's presentation that what is often not taken into account is that fine subwoofers, crossed over properly low and placed in a location that optimizes a variety of factors to get the best overall performance can really help.
Please DON’T make room smoothing your primary objective as a goal. Work to make the system sound its best, then leave it alone and ignore any far field microphone measurements you take, it’s likely your measurement technique that’s at fault. That’s not a criticism, just the reality that pro’s who do this for a living 8 hours a day develop deep technique when it comes to microphone placement. Believe me, I once watched Peter McGrath (of Wilson Audio, at the time engineering for a Harmonia Mundi recording) up and down on a tall ladder on and off for 3 hours hanging his proprietary “ball microphone” from a ceiling. I know, I was the guy holding the ladder. So there you go, yes subs can make an appreciable improvement to overall smoothing of response especially when their position is optimized in the room, which is Paul’s point. It’s your job to get speaker position optimized, then dial in a great sub underneath it. Once you get it done, leave the microphone in its case and enjoy the music or film."
Thanks, John. Well said.
