Room gain. Is it really free?

Diego Estan just published his Stenheim Alumine 2 review on SoundStage!. He used his acoustically treated 12×15' room and found the expensive Swiss 6.5" 2-way to be inexplicably bass shy. Being the publication's lab expert, he wanted objective confirmation so took measurements. "…I found that relative to 2kHz, the Twos yielded a -3dB point at 38Hz in my room. As a matter of comparison, most of the two-way standmounts with 6.5" midrange-woofers that I've measured in my room (always in the same positions) yielded -3dB points around 32–35Hz. More importantly however, the Twos yielded effectively no bass boost due to room gain. Although most of the two-way standmounts I've measured yielded 5–10dB of extra output at 50Hz compared to 2kHz, the Twos were basically at 0dB. Overall the Alumine's in-room response effectively looked like an ideal anechoic response – flat-ish from 40Hz to 10kHz. Research done at Canada's National Research Council (NRC) and Harman International suggests that (and this is true to my experience) without a few decibels of domestic in-room bass boost (below 100–150Hz), most people find that a loudspeaker sounds thin and lacks bass impact and fullness – which is how the Alumine Twos sounded in my room."

Comparing them to his reference Focal Sopra N°1 monitors, "… right from the start, one thing was immediately obvious and inescapable: the Alumine Twos lacked bass and the Sopra N°1s accentuated bass no matter what track I played. In fact it was so obvious that it became distractingly obvious – this is because the N°1s sounded almost like full-range speakers with almost too much bass output while the Alumines lacked appreciable bass output. And my in-room measurements confirmed these observations. As I explained above, while the Stenheims had effectively 0dB of bass boost (relative to 2kHz) in my room, the Focals yielded an admittedly over-generous 10dB of boost!"

Those rocks act like our room boundaries. They reflect omnipolar bass waves, thus generate bigger ripples (more amplitude).

This makes the perfect segue for a contention of mine. My favored Ripol subwoofers or equivalent bass systems built into floorstanders take some getting used to. If employed across sufficient bandwidth, they deliberately cancel most room gain to avoid ubiquitous sub ~150Hz response fattening. The NRC finding Diego references confirms just how used we all are to 360° bass radiation reflecting off all our room surfaces. Should that radiation pattern become far more directional, it creates more textural linearity with what happens above ~150Hz. That will first register as a lack of bass quantity to ear/brains conditioned by the vast majority of omni bass. As a front-ported box, the Stenheim's radiation obviously didn't get directional in the bass. Its designers must have built in room-gain correction by attenuating their mid/woofer accordingly. The result was simply the same. It created a 10dB loss against Diego's reference speaker. Which one was right?

According to habit and conditioning, clearly his Focal. Diego probably had to live with the Stenheim far longer before he could successfully overwrite his ear/brain's yardstick. Perhaps referencing the recorded tonal balance of his favorite music over premium open-backed headphones would have helped to eliminate his room for more triangulation? Diego did see that "one potential benefit of this lack of bass was the Alumines' portrayal of Bublé's voice. In my small room where bass modes up to almost 300Hz are standard, on this track in particular the singer's voice can sound too thick or chesty through most speakers without the aid of room equalization. Yet the Alumine Twos' reproduction of Bublé's voice on this track sounded exceptionally clean and completely divorced itself from each speaker's cabinet, flowing freely in space with just the right degree of warmth and upper-bass body."

That mirrors my own observation. Reducing room bloom/boom in the bass removes endemic overlay across the vocal range for higher transparency and intelligibility. The question is, who'd prioritize that over Diego's ten decibels of free LF room gain? That's no trick question. It points at the fundamental nature of this matter. It's virtually hard-coded to our expectations of what the 'correct' tonal playback balance in typical rooms should be. We can't just turn off room gain like a light switch. It's always on. That makes seeing its influence very difficult; unless we compare linear headphones and/or speakers which behave differently¹.

¹ Here we should also mention that room gain incurs a time delay since it's based on reflections whose path lengths are longer than the direct sound. The smaller the room, the shorter the extra path lengths and resultant delay. But a small blur in the time domain always factors unless we manage to eliminate room gain with a clever dispersion pattern's cancellation; or absorb it with sufficiently large physical room treatments to be effective across the necessary bandwidth [PSI's active corner traps shrink those size requirements]. Just cutting the extra output in DSP doesn't fix the time-domain behavior, only the frequency response. Now we'll have linear but still late bass by suffering overhang from acoustic reverb. Bass might start on time but doesn't stop on time.

If you follow my subwoofer adventures to explore Ripol bass, keep that in mind. Give yourself sufficient time to hit alt-delete on your brainware. Only then can you fully appreciate all the effects on their own terms, not by constant comparison to what came before. You may still prefer that. At least now you can be sure. Some comparisons are like that. They demand sufficient distance from what we're accustomed to. And it's not a matter of right or wrong. In these matters our personal tastes are never wrong. Over the last year, mine simply changed. Now I hear the usual in-room bass balance and textures as bloomy, ringy, blurry, heavy and dark. That's also because I reference the open-baffle Raal-Requisite SR1a ribbon earphones to tell me what the recorded tonal balance of my music is before a room adds its own ideas. But if we polled 10 listeners on this, at least 9 wouldn't agree. It reminds me of first cutting down on salt. Initially boiled eggs without salt tasted very boring. It was much later that my taste buds had sufficiently recovered from the salt addiction. Finally I appreciated an egg's 'self' taste which prior seasoning had papered over. Here too the standard diverges. Whenever a chef tells us to season our meat, he means put salt and pepper on it; and often copiously so.

When it comes to room reflections and what to do about them, we all walk our own path.  But we can probably agree that no ripples like above create the least distortion.

The thing is, if we don't eat out but cook for ourselves, we decide how much seasoning we want; if any. If we trust our ears, we likewise get to decide on our hifi's seasoning. Here we could say that Ripol bass—or any other tuning which counteracts room gain like apparently the Stenheim Alumine 2 do—is the lighter vegetarian or vegan option. It's clearly not for everyone. As to salt 'n' pepper, I've already got enough on my noggin to not need extra in my food or sound. This returns us to the headline. Is room gain really free? To my ears it now comes at a price I'm unwilling to pay. But in the core meaning of the word, it is free. If you use box not open-baffle speakers, it'll happen automatically at max reinforcement. If you then want to erase it, it'll take some doing (unless a manufacturer like Stenheim compensates for it in the frequency domain). As I've covered extensively in other articles and reviews, it can be done though it does call on some resourcefulness to identify the necessary hardware; or go pro on acoustic treatments. For most, room gain is simply a familiar friend they don't want to be without. In which case, forget I said anything against it.