Tuesday, November 22, 2011

House Curve discussion

Here's a discussion (or really, an introduction to the concept) of a House Curve, what I generally call "room curve" (coming from the Tact tradition of Room Correction System preamps).


He proposes an interesting way of setting curve by making 100 Hz and 30 Hz sound equally loud.  (Just due to human hearing response, the 100Hz would naturally sound louder if played at equal physical loudness, and the effect is greater at lower playback levels.  So this is obviously increasing deep bass response over the flat or natural response, a point Wayne doesn't make or belabor.)

I find the "discussion" (actually, there isn't any discussion, except Wayne raises and addresses some issues in his own writing) rather lacking.  The rationale for house curve is very flimsy.  I suspect that HTS editors feel take house curve as a given need, didn't need much convincing.  Wayne is at his best shooting down other bogus ideas, such as that a house curve is needed because of the industry's "X curve".

Despite having this gnawing feeling that rationale for a room curve (other than flat) is at best circular reasoning, I count myself as a believer in having a house curve and Wayne's ideas (such as the 30Hz, 100Hz test) are sensible even if his arguments for them are weak.

I'm thinking the way to think about this is to consider that every room has a reflective signature, and a room curve is chosen to make music more intelligible given that reflective signature, they type of music it is, the type of speakers, etc.  Start with this as "hypothesis 1" and I think it's fairly obvious.

"Hypothesis 2" goes farther, making some specific claims.  Flat average response falls flat because it lumps together direct and reflected sound, which the brain is somewhat capable of perceiving separately.  You would think the direct sound should be the flattest, if you equalize the total sound, which includes proportionately more bass, you will make the direct sound component of it lighter in bass.

Aha, but we do have ways of mesuring or computing direct vs reflected sound.  And a system can be designed around the goal of flat direct sound.  Has been I'm sure.  And what is the result?  I don't know, hypothesis 2 could be wrong.

"Hypothesis 3" takes a different but similar view.  Instead of direct vs reflected analysis, our brains are assumed to have real-room-response correctors.  When we go into any room, we start correcting the sound to fit our perceived sense of how the room itself boosts that (in modal patterns in the bass).  Therefore, the recorded sound played back should have those same boosts.

The problem, however, with taking H3 seriously is that flat-played-back sound will indeed get the room boosts added to it.  That is what the natural room boost does to all sounds.  So from this perspective, a "house curve" would be adding to this.  But why should boost be added more to played back sound

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