# Interesting paper on deep bass perception...

Here is something just linked to on Audio Asylum - a 48 page scientific paper on Speaker placement, externalization, and envelopment in home listening rooms (.pdf).

I haven't had a chance to read much of it yet, but anyone interested in the subject of proper bass and deep bass reproduction might give it a go.

Abstract

The ideal number and placement of low frequency drivers in small listening
rooms has been controversial. Most research has assumed listener satisfaction is
determined by the sound pressure as a function of frequency and source-listener
position. We believe two additional properties of the soundfield, externalization
and envelopment, contribute to listener preference. We propose mathematical
methods for quantifying these two perceptual properties given a measured or
calculated binaural impulse response. The Average Interaural Time Difference
(AITD) is our measure for externalization, and the Diffuse Field Transfer function
(DFT) is our measure for envelopment. An image model for small rectangular
rooms is used to predict the values of pressure, AITD, and DFT for different room
properties and driver locations. It is found that the low frequency pressure
uniformity, the AITD, and the DFT can be increased in the prime listening area by
using multiple low frequency drivers – especially at the sides of the listeners.
When playing material where the bass energy is primarily monaural, the drivers
on the left side of the room should lead or lag the drivers on the right side by a
constant phase angle of 90 degrees. Listening tests confirm the results of the
calculations.

What say the jury?
darkmoebius
4 responses
 10-13-2005 9:43amI was interested by this paper and had discussed it some time ago with a friend (mathematician). We made a VERY approximative experiment trying to apply the model.Of course, our room was irregular: floor had/has two levels, ceiling is roof with beems, stairway to one side & in the middle of the long length, front wall lower hight than back wall (slanted roof, etc). It's an attic, as you've already guessed.The signal went through (active & passive) volume control(s) to two, then three amps, i.e., 1-> wide range driver unit, 1->bass unit 1->"sub"-bass (40-~22Hz).We placed the latter on either side of a (listening area) couch at a variety of distances. We used an active xover unit with phase control.Approximating the perceived "pressure uniformity" referred to in the article, we found (afai remember) little difference between 45-90 degrees phase lag between the two sub units. OTOH and quite amazingly, I distinctly remember that alternating the phase lag between the two units did make a difference.This is just anecdotal, we didn't have appropriate s/ware, equip, etc.Cheers 10-13-2005 10:29pmVery cool Greg,I'm still reading the paper, but would love to try the 3 speaker approach if I can find someone in the Los Angeles area with an extra sub and an active crossover. 10-14-2005 9:47amAll you basically need is a cheap dsp like a behringer, a pair of "main" spkrs (that you have) and two preferably identical subs.The only reason we used three stereo channels is that we didn't really have a bass unit: the Lowther only gave us midbass to ~220Hz and the open baffle bass drivers really couldn't make it down to ~30Hz without monstrous equalisation. So, we let the bass work to ~50 & added two more 15" to work from there to 22Hz a L-R 24 hi-pass.Cheers 10-15-2005 12:38amCool, all I need then is to pick up one of the digital crossovers. I've got a pair of matching 87dB/8-ohm passive subs driven by a Hafler DH-500 amp (250wpc). My mains are ~-3dB@40Hz.