Thanks, Antone. The major focus of my music and my studio is Afrocuban rumba. This involves acoustic percussion, primarily congas plus claves, woodblock, and sometimes wood box drums call cajones. The bass content is important for 2 reasons. Most importantly, some very important parts of the rhythms are bass notes that are generally heard only by the musicians. This is because they are naturally softer and as you said the ear is much less sensitive to low frequencies. Sometimes the musicians inadvertently produce more bass sound than intended. I have heard commercial CDs in which these spurious bass notes have not been edited out and it sounds terrible. I suspect the studio's monitoring system was deficient in LF response. It is important to hear this in the mixing stage and edit these unintended bass sounds out as appropriate.
The effect of reduced perception of bass, especially at low SPLs, is huge. The Fletcher Munson curves are actually conservative in predicting the perceived effect. More recent curves, the ISO Equal Loudness Curves, are apparently more accurate than the Fletcher Munson curves and are more extreme in their predictions. Wikipedia has an internet accessible graph that compares the two, here:
http://en.wikipedia.org/wiki/Fletcher%E2%80%93Munson_curvesAs an example, for a 1000 Hz tone, 100 phon is the perceived loudness of a 100 dB SPL tone. The perceived loudness of a 40 Hz, 100 dB SPL tone is around 70 phon. At 20 Hz, your 100 dB SPL tone is perceived as having equal loudness as a 40 phon tone at 1000 Hz.
This has big implications for sound production. To produce a 40 Hz tone that is perceived as 100 phon requires about 117 dB SPL, interpolating from the graph. For a 20 Hz tone to be perceived at 100 phon requires 128 dB SPL. The situation gets even worse at lower SPLs. For a 40 Hz tone to be perceived at 80 phon requires about 106 dB SPL. For a 20 Hz tone to be perceived at 80 phon requires about 120 db SPL. The threshold of hearing for a 1000 Hz tone is at 0 phon but for a 20 Hz tone, the threshold of hearing is at 75 phon and at 50 phon for 40 Hz!
These perceived loudness curves are averages over small groups of study subjects that were included in the research studies, and I don't know how much variability of these parameters exists in the general population.
For this reason, seeking a subwoofer that is "flat" in its dB SPL frequency response seems very arbitrary, and it does not come close to ensuring that the perceived loudness is equal at different frequencies. A "flat" frequency response based on perceived loudness would sound massively different than what we are used to, aside from being technically unfeasible for bass frequencies. For mixing music, however, a "flat" frequency response in SPL gives us some basis to judge when the bass notes would sound softer or louder than the real life sound that was recorded, assuming the frequency response of the listener's stereo system or PA is also flat. To the extent that most people's stereos are not flat, our mixes will sound different on those systems, but there is nothing we can do about that. Also, some people choose to crank the bass and others cut it down.
So do you think that for purposes of monitoring recordings striving for a natural sound similar to the real acoustic sound, the small sealed sub I am proposing will be adequate?
If I need another 6 dB, I could build 2. I even thought of building 2 boxes 14" x 14" x 34" long, putting feet on the driver end and using them vertically as combined downfiring subs and speaker stands! Also, I already have the Peerless driver but the LAB12 driver has similar TS parameters and would give a similar response in the same box, with slightly higher sensitivity and double the power handling capability. I just don't know how clean (distortion free) the sound of the LAB12 would be between 20-40 Hz compared with the Peerless.
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Topic: Use DSP to extend and flatten frequency response of sealed box sub? (Read 21191 times)