Reply posted by Mikael Holm on January 19, 2002

“By offering the ability to deliver the OCTAVE of information from 20 to 40Hz you will double the apparent output of your system while protecting the hearing of your audience.”

What does this have to do with a club gigging guy who has to face >120dB Marshall stacks and the lowest note band will make is the E-string on bass guitar.

I have asked this before but you never gave me an answer.

Miffe


Reply posted by Thomas Danley on January 19, 2002

Hi

I can give one answer. One way to look at the musical spectrum is to examine the resonant frequencies of the instruments involved. As you mention the E string on a bass guitar resonates at about 42 Hz while a low E on a 6 string is an octave higher. There are charts which show this resonant or fundamental frequencies of most instruments.

End of story....not quite.

Modulation of or a change in signal amplitude ALSO has the effect of increasing its bandwidth. An old friend Don Keele had a goody disk for the TEF machine on which he programmed a 6 cycle long, gaussian amplitude envelope tone burst. This was a pure tone (low in distortion) but because of the amplitude modulation appeared to have a 1/3 octave wide spectrum, other less gradual amplitude envelopes produced an even wider spectrum too.

Since so much of music consists of rapid changes in amplitude, it is common for the musical content to go below the lowest fundamental note of the instruments. In fact Bass guitars produce so much VLF signal that it must be filtered out, plug a bass into a real subwoofer and see the cones dance. Also a drum head may resonate at say 30-50 Hz but the FFT of a drum hit up close is often a big peak at say 10 Hz with a more or less
straight line fall off with increasing frequency.

Time is the element left out when relating fundamental frequencies to the actual musical spectrum.

The bottom line is if you want to know what the spectrum is, you have to measure it.

If you have a subwoofer low enough in distortion to not interfere with the upper registers AND it is powerful enough to reach / surpass the threshold of audibility at those low frequencies, then with nearly ANY kind of music there is a subjective improvement when the lowest frequencies are produced.

Don Davis (the fellow who started Syn-Aud-Con) after trying a Contra bass (-3 @16 Hz) wrote that he had been wrong about adding the lowest octaves, that even with "event recordings" (like the Indy 500) or voices (non-musical program), there was an
improvement in realism when the lows were present. Funny too as he keep the Contra permanently as part of the demo.

Barry's point, which I have heard my self many times and agree with fully is, that when the low cutoff is extended downward (and this is NOT the same thing as louder bass), that the subjective "musical size" of the system is increased dramatically. This is because the lower you go in frequency (with in some boundaries), the more emotional impact the sound has. When that sound is music, the more dynamic, the more subjectively "loud" it seems.
I know your thinking "what do you expect from subwoofer guys".

Here is how you can find out for your self.

Take a couple large vented box subwoofers, plug the ports with an old tee shirt or perhaps something more elegant, the point is make them a sealed box and large enough so you won't have to drive them hard, cross them in around 50 Hz.

Set up a music system in a smallish room, a room with doors which can close, ideally making it more or less sealed off. Your typical subwoofer with the ports closed will have a roll off starting at a higher frequency but only having half the slope of the vented
box. Your room, being smallish, will have a room gain slope starting in the 35-45 Hz range (begins approximately when the longest room dimension is about 1/4-1/3 wavelength).

The room gain, (in a perfectly sealed room) is a +12 dB / oct slope once your below this knee. A sealed box sub on the other hand rolls off at -12 dB per octave and somewhere in a similar frequency range. In the perfect case, one slope totally cancels the other, the sealed box which has a 40 Hz cutoff in half space now has flat response to say 5 Hz in the room.
Anyway, it will be easy to adjust the sub level to give the right balance and a little vlf eq will bring out the "weight" in the music. Once you get it sounding "big" try your favorite music, then shut off the subs and see how different it is..

Try it if you want to hear why below 40 Hz is desirable.

Adding the VLF's to the band you describe probably makes the band just that much more "too loud" sounding. I don't know what you would do about that, I have seen / known guitar players in Bands I was in (and Brad if your reading this, your not one of em :-) that liked to be too loud all the time and were too often content at rehearsals to play on and on while the rest of the band stood and waited. Its a personality defect type thing....probably like how unsuccessful bass players get in to the sound business gulp. Maybe the answer would be a bank of really powerful, really directional horns as floor monitors, this way you would have enough horsepower on the man's monitor knob to force him to turn his stuff down, make it more than "loud enough" for the man and he will use his knob and down comes his Marshall stage volume...

Cheers,

Tom


Reply posted by Alan Wheeler on January 19, 2002

Hey Miffe, I can add support to both Barry and Tom's comments. I have been using VLF bass for a number of years now. I too have also struggled to convince other sound guy's it works. As Tom stated and in my own words to others, I describe it as giving the sound a "sense of bigness".

I use it to give me a perceived higher SPL level when infact it is not.
As to the thoughts about the fundamentals of instruments, I to believe there is info below those fundamentals. Lets take a Bass string.(I am a Bass player)There is information produced by the finger striking the string and the movement of that string before the finger leaves and the string vibrates on its own. This "feeling" may be very low in SPL, but it is there. Infact I beleive it is the reason why Drum machines and electronicaly produced Bass gats sound lifeless as to the real thing. There are sounds there that just aren't in the "machine" versions.

Regards,
Wheels