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Ethan Winer · 6th June 2005

Johnny,

> I think an open E on a bass guitar is lower than 50Hz, and one tuned to a D is even lower, and for sure the lowest note on a real grand piano is about 27.5 Hz <

I'll address that part first. Yes, the fundamental of a low E is 41.2 Hz, but most of what you hear is usually an octave higher. With an electric bass, the second harmonic is as much as 12 dB louder than the fundamental when the string is plucked in the usual position over the pickups. With other bass instruments, like a standup bass or tuba, the disparity is even larger. With guitars it's larger still. The last time I checked very low notes on a grand piano, there was almost no fundamental at all. So take that 27.5 Hz with a grain of salt.

> would it not be a good idea to at least show your specs going down to 27.5Hz? <

Sure, but it's almost impossible to get reliable data that low. Most labs are certified to measure down to only 100 Hz, and a very few labs are certified down to 80 Hz. IBM's lab we use is certified to 100 Hz. This does not mean the numbers suddenly become useless below that frequency! The size of the test lab determines the lowest frequency that can be tested reliably. As you go lower the margin of error increases. I devised a way to measure absorption reliably down to the lowest frequencies, and reported on it in THIS article. Note that this method does not yield absorption data as numbers. Though it is useful to see the relative absorption of different traps.

Also, bass trapping at very low frequencies is not as important as at higher frequencies. The important "fullness" range where things become boomy and ill-defined without traps is around 80 to 200 Hz. So that's where trapping is most important. Further, with "normal" single layer sheet rock construction, when you get down to very low frequencies the walls tend to pass sound rather than reflect all of it. Since all acoustic problems are caused by reflections, that's another reason trapping down to 27 Hz is not as important as at higher bass frequencies.

You can read more about acoustic labs and test methods in THIS article on the RealTraps site.

--Ethan

6th June 2005	#7
Ethan Winer Gear Guru Joined: Oct 2002 Location: New Milford, CT, USA Posts: 12,332 Thread Starter	Johnny, > I think an open E on a bass guitar is lower than 50Hz, and one tuned to a D is even lower, and for sure the lowest note on a real grand piano is about 27.5 Hz < I'll address that part first. Yes, the fundamental of a low E is 41.2 Hz, but most of what you hear is usually an octave higher. With an electric bass, the second harmonic is as much as 12 dB louder than the fundamental when the string is plucked in the usual position over the pickups. With other bass instruments, like a standup bass or tuba, the disparity is even larger. With guitars it's larger still. The last time I checked very low notes on a grand piano, there was almost no fundamental at all. So take that 27.5 Hz with a grain of salt. > would it not be a good idea to at least show your specs going down to 27.5Hz? < Sure, but it's almost impossible to get reliable data that low. Most labs are certified to measure down to only 100 Hz, and a very few labs are certified down to 80 Hz. IBM's lab we use is certified to 100 Hz. This does not mean the numbers suddenly become useless below that frequency! The size of the test lab determines the lowest frequency that can be tested reliably. As you go lower the margin of error increases. I devised a way to measure absorption reliably down to the lowest frequencies, and reported on it in THIS article. Note that this method does not yield absorption data as numbers. Though it is useful to see the relative absorption of different traps. Also, bass trapping at very low frequencies is not as important as at higher frequencies. The important "fullness" range where things become boomy and ill-defined without traps is around 80 to 200 Hz. So that's where trapping is most important. Further, with "normal" single layer sheet rock construction, when you get down to very low frequencies the walls tend to pass sound rather than reflect all of it. Since all acoustic problems are caused by reflections, that's another reason trapping down to 27 Hz is not as important as at higher bass frequencies. You can read more about acoustic labs and test methods in THIS article on the RealTraps site. --Ethan __________________ Ethan's audio book is now available!