May 16, 2010

Can you pass the bass test?

So you think you know bass? Take the bass test. Don't worry, you don't have to write anything. This one is "multiple guess." Answers below.

1. At 80 Hz bass can be localised

a. By no one
b. By some
c. By everyone

2. At 120 Hz bass can be localised:

a. By no one
b. By some
c. By everyone

3. The Shroeder frequency is:

a. The transition point below which bass uniformly pressurises a room
b. The transition point below which room modes are a problem
c. The point where a speaker's bass response is -6db

4. The most effective way to get a smooth in-room bass response at different positions is:

a. Place multiple subwoofers so that problem room modes are cancelled
b. Excite as many modes as possible using multiple subwoofers
c. Acoustic treatment (bass traps, tuned absorbers, etc)
d. EQ
e. All of the above except a
f. All of the above except b

5. Adding a second identical subwoofer will increase the maximum output:

a. By 3db
b. By 6db
c. By 12db
d. Impossible to say - depends on location

6. Movie sound tracks are set up so that the subwoofer level is

a. The same as the main channels
b. 3 db louder
c. 6 db louder
d. 10 db louder

7. Subwoofer A has 1kw of power handling and 80 db 1w1m. Subwoofer B has 100w power handling and 90 db 1w1m. Both have adequate excursion and thermal handling to handle the full power output of their amplifiers.

a. Identical maximum output
b. Subw A wins due to power handling
c. Sub B due to lower power compression

8. A rumble filter is

a. A high pass filter which eliminates all bass below a certain point
b. A low cut filter which attenuates very low frequencies
c. A low pass filter which keeps the cone under control
d. Both a and b

9. If a low frequencies were filtered with a second order (12db/octave) filter, below this point

a. Excursion will remain constant with lowering frequency
b. Excursion will be reduced but will still increase with lowering frequency
c. Excursion will be decrease with lowering frequency

10. In the bass range, in order to sound twice as loud, a sound must be increased in level by

a. 3 db
b. 6 db
c. 10 db

11. Two subwoofers are placed in different locations in a room, each having peaks and dips in different places from their interaction with different room modes. In one particular seating location, one has a peak where the other has a dip. Assuming there is no phase difference between them, the combined response of the two subs at that point will show:

a. An average of the two outputs where they cancel according to their respective levels
b. The dip will dominate the response and the peak of the other sub won't be able to couteract it
c. The peak will dominate the response and the dip will be eliminated

12. The smoothest in-room bass can be achieved by:

a. Dipoles
b. Monopoles
c. Multiple monopoles if correctly placed

13. Phase is significant at bass frequencies:

a. Because it has a big impact on spaciousness
b. As it relates to the transient response and thus subjective speed of the bass
c. To the extent that it impacts the steady state response
d. Both a and b

14. Using EQ to fix room issues:

a. Works in one position only and will make all other positions worse
b. Is the only thing you need to do for the best bass apart from get a top notch sub
c. Tends to work for part of a room, but usually not the whole room and can make some positions worse

15. When using EQ for dealing with room modes:

a. You can fill in dips if you have enough headroom
b. You can't fill in the dips - no matter how much boost you apply, they will remain

16. When using boost:

a. 10 db of boost requires twice as much power
b. 3db of boost requires twice as much power
c. 6db of boost requires twice as much power

17. A subwoofer driver is placed into a sealed box with a Q of 0.707. It has an fs of 20 Hz. If no EQ is used, the anechoic -3db point will be:

a. 20 Hz
b. 40 Hz
c. 50 Hz

18. The same driver is placed into a vented box tuned at fs. In comparison to the sealed box, we can expect:

a. Lower extension but the same output
b. One octave extra extension and about 5 db extra output
c. Less extension but higher output

19. We now use a high pass filter to keep the cone under control below tuning. In order to ensure that the excursion below tuning will never exceed excursion above, we need:

a. A first order (6db/octave) slope
b. A second order (12db/octave) slope
c. A third order (18db/octave) slope
d. A fourth order (24db/octave) slope
e. None of the above - it will vary with driver parameters

20. THD (Total Harmonic Distortion)

a. Is a useful measure which shows how accurate a subwoofer will sound
b. Is useful depending on the level - the ear is not sensitive below a certain threshold
c. Is an important measure - when considering the equal loudness contours they are more important than you might think
d. Is not critical for the bass range as our ears are not sensitive to bass distortion
e. Doesn't relate to perceived accuracy and is meaningless for subwoofers

You can find the answers here:

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