krrish389 wrote:Some companies stick to the standard +/- 3dB deviation for frequency response, while others will list bass extensions as numbers -6dB or even -10dB. Is this just a way to make their specifications look better? How many dB, can you still see the bass feedback that can be used?
The specs given for loudspeakers (where they are given!) are typically a little different from those for audio devices like preamps or mixers etc.
No speaker will ever have a perfectly flat response across the entire audio bandwidth so the specs will usually include a 'deviation' value such as +/-3dB. The better the speaker, the smaller that deviation will be (and vice versa). For example, the Neumann KH80 specs give a free-field passband response of ± 2 dB between 59 Hz and 20 kHz, and an astonishingly impressive ± 0.7dB between 100Hz and 10kHz.
The other thing we like to know about a speaker is the bass extension, and so most manufacturers quote a frequency value to describe the 'lowest useful frequency' that the speaker can reproduce. However, there is no hard definition of what amount of roll-off attenuation is considered acceptable for this 'lowest useful frequency' figure.
Some manufacturers quote this at -3dB (which is the traditional engineering filter-defining attenuation level), some at -6dB, some at -10dB ...and so on. Obviously the bigger the roll-off amount, the lower the frequency number and the more impressive the speaker will appear (on paper).
Just because I happen to have the numbers in front of me, the Neumann KH80 quotes values for both -3 and -6dB thresholds, which are: 57Hz and 53Hz, respectively. And if they'd bothered to quote a -10dB figure it would be about 49Hz.
The other thing to consider is the type of speaker cabinet because that affects the roll-off rate or slope. The bass roll-off is much faster and steeper from a ported cabinet (typically) than a sealed cabinet, for example. So while the figures for a ported cabinet might appear to have greater bass extension (ie, a lower -6dB frequency figure) than a similarly sized sealed cabinet, the latter will still be reproducing audible bass at a much lower frequency than the ported cabinet because the bass rolls-off more gently -- as this diagram illustrates. Here the -3dB figure for the sealed cabinet might be 100Hz, while that of the ported cabinet is closer to 60Hz... but at 40Hz the sealed cabinet's output is some 10dB greater than that of the ported cabinet! So it's complicated... ;)
Subquestion - for a classical rock and folk listener, is there even a point in getting into the 20Hz range? The lowest bass note of a bass guitar is 31Hz and the lowest key of the piano is 27.5Hz. Looking at the instrument frequency chart, you get almost everything at 60Hz or higher.
Is there a point? Well, yes... although it depends on what you are trying to do.
If you are a mastering engineer then you need to be able to hear the entire audio bandwidth so that you can be sure you are processing it correctly. If you want to do that with loudspeakers then you're going to need very big speakers, and a very big room, and a lot of very well designed acoustic treatment! If you are an pipe-organ fanatic then you might also want to be able to hear (feel) the bass pedal fundamentals at 32Hz (or even 16Hz)...
But the reality is that few consumer-sized speakers are capable of reproducing frequencies that low with any power, and even fewer listening rooms can reproduce those frequencies with any consistency.
And yes, while the fundamental of the lowest string on a 5-string bass is around 31Hz (41Hz for a standard four-string), it's actually the higher harmonics that people really hear and which matter in the balance of a mix.
So, in reality, most amateur mixing work and domestic listening can be achieved with speakers with a rated bass extension down to 60Hz or so. Higher, in many cases... And where the really low end needs to be checked, good quality headphones make a very practical alternative.
Also, don't forget that even the finest speakers with the most extended bass-end will sound rubbish if the room is untreated. All rooms suffer 'standing waves' (low frequency reflections) which will cause some specific low notes to become amplified, and others attenuated as the direct and reflected sound waves interfere as they bounce around the room. The result is a really lumpy low end, making it impossible to accurately judge the mix balance, and it's extremely difficult to deal with as the wavelengths involved are enormous meaning the thickness of acoustic treatment has to be enormous too -- which is just not practical in the average bedroom studio!
So working with smaller monitors with a good -- but not silly -- bass extension actually makes a lot of sense...