A Bass Question
I agree with those that say for music the Low E on the guitar is generally enough. If it rolls off after that then I would not worry about it at all. In fact, unless you have a very high end system, it is better to have bass roll off much earlier (say 60 Hz on a two way) as much of what you get in the extreme LF will all be distortion anyway. Even relatively good subs with large woofers and powerful amplifiers can cause tremendous amounts of distortion and this will ruin good music. 3rd harmonic distortion of a mere 1% on a 20 Hz signal will sound equally as loud as the 20 HZ signal itself (this is because your ear is much more sensitive at 80 Hz than at 20 Hz) You don't see many subs with less than 1% distortion at rated high levels of SPL output at 20hz - so even a sub with a roll off at 30Hz is preferable to all that distortion. Therefore most of what subwoofer and full range speaker owners (flat to 20 hz claims) are hearing on a 20Hz to 30 Hz signal is actually between 40 Hz to 90Hz due to harmonic distortion and the much greater sensitivity of the ear in the 40 to 90 Hz range. It is also not just a matter of hugely powered subwoofers - unfortunately voice coils get very very hot with all that power and you get significant audio compression as well as the distortion. Here is an example of an excellent subwoofer HT Shack subwoofer test - at 20 Hz it does not get much above a mere 100 db and you need 75 db at that frequency just in order to hear anything at all. This sub does get you an extremely impressive 115 db SPL at 40 Hz (but with 20% distortion however - good for HT but not quite acceptable for music). Furthermore as you get up to 80 Hz the THD remains quite high around 5%. This is still a fantastic sub that defeats most of the competition but I hope you are getting the point about how difficult it is to get a truly musical sub and why it may be better to simply roll off those ultra LF signals! My advice is to stay away from subs and "full range speakers" (down to 20 Hz) for music unless you can afford the best quality drivers. Good linear drivers are very expensive. This LMS-Ultra driver alone costs more than most complete subwoofers. This is the impressive results in a sealed 100 liter DIY enclosure. Again from HT Shack subwoofer tests. Note the very low distortion at extreme SPL's. Now that is a musical sub! |
A 20 Hz wavelenth according to this webside http://www.mcsquared.com/wavelength.htm is 56.5' so I am not sure how you arrived at 27.5'. My own room measures only 13' and I have speakers which go down to 33Hz and a sub which goes down to 10 Hz (-3db) and I can assure you I hear well below the 90hz (12.5') wavelength that the room can accomodate. My sub only switches on when there are signals below 33Hz and as such I can say for certain music (light jazz) its always on while for some (classical) its off except for brief moments, so depends it really depends on the music. My understanding is that we hear based on vibrations the ear drum picks up and not on wavelength. We can hear in water too or by placing our ears on any medium that will transmit sound like a wall. Take earphones which operates by moving the air in the ear cannel coupled to the ear drum. The only reason for a large room is that you reduce reflections as a result of being too close to walls. So I don't really see why you would need a huge room to accomodate a 20 Hz wave. Can someone explain this? |
My room is similar in size to Athipaul's and my sub also only switches on when bass signal is present. Although with mine once it's on it rarely goes off while music is present; it has a ten minute minimum. I feel like I'm hearing good clean bass in this small, well-treated room. It was all done through experimentation as I initially ran the system with zero treatment for a few days before purchasing the treatment material. The sound was all over the place and bass notes were boomy or nonexistent depending on where I stood/sat. Now the bass is clean and even anywhere in the room. How low does my system go? Can't say exactly as I don't have any measuring device, but tracks I use when auditioning equipment for bass reproduction are working very well. I suppose you could go the scientific route; get out your calculator and measuring tape but your ears will make the final judgment. I would think with a room your size, getting solid, even bass distribution would require even more work and a quality sub or two. Good luck. |
