JVA said:
(I'm not GM, but then, who is?)
"Fast bass" is a pretty common term. The question is, what do people mean by it? Maybe they don't all mean the same thing. Someone, (Lynn Olsen?), said he thinks people use the expression for bass that has low IM distortion. In any case, bass is, by definition, slow.
Although I'm still driving on my learner's permit, I venture this: In order to get clean bass with some volume to it, you have to move a lot of air. In a small room, it might be possible to move enough air with smallish drivers with a modest xmax. It would depend on your expectations. But small drivers also tend to have high Fs, which is not a Good Thing for bass either.
Getting back to the original question, let me just reiterate that I'm using a 10" Peerless XLS with a 400 gram passive radiator in a 26 liter box with my Jx92s's, and I could not be more pleased. The mains are in sealed boxes. I'm running them with no high pass filter. The sub's low pass is set at around 80 Hz. It's in an office that's about 14' x 18' X 10', but judging by how much I have to turn it down, I think it would do quite well in an average size living room, except maybe for the lowest quarter octave.
Dave Jones said:
you are still to get a driver's licence (presumably because you are a bit young) but you are old enough to go to an office?
seriously what i understand by "fast bass" is the attack. the attack is actually a combination of the bass note as well as it's over tones. if you take a bass guitar (the low E goes down to about 42hz) you can either create a pure sine wave at 42Hz or a complex wave (by slapping the strings for example) that includes other overtones and by that nature sounds fast.
music usually is a mix of simple and complex sounds. everyone has his/her own definition of what constitues music and what does not. as a rule most of do NOT visit as many live concerts as we should or wish too and hence dont recalibrate our ears often enough. this is probably the source of the confusion.
"Fast" is common expression in audio mumbo-jumbo, as is another idiom - "speed" (ever heard of amplifier speed). Of course, a bass as low frequency sound can be as "fast" as are its frequencies it reproduces. A better word would be “quick” - quick to react or quick to go and quick to stop. In other words good acceleration and stopping speed. But not only that. One can say that a drag racing car is a “fast” car but try to compete with it on formula circle or on rally special stage. It just can’t react to the changes of the track as “fast” as F1 or WRC car.
As navin sayd, the bass in the music is seldom only a single note but several instruments playing a multitude of different notes (frequencies) or accords at warring speed and producing their accompanying harmonics at the same time. So how would you describe a low frequency transducer that can truthfully reproduce all that?
As navin sayd, the bass in the music is seldom only a single note but several instruments playing a multitude of different notes (frequencies) or accords at warring speed and producing their accompanying harmonics at the same time. So how would you describe a low frequency transducer that can truthfully reproduce all that?
Greets!
The lower the frequency, the wider its BW, ergo DC = infinite BW, but a speaker normally has multiple drivers electrically isolated from each other by XOs so that the woofer handles the lowest fundamentals and their first few harmonics (slow), the mid driver the middle harmonics (faster), and the tweeter the leading edge of all that came before them (fastest). Note that 'fullrange' drivers have built in mechanical XOs so are self contained multiple discrete BW systems.
From this it's obvious that the woofer section is by definition 'slow' because the WLs are long and all of the leading edge and middle harmonics that defines its 'speed' are being reproduced by other systems. To say a typical sub that's BW limited to ~3 octaves is 'fast' is at first glance not only technically incorrect, it's just plain ludicrous, hence some folk's brutal rebuttals.
Factor in our falling hearing acuity with decreasing frequency and when tested outdoors well away from any boundaries it's very hard for most folks to hear any difference between various BW limited sub systems that have wildly varying Qtc, or even type of cab design, beyond how loud each one is for a given frequency compared to the others.
Still, once these slow/dull sounding systems are confined in an acoustically small space, and even more so when the rest of the LF BW (mids/highs) is added, we sense differences (sometimes major) in these systems that leave most folks 'grasping at air' trying to verbalize them. At this point Mother Nature takes over as even the most technically illiterate innately understands the concept of DC = infinite BW because the more HF BW we hear/feel, the 'fuller' the bass sounds *even if the corresponding fundamentals are missing* and vice versa when the extreme highs are missing from an otherwise super wide BW sound. Even if BW limited at both ends we are 'Happy Campers' if the tonal balance mirrors our speech power response, and why a telephone's very limited BW (~3.3 octaves) sounds sufficiently wide for all but critical listening. Seems our internal sound processor has a very elaborate EQ/synthesizer built into it.
Viewed from this perspective, 'fast' seems the obvious 'catch-all' adjective to define the system's ability to sound tonally balanced, i.e. ~accurately reproducing the signal from top to bottom, however wide or narrow it may be (within reasonable limits of course).
Being a 'catch-all' word like 'clean', 'muddy', etc., and factoring in that folks differ as to how they perceive certain sonic attributes of a system it can mean timing to one person, phase to another, a rising response to another, excessive comb filtering between discrete systems, etc., though really it's all of them, with only the perceived importance of each shifting among them based on our physical/emotional make-up.
So we understand in general what someone is trying to tell us about a system's accuracy, but don't have a clue what they're specifically referring to unless they further define whatever adjective they're using to describe their subjective feeling of how 'right' or 'wrong' it sounds, ergo lacking this info we naturally 'weight' it based on our own perceptions, which can be poles apart from what the author intended to convey.
Little wonder then that folks can get into extremely venal 'debates' over a phrase such as 'fast bass' when no narrowly defined definition can be agreed upon due to it being at once ludicrous and technically correct when the audio system is being reviewed both as a whole and as a collection of interconnected discrete systems, with the room's impact usually being an unaccounted for 'wild card'.
As always though, YMMV and "it's just my opinion, I could be wrong" (after Dennis Miller).
GM
argo said:
The fast start (attack) is handled by the mains.
Bass notes typically stop (decay) much more slowly than loudspeaker is capable of starting and stopping. Reverberation in the room also continues long after the loudspeaker has stopped responding to the program source.
A loudspeaker that stops as quickly as possible without overshoot has a Qts of 0.5. A few months ago I read some heebie jeebie on a website and got all excited about building a subwoofer with a Qts of 0.5. The whole concept turned out to be so much bunk. A sub with a Qts of .7 or even 1.0 is plenty quick enough.
From what I've been able to learn over the last few months, a good subwoofer is one that has low distortion and is capable of moving enough air for the program material and listening room. If the sub has nasty breakup modes in the midrange, as many do, it needs a high order lowpass filter. Probably the most effective thing that can be done to make a sub sound "speedy" is to eliminate room reverberation, or failing that, EQ around it.
GM and Dave, amen and amen.
It's a rare thing to see two consecutive posts on this topic of such high quality.
In support of this, I cite my current 21" bass units on open baffles. Their Qts is somewhere around 1.3 and their cones are large and heavy. Some might say they're the perfect recipe for "slow" bass. Yet, on open baffles, they are things of sonic beauty, truth, and grace. The room intereaction (or relative lack thereof) really is the huge factor.
It's a rare thing to see two consecutive posts on this topic of such high quality.
In support of this, I cite my current 21" bass units on open baffles. Their Qts is somewhere around 1.3 and their cones are large and heavy. Some might say they're the perfect recipe for "slow" bass. Yet, on open baffles, they are things of sonic beauty, truth, and grace. The room intereaction (or relative lack thereof) really is the huge factor.
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