We hear a lot about 'fast bass' and 'floppy bass'. It sounds odd to me that sometimes the 'floppy bass' comment is about speakers with good specs. So can we not see the specs and determine if the bass will be 'fast ' or not?
Reflex enclosures (ducted) may be a bit more difficult to analyse with respect to 'fast' bass.
Sealed enclosures should be easier to check out.So a driver with good mechanical and electrical damping should be able to produce 'fast bass' in a suitable enclosure (say Qtc = 0.5 to 0.6 ).
The Q after all is a measure of the transient response of the driver which in turn tells us how the bass will be.
So can we say that a driver with say :
Fs = 28Hz
Qms=1.69
Qes=0.41
(Qts=0.33)
In a suitable box we could get a Qtc of 0.6 and so should have 'fast bass'.
So I would conclude that this driver must be improperly used if it produces 'floppy bass' in a sealed enclosure.Reflex enclosures are much harder to work with.
The other comment that I would like to make is that it would be good to get a bass driver with low Qms because that is the inherent mechanical damping of the driver itself . This means that this driver ( also with an overall low Qts!)compared to a driver with say a Qms of 3.6 would sound 'faster' even if the external connecting wire and output impedance of the amp were high at say 1 ohm ! The reason being that it (Qms) contributes more to the overall Qts/Qtc and so is not affected as much by the external contributors to the overall Q of the system. The external factors generally increasing Q and making it more 'floppy'.
I base this view on the very tight bass that I have heard from subs with very low Qms ( in a suitable sealed box of course). The electronics was solid state and quite dated.
Any comments?
Reflex enclosures (ducted) may be a bit more difficult to analyse with respect to 'fast' bass.
Sealed enclosures should be easier to check out.So a driver with good mechanical and electrical damping should be able to produce 'fast bass' in a suitable enclosure (say Qtc = 0.5 to 0.6 ).
The Q after all is a measure of the transient response of the driver which in turn tells us how the bass will be.
So can we say that a driver with say :
Fs = 28Hz
Qms=1.69
Qes=0.41
(Qts=0.33)
In a suitable box we could get a Qtc of 0.6 and so should have 'fast bass'.
So I would conclude that this driver must be improperly used if it produces 'floppy bass' in a sealed enclosure.Reflex enclosures are much harder to work with.
The other comment that I would like to make is that it would be good to get a bass driver with low Qms because that is the inherent mechanical damping of the driver itself . This means that this driver ( also with an overall low Qts!)compared to a driver with say a Qms of 3.6 would sound 'faster' even if the external connecting wire and output impedance of the amp were high at say 1 ohm ! The reason being that it (Qms) contributes more to the overall Qts/Qtc and so is not affected as much by the external contributors to the overall Q of the system. The external factors generally increasing Q and making it more 'floppy'.
I base this view on the very tight bass that I have heard from subs with very low Qms ( in a suitable sealed box of course). The electronics was solid state and quite dated.
Any comments?
I think it has a lot to do with enclosures... Passive radiator enclosures sound really smeared to me. Right now I'm listening to a pair of ported studio monitors that respond down to 45hz (not terribly low, but with room gain, not bad) and when I want faster or tighter bass, I just plug the ports with socks 
It really works. It also cuts off the LF response so if I want to use a subwoofer and make my total SPL go up, I can.
I've heard really good things about dipole subs, and I'm about to build one (today or tomorrow, I think) so I'll let you know what results I get.
It really works. It also cuts off the LF response so if I want to use a subwoofer and make my total SPL go up, I can.I've heard really good things about dipole subs, and I'm about to build one (today or tomorrow, I think) so I'll let you know what results I get.
I too agree that it has to do mostly with the enclosure.
I was just about to say that dipoles seem to have very "fast" bass, some may think this because they roll off at quite a high frequency. But if you use equilization to keep them flat 'til the really low frequencies, you'll see just how "fast" and "tight" dipole bass can be.
I was just about to say that dipoles seem to have very "fast" bass, some may think this because they roll off at quite a high frequency. But if you use equilization to keep them flat 'til the really low frequencies, you'll see just how "fast" and "tight" dipole bass can be.
OK guys. Some terminology. Fast is not an appropriate term for trying to describe what you are trying to describe (use that term over on the basslist and expect to be buried under a firestorm of responses). Fast is really a frequency thing. HF can be fast, low frequencies not. For a bass driver to be "fast" it has to be very extended range, and then it still is not the bass that is fast.
What you are trying to describe is an ability to accelerate (ie control), and a lack of group delay.
dave
What you are trying to describe is an ability to accelerate (ie control), and a lack of group delay.
dave
Transient attack
I think we all agree that it is partly the HF element of the bass note that contributes to the bass sounding 'tight' or 'fast'.
So the part of the system that reproduces the HF part of the bass note must do it accurately and aslo be accurate in 'time'.
That will be done by the rest of the system - mids and tweeter.
Even if that is OK the bass driver will still have to be very good at 'starting' and stopping'. That I guess will be the mechanical equivalent of 'slew rate'. This factor I have never seen measured (as "mm/second"). The bass driver will have to slew only as fast as the fundamental note in the bass ( say 40Hz) . But the bass note ( of say the drum ) has a very sharp rise time and is faster than the slew rate for the 40Hz signal. That will be the HF part of the bass note and it will be filtered out ( in the crossover) and fed to the rest of the system. This must add with the fundamental note eventually without any time delay. Only then will the bass note have the attack of the original signal.
So 'tight' bass needs a very competently designed bass AND HF section with great attention to time delays in each section. This is also why simple crossovers (6db/octave) used with good drivers have very good transient attack in the bass.
So after getting good drivers it will be quite difficult to make a 'good' crossover to ensure that you do not loose out on the capabilities of the speaker - due to time smear . You could get a flat frequency response over the band but will it stand up to a coherent transient signal ? That will determine the 'tight' bass and other finer details of the image.
Suddenly the crossover looks far more difficult that it appeared to be ?
Cheers.
I think we all agree that it is partly the HF element of the bass note that contributes to the bass sounding 'tight' or 'fast'.
So the part of the system that reproduces the HF part of the bass note must do it accurately and aslo be accurate in 'time'.
That will be done by the rest of the system - mids and tweeter.
Even if that is OK the bass driver will still have to be very good at 'starting' and stopping'. That I guess will be the mechanical equivalent of 'slew rate'. This factor I have never seen measured (as "mm/second"). The bass driver will have to slew only as fast as the fundamental note in the bass ( say 40Hz) . But the bass note ( of say the drum ) has a very sharp rise time and is faster than the slew rate for the 40Hz signal. That will be the HF part of the bass note and it will be filtered out ( in the crossover) and fed to the rest of the system. This must add with the fundamental note eventually without any time delay. Only then will the bass note have the attack of the original signal.
So 'tight' bass needs a very competently designed bass AND HF section with great attention to time delays in each section. This is also why simple crossovers (6db/octave) used with good drivers have very good transient attack in the bass.
So after getting good drivers it will be quite difficult to make a 'good' crossover to ensure that you do not loose out on the capabilities of the speaker - due to time smear . You could get a flat frequency response over the band but will it stand up to a coherent transient signal ? That will determine the 'tight' bass and other finer details of the image.
Suddenly the crossover looks far more difficult that it appeared to be ?
Cheers.
I don't know the reason for this, but I am experiencing very clean "fast" bass with a very old Electro-Voice 12" inch fullrange driver (LS-12) in an open baffle. When played without the subs, it is "faster" sounding then any box speaker or multi-speaker I've ever owned above 60 Hz (and I've owned a bunch). I have four bass drivers on each baffle surrounding the EV's (two 12" and two 10") that, when turned on, extend the bass below about 80 Hz without sounding a bit slower. The EV's specs aren't that impressive, and the bass drivers are just old mis-matched units I had laying around. The bass drivers are boosted quite a bit. The bass drivers that I have used in regular boxes didn't sound this "fast". When put in the OB and coupled with the EV fullranger, they become different speakers altogether. Part of it may be the EV with no crossover, but I suspect that much of it is due to the open baffle. It's an example of the sum being greater then the parts.
I'd suggest everyone should experiment with open baffle bass sometime (not to mention the great mids that OB has).
Dave
My site
http://www.geocities.com/the_hurdy_gurdyman/
I'd suggest everyone should experiment with open baffle bass sometime (not to mention the great mids that OB has).
Dave
My site
http://www.geocities.com/the_hurdy_gurdyman/
Re: Transient attack
We're still not there yet. A fast risetime 40 Hz note will be divided by the xover network: the fundamental (plus maybe 2nd, part of 3rd harmonic) will be routed to the bass driver, the attack/release edge will be routed to the mid/tweeter.
If you simulate a 40Hz burst through a say 1kHz lowpass, you will see that the sharp edges at the start and stop points are rounded: there is no need for the bass driver to start/stop quickly, because that part of the signal is not getting to it. That is what the xover is for.
Jan Didden
ashok said:
We're still not there yet. A fast risetime 40 Hz note will be divided by the xover network: the fundamental (plus maybe 2nd, part of 3rd harmonic) will be routed to the bass driver, the attack/release edge will be routed to the mid/tweeter.
If you simulate a 40Hz burst through a say 1kHz lowpass, you will see that the sharp edges at the start and stop points are rounded: there is no need for the bass driver to start/stop quickly, because that part of the signal is not getting to it. That is what the xover is for.
Jan Didden
Assume that we are playing a pure tone of, say, 50Hz through two different bass drivers - no tweeters, no crossovers.
If the tone generator is switched off do both bass drivers come to an immediate stop? Do they both stop at the same time?
If the tone generator is then switched on again, do both drivers instantaneously produce the tone? Do they each produce the tone at precisely the same moment?
Surely Newton's laws apply to drive units. A cone cannot instantaneously go from stationary to full harmonic motion, nor can it instantly come to a halt. Cone acceleration and deceleration are both functions of the cone's moving mass and the forces acting upon that mass.
Am I missing something obvious here or will some bass drivers sound "faster" than others depending on their ability to accelerate and decelerate?
Steve
If the tone generator is switched off do both bass drivers come to an immediate stop? Do they both stop at the same time?
If the tone generator is then switched on again, do both drivers instantaneously produce the tone? Do they each produce the tone at precisely the same moment?
Surely Newton's laws apply to drive units. A cone cannot instantaneously go from stationary to full harmonic motion, nor can it instantly come to a halt. Cone acceleration and deceleration are both functions of the cone's moving mass and the forces acting upon that mass.
Am I missing something obvious here or will some bass drivers sound "faster" than others depending on their ability to accelerate and decelerate?
Steve
Steve and Jan
A test with a tone burst would be quite a stringent one. Such a signal would not exist in nature at all (luckily, since no speaker would pass this test with flying colours !).
From the signal-processing point of view bursts etc are the result of the multiplication of sinusoids with step functions.
Many people tend to perceive bass as fast if the real lower end is missing, if for instance you hear only the initial transient of a bass drum and the rest is completely missing due to a high cutoff frequency!
IMO since there is no fast bass you don't need fast bass drivers !
Regards
Charles
A test with a tone burst would be quite a stringent one. Such a signal would not exist in nature at all (luckily, since no speaker would pass this test with flying colours !).
From the signal-processing point of view bursts etc are the result of the multiplication of sinusoids with step functions.
Many people tend to perceive bass as fast if the real lower end is missing, if for instance you hear only the initial transient of a bass drum and the rest is completely missing due to a high cutoff frequency!
IMO since there is no fast bass you don't need fast bass drivers !
Regards
Charles
Stringent it may be, Charles, but the example of square waves being comprised of a series of harmonics, most of which are not handled by the bass driver, is also a stringent one.phase_accurate said:
Certainly the higher frequencies are filtered out of the signal to the bass driver and handled by mid-range units and/or tweeters.
Even so, what remains unfiltered must be handled by the bass driver. This driver 'sees', in real music reproduction, a waveform where the amplitude and the frequency both vary with time.
Surely some bass drivers will follow this pattern of varying amplitude and frequency closer than others.
Is this correct or is there an error in my logic somewhere?
Steve
Haven't we forgotten something?
Reading through this thread again it strikes me that we've omitted something very important.
We've mentioned that various elements are required for the bass of a system to be considered fast:
- The integration of mid and/or high frequency drivers and crossover
- The bass units themselves
- The enclosure
Of course the rest of the system will also play its part in the perception of bass speed.
However, the most important element for most systems is the room. In the wrong room, the resonances will ensure that no speaker system can be perceived as having a fast bass. Dipole bass systems are often perceived as faster simply because they excite less of the room resonances.
Thought it should be mentioned.
Steve
Reading through this thread again it strikes me that we've omitted something very important.
We've mentioned that various elements are required for the bass of a system to be considered fast:
- The integration of mid and/or high frequency drivers and crossover
- The bass units themselves
- The enclosure
Of course the rest of the system will also play its part in the perception of bass speed.
However, the most important element for most systems is the room. In the wrong room, the resonances will ensure that no speaker system can be perceived as having a fast bass. Dipole bass systems are often perceived as faster simply because they excite less of the room resonances.
Thought it should be mentioned.
Steve
To mee this seems logic als well.
We just have to know what the spectrum of a music signal vs time looks like.
IMO ANY spectral part of a music signal is having a rising amplitude at the beginning and a decay at the end. The higher the frequency the faster the initial buildup of the signal component.
For low organ notes you can distinguish quite clearly, by listening carefully, how the sounds start with a "pffff..." (didn't know a decent way to describe this) before the LF content is built up.
Regards
Charles
Some thoughts.
7V, you are right about the start and stop speed. Since the drive units have mass and a motor with finite power , it is obvious that it will take time to start moving . To see this we would have to feed a step impulse to the speaker. Both drivers should behave differently if they are mechanically and /or electromagnetically different. Some bass drivers which are slow to respond will not be able to reproduce the initial part of the waveform accurately. This should result in a loss of information in the bass note.
Additionally all the harmonics that are associated with the bass should be reproduced accurately in time , so that they add up to give the same signal as the original. So smaller bass drivers should in theory be better placed to produce tight bass as compared to very large woofers ( assuming they have
a low resonant frequency) . BUT if the very large bass driver has a whopping magnetic assembly
( magnetic field) and an appropriate voice coil (totally the BL factor I think ) , there should be no reason why it cannot produce tight bass also.
There is tight bass in music. That's the thing that hits you in the stomach and gives you goose bumps !
Many drivers/systems are not capable of reproducing this . Once you hear it you will miss it in every other system that cannot reproduce it. And so, happily , the DIY trail goes on ..............................
Cheers.
Joe Dirt, that crack about the car speaker was great!
7V, you are right about the start and stop speed. Since the drive units have mass and a motor with finite power , it is obvious that it will take time to start moving . To see this we would have to feed a step impulse to the speaker. Both drivers should behave differently if they are mechanically and /or electromagnetically different. Some bass drivers which are slow to respond will not be able to reproduce the initial part of the waveform accurately. This should result in a loss of information in the bass note.
Additionally all the harmonics that are associated with the bass should be reproduced accurately in time , so that they add up to give the same signal as the original. So smaller bass drivers should in theory be better placed to produce tight bass as compared to very large woofers ( assuming they have
a low resonant frequency) . BUT if the very large bass driver has a whopping magnetic assembly
( magnetic field) and an appropriate voice coil (totally the BL factor I think ) , there should be no reason why it cannot produce tight bass also.
There is tight bass in music. That's the thing that hits you in the stomach and gives you goose bumps !
Many drivers/systems are not capable of reproducing this . Once you hear it you will miss it in every other system that cannot reproduce it. And so, happily , the DIY trail goes on ..............................
Cheers.
Joe Dirt, that crack about the car speaker was great!
FFT of a drum signal
Hi all,
I tried to get an FFT of a Drum note that I know sounds VERY tight in my system. The mathematically obtained FFT from the wav file of the drum note i snot too easy to interpret as a lot of very low amplitude ( below -45db wrt to the highest frequency) signals are there. The drum note also does not have any other musical instrument in the background.
24Hz -45db
46Hz -16.4db
67 Hz 0db
94Hz -11.8db
135Hz -28db
164 Hz -45db
Higher frequencies were much lower in level.
Where does this lead us ?
Cheers.
Can I upload a wav file ( of the drum note ) zipped ? What is the file size limit ?
Hi all,
I tried to get an FFT of a Drum note that I know sounds VERY tight in my system. The mathematically obtained FFT from the wav file of the drum note i snot too easy to interpret as a lot of very low amplitude ( below -45db wrt to the highest frequency) signals are there. The drum note also does not have any other musical instrument in the background.
24Hz -45db
46Hz -16.4db
67 Hz 0db
94Hz -11.8db
135Hz -28db
164 Hz -45db
Higher frequencies were much lower in level.
Where does this lead us ?
Cheers.
Can I upload a wav file ( of the drum note ) zipped ? What is the file size limit ?
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