What actually would be interesting is the spectral buildup and decay of such a signal (i.e. it's waterfall plot).
BTW: Why not use a driver that doesn't store energy for the mids and lows, and an ordinary "sluggish" woofer at the low end ?
http://www.manger-msw.com/en/produkte/index.html
Regards
Charles
BTW: Why not use a driver that doesn't store energy for the mids and lows, and an ordinary "sluggish" woofer at the low end ?
http://www.manger-msw.com/en/produkte/index.html
Regards
Charles
I read the first post in the thread where he mentioned Qts and Qtc only to have practically no one else use them in their replying post. I also would agree that an enclosure has much to do with the type of bass you will hear whether it may be floppy or fast. But, I think the original post was asking whether or not the Qtc of an enclosure lends itself to the type of bass you'd hear in the end. So, fast bass would be trasient perfect (T.P.), is T.P.=Qtc=1.0? I know that increasing enclosure volume will decrease Qtc while, decreasing volume will increase Qtc. {Inversely proportional}. Does anyone know what sound to expect between certain ranges (if any) of Qtc?
-TIA, Bose(o)
-TIA, Bose(o)
Q parameters.
Hi Bose(o),
I did expect some discussion with the driver and enclosure parameters but no one seems to want to do that.
IIRC a Q of 0.5 is transient perfect and a Q of 0.6 is acceptable. The catch here is that usually most systems with 0.5 or 0.6 will have a higher f -3db at low frequency than we want. With very large drivers with a Fs of 15 Hz or so this might not apply I guess.
This might also need very large boxes that most of us cannot have.
I would like a -3db point at about 30 Hz or max 40 Hz. With room gain this is possible. How would this ( room gain ) affect the Q of the overall acoustic signal we hear ?
Does anyone have the TS parameters of the 12 inch woofer used in the great Dovedale kit from Wharfedale ?
Cheers.
In my earlier post I was suggesting that we look closely at the Qms of the driver to determine if we can get tight bass from that unit. This of course cannot be looked at in isolation.
I am using a Peerless 12 inch in a box with a Qtc of about 0.6. It does sound tighter than it did with a Qtc of 0.77. Location is about the same as I used earlier.
Hi Bose(o),
I did expect some discussion with the driver and enclosure parameters but no one seems to want to do that.
IIRC a Q of 0.5 is transient perfect and a Q of 0.6 is acceptable. The catch here is that usually most systems with 0.5 or 0.6 will have a higher f -3db at low frequency than we want. With very large drivers with a Fs of 15 Hz or so this might not apply I guess.
This might also need very large boxes that most of us cannot have.
I would like a -3db point at about 30 Hz or max 40 Hz. With room gain this is possible. How would this ( room gain ) affect the Q of the overall acoustic signal we hear ?
Does anyone have the TS parameters of the 12 inch woofer used in the great Dovedale kit from Wharfedale ?
Cheers.
In my earlier post I was suggesting that we look closely at the Qms of the driver to determine if we can get tight bass from that unit. This of course cannot be looked at in isolation.
I am using a Peerless 12 inch in a box with a Qtc of about 0.6. It does sound tighter than it did with a Qtc of 0.77. Location is about the same as I used earlier.
7V said:
You are right, but the point is that in an actual installation this does not happen. There are the xover and mid/tweeter, and they will receive the fast edges. Both woofers in your example will only receive the signal components below the xover frequency (simplified, I know, but the principle is OK), so they are never required to start/stop instantaneously.
Jan Didden
punchier bass, a recepy
choose a woofer with:
a) lightweight cone
b) powerfull magnet (big BL)
c) little coil diameter (some altec, e-voice, beyma, RCF..)
d) fs>45 Hz, not a long-trow type
Often these units are 'misused' (abused) in PA and wrongly catalogued as not reliable because these are extended range woofers, not made for the purpose of extended bass response in the low frequencies, but just the opposite: covering also the low-midrange.
Put them in:
a) closed enclosure without too much filling.(Qtc<0.7)
or
b) a little reflex enclosure with relatively big reflex port.
or
c) short horns (JBL, VOT,community,...)
DON'T try too get 40 Hz at -3dB out of these things, 65 to 80 Hz will be your target, and use another specialized woofer for those earth-shaking sounds.
So DON'T touch that bass-boost or other equalizer, loudness thingy...
PS most of the cheap offers often have nearly the same specifications as mentioned above (at first glance) but fabrication quality is poor.
Good 15 inchers for this purpose are rare these days (due to the abuse many make of them, difficult for the manufacturers to make them fool-proof without touching on the essential parameters, so better no product than a 'bad-name' product).
12 inchers are more available in this class.
Not an absolute solution but it works for me
choose a woofer with:
a) lightweight cone
b) powerfull magnet (big BL)
c) little coil diameter (some altec, e-voice, beyma, RCF..)
d) fs>45 Hz, not a long-trow type
Often these units are 'misused' (abused) in PA and wrongly catalogued as not reliable because these are extended range woofers, not made for the purpose of extended bass response in the low frequencies, but just the opposite: covering also the low-midrange.
Put them in:
a) closed enclosure without too much filling.(Qtc<0.7)
or
b) a little reflex enclosure with relatively big reflex port.
or
c) short horns (JBL, VOT,community,...)
DON'T try too get 40 Hz at -3dB out of these things, 65 to 80 Hz will be your target, and use another specialized woofer for those earth-shaking sounds.
So DON'T touch that bass-boost or other equalizer, loudness thingy...
PS most of the cheap offers often have nearly the same specifications as mentioned above (at first glance) but fabrication quality is poor.
Good 15 inchers for this purpose are rare these days (due to the abuse many make of them, difficult for the manufacturers to make them fool-proof without touching on the essential parameters, so better no product than a 'bad-name' product).
12 inchers are more available in this class.
Not an absolute solution but it works for me
Transients in bass drivers.
Not instantaneously .....but .......
Well the bass driver may not have to stop suddenly but if it is not already producing some other bass notes , a drum note starts very fast and even if we take the fundamental note only, it will be a start from a 'stopped' position. With high level signals it can be a very fast start. Not comparable to the tweeter of course.
Most of our transients do die down relatively slowly but there are some where the decay can be very fast.
In complex waveforms the downward wave (tending to zero) could be VERY fast due to complex addition of the other waveforms. This is a very complex situation and the bass driver will have to respond correspondingly.If it does not we will have spurious signals generated due to the error. Lots of low level behaviour is very hard to analyse but easy to hear. So I guess we should be very meticulous when choosing drivers and that does not guarantee that we have got it all right.
"Men may come and men may go - but DIY hi-fi goes on forever"
Cheers,
Ashok.
Not instantaneously .....but .......
Well the bass driver may not have to stop suddenly but if it is not already producing some other bass notes , a drum note starts very fast and even if we take the fundamental note only, it will be a start from a 'stopped' position. With high level signals it can be a very fast start. Not comparable to the tweeter of course.
Most of our transients do die down relatively slowly but there are some where the decay can be very fast.
In complex waveforms the downward wave (tending to zero) could be VERY fast due to complex addition of the other waveforms. This is a very complex situation and the bass driver will have to respond correspondingly.If it does not we will have spurious signals generated due to the error. Lots of low level behaviour is very hard to analyse but easy to hear. So I guess we should be very meticulous when choosing drivers and that does not guarantee that we have got it all right.
"Men may come and men may go - but DIY hi-fi goes on forever"
Cheers,
Ashok.
Re: Some thoughts.
Hmm...
A transient at 50Hz can be, by the laws of physics, no faster than 50Hz. Anything faster, by nature is a higher frequency
Correct
IMHO, as was stated earlier, so called fast bass is usually due to a peak in response at between 80 and 120Hz. This can be caused by box design, driver or crossover response/problems, or IM products in cones,
ashok said:
Hmm...
A transient at 50Hz can be, by the laws of physics, no faster than 50Hz. Anything faster, by nature is a higher frequency
Correct
IMHO, as was stated earlier, so called fast bass is usually due to a peak in response at between 80 and 120Hz. This can be caused by box design, driver or crossover response/problems, or IM products in cones,
Lieven, I think your right here, and I also think thats the reason why the passlabs Rushmore has a 11 inch driver and a 15 inch driver.
http://www.passlabs.com/images/product/rushmore-poster.jpg
I think that low x-max high efficiency lightweight but rigid cone speakers with enormous BL would be best for that 'fast' bass.
And I dont know how rigid that cone is but the 80cm fostex woofer could probably do the job
Also would a very high order crossover help?
http://www.passlabs.com/images/product/rushmore-poster.jpg
I think that low x-max high efficiency lightweight but rigid cone speakers with enormous BL would be best for that 'fast' bass.
And I dont know how rigid that cone is but the 80cm fostex woofer could probably do the job
Also would a very high order crossover help?
agree with ashok's view
http://www.diyaudio.com/forums/showthread.php?postid=58343#post58343
similar subject.
http://www.diyaudio.com/forums/showthread.php?postid=58343#post58343
similar subject.
I am beggining to see that maybe "fast bass" is related to the "resolution" of the driver. If the driver, due to poor design/construction, can not respond to the CHANGES in the electrical current applied to it quickly enough, then perhaps some musical information is "eaten up". Thus when the musical program dictates to "play" silence, the driver is still playing a note (smearing into the next note). I think that this is somehow related to the inductance of the voice coil (Le). Unfortunately, when I tried to research this, it ended up being completely counter intuitive. I though that the lower the inductance (Le), the quicker the driver (or the driver is capable of a higher resolution). Then people at this site suggested that a higher Le is actually better for bass driver, and I did not get a chance to look into it further, so if someone can elaborate on how Le relates to all this, it would be great.
As far as a higher order crossover impacting the smearing and group delay... seems like this can be solved (or helped) by placing the drivers as close as humanely possible. If the drivers are VERY close, then high order crossovers seem logical. What do you think? I am glad I am not the only one preocupied with this at times that I should really be sleeping.
As far as a higher order crossover impacting the smearing and group delay... seems like this can be solved (or helped) by placing the drivers as close as humanely possible. If the drivers are VERY close, then high order crossovers seem logical. What do you think? I am glad I am not the only one preocupied with this at times that I should really be sleeping.
amo said:
I am beginning to see that no matter how much information is provided, people will refuse to see that there is no such thing as fast bass.
One more time: the purpose of the xover is to ensure that the bass driver only receives lf parts of the signal. These are relatively slow changing voltage (or current) levels, that the bass driver is able to follow easily. In a properly designed system, the driver is never asked to move faster (or to stop faster) than it can.
Suppose you have a lf burst. The xover will route the lf part to the bass driver, and the fast start/stop parts of the burst to the mid/tweeter. The lf driver will leasurely start and stop, while the mid/tweeter will fill in the fast transients.
Jan Didden
No 'fast' bass?
I think that this statement is probably correct. The term 'fast' or 'tight' bass was used to describe the kind of bass that we get from a percussion instrument with a sharp transient and low frequency fundamental and harmonic frequencies. Typically from drums.
We could possibly say accurate transient bass reproduction! That would be determined not just by the bass driver but by every component in the system , including the power amplifier and the room acoustics! Suddenly things have got pretty complicated- huh?
I think that this statement is probably correct. The term 'fast' or 'tight' bass was used to describe the kind of bass that we get from a percussion instrument with a sharp transient and low frequency fundamental and harmonic frequencies. Typically from drums.
We could possibly say accurate transient bass reproduction! That would be determined not just by the bass driver but by every component in the system , including the power amplifier and the room acoustics! Suddenly things have got pretty complicated- huh?
Re: No 'fast' bass?
Exactly. If you limit it to the speaker system, accurate reproduction of say a bass transient requires the cooperation of the whole speaker system, the lf driver to reproduce the powerfull lf component and the tweeter to take care of the transient parts. Preferable everthing in correct phase relationships, of course.
Jan Didden
ashok said:
I think that this statement is probably correct. The term 'fast' or 'tight' bass was used to describe the kind of bass that we get from a percussion instrument with a sharp transient and low frequency fundamental and harmonic frequencies. Typically from drums.
We could possibly say accurate transient bass reproduction! That would be determined not just by the bass driver but by every component in the system , including the power amplifier and the room acoustics! Suddenly things have got pretty complicated- huh?
Exactly. If you limit it to the speaker system, accurate reproduction of say a bass transient requires the cooperation of the whole speaker system, the lf driver to reproduce the powerfull lf component and the tweeter to take care of the transient parts. Preferable everthing in correct phase relationships, of course.
Jan Didden
I'm not sure I understand the question, Steve.
Of course you can present an impulse to a woofer and check its transient response, which will be awfull. But since in real music reproduction the woofer never is asked to reproduce the impuls, the point is moot.
There probably is a phase shift between the woofer driving voltage and it's acoustical output because of the inductive nature of the voice coil (neglecting for the moment the xover part), but a good enclosure present a largely resistive load to the woofer, so the phaseshift may be very small. Not being a speaker expert, maybe some of the cognoscienty in this forum can answer that.
Jan Didden
BTW Great-looking speakers! Are those mid/tweeters Jordans?
Of course you can present an impulse to a woofer and check its transient response, which will be awfull. But since in real music reproduction the woofer never is asked to reproduce the impuls, the point is moot.
There probably is a phase shift between the woofer driving voltage and it's acoustical output because of the inductive nature of the voice coil (neglecting for the moment the xover part), but a good enclosure present a largely resistive load to the woofer, so the phaseshift may be very small. Not being a speaker expert, maybe some of the cognoscienty in this forum can answer that.
Jan Didden
BTW Great-looking speakers! Are those mid/tweeters Jordans?
Don't worry Jan, I'm just playing Devil's Advocate. I'm still having difficulty with the concept that the acceleration/deceleration ability of bass drivers has no relevance to the sound, although I accept your point that the woofer is not required to produce an impulse (unless it's a full-range driver).janneman said:
So let me put forward another hypothetical, and see if someone can help me understand this ...
OK, we've got two woofers that carry the range from 20Hz to 1,000Hz. Without a crossover, one would fall off at around 1,500Hz, the other at 5,000Hz.
Is there no situation where the difference in transient response of these two units can be detected (in their working range of 20-1000)?
Thanks Jan. Hopefully others on this forum will be able to audition them soon so we can have opinions on the sound quality other than mine.
The drive-units are Bandors. They have a free-air resonance of 65Hz and will go beyond 20kHz. I do like a speaker without a crossover in the mid-range.
Steve
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