Faster Bass

[Hoerninger]

Regularly I read about "faster bass" and I do not understand it.
Is meant "slew rate", a subjective description or something else? :confused:
Thank you in advance.
____________
Peter

[herki the cat]

Regularly I read about "faster bass" and I do not understand it.
Is meant "slew rate", a subjective description or something else? :confused:
Thank you in advance.
____________
Peter

herki:
Fast bass originally refered to good transient response in the bass spectrum. Today it is up for grabs. I think that many listeners yearn for realistic sounding bass which is difficult to achieve with all the complexity encurred with speaker enclosures. Try listening to a 2245 sub laying bare on its back on the rug on the floor with zero enclosure__it has an incredibly clean sound at 20 Hz on a simple frequency sweep from an audio generator; it is a sound like real pipe organ pedals.

[1audiohack]

Hi Peter;

Slew rate is posatively an objective measurement. Let's see if I can get this right without the aid of a text book, in electronics like an amplifier, slew rate defines the ability of the amp to track rapid transients like square waves. I think (electronics are not my speciality) the metric is votage rise in microseconds i.e., how fast can it switch before the vertical portion of the square wave becomes distorted like saw toothed or rounded.

One could also measure a speakers ability to track impulse type transients with a position detecting device such as a laser and the metric could be distance in microseconds. If you had the amp output on ch1 of a scope and the cone position via the laser on ch2 of the scope the picture is not a pretty one. I have done this and I haven't gotten over it yet! Combine this with delay distortion and you're just getting started.

This is a subject with some interesting and counterintuitive twists. Before I type a ton, is this the road you're on?

[jcrobso]

Hi Peter;

Slew rate is positively an objective measurement. Let's see if I can get this right without the aid of a text book, in electronics like an amplifier, slew rate defines the ability of the amp to track rapid transients like square waves. I think (electronics are not my specialty) the metric is voltage rise in microseconds i.e., how fast can it switch before the vertical portion of the square wave becomes distorted like saw toothed or rounded.

One could also measure a speakers ability to track impulse type transients with a position detecting device such as a laser and the metric could be distance in microseconds. If you had the amp output on ch1 of a scope and the cone position via the laser on ch2 of the scope the picture is not a pretty one. I have done this and I haven't gotten over it yet! Combine this with delay distortion and you're just getting started.

This is a subject with some interesting and counter intuitive twists. Before I type a ton, is this the road you're on?

Slew rate is how long it takes the output to change in response to a change in the input.

For speakers how long does it take the cone to start moving after a voltage is applied the terminals.

Many bass players prefer 4-10" speakers over a 15" because they feel the get better transit response this way.

[scott fitlin]

Slew rate of amp, and drivers transient response affect speed of sound, and ALSO damping factor.

Woofers with very strong motors and LOW MASS underhung coils with lighter weight cones than is the norm today, had FAST acceleration. An amps ability to rise quickly to input signal is also at play, but damping factor determines how quickly the amp pulls the woofer cone back after the signal hits the woofer.

[1audiohack]

Woofers with very strong motors and LOW MASS underhung coils with lighter weight cones than is the norm today, had FAST acceleration. An amps ability to rise quickly to input signal is also at play, but damping factor determines how quickly the amp pulls the woofer cone back after the signal hits the woofer.


Yup and they (big motor / light cone / small series L) "woofers" sound fast in large because they have an upward sloped non flat frequency response because they become mass dominated at higher frequencies than their higher moving mass large series L cousins. The light ones are just way down in volume at very low frequencies where they also have increasing group delay, you don't hear it as much, its the lack of low frequency components that make it sound "fast".



jcrobso Your right on!

Wow, thanks!

[scott fitlin]

Which, for me, is why the combination of ALTEC 15,s with JBL 2240 18,s worked so very well.

[1audiohack]

Zactly.
Now if you get into the acoustic phase portion you find that the acoustic center of the driver usually retreats from you as the frequency goes lower. I have some GTI1800's that with the driver group delay added to the delay caused by the vented box, the measured acoustic center is more than 11 feet behind the E130 (with felt dust caps) mid bass driver at 30Hz. If that is not partially corrected by delaying the rest of the system, you hear the mallet or stick hit a kick drum or floor tom through the mids and tweets followed by a whuumph from the sub, and naturally you say, "That is slow bass!" If you lead by a small amount the big lump (as captured in an ETC measurement) caused by the sub to come close to peak with the much sharper peaked mid bass you get much tighter, "faster" bass.

[scott fitlin]

Zactly.
Now if you get into the acoustic phase portion you find that the acoustic center of the driver usually retreats from you as the frequency goes lower. I have some GTI1800's that with the driver group delay added to the delay caused by the vented box, the measured acoustic center is more than 11 feet behind the E130 (with felt dust caps) mid bass driver at 30Hz. If that is not partially corrected by delaying the rest of the system, you hear the mallet or stick hit a kick drum or floor tom through the mids and tweets followed by a whuumph from the sub, and naturally you say, "That is slow bass!" If you lead by a small amount the big lump (as captured in an ETC measurement) caused by the sub to come close to peak with the much sharper peaked mid bass you get much tighter, "faster" bass.I use TAD 15,s now, and although they don't have a peaky midrange response like the Altecs did, they do seem to have good transient snap, as well as a natural tone, especially in the vocal range, and TOM TOMS and SNARES sound. JBL still rules most of my 18in applications, and the 2240H still has snappy kick, and decent deep low end, in a rear horn loaded configuration.

My center stack ported 2242 subs, these sound great, but on one brand of amplifier, sound sort of slow and a bit plodding to me, YET, switch to Crown amps, and WOW, what a difference in speed and tightness! Crown has always been known for a tight, kick ass bottom end, and now as was then, is no different.

IT WORKS! :D

[herki the cat]

Zactly.

Now if you get into the acoustic phase portion you find that the acoustic center of the driver usually retreats from you as the frequency goes lower. TI1800's driver group delay plus the delay caused by the vented box yields measured acoustic center more than 11 feet behind the E130 (with felt dust caps) mid bass driver at 30Hz, & you hear the mallet or stick hit a kick drum or floor tom followed by a whuumph from the sub, and naturally you say, "That is slow bass!"...1audiohack

herki's two cents:
quote: 1audiohack="you hear the mallet or stick hit a kick drum or floor tom followed by a whuumph!, due to speaker system group delay." Of course you already know, the same thing happens with a snare drum; you hear the hi-frequency stick-snap followed by the delayed low-frequency slower thump-component.


The delay problem is significantly aggrevated beyond the the speaker system group delay mess, by conventional speaker wires of any gauge, according to Mr. Bruce Brisson , CEO of MIT Interface Technologies, who explains in his patents, that due to group delay in simple conductors, the audio-signal magnet-field physically moves towards the center of the conductor in a manner "inversely proportional to the audio frequency, acting like frequency sensitive-change of distributed inductance in the conductor, say, from 20,000 Hz down to 10 Hz or so.

Simply stated, group delay in speaker cables and interconnects, results in progressively altering the transmission velocity of audio signals in a manner inversely propositional to frequency in the entire audio spectrum, so these audio signals of different frequencies do not arrive at the end of the pipe coherently together at the same time, and this really screws up pase linarity and creates phase distortion__two different entities which spoil the ability to transport the recording studio's "extremely complex SPL and phase related " reverberation components in their original state by corrupting the signal before it arrives at the loud speaker.

[eso]

... its the lack of low frequency components that make it sound "fast".


Now, you've had the Big Bottom around for a bit and you say it lacks low-frequency components?

"Fast" is a subjective term, and transient response is one part of it, but decay is equally as important to me. That is why I so dislike most ported enclosures: the cabinet resonance all-too-often gives a lethargic decay, or "overhang" as I often call it. Not to mention that the port out put is an amplified cabinet resonance, and that equals raised distortion.

Take a good low mass driver and properly horn load it and you will get excellent transient response, very low distortion and no exaggerated decay.

Fast bass=accurate transient response, very low distortion and accurate decay.

eso

[1audiohack]

Now, you've had the Big Bottom around for a bit and you say it lacks low-frequency components?

:blink:

eso

Nope. It is no stretch for me to agree with everything you stated in your post except the above. I was stating my experiences with them used as direct radiators. As you well know, horn loaded is another animal entirely! One of which I am just beginning to understand, but have long appreciated.

As for"Big Bottom" it is not at this time properly loaded i.e., in a room driving into a corner with a ceiling, most likely is not loaded with an ideal driver, and not driven with
an ideal amp. I have never heard it in any other circumstance and while preparing for the Baja 500 and hampered by weeks of high winds I have not been able to spend any meaningfull time with it. BB most certainly has low frequency components. :D