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Discussion Starter · #1 ·
Can anyone suggest a physical interpretation for the description "tight bass", a term of approbation for subwoofers? More specifically, I'm interested in what it means for a sub crossed over fairly low, so that a musical note at say 40Hz is not going to have any harmonics played by the sub. So, whatever "tight" might mean, it can't have to do with timbre, since that is sounded with harmonics (unless the sub is distorting and producing higher harmonics way above the crossover frequency).
 

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Tight bass is well damped bass. The woofer stops moving quickly after the signal is removed. The opposite would be boomy bass which is what you typically hear from the subs in kids' cars.
 

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Imagine Jenifer Lopez now. Now imagine her 40 years from now. The former is well damped ;)
 

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Quote:
Originally posted by GregLee
Can anyone suggest a physical interpretation for the description "tight bass", a term of approbation for subwoofers? More specifically, I'm interested in what it means for a sub crossed over fairly low, so that a musical note at say 40Hz is not going to have any harmonics played by the sub. So, whatever "tight" might mean, it can't have to do with timbre, since that is sounded with harmonics (unless the sub is distorting and producing higher harmonics way above the crossover frequency).
It's a function of frequency response. (People often talk about woofer damping, but that's actually just another way of talking about its frequency response.) More bass, especially if it comes in a big peak somewhere, will tend to sound fat, whereas less bass will tend to sound tighter, until you get to the point where it starts to sound thin. The primary reason is reduced upward masking, so that upper-bass or midrange sounds can be heard more clearly. Since all the attack information is well up from the bass fundamentals, the bass sounds "quicker," even though it isn't really.
 

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Quote:
Originally posted by GregLee
What's "tight" bass?
Probably the biggest misnomer of hi-fi lore, and the cause for more confusion and completely incorrect assumptions made about design generalizations.


Realize the term comes from audiophiles attempting to verbalize their perceptions. Unfortunately different listeners will often use this term do describe a myriad of different sounds and effects. I strongly suggest the use of less ambiguous terms if you are looking to convey your perceptions more accurately. I like descriptors like immediate, articulate, accurate, clean, unstressed, precise, having less overhang, etc. to describe bass, as such terms are more specific. It is somewhat akin to saying you don't like the taste of something as opposed to saying it is too sweet, sour, bitter, etc. At least in this case some perspective is given and comparative help or suggestions can be offered. Otherwise, it is a random "give this a try..."



Rant over.
 

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Discussion Starter · #6 ·
Quote:
Originally posted by MDRiggs
... The primary reason is reduced upward masking, so that upper-bass or midrange sounds can be heard more clearly. Since all the attack information is well up from the bass fundamentals, the bass sounds "quicker," even though it isn't really.
If the sub's crossover is set low, upper bass or midrange is not going to be played by the sub, so how can it be heard more clearly because of something about the sub's frequency response? What's upward masking?
 

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Discussion Starter · #7 ·
Quote:
Originally posted by Mark Seaton
... I like descriptors like immediate, articulate, accurate, clean, unstressed, precise, having less overhang, etc.....
What do those mean?
 

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Greg,


The term "tight" bass is often used in an attempt to communicate the difference between accurate and distorted bass and is not typically a physical description other than referring to the rapidity in which the driver (speaker) stops moving. An example of well reproduced or "accurate" or "tight" bass would be when a bass drum from say, a typical rock band sounds like one and not like the bass drum from a marching band which is much bigger and has a lower and longer sound. The first one (the rock band bass drum) has a tendency to sound more like a thump and the other (the marching band bass drum) sounds more like a boom. Poorly reproduced or "loose" or "boomy" bass will make the Bass drum from the rock band sound like the bass drum from a marching band or even worse the noise that exudes from the kid's cars that Colm mentioned.


Mark's descriptors;

"... I like descriptors like immediate, articulate, accurate, clean, unstressed, precise, having less overhang, etc..... "

are all terms used to describe accurate bass reproduction. Pick one you like and go with it. I think he was actually talking to the others that answered before him though.


As for your 40hz question....You may want to set the crossover a bit higher. but I'll use it as an example.


All speakers have crossovers to remove unwanted distortion at the bottom and high frequency range limits of each driver in the speaker. Driver= individual bass, mid or tweet in a speaker.


A crossover causes the frequency to be rapidly "rolled off" or lowered in volume to zero for a particular driver. It does not stop the frequency dead in it's tracks. In your main speakers this "roll off" is typically set very near the point in the frequency where the driver (speaker) can no longer reproduce the sound accurately. This means that a speaker with a bottom end rating of 40hz is still reproducing sound at 20hz but at a much lower db level. This is a good thing because the sound is distorted but no sound "cuts off" in the real world so, you would notice if it did just "cut off". Your sub does this too at about the same rate of ascent and descent as the main speakers. So using the example of a 40hz tone, you would need the main speakers to kick in well below 30hz so they can provide the sound and you don't hear the 40hz tone from your sub. (in reality it would have to kick in much lower) Real speakers drop off a bit slower than this example.


An example of a more accurate speaker drop off would be 90db at 100hz down to 60db at 20hz. Some of the best subs go from 60db at 15hz to 90db at 30hz. Even setting the sub crossover at 35hz would create a hole in the sound. In this example you would have a valley in the sound because you would be at 85db at 40hz. That's 5db lower than at 50hz and 30hz and is very audible.


If you look at just about any manufacturers speaker brochure you will see a graph that shows the "roll off" that I'm talking about at the bottom and high end of the frequency range that the speaker produces.


So, "tight" bass might be characterized as a slang term for well reproduced or "accurate" bass and crossovers do not "cut off" the frequency they cause a rapid "roll off" of the volume at a specific frequency being fed to a particular driver.



I hope this helps.


Dan
 

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Quote:
Originally posted by MDRiggs
It's a function of frequency response. (People often talk about woofer damping, but that's actually just another way of talking about its frequency response.) More bass, especially if it comes in a big peak somewhere, will tend to sound fat, whereas less bass will tend to sound tighter, until you get to the point where it starts to sound thin. The primary reason is reduced upward masking, so that upper-bass or midrange sounds can be heard more clearly. Since all the attack information is well up from the bass fundamentals, the bass sounds "quicker," even though it isn't really.
So you are saying a sub with the most bloated bass, whose woofer is so uncontrollable that it rings long after the signal has stopped could achieve tight bass just by equalizing the response until it is flat?
 

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Discussion Starter · #10 ·
Quote:
Originally posted by Dan 41
... The first one (the rock band bass drum) has a tendency to sound more like a thump and the other (the marching band bass drum) sounds more like a boom. Poorly reproduced or "loose" or "boomy" bass will make the Bass drum from the rock band sound like the bass drum from a marching band or even worse the noise that exudes from the kid's cars that Colm mentioned.
That's very clear: what should sound like a thump sounds instead like a boom because the bass is not "tight". But there are two things still unclear to me. One is the connection (if any) between an underdamped cone and boominess. The other concerns the predominate frequencies of a "boom", which intuitively I'd associate with frequencies considerably above the 40Hz note of my example. I find that dialling down my sub's crossover removes boominess, but can this affect the damping of the cone?

Quote:
As for your 40hz question....You may want to set the crossover a bit higher. but I'll use it as an example....
A bit higher than what? I didn't say what I had my crossover set at. I'm just trying to understand what is going on the case where the harmonics of low notes are produced by the mains rather than the subwoofer. Thanks for the discussion of roll off, but I didn't quite get the poiint of it.
 

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Hi Greg,


The "roll off" discussion was an attempt at explaining part of why the distortion you are trying to get rid of occurs.




"One is the connection (if any) between an under-damped cone and boominess."




Under-damped and damped are terms that are widely used, and abused, to explain a portion of why this "boomy" distortion exists. In this case it sounds like the term is used to describe the rapidity in which the cone or "driver" stops moving. Often when a cone is said to be under-damped it will move a lot and continue to move after the desired tone has passed. This causes the sound to be "boomy". If it is over-damped the cone won't move enough causing the sub to sound weak or "thin"(not enough bass). In short the longer the cone moves after the desired tone ceases the more boomy (distorted) the sound will be. In the case of extreme low bass you need a lot of speaker movement because this is what creates the sound pressure. The trick is to get it to stop when the tone does. Damping or under-damping aren't the only things that can cause this problem: improper crossover, insufficient damping material (usually looks like insulation) inside the speaker, poor design, improperly tuned port, bad cone, blown voice coil etc. The list goes on.




"The other concerns the predominate frequencies of a "boom", which intuitively I'd associate with frequencies considerably above the 40Hz note of my example. I find that dialling down my sub's crossover removes boominess, but can this affect the damping of the cone?"




Typically, you're right in saying that you associate this with frequencies above 40hz because that's where it, so often, is and why it can be so annoying. Keep in mind that the cone will dictate how much damping the the speaker will need but damping affects the cone not vise versa.


You may have several different things going on simultaneously that are causing your boominess. Now, I don't want to impugn your equipment here so don't take this as critiquing your sub. I have heard several poorly designed subs that no matter where you set them they sound boomy. Your sub may be "blown" or defective. It should not become boomy here because subs are inherently designed for these frequencies. A good design will incorporate the frequencies between 15hz-150hz inclusive, any boominess here is regarded as unacceptable in my house. Other causes can be too much volume, overlapping the sound of the mains (this is where the crossover discussion helps), sub being "out of phase" or a bad signal. I would check the phase and look at where the "roll off" is of your mains.


When you "dial down" your sub you are changing the crossover frequency (moving the "roll off" point) . This will eliminate overlapping of the main speakers which may be causing your problem.




'A bit higher than what? I didn't say what I had my crossover set at. I'm just trying to understand what is going on the case where the harmonics of low notes are produced by the mains rather than the subwoofer. Thanks for the discussion of roll off, but I didn't quite get the poiint of it."




I must have misunderstood your 40hz statement. I thought you were setting the sub below that point. The point about the "roll off" is that the crossover does not "stop" the sound it causes the dB's to rapidly decrease at a specific frequency in a particular driver. You may want to set the dial on your sub near the "roll off" point of your mains to prevent your "boom".


I hope this clears it up a bit,

Dan
 

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Greg,
Quote:
I find that dialling down my sub's crossover removes boominess, but can this affect the damping of the cone?
It probably has nothing to do with "damping of the cone".


There is something called room modes (room induced frequency modes with peaks and nulls) that is probably causing the boominess you are experiencing.



What you are doing when you lower the sub's crossover frequency (and reduce the boominess) is reducing the output from the sub that reinforces the room's frequency peak created by the combination of your listening position, the sub's position in your room and your room's length, width and height dimensions. This room induced frequency peak causes the boominess.


Many on this forum use parametric EQs with adjustable bandwith or "Q" to tame these room induced frequency peaks in the sub's bass output region and reduce the boominess (I use one called a Behringer BFD 1100Pro).


This is all explained in a book called "Master Handbook of Acoustics" by F. Alton Everest, Fourth edition, if you care to read about it.
 

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Discussion Starter · #13 ·
Quote:
Originally posted by Dan 41
When you "dial down" your sub you are changing the crossover frequency (moving the "roll off" point) . This will eliminate overlapping of the main speakers which may be causing your problem..... You may want to set the dial on your sub near the "roll off" point of your mains to prevent your "boom".
I do set my sub's crossover near the roll off of my mains, and it does prevent the boom, which, as you say, is due to overlapping frequency ranges. I don't have a specific problem I'm trying to cure -- just curious about what "tight" means.


Thank you all for your answers.
 

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To me tight bass means that it follows the music the way it is supposed to be. Although the sound of bass is completely dependent on the source. The bass coming from a Tupac album and a Tears For Fears album are completely different even if played on the same stereo. And likewise a sealed 10" sub will sound great on a Tears For Fears or Suzanne Ciani, but will sound like crap on that Tupoc CD.


Heres one of the ways I have used to decide how accurate my subs are.


I have a CD by Vangelis (excellent for the Hifi, Oceanic especially), called Themes. In the begining and throughout track 10 "Closing Titles from "The Bounty" " there is thunder. Now the thunder has a good deal of bass, but it also has a "bottoming out" sound to it. In that the sub sounds like it bottoming out, and on my earlier systems it sounded just like that. But the better my system has gotten, the better it has been able to reproduce that bottoming out sound. It doesn't sound distorted, it actually sounds like thunder, that powerfull bass with a delicate background sound.


I think thunder just has a natural ability to test a woofer, because its so dynamic. The Cures "Disintegration" album also has track 9 "The same deep waters as you" which has thunder and sounds good.



BTW I highly recommend anyone who is interested to check out Vangelis. Oceanic, Themes, Antarctica, and Reprise are very good albums that really bring some of the best sound engineering. Oceanic has one the best atmospheres I have ever heard, my Magnepans just disapear when I play that album.
 

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Quote:
Originally posted by lwang
So you are saying a sub with the most bloated bass, whose woofer is so uncontrollable that it rings long after the signal has stopped could achieve tight bass just by equalizing the response until it is flat?
Yes. The reason the bass sounds bloated is because the severe resonance you describe is causing a hump in the response. That's what we hear.
 

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Quote:
Under-damped and damped are terms that are widely used, and abused, to explain a portion of why this "boomy" distortion exists. In this case it sounds like the term is used to describe the rapidity in which the cone or "driver" stops moving. Often when a cone is said to be under-damped it will move a lot and continue to move after the desired tone has passed. This causes the sound to be "boomy". If it is over-damped the cone won't move enough causing the sub to sound weak or "thin"(not enough bass). In short the longer the cone moves after the desired tone ceases the more boomy (distorted) the sound will be. In the case of extreme low bass you need a lot of speaker movement because this is what creates the sound pressure. The trick is to get it to stop when the tone does.
It's important to understand that you have a relatively light structure (cone and voice coil) whose position at any given instant is determined by the forces applied by a very strong electromagnetic motor system. In other words, it doesn't work like a drum, where you thwack a diaphragm that then vibrates freely until its motion eventually dies down as a result of mechanical damping. The location of a woofer diaphragm is forced by the interaction between the magnetic field from the driver's fixed magnet and the magnetic field generated around the voice coil by the passage through it of current from the amplifier. So even if the signal to the woofer is abruptly cut off (which pretty much never happens while music is actually being played), it stops moving very quickly. When we talk about woofer damping, what we primarily are talking about is control of the primary resonance. As you approach a driver's primary resonance, it takes less and less force to move it. This is why speakers have a big impedance peak at their bass resonance frequency--the rising impedance reduces the power reaching the driver at the frequency where it is most sensitive. An underdamped woofer system will have a frequency response that bumps up at resonance, whereas an overdamped one will start rolling off early. This is what is critical to the sound we hear; the business about the starting and stopping is greatly oversold!
 

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MDRiggs,


"This is what is critical to the sound we hear; the business about the starting and stopping is greatly oversold!"



I may have missed the mark here but GregLee seems to be new to the fine art of speaker construction and why they do the things they do. So, in an attempt to explain some of the distortion to him I hit a "nerve" with you. This is unfortunate because It was never my intention or "business" to oversell anything. With the exception of the above quote I agree with all of your statements and I personally prefer your explaination of "Tight Bass". I wonder, would it have answered Greg's question? It seemed to me that he was asking about the "typical" definition of the term "Tight Bass". A term that I think we would all be better off without btw.


Conclusion: I may have oversold my point but I was right and I was understood.
 

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Quote:
Originally posted by Dan 41
MDRiggs,


"This is what is critical to the sound we hear; the business about the starting and stopping is greatly oversold!"



I may have missed the mark here but GregLee seems to be new to the fine art of speaker construction and why they do the things they do. So, in an attempt to explain some of the distortion to him I hit a "nerve" with you. This is unfortunate because It was never my intention or "business" to oversell anything. With the exception of the above quote I agree with all of your statements and I personally prefer your explaination of "Tight Bass". I wonder, would it have answered Greg's question? It seemed to me that he was asking about the "typical" definition of the term "Tight Bass". A term that I think we would all be better off without btw.


Conclusion: I may have oversold my point but I was right and I was understood.
Okay. Apologies if I went overboard. No harm intended.
 

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MDRiggs,


I just re-read my last post and it seems a bit harsh. I accept your apology and hope you will accept mine.


I avoided resonance in my explanation because I thought it would only confuse and divert the issue.


Greg,

If you are interested in learning more about resonance, what it is, what causes it and how to control it, there are volumes of information and there are several experts on the subject here in the forum. A couple of them have posted in this thread because the answer to your question, as MDRiggs pointed out and for lack of a better term, is controlling peaks in resonance.
 

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Quote:
Originally posted by Dan 41
MDRiggs,


I just re-read my last post and it seems a bit harsh. I accept your apology and hope you will accept mine.


I avoided resonance in my explanation because I thought it would only confuse and divert the issue.


Greg,

If you are interested in learning more about resonance, what it is, what causes it and how to control it, there are volumes of information and there are several experts on the subject here in the forum. A couple of them have posted in this thread because the answer to your question, as MDRiggs pointed out and for lack of a better term, is controlling peaks in resonance.
No prob. :) Online communication can be a tricking thing with respect to getting tone across. One of the nicest things about AVS Forum is how civilized it is.
 
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