What measurement is used for Subwoofer "SPEED"? - AVS Forum
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post #1 of 76 Old 05-03-2013, 05:46 AM - Thread Starter
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I just visited a dealer that carries both JL and SVS today.
Although I did a little homework on the audioholic abut THD, sub's compression and output. Audioholic has CEA sub data sheet
Actual listening today on both JL113 and SVS PB-13 turned me upside down. I was so confused.
People said SVS and JL are comparable, although the former is internet direct, while the latter is brick and mortar and full of reviews.

To be honest, I visited a dealer today with full intention to buy SVS PB-13. ultra
During a visit, We watched some clips on DVD-test ; Iron man, Hulk, Startrek, and The book of Eli.
The dealer simply swap JL and SVS one after another. the same clips were used. I knew afterward that the dealer demo's system; Rotel Processor had been Audyssey-calibrated to Canton sub. During demo, we swift one sub after another without calibration, (I don't know if the gain control for JL and SVS were properly at 75dB or not)

Jl113 --> is very very quick.. it has "speed"
SVS-PB13 --> SVS is lacking speed, but it seems to go low.

I know that comparison between two subs (improperly calibrated) is useless.
what's wrong with me.

If we are to scientifically measure subwoofer speed. what is the measurement to be used? Does REW have that feature?
I hope that maybe gain control on SVS was too low. and that made SVS less impactful than it is supposed to.
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post #2 of 76 Old 05-03-2013, 05:55 AM
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Originally Posted by narutium View Post

If we are to scientifically measure subwoofer speed. what is the measurement to be used? Does REW have that feature?
There is no way of measuring subwoofer 'speed', because there's no such thing. The depth of technical expertise possessed by the dealer you went to is limited to what he's read in sales brochures. A knowledgeable dealer wouldn't even play a sub in the same room with other subs, as the unused subs act as Helmholtz resonators, literally sucking away the output of the sub being tested.
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I know that comparison between two subs (improperly calibrated) is useless.
+1.

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post #3 of 76 Old 05-03-2013, 06:29 AM
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You can measure subwoofer 'speed', its called attack time, the tests are ran with amps and speakers in better audio testing / rating labs. They use terms like ringing and overshoot. I'm not a pro, so don't ask to much of me.
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post #4 of 76 Old 05-03-2013, 07:21 AM
 
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Quote:
Originally Posted by narutium View Post

Jl113 --> is very very quick.. it has "speed"
SVS-PB13 --> SVS is lacking speed, but it seems to go low.

I know that comparison between two subs (improperly calibrated) is useless.
what's wrong with me.

If we are to scientifically measure subwoofer speed. what is the measurement to be used? Does REW have that feature?
I hope that maybe gain control on SVS was too low. and that made SVS less impactful than it is supposed to.

I think what you're asking about is a waterfall chart that shows how responsive a subwoofer's reproduced sound, interacts with a room's acoustics; decay and echo. Anybody is welcome to correct my above comment as they find necessary. Below is an open plane waterfall graph for a PB13-Ultra.



The above does not take into consideration the room acoustics of a listener's Home Theater venue.

The thing that I think is missing when one asks, "what's wrong...", the two subs are totally different subs regarding performance and output.

How much is the JL113 vs the PB13-Ultra? From what I see online, the JL113 has 2,500w RMS vs 1,000w RMS for the PB13-Ultra.

I'm seeing $4,000.00 CDN for the JL113.

Reading further, I see that the JL113, refers to the amplifier output at "short term" which in my opinion is code for peak output. The point, when one uses semantics to jack up their numbers, that's what they're doing, inflating their numbers to make themselves look good.

Think of it like a long distance runner. Cross country runners like to say, our warm-up is a football player's punishment where the heart rate doesn't start to level off until after the first mile and a half and ones doesn't lace up unless going out for three to six miles.

Personally, due to a desire to smooth room response, I'd buy three PC-12 NSD's before buying a single, uber powerful subwoofer.

Personally, if paying with Canadian dollars, I'd buy Funk Audio.

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post #5 of 76 Old 05-03-2013, 07:46 AM
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Originally Posted by joehonest View Post

You can measure subwoofer 'speed', its called attack time.
Logically one might assume that different drivers react to a signal slower or faster based on the driver moving mass, but it's not so. This explains:
http://web.archive.org/web/20030208002619/http://www.adireaudio.com/tech_papers/woofer_speed.htm

Mms doesn't determine transient response, it's mainly an inductance (Le) issue. Where subs are concerned Le sufficiently high to affect transient response within the subwoofer pass band is exceedingly rare.

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post #6 of 76 Old 05-03-2013, 08:26 AM
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Sometimes true deep frequency response can sound like bloat since its more humanly difficult to discern sounds down there. So a sub with deeper extension could possibly sound 'slower'. Higher frequency bass is easier to perceive. This may be why subs with smaller woofers have that bogus audiophile reputation of being 'faster'. What this could also mean is a sub with more harmonic distortion could sound 'quicker', since more upper bass is being played back and the overall sound is easier to track and follow. I don't know if this is the case for the SVS and JL Audio comparison though. The SVS will probably have more group delay around its tuning point thanks to the ports, so a fairer comparison would be between a SB13 and a F113. By the way, what dealer sells SVS subs? Was it a used one?
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post #7 of 76 Old 05-03-2013, 09:55 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

Logically one might assume that different drivers react to a signal slower or faster based on the driver moving mass, but it's not so. This explains:
http://web.archive.org/web/20030208002619/http://www.adireaudio.com/tech_papers/woofer_speed.htm

Mms doesn't determine transient response, it's mainly an inductance (Le) issue. Where subs are concerned Le sufficiently high to affect transient response within the subwoofer pass band is exceedingly rare.

Joe didn't say what "attack time" was based on though, only that it exists.

At what frequency does inductance start to become a factor?

Is mms completely irrelevant, or do many things contribute to a woofer's speed capability?

If 2 woofers had the same inductance for example but cone A weighed twice as much as cone B would there be a measurable and audible difference to the frequency response?
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post #8 of 76 Old 05-03-2013, 10:02 AM
 
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Of course, depending on the size of the magnet?
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post #9 of 76 Old 05-03-2013, 10:33 AM
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Originally Posted by BeeMan458 View Post

Of course, depending on the size of the magnet?

This may surprise you, but magnet size all by itself, is not all that important.

To me, loudspeaker speed relates to high frequency extension. The fastest woofer would also be a good tweeter (and midrange).

Since the convention in modern home audio systems is that LFE channels does not contain high frequency content, it would seem that beyond a certain fairly low frequency, subwoofer speed is irrelevant.

Beyond that, when music contains complex sounds that all by themselves cover a wide range, the way that crossovers work is that the entire system can have wonderful overall performance, even though the subwoofers aren't very good tweeters.

To me, someone who talks about fast woofers doesn't get it.

I hang out with people who are very sophisticated about speakers, people like David Clark (AES fellow, author, lecturer) and Earl Geddes (AES fellow, author, lecturer) . One of our inside jokes is that a fast woofer is a midrange speaker, IOW defective as a woofer.
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post #10 of 76 Old 05-03-2013, 10:37 AM
 
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Originally Posted by arnyk View Post

This may surprise you, but magnet size all by itself, is not all that important.

Didn't say it was. Magnets control what's happening and if they're not all that important, then I'll save a bundle, get little-itty-bitty ones and be happy.
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post #11 of 76 Old 05-03-2013, 11:38 AM
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Originally Posted by BeeMan458 View Post

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Originally Posted by arnyk View Post

This may surprise you, but magnet size all by itself, is not all that important.

Didn't say it was. Magnets control what's happening and if they're not all that important, then I'll save a bundle, get little-itty-bitty ones and be happy.

Magnet don't control what is happening all by themselves. The three most important elements relating to control are the field strength of the magnet (not its size or weight), the construction of the voice coil (mostly number of turns and area in the magnetic field), and the mass of the diaphragm.

It is possible to add a lot of magnetic material to a loudspeaker for the sake of looks only and this has been done, particularly in speakers for car audio that are sold as bare parts.
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Originally Posted by arnyk View Post

Magnet don't control what is happening all by themselves.

Never said they did.

Not sure where you're trying to go with this but I'm stepping out as it reads as if you're looking for an argument when there isn't any as it seems now manufactures are just putting bigger magnets (stronger field strength) on the drivers to sell more drivers. I guess there's no hope for the consumer cause no matter the door, there's always someone standing on the other side with a sign which reads: you lose.

I'm sure you guys could have a good time making sport of our Klipsch, Epic, CF-3's. confused.gif

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post #13 of 76 Old 05-03-2013, 12:15 PM
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Originally Posted by Mik James View Post

Joe didn't say what "attack time" was based on though, only that it exists.

At what frequency does inductance start to become a factor?

Is mms completely irrelevant, or do many things contribute to a woofer's speed capability?

If 2 woofers had the same inductance for example but cone A weighed twice as much as cone B would there be a measurable and audible difference to the frequency response?

hopefully Bill will weigh in on your inductance question.

"speed" or "attack" has nothing to do with frequency response, really. Every sub will in fact play the frequencies within its passband. In fact, I'd wager that pretty much every sub driver will have significant output well above 1000 Hz. Certainly bass guitar speakers roll off about like guitar speakers - - around 3 or 4 thousand Hz. The rolloff is not caused by the size or weight of the cone. It is caused by the fact that the voice coil is a coil so it acts just like the low pass coils in speaker crossovers, rolling off highs above some frequency. If the thing will output 1000 Hz, it has to be "fast enough" to output 40 or 80 or 100 Hz, right? (It'll likely be peaky in its high frequency response and will beam like mad at high frequencies but they're really there . . .) just by way of example, purely random, here's the eminence Kilomax Pro 15. It's rated frequency response is up to 800 Hz, but its output plot shows rolloff starting at just under 2000 Hz.
http://www.eminence.com/speakers/speaker-detail/?model=Kilomax_Pro_15A

So the speed question is whether the sub starts playing its "notes" later than the other speakers start playing. At least that's the way I see the slow sub idea. It is NOT that the sub will output 50 Hz when you feed it an 80 Hz tone beause it can't move fast enough. It will play the frequencies presented. Whether the frequencies output are at the same relative levels as the input is "frequency response" and depends on a host of factors.

Two otherwise identical speaker drivers that differ only in their cones and are tested raw or used in identical boxes without EQ will likely have different frequency responses simply because they're different speakers. They'll also have different distortion characteristics. Lots of details about the cone affect frequency response. You can change the high end wiht different dust caps, even.
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post #14 of 76 Old 05-03-2013, 12:20 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

Logically one might assume that different drivers react to a signal slower or faster based on the driver moving mass, but it's not so. This explains:
http://web.archive.org/web/20030208002619/http://www.adireaudio.com/tech_papers/woofer_speed.htm

Mms doesn't determine transient response, it's mainly an inductance (Le) issue. Where subs are concerned Le sufficiently high to affect transient response within the subwoofer pass band is exceedingly rare.

I am sure that the writer of this article is much smarter than myself by far. However there is a lot wrong about this article. There is also a lot balanced towards the speaker manufacturer in charge of it. More tech jargon biased to skew the specs or info towards the sellers product. Don't get me wrong most of what ist says is absolutely correct. Some, however is not and what it doesn't say leaves a lot of the info balanced in their own favor. Inductance is extremely important to driver acceleration from a dead stop as the article is describing. however, how often is your driver starting from a dead stop? Again though this same aspect also works to change direction of the driver. Notice he didn't get into that other formula he mentioned about inertia; that is where Mms comes into play. remember that a body in motion tends to stay in motion; this means that a heavier Mms is slower to start moving and or slower to change direction (all other factors remaining equal). The equation he uses where i::a, by using the same logic, Bl would be proportional to Mms and we all know that this is not really so.

There are many things that effect the speed of a driver. Some due to the drivers design and others not. Such as system design of the sub driver and cabinet, amplifier damping factor, cables (due to much of the same reasoning he describes in the article). Addressing the OP's original thoughts are most likely design differences in the driver as well as the sub system itself, such as the cabinet and amp.

I forgot to get into compliance of the suspension/ system but will leave that as simply stating that it also has some effect on the situation as well.

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Originally Posted by arnyk View Post



To me, loudspeaker speed relates to high frequency extension. The fastest woofer would also be a good tweeter (and midrange).

.

It looks to me that you may be playing a semantics card. In the world of physics this is absolutely true when you compare speed of differing frequencies. However that is not what is being done here. Let's use a little common sense shall we. We are not comparing the speed of a tweeter to that of a woofer so that frequency range is irrelevant here. we are comparing different woofers utilizing the same frequency range input as the others it is compared to. One woofer may absolutely react "faster" to a change of direction than a different woofer. That is what is being discussed. Please read your wording again as I have highlighted. The speed of loudspeakers in general is not being discussed. Only that of low frequency drivers (woofers).

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post #16 of 76 Old 05-03-2013, 02:49 PM
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A slow sub, some would say sounds muddy, where as a fast sub will sound punchy. Subs with 8s or 10s are more likily to have a punchy sound were as subs with 12s and 15s could be muddy. Punchy sub may be best used for music, muddy is just muddy, but will work for home theater, just need to rattal the walls. Any size sub can sound great if well made.
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post #17 of 76 Old 05-03-2013, 03:26 PM
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Quote:
Originally Posted by Mik James View Post

Joe didn't say what "attack time" was based on though, only that it exists.
The attack time is determined by the ability of the driver motor to overcome the inertia of the moving mass. There are no audible differences in the attack times of drivers, as the electro-magnetic forces operate in the realm of the speed of light, not the speed of sound.
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At what frequency does inductance start to become a factor?
Perhaps 200Hz, worst case, with a very high Le driver, like a 21 with a six inch coil.
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Is mms completely irrelevant, or do many things contribute to a woofer's speed capability?
Irrelevant. All woofer cones move at the same speed.
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If 2 woofers had the same inductance for example but cone A weighed twice as much as cone B would there be a measurable and audible difference to the frequency response?
Not within the subwoofer pass band.
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One woofer may absolutely react "faster" to a change of direction than a different woofer.
The electromagnetic force of the driver motor is so strong compared to the inertia of the moving mass that it isn't affected by changes in that mass. One might be inclined to think so in looking at a waterfall plot, but that's not what a waterfall plot shows. A waterfall plot shows what happens when the signal ceases and how the inertia of the moving mass then causes the driver to 'ring on'. In short, a high moving mass has no significant effect on how the driver reacts to an applied signal, but it does have an effect on how the driver reacts once the signal stops. In the midbass and higher frequencies you can hear that effect as transient response. In the bass frequencies you cannot, for the same reason why you can't directionally locate low frequencies: your ear/brain isn't wired to do so.

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post #18 of 76 Old 05-03-2013, 03:29 PM
 
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Quote:
Originally Posted by joehonest View Post

A slow sub, some would say sounds muddy, where as a fast sub will sound punchy. Subs with 8s or 10s are more likily to have a punchy sound were as subs with 12s and 15s could be muddy. Punchy sub may be best used for music, muddy is just muddy, but will work for home theater, just need to rattal the walls. Any size sub can sound great if well made.

Reads like some are having trouble with subwoofer integration as what you describe is what it sounds like when low frequency waves argue with each other. Things didn't improve in our room until we got room measuring capability and started taming all those wild subwoofer produced sound waves. Humps and nulls create confused sound which one can easily characterize as muddy due to all the humps and suck-outs or nulls; room modes.

We still have a big -6dB suck-out that we're working on. If one looks to their graphs, spectrographs and waterfall plot, they'll have a better idea of what's happening with their room's acoustics as via these graphs, one can easily see why their subwoofer reproduced sound waves, come across as muddy......because they are but it's not the fault of the subwoofer. The waterfall plots below are of the same subwoofers and room. The right graph, a third sub was added and was effort put forth to integrate the three subs into the room's acoustics. One can easily see that although the same subwoofers and the same room's acoustics, the bass is much tighter.

Two subs:................................................................Three subs.

...

And if we wanted the room to be "boomy," one need only to turn up one of the subwoofer's gain a smidge and voila, instant boomy.

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post #19 of 76 Old 05-03-2013, 03:50 PM
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Probably a combination of

1) Spectral decay graphs
2) THD graph
3) Cycle delay
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Moi? confused.gif
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post #21 of 76 Old 05-03-2013, 04:14 PM
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Originally Posted by Mr. Bubbles View Post

One woofer may absolutely react "faster" to a change of direction than a different woofer. That is what is being discussed.
No, that isn't what is being discussed.

The terms "slow" and "fast" as used to describe the characteristic sound of a subwoofer have nothing at all to do with whether a woofer might "react faster to a change in direction". Nor do the terms "tight" and "loose" have anything to do with this. The "speed" of the woofer, itself, is not even really relevant to this discussion.

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post #22 of 76 Old 05-03-2013, 07:34 PM
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Originally Posted by sivadselim View Post

No, that isn't what is being discussed.

The terms "slow" and "fast" as used to describe the characteristic sound of a subwoofer have nothing at all to do with whether a woofer might "react faster to a change in direction". Nor do the terms "tight" and "loose" have anything to do with this. The "speed" of the woofer, itself, is not even really relevant to this discussion.
+1. Whats really being tossed about are subjective terms that don't accurately describe anything by those who don't know how to describe whatever it is that they're trying to describe with objective terms that actually have meaning. And if that seems convoluted, it's no more so than using the terms fast or slow to describe the response of a subwoofer when they mean something different to every user.

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post #23 of 76 Old 05-03-2013, 07:37 PM
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Whats really being tossed about are subjective terms that don't accurately describe anything by those who don't know how to describe whatever it is that they're trying to describe with objective terms that actually have meaning.
Could you please provide the corresponding objective terms that actually have meaning? That would be helpful. Thanks. smile.gif


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post #24 of 76 Old 05-03-2013, 07:46 PM
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Originally Posted by eljaycanuck View Post

Could you please provide the corresponding objective terms that actually have meaning? That would be helpful. Thanks. smile.gif
I can't, because each person's definition of 'fast' bass is different. For instance, my definition of 'fast' bass is when I'm playing 64th notes.

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post #25 of 76 Old 05-03-2013, 08:12 PM
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I am sure others may disagree but what I believe "many" people mean by speed of bass (again many people, not all) has nothing to do with one note bass. This has already been pointed out that all drivers play the same frequencies at the same speed, hence the particular frequency. If the speed of the driver were different it would be playing a different frequency. However when we listen to music, the driver is playing overlapping and even multiple frequencies on top of each other (at least that's the way our ears perceive it). What I believe many people actually are describing with the term speed is the driver/ systems ability to cover this range and all the dynamic changes in the signal in a cleaner, more controlled manner versus a driver/ system with less control over the input signal. This is where distortion is introduced and phase is shifted compared to the original signal input and most of us are after less distortion and a more accurate reproduction of the original input signal. Hence my original description of the drivers/ systems ability to change. not just change direction of the driver at a signal frequency but to control all the minor changes in the music signal as well as the major changes and keep the output as close to the original input signal as possible. There are many factors that effect this, not just one or two. Some of those are being described as irrelevant, and I respectfully disagree. I do agree that opinions do not change physics.

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post #26 of 76 Old 05-03-2013, 09:15 PM
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post #27 of 76 Old 05-04-2013, 11:10 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

I can't, because each person's definition of 'fast' bass is different. For instance, my definition of 'fast' bass is when I'm playing 64th notes.

at 120 bpm, I'm sure! smile.gif
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post #28 of 76 Old 05-04-2013, 11:17 AM
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Originally Posted by Mr. Bubbles View Post

It looks to me that you may be playing a semantics card. In the world of physics this is absolutely true when you compare speed of differing frequencies. However that is not what is being done here. Let's use a little common sense shall we. We are not comparing the speed of a tweeter to that of a woofer so that frequency range is irrelevant here. we are comparing different woofers utilizing the same frequency range input as the others it is compared to. One woofer may absolutely react "faster" to a change of direction than a different woofer. That is what is being discussed. Please read your wording again as I have highlighted. The speed of loudspeakers in general is not being discussed. Only that of low frequency drivers (woofers).

thing is, if they all can, without EQ, actually reproduce a 1000 or 2000 Hz Hz input, it's hard to see how they're too slow to respond to 40 Hz.
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post #29 of 76 Old 05-04-2013, 11:22 AM
 
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But the LFE channel is basically, 0Hz to 80Hz content as anything >80Hz is locatable.

What am I missing as I'm stuck on subwoofers and managed bass with LPF's set to <80Hz and bass content of the LFE channel being reproduced by our subwoofers and to me, it appears that you guys are talking about upper level frequencies being reproduced by the rest of the speaker channels......frequencies our personal subs don't seem to be dealing with.

...confused.gif

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post #30 of 76 Old 05-04-2013, 11:52 AM
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Originally Posted by sivadselim View Post

The terms "slow" and "fast" as used to describe the characteristic sound of a subwoofer have nothing at all to do with whether a woofer might "react faster to a change in direction". Nor do the terms "tight" and "loose" have anything to do with this. The "speed" of the woofer, itself, is not even really relevant to this discussion.
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Originally Posted by Bill Fitzmaurice View Post

+1. Whats really being tossed about are subjective terms that don't accurately describe anything by those who don't know how to describe whatever it is that they're trying to describe with objective terms that actually have meaning. And if that seems convoluted, it's no more so than using the terms fast or slow to describe the response of a subwoofer when they mean something different to every user.
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Originally Posted by eljaycanuck View Post

Could you please provide the corresponding objective terms that actually have meaning?

Well, the terms are not really THAT entirely subjective. I think that, very generally, most people DO know what is meant by "fast", tight", "slow", loose" (etc.) bass. And it probably wouldn't surprise anyone if those characteristics could be correlated to certain measurable parameters of a subwoofer's performance. And they have, btw. (You can do your own research.)


Quote:
Originally Posted by Mr. Bubbles View Post

I am sure others may disagree but what I believe "many" people mean by speed of bass (again many people, not all) has nothing to do with one note bass. This has already been pointed out that all drivers play the same frequencies at the same speed, hence the particular frequency. If the speed of the driver were different it would be playing a different frequency. However when we listen to music, the driver is playing overlapping and even multiple frequencies on top of each other (at least that's the way our ears perceive it). What I believe many people actually are describing with the term speed is the driver/ systems ability to cover this range and all the dynamic changes in the signal in a cleaner, more controlled manner versus a driver/ system with less control over the input signal. This is where distortion is introduced and phase is shifted compared to the original signal input and most of us are after less distortion and a more accurate reproduction of the original input signal. Hence my original description of the drivers/ systems ability to change. not just change direction of the driver at a signal frequency but to control all the minor changes in the music signal as well as the major changes and keep the output as close to the original input signal as possible. There are many factors that effect this, not just one or two. Some of those are being described as irrelevant, and I respectfully disagree. I do agree that opinions do not change physics.

Again, the speed (or even the way) that a subwoofer's driver moves has no real relevance to the characteristics that people often describe as "fast", "slow", "loose", or "tight" bass. The same exact subwoofer could sound "slow" or "loose" to you in one room, yet sound "fast" or "tight" to you in another room. Or in another location in the room. Or with the addition of room treatments. Or by simply moving to another seat to listen to it. So, how does it have anything to do with the way the driver is moving?

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