What measurement is used for Subwoofer "SPEED"? - Page 3 - AVS Forum
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post #61 of 76 Old 05-06-2013, 05:24 AM
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Originally Posted by Bill Fitzmaurice View Post

The problem with your analogy is that it would only be accurate if it was comparing a 2000 pound and a 4000 pound car, both driven by 10,000 HP turbofan jet engines. That would be a fair comparison, as the Mms relative to the force provided by the driver motor is miniscule.

Miniscule in most cases but none the less important in many cases. Hence the reasoning for lighter drivers that still retain rigidity in many of the top speakers in the world. If Mms were unimportant drivers could more easily be made from plywood than many other materials commonly in use today, or always for that matter.

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post #62 of 76 Old 05-06-2013, 10:29 AM
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My take subwoofer speed;

Somewhat like porn, except in this case ... you know it when you hear it. smile.gif


Terms like "speed", "tight", "taught" "quickness", or more maybe appropriately "well defined, well delineated, transparent or high resolution bass".... etc, enthusiasts, savvy or otherwise will continue to use the terms.


The time domain.
It's a function of several elements. But as mentioned, it's the time domain that's key to the subjective appeal of subwoofer speed. It's a well executed and capable sub design that's matched ideally in time/signal alignment with the octaves above. As Bill stated, material like a bass guitar has complex variety of harmonics, ... all of which must be aligned in time for an accurate portrayal of the instrument.

A kick drum, a rock kick drum heavily EQ'd may have a spectrally diverse set of components. Typically boom, smack, click .. is often what engineers may use when discussing it. Anyway, artificial or not, it's ideal if it's all aligned upon the wave-launch into the room. If the time alignment is off, the subjective component lost is speed, definition, spectral delineation.

On the room side, there's a host of acoustic distortions .. that can easily corrupt the signal that was so well aligned aligned a short time ago. SBIR or any destructive acoustic influence can easily null an important spectral component of the kick drum/bass guitar,..so care must be taken. Also, a room's decay characteristics are of paramount importance in subjective appeal for speed, definition and tightness. Unfortunately, decay characteristics for the bottom octaves are contraindicated for the midband and upper freqs (but there's steps that mitigate this issue).

Finally, the system's capability comes into play. Velocity has been mentioned, as has ringing. Maintaining adequate system headroom with multiple drivers, so that each driver moves slower (yes slower smile.gif ) for a given freq/given level .... thus lowering potential non-linearity and the artifacts contained therein.

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post #63 of 76 Old 05-06-2013, 10:42 AM
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There's other factors too, I forgot to mention above. Aside from the hugely dominant subjective components, consider driver type, alignment, voltage/current delivery too.

Examining a driver's actual reactionary response, transient response or impulse response .... although I fully understand the merit behind the theory, I'm not entirely on board with the statement that the driver has nothing to do with it.

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post #64 of 76 Old 05-07-2013, 05:40 AM
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Quote:
Originally Posted by sivadselim View Post

Yes, so. But suit yourself. True, you aren't missing much. Honestly,I do not know how steep the 'LPF of LFE' is on most AVRs. What is your AVR??
The 'LPF of LFE' setting will not affect the dialog at all as there is no dialog supportive material encoded in the LFE channel.
That little bit of LFE info between 80Hz to 120 Hz makes that big a difference, huh? Yeah, sure it does.
Maybe you have some REW measurements you can show us to support these assertions.
Seems to me some folks STILL do not understand the LFE channel or bass management. What the LFE channels is, how the LFE channel is encoded at production, how an AVR decodes it, and how the other speaker channels' bass is bass managed completely independently from it.

I'm not sure, its an onkyo 3007, at most it would only be 24db per octave slope, so at 80hz it would only be down 12db@120hz.. Listening at reference level, and setting the sub +3db hot, I'm sure I'm hearing and feeling everything the director hoped for.. I've tried 90hz,100hz and 120hz, but 80hz is clearly the best choice for my HT setup. The sub, a polk 505, its over 5 years old, and still rock'n..
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post #65 of 76 Old 05-07-2013, 10:11 AM
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Quote:
Originally Posted by joehonest View Post

I'm not sure, its an onkyo 3007, at most it would only be 24db per octave slope,

Why do you think the the 'LPF of LFE' could not be steeper than 24dB/octave?

You realize that the 'LPF of LFE' does not at all affect any of the bass-managed bass from any of your speaker channels, right? It is only applied to the material encoded in the LFE channel. It has absolutely nothing to do with the low-pass filters in the AVR's speaker channel crossovers.

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Originally Posted by joehonest View Post

.............so at 80hz it would only be down 12db@120hz.

FYI, just for clarification. Even though 160Hz is one octave up from 80Hz, because it is a logarithmic scale, 120Hz is NOT a half an octave up from 80Hz.

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Originally Posted by joehonest View Post

I'm sure I'm hearing and feeling everything the director hoped for...........

If the LFE channel can contain info as high as 120Hz, but you are truncating it at 80Hz, how can you possibly be "hearing and feeling everything the director hoped for..........."? You can't. You are NOT reproducing the entire sound track. This is not arguable.

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post #66 of 76 Old 05-08-2013, 03:55 AM
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Quote:
Originally Posted by sivadselim View Post

Why do you think the the 'LPF of LFE' could not be steeper than 24dB/octave?

You realize that the 'LPF of LFE' does not at all affect any of the bass-managed bass from any of your speaker channels, right? It is only applied to the material encoded in the LFE channel. It has absolutely nothing to do with the low-pass filters in the AVR's speaker channel crossovers.
FYI, just for clarification. Even though 160Hz is one octave up from 80Hz, because it is a logarithmic scale, 120Hz is NOT a half an octave up from 80Hz.
If the LFE channel can contain info as high as 120Hz, but you are truncating it at 80Hz, how can you possibly be "hearing and feeling everything the director hoped for..........."? You can't. You are NOT reproducing the entire sound track. This is not arguable.
Don't have time for a thorough response right now, but Roger Dressler recommends and uses an 80 Hz LPF of LFE. His reasoning is sound, and I've been doing the same for quite a while now.

I'll try to find the links and post them later.

Edit: In the Audyssey FAQ, Keith Barnes quotes both Roger Dressler and Mark Seaton on their logic for setting the LPF of LFE to 80 Hz:
http://www.avsforum.com/t/795421/official-audyssey-thread-faq-in-post-1/51750#user_c5

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post #67 of 76 Old 05-08-2013, 06:26 AM
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Thanks for the link. It seem s to go along with Beemans thinking pretty well. My knowledge is more towards 2ch, but am trying to learn more about HT and these discussions help me.

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post #68 of 76 Old 05-08-2013, 06:52 AM
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Quote:
Originally Posted by Mr. Bubbles View Post

Thanks for the link. It seem s to go along with Beemans thinking pretty well. My knowledge is more towards 2ch, but am trying to learn more about HT and these discussions help me.
Let's just say that the BeeMan's thinking is still evolving... wink.gif

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Which is a much easier concept to grasp then to accept subwoofer integration into a Home Theater sound system transcends science and is more art then science.

There is only one constant I've found and that is, one "MUST" have room measuring capability as everything else on the table is to be played with.

A concept worth hanging one's hat on is the scientific principal of repeatability. Lacking this principal, one has a choice of realizing they're not dealing with science but instead they're dealing with the wishful thinking of art as it's mighty hard to make three unaligned points into a straight line but real easy to make into a plane.

When conceptually, one realizes they're dealing in the world of 3-D (art), they'll stop looking to stated linear solutions and when they do that, their efforts will find the solid ground of repeatability; science.

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post #70 of 76 Old 05-08-2013, 10:33 AM
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Quote:
Originally Posted by craig john View Post

Don't have time for a thorough response right now, but Roger Dressler recommends and uses an 80 Hz LPF of LFE. His reasoning is sound, and I've been doing the same for quite a while now.

I'll try to find the links and post them later.

Edit: In the Audyssey FAQ, Keith Barnes quotes both Roger Dressler and Mark Seaton on their logic for setting the LPF of LFE to 80 Hz:
http://www.avsforum.com/t/795421/official-audyssey-thread-faq-in-post-1/51750#user_c5

Craig

Thanks! I missed this "development". If you can find the links to Roger's viewpoint, that'd be great.

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Let's just say that the BeeMan's thinking is still evolving... wink.gif
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Originally Posted by BeeMan458 View Post

Which is a much easier concept to grasp then to accept subwoofer integration into a Home Theater sound system transcends science and is more art then science.

There is only one constant I've found and that is, one "MUST" have room measuring capability as everything else on the table is to be played with.

A concept worth hanging one's hat on is the scientific principal of repeatability. Lacking this principal, one has a choice of realizing they're not dealing with science but instead they're dealing with the wishful thinking of art as it's mighty hard to make three unaligned points into a straight line but real easy to make into a plane.

When conceptually, one realizes they're dealing in the world of 3-D (art), they'll stop looking to stated linear solutions and when they do that, their efforts will find the solid ground of repeatability; science.

He still posts gobbledygook. biggrin.gif

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post #71 of 76 Old 05-08-2013, 11:20 AM
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Quote:
Originally Posted by sivadselim View Post

Thanks! I missed this "development". If you can find the links to Roger's viewpoint, that'd be great.
Roger's quotes are clearly linked to in the thread that Craig John referenced. confused.gif
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post #72 of 76 Old 05-08-2013, 11:24 AM
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Originally Posted by desertdome View Post

Roger's quotes are clearly linked to in the thread that Craig John referenced. confused.gif
Yeah, I posted that prior to reading. Thanks.

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post #73 of 76 Old 05-30-2013, 05:50 AM - Thread Starter
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I learned a bit or two during the last few days. My SVS PB-13 ultra had been plugged. From the originally designed ported subwoofer it turns into sealed subwoofer.
And the result. is the bass is very very punchy. definitely more punchy.

I learned from SVS that seal sub has a high roll off. and it give a feeling of punch and speed.
I don't how to define it in engineering / scientific term. but it's totally a new subwoofer......
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post #74 of 76 Old 05-30-2013, 07:53 AM
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Originally Posted by narutium View Post

I learned a bit or two during the last few days. My SVS PB-13 ultra had been plugged. From the originally designed ported subwoofer it turns into sealed subwoofer.
And the result. is the bass is very very punchy. definitely more punchy.
...
What you're referring to as punch and speed is the result of a loss of low frequency response. If I was to put a name to that it would be 'thin' or 'weak'. This assumes that the sub in the ported mode was properly placed and EQ'd for flat in room response. If you didn't do so the low end might have been excessive, and that could explain why you found sealing it made it better.

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post #75 of 76 Old 05-30-2013, 08:26 AM
 
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Quote:
Originally Posted by Bill Fitzmaurice View Post

What you're referring to as punch and speed is the result of a loss of low frequency response. If I was to put a name to that it would be 'thin' or 'weak'. This assumes that the sub in the ported mode was properly placed and EQ'd for flat in room response. If you didn't do so the low end might have been excessive, and that could explain why you found sealing it made it better.

If running several sealed subs in a room, I'm of the understanding that room gain improves bottom end response on the left side of the graph and of course, makes a similar assumption of properly integrating the sealed sub into a room's acoustics. confused.gif.

Where does "punch and speed", appear after "loss of low frequency response?" What is the the threshold of this phenomenon appearing?
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post #76 of 76 Old 05-30-2013, 09:09 AM
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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).

Objective speed is FR, period. The higher in frequency, the faster.

But there is a subjective sense of "bass speed" too. That too IME has mostly to do with FR. Specifically, integration of the sub with the mains. Said integration tends to be easier when their are multiple subs folded into the mains, the subs all perform well an octave or more above their respective nominal lowpasses, and the mains are closed boxes.
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I hang out with people who are very sophisticated about speakers, people like *** 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.

It's worth noting that the subs Dr. Geddes currently sells - closed boxes with B&C "pro" drivers in them - do not have terribly low F3 points on their own. They do, however, have HF extension well beyond a reasonable low-pass for a sub, relatively high efficiency at the top of their passband (there's a lot more music at 80Hz than 30Hz), and enough stroke and power-handling to play low in-room with appropriate EQ. That strikes me as a good template to follow.
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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.

IME, it's much lower than that. In addition to the HF rolloff, there's also an inductive hump smack in the middle of the passband on a lot of woofers. I remember measuring something like an 8dB hump centered in the 50-60Hz range on a Stryke (now Acoustic Elegance) HE15 from the late 1990s/early 2000s. (I didn't even know what inductance was until I started researching reasons why the HE15 sounded so...sluggish compared to systems based on woofers with much less volume displacement, such as the Peerless XLS12.) The HE15 was a woofer with an extremely long voicecoil (xmax in the 30mm neighborhood) and no shorting rings. For a more current comparison, look at the RE SX18 and the TC Sounds Pro5100.. Yes, I realize the comparison is flawed in a number of ways (price, overhung vs. underhung motor, etc), but it shows the difference in FR well below 200Hz due primarily to inductance. The RE SX18 has a very long overhung coil and no mention of inductance control measures, whereas the Pro5100 has a a shorter coil (underhung, probably near evenhung given TC's general "let it move until it hits metal" design philosophy) moving inside an Aurasound-knockoff motor with shorting rings.

I'd avoid any woofer with a very long voice coil unless it also had very good inductance control OR the woofer was only going to be used very very low (say, as an air pump for below 35-40Hz in a multisub system with smaller subs above it).

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