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post #1351 of 2469 Old 12-21-2013, 12:40 PM - Thread Starter
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Quote:
Originally Posted by jbrown15 View Post


That sounds like a great idea, I call dibs on the FTW-21's!...lol

LOL. Let's not get crazy now...FTWs are staying for sure.

 

FV's may be leaving though if I determine in my room that sealed can shake as much ported nearfield...

 

Like I said, I've done tests in my room before, but I didn't use sine waves for testing (used move clips) and as a result, weren't conclusive tests that anyone should or could extrapolate to their rooms.

 

Hopefully, through this exercise, we'll get to the bottom of this.



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post #1352 of 2469 Old 12-21-2013, 01:04 PM - Thread Starter
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Quote:
Originally Posted by bossobass View Post

I was suggesting (among other things):

1) Run a 100dB minimum sine sweep, with the mic wherever it was placed for your test, of just the 21s and then just the FVs, matching level at 15 Hz, and post the graph with the 2 traces.

We'' take it from there...

Both FTW and FV15HP

 

FV15HP Only, 104.1db at 15hz

 

 

FTW21 Only, 105.7 at 15hz.



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post #1353 of 2469 Old 12-21-2013, 01:31 PM
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Interesting stuff guys. Guess I should post my nearfield experience.

I wound up placing a Cap S2 a few inches behind my couch which is close to the center of the room. I also have 3 ported subs along room boundaries. The S2 literally fills the whole couch with bass energy, both ULF and mid bass punch. But it only adds a little to the overall SPL of the room. And by itself it does not shake my wood floor much at all. So the ported subs are critical to provide most of the SPL and "heard" frequencies as well as the floor shake. All of which are required to make the couch shake from the S2 feel natural and integrated and avoid localization issues. Most of the time it is seamless and very effective.

So my impression is that a nearfield sub on concrete would likely shake the seating just as much as on a wood floor. But without the floor shake to go with it, there would likely be localization issues, especially at the higher frequencies.
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post #1354 of 2469 Old 12-21-2013, 05:18 PM
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Thanks for all the new measurements Dominguez. I admit I am truly puzzled now. So at about the same SPL, but this time with the couch much closes to the FTW21's than the FV15HP's, there's more vibration with the FV15's. Sure the Rhytmik's are vented but they're outputing the same wavefront with the same peak pressure difference, so I don't see how it should affect absorption into the couch.

For now I don't have much to add but I'm really looking forward to the resolution of this puzzle.

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post #1355 of 2469 Old 12-21-2013, 05:48 PM - Thread Starter
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Neutro, is it possible that there is an energy that is not detected by an spl measurement device that is causing the shaking?


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post #1356 of 2469 Old 12-21-2013, 06:30 PM
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Yes, if it's transmitted by something else than air for example, but I think you ruled that out already. There could be room effects (modes) at play, since you don't measure SPL inside the couch but a bit above it. For example the Rhytmiks might be well positioned for coupling with a room mode that also couples well with the couch. But two problems with that are 1) 15 Hz is typically much to low for a room mode and 2) the fact that you obtain similar results in another position would be an amazing coincidence.

Would be interesting to repeat the experience at another frequency (not necessarily ULF) to see if the situation is the same.

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post #1357 of 2469 Old 12-21-2013, 07:26 PM
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Quote:
Originally Posted by dominguez1 View Post

More food for thought...



I moved the center section of the couch right in front of the screen so that is essentially nearfield to the FTW21s. This is as close as I will go to swapping positions with the FV and the FTW21s as Archaea and Cowboy asked. Too much of a PIA to go the other route. smile.gif

The FTWs are now ~3ft away from the main LP, and the FV15HPs are ~10ft away from the main LP.

EDIT: When I measured at the main LP, the FV15HPs had a max SPL at 15hz of 105.8. When I played the tone with the FTW21s, they are 93db Max, so I raised the output to match when testing the FTWs. 



Mean = 1.7, Max = 3.1

EDIT: I tested the FTWs at 105.7 Max (no video), and they achieved:

Mean 1.8, Max 2.8

So even though the FV15HPs are now 10ft away, they approximately equal the shake of the 3ft away FTW21s.

If you look at my posted graph again, maybe now you'll see what I was trying to tell you and what is confirmed by the above test.

When you move the sealed subs near field, the FR changes back to anechoic (or closer to anechoic, with room modes). With room gain diminished, the output will be much higher up top than it is at ULF.

IOW, move the sealed subs near field (with little room gain) and you'll have to EQ out the top end or boost the low end to approximate the far field response (which includes room gain).

.

But, the ported subs in their low tune are far less dependent on room gain because they're engineered to only be down -3dB at the frequency you're using for your test.

The ported subs in near field placement have less-to-no room gain effect at 15 Hz, while the sealed subs in far field placement are measuring mostly room gain at 15 Hz. Why the couch measures higher shake with the ported in near field vs the sealed in far field lies in this difference.

Now, you're using a pure sine wave for your test. In my room, a 15 Hz sine wave offers no shake factor. It's a non-event. The shake in my room comes from ULF transients, or pulses. As I said earlier, the proximity of the source to the measurement device is an unknowable variable, especially when using a single frequency sine wave.

IMO, the test requires using actual program for more relevancy and accurate comparison. Use the scene in Oblivion since you've commented elsewhere that when Cruise and Freeman enter the alien ship you felt the 'wobble'. Something like that which you know has the effect you actually want to measure.

So, put everything back where it was and try the test with a scene that you know has the wobble effect.

Me? I'm gonna crack another brew and picture the hard work that's goin' on in Cincy. biggrin.gif
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post #1358 of 2469 Old 12-21-2013, 07:53 PM
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Bosso has a good point. The FTW's rely on room gain (i.e. reflections on boundaries) a lot to get the same SPL as the Rhytmiks, but those probably produce more acoustic energy directly at this frequency...

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post #1359 of 2469 Old 12-21-2013, 08:04 PM - Thread Starter
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This is where I'm not clear on: the acoustic energy piece. Are you saying that there is more acoustic energy being produced directly from the source as compared to the energy that is produced from room gain? If so, then spl and acoustic energy are not proportional...and if they are not, how can this energy difference be measured if not through an spl meter?


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post #1360 of 2469 Old 12-21-2013, 08:51 PM - Thread Starter
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Quote:
Originally Posted by bossobass View Post


If you look at my posted graph again, maybe now you'll see what I was trying to tell you and what is confirmed by the above test.

When you move the sealed subs near field, the FR changes back to anechoic (or closer to anechoic, with room modes). With room gain diminished, the output will be much higher up top than it is at ULF.

IOW, move the sealed subs near field (with little room gain) and you'll have to EQ out the top end or boost the low end to approximate the far field response (which includes room gain).

.

But, the ported subs in their low tune are far less dependent on room gain because they're engineered to only be down -3dB at the frequency you're using for your test.

The ported subs in near field placement have less-to-no room gain effect at 15 Hz, while the sealed subs in far field placement are measuring mostly room gain at 15 Hz. Why the couch measures higher shake with the ported in near field vs the sealed in far field lies in this difference.

Now, you're using a pure sine wave for your test. In my room, a 15 Hz sine wave offers no shake factor. It's a non-event. The shake in my room comes from ULF transients, or pulses. As I said earlier, the proximity of the source to the measurement device is an unknowable variable, especially when using a single frequency sine wave.

IMO, the test requires using actual program for more relevancy and accurate comparison. Use the scene in Oblivion since you've commented elsewhere that when Cruise and Freeman enter the alien ship you felt the 'wobble'. Something like that which you know has the effect you actually want to measure.

So, put everything back where it was and try the test with a scene that you know has the wobble effect.

Me? I'm gonna crack another brew and picture the hard work that's goin' on in Cincy. biggrin.gif

As neutro said, you bring up great points bosso...and may have the smoking gun. :) Perhaps there is more acoustic energy when it produced directly from the source as opposed to room gain. This would make intuitive sense as you explained: The ported subs are tuned right around 15hz, and will be very strong anechoic compared to sealed, especially nearfield. The sealed, farfield, pick up room gain to get to the same SPL at 15hz, and if room gain contains less acoustic energy, would potentially shake the couch less.

 

The shaking gap closed when the FTWs were nearfield, and the FVs were farfield. The FVs are still tuned at around that frequency and still showed strong shaking even 10ft away...again, perhaps its because it has more acoustic energy at this frequency before room gain. I had to boost the FTWs nearfield to match the SPL output, and in doing so, it more closely matched the shaking (and acoustic energy) of the FVs.

 

So that seems to be the best theory thus far in this mini-series: acoustic energy directly from the source is stronger than acoustic energy derived by room gain AND acoustic energy is causing the couch to shake AND acoustic energy is not completely captured by measuring SPL alone.

 

If this is the case, then we should really look at the long term anechoic response of both subs to determine how to match the acoustic energy. If my FVs are 93db anechoic at 15hz, and my FTWs are 80db anechoic at 15hz (again, natural response not max output), to match the acoustic energy of the FVs, I'd have to boost my FTWs by 13db (regardless what room gain gets me). In-room that may mean I measure 20db hotter on the spl meter than the FVs, but I only raised the level by 13db (again to match the acoustic energy).

 

Also, I'm pretty sure that the resonant frequency of my couch is around 15hz. In the oblivion scene that you mentioned, I believe that is right around that frequency to get me the 'wobble' effect. I'll try and give that a shot tomorrow.

 

Cheers, and enjoy your brew. :cool: I'll have to re-look at what I wrote tomorrow as I may have had one too many brews tonight... :D



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post #1361 of 2469 Old 12-21-2013, 09:23 PM
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This is all interesting stuff. When I had my giant 14 cf ported monsters, they would shake the living crap out of everything where as at the time I had 4 x Paradigm servo 15 v2's stacked in the corner, the servo's had more spl but the ported monster could shake full cups off the table whereas the servo's would barely make it move. Now with my current system, the G-horn is pointed directly at the back of my couch and shakes the living crap out of you. So much that when the lower ocaves are playing and you are talking, it sounds like you are talking into a fan or someone is shaking you while talking lol. I always get a funny look when rocking the subs with a new person thats never heard it before.

Blasting brown notes for 10 years and counting!

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post #1362 of 2469 Old 12-21-2013, 09:25 PM - Thread Starter
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Hmmm...thinking about this more...

If the theory above is true, this could explain why sealed Subs have been subjectively said at times to have more mid bass slam compared to ported. Unlike ulf, mid bass would work in the exact opposite behavior when comparing sealed and ported. sealed would have a higher anechoic mid bass response compared to ported and would thus also have more acoustic energy. More acoustic energy would take shape as stronger kick in the chest compared to ported...


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post #1363 of 2469 Old 12-21-2013, 09:43 PM - Thread Starter
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More...

Carp, this would also likely explain why your mbm slams like it does...very strong anechoic mid bass frequencies resulting in a lot of acoustic energy that translates to the tactile feedback your feeling...


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post #1364 of 2469 Old 12-21-2013, 10:55 PM
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Dominguez1 have you ever thought about putting the FTW-21's in a ported enclosure with a 15hz tune?
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post #1365 of 2469 Old 12-22-2013, 03:20 AM
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not sure if you guys got the near field effect thing sorted out yet, but if not...

...at distances of about less than 1/4 wavelength from the source, air doesn't behave like air. instead it behaves like an "incompressible fluid" with the entire slug of air moving back and forth (not compressing and decompressing as most folks tend to think about wave propagation).

the molecules in this region aren't moving back and forth either, as most would think (myself included). instead the molecules are actually moving every which way as the whole slug of air is being moved back and forth.

we discussed this on the diy board a while back and the conversation got pretty heated, so I'm not looking to stoke up and old coals, just providing an explanation for this "near field" effect.

section 2.2.3 describes what constitutes the acoustic near field. it is also called the hydrodynamic nearfield in the literature for those curious to do more reading.

section 4.1 discusses some of the weird behavior of air molecules in this region.

www.win.tue.nl/~sjoerdr/papers/boek.pdf‎

it is this same weird effect that gives rise to the 12db octave "pressure vessel gain" an ideal sealed room experiences when, again, the wavelength is >> the long dimension of the room. in such case the entire room becomes the hydrodynamic nearfield and the behavior tends toward that of an incompressible fluid--the air not losing any spl per distance, the whole room just modulated equally by the driver.
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post #1366 of 2469 Old 12-22-2013, 03:36 AM
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maybe he describes it better than me :-)

http://www.auditory.org/mhonarc/2012/msg00790.html
Quote:
Hi Kevin-

The nearfield of an acoustic source is more complicated because it
contains a reactive (energy storing) component which does not
propagate. Most people stay away from measurements in the nearfield
because the acoustic pressure is an incomplete description of how the
source is behaving. The electrical analogy is that we all walk around
with voltmeters (pressure microphones) and most everyone likes to
ignore the need to measure current (particle velocity).

We can get away with voltmeters because we're usually in the farfield,
where the acoustic waves look resistive (pressure and particle
velocity are in-phase). When we move to the nearfield, suddenly there
are inductors and capacitors in the circuit and simply measuring the
output voltage no longer describes the output power. We need to use a
voltmeter and a current meter (particle velocity sensor*), to measure
the amount of power transfered from circuit to the output terminals.

The challenge of listening in the nearfield is that the pressure can
change quickly as you move around the studio, resulting in unintended
changes in loudness perception of the program material.

I hope that this is useful.
-Tony
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post #1367 of 2469 Old 12-22-2013, 03:48 AM
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one more bit about the weird behavior in the nearfield from Noise Control: From Concept to Application By Colin Hansen (google books preview)

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post #1368 of 2469 Old 12-22-2013, 03:53 AM
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Just to be pedantic about vocabulary, acoustic energy is not something that you can measure at every point in a room like SPL. Rather it's a quantity being expended, carried out transferred, then absorbed.

Perhaps it would be easier to speak about acoustic power, which is the rate of production/ transfer / etc. Of acoustic energy. Acoustic power generated by the sub is the electrical power used minus thermal losses. So it's more or less proportional to electrical power. You are better aware of me of how electrical power is related to SPL in-room.

Note that technically you can store acoustic energy in a room mode, but I don't think this is relevant to our discussion.

Now for room gain, as far as I know, it's basically due to multiple reflections reinforcing direct radiation from the sub. It happens too in the case of the FV15's. But since you calibrated at the same SPL, perhaps the proportion of direct and reflected radiation is different, with direct radiation being somehow more potent...

EDIT pretty interesting stuff about the hydrodynamic near field!

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post #1369 of 2469 Old 12-22-2013, 10:41 AM
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I was told to come and ask this question here from a thread I started about which sub to chose between a JTR Captivator 2400 or a S2. I was asking about tactical feeling between the two subs because of the obvious reasons of one being ported and the other being sealed. I like the tactical feeling of horn/ported subs and was wondering if the S2 had the same feeling as the 2400 considering they both have the same output above tuning on the 2400. I have never experience sub sonic levels or have never had sealed subs before, so do not know how the sub 20hz feels either. Thoughts?

here is the thread:
http://www.avsforum.com/t/1507054/need-help-on-jtr-s2-or-captivator-2400/0_100#post_24105960

Thanks!


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post #1370 of 2469 Old 12-22-2013, 12:40 PM
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Quote:
Originally Posted by LTD02 View Post

not sure if you guys got the near field effect thing sorted out yet, but if not...

...at distances of about less than 1/4 wavelength from the source, air doesn't behave like air. instead it behaves like an "incompressible fluid" with the entire slug of air moving back and forth (not compressing and decompressing as most folks tend to think about wave propagation).

the molecules in this region aren't moving back and forth either, as most would think (myself included). instead the molecules are actually moving every which way as the whole slug of air is being moved back and forth.

we discussed this on the diy board a while back and the conversation got pretty heated, so I'm not looking to stoke up and old coals, just providing an explanation for this "near field" effect.

section 2.2.3 describes what constitutes the acoustic near field. it is also called the hydrodynamic nearfield in the literature for those curious to do more reading.

section 4.1 discusses some of the weird behavior of air molecules in this region.

www.win.tue.nl/~sjoerdr/papers/boek.pdf‎

it is this same weird effect that gives rise to the 12db octave "pressure vessel gain" an ideal sealed room experiences when, again, the wavelength is >> the long dimension of the room. in such case the entire room becomes the hydrodynamic nearfield and the behavior tends toward that of an incompressible fluid--the air not losing any spl per distance, the whole room just modulated equally by the driver.

Quote:
Originally Posted by LTD02 View Post

maybe he describes it better than me :-)

http://www.auditory.org/mhonarc/2012/msg00790.html

Quote:
Originally Posted by LTD02 View Post

one more bit about the weird behavior in the nearfield from Noise Control: From Concept to Application By Colin Hansen (google books preview)


So-called PVG is supposed to begin at the frequency whose length = 2X the longest room dimension. Alas, room gain begins much earlier than that in every room ever measured, bar none.

The articles you refer to do not explain Dom's results because, technically, both the sealed subs and the ported subs are considered to be in near field placements @ 15 Hz, a quarter wavelength of which is 19 feet.
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post #1371 of 2469 Old 12-22-2013, 02:56 PM - Thread Starter
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Quote:
Originally Posted by N8DOGG View Post

This is all interesting stuff. When I had my giant 14 cf ported monsters, they would shake the living crap out of everything where as at the time I had 4 x Paradigm servo 15 v2's stacked in the corner, the servo's had more spl but the ported monster could shake full cups off the table whereas the servo's would barely make it move. Now with my current system, the G-horn is pointed directly at the back of my couch and shakes the living crap out of you. So much that when the lower ocaves are playing and you are talking, it sounds like you are talking into a fan or someone is shaking you while talking lol. I always get a funny look when rocking the subs with a new person thats never heard it before.
Very interesting. I'd be interested to hear from others who have also experienced differences in the shaking effect between ported and sealed...


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post #1372 of 2469 Old 12-22-2013, 02:59 PM - Thread Starter
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Quote:
Originally Posted by jbrown15 View Post

Dominguez1 have you ever thought about putting the FTW-21's in a ported enclosure with a 15hz tune?
I haven't...mainly because I got zero DIY skills and tools. I also lack the time... frown.gif

I had the cabs built at eD, and had the driver shipped there for them to install. They shipped it all back to me as a completed sub package.


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post #1373 of 2469 Old 12-22-2013, 03:02 PM - Thread Starter
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Interesting stuff LTD. I remember reading that thread and the heated debate. LTD, et al, thanks in advance for keeping it cool. smile.gif


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post #1374 of 2469 Old 12-22-2013, 03:36 PM - Thread Starter
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The ported/sealed test is going to have to wait until tomorrow unfortunately...lots of family stuff going on.

Thinking about what was discussed yesterday (in re-reading, I may have had too many brews...) let me clarify and also bring up some more questions...

The theory is that when subs are placed nearfield, they benefit less from room gain and fall back closer to their anechoic response. As a result, they likely need to be calibrated hotter compared to farfield placement. Assuming that acoustic energy is stronger directly from the source (as opposed to acoustic energy generated by room gain), this mean more tactile feedback and energy transfered to the couch. Farfield placement benefits more from room gain, therefore has less acoustic energy, and less transfered to the couch.

The question is, if both subs are compared farfield or both compared nearfield, and both calibrated to the same SPL, they should essentially have the same acoustic energy? IOW, if your gain at 15hz is 6db, regardless of ported or sealed, it will still be 6db. The ported sub may take less EQing than the sealed at this frequency because of it's tuning point, but at the end of the day the mix of direct SPL from the source and room gain will be the same between both designs.

So, if the SPL meter measures 110db at 15hz, the sealed may need 10db of EQing to get to 104db. Add the 6db of room gain, and you're at 110. The ported may only need 2db of EQing to get to the 104db. Add 6db gain, and you're at 110.

In both situations, the sub is outputting 104db directly from the source, and benefitting from 6db of room gain. The ported required less EQ to get to the 104db, but at the end of the day, that acoustic energy for both the ported and sealed is the same.

I would think nearfield placement of both designs should react the same as well. That being the case, there shouldn't be any difference in shaking when I perform the test. We will see...


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post #1375 of 2469 Old 12-22-2013, 04:20 PM - Thread Starter
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Quote:
Originally Posted by Pain Infliction View Post

I was told to come and ask this question here from a thread I started about which sub to chose between a JTR Captivator 2400 or a S2. I was asking about tactical feeling between the two subs because of the obvious reasons of one being ported and the other being sealed. I like the tactical feeling of horn/ported subs and was wondering if the S2 had the same feeling as the 2400 considering they both have the same output above tuning on the 2400. I have never experience sub sonic levels or have never had sealed subs before, so do not know how the sub 20hz feels either. Thoughts?

here is the thread:
http://www.avsforum.com/t/1507054/need-help-on-jtr-s2-or-captivator-2400/0_100#post_24105960

Thanks!

I am performing a test tomorrow to collect more data points around this topic.

 

Between the two, I'd go with the S2 personally. You'll get 1 or 2 octaves more extension with your room size, which means more chance for tactile feedback...

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post #1376 of 2469 Old 12-22-2013, 04:25 PM
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Quote:
Originally Posted by dominguez1 View Post

I am performing a test tomorrow to collect more data points around this topic.

Between the two, I'd go with the S2 personally. You'll get 1 or 2 octaves more extension with your room size, which means more chance for tactile feedback...

Yea, I am pretty convinced that I am going to purchase the S2. I am going to see if I can get in touch with Jeff tomorrow. I am looking forward to your conclusion of your test.


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post #1377 of 2469 Old 12-22-2013, 05:36 PM
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Quote:
Originally Posted by Pain Infliction View Post

I was told to come and ask this question here from a thread I started about which sub to chose between a JTR Captivator 2400 or a S2. I was asking about tactical feeling between the two subs because of the obvious reasons of one being ported and the other being sealed. I like the tactical feeling of horn/ported subs and was wondering if the S2 had the same feeling as the 2400 considering they both have the same output above tuning on the 2400. I have never experience sub sonic levels or have never had sealed subs before, so do not know how the sub 20hz feels either. Thoughts?

here is the thread:
http://www.avsforum.com/t/1507054/need-help-on-jtr-s2-or-captivator-2400/0_100#post_24105960

Thanks!

Quote:
Originally Posted by Pain Infliction View Post

Yea, I am pretty convinced that I am going to purchase the S2. I am going to see if I can get in touch with Jeff tomorrow. I am looking forward to your conclusion of your test.


I'll bite...................

I have a suspended floor, dampen, soundproofed room which is isolated from rest of home ie. has own separate foundation sitting on TJI 16" OC floor joist with stem walls every 12' ................

One S2 in arsenal and 4-UM-18's coming in February........................for now, one S2 in a 25.5 X 17 X 10 ft room creates a trampoline effect.................ie. rocks the whole room. Was thinking another S2 but want to start building subs as I've got the itch. biggrin.gif

To answer your question..............................get the S2, you wont regret it. wink.gif

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post #1378 of 2469 Old 12-22-2013, 06:36 PM
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Dom,

Nice recap. smile.gif

A clarification: the closer you get to a sub the more it reverts to its anechoic response. That's not a theory, it's reality. That's why we ask for a close-mic response when wanting to know what the anechoic response of the sub is. A close-mic shows the subs anechoic response regardless of the room it's in.

Also, in my room the "wobble" effect is most pronounced:

1) When frequencies between 5-10 Hz are included in the effect, and they don't have to be hot in relation to the rest of the frequencies in the effect.

2) When the effect is transient. For example, the lowest fundamental in the F'in Irene scene is right in my rooms sweep spot, 6.2 Hz. But, since it's a constant from beginning to end, it is an unremarkable effect for me. I've only used it to compare the subs mic'd response through SpecLab vs the digital version of same. That comparo shows even order harmonic distortion and intermodulation distortion like no other demo I know of and you can actually calculate the even order harmonic distortion as a % from the SpecLab fairly accurately, which proofed my theory that room gain reduces THD.

Otherwise, the best shake effect scenes contain pulses and/or transients with content 5-10 Hz.

Of course, this eliminates ported subs (or any other resonant system) as candidates for the test in my room.

3. This is not, of course, to be confused with >30 Hz effects that you can feel in your torso/seat. The higher frequency stuff is readily noticeable as being higher in frequency and not relevant to the discussion.

A member here once posted that if you start a slow sine sweep at 5 Hz and watch the driver excursion, you can see the excursion rate increase as frequency increases, but not hear the sound. He said that as soon as your eye can no longer follow the excursion rate because it's getting too rapid, your hearing takes over from your sense of sight. He said he tried the experiment and sure enough, he began to hear just as he could no longer see the rate of excursion increase and that the frequency at which that occurred was... right around 20 Hz.

Try it some time when you have nothing better to do, and... BEFORE the 12th brew. biggrin.gif
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post #1379 of 2469 Old 12-22-2013, 07:00 PM
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Quote:
Originally Posted by bossobass View Post

Dom,

Nice recap. smile.gif


A member here once posted that if you start a slow sine sweep at 5 Hz and watch the driver excursion, you can see the excursion rate increase as frequency increases, but not hear the sound. He said that as soon as your eye can no longer follow the excursion rate because it's getting too rapid, your hearing takes over from your sense of sight. He said he tried the experiment and sure enough, he began to hear just as he could no longer see the rate of excursion increase and that the frequency at which that occurred was... right around 20 Hz.

Try it some time when you have nothing better to do, and... BEFORE the 12th brew. biggrin.gif

I remember this. Seem to hold some water. I find good 20hz content can be ...."heard"? There sure is palpable tactile sensations but it's also audible.

Now that I am 'tune-free' I can certainly echo sentiments of <20hz. I have been wow, wow, wowing all weekend. eek.gif


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post #1380 of 2469 Old 12-22-2013, 07:11 PM
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I have seen this 20hz thing all over the place for years, but I have always had no problem hearing 20hz at all. I’m not saying everyone can but 20hz is easy peasy in my case.

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