Nearfield Ported MBM for Increased Mid-Bass Tactile Response - Page 61 - AVS Forum | Home Theater Discussions And Reviews
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post #1801 of 3131 Old 02-02-2017, 06:13 AM
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Have any of you guys tried those slim-profile under-the-couch subs to get more tactile? Like any of the below:
  • Earthquake Sound CP8 Couch Potato
  • Dayton Audio SUB-1000L 10" 100 Watt Low-Profile Powered Subwoofer
  • Yamaha YST-FSW150BL Advanced YST II Down-Firing Active Subwoofer
Theoretically these could fit under a couch or a chair (and thus be less obtrusive).
I see their disadvantage, compared to the Behringer B1200D, is that they could be underpowered and higher THD.

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post #1802 of 3131 Old 02-02-2017, 08:13 AM
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Quote:
Originally Posted by bscool View Post
OK, if you get a chance I would be curious to see what your SPL is at your listening position without the MBM and then what is the SPL with the MBM while the same volume level on your AVR for both. Because if you are at say 102db with the MBM and 112db after while listening to the same track at the same volume level on your AVR then you are not comparing apples to apples in my opinion. Gaining 6-10db @50-100hz would obviously make a big difference ported or sealed.

I did the testing a while back and I don't remember what my numbers were if I remember right I measured SPL to get good tactile feel and it was around 115-120dB peak in REW using a ported Kappa 18 tune to 41hz.

What kinda SPLs do you guys measure at your seating position getting good tactile feel?
Here's what I got after I integrated the 1200D. Not much increase in SPL at all (a max of maybe 3dB at 75hz), but the TR was massively increased! This is with the 1200D directly behind my chair (about 8").

To get massive TR, I have to have the MV up around -10 or more, although even below that you can most certainly tell the MBM is there.
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post #1803 of 3131 Old 02-02-2017, 08:47 AM
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Originally Posted by Alan P View Post
Here's what I got after I integrated the 1200D. Not much increase in SPL at all (a max of maybe 3dB at 75hz), but the TR was massively increased! This is with the 1200D directly behind my chair (about 8").

To get massive TR, I have to have the MV up around -10 or more, although even below that you can most certainly tell the MBM is there.
That's about what I got. A few dB increase across the B1200's bandwidth and it really filled in some dips nicely that I had in the midbass. I haven't rerun REW since adding the second B1200...should probably do that.

Speakers: PSA MTM-210T x2, MTM-210C, MT-110SR x2; Atmos-SVS Satellite x2, DIY Volt-10 x2
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post #1804 of 3131 Old 02-02-2017, 09:24 AM
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The difference is very noticeable with my 1200D pair as I can turn them off instantly from Mlp. More mid bass and TR for SURE.
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post #1805 of 3131 Old 02-02-2017, 10:24 AM
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Quote:
Originally Posted by amnesia0287 View Post
I guess the easiest way to ask is, has anyone figured out WHY a ported sub would have more particle velocity?
Substantially smaller radiating area is the major difference
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post #1806 of 3131 Old 02-02-2017, 11:23 AM
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Quote:
Originally Posted by 3ll3d00d View Post
Quote:
Originally Posted by amnesia0287 View Post
I guess the easiest way to ask is, has anyone figured out WHY a ported sub would have more particle velocity?
Substantially smaller radiating area is the major difference
So ported subs actually have a different radiation pattern?
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post #1807 of 3131 Old 02-02-2017, 11:46 AM
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Quote:
Originally Posted by amnesia0287 View Post
So ported subs actually have a different radiation pattern?
you mean how the soundwave propagates beyond the port? if so, no.
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post #1808 of 3131 Old 02-02-2017, 12:47 PM - Thread Starter
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Originally Posted by bscool View Post
Haha I see as soon as I posted this you basically covered what I was looking for. But has anyone actually took a sealed subwoofer that put out the same spl and the same frequencys as a ported and compared in actual real life? How noticeable is the difference? I see many people on these board say this program showed this or we can measure that but in acutual use a difference cannot be noticed even though it could be measured or shown in a simulation. Not saying you guys are wrong I just need to see actual hard real life test results
Yep...the below 4 examples in Post 1 where it is the same SPL but greater TR response for ported compared to sealed.


Quote:
Originally Posted by dominguez1 View Post
Background

In the ULF thread and @coolrda 's Vibsensor thread, we've been discussing how different sub designs (sealed, ported, horn, etc.) can produce different tactile responses. When placed nearfield, these differences become more pronounced. Our focus has been largely from a ULF tactile response (TR) standpoint.

One of the theories is that ported produces more TR than sealed around the tune. I first demonstrated this in the ULF thread in this post:

Ported vs Sealed in my room

Recently, others have also done similar tests, but used a far more accurate measuring system with VibSensor:

@derrickdj1 example



His martysub is tuned to 20hz, and you can see in the above (scales were adjusted on images so that you can directly compare) that 20hz is much higher compare to his sealed Marty (plugged vents).

@MKtheater example



MK ported his IB setup, putting him at around a 7hz tune. You can see from the above how much the 10hz TR changed, even when he was running his sealed setup much hotter.

Within the spoiler below, I put together a much more detailed analysis of MK's example above:

Spoiler!



Testing Update 6-1-16: FV15HP vs 1200D


Subs:
Rythmik FV15HP - 15in Driver w/12hz tune
Behringer 1200D - 12in Driver, w/65hz tune


Distance:
10.5in behind the Main Listening Position


Content:
47hz Sine Wave


Level:
88db


Measuring tool:
LG G5 running VibSensor 2.0.0


Each sub was placed in the exact same location, and each was calibrated to 88db. I placed the LG G5 at the MLP and ran the tests.

The results are in....






As you can see, the 1200D has almost 2X the PSD and acceleration as the FV15HP at the same frequency and the same SPL.

Additionally, I don't believe this is at the tune of the 1200D. If VS was able to measure around 55hz, I believe the difference would be even larger...
In my setup the difference was a night and day! Not even close... I can best speak of the difference in the ULF range because I lived with Sealed subs nearfield for many months, and then switched to ported nearfield.
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post #1809 of 3131 Old 02-02-2017, 01:02 PM - Thread Starter
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Quote:
Originally Posted by amnesia0287 View Post
I guess the easiest way to ask is, has anyone figured out WHY a ported sub would have more particle velocity?
Quote:
Originally Posted by 3ll3d00d View Post
Substantially smaller radiating area is the major difference
Quote:
Originally Posted by amnesia0287 View Post
So ported subs actually have a different radiation pattern?
Quote:
Originally Posted by 3ll3d00d View Post
you mean how the soundwave propagates beyond the port? if so, no.
Below is a good article on Sound Intensity and the relationship with wave propagation, pressure, and particle velocity. It doesn't directly answer your question about ported designs (@3ll3d00d's answer was appropriate), but should give you a better understanding of the properties involved.

https://www.bksv.com/media/doc/br0476.pdf

You also asked how PVL is measured: Sound Intensity and particle velocity can be measured by Sound Intensity Meters or PVL meters.

See below:


Sound Intensity, Particle Velocity, and Pressure Visualized...



1st - Microflown Acoustic Camera



2nd - Sound Intensity Mapping of a Speaker


3rd - Low Frequency Mapping of Sound Intensity of Speaker/Subwoofer


Last edited by dominguez1; 02-02-2017 at 01:05 PM.
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post #1810 of 3131 Old 02-02-2017, 03:41 PM
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Thank you dominguez1 really interesting paper and videos.
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post #1811 of 3131 Old 02-03-2017, 05:08 AM
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Because of WAF, I have decided to sell my Behringer B1200D. I placed it in the classifieds, if anyone is interested.

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post #1812 of 3131 Old 02-03-2017, 06:57 AM
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@dominguez1

After I looked at the tests more those do not show what I am asking. Is there a ported sub compared to a sealed subwoofer that both have identical or very close frequency responses when measured @ ground plane.

Because if you just take a ported sub and plug the port and crank the now sealed sub up to try to match the frequency response in your room and hit the same SPL as the ported, a lot of what is being measured is influenced by the room. So I am not sure how that would work?

Measure ground plain they will look very different if you took a ported sub, measure and then plugged the port and measure the same sub. And you can't just EQ it to make a sealed sub have the same FR and SPL as a ported sub, you will run out of Xmax or power handling trying to make a sealed sub hit the same dB a ported sub will around its tuning frequency or bandpass where it is most efficient. If you could EQ a sealed sub to have the same FR and have the same output of a ported sub people wouldn't build ported, would they?

Also with the Rhythmic 15 compared to the 1200d, at what frequency range were they compared? 47hz? They have totally different frequency responses so one will rule down low for tactile feel and one will beat the other up higher where each is most efficient. Edit: Are you saying at 47hz the 1200D wins? But what about at 20hz?

Maybe I am misunderstanding some of the tests and comparisons but it appears to me that some of the tests are not comparing apples to apples.

I'll post a hypothetical frequency response graph of what the Rythmik(blue) would look like comparing to the 1200d(green) so there is a visual to look at. And I'll so the same for a ported(red) vs sealed(yellow) using the same subwoofer in the same sized box.

I am not trying to debate that ported doesn't give more tactile feel than sealed, I just wonder how accurate are some of the comparisons or maybe I am missing something still.
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post #1813 of 3131 Old 02-03-2017, 07:22 AM
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Nearfield Ported MBM for Increased Mid-Bass Tactile Response

Also to add to the above post... If TR is greatly increased at port tune what about the rest of the FR? Wouldn't you want a more linear TR rather than a holy sh*t moment at only a certain frequency?


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post #1814 of 3131 Old 02-03-2017, 07:48 AM
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I want the Holy Sh*t feeling!!!!!
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post #1815 of 3131 Old 02-03-2017, 07:57 AM
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Originally Posted by XBR11 View Post
I want the Holy Sh*t feeling!!!!!


I do too - but at every possible appropriate moment. Not just certain scenes that have a specific frequency.


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post #1816 of 3131 Old 02-03-2017, 08:19 AM
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Originally Posted by bouf0010 View Post
If TR is greatly increased at port tune what about the rest of the FR? Wouldn't you want a more linear TR rather than a holy sh*t moment at only a certain frequency?
I think your questions are addressed here:
https://www.avsforum.com/forum/113-su...st-thread.html
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Did you really need to quote that entire post in your reply?
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Don't guess, measure: https://www.avsforum.com/forum/91-au...l#post22789786
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post #1817 of 3131 Old 02-03-2017, 08:26 AM - Thread Starter
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Quote:
Originally Posted by bscool View Post
@dominguez1

After I looked at the tests more those do not show what I am asking. Is there a ported sub compared to a sealed subwoofer that both have identical or very close frequency responses when measured @ ground plane.

Because if you just take a ported sub and plug the port and crank the now sealed sub up to try to match the frequency response in your room and hit the same SPL as the ported, a lot of what is being measured is influenced by the room. So I am not sure how that would work?
No. When taking a single frequency like many of these tests, room gain is not a factor as both the ported configuration and sealed configuration will benefit from the exact same room gain. So room gain is not a factor.

Quote:
Measure ground plain they will look very different if you took a ported sub, measure and then plugged the port and measure the same sub.
Ground plane characteristics aren't a factor in these single frequency tests as the frequency is well within the passband of both configurations. As mentioned above, room gain will benefit them equally.

Quote:
And you can't just EQ it to make a sealed sub have the same FR and SPL as a ported sub, you will run out of Xmax or power handling trying to make a sealed sub hit the same dB a ported sub will around its tuning frequency or bandpass where it is most efficient.
In these single frequency tests, the SPL was with not high enough to push the limits of power or xmax, so not a factor.

Quote:
Also with the Rhythmic 15 compared to the 1200d, at what frequency range were they compared? 47hz? They have totally different frequency responses so one will rule down low for tactile feel and one will beat the other up higher where each is most efficient.
I think you're confused with the premise of the tests.

The hypothesis was that around port tune:

  1. Ported produces more Particle Velocity and subsequently increased Sound Intensity given the same SPL
  2. Because of the increased Sound Intensity, Vibration or Tactile Response is also increased.

For Point 1:


The increased PVL levels around the port tune have been validated by hornesp as found by @3ll3d00d . Below is the graph as shown in the first post comparing a 14hz tuned sub vs a sealed sub. Here is his model :



You can see the increased levels start about an octave before.

For Point 2:


The Vibsensor graphs have validated that there is more Vibration or TR around tune given the same SPL.

Quote:
Edit: Are you saying at 47hz the 1200D wins? But what about at 20hz?
Yes, in the test with the FV15HP and 1200D, the 1200D shows more TR and "wins" because the frequency tested is near the tune of the 1200D. At 20hz, the FV15HP would obviously win as that is not in the 1200D's passband. Assuming that it was (for illustrative purposes), the FV15HP would likely produce more TR because it is closer to the tune of the FV15HP where PVL is higher.
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Last edited by dominguez1; 02-03-2017 at 08:51 AM.
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post #1818 of 3131 Old 02-03-2017, 08:40 AM - Thread Starter
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Originally Posted by bouf0010 View Post
Also to add to the above post... If TR is greatly increased at port tune what about the rest of the FR? Wouldn't you want a more linear TR rather than a holy sh*t moment at only a certain frequency?


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See graph above. Increased PVL starts about an octave before tune and is a gradual increase, not a sudden spike.
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post #1819 of 3131 Old 02-03-2017, 08:56 AM
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Because of WAF, I have decided to sell my Behringer B1200D. I placed it in the classifieds, if anyone is interested.
Dang...that was quick.
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post #1820 of 3131 Old 02-03-2017, 09:08 AM
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Quote:
Originally Posted by dominguez1 View Post
No. When taking a single frequency like many of these tests, room gain is not a factor as both the ported configuration and sealed configuration will benefit from the exact same room gain. So room gain is not a factor.





Ground plane characteristics aren't a factor in these single frequency tests as the frequency is well within the passband of both configurations. As mentioned above, room gain will benefit them equally.





In these single frequency tests, the SPL was with not high enough to push the limits of power or xmax, so not a factor.





I think you're confused with the premise of the tests.



The hypothesis was that around port tune:




  1. Ported produces more Particle Velocity and subsequently increased Sound Intensity given the same SPL
  2. Because of the increased Sound Intensity, Vibration or Tactile Response is also increased.



For Point 1:




The increased PVL levels around the port tune have been validated by hornesp as found by @3ll3d00d . Below is the graph as shown in the first post comparing a 14hz tuned sub vs a sealed sub. Here is his model :







You can see the increased levels start about an octave before.



For Point 2:




The Vibsensor graphs have validated that there is more Vibration or TR around tune given the same SPL.







Yes, in the test with the FV15HP and 1200D, the 1200D shows more TR and "wins" because the frequency tested is near the tune of the 1200D. At 20hz, the FV15HP would obviously win as that is not in the 1200D's passband. Assuming that it was (for illustrative purposes), the FV15HP would likely produce more TR because it is closer to the tune of the FV15HP where PVL is higher.


Another important point is that the tactile, chest-slamming frequencies are in the 60-70hz range, which a large, sealed sub is not specifically optimized to reproduce.


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post #1821 of 3131 Old 02-03-2017, 09:23 AM
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Dang...that was quick.
Well when she didn't talk to me for 3 hours, I thought it was because she was kind and wanted me to enjoy the new subwoofer.


Turns out I was wrong.

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post #1822 of 3131 Old 02-03-2017, 09:23 AM
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Originally Posted by XBR11 View Post
Because of WAF, I have decided to sell my Behringer B1200D. I placed it in the classifieds, if anyone is interested.
I also sent mine back for refund. I didn't like the looks of them on top of the other subs behind the MLP. If I drop the x-over down to 40z the JBL 4722s really start to kick in on the mid-bass.
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post #1823 of 3131 Old 02-03-2017, 09:34 AM - Thread Starter
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I think I see now where the confusion might be setting in...

Let's tackle the midbass frequencies (50-100hz).

Efficient drivers or highly sensitive drivers for midbass will have more impact than non-efficient drivers in this frequency range because it will handle and reproduce the transients more accurately and with less compression. The result is more perceived "slam" from the efficient driver vs non-efficient driver.

The key point here is that it is reproducing the content more accurately...but it doesn't change the physics.

For example, take an efficient 18in driver and non efficient 18in driver, put them in an optimal box for each and feed optimal power. Now run them through the same single frequency tests as I explained above (same spl).

In hornresp, they will likely model similar PVL levels (in the models that have been run, this has been the case). Given that they have the same PVL levels, sound intensity and resulting TR will likely be similar when measuring through Vibsensor.

BUT WAIT? How can that be? The efficient driver has been confirmed by many to have more "slam". It's because it reproduces the Transients more accurately. This could equate to more TR if the non-efficient driver is compressing...looking at the equation:

SIL = SPL * PVL

Assuming PVL is the same, it's all about SPL. If the non-efficient driver is compressing at some frequencies, it may not be reproducing the same transient SPL levels as the efficient driver. If SPL is lower at those transients, then SIL or TR or "slam" will also be lower.

The ultimate TR midbass combo would be an efficient driver combined with a midbass port tune: accurate transients and higher TR on top of that because of the port tune.

It's the port that changes the physics because there is increased PVL levels...not because it is more efficient in the range.

My .02 anyway...

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post #1824 of 3131 Old 02-03-2017, 10:14 AM
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Another important point is that the tactile, chest-slamming frequencies are in the 60-70hz range, which a large, sealed sub is not specifically optimized to reproduce.
Based on what? That doesn't seem accurate to me at all. To me it seems like that's the area they are most capable:



This doesn't have anything to do with SI though
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post #1825 of 3131 Old 02-03-2017, 01:21 PM
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I have tried to understand and keep up with this (really long) thread but find it a bit hard to conclude what the best option for a home theater enthusiast is, given the benefits of a sealed sub do exist.

I would like to offer my hypothesis as to why a ported sub would create more tactile sensation over a sealed one at the same SPL, if I may:

The ported sub would simply move more air than just the woofer surface would, resulting in a bigger "shockwave" particle effect even though the measured SPL (when calibrated) would be the same.
So the question is, if we would actually look at the following example:

1 Ported Sub vs 2 Sealed Subs at the same measured SPL - which one would generate more tactile response? If what I'm saying is correct then 2 sealed subs would generate the same SPL when calibrated (each playing about 6db less?) but they would be moving twice more air than 1 sealed sub. Therefore more tactile sensation potentailly competing or even extending that of 1 ported sub becuase port would have to have at least some energy loss inefficiency by design (unless we're talking Regenerative Transmission Line akin to Wisdom Audio STS subs).

Or another question - what if we compare a 12 inch ported sub with a 21 inch sealed one at the same measured SPL. Does the balance change then? If so, then it would again mean that it's more about having more air particles energized and having a bigger physical shockwave.

Would this be a correct way of looking at it?
Ie, it's not that sealed subs can't get the same tactile sensation, it's just that "tactile bang per sub" is higher with the ported sub but sealed subs can achieve the same effect if you have more of them / having larger drivers.

Last edited by ViciousDelicious; 02-03-2017 at 01:33 PM.
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post #1826 of 3131 Old 02-03-2017, 01:56 PM
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If what I'm saying is correct then 2 sealed subs would generate the same SPL when calibrated (each playing about 6db less?) but they would be moving twice more air than 1 sealed sub.
particle velocity scales with frequency (angular velocity) and displacement. If you add a 2nd driver and keep spl the same then the excursion of each is reduced and hence PVL will remain unchanged.

IIRC all of this is covered in the first few posts of the thread.
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post #1827 of 3131 Old 02-03-2017, 06:24 PM
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Yes. I think there's a certain amount of resistance to this because it's a novel concept, and flies in the face of what had been conventional wisdom for some time. The beauty of this is that it doesn't cost much to try it out. Movies like Star Trek Beyond are entirely different experiences with the addition of a 1200 properly configured Nearfield. . I was shocked at how much it added to the experience, and I've been a home theater enthusiast since the 80's.


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post #1828 of 3131 Old 02-03-2017, 08:17 PM
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So how would you compare two different sealed subs if I wanted to compare tactile feel? Use your same test method of comparing them at 1 specific frequency and measure tactile feel?

Because I have a Submersive and also a PSA XS30 both sealed subs that are very similar, so I would test each at say 50hz using the same SPL?

Because I know from actually playing each the Submersive is much more tactile and kicks harder and plays lower. Just trying to figure this out or how it compares or would apply when comparing sealed subs.

I can't use the Vibsensor app on my windows phone or I would do the testing and comparison myself .

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I think I see now where the confusion might be setting in...

Let's tackle the midbass frequencies (50-100hz).

Efficient drivers or highly sensitive drivers for midbass will have more impact than non-efficient drivers in this frequency range because it will handle and reproduce the transients more accurately and with less compression. The result is more perceived "slam" from the efficient driver vs non-efficient driver.

The key point here is that it is reproducing the content more accurately...but it doesn't change the physics.

For example, take an efficient 18in driver and non efficient 18in driver, put them in an optimal box for each and feed optimal power. Now run them through the same single frequency tests as I explained above (same spl).

In hornresp, they will likely model similar PVL levels (in the models that have been run, this has been the case). Given that they have the same PVL levels, sound intensity and resulting TR will likely be similar when measuring through Vibsensor.

BUT WAIT? How can that be? The efficient driver has been confirmed by many to have more "slam". It's because it reproduces the Transients more accurately. This could equate to more TR if the non-efficient driver is compressing...looking at the equation:

SIL = SPL * PVL

Assuming PVL is the same, it's all about SPL. If the non-efficient driver is compressing at some frequencies, it may not be reproducing the same transient SPL levels as the efficient driver. If SPL is lower at those transients, then SIL or TR or "slam" will also be lower.

The ultimate TR midbass combo would be an efficient driver combined with a midbass port tune: accurate transients and higher TR on top of that because of the port tune.

It's the port that changes the physics because there is increased PVL levels...not because it is more efficient in the range.

My .02 anyway...

Last edited by bscool; 02-03-2017 at 08:29 PM.
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post #1829 of 3131 Old 02-03-2017, 08:27 PM
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Originally Posted by healthnut View Post
Yes. I think there's a certain amount of resistance to this because it's a novel concept, and flies in the face of what had been conventional wisdom for some time. The beauty of this is that it doesn't cost much to try it out. Movies like Star Trek Beyond are entirely different experiences with the addition of a 1200 properly configured Nearfield. . I was shocked at how much it added to the experience, and I've been a home theater enthusiast since the 80's.


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I need to do more A/B comparisons now that I have the pair of B1200. I haven't wanted to watch any movies without them on! I have shut the pair off a couple times just to see, but only briefly in one movie. If anything, I need to remember what my old setup was like before the midbass nearfield extravaganza.

I've got a pair of Crowson actuators coming next week to pick up the low end TR where the B1200 leave off...sooo excited! 😃

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post #1830 of 3131 Old 02-03-2017, 08:40 PM
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I'll be curious what you think when you get your Crowsons. I have tried my Kappa Pro 18" tuned to 41hz behind me and I can feel it more when right behind my chair, but I can tell it is coming from behind and I prefer it in front between my with the LRC since I still get some tactile feel from it although not as intense but I feel it coming from up front. And the Crowsons feel more "all" around me feeling, kind of enveloping. It could also be because my priority is music over movies.

I remember reading someone else on here that had both and liked them when combined.


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I need to do more A/B comparisons now that I have the pair of B1200. I haven't wanted to watch any movies without them on! I have shut the pair off a couple times just to see, but only briefly in one movie. If anything, I need to remember what my old setup was like before the midbass nearfield extravaganza.

I've got a pair of Crowson actuators coming next week to pick up the low end TR where the B1200 leave off...sooo excited! 😃
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