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Your Home Theater ULF Score - Page 47

post #1381 of 1882
They are talking sub 20hz not just 20hz.
post #1382 of 1882
Quote:
Originally Posted by Pain Infliction View Post

They are talking sub 20hz not just 20hz.

See! Look at DW's last post. Now, DW has one S2. He's was thinking of already adding another. But going to the more insane route which is DIY.Everyone wants more sooner or later. Lol! Just saving you some time and money
Especially the price increase in 2014. Like I said in your thread pain. For a couple more hundreds I'd go with two cap 2400 which would equal to a single OS. Just saying. Because the cost of 1 S2 to 2 cap 2400 is close. And like I said talk to Jeff first. He does good with multi purchase.
post #1383 of 1882
Quote:
Originally Posted by rhed View Post

See! Look at DW's last post. Now, DW has one S2. He's was thinking of already adding another. But going to the more insane route which is DIY.Everyone wants more sooner or later. Lol! Just saving you some time and money
Especially the price increase in 2014. Like I said in your thread pain. For a couple more hundreds I'd go with two cap 2400 which would equal to a single OS. Just saying. Because the cost of 1 S2 to 2 cap 2400 is close. And like I said talk to Jeff first. He does good with multi purchase.
I have one location I can put a sub and dual cap2400's would take up more real estate than an OS. I didn't want an OS because I do not need that amout of headroom nor do I want that big ass sub lol. I also wanted the s2 for the extension as well. If I ever decide to get a second s2 I can do that and still have more output. Also, dual passive 2400's would be the same price as am active s2. I want to use the amps that are available because of the efficiency of them and do not have to worry about dedicated circuits and fans or anything else. I am stepping out of the DIY world and want simple and proven.
post #1384 of 1882
http://www.avsforum.com/t/1387178/archaeas-kansas-city-blind-subwoofer-shootout-2012/840#post_24107938
Quote:
Originally Posted by Pain Infliction View Post

I have one location I can put a sub and dual cap2400's would take up more real estate than an OS. I didn't want an OS because I do not need that amout of headroom nor do I want that big ass sub lol. I also wanted the s2 for the extension as well. If I ever decide to get a second s2 I can do that and still have more output. Also, dual passive 2400's would be the same price as am active s2. I want to use the amps that are available because of the efficiency of them and do not have to worry about dedicated circuits and fans or anything else. I am stepping out of the DIY world and want simple and proven.

One more thing Pain.. Ask Archaea about his ported Caps. He knows a lot about JTR's..
post #1385 of 1882
Quote:
Originally Posted by rhed View Post

http://www.avsforum.com/t/1387178/archaeas-kansas-city-blind-subwoofer-shootout-2012/840#post_24107938
One more thing Pain.. Ask Archaea about his ported Caps. He knows a lot about JTR's..
I really appreciate that you are trying to help me, but my mind is made up. I do not think you are understanding what my reasoning is. I have research a lot and also those meets are somewhat inconclusive for my needs. There was never an S2 at those meets and the cap S actually won the blind test, and some people thought it was the OS. So that actually helps me out even more considering the S2 is two Cap S's.
post #1386 of 1882
Thread Starter 

So, I did the ported vs sealed shake test this morning. I placed the 1 FTW21 behind the main LP ~1.5ft away from the mic, and ran a 15hz sine wave at 88db and 103db and measured the vibration using the Vibration Meter app on the android and recorded the results. I did the same using 1 FV15HP.

 

Here are the results:

 

88db 15hz sine wave test

 

FV15HP

  • Mean = 3.4
  • Max = 5.4

 

FTW21

  • Mean = 2.6
  • Max = 5.0

 

Observations: IMO, negligible difference from the Vibration Meter.

 

103db 15hz sine wave test

 

FV15HP

  • Mean = 5.6
  • Max = 7.6

 

FTW21

  • Mean = 4.3
  • Max = 6.9

 

Observations: More shaking occurred with the FV15HP as the Mean values are a significant enough difference IMO. However, there also looks to be more 2nd harmonic distortion (30hz) compared to the FTW. This could be contributing to the additional shake. I will say that even though it appears that 30hz is showing on the graph, I did not hear anything. I even played it at much higher volumes, and I didn't hear the 30hz signal...

 

Conclusion:

  • Based on this single test alone, and with a 15hz sine wave, at higher volumes, it looks like the FV15HP shakes does shake more, but that is likely because of the 2nd harmonic distortion. At lower volumes, the FV15HP and FTW21 had similar tactile feedback.
  • It would have been very interesting to compare duals to duals where they are both 3ft away from the mic to see if there was any difference. Unfortunately, it's way too much trouble for me to do!

 

Testing Note:

It's surprising how much more harmonic distortion there is when the mic is placed even a foot or two more close to the sub. It's also amazing how adding another sub significantly reduced the harmonic distortion.

 

Here is the a 101db 15hz sine wave with dual FV15HPs (1 is 1.5ft away, 1 is 3ft away):

Compare that with the 103db sine wave above, and there is quite a difference.

 

Move the FV15HP from 1.5ft away to 3ft away so they are both 3ft away:

This is at 96.6db for the 15hz sine wave. Compare that with the 88db, and you can see a huge difference.

 

Now look at the FTWs 13.5ft away:

This is at 117db Max SPL. Compare that to the 103db nearfield above, and it's a huge difference.


Edited by dominguez1 - 12/23/13 at 7:12am
post #1387 of 1882
Why do you suppose there's so much drop in second and third harmonic distortions? How much would you think the addition of a third FV15HP is going impact harmonic distortion as the difference between one and two FV15HPs, in my opinion is doubly huge.

In our case, at three feet (1m) from the MLP, one is nearfield and the second one is ten feet (3m) from the MLP, on the opposite wall.
post #1388 of 1882
"Why do you suppose there's so much drop in second and third harmonic distortions?"

distortion scales pretty well with spl, increasing at about 2x, roughly.

two subs are +6db vs one sub, so distortion is reduced by about 12db at the same spl level.
post #1389 of 1882
"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."

there are two topics there.

pressure vessel gain is the effect where the room can no longer support the wave, so the entire room becomes pressure modulated. this is the zone in between the "first" mode (which is actually the zero mode) and the "second" mode (which is the first measured mode)...or put another way, it is a mode free zone. pressure vessel gain is also a bit of a sliding scale depending on the wave length, not a brick wall, as it transitions from almost zero to almost 12db/oct.

room gain is the increase in spl provided by the walls, ceiling and floor. this is the cancellations, reflections, and all the rest of it zone.
post #1390 of 1882
Quote:
Originally Posted by LTD02 View Post

"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."

there are two topics there.

pressure vessel gain is the effect where the room can no longer support the wave, so the entire room becomes pressure modulated. this is the zone in between the "first" mode (which is actually the zero mode) and the "second" mode (which is the first measured mode)...or put another way, it is a mode free zone. pressure vessel gain is also a bit of a sliding scale depending on the wave length, not a brick wall, as it transitions from almost zero to almost 12db/oct.

room gain is the increase in spl provided by the walls, ceiling and floor. this is the cancellations, reflections, and all the rest of it zone.

Convenient explanation, but not supported by the evidence. cool.gif
post #1391 of 1882
Quote:
Originally Posted by bossobass View Post

Convenient explanation, but not supported by the evidence. cool.gif

And your alternative theory is?

In the meantime, for room smoothing purposes, I was hoping to get by with two subs and not have to purchase a third.

(the wife is already prepared for this eventuality)
post #1392 of 1882
In-room harmonic distortion, as a %, should always be accompanied by the FR taken from the same mic position the sine wave was measured from.

For example, if the sine wave (fundamental) is 15 Hz and with one distance measurement the FR shows a 30 Hz peak, that measurement will have much higher 2HD. Changing the distance (either the mic or the sub) you may see a dip at 30 Hz and the 2HD, as a percentage, will drastically drop.

As my measurements show, as you shorten the distance to a sealed subwoofer, the 15 Hz fundamental drops in relation to 30, 45, 60 Hz, etc., so the THD, as a %, will increase. Conversely, as you increase the distance, boundary gain increases the fundamental more so than the harmonics and THD will drop accordingly.

All gain derived from placing a subwoofer in a room is derived from progressively constructive reflections. The pressure waves do not turn into water, nor does the ambient barometric pressure of the room increase or decrease. The articles repeatedly posted by LTD concern behavior in an enclosed cylinder and have nothing whatever to do with a subwoofer in a room in your home.

Many posters over the years have attempted to move the listener inside his subwoofer enclosure in wild stabs at explaining observed phenomena from low frequency reproduction in-room. The explanations are never explained, just stated as matter-of-fact, and they never actually coincide with the massive accumulated data provided by members who own subwoofers, place and calibrate them in their room and measure the process and results.

Trying to apply non-applicable data will only forever obscure the answer to Dom's test results.

But hey, if you prefer the dilithium crystal explanation, that's fine too. smile.gif
post #1393 of 1882
Quote:
Originally Posted by bossobass View Post

But hey, if you prefer the dilithium crystal explanation, that's fine too. smile.gif

The beauty of being an ignorant, we'll believe anything. biggrin.gif

At my level of understanding, all I expect out of the deal is some kick butt sound.

(my current problem is a ringing center channel horn and my understanding, I'm going have to wrap it in damping material to get it to shut up)

...confused.gif
post #1394 of 1882
How about this, near field placement takes out the room for sealed subs. So the room is what adds to the increased low end and decrease in THD. The point of Bosso's graph. When Dom moved the subs away to 3 feet the THD dropped. It happens in every room, try measuring and you will see it happen. I am going to measure my near field soon because I have a Bassis on the way and I will show the differences between 2 inches away(no room) and at my LP 12 feet away.
post #1395 of 1882
Thread Starter 
Quote:
Originally Posted by Archaea View Post

Guys - somebody with a pair of Rythmiks please accept my challenge. There are at least three of you in this thread who have spoken up recently that could do it.

The challenge I put up to beeman is to test his claim of thinking he can hit 115dB at 10hz with a pair or a tri setup of Rythmiks FV15HP in a home theater room at the MLP.

What does this mean? To say you can claim 115dB at 10hz (reference at 10hz) means no audible sound (harmonic distortions), and no offsetting port noise. For the purposes of this thread - Reference subwoofer output at 115dB means usable output --- not junk disgraceful sound.

I say it won't happen. At least two of you guys say it can. Time to put up proof or quit making senseless claims...

I got my public touché ready if it's needed. I'm not picking on Rythmik. I'm talking about junk unrealistic, borderline absurd claims in a thread where the opposite horizon is the goal. My same opinion would apply to pretty much any ported sub where someone said they could achieve reference levels below a bass reflex sub's port tune or at point on a sub where the vendor introduced a steep HPF above that point. My hypothesis --- If you hit 115dB at 10hz with a pair of Rythmiks it's going to be whistling Dixie (as a friend likes to say) through that single open port, and making all kinds of harmonic distortion (audible sound), perhaps even making mechanical distress sounds, and generally just sound horrible.

Prove me wrong. Video it with a cell phone and share the vid.........if it is even close.

I'd test it tonight if I had the Rythmik subs on hand. I've thrown up several videos showing different things people asked me about on these forums in the last few years. It'd take 10 minutes tops if you have measuring equipment handy.

My public touché is at the ready...

beeman I'll even give you a thumbs up to add to your immense collection if this experiment pans out in your favor.

It's Friday night - I'm feeling spunky...

Test is here:

 

http://www.avsforum.com/t/1507234/rythmik-fv15hp-10hz-test

 

115.8 Max SPL at 10hz. :)

 

Keep the responses in that thread please...

post #1396 of 1882
Quote:
Originally Posted by dominguez1 View Post

115.8 Max SPL at 10hz. smile.gif

By 0.8dB.....I'll take it. biggrin.gif

(sorry, wrong thread to post in)
post #1397 of 1882
Quote:
Originally Posted by dominguez1 View Post

ironhead, these charts are awesome! Sorry if I missed this, but you had all these subs at a GTG? That's pretty incredible if you did! Did you frequency and level match the subs?

Yeah these were taken last year at this GTG.
http://www.avsforum.com/t/1434901/northeast-october-20th-gtg-results-thread

We did try to level match but did not EQ so the FR of each sub are quite different. I forgot how different they were so that definitely has to be taken into account when looking at the speclab captures. However the submersives, FV15hp and E15 are pretty similar between 15hz and 30hz.

http://www.avsforum.com/t/1434901/northeast-october-20th-gtg-results-thread#post_22512892
Quote:
Originally Posted by dominguez1 View Post

Based on these charts, what objective data can we (or did you) conclude from these?

Love the format...nice work!

Going through the captures, I'm not sure if any firm conclusions should be made since I can't remember all of the MV settings used and the differences in FRs, but here are some of my observations. It surprised me how similar the outputs of the FV15, E15, XS15 and submersives were between 20-40hz. Of course they will not all have the same max output, but at the levels used and in that room, they were very similar. It was also interesting to me how easily it was to see the differences in distortion on some clips. I also looked a lot comparing the FV15HP and E15. The ULF scores have the FV15 twice the E15 at all frequencies, but the captures do not back that up. The E15 had more output below 15hz and similar output above at the expense of higher distortion. It would probably change in a different room, at higher levels, or with EQ, but something to think about.

Lastly, I wanted to try and spark some more interest in others to take their own captures. I started a thread awhile ago to try and put together a method to take mic captures that can be directly compared like the digital captures, but there was not much interest. I've said it a number of times already, but I think speclab captures of different sub setups in different rooms would be an excellent set of data to refine or verify the ULF scores. Theoretical discussions based on outdoor measurements are great, but nothing beats data from in-room measurements of real content. So far from my testing, I have a way to accurately import a mic calibration into speclab. Now just need to put together a calibration method so the results are comparable and repeatable. If anyone is interested in working with me on this, PM me.
post #1398 of 1882
This is my next step, getting some spec lab graphs however I need the cal files for them to be accurate below 20hz.
post #1399 of 1882
Quote:
Originally Posted by MKtheater View Post

This is my next step, getting some spec lab graphs however I need the cal files for them to be accurate below 20hz.

Send me your mic cal file and I will convert it to a spec lab filter and instructions to load it into speclab.
post #1400 of 1882
Quote:
MK I have a Bassis on the way

Are you talking WM8 BASSIS MK? http://www.marchandelec.com/wm8.html
post #1401 of 1882
Quote:
Originally Posted by MKtheater View Post

How about this, near field placement takes out the room for sealed subs. So the room is what adds to the increased low end and decrease in THD. The point of Bosso's graph. When Dom moved the subs away to 3 feet the THD dropped. It happens in every room, try measuring and you will see it happen. I am going to measure my near field soon because I have a Bassis on the way and I will show the differences between 2 inches away(no room) and at my LP 12 feet away.

Been there done that! It is fun to test for sure smile.gif I already have some graphs on the subject and these further show what Bosso et al have been discussing here. Second post:

http://www.avsforum.com/t/1466294/beastaudios-diy-sub-and-main-testing-measurement-thread/0_60
post #1402 of 1882
Quote:
Originally Posted by steve nn View Post

Are you talking WM8 BASSIS MK? http://www.marchandelec.com/wm8.html
Quote:
Originally Posted by steve nn View Post

Are you talking WM8 BASSIS MK? http://www.marchandelec.com/wm8.html

Yes, the mono version.
post #1403 of 1882
Quote:
Originally Posted by ironhead1230 View Post

Send me your mic cal file and I will convert it to a spec lab filter and instructions to load it into speclab.

OK, where to?
post #1404 of 1882
Quote:
Originally Posted by MKtheater View Post


Yes, the mono version.

Awesome! yeah it costs a little bit, but I’ll be very surprised if you’re not really happy with it.
post #1405 of 1882
I am wondering how much effects will be created from it. I hope enough besides a flatter graph. Here is my response



Full range

post #1406 of 1882
Thread Starter 

Based on this test here, it shows that SPL as measured by an SPL measurement device does not solely determine the tactile sensation for ULF. Even though the farfield subs measured at the same SPL as the nearfield subs, the couch shaking effect was much more pronounced with the nearfield subs. I had to increase the farfield subs by 20db to get a similar shaking effect. The theory is that acoustic energy is what primarily drives the tactile feeling, and acoustic energy is stronger when the distance is close and is produced directly from the sub (as opposed to SPL from room gain). SPL meters are not the right device to measure this acoustic energy. At this point, this is still an open question as to how this acoustic energy can be accurately measured.

 

Since nearfield subs drive the tactile feeling as compared to farfield subs, the frequency response of the nearfield subs should give a better representation of tactile feeling. In my room, the dual FV15HPs have the below nearfield response:

 

Based on the above, you would think I would have the most tactile feeling 25 and 50hz. I would also have good tactile feeling from 11hz to 18hz as well.

 

So I took the Vibration Meter and measured the vibration between the frequencies of 10hz to 80hz and plotted on a chart with the response of my nearfield FV15HPs. The main volume on the receiver as -20db for this test.

 

Here is the Vibration Meter scale (Mercalli scale):

 

1.0 - Instrumental. Felt by animals
2.0 - Weak. Felt indoors by a few people
3.0 - Slight. Felt indoors by several
4.0 - Moderate. Hanging objects swing
5.0 - Rather Strong. Dishes broken
6.0 - Strong. Heavy furniture moved
7.0 - Very Strong. Difficult to stand
8.0 - Destructive. Fall of walls
9.0 - Violent. Noticeable ground cracks
10.0 - Intense. Almost destroyed
11.0 - Extreme. Rails bent greatly
12.0 - Cataclysmic. Total destruction

 

As you can see by the pink line, I get the majority of the couch shaking in my room starting at 11hz or so to about 21hz. After that, the couch shaking levels out to barely any shaking at less than 1. You can see by the blue line, that the shaking does not match the frequency response entirely, especially past 20hz where I have the strongest SPL, but the weakest couch shaking.

 

I have two theories why this is: 1. The resonant frequencies of my couch, 2. ULF frequencies wobble the foundation of the couch (imagine someone grabbing the base of your couch and shaking) with slower vibrations, whereas the higher LF frequencies are quicker vibrations and more directional (e.g. back massage chairs) as well as have the kick in the chest type sensations. The ladder isn't accurately measured by a phone on the based of the couch and perhaps why it drops off in the audible frequencies. It would be interesting if I could somehow measure the shaking that is happening on the cushions behind your back, as I'm sure there is lots of shaking going on in the upper bass frequencies.

 

post #1407 of 1882
Quote:
Originally Posted by dominguez1 View Post

Based on this test here, it shows that SPL as measured by an SPL measurement device does not solely determine the tactile sensation for ULF. Even though the farfield subs measured at the same SPL as the nearfield subs, the couch shaking effect was much more pronounced with the nearfield subs. I had to increase the farfield subs by 20db to get a similar shaking effect. The theory is that acoustic energy is what primarily drives the tactile feeling, and acoustic energy is stronger when the distance is close and is produced directly from the sub (as opposed to SPL from room gain).

Think fluid dynamics.

Our nearfield sub is three feet from where I sit to where the wife sits, two feet further away. She feels the floor, but not tactile sensation.

The point, the further from the end of the hose, the more dispersed (weak) the stream at the end of the hose; fluid dynamics.
post #1408 of 1882
Thread Starter 
Quote:
Originally Posted by dominguez1 View Post
 

So, I did the ported vs sealed shake test this morning. I placed the 1 FTW21 behind the main LP ~1.5ft away from the mic, and ran a 15hz sine wave at 88db and 103db and measured the vibration using the Vibration Meter app on the android and recorded the results. I did the same using 1 FV15HP.

 

Here are the results:

 

88db 15hz sine wave test

 

FV15HP

  • Mean = 3.4
  • Max = 5.4

 

FTW21

  • Mean = 2.6
  • Max = 5.0

 

Observations: IMO, negligible difference from the Vibration Meter.

 

103db 15hz sine wave test

 

FV15HP

  • Mean = 5.6
  • Max = 7.6

 

FTW21

  • Mean = 4.3
  • Max = 6.9

 

Observations: More shaking occurred with the FV15HP as the Mean values are a significant enough difference IMO. However, there also looks to be more 2nd harmonic distortion (30hz) compared to the FTW. This could be contributing to the additional shake. I will say that even though it appears that 30hz is showing on the graph, I did not hear anything. I even played it at much higher volumes, and I didn't hear the 30hz signal...

 

Conclusion:

  • Based on this single test alone, and with a 15hz sine wave, at higher volumes, it looks like the FV15HP shakes does shake more, but that is likely because of the 2nd harmonic distortion. At lower volumes, the FV15HP and FTW21 had similar tactile feedback.
  • It would have been very interesting to compare duals to duals where they are both 3ft away from the mic to see if there was any difference. Unfortunately, it's way too much trouble for me to do!

 

So, back to the ported shakes more than sealed debate (at least in my room):

 

Based on my test above, ported does shake more than sealed. I had originally thought this because ported nearfield had higher 2nd order harmonic distortion (30hz).

 

 

However, look at 30hz in the above plot? There is hardly any shaking going on compared to 15hz where it is the strongest.

 

If when playing a 15hz sine wave in my room, a ported sub shakes more than sealed, and harmonic distortions (above 20hz or so) don't provide any couch shaking, what is causing the additional shaking by the ported sub?

 

Perhaps the ported design produces more acoustic energy than sealed?

post #1409 of 1882
I know you're ignoring me on this issue and have been for some time.

I'm sharing my nearfield experience and what my rational is. From personal experience, it's energy disbursement. The further from the energy source, the less one is able to perceive it's existence.

Flexture of the floor is a general transference, over a large area. Tactile sensation is a nearfield experience and one has to jack up the energy source to pass the sensation on down the line in the same way, dB falls off at 6dB per doubling of distance.

With the nearfield subwoofer close at my back, I feel lots of tactile sensation but the wife, two or three feet to my side, in a separate chair, doesn't feel anything in this regard.

(subwoofers; two FV15HPs)

(it's rude to intentionally ignore a sincere participant and if you will, if you don't wish me to participate in this conversation, man up and say so)

...mad.gif

-
Edited by BeeMan458 - 12/27/13 at 7:58am
post #1410 of 1882
One thing to keep in mind Dom - the results of your tests don't really mean much at this point. <- Read that in a friendly tone of voice, cuz I don't mean that in a disparaging way of course, but as a reminder that any scientific experiment must be carried out repeatedly with many many trials to cover all variables. You are performing tests with only one specific subwoofer, in one specific room, in one house with its own specific construction. You would need many different types of subwoofer builds in many different environments (and/or one acoustically neutral environment) to get the full picture of the relationship between tactile feedback, sub build, frequency, SPLs and placement. So as it is, imho your tests should at best be considered only as indicative, not conclusive.

My point: I think that it would be a good idea to invite others to start doing their own tests to add to your data regarding tactile feedback. Maybe another thread is in order?
smile.gif
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