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Purpose of flat response below 20Hz - Why does it matter? - Page 20

post #571 of 585
Quote:
Originally Posted by Archaea View Post

We did two tests tonight at the Gorilla83 meet. Mixed results on one test and definitive results on the other.
We had three Submersive HPS. One F2 HP, two traditional dual opposed Submersive HPs.

Here was the uneq'ed frequency response in Gorilla83's room as we listened to the three submersives. FR captured 10x's and averaged at MLP.
SeatonSubmersiveHPtriplesFRgraph-noEQ-programmode2.jpg
For the Tracks we used the most recent Incredible Hulk cop car smash scene and a snippet of the Bass I love you clip. We played both clips back to back with a minidsp engaging a HPF at 18hz, and then with the HPF removed. Then we blind tested the two tracks again and had people vote on which A / B replay had deeper bass.
On the incredible Hulk Scene 12 out of 14 people voted correctly in blind voting done by show of hands with eyes closed.
On the Bassotronics - Bass I Love You track (which contained 15 and 7hz content) - nobody could tell and we didn't even blind vote because nobody knew and everyone admitted so before the voting.
I hold a ported sub preference -- generally, and I could tell pretty clearly (and was right) from my seating position which A/B had deeper content on the Hulk footsteps and cop car smash scene because my pant legs shook a bit more and my body seemed to feel a bit more tactile feedback. I voted correctly.
However, On the Bass I Love You Track I couldn't have determined the difference if my life depended on it from that A/B demo.
Interesting to be sure. 12 of 14 indicates that at least on at least some demo clips people can definately tell the difference. We will do additional testing at the Omaha Home Theater tour happening next weekend in at least two theaters --- HuskerOmaha's with four UXL18 drivers, and Desertdome with eight 15" drivers in an infinite baffle setup.

OK, most people noticed infrasonics and you were not even flat for the infrasonics. You were 6 dBs low at 10hz and who knows how much lower at 5 hz. Now imagine if you boosted the low end to have a -3 dBs point at 5 hz! Having 4 times the power just at 10hz makes a difference. That is like having 3 more submersives just for 10 hz.

BTW, that F2 looks amazing! I hope you guys had a blast! I am jeoulous I could not make it!
post #572 of 585
Quote:
Originally Posted by mojomike View Post

How about lawsuits? Any lawsuits?
Filed only by the victims families. I can't wait to see the headlines. "12 Dead in Infrasonic Massacre"
post #573 of 585
Quote:
Originally Posted by Archaea View Post

12 of 14 indicates that at least on at least some demo clips people can definately tell the difference.
Did you get their votes before or after they passed out, threw up, or soiled their drawers?

Also, what about the 3 people who died from the infrasonics? Were you planning to mention that? biggrin.gif
post #574 of 585
I'm still going through all of the speclab captures I have from the GTG, but figured I'd start with these. These were taken with a CSL calibrated Dayton EMM-6 mic and tascam US-144 mkII preamp. I am pretty sure I was able to load the mic calibration into speclab correctly, but left the soundcard calibration out. The soundcard is +-1db down to about 7hz. I did not calibrate the levels, so they can only be compared to other captures I took that night. They cannot be directly compared to captures from anyone else. I didn't do a digital capture of the source. I'll be posting more captures and information in another thread, and possibly some questions for the next time I try this.

As far as I know, there was no difference between the two clips except for a 18hz HPF. If I remember correctly, the subs were about 8db hot and this was at +4 MV with an 80hz crossover.

Incredible Hulk no HPF
Seaton%2520Submerswives%2520-%2520hulk1%2520test%2520no%2520hpf.jpg

Incredible Hulk with 18hz HPF
Seaton%2520Submerswives%2520-%2520hulk1%2520test%252018hz%2520hpf.jpg

Bass I Love You no HPF
Seaton%2520Submerswives%2520-%2520bass%2520i%2520love%2520you%2520test%2520no%2520hpf.jpg

Bass I Love You with 18hz HPF
Seaton%2520Submerswives%2520-%2520bass%2520i%2520love%2520you%2520test%252018hz.jpg

-Mike
post #575 of 585
Thanks Mike!


Good stuff!
post #576 of 585
I don't think they were down 6db at 10hz, there was just a 6db hump around 23hz or so. At what volume was the test run if I may ask?
post #577 of 585
Quote:
Originally Posted by TimVG View Post

I don't think they were down 6db at 10hz, there was just a 6db hump around 23hz or so. At what volume was the test run if I may ask?

To me it is the same thing because that peak is in the wheel house of many movies and will be noticed more over infrasonics(it is anyways when flat). Also you can see there is much more overall energy down low from TIH than bass I love you. Gorilla looks to have similar room gain that I have from the uneq'd graphs. I am just glad to see the guys having fun no matter what their preference is. When I went to my only GTG two subs were compared in similar fashion and just level matched with no EQ and everyone picked the same sub to sounding better(including me). Of course with EQ it could have been different. It was still fun. Now imagine running about 6 submersives with boost down low and a smaller room and that is just about right for me! You guys wonder why I talk about the low end now?
post #578 of 585
Quote:
Originally Posted by ironhead1230 View Post


As far as I know, there was no difference between the two clips except for a 18hz HPF. If I remember correctly, the subs were about 8db hot and this was at +4 MV with an 80hz crossover.

-Mike

Great stuff Mike, I didn't even know you were recording this.

FYI, let me correct the calibration notes. While the subs were +8dB over the mains, the mains ended up calibrated 3dB below reference due to various concerns with gain structure and wanting to not set the outputs of the receiver too far into the +dB range, while also reducing some line induced noise due to the dimmers and grounding.

Translation: +4 on the MV was more like a "calibrated" +1dB MV with the subs +5dB.
post #579 of 585
Didn't follow the discussion but this might help explaining some observations - listening threshold at low frequencies:

post #580 of 585
^ According to that my house curve should look a hell of a lot different than it does now (but I'm not changing it).
post #581 of 585
Quote:
Originally Posted by Auditor55 View Post

Once again, since you say harnful affects only occur at LF 150 dbs or higher.
Scientific Applications and Research Associates (SARA) - This agency's alleged infrasound research showed, "infrasound at 110 - 130 dB would cause intestinal pain and severe nausea. Extreme levels of annoyance or distraction would result from minutes of exposure to levels 90 to 120 dB at low frequencies (5 to 200 Hz), strong physical trauma and damage to tissues at 140 - 150 dB, and instantaneous blastwave type trauma at above 170 dB.

So I should be barfing and farting when I do this? Who knew!!!! biggrin.gif
post #582 of 585
to answer an earlier question
yes the playback of the movie with the low frequencies was more enjoyable than the playback with the hp filter engaged.
conclusion: if you are a person who enjoys your music and movies, your gear, clean distortion free playback, capable of volume that you want in your room yes yes yes you want to be able to reproduce all that is on the dvd or cd. period.
if you don't care about that stuff then this entire discussion does not apply to you
post #583 of 585
http://www.rotarywoofer.com/howlowcanwehear.html

As can be seen in the above link where research was done. Fact is it takes a ton of power, and huge high quality subwoofer drivers to really enjoy much below 20 hz. Your looking at sound pressure levels of 100 to 120 db just to get a response that you can hear. To get a good low experience below 20 hz it is just a matter of lots of money and power smile.gif))) Here is the graph listed there also. Wow 580 or so posts and counting.
post #584 of 585
Bringing back an old thread here. BTW, those speclab graphs show that there was lots of low stuff still missing from TIH from the digital graph so imagine that 12 out 14 people knew it played lower now add in the rest of the low end and at much higher levels to get the full digital accurate playback and you guys would not think twice about which is better wink.gif
post #585 of 585
Quote:
Originally Posted by MKtheater View Post

Bringing back an old thread here. BTW, those speclab graphs show that there was lots of low stuff still missing from TIH from the digital graph so imagine that 12 out 14 people knew it played lower now add in the rest of the low end and at much higher levels to get the full digital accurate playback and you guys would not think twice about which is better wink.gif

LL

Top graph is Ironhead's cap of the SMs. His scroll speed isn't properly synced with his resolution and I can't tell what's up with the waveform (amplitude graph on the right), but the FR is still reflected in the graph.

Middle graph is Beast's 8x18" system mic'd

Bottom graph is the signal fed into SL from the SW out jack.

Beast's system has a signal chain that rolls off fairly aggressively below 10 Hz but he still captures the essence of the Hulk scene quite well. He's perfect to around 12 Hz, -5dB @ 10 Hz and -6-8dB from there to 6 Hz, the heart of the scene's ULF hit.

Pretty awesome.

The Ironhead cap shows the bump in response between 20-23 Hz and the dip @ 35 Hz but rolls off <20 Hz and gives not much <10 Hz with the 6 Hz hit pretty much missing from the reproduction. The listener's appear to have been reacting to the area around 10-20 Hz that's missing from the presentation with the HPF.

Mark has argued against my stance that the limiters change the FR at high level playback, but my position is unchanged. I believe the difference between the posted FR (averaged) and the response evident in the SL cap is a bit of sig chain but mostly limiters kicking in.

At my GTG later this summer I hope to show this limiter-induced FR change more accurately.

I agree with you, James. Accurate to 5 Hz in this scene at reference level is unmistakable and the whole difference in the presentation. After playing it a gozillion times it still unnerves me a bit. If the listeners ever get the chance to truly A/B these sorts of scenes, I'm sure the result will be as my similar tests have always resulted.
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