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First build - Octo SI 18's with flat packs. - Page 11

post #301 of 623
3/19/13 at 1:50pm
MK: Your graphs drop like a rock below 6hz. That's odd behavior for your concrete bunker. Do you have graphs of signal chain rolloff via loopbacks?
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post #302 of 623
3/19/13 at 2:26pm
Quote:
Originally Posted by carp View Post

It shipped yesterday, so however long it takes to get here and then Kevin will do his thing but that will depend on how busy he is.

Hey, who shrunk my speakers?!?!






Ddduuuuuuuudddee! That looks so awesome! Even your dog is going nuts. tongue.gif
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post #303 of 623
3/19/13 at 2:29pm
WOW
That looks amazing!! Congrats
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post #304 of 623
3/19/13 at 2:43pm
Quote:
Originally Posted by popalock View Post

Seems like the SI's simply can't dig as deep as some of the other heavy hitters. Some of my favorite demo songs on my old LMS-U's just arent the same on the SI's. Not necessairly a bad thing...just means I'll have to find other favorite demo songs...lol

Ah. I was waiting for someone to point this out. You aren't the first person to say something just like this (but compared to another driver than the SI).

You know what this is atributed to? One really powerful motor coupled with the LMS technology on the coil.

Down low in a sealed subwoofer, you are guaranteed to be using a good amount of excursion if not all of it with peaks or overall loudness, most notably in the deeper bass <30-40hz. Some of you have seen pictures of the BL curve of a particular subwoofer driver. In most cases like the SI which is an overhung motor topology you will get a bell shaped curve that follows the excursion. The most amount of motor force (BL in general) will be around Xmax 0 or in a sitting position or within sitting position. As the excursion expands futher more and more of the coil is leaving the gap where the most flux in the motor is and the force from the motor/coil combination starts to drop. In some ways this can be an alright thing because that loss in force can possibly protect a driver from damaging itself by overexerting. Some might remember a year or so back and people were damaging their LMS-U's with too much power. The LMS-U has just as much motor strength at Xmax as it does just sitting.

Coming back from that I think this is why users that own LMS-U's and compare them to others say things like you did (where I quoted). There is plenty of power during the full stroke. Producing deep bass at any volume is forceful to put it one way. Using lesser drivers can somewhat compete with multiples but I think only within a margin of total output and that scales with how many drivers we are talking about.
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post #305 of 623
3/19/13 at 3:02pm
back in post #271, where were the subs located? dual stacks of four behind mains, or something else?

i though the frequency response of the red sweep looked almost perfect.

a little bit of shelf filter to boost the spl from 28hz to 18hz and it would be done.

here is the effect of a 12db/octave, 12db gain, shelf from 30hz to 15hz (more or less, blue dotted line).

a little eq at 45hz for that and the shaping is good.

since you run the bass a little hot, an 80hz cross would work just fine.



who knows if the stuff below 10hz is being measured properly anyways.

scott, great post. is there a public pic of the bl curve of the lms-u?
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post #306 of 623
3/19/13 at 3:05pm
^^^^^

Yup. cool.gif


Lol. Now this post looks like I am replying to your question about the LMS-U graph. biggrin.gif

But no...not that I know of.

Check below.
Edited by Scott Simonian - 3/19/13 at 4:03pm
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post #307 of 623
3/19/13 at 3:06pm
Quote:
Originally Posted by Scott Simonian View Post

Ah. I was waiting for someone to point this out. You aren't the first person to say something just like this (but compared to another driver than the SI).

You know what this is atributed to? One really powerful motor coupled with the LMS technology on the coil.

Down low in a sealed subwoofer, you are guaranteed to be using a good amount of excursion if not all of it with peaks or overall loudness, most notably in the deeper bass <30-40hz. Some of you have seen pictures of the BL curve of a particular subwoofer driver. In most cases like the SI which is an overhung motor topology you will get a bell shaped curve that follows the excursion. The most amount of motor force (BL in general) will be around Xmax 0 or in a sitting position or within sitting position. As the excursion expands futher more and more of the coil is leaving the gap where the most flux in the motor is and the force from the motor/coil combination starts to drop. In some ways this can be an alright thing because that loss in force can possibly protect a driver from damaging itself by overexerting. Some might remember a year or so back and people were damaging their LMS-U's with too much power. The LMS-U has just as much motor strength at Xmax as it does just sitting.

Coming back from that I think this is why users that own LMS-U's and compare them to others say things like you did (where I quoted). There is plenty of power during the full stroke. Producing deep bass at any volume is forceful to put it one way. Using lesser drivers can somewhat compete with multiples but I think only within a margin of total output and that scales with how many drivers we are talking about.

Outstanding explanation Scott. Thank you very much!
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post #308 of 623
3/19/13 at 3:18pm
"The LMS-U has just as much motor strength at Xmax as it does just sitting."

you sure about that?
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post #309 of 623
3/19/13 at 3:36pm
Quote:
Originally Posted by popalock View Post

Outstanding explanation Scott. Thank you very much!
+1

Thanks SS!
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post #310 of 623
3/19/13 at 3:41pm
Quote:
Originally Posted by LTD02 View Post

back in post #271, where were the subs located? dual stacks of four behind mains, or something else?

i though the frequency response of the red sweep looked almost perfect.

a little bit of shelf filter to boost the spl from 28hz to 18hz and it would be done.

here is the effect of a 12db/octave, 12db gain, shelf from 30hz to 15hz (more or less, blue dotted line).

a little eq at 45hz for that and the shaping is good.

since you run the bass a little hot, an 80hz cross would work just fine.



who knows if the stuff below 10hz is being measured properly anyways.

scott, great post. is there a public pic of the bl curve of the lms-u?

Scott helped me flatten out my response that was pretty similar by using the same method you're mentioning but when you say, a shelve filter from 30hz to 15hz", how is the 15hz part implemented into the dsp settings?

Back to OP. once you get the mini you'll be measuring in a whole different way. A tip that I didn't pick up on till after many hours is to actually use note pad plotting your concerning points from measurements/graph and then when you start applying filters and bumping/cutting different frequencies on the mini it will show how many dbs you've changed on the points that you've written down on the minis graph while you're changing things. It's a little time consuming and I'm not describing it as good as I would like but you'll see what I mean after applying a few changes you've made in the mini and remeasure a few times. Keeping track of how the EQ changes affect other frequencies that you're not necessarily trying to change is the key of the plots on note pad or whatever. I wrote down every 5hz what db was and target final point needed to be but some dips or peaks needed to be recorded as well.
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post #311 of 623
3/19/13 at 3:54pm
Quote:
Originally Posted by LTD02 View Post

"The LMS-U has just as much motor strength at Xmax as it does just sitting."

you sure about that?

Ummm..... yeeesss. I think I am correct. redface.gif


I wouldn't say it if I didn't think so. wink.gif
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post #312 of 623
3/19/13 at 3:56pm
Here we go!





I'm pretty sure that is not a sample from the LMS-U but of the LMT technology from a lab way back. I remember this exact picture but I do not remember what it was from. If we could get Kyle in here that would be great.

However, my explanation of motor force on perceived SQ is sound....no pun intended. tongue.gif
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post #313 of 623
3/19/13 at 5:08pm
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

back in post #271, where were the subs located? dual stacks of four behind mains, or something else?

i though the frequency response of the red sweep looked almost perfect.

a little bit of shelf filter to boost the spl from 28hz to 18hz and it would be done.

here is the effect of a 12db/octave, 12db gain, shelf from 30hz to 15hz (more or less, blue dotted line).

a little eq at 45hz for that and the shaping is good.

since you run the bass a little hot, an 80hz cross would work just fine.



who knows if the stuff below 10hz is being measured properly anyways.

scott, great post. is there a public pic of the bl curve of the lms-u?

LTD, yes that graph was all 8 subs up front 4 in each front corner.
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post #314 of 623
3/19/13 at 5:18pm
That looks sick. But I would constantly worry they were going to fall.
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post #315 of 623
3/19/13 at 5:43pm
"That looks sick. But I would constantly worry they were going to fall."

there is a rubber beaded-mat product used under area rugs to keep them from sliding around on wood floors that could be placed in between each box to keep them from sliding around.

now, with kids, i'd be nervous too. (but...hehe...you could always mount a safety loop/rigging to the back of the subs like some folks do with big screens to keep them from falling forward...or just hang them from the ceiling in a giant J-arrary for full effect.) j/k
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post #316 of 623
3/19/13 at 7:17pm
Funny things over the last few pages....

"YOLO"

"Thanks Fatshaft"

"I only have 3 18s and 2 12s"

"The LMS-U has just as much motor strength at Xmax as it does just sitting."
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post #317 of 623
3/19/13 at 7:33pm
Quote:
Originally Posted by nube View Post

MK: Your graphs drop like a rock below 6hz. That's odd behavior for your concrete bunker. Do you have graphs of signal chain rolloff via loopbacks?

Hey Nube,
Yeah that is the result of a bad sound card. My mic is calibrated flat to 4 hz but my sound card is cheap. I did run a loop back but maybe I need to run another file for it. I remember it took many tries to get one to register at all. My processor is flat to 5hz, my amp is flat to 2hz, and my PS3 is flat to ? I have no idea, I would assume(yikes) that it is flat to 5 hz? So that drop off has to be the sound card. It looks natural until 5.5hz and then it looks like a ported sub or something. Maybe it is time to upgrade the sound card. Any suggestions?
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post #318 of 623
3/19/13 at 7:48pm
Quote:
Originally Posted by Scott Simonian View Post

Here we go!





I'm pretty sure that is not a sample from the LMS-U but of the LMT technology from a lab way back. I remember this exact picture but I do not remember what it was from. If we could get Kyle in here that would be great.

However, my explanation of motor force on perceived SQ is sound....no pun intended. tongue.gif

Isn't that the graph from the old Adire (Parthenon) motor?
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post #319 of 623
3/20/13 at 1:55am
I think it's actually from the rare-ish Sound Splinter RLs driver. I don't think that is a curve from anything XBL^2 based.
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post #320 of 623
3/20/13 at 12:57pm
Quote:
Originally Posted by bossobass View Post

Hi FOH,

Yes, this is the theory that's been used as the explanation for why sealed subs have a rising response below their knee in-room vs GP.

Unfortunately, I have not been able to reconcile it with any posted in-room measurements. In the past few years, with OM and other low cost measurement hardware/software/freeware options, many more in-room graphs have been posted, many of which I've archived against the modeled and GP measured responses.

Hey Bosso,
This is certainly worthy of it's own thread, but I'd like to respond. I'm aware you feel this way from previous comments. It runs counter to what I've seen. I'm curious what you're basing your opinion on, as I've participated in such discussions with you before, and I believe we both shared similar positions wrt PVG.
Quote:
Originally Posted by bossobass View Post

Carp is seeing room gain begin where virtually everyone else does, regardless of the "longest dimension of the room"... in the 30s Hz. He's seeing an almost identical amount of gain as I (and notnyt, Josh, MKT, etc.) do, around 8dB/octave, beginning in the 30s Hz in rooms ranging from 2200 cubes to 6000 cubes, some open to the rest of the hose and some in an enclosed room.

The physics involved dictate the onset frequency, and the amount elicited by the room.

We have the room's physical boundaries, which determine the frequency of the 1, 0, 0 mode (the first axial length mode). This is essentially the last point at which sound bounces around, propagating as we typically associate it to do. It's at this point that the room behavior changes and begins to act more toward confining the pressure, rather than the propagation we're typically familar with.

Below this point is the static mode, where the acoustic behavior tends toward pressurization, not propagation.
Quote:
Originally Posted by bossobass View Post

I've stopped calling the phenomenon PVG and I don't believe subwoofers "pressurize" a room. Instead, they send pressure waves through the room.

This pressurization discussion has been made, I agree,.. in that a room doesn't become pressurized. They're inherently too lossy.

However, with the deep stuff, the compression is still occuring upon the point at which the leading edge of the compression encounters the farthest boundary. With either a single sub system, or a well executed (in-phase/coherent) multi-sub scenario, the sub system would increase the pressurization we experience. An audible sound could be defined as a pressure wave, within the frequency range, and at a high enough level to be discernable/experienced by us. So if the wavelengths are so long as to encounter the far boundary, before even finishing the initial outward, compression stroke, then yes there would be a corresponding raise in pressure, ... commensurate with the displacement of the drivers.


How else could the phenomenon we're discussing occur?


Quote:
Originally Posted by bossobass View Post

The gain is related to the phenomenon of progressively constructive reflections. Reflections can be constructive or destructive. As the wavelength increases, there is less chance of them being destructive and they become more and more constructive.


Outdoors, or in a very large space that would be the case, but not indoors.


For simplicity, we'll use a single sub example.

By definition, the static mode is just that. Due to the physical size of the space, and the frequency of the wavelength, the mass compresses and rarefacts in all in concert. There won't be constructive or destructive interactions.


Quote:
Originally Posted by bossobass View Post

If there was a frequency below which the room becomes everywhere pressurized, causing this PVG phenomenon, he would not be seeing 6dB differences within the so-called pressure vessel gain region simply by moving the subs, as he (and everyone else who has engaged in this exercise in his own room) clearly has shown is the case.


Although an interesting observation, I'm not sure what's causing what you're refferring to. edit; I've looked, I see nothing inexplicable in Carp's graphs

Quote:
Originally Posted by bossobass View Post

I have not been able to match the onset of the wavelength whose length is twice my rooms longest dimension to any measurement I've made with the subs in any location(s) in my room in 10 years. In fact, room gain begins in my room an octave above that theoretical PVG point.



I can appreciate that. Conversely, my findings wrt PVG onset in my room correlate spot on. I've noticed many that correlate quite closely, some not so much. If yours appears to begin an octave sooner, that's fine. That doesn't mean that where it begins,...by definition, it cannot. Other boundary reinforcement, certainly. Modal influences, as well. However, one cannot experience PVG above the first mode. Any acoustic gain at that point is efficiency elicited from 1/2 space, 1/4 space, etc., loading.


It's not unusual for us to view Carp's measurements, and boltster our previously held views.


Thanks


This is worthy of it's own thread, I find it very interesting, and I'd enjoy reading more of what you've discovered. Some of what I've learned may be wrong, if so, .. I'd like to know exactly what that is. The physics is solid, but admittedly, I've not read all the papers many here have poured through. So assume nothing, I want to know more.
Edited by FOH - 3/20/13 at 9:47pm
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post #321 of 623
3/20/13 at 1:13pm
"Scott helped me flatten out my response that was pretty similar by using the same method you're mentioning but when you say, a shelve filter from 30hz to 15hz", how is the 15hz part implemented into the dsp settings?"

it depends on how your dsp defines a shelf filter. if using the behringer which has a 20hz limit, then using negative gain on a high pass filter will produce the same thing.

"I wouldn't say it if I didn't think so."

it is just a pretty wild claim, so i was just confirming that what i thought you were saying is what you were saying. the picture appears to have linear bl, but is that the lms-u or something else? pretty interesting.
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post #322 of 623
3/20/13 at 1:26pm
it looks like that image is from this file:

http://www.angelfire.com/ultra2/london/WhitePaper.html
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post #323 of 623
3/20/13 at 3:03pm
Thread Starter 
FOH, Bosso, LTD and anyone else if you want to start another thread on the subject I understand but I love the fact that you are having the discussion here. The reason I am posting so much info, graphs, pictures, etc. is so I'll have a record of it but the most important part is the advice and input from others - and with that interesting discussions which are currently above my head but someday I may get more of a handle on. I don't often look back at old threads, but this one I will for sure so I appreciate all of your input and opinions even if a lot of it isn't directed at me. smile.gif

That is selfish on my part though, and I do understand a separate thread would be more viewer friendly for others to follow along that may not see your back and forth buried in my thread.

BTW, I'm all setup to experiment with the minidsp, mrsmithers was kind enough to let me borrow his until mine gets here. cool.gif
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post #324 of 623
3/20/13 at 4:48pm
Quote:
Originally Posted by LTD02 View Post

"Scott helped me flatten out my response that was pretty similar by using the same method you're mentioning but when you say, a shelve filter from 30hz to 15hz", how is the 15hz part implemented into the dsp settings?"

it depends on how your dsp defines a shelf filter. if using the behringer which has a 20hz limit, then using negative gain on a high pass filter will produce the same thing.

"I wouldn't say it if I didn't think so."

it is just a pretty wild claim, so i was just confirming that what i thought you were saying is what you were saying. the picture appears to have linear bl, but is that the lms-u or something else? pretty interesting.

Quote:
Originally Posted by LTD02 View Post

it looks like that image is from this file:

http://www.angelfire.com/ultra2/london/WhitePaper.html

You know? I am just regurgitating what I remember from the past when the LMT tech started to surface when TC was battling it out with XBL^2 tech a few years back. I don't think the graph I posted is of the Ultra and I stated that but everything I learned of this technology is that the BL is linear from a near sitting position all the way out to the edge. I wouldn't take what I said literally but close. wink.gif If that. I'm still learning new things everyday and sometimes I'm wrong. smile.gif
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post #325 of 623
3/20/13 at 4:56pm
Quote:
Originally Posted by popalock View Post

Kevin, do you have a build thread or a writeup some where regarding your miniDSP Box build? I'm probably one the few idiots who wasted money on purchasing a boxed version, but I'd love to see what I could pickup from your write up.l

I didn't make a thread or take any pictures. I can when I put carp's together. Basically I just put it in a 1U rackmount case so that it can go in a rack (someday when I have one!) and have the connectors on the back side be the only thing visible. I had no interest in paying extra for their "boxed" solution that still doesn't do a bit of good since you still have to use those Phoenix terminal to XLR connectors (or similar) and then are left with this form factor that isn't really conducive to anything. Just personal preference really, but I like having it all enclosed and neat-like.
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post #326 of 623
3/20/13 at 5:15pm
Thilo Stompler says their subwoofers have a flat BL.

http://www.youtube.com/watch?v=r1RIMfzCxXM (starts at about 2 minutes in)
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post #327 of 623
3/20/13 at 6:09pm
Quote:
Originally Posted by Scott Simonian View Post

You know? I am just regurgitating what I remember from the past when the LMT tech started to surface when TC was battling it out with XBL^2 tech a few years back. I don't think the graph I posted is of the Ultra and I stated that but everything I learned of this technology is that the BL is linear from a near sitting position all the way out to the edge. I wouldn't take what I said literally but close. wink.gif If that. I'm still learning new things everyday and sometimes I'm wrong. smile.gif

It's interesting stuff Scott. I'm glad you posted it. I was poking around on that site a bit and found this Dumax report, which looks to be the same or a very similar graphic of measured data. The driver description reads, "TC Sounds Variable Coil, 15" Subwoofer Honeycomb".

I didn't realize it was even possible to get BL vs. displacement to be so flat.
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post #328 of 623
3/21/13 at 9:24pm
Thread Starter 
Ok, did a lot of playing around with the minidsp tonight. What I have found is that I do not like flat bass, or at least so far I don't.

Here is what I managed to get with a bunch of tinkering with the minidsp:



Above is the flattest I could get it. I experimented with the LT thingy and ended up with 12.7 gain and I used 25hz for the f(0).

I had to pull down 30hz a ton.

Next I tried the same settings but 30 dbs louder on the receiver. Actually 29.5, I went as loud as the receiver would go without bumping up the individual speaker volumes so I guess I still had over 20 db left in the tank but I don't want to experience that. As is the sweep was very loud even with ear plugs in. I didn't get an average, just very quickly hit the pause on the omnimic and saved the curve from there.

So, looks like there isn't much or any compression at least at those volumes but... even though those are loud volumes for a sweep they aren't much for movie bass peaks.

Next, on to watching more bass heavy movie scenes. I kept creeping up the volume until I was at reference with the subs 10 hot trying to get the clip light to tickle a bit. The only scene it did that was the beach scene in the newest X-men movie and then later Bass I Love You.

So all is good right? Well, I noticed I wasn't really overwhelmed with the bass like I expected. So I stopped looking at lights and worrying about measurements and just watched scenes and listened to bass I love you. Meh... it's ok. The really low notes in Bass Love you are cool but I'm not getting that huge impact I like.

I clipped Bass I love You before I wanted more and that's a bit depressing since I just spend the better part of the last 2 weeks putting 8 friggin subs together...

Is this it? Is this really it? confused.gif



Ok, screw this. I go back into the settings and take of the eq at 30hz and some of the other smaller eq stuff I had done so the only thing left is the LT.

SOOOOOOO much better. Huge impact. I can feel the bass just crushing me, the front wall/screen is shaking like mad - or is it my eyeballs, not sure. So, I know I'm a heretic but to me flat bass sounds... flat.

Before I jump to conclusions that I don't like flat bass here is what I have come to believe. In the past I played around a ton with the sms-1 and was left with the same conclusion: pulling down peaks/mountains and then raising everything back up is just as bad as boosting. I feel it totally neuters the bass. In my next sub configuration with subs under each side surround speaker I know my response is going to be flatter but I have a feeling I'll like it - because I won't be pulling down massive peaks.

So here is the comparison. The blue line sounds/feels so crazy good and the red line is nice but underwhelming and doesn't do it for me.







Now, looking at that you might be thinking, well sure you have more bass with the blue line so of course that will seem better - but here's the thing. I ran both settings hot and loud until I got clip lights - well actually that's not true. I never clipped with the blue line!! That's the whole thing I've been after, I gave in before my amp/subs did!! With the red line setting I clipped before I cried uncle.

Ha, oh one other thing. Earlier today Kevin and I did discover that one of the 8 subs was out of phase. It was easy to spot during the x-men scene because the drivers were moving so slow in parts. That throws off all of my measurements from before - damn.

It didn't make a massive difference but it did smooth things out some.
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post #329 of 623
3/21/13 at 9:34pm


Dude... don't worry about what other people say. Set the bass how YOU like it. Obviously we can see that flat bass is possible in your room. You were unhappy with the results so go with the ones that do make you happy. smile.gif
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post #330 of 623
3/21/13 at 9:41pm
Quote:
Originally Posted by Scott Simonian View Post



Dude... don't worry about what other people say. Set the bass how YOU like it. Obviously we can see that flat bass is possible in your room. You were unhappy with the results so go with the ones that do make you happy. smile.gif
Well said Scott! And Carp, again, great post. There are far, FAR more knowledgeable peopl on here, but for me, my ears will almost always trump measurements.
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