8x 18" LMS 5400 Ultras Sealed to 27 Cube 15hz Ported Build - Page 16 - AVS Forum
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post #451 of 512 Old 04-24-2014, 03:33 PM
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Well here is the decay of my room from 2 weeks ago.
Mains + All Subs
with all acoustical panels deployed (not including the front wall treatments that haven't arrived yet);

Front wall: 1% treated (<8sqft)
Left wall: 55% treated @ 4inches, combo of Safe'NSound (~48sqft) + FBM Wedges(~16sqft)
Right wall: 55% treated @ 4inches, combo of Safe'NSound (~48sqft) + FBM Wedges(~16sqft)
Ceiling: 40% treated @ 4inches, combo of Safe'NSound (~108sqft) + FBM Wedges(~32sqft)
Back Wall: 5% treated @ 4inches, ~20sqft FBM Wedges
Floor: 216sqft padded carpet, 180sqft of vynl, on cement foundation
FL Corner: 8cuft FBM Bass Traps
FR Corner: 8cuft FBM Bass Traps
BL Corner: Nothing
BR Corner: Nothing

[Apparently my 60 to 80hz is running a bit HOT. hehe... biggrin.gif I will have to look into that]

(Note: Mic has self-noise hum @ 60hz.)


Above 150hz, the sweep has decayed to the mic's noise-floor after 1/5th of a second.


Room Modes affecting decay appear to be:
142.4hz
120.0hz
78.0hz
73.0hz
60.0hz (the third worst)
49.0hz
25-35hz (the second worst)
14.5hz (the worst)

Room Modes affecting nulls appear to be:
90hz
55hz

Software Calculated modes:
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post #452 of 512 Old 04-24-2014, 04:34 PM
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I don't have any "befores"... but I should be able to remove the corner pieces from the front wall easy enough and remeasure without. (Stand by).

Here is just my mains by themselves, to give a different perspective on the effect of the absorption on the bass decay.

This was the 110db sweep I did a week ago.

Well... I think I found the bass culprit. tongue.gif
Looks like it could be my new mains that is adding the extra upper-bass, the Quad UM's seem to be adding lots of 60 to 80hz.
I will look at EQ'ing them downwards slightly if that is the case.


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post #453 of 512 Old 04-24-2014, 05:24 PM
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Ok here we go.

Everything kept exactly the same.

Removed all of this (~17 cubic feet):




Red without, Blue With.

With Corner Bass Traps:







Without Corner Bass Traps:



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post #454 of 512 Old 04-24-2014, 05:28 PM - Thread Starter
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post #455 of 512 Old 04-24-2014, 05:32 PM
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No it's the mic's self-noise (Emotiva mic-1 or whatever they call it)
No ground loop.
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post #456 of 512 Old 04-24-2014, 06:41 PM
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Hey not'...

I'm thinking of getting into a couple Crawsons, and powering them with the inuke 1000 DSP. Since you have the same set up I'm sure you would know.......doesn't the inuke roll off at 20hz? Is there some work around or does it not matter?

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post #457 of 512 Old 04-24-2014, 06:56 PM - Thread Starter
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Quote:
Originally Posted by SeekingNirvana View Post

Hey not'...

I'm thinking of getting into a couple Crawsons, and powering them with the inuke 1000 DSP. Since you have the same set up I'm sure you would know.......doesn't the inuke roll off at 20hz? Is there some work around or does it not matter?

Not noticable. Do it.
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post #458 of 512 Old 04-24-2014, 10:49 PM
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Yea I think I will do it....I get a feeling the wife is going to get me a Oppo 103D for my birthday, i'm asking for it so I can run the Crawsons off of the sub out. I haven't even finished building my dual Ultra's....and I'm already looking for more.

Did you set the gain or volume (what ever it's called, since it doesn't actually make noise) of the Crawsons and just leave it, or does it vary with the MV?

When you say it's not noticeable, is it because the 20hz feeling is so intense? Can you feel 10.....5hz?

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post #459 of 512 Old 04-24-2014, 11:05 PM - Thread Starter
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Quote:
Originally Posted by SeekingNirvana View Post

Yea I think I will do it....I get a feeling the wife is going to get me a Oppo 103D for my birthday, i'm asking for it so I can run the Crawsons off of the sub out. I haven't even finished building my dual Ultra's....and I'm already looking for more.

Did you set the gain or volume (what ever it's called, since it doesn't actually make noise) of the Crawsons and just leave it, or does it vary with the MV?

When you say it's not noticeable, is it because the 20hz feeling is so intense? Can you feel 10.....5hz?

You can feel all the way down to dc, it's pretty intense. If there's rolloff, I don't notice. I'm also EQ'd slightly with the dynamic EQ so there's more action at lower levels without it getting too crazy as the mv raises.
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post #460 of 512 Old 04-25-2014, 12:40 AM
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Rob, was there any difference in crossover when you ported the subs other than the subsonic cross?  What is the cross freq/slope?

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post #461 of 512 Old 04-25-2014, 02:40 PM - Thread Starter
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Quote:
Originally Posted by SpinMonster View Post

Rob, was there any difference in crossover when you ported the subs other than the subsonic cross?  What is the cross freq/slope?

I cross at 80hz in multichannel mode (movies) and 90hz in 2 channel mode (music). No change. Whatever slope my receiver users...
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post #462 of 512 Old 04-25-2014, 09:43 PM
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standard slopes for receivers are 2nd order highpass (meant to be put on top of sealed speakers with natural 2nd order rolloff) for the mains and 4th order lowpass for the subs. so the net effect is 4th order acoustic crossover. reality though varies...quite a bit!

Listen. It's All Good.
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post #463 of 512 Old 04-25-2014, 10:10 PM
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So when you say 2nd order that is 12db right? 12db per octave....and a octave is half the frequency?

So.....where ever it starts to roll off let's say 30hz.....then by the time it has dropped to 15hz it's down 12db?

1st order is 6 db per octave
2nd order is 12db
3rd order is 18
So on and so on multiples of 6?

What is the highest order? 6th=36db...

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post #464 of 512 Old 04-25-2014, 11:37 PM
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Quote:
Originally Posted by LTD02 View Post

standard slopes for receivers are 2nd order highpass (meant to be put on top of sealed speakers with natural 2nd order rolloff) for the mains and 4th order lowpass for the subs. so the net effect is 4th order acoustic crossover. reality though varies...quite a bit!

 

I agree but he has theater mains with big bass and is not likely rolling off at 80hz.  He could likely use 4th order electrical at 80 or 90. As it stands I doubt there is much missing in his system but the better power handing with more filtering from the mains may make for more detail in the mid-bass. JBL lists his 4722 mains as being +/- 3db down to 30hz. I'm sitting here thinking that many enthusiasts would consider his 4722's as being great quality deep bass.....haha

 

http://www.jblpro.com/www/products/cinema-market/screenarray-systems-2-way/4722_4722n#.U1tULvldWa8

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post #465 of 512 Old 04-26-2014, 03:24 AM - Thread Starter
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post #466 of 512 Old 04-26-2014, 04:40 AM
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post #467 of 512 Old 04-26-2014, 07:47 AM
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I find that doing effective room correction and trapping is notoriously difficult especially without baffle walls all around the room or unless decor is a non-concern

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post #468 of 512 Old 04-26-2014, 10:43 AM
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Quote:
Originally Posted by SeekingNirvana View Post

So when you say 2nd order that is 12db right? 12db per octave....and a octave is half the frequency?

So.....where ever it starts to roll off let's say 30hz.....then by the time it has dropped to 15hz it's down 12db?

1st order is 6 db per octave
2nd order is 12db
3rd order is 18
So on and so on multiples of 6?

What is the highest order? 6th=36db...

Thanks for clearing that up for me smile.gif

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post #469 of 512 Old 04-26-2014, 12:32 PM
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Quote:
Originally Posted by SeekingNirvana View Post

Hey not'...

I'm thinking of getting into a couple Crawsons, and powering them with the inuke 1000 DSP. Since you have the same set up I'm sure you would know.......doesn't the inuke roll off at 20hz? Is there some work around or does it not matter?

I'm using the 3000dsp which I think is a better match, Randall at Crowson told me that they can take up to 500 watts and are an 8 ohm load and the 3000 puts out just under 500 watts per channel in 8 ohm stereo. I've clipped the inuke many times with no harm done to the Crowson.
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post #470 of 512 Old 04-26-2014, 01:59 PM - Thread Starter
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I'm using the 3000dsp which I think is a better match, Randall at Crowson told me that they can take up to 500 watts and are an 8 ohm load and the 3000 puts out just under 500 watts per channel in 8 ohm stereo. I've clipped the inuke many times with no harm done to the Crowson.

I'm running them at 4 ohms bridged off the nu1000dsp, which translates to 500 per transducer. I run them hard. I've overheated them before testing, but haven't seen any real issues in movies.
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post #471 of 512 Old 04-26-2014, 02:28 PM
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Quote:
Originally Posted by notnyt View Post

I'm running them at 4 ohms bridged off the nu1000dsp, which translates to 500 per transducer. I run them hard. I've overheated them before testing, but haven't seen any real issues in movies.


Duh...didn't think of that...

That would have saved me having to run another set of speaker wires (my amps are in the room next to me) when I get my 2nd Crowson...oh well.
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post #472 of 512 Old 04-26-2014, 03:13 PM
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Quote:
Originally Posted by notnyt View Post

jbl lists -3db at 40hz.

I stand corrected but the point was that they weren't rolling off 2nd order at 80 or 90hz.

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post #473 of 512 Old 05-06-2014, 01:16 PM
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forgive me for asking as i'm not a builder like you...but did you put any filler in those cabinets? or is it just dead air with the port slots and bracing?
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post #474 of 512 Old 05-06-2014, 02:32 PM
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notnyt's cabinets don't have any kind of dampening material inside of them.
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post #475 of 512 Old 05-07-2014, 04:14 PM
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notnyt's cabinets don't have any kind of dampening material inside of them.

Does that ruin the sound or affect it for better or worse?

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post #476 of 512 Old 05-08-2014, 03:38 AM - Thread Starter
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Does that ruin the sound or affect it for better or worse?

It doesn't make a difference. Stuffing the box would lower tuning and overall output, I didn't want that.
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post #477 of 512 Old 05-08-2014, 08:08 AM
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so is it better to NOT use any fill at all when building a sub? I thought it would sound hollow without it. am i wrong?
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post #478 of 512 Old 05-08-2014, 08:11 AM
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http://www.data-bass.com/data?page=content&id=79

"In general, there is probably a sweet spot for most systems where the system's major response issues are cleaned up and damped, but further addition of material will only serve to further decrease efficiency. Unfortunately, finding this sweet spot probably involves trial and error or other testing."
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post #479 of 512 Old 05-08-2014, 08:12 AM
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To sum it up, if your cabinets don't seem to have resonance issues, you probably don't need it.
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post #480 of 512 Old 05-08-2014, 08:16 AM
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Quote:
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so is it better to NOT use any fill at all when building a sub? I thought it would sound hollow without it. am i wrong?

Rules of thumb applied universally will usually result in a result below what you were expecting. However, notnyt understands the rules and thus he knows when to deviate from the rule of thumb.

I must be guilty because people say I am guilty because they chose to call me guilty because they refuse to see the truth. Much easier to be part of the mob..
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