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post #1 of 42 Old 12-09-2016, 01:54 PM - Thread Starter
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HELP! Huge Room Null

I recently finished my theater (https://www.avsforum.com/forum/19-ded...ent-build.html). I'm still in the process of dialing everything in but I have a serious room null that's driving me crazy. I've spent close to 10 hours moving subs and measuring and I just can't seem to get a handle on it. I've also spent multiple hours on the forums and have read through the Harmon white paper on sub placement. No matter what, I seem to have a 2-3 foot null for basically 80hz and below that spans the entire length of the room right down the middle (impacting both front and rear center seats).

My room is 18' x 12.5" with low ceilings (80"). The room fairly air tight and was built with DD+GG. I've got a media cabinet and equipment rack in the rear two corners (floor to ceiling drywall) connected by an 8" x 8" soffit. All of the empty areas were stuffed with insulation. Currently the subs sit on a sand/insulation filled stage (6" tall). I've also got a 4'10" x 7'6" x 16" riser which doubles as a bass trap (filled with insulation and lots of 3" holes). The front corners have floor to ceiling "super chunks" which span 24" across and fill the entire corner. The room also has 6 - 2'x4'x2" acoustic panels. My current setup includes two Def Tech ProSub 1000's connected to a Yamaha A2050 AVR.

Here's a couple shots of the room:





I also put together a quick drawing with dimensions and locations I've tried so far. The wavy lines in the middle represent the null.



I've not done a detailed analysis, so far I've just been testing using 31, 40, 50, 63, and 80hz test tones. However, I can say the difference is dramatic across all of those bands. In most cases, especially 50 and lower, I'm seeing a 15-25db difference in the left and right seats vs. the middle. The left and right seats for both rows remain within 2-3db in the majority of placements.

Current setup is in position 1 which is basically me giving up for the moment. Corner loading them makes no difference in the null, moving them from the side walls a bit seems to provide a little smoother response outside the null so that's where I've landed for now. I've also tried basically every position possible across the stage (including placing them higher, pointing them in every direction possible, etc.). Basically no placement in the front seems to make much of a difference for null or otherwise. Position 8 (front and rear center placement) provided the best results in terms of leveling out the null. However, this position is less than ideal as my second row is against the back wall and it still didn't eliminate the null. The "crawl" method with single sub in front center chair yielded the most db in position 7. While it did increase the db in the null, there was still a huge difference seat to seat (not to mention the left and right seats were too boomy). Position 9 (opposite corners) also helped with the null but created much larger dips and peaks between seats. Oddly enough, the null is actually reduced when I unplug one sub, normally a 3-6db increase at the null. However, this may be normal due to some sound waves cancelling each other out. I perform more detailed measurements if it would help (i.e. write down db's for each seat with different placements). I haven't done that as of now because I don't need to see the numbers to tell how big of a difference there is. Essentially, you can stand 2 feet left or right of center and bass is overwhelming, step to center and you can't even tell they are on.

Anyways, hoping some of you experts may have some additional thoughts. I'm looking at upgrading my speakers/subs but don't want to invest in bigger & better subs with this nasty null. I'd also like to avoid adding two more subs due to space (not to mention my wife would likely kill me and I'm not convinced it would help). Moving the seating also makes no difference as the null is the same from front wall to back wall. I've also played around with moving the couch just to see if it impacts anything, it does not. I'm at a loss...

Thanks!!
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post #2 of 42 Old 12-09-2016, 02:37 PM
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I can't help but nice setup!

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post #3 of 42 Old 12-09-2016, 02:46 PM
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You say 80Hz. If I were a betting man, I'd say you're looking at your Width Null. (12.5 feet is about 90 Hz). Did you try putting a sub to each side of the seats? So one just to the left and one just to the right? That would be the first "test". I'd do this more to check the cause than a fix (unless it works for you!)

Edit: totally missed paragraph after pics, will get back.
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post #4 of 42 Old 12-09-2016, 02:56 PM
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Okay, chewing over some more, two things (not an expert, but if nothing else gathering info for those who are).

Did you play with phase settings at all? Are you running YPAO? (Yamaha's room correction software for those who don't know). In part of your measuring were you re-running ypao for each new sub position?

My new suggestion after having seen you moved subs is can you put an air gap behind the wall panels? I'd see if you could get them out at least 2" from the wall and listen (even if temporarily, because then knowing that helped you could look at soffit traps or something).
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post #5 of 42 Old 12-09-2016, 03:10 PM
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What are you using to time-align the subs and did you time-align them after each move?

Have you tried the REW room simulator? REW is a free download and the room sim should work pretty well for your room.

Room EQ Wizard
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post #6 of 42 Old 12-09-2016, 03:40 PM
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Sounds more like a phase issue and drop some panels or get some diffusion going , does the room sound dead.

And post equipment list and DRC system if used.
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post #7 of 42 Old 12-09-2016, 07:40 PM
 
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The subs are set symmetrically. That's usually the worst way to place them. They should be asymmetrically placed. I see that your numbered placements were all symmetrical. That's why you kept getting a bad result, and why one sub works better than two. Instead of 1/1, for instance, try 1 left, 5 right. With a room that narrow you may even find center clustered works better than split.
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post #8 of 42 Old 12-09-2016, 08:48 PM
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That back couch can be converted in a nice enclosure for a couple of more drivers and smoother response.
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post #9 of 42 Old 12-09-2016, 09:01 PM
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1 and 5 like bill said, but if your null is at 90hz, you may want to play with phase on your subs.
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post #10 of 42 Old 12-09-2016, 09:17 PM
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Put both subs stacked on top of each other, facing the corner. (3 inches is enough space.)
That is usually the best place for a sub when no other placement options are possible.

Having the subwoofer directly behind the head-rest, at ear level, is one of the most-ideal locations for resolving room-null issues.
i.e. Nearfield
Unfortunately... it is also the least-practical.
One sub behind each seat on the floor is the next-best compromise.

Alternatively the four, 1/4 wall points, is another highly-optimal location. Also again highly-impractical though...

What works for treble, doesn't work for bass.
What works for bass, doesn't work for treble.
Funny how that is, but it has to do with the size of the waves and how insensitive our ears are at low frequencies, and how it interacts with the room and its abilities to penetrate walls and diffract around extreme-angled corners.

Usually below 20hz the wave is so big it doesn't matter where or how many subs you have, they sum perfectly. Rarely is there a room null in the infrasonic range.

On the other hand, the mid-bass octaves above 60hz are highly-sensitive to placement/room-nulls. In a rock concert, you are usually outside or in a really big space, so the SPL is merely a matter of adding more subs, stacked all the way to the clouds. In a smaller space, like a house, the room and sub-placement becomes critical.

It's hard to say where will be the optimal location without a supercomputer and a Ph.D
Usually it is easier to just measure some real-world sweeps, than trying to sim it in virtual reality.

Wel it comes to bass, cube shaped rooms, sphere shaped rooms and L-Shaped rooms tend to be the WORST shapes.

Rectangular tends to be the best shape, but only if the subs aren't really far away, as distance reduces loudness. 75% reduction for each doubling of increased distance.

So you lose 75% output in the first 6 feet... (unless you are sitting in a room-peak, like the corner of the room! Where the bass is again... most-optimal [but again... not good for movie-watching or treble either!])

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post #11 of 42 Old 12-10-2016, 05:13 AM - Thread Starter
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Quote:
Originally Posted by mushroommunk View Post
Okay, chewing over some more, two things (not an expert, but if nothing else gathering info for those who are).

Did you play with phase settings at all? Are you running YPAO? (Yamaha's room correction software for those who don't know). In part of your measuring were you re-running ypao for each new sub position?

My new suggestion after having seen you moved subs is can you put an air gap behind the wall panels? I'd see if you could get them out at least 2" from the wall and listen (even if temporarily, because then knowing that helped you could look at soffit traps or something).
I did run YPAO for most positions. However, I haven't messed with the phase settings. The receiver has normal and reverse for each sub, I will play around with them to see what kind of impact it has. I should be able to put an air gap between my panels but it wouldn't be easy. Is the idea the air gap would provide better low end absorption? Outside the null, the room is fairly flat, the only standing waves I've noticed are in front of the equipment rack and media cabinet.
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post #12 of 42 Old 12-10-2016, 05:18 AM - Thread Starter
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Quote:
Originally Posted by Alan P View Post
What are you using to time-align the subs and did you time-align them after each move?

Have you tried the REW room simulator? REW is a free download and the room sim should work pretty well for your room.

Room EQ Wizard
I'm using YPAO, measuring from each of my six seating locations. I actually just ordered a calibrated mic for my phone to use with AudioTool but now I'm thinking REW will provide more detailed results. I'm going to look around for a decent USB mic.
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post #13 of 42 Old 12-10-2016, 05:29 AM
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Quote:
Originally Posted by earleyksig View Post
I recently finished my theater (https://www.avsforum.com/forum/19-ded...ent-build.html). I'm still in the process of dialing everything in but I have a serious room null that's driving me crazy. I've spent close to 10 hours moving subs and measuring and I just can't seem to get a handle on it. I've also spent multiple hours on the forums and have read through the Harmon white paper on sub placement. No matter what, I seem to have a 2-3 foot null for basically 80hz and below that spans the entire length of the room right down the middle (impacting both front and rear center seats).

My room is 18' x 12.5" with low ceilings (80"). The room fairly air tight and was built with DD+GG. I've got a media cabinet and equipment rack in the rear two corners (floor to ceiling drywall) connected by an 8" x 8" soffit. All of the empty areas were stuffed with insulation. Currently the subs sit on a sand/insulation filled stage (6" tall). I've also got a 4'10" x 7'6" x 16" riser which doubles as a bass trap (filled with insulation and lots of 3" holes). The front corners have floor to ceiling "super chunks" which span 24" across and fill the entire corner. The room also has 6 - 2'x4'x2" acoustic panels. My current setup includes two Def Tech ProSub 1000's connected to a Yamaha A2050 AVR.

Here's a couple shots of the room:





I also put together a quick drawing with dimensions and locations I've tried so far. The wavy lines in the middle represent the null.



I've not done a detailed analysis, so far I've just been testing using 31, 40, 50, 63, and 80hz test tones. However, I can say the difference is dramatic across all of those bands. In most cases, especially 50 and lower, I'm seeing a 15-25db difference in the left and right seats vs. the middle. The left and right seats for both rows remain within 2-3db in the majority of placements.

Current setup is in position 1 which is basically me giving up for the moment. Corner loading them makes no difference in the null, moving them from the side walls a bit seems to provide a little smoother response outside the null so that's where I've landed for now. I've also tried basically every position possible across the stage (including placing them higher, pointing them in every direction possible, etc.). Basically no placement in the front seems to make much of a difference for null or otherwise. Position 8 (front and rear center placement) provided the best results in terms of leveling out the null. However, this position is less than ideal as my second row is against the back wall and it still didn't eliminate the null. The "crawl" method with single sub in front center chair yielded the most db in position 7. While it did increase the db in the null, there was still a huge difference seat to seat (not to mention the left and right seats were too boomy). Position 9 (opposite corners) also helped with the null but created much larger dips and peaks between seats. Oddly enough, the null is actually reduced when I unplug one sub, normally a 3-6db increase at the null. However, this may be normal due to some sound waves cancelling each other out. I perform more detailed measurements if it would help (i.e. write down db's for each seat with different placements). I haven't done that as of now because I don't need to see the numbers to tell how big of a difference there is. Essentially, you can stand 2 feet left or right of center and bass is overwhelming, step to center and you can't even tell they are on.

Anyways, hoping some of you experts may have some additional thoughts. I'm looking at upgrading my speakers/subs but don't want to invest in bigger & better subs with this nasty null. I'd also like to avoid adding two more subs due to space (not to mention my wife would likely kill me and I'm not convinced it would help). Moving the seating also makes no difference as the null is the same from front wall to back wall. I've also played around with moving the couch just to see if it impacts anything, it does not. I'm at a loss...

Thanks!!
Hi earleyksig,
I myself had terrible trouble locating my subs, for the best position in my room. I wish I had good knowledge of correcting bass nulls, etc. As "Alan P" recommended, I would try REW as you can get a real look at what your room and speakers, subwoofers are doing, and how they perform together. I wish I had more Computer skills to set it up for myself.
I have a big null in my room in the 50 - 100hz range. I never seemed to master doing sub crawls. I could see what my subwoofers were doing via Paradigm PBK though. I use 2 x Paradigm DSP-3100, and 1 x Paradigm DSP-3400.
Using your Position no. 7 (at the rear of the room), is it possible to raise your Subwoofers off the floor on stands, or something temporary that is sturdy to see if this makes a difference to your Bass Null. I placed my 3 subs on 27 inch high Stands. This has worked for my room, the bass is pretty flat down to 25hz. This performance is good for the DSP-3400 in my room. You may not have the space or need to raise them that high in your room,but if it is possible you could give it a try?
Regards, Juz
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Last edited by Juz; 12-10-2016 at 05:31 AM. Reason: Grammar
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post #14 of 42 Old 12-10-2016, 05:43 AM - Thread Starter
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Quote:
Originally Posted by audiofan1 View Post
Sounds more like a phase issue and drop some panels or get some diffusion going , does the room sound dead.

And post equipment list and DRC system if used.
Interesting thought on dropping panels. I used the calculator on ATS Acoustics' site and I'm actually around a panel short based on their recommendations. Would dropping panels help in the <100 hz range? I didn't think the 2" panels made an impact in that range. In terms of equipment, I'm running my Prosub 1000's directly from my A2050. At this point, I've only been relying on YPAO and a db meter for measuring. I have Adaptive DRC (i.e. YPAO volume) set to off.
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Quote:
Originally Posted by Bill Fitzmaurice View Post
The subs are set symmetrically. That's usually the worst way to place them. They should be asymmetrically placed. I see that your numbered placements were all symmetrical. That's why you kept getting a bad result, and why one sub works better than two. Instead of 1/1, for instance, try 1 left, 5 right. With a room that narrow you may even find center clustered works better than split.
I did do opposing corners which did help some but it also caused quite a bit if unevenness in the left and right seating positions. However, that may be something that could be dealt with by EQing. I'm going to try 1 and 5, run YPAO, and adjust the phase settings. I'm hoping to give it a try later today, I'll jot down some measurements and post the results as well.
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post #16 of 42 Old 12-10-2016, 05:55 AM - Thread Starter
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Originally Posted by donktard View Post
That back couch can be converted in a nice enclosure for a couple of more drivers and smoother response.
I like where your head is at! It is fairly hollow underneath, think you may be on to something!
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post #17 of 42 Old 12-10-2016, 05:59 AM
 
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1 and 5 like bill said,
That was just an example, 5 and 7 may work better, or 2 and 3. What's pretty much guaranteed, and proven by the OPs experience, is that symmetrical placement doesn't work. In the absence of measuring tools I'd locate the first sub based on the crawl, then place the second wherever it works best.
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post #18 of 42 Old 12-10-2016, 06:02 AM - Thread Starter
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Originally Posted by Bill Fitzmaurice View Post
That was just an example, 5 and 7 may work better, or 2 and 3. What's pretty much guaranteed, and proven by the OPs experience, is that symmetrical placement doesn't work. In the absence of measuring tools I'd locate the first sub based on the crawl, then place the second wherever it works best.
Thanks Bill! It seems like most of the information I read leaned more towards symmetrical placement but it does make sense as to why it wouldn't work in a lot of rooms.
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post #19 of 42 Old 12-10-2016, 06:06 AM
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Pay attention to Bill. Best looking (symmetrical) is often worst-sounding. Symmetrical placement means the subs are driving the same nodes instead of "breaking them up".

You could also download AndyC56's multisub optimizer program -- see thread in this forum.

https://www.avsforum.com/forum/113-su...optimizer.html
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post #20 of 42 Old 12-10-2016, 06:08 AM
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Quote:
Originally Posted by earleyksig View Post
I'm using YPAO, measuring from each of my six seating locations. I actually just ordered a calibrated mic for my phone to use with AudioTool but now I'm thinking REW will provide more detailed results. I'm going to look around for a decent USB mic.
I never used YPAO, but if it is like other room correction software, your spacing for microphone placement is way too wide (for example for Audyssey each measurement location shouldn't be more then 2 feet away from central location). You need better way to optimizer subs I suppose. And ofc...more subs would smooth out response further if you have means...especially with multiple rows in your theater.

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post #21 of 42 Old 12-10-2016, 06:12 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
Put both subs stacked on top of each other, facing the corner. (3 inches is enough space.)
That is usually the best place for a sub when no other placement options are possible.

Having the subwoofer directly behind the head-rest, at ear level, is one of the most-ideal locations for resolving room-null issues.
i.e. Nearfield
Unfortunately... it is also the least-practical.
One sub behind each seat on the floor is the next-best compromise.

Alternatively the four, 1/4 wall points, is another highly-optimal location. Also again highly-impractical though...

What works for treble, doesn't work for bass.
What works for bass, doesn't work for treble.
Funny how that is, but it has to do with the size of the waves and how insensitive our ears are at low frequencies, and how it interacts with the room and its abilities to penetrate walls and diffract around extreme-angled corners.

Usually below 20hz the wave is so big it doesn't matter where or how many subs you have, they sum perfectly. Rarely is there a room null in the infrasonic range.

On the other hand, the mid-bass octaves above 60hz are highly-sensitive to placement/room-nulls. In a rock concert, you are usually outside or in a really big space, so the SPL is merely a matter of adding more subs, stacked all the way to the clouds. In a smaller space, like a house, the room and sub-placement becomes critical.

It's hard to say where will be the optimal location without a supercomputer and a Ph.D
Usually it is easier to just measure some real-world sweeps, than trying to sim it in virtual reality.

Wel it comes to bass, cube shaped rooms, sphere shaped rooms and L-Shaped rooms tend to be the WORST shapes.

Rectangular tends to be the best shape, but only if the subs aren't really far away, as distance reduces loudness. 75% reduction for each doubling of increased distance.

So you lose 75% output in the first 6 feet... (unless you are sitting in a room-peak, like the corner of the room! Where the bass is again... most-optimal [but again... not good for movie-watching or treble either!])
I hadn't thought about stacking, I will definitely give it a try. One thought though, wouldn't this defeat the purpose of having two subs? I did try placing them directly behind the front left and right seats and the null was still present. It has to be be an issue with the room width as it doesn't seem to make much of a difference at all as to where I move the subs lengthwise (null always in middle of room). This is my first build but I did take room size/dimensions into account based on some initial research. My love for sound really started back in my car audio days which was a walk in the park compared to home audio. The only concern I had with my W7 in a custom vented enclosure was permanent hearing loss
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post #22 of 42 Old 12-10-2016, 06:16 AM - Thread Starter
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I appreciate all of the feedback so far! You've given me a lot more things to try. Hoping to give a few of them a try later today. I'll run through multiple frequencies and record the results.
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post #23 of 42 Old 12-10-2016, 07:35 AM
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To add to the very competent advice you have gotten, I would probably not spend much time on a stacking option. Based on what you have said, you will be upgrading subs once you find a way to deal with the nulls you are experiencing. So, you need to engage in a problem-solving process that will enable you to ultimately move to better multiple subs. I said multiple, rather than dual subs, because if you can make something work in the rear riser, that might be very helpful for reasons that transcend just the current frequency response issue.

Bill's advice is always very helpful. Where I see symmetrical sub locations routinely recommended is for 4 subs--as in subs in each of the 4 corners (Toole) or 4 subs at 1/2 or 1/4 wall length (Harman/Welti). For fewer than 4 subs, most experts recommend asymmetrical arrangements involving opposing walls, such as Geddes triangular configuration for three subs. Two subs, symmetrically located on the front soundstage, is popular aesthetically, and it does work for some people. But, symmetrical arrangements for dual subs is never a default recommendation, according to anything I have read.

Putting air pockets behind acoustic panels--particularly open back acoustic panels--can enable them to be effective down to 60Hz, or even a little lower. But, it takes space to do that. The good news is that the panels might be able to work anywhere, including in the rear ceiling alcove or the riser, so that might be something else to try. In addition to getting REW to test things, I might investigate whether I could do more with treatments, and whether a third sub might help.

Regards,
Mike

GUIDE TO SUBWOOFER CALIBRATION AND BASS PREFERENCES

* The Guide linked above is a comprehensive guide to Audio & HT systems, including:
Speaker placements & Room treatments; HT calibration & Room EQ; Room gain; Bass
Preferences; Subwoofer Buyer's Guide: Sealed/ported; ID subs; Subwoofer placement.

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post #24 of 42 Old 12-10-2016, 09:21 AM - Thread Starter
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Started doing some tinkering and I honestly can't believe what I'm seeing. As a baseline, I left the subs where they are, ran YPAO using a single measurement point (center directly between first and second rows). My settings are all speakers set to small and crossed over at 80hz with the exception of my Atmos modules which are crossed at 200. Parametric EQ set to flat, YPAO volume and DRC off. When performing the tests, I had all speakers off except for the subs. I took measurements with AVR set at 0, running test tones from my phone in 10 hz increments from 30-100 (measured 20 but it was ~35 db - main reason I want bigger subs). Phone was hooked directly into AVR and volume turned all the way up. Intitial results are what I expected, a 20+ db swing in 40-50 range from center to left or right seats. Before I started moving subs, I set one to reverse and left the other in normal. I immediately noticed a huge difference. Here are the results:



I cannot believe how big of a difference it made. It has almost completely eliminated the null across all bands <100. The biggest difference now is 70-80hz but it's down to 5-6db vs. 20+. However, while frequency is much flatter across a given row, the second row is now substantially louder than the front. I'm thinking this will be much easier issue to address though.

Back to the phase setting, are there any implications to having the subs out of phase of one another? I haven't done any real listening yet as I wanted to get these results posted. Based on what I'm seeing though, it seems to be the trick at this point.

I've got to run an errand but am hoping to get back to it shortly. I still want to try a couple of different locations now that the phase has made such a difference in my initial null.
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Originally Posted by earleyksig View Post
Started doing some tinkering and I honestly can't believe what I'm seeing. As a baseline, I left the subs where they are, ran YPAO using a single measurement point (center directly between first and second rows). My settings are all speakers set to small and crossed over at 80hz with the exception of my Atmos modules which are crossed at 200. Parametric EQ set to flat, YPAO volume and DRC off. When performing the tests, I had all speakers off except for the subs. I took measurements with AVR set at 0, running test tones from my phone in 10 hz increments from 30-100 (measured 20 but it was ~35 db - main reason I want bigger subs). Phone was hooked directly into AVR and volume turned all the way up. Intitial results are what I expected, a 20+ db swing in 40-50 range from center to left or right seats. Before I started moving subs, I set one to reverse and left the other in normal. I immediately noticed a huge difference. Here are the results:



I cannot believe how big of a difference it made. It has almost completely eliminated the null across all bands <100. The biggest difference now is 70-80hz but it's down to 5-6db vs. 20+. However, while frequency is much flatter across a given row, the second row is now substantially louder than the front. I'm thinking this will be much easier issue to address though.

Back to the phase setting, are there any implications to having the subs out of phase of one another? I haven't done any real listening yet as I wanted to get these results posted. Based on what I'm seeing though, it seems to be the trick at this point.

I've got to run an errand but am hoping to get back to it shortly. I still want to try a couple of different locations now that the phase has made such a difference in my initial null.
Ignore the 1 &5 on the second row, I was going to take that measurement next but did position 1 (reverse/normal) for all seats instead.
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Polarity is a double edged sword. If you've got a null caused by the outputs of the subs combining destructively over a narrow band width and/or LP reversing the polarity on one sub can eliminate the null within that pass band and/or LP, but it may also create a new null in a different pass band and/or LP. By and large if polarity is an issue it will show up as more of a broad band cancellation than a narrow pass band cancellation.
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Interesting thought on dropping panels. I used the calculator on ATS Acoustics' site and I'm actually around a panel short based on their recommendations. Would dropping panels help in the <100 hz range? I didn't think the 2" panels made an impact in that range. In terms of equipment, I'm running my Prosub 1000's directly from my A2050. At this point, I've only been relying on YPAO and a db meter for measuring. I have Adaptive DRC (i.e. YPAO volume) set to off.
I'm using a few ATS panels as well You could try dropping only the second reflection point panels and leaving the first reflection panels up (try combo panels there or diffusion only panels it can really easy to over damp a room)Also as Bill mentioned playing with the phase can indeed be a two edge sword, try moving one sub to the opposite corner in the rear of the room and play with the phase just to see if you can fine tune things further, also try different crossover points as well while 80hz is the defacto standard 90hz or 100hz maybe a better setting for overall blending to the sub. The more important question is how does it sound now after the recent tweaking you've done?
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I've done some additional tinkering/measuring. I tried several variations in the front, 1/5, and 1/7. 1/7 with one set to normal and the other in reverse, it seems to have given me a flatter response between rows. However, my low end took a nosedive but may correctable with some EQing. Here are the new results:



I feel like I'm getting closer. The first time in 1/7, I ran YPAO with two positions, front center and rear center. With this, response was all over the place seat to seat. I then set it up in a single centralized position and those are the results you are seeing above. What's the consensus on YPAO measurements? Single central location or is it better to measure at all seating positions?
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post #29 of 42 Old 12-11-2016, 06:33 AM
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Originally Posted by earleyksig View Post
I've done some additional tinkering/measuring. I tried several variations in the front, 1/5, and 1/7. 1/7 with one set to normal and the other in reverse, it seems to have given me a flatter response between rows. However, my low end took a nosedive but may correctable with some EQing. Here are the new results:



I feel like I'm getting closer. The first time in 1/7, I ran YPAO with two positions, front center and rear center. With this, response was all over the place seat to seat. I then set it up in a single centralized position and those are the results you are seeing above. What's the consensus on YPAO measurements? Single central location or is it better to measure at all seating positions?
As you may know, there are two schools of thought on this. One thought is to measure across a very large area, hoping to EQ the entire listening space better that way. The other is to restrict measurements to a smaller area, hoping to give the EQ algorithm slightly more consistent data to work with. Audyssey, which used to recommend spacing mic positions 3' to 4' apart, has recently changed its recommendation to spacing mic positions no more than 2' apart. That is consistent with the second school of thought, and with the experience of many Audyssey users.

I can't think of any reason why the fundamental issues would be that different with YPAO. If I were you, I would probably start with a somewhat limited mic spacing, concentrated around the primary listening position. If you don't like the results, or if you are simply curious, you can always try measuring from every seat. But, I really believe that the latter asks a little too much of the weighting algorithm.

In any case, there will almost certainly be imaging differences anyway among seats, as some seats on the perimeter are closer to some speakers than others. Concentrating your EQ resources on the seats which are most often used (and which have superior imaging) probably makes the most sense for general use of the HT.

Regards,
Mike

GUIDE TO SUBWOOFER CALIBRATION AND BASS PREFERENCES

* The Guide linked above is a comprehensive guide to Audio & HT systems, including:
Speaker placements & Room treatments; HT calibration & Room EQ; Room gain; Bass
Preferences; Subwoofer Buyer's Guide: Sealed/ported; ID subs; Subwoofer placement.
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post #30 of 42 Old 12-11-2016, 11:03 AM
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Polarity of Mains. Same as Subs

I'm not an expert but I had a similar problem with a null. My null/suck out was really noticeable when the subs, two of them, were working with the mains. Very obvious listening to music. Using REW with a calibrated microphone from CS labs, 90° polar coordinates, and testing near field, I confirmed that my null was not due to either sub. It had to be the room and/or interaction with my mains which are Vienna Acoustic Baby Beethoven Grands and the CC.

Using a 1.5 volt battery, I discovered my mains, BBG, sucked in on positive polarity while all other speakers pushed out, even my CC speaker which is also a Vienna Acoustics Maestro, pushed out on positive polarity. Yikes!

This bothered me as Audyssey MultEQ XT32 (pre is AV 8801) did not detect until after I moved the speakers to extreme positions. I didn't even bother trying to determine the REW readings as to me, all speakers should be the same polarity - period.

So I reversed the polarity on my mains and noticed an immediate improvement. Problem solved.

Since then I moved and system now in completely different room. The room is 17' x 31' with 10' ceiling. Bass was a bit lacking and I acquired some new nulls and peaks.

I have spent too much time moving, subs, reading REW graphs, etc., REW (awesome tool) is time blind IMO and I don't want to pursue a feedback loop.

I decided to just replace 13" subs with 16" subs. Even without an Audyssey calibration the difference was extremely noticeable - much deeper and smoother bass. Bottom line - more woffage fixed my lacking bass in new room. I'm so satisfied with it, I'm not even going to measure it for a while and just enjoy. I've had the subs for a few days only; however, I am convinced that sub driver size has just as much affect as, placement and room environment.

I hope this helps and gives you some other options to consider. Also, you don't need a 9v battery to do the polarity test, I used a D size 1.5 v.
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