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vpr testing in small room
Old 9th June 2019
  #1
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vpr testing in small room

hello i'm nixon i tried building 2 vpr panels and here was my process. the steel is cold rolled 1m x 1.5m x 1.6mm & powder coated. i'm using a 4" mattress topper for the foam

i used master seal np1 polyurethane sealant spread thin.

in my room the bass is very amplified in the back of the room in the corner and back wall, super loud, and pretty quiet near my listening position. the room is completely untreated other than these 2 vprs i have just built. it's 9' x 10.7' x 8' with the wall behind the speakers brick & concrete floor, everything else drywall.

my rew testing seems odd, i think i've done something incorrectly. i've got the mic pointing upwards @ my ear's location with the 90deg cal file per instructions in the manual for measuring LF (both monitors). i'm using the umik-1. my waterfalls seem to indicate that the vpr's are making my response worse which would be sad
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vpr testing in small room-img_0508.jpg   vpr testing in small room-img_6902.jpg  
Attached Files
File Type: mdat vpr tests.mdat (9.93 MB, 20 views)
Old 9th June 2019
  #2
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The "2vpr corner" is the best when it comes to reducing the 104 Hz mode. You need more midrange absorption though. To fill out the interferences, do thick absorption on the side walls first.

Your desk reflection is also absolutely huge. Try some Basotect pads -- or a smaller desk.

Overall, from the impulse response, I think the room is stll under-damped.
Old 9th June 2019
  #3
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Did you change measurement volumes between empty room and VPR? Or are they adding 20+db of ringing?

Using a different glue and a mattress topper is probably sub optimal, but I still see some improvement.
Old 9th June 2019
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no changes in volume, and mic was in exact same spot also. i think something went wrong, how could the decay times be so small in a completely untreated squarish room between 0-100hz.

where do you see improvement? all i see is increasing decay times each time more treatment is added
Old 9th June 2019
  #5
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They're not that small (your window is set out to 2,000 ms). For positive changes: from "Empty" to "1 vpr corner" I noticed some work in the 140 buildup.

To get better measurements: Have signal peak around 85 DB (you don't really want to mix louder than this anyway) and do just single speakers (L and R independently, not together).
Old 9th June 2019
  #6
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Ok let me try these adjustments

Do you know if Measuring each monitor independently would it be advisable to point the mic directly at the monitor with the 0deg cal file
Old 9th June 2019
  #7
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Quote:
Originally Posted by datal4b View Post
Ok let me try these adjustments

Do you know if Measuring each monitor independently would it be advisable to point the mic directly at the monitor with the 0deg cal file
That introduces inconsistencies that don't help for this purpose.

You want to measure from a central point of both speakers without moving the mic, so point it to the ceiling and use the 90, make sure it's centered between the two speakers and then you'll have a meaningful comparison
Old 9th June 2019
  #8
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i see, ok let me try again with this method
Old 9th June 2019
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progress

ok, these measurements are looking much more correct, thanks for helping me. i decided to just do both panels at once. from what i can see they are doing something for the decay time, not as much LF work as i was hoping, but it's at least doing something positive i think? i included L+R measurements just for kicks

i'm noticing a little bit of improvement in LF at my listening position, but not much.
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vpr testing in small room-setup.jpg   vpr testing in small room-vprsetup.jpg   vpr testing in small room-lempty.jpg   vpr testing in small room-rempty.jpg   vpr testing in small room-l-rempty.jpg  

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vpr testing in small room-l-roverlay.jpg  
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File Type: mdat vpr tests2.mdat (14.89 MB, 5 views)
Old 10th June 2019
  #10
nms
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Quote:
Originally Posted by datal4b View Post
i'm noticing a little bit of improvement in LF at my listening position, but not much.
You're in a room with zero broadband acoustic treatment. This shouldn't be a surprise

Try building some thick broadband bass traps now and compare those results with your VPRs.

What made you decide to start with VPRs? That's an unusual starting point to choose.
Old 10th June 2019
  #11
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yea most certainly understand that.. i do want to continue treating the room, i can get Knaupf material here in my town 3lb or 6lb density

i started with the vpr’s because i had the foam already and from the research i did it seemed that the sub-100hz range was going to be a big problem for me so i figured i was definitely going to need some pressure based devices for my small room to help mitigate that

i’m wondering if their performance is going to change once there is other treatment in the room

i shall test and continue reporting
Old 10th June 2019
  #12
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Quote:
Originally Posted by datal4b View Post
i shall test and continue reporting
If you can build these VPRs for cheap, do one for every room corner.
Old 10th June 2019
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Quote:
Originally Posted by johannburkard View Post
If you can build these VPRs for cheap, do one for every room corner.
would be ideal, they ran me about 250 just for the plates so proper absorbent would’ve put them much higher unfortunately... i know that they aren’t cheap to make

i’ve been reading about the superchunks i can make a 4’ tall one for about 50 bucks so 4 corners floor to ceiling 400$ not bad.. does anyone know whether it’s better to use 3lb or 6lb density material for these? reading conflicting opinions
Old 11th June 2019
  #14
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Originally Posted by datal4b View Post
would be ideal, they ran me about 250 just for the plates so proper absorbent would’ve put them much higher unfortunately... i know that they aren’t cheap to make
A room full of VPRs is not ideal at all, regardless of price. They're a specific solution effective on a narrow band of frequencies.
Quote:
i’ve been reading about the superchunks i can make a 4’ tall one for about 50 bucks so 4 corners floor to ceiling 400$ not bad.. does anyone know whether it’s better to use 3lb or 6lb density material for these? reading conflicting opinions
6lb density is a very ineffective choice for bass traps. I wouldn't suggest using it in instances of more than 2" thickness. The thicker the trap, the lower density and GFR insulation type you should use.
Old 11th June 2019
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it might be nice to have one in each corner, flat to the boundary, coupled with fiber traps? that’s got to be better than fiber alone, i would think


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Originally Posted by nms View Post
6lb density is a very ineffective choice for bass traps.
thx!
Old 1 week ago
  #16
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what's up People so i've got some porous absorbers going now in my room, all the corners are chunked behind me now as well. I'm putting a cloud up next is the rest of the treatment I have so far. The awful boxy sound is now gone in the room, music sounds pretty nice and clean, detailed? Noticing alot of difference in mixdown between certain pieces of music vs. others of the same style i hadn't noticed before. Only thing is....still a huge hole in LF at my listening position. Guess that problem is going to be a bit harder to solve. I noticed the foam on my VPRs don't really sit all the way flush against the wall because they are just leaning right now with no frame so I am going to try to frame them so they sit perfectly flat against the wall, hoping that might help a little with the "short circuit" deal. Anyways... rew testing coming after cloud goes up.
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Old 1 week ago
  #17
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anyone have any luck with stereo sub setup in a small room?
Old 1 week ago
  #18
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Do you not have any ceiling treatment? If so, the ceiling and the front wall to ceiling intersection are two high priority treatment locations. As is the wall behind you.

Quote:
Originally Posted by datal4b View Post
anyone have any luck with stereo sub setup in a small room?
Wouldn't recommend it. Also would be better to buy one $1000 sub than two $500 subs if you actually want something cleaner & tighter.
Old 1 week ago
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i have 3 more of the 4" thick 2x4 panels to go up on the ceiling which i am spacing 4" away from the surface. i will get the wall ceiling intersection chunked also as you recommend. on the back wall I've got the VPR panel only which i'm not fully sure is doing anything... should I couple it something else maybe?

if i'm not getting any noticeable improvement after treating those two areas would you recommend more treatment in other areas of the room or is there a point of diminishing returns in continued adding of treatment

thanks for helping me
Old 1 week ago
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as far as the sub/LF issue goes, i'm just trying to hear some bass at the listening position without it ruining the rest of the spectrum if that's possible
Old 1 week ago
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Your monitors are big (for a very small room) & 'corner loaded' with regard to the room & your position in it. The SBIR is gonna be messy. Consider using them as vertical MTM.

I can't see a need for a sub in that size room with those monitors unless you intend to use the sub to influence the null in your mix position, perhaps by filtering bass from the mains.

Bear in mind the nulls & peaks shown on an FFT waterfall look a lot more dramatic than what your ears perceive, for multiple reasons. So don't expect perfect waterfalls. Reduced ringing is an acceptable result, in other words.

Sometimes modest changes to positions can provoke big changes in the measurements i.e. using velocity & pressure absorption is the right approach, but your speakers, toe-in angle, desk and listening position all factor into it and should be regarded as variables which can be adjusted.

Consider using a less acoustically intrusive desk, such as a mesh grill instead of glass. It wont change the bass ringing, but it will reduce comb filtering in the mids. Remember, the mids are where the music/magic happens, so it's really important to look after your mids.

VPRs work better when properly suspended and hung right against the wall surface, because that's where the highest pressure occurs.

Bass radiates from the speakers in all directions, so consider velocity absorption above and below the speakers, a bit like soffit mounting (but not as drastic)

Finally, consider using "room EQ" as a valid partial solution for your dilemma. MiniDSP offer Dirac for very modest expenditure and the pros for Dirac can easily outweigh the cons in your situation. "Here be dragons" applies, but that also applies to any room treatment once you enlist REW and make decisions based on test results.

Hope that helps.
Old 1 week ago
  #22
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Quote:
Originally Posted by diggo View Post
Your monitors are big (for a very small room) & 'corner loaded' with regard to the room & your position in it. The SBIR is gonna be messy. Consider using them as vertical MTM.
He'd need new stands, but also those speakers are not suitable for vertical orientation due to the orientation of the mid & tweeter. The physical orientation of the drivers is a bit unfortunate for this small room, given that the woofers & ports end up straddling the corner. The corner traps should also have been designed with a 60 degree angle instead of 90, so that the speakers could be set at the correct angle for an equilateral triangle without creating space behind the inside corner (and utilizing 90 degree XLR connectors to keep them flush as possible).

Quote:
Consider using a less acoustically intrusive desk, such as a mesh grill instead of glass.
I would DEFINITELY aim for a narrower desk. Small rooms require strategic planning and a desk proportioned to the room. Ideally should be as small as you can go while still accommodating your essential gear.

Quote:
Finally, consider using "room EQ" as a valid partial solution for your dilemma.
You don't want to head down this route til you've tackled the critical treatment locations in the room to properly deal with its problems. Can't leave the ceiling, front wall to ceiling edge, and rear wall untreated then expect it to sound right. Once you've treated all the key areas of the room properly, a little light room correction can be applied if needed, but it really should be the last item on the list.

Quote:
Originally Posted by datal4b View Post
if i'm not getting any noticeable improvement after treating those two areas would you recommend more treatment in other areas of the room or is there a point of diminishing returns in continued adding of treatment
If you're not getting noticeable improvement from a good ceiling cloud and corner chunks across the fw-ceiling edge then definitely book in for a hearing exam

Really though, these are critical locations and you can't get away with anything in a small room like this with concrete boundaries.

Go thick as possible for your treatments and cover as much surface area as you can. The room is small. That's the best course of action. And hopefully you didn't use anything above 3pcf density in those corner traps.
Old 1 week ago
  #23
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Quote:
Originally Posted by nms View Post
If you're not getting noticeable improvement from a good ceiling cloud and corner chunks across the fw-ceiling edge then definitely book in for a hearing exam
i'm really hoping it will improve the bass!

i produce drum & bass so the bass is central to the style but to be honest, it's all about the mid range definition as far as the "bass" goes, as one of you said. i can still hear some sub in tracks, it's just a bit behind the rest of the mix which doesn't sound that bad actually, i can really hear every detail of the track so that's probably owed to the quality of the s3h's and the treatment installed so far also of course... it's all good honestly. i'm trying to remind myself not to get too overwhelmed with getting this room dialed completely because 1. never gonna happen likely 2. my budget is running slim already had no idea how much this would add up to! and most importantly i noticed that many many of my favorite producers i notice have either no acoustic treatment at all or i have seen some of them with a couple pieces of foam on the walls so i guess it's all about making what you have work for you...in this style at least from what i can observe. that or they're final mixing in a pro environment. but i doubt the latter...it's all about technique for them at a certain point i think, so i know that it can be done even in the worse case scenario which gives me hope.

i will report back soon with some REW testing i'm going to modify the VPRs today and install the cloud.

thanks again for your input
Old 1 week ago
  #24
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Quote:
Originally Posted by diggo View Post
Consider using a less acoustically intrusive desk, such as a mesh grill instead of glass.
i know it's got to go...for sure

Quote:
Originally Posted by diggo View Post
Sometimes modest changes to positions can provoke big changes in the measurements i.e. using velocity & pressure absorption is the right approach, but your speakers, toe-in angle, desk and listening position all factor into it and should be regarded as variables which can be adjusted.
any ideas on how i might use this to my advantage?
Old 1 week ago
  #25
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so i put up the cloud and just moved my seat back to about 60% from the back wall and there is plenty of sub there. any way this could be bad for mixing?
Old 1 week ago
  #26
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Quote:
Originally Posted by datal4b View Post
any ideas on how i might use this to my advantage?
Once you've completed building the solutions suggested by nms, move & measure, one 'part' at a time - this will show you the influence positions can have on the test results. It will also show you that changes in test results which seem dramatic (in one way or another) are not always audibly dramatic.
You do need to maintain stereo symmetry of course, but sometimes asymmetric tests can provide insight.

But before you do that, use REW to generate tones at the modal frequencies shown on your waterfalls, then (for each tone you generate) very slowly walk around the space noting the huge nulls and huge peaks at different frequencies in different locations. If you've not done it before, this can be a disturbing but very useful experience, particularly if all the walls are solid like yours.

Your tests are likely to always show a strong dips from SBIR, but bear in mind our ears adjust for this much better than for detecting pitch amid ringing bass (hence the "one note bass" problem). That's partly because SBIR effects change when we move our head, but bass ringing doesnt.

Your optimal listening position should reside somewhere near (ideally a bit above above) the mid point (zero crossing) of the dominant standing wave which provokes the worst ringing after treatment.

Low budget situations like these, in small solid-walled rooms, need low frequency ringing to be the prime focus, followed by positioning of sources and listening spot.

Note your ceiling/roof cavity can potentially be used as a bass trap if that's an option.

Your speakers are unsuitable for your room and your chosen genre of audio (ie you want clean, accurate bass) - even with the corner treatment you'd added, that probably wont sufficiently reduce the comb filtered SBIR as a result of the uneven corner loading for the two mid/low speakers in each speaker box. Those speakers ideally need more space to each side and should not be corner loaded in the manner you've adopted out of physical necessity.

In other words, it's not ideal to build a solution around speakers which don't suit the room. That's partly why manufacturers are investing so much in designing professional speakers suitable for bedrooms (the other reasons being lower manufacturing and shipping costs).

I'd seriously consider swapping out your speakers for a demo of more suitable designs which incorporate assistance for your situation. Try demoing a pair of the tiny iLoud Micro monitors from IK Multimedia - they probably wont become your chosen speakers, but they will illustrate the big difference when using speakers designed for bedroom-sized studios.

https://www.soundonsound.com/reviews...ia-iloud-micro

The MTM version of the iLoud range looks likely to be a giant killer.

Using smaller main speakers allows you to make effective use of a mono sub for frequency perception/balance below 70Hz, which can be positioned at the ideal location in the room without impacting the stereo soundstage. The sub brings you positioning advantages which a two speaker system cant use - asymmetrical positioning and phase changing.

Whereas rolling off the bass from your existing speakers and adding a sub doesn't ameliorate the impact on frequencies above 100Hz due to the proximity of the corners.

You can use REW tone generator (as you move the sub) to confirm optimal location for a sub within the modal spectrum.

In other words, if one of your main criteria is potent, evenly distributed bass, consider the advantages of a 3 way system over a 2 way system. That said, in your shoes I'd probably swap out the mains as described above if adding a sub.

As nms said, tools like Dirac should only be used to apply final tweaks to an already physically tuned system. You already have a MiniDSP mic - have a look at their products which offer Dirac. MiniDSP makes excellent products.

Last edited by diggo; 1 week ago at 06:59 AM.. Reason: emphasis & grammar
Old 1 week ago
  #27
nms
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Quote:
Originally Posted by diggo View Post
Note your ceiling/roof cavity can potentially be used as a bass trap if that's an option.
Given the circumstances, it would be a great idea to go BIG on the deep ceiling treatment to help compensate.

Quote:
Your speakers are unsuitable for your room and your chosen genre of audio (ie you want clean, accurate bass) - even with the corner treatment you'd added, that probably wont sufficiently reduce the comb filtered SBIR as a result of the uneven corner loading for the two mid/low speakers in each speaker box.
Actually the issue here isn't uneven corner loading at all. It's that the two woofers are pretty evenly straddling the corner, which will excite the room modes more, and their width will cause the inside edge to be pulled forward from the treatment in order to get them at a 60 degree angle. Not ideal. The best solution in this room would have been to build a soft-flush mounted wall, which gets the speakers close to the wall and provides maximum absorption coverage & depth.
Old 1 week ago
  #28
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Quote:
Originally Posted by nms View Post
Given the circumstances, it would be a great idea to go BIG on the deep ceiling treatment to help compensate.
yep. Even to the extent of creating a false transparent ceiling for the entire room, filled with low density absorption.
Quote:
Originally Posted by nms View Post
Actually the issue here isn't uneven corner loading at all. It's that the two woofers are pretty evenly straddling the corner, which will excite the room modes more, and their width will cause the inside edge to be pulled forward from the treatment in order to get them at a 60 degree angle. Not ideal. The best solution in this room would have been to build a soft-flush mounted wall, which gets the speakers close to the wall and provides maximum absorption coverage & depth.
I agree with this with regard to the low frequency problems, which arent significantly affected by uneven corner loading aside from the overall contribution to low frequency excitement.

"Soft-soffit" could be interesting (to extend your suggestion a bit further)

That doesnt mean the speakers suit the space though. Horses for courses is best approach IMO. Room dictates solutions, in other words.
Old 1 week ago
  #29
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Originally Posted by datal4b View Post
2. my budget is running slim already had no idea how much this would add up to!
Welcome to Gearslutz!

Quote:
Originally Posted by datal4b View Post
and most importantly i noticed that many many of my favorite producers i notice have either no acoustic treatment at all or i have seen some of them with a couple pieces of foam on the walls
You don't want to be just average, do you?
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