# First attempt at room treatments



## DanTheMan (Oct 12, 2009)

OK, so I've started the journey into improving my room. First thing I built is an 8ft by 2ft bass trap with R19 paper face out:
material specs from http://www.bobgolds.com/AbsorptionCoefficients.htm
PRODUCT	THICKNESS	MOUNTING	125HZ	250HZ	500HZ	1000HZ	2000HZ	4000HZ	
Paper Out	6.25" R19	on wall.........0.94...1.33....1.02....0.71.....0.56......0.39
looks like a good bass absorber.

































Now for some before and after graphs:
*before in five places across the couch*








*after in five paces across the couch*








Certainly did not do much. Here's 2 graphs from the same miv position. Nothing at all was changed setting wise in these spectrograms.
















Here's those 2 FR overlaid. The blue is after treatment:








RT60 for the same 2 graphs. Blue is still after treatment:









Any thoughts?

Thanks gents,

Dan


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## Moonfly (Aug 1, 2008)

Bass traps are not my area of expertise, but I cant see what it has done if anything, and I can read graphs etc. It looks as though you have a massive peak in your low end bass response though, and thats something electronic EQ can certainly help with. Have you done anything to tackle it before looking into bas traps.


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## bpape (Sep 14, 2006)

How many did you build and deploy and how big is the room? 

Looks to me like it did quite a bit for the 90Hz dip and dropped your decay time about .04.

Just remember that corners themselves will not solve all frequency response issues. Most peaks and nulls will be due to SBIR, cancellations off the back wall, and height modes in standard sized rooms. Some are also based on seating position in relations to room dimensions.

Are your sure you're measuring decay times right? .35 at 40 Hz is pretty hard to do without a LOT of treatment depending on the room.

Bryan


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## Moonfly (Aug 1, 2008)

How do the 5 positions relate to the seating position. In the 5 measurement graphs it looks like there has been some reduction in the dip at 90hz, but the single position before and after on the single graph shows little effect.


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## DanTheMan (Oct 12, 2009)

I've experimented a fair amount with placement, filter frequency, phase and level settings to try and kill that 30Hz issue. It always seems to result in a more readily audible issue. The only electronic EQ I've tried was an absolute bummer. I gained a 60Hz hum in the one channel no matter how I cabled it and I never bothered to try another.

I only built one and placed it in the corner nearest the entertainment center. Here's a photo of it now combined with the three 2'X4' foam absorbers I just built placed on the wall behind the entertainment center. I changed the color to match the foam:
















Sorry about the barrel distortion on the lens. It's an old point and shoot camera. Oh, and the flash seems to reflect more off the bass trap more than the foam. The color os closer in person.

The previous graphs did not include the treatments and placement of the subs was different. The room is "S" shaped with a laundry room connected, a long hallway, a large dormer, vaulted ceilings and I've never measured it out with any precision. 

As far as measuring goes, I'm just letting REW do all that. I just measured from five positions across the couch where we listen/watch movies. On the right side I do toward the arm of the couch, then toward the inside of the right cushion, one in the middle, one toward the inside of the left cushion and then toward the left arm. Only the graph where I did the side-by-side are the mic positions exactly the same. The others are startlingly similar however even if they are off by an inch.

After some placement, phase, filter setting and level setting and new treatment placements, I've got this:
















and the average from across the five positions:









Here's an old RT60 from the old room prior to the additional foam treatments and different sub placement(s) and moving the bass trap around the room--purple line is with the bass trap furthest into the room. The monitors are in the identical position.









So it looks like the foam does do something. I'm in the process of building 3 more. Any suggestions for placement? I was thinking one between the bass trap and the curtain and then 2 on the other wall near the hallway. Later I was thinking diffusion behind the couch even though its about 5 feet from the rear wall. Does this sound like a smart idea? I've got to do a lot more bass trapping I think. Any suggestions on those would be greatly appreciated.

thanks,

Dan


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## DanTheMan (Oct 12, 2009)

I wanted to show a little before and after room treatments/placement changes.
Before:








After:








Before:








After:








Before:








After:








Not a complete winner, but generally improved. The bass decays somewhat slower in some positions, but sounds better overall.

Dan


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## Moonfly (Aug 1, 2008)

Could you post the last graph with 1/3rd smoothing applied, I would be interested to see that. It does look like your addition are having an impact now and offering decent results, which is pretty good considering no eq is being applied :T As they say, get the room right first and the rest will follow.


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## bpape (Sep 14, 2006)

1/3 octave smoothing will mask a lot of problems. It's interesting to see as our ears can try to filter some anomalies but to really fix things, we need unsmoothed data.

Exactly right. If you do the setup correctly and apply appropriate treatment in the right places, you can do a lot - and it will help in terms of decay time for every seat in the house as opposed to EQ.

Bryan


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## Moonfly (Aug 1, 2008)

I would simply like to see the smoothed response, as like you say it masks some of the finer details (that your ears cant really distinguish anyway) and gives a more overall idea of how the response is. I lie to compare the smoothed and un-smoothed responses personally.


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## bpape (Sep 14, 2006)

Sorry. Thought I was agreeing with you that it was interesting to compare to see what our ears might try to do with it.

Bryan


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## Moonfly (Aug 1, 2008)

My bad :doh: :T


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## DanTheMan (Oct 12, 2009)

Here you go Moonfly:

















Dan


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## Moonfly (Aug 1, 2008)

Cheers Dan.

The smoothed response highlights what issues are more likely to be immediately obvious to your ears. It looks fairly decent but as you can see you still have a couple peaks centred on 30 and 80 hz. These will be the most prominent issues as far as your ears are concerned so I think the smoothed response is good as it visually shows you this, and allows you to somewhat ignore less important issues that might otherwise just be a distraction. 

The 80hz peak is likely due to some interaction with the speakers at the crossover point, so looking into that might solve that peak quite quickly and easily. The 30hz peak will need either more bass trap work, or som electronic eq to bring it down.

Personally, I like to use the smoothed result as my final judgement. At the end of the day, its nigh on impossible to get your response absolutely perfect, so at some point you have to give up with trying to perfect the un-smoothed response, and IMO, this is the first step to helping cure tinkeritus :bigsmile:.


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## DanTheMan (Oct 12, 2009)

Me tinker? Nah, never gonna happen.:whistling: OK, three more treatments built. Measurements tomorrow or sometime soon. I can tell you these make the largest audible difference, but my gut tells me the measurements won't look too different from the last--at least FR and RT60. Right now I'm just flabber-ghasted(sp?) by the imagine and soundstage improvements. Very, very cool.

Anyone have a method for hanging a 2ft by 4ft room treatment on a door?

Dan


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## DanTheMan (Oct 12, 2009)

OK, got longer cable, moved a sub, toed the monitors in differently, and tried again.

































Looks like I need more cable. Oh, and I took 6 measurements this time. That 40-50 Hz region is just a bummer. Should I build more bass traps? There's only a few more places they could easily go.

Dan


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## bpape (Sep 14, 2006)

Well, something is changing it looking at your plots. What's the difference between say the red plot and the gold plot?


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## DanTheMan (Oct 12, 2009)

About 3 ft. What used to be the worst seat for bass is now the best and the old best is now the worst. Oye.

I think I'm going to build as many bass traps as will fit easily into the room before I do any more graphing. Getting a decent bass response in a small room isn't so simple. Maybe if I had another sub (that would make 3) it would be easier. I'd like to do the Welti thing, but my room is far from rectangular, and the Geddes thing requires another sub. My bet is that a parametric EQ is in my future.

Dan


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## bpape (Sep 14, 2006)

3 feet in which direction? That will shed some light on potentially good positions to address. If one is farther forward, then it likely can be addressed with a combination of corner treatments and rear wall behind the seating.

Bryan


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## DanTheMan (Oct 12, 2009)

The gold is near the middle of the couch and the red is on the right side--three feet to the right. So neither of them are really more forward. The right side of the couch is near the kitchen/dining room which has no doorway in between them. The left side of the couch is about 5ft from a corner where my home computer desk is. I really want to get rid of it as I never use it. That left corner is where the bass is now smoothest, but the RT60 is longer there than anywhere else--look at the #1 and #2 lines.

Bryan, do you have a recommended style of bass trap? The rear wall really can't be done at present, but I've got 5 ft of space behind the couch to the rear wall. So the area immediately behind the couch can be treated. According to Dr. Toole's book, absorption should be placed 1/4 wavelength away from the wall of the intended frequency where maximal particle velocity occurs. To get down to 30Hz, that would require 9ft. My current situation should be able to get me to approx 50Hz. Vibrating bodies would then do better near the walls where maximal pressure occurs. How would you do it? I'm loosing my hair trying to get to the bottom of it.

Thanks,

Dan


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## bpape (Sep 14, 2006)

OK. So, you either have some tangentials and obliques piling up there at the center or it's picking up you as being at something like 1/4 of the distance from the one wall to the far wall in the other room.

Reread the Toole. 1/4 wavelength is theoretical optimum. Real practice shows that you can go significantly closer and thinner and be effective. According to theory, you also should have THICKNESS at 1/4 wavelength which is not practical. 

If the dip is not coming from the rear, then placing treatments there, regardless of type isn't going to address any frequency response issues - only decay time and ringing in that position. I'd experiment with something on the side wall to narrow down even farther.

Another test would be to measure say 1' in front or behind the existing center seat to further narrow things down.

Bryan


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## DanTheMan (Oct 12, 2009)

Thanks Brian! I went a little further than what you asked for just for safe measure.








































Recap with some smoothing applied:

































I would love to know how to best treat the room and place the subs. My earlier attempt sounded better than this current one overall. Oh, I know things work better than the theories in Dr. Toole's book, but that theory is nice to know and helps me rationalize what I do even when its wrong.:doh: I have a ton of r19 left over that I'd really like to use in building these new traps.

I'm not really concerned with the treble end at all. I am going to go back to my previous toe in just b/c I like it better. It also graphs better as well.

Dan:bigsmile:


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## DanTheMan (Oct 12, 2009)

OK, I built another bass trap but made this one a bit smaller. It's 4' by 2' by 16" but actually contains more fiberglass than the last.
Here's what I'm looking at now:
































Where the rt60 is high on the bass, it the right side opposite the bass trap. Now check out the center seat:

















Any thoughts gents?

Thanks,

Dan


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## DanTheMan (Oct 12, 2009)

Well, I turned the bass down, adjusted the toe in a bit, and did ten more measurements to see if I could get a more appropriate AVG.
















































Subjectively this is easily tops as far as I've owned. All with a $152 pair of main monitors slightly modified.

Dan


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## bpape (Sep 14, 2006)

That's the thing - you just never know how much of some of the problems you're having are due to monitor or xover or both. Even so, with no EQ and minimal treatment (I'm very sure the room could use more), you're within a total of 5db range. In most cases, if you can get to +/-5 UNSMOOTHED with no eq, you're doing fantastic.

You're basically there in the 10 position average other than being a couple db over around 140Hz.

Bryan


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## DanTheMan (Oct 12, 2009)

That 140Hz bump is the only thing that's readily audible as a defect. The odd thing is that it's never been a problem prior to building this bass trap. The trap seemed to smooth out other parts of the bass, but somehow created another issue. Overall though I am extremely happy with this result. My thought is that the 30Hz issue probably has to do with the long dimension of the room and the 140Hz might be d/t the ceiling b/c they seem to be there regardless of mic position across the couch. My guess is that they are perpendicular to the couch. Would that be your assessment Brian?

Thanks,

Dan


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## bpape (Sep 14, 2006)

Remove the trap that supposedly caused the problem and see if it goes away. If so, then use it somewhere else. There are times when 2 problems cancel each other out and when getting one right, the other shows up. 

Bryan


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## DanTheMan (Oct 12, 2009)

Sounds good, I'll do that later today.

Thanks,

Dan


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## DanTheMan (Oct 12, 2009)

OK, so I moved the second bass absorber down the hall. Here's the avg. of the before and after. The after is the top line:








Not really much difference really.:doh: So here's the rest of what I'm looking at:
Both traps in place:








After trap removed:








Both traps:








one trap removed:









So looking at those carefully it seems the extra absorber helps very little and actually makes the RT60 longer in one position in the low bass.

So a panel absorber is next, but how to build one is the question?

Dan


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## bpape (Sep 14, 2006)

Adding a bass absorber is not going to make the RT60 (which really isn't all that usable in small rooms anyway) longer. What it may do is allow something to come forward that was being cancelled before. If it's not helping frequency response, then likely, the corner wasn't the proper place to address those particular issues. Until you determine where the problems are physically, matters not what you put in the room.

Bryan


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## DanTheMan (Oct 12, 2009)

Thanks Brian. That's been my question all along, how do I determine where my problems are and where to place treatments? 

Thanks,

Dan


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## bpape (Sep 14, 2006)

Remove the treatments from the room. Take a baseline unsmoothed measurement with seating at approx 62% room length and speakers in a somewhat normal position (best by ear) but making sure that center to side walls and front baffle to wall behind are not the same. Distance to sides ideally will also not be a fraction of distance center to center.

From there, move the mic forward and back and see what, if anything changes. Move the mic side to side and see what changes. Once you get that pinned down, start with sub placement. After you find the smoothest place for that, then re-check your seating position measurement to make sure there isn't a better place now that the sub has moved. 

Once you do all of that, then you have the fun job of finding a place where the speakers are happy, blend well with the subs, and still image well. An infinitely variable sub phase adjustment can be a great thing.

Yes - in a perfect world you should be able to predict what exactly is happening and sometimes you can get close. But, in real world rooms with non perfectly square, non-perfectly rigid walls and no furnishings, doors, windows, etc. don't exist so there are variances.

Sub level is a little hot compared to the others. Turn it down say 3db.


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## DanTheMan (Oct 12, 2009)

Thanks Brian! I'll give it a shot Wednesday or Thursday as time permits.

Dan


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## DanTheMan (Oct 12, 2009)

OK, so I'm a little late reporting as it took longer than I expected and I still don't feel done yet. I am using the Mackie HR624mkII now and thus the graph titles.
























compare to where I started from:
he start:
[img]http://i836.photobucket.com/albums/zz286/my_graphs/Bass%20Trap/beforetreatmentavg1.jpg?t=1281676515[/IMG]









Thanks Brian. I think I may have a bit more work to do, but this is the next level for me.

Time for a bit more listening before bed. Life is good.

Dan


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## Stele (Jul 3, 2010)

Looks like your going quite well Dan and have some nice bass without any EQ.

I agree with Bryan that RT60 is of limited use in small rooms with your 'typical' furnishings. Now that you have begun measuring in 10 spots, I assume you only have 5 seats? So why the 10 measurement? have you been measuring the 10 spots across the 5 seats?

I wouldn't bother getting more then 2 subwoofers unless you go to 4, so they can drive the standing waves destructively. Almost the perfect solution is given by Toole (Sound Reproduction by Floyd E. Toole - for those that don't know) in Sound Field Management. Basically after all the measurements it places different EQ and phase response on each subwoofer so different listening locations have very little differences in bass response.
Does anyone know if anyone has a system that is commercially available yet?

Either way Dan your doing the basics right, testing different placement of subs and absorbtion to get the best you can before EQ. Kudos!

Pete


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## DanTheMan (Oct 12, 2009)

Thanks Pete! I can't count all the things I tried and the total graphs I made to get to where I am. I think REW was even getting annoyed with me. This was an enormous pain to get here, but easily worth every moment.

I actually have just 3 seats. I take 10 measurements for a few reasons. 1) I move around while doing anything. "Ants in my pants and I need to dance." James Brown 2) It helps to get better statistics in the area above the modal region where sounds behaves in essentially a statistical manner. 3) it lets me see where the modal response is doing what--which ways it's changing and how it changes with location.

SFM would be cool. I basically did the same thing by trial and error only with just phase, filter, and level adjustments. It's hard to stop. I'm thinking about it now. OCD.

Oh yea, never fear, I'm aware of the lack of the RT60 not being the most useful graph for small room acoustics. I believe I've talked about it in this thread. None the less, you can see the difference in the with/without treatments in the RT60 times especially in the statistical region and they are stable. It's really the best way I know to demonstrate an in room change there.:gulp: I know that they are really useful for larger auditoriums and help determine what music can be played there, but for small rooms intelligibility is more of a speaker issue than a room issue. Dr. Toole gives an optimal range of like 0.2s to 0.5s for HT and says pretty much everyone will fall into that. You can see I did/do either way. CSD/Spectrograms can be manipulated to make nice curves and may be better for modal bass range, but even there the thing that most correlates with what I hear is the FR. Above the modal region, the thing that correlates most to what I hear is the anechoic polar response and the RT60. I'm not saying it's the best, just that it seems to work well for me. I've asked for better systems of measurements before on other forums, but haven't gotten any answers.

You can see the only place where my bass varies a lot is at 55Hz. I can fix that but it causes other problems. 

I believe Harman did have a system like that for pro use, but I may well be wrong and their are multiple DEQX options and I want to say that even Paradigm had something. I'm pretty sure I'm getting that company wrong, but there was a high end company producing subs with a built in system like that.

Thanks,

Dan


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## DanTheMan (Oct 12, 2009)

Well I got a little lazy today with perfecting the room with just 5 graphs. It was a little bass shy and a little treble shy so I went about fixin it.

Here's what I came up with:
















And just to show something I keep seeing when I do these graphs and perhaps what's more relevant for me in the center seat vs. the room AVG. It always seems to look like this and perhaps why I prefer a slightly dull AVG best:








Then compare that the the same pseudo anechoic on axis vs avg no smoothing:









Cool stuff,

Dan


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## Stele (Jul 3, 2010)

Dan I've gotta say; nice curves! Taking a look back at what you started with and variances of 15-20dB to those latest graphs you've done a great job indeed.

In case you were I wouldn't worry too much about that slight 'grass' in the 1/48 octave graph, because of (you prob know this) the human ears + brain to listen through the room etc and hear the music/source what have you. It's a very nice 'real-world' flat response.

Now the most important question of all; can you hear the difference? And how does it sound?

Pete


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## DanTheMan (Oct 12, 2009)

Pete, you are so correct. I can't hear that grass at all--well if I can I'm unaware of it. The difference from when I started this until now is fairly large. The whole spectrum has improved in several ways. It would be impossible for me to describe it adequately, but I'm pleased with the money spent and improvement obtained. Of course it took more time than money, but I'll get to enjoy it for a long time to come. The treble was too wet--for my needs. I use this room for recording music and the reverberation/slap echo just didn't sound good on the recording. Everything had that ghostly hollow, vintage sound of The Complete Recordings of Robert Johnson. It just never sounded like a pro recording. Most of what I play is acoustic blues with a slide guitar, and the slap echo does give it an authentic feel(sounds old, cheap, bad, etc...), but I also do a lot of other stuff and the room just didn't work for that. Before getting this bass as correct as I have, there was always either too much here, too little there, but never just right. It was muddy one moment, lean the next. Now it's just right. It doesn't draw attention to itself in any way even though it's not perfectly flat or stable. I think once you get away from major bass problems, things just work much better. Still, away from the listening space, the bass isn't great and it's audible. So wile I'm doing other things, I'll just have to live with bass issues unless I'm looking to get into far more treatment. I think both imaging and sense of space has improved even though that runs counter to research. Maybe it's just my wishful thinking. Of course it could be that my musician ears only need 1/7th the reverb to derive a satisfying amount of it compared to non musicians. What's the difference between ignorance and apathy? I don't know and I don't care. :T It worked for the better.

One negative might be a slight loss of detail. That may run counterintuitive as well, but I think the extra reflections really do give our ears another chance to look at things and pick out more minutia. Some of that is good for a guy like me, some not so good. The difference is extremely subtle in that respect and the reciprocal faster, tighter, more dynamic(I know that can seem counterintuitive as well), dryer, sound is much appreciated. These differences are really subtle--well at least over this much time. My bedroom is untreated and has the same speakers, so I can hear the difference anytime I want. I definitely prefer the treated room, but even that preference is suspect. With all the work I put into it, I'm bound to appreciate the results of my efforts. I'd call it the home cooking affect.

Dan


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