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amishsixstringe 29th November 2011 01:45 AM

Lights, It sounds like you are well on your way to making the world a better place. Just go slow and test as often as possible. You will get the best efficiency by being uber anal retentive about measuring and moving.

Just remember, if you don't take pictures: it didn't happen.

Keep us up to date.


Lights 29th November 2011 02:53 AM

Thanks Neil. BTW: Awesome studio build pics. The home-made QRD diffuser looks phenomenal. I want one.

Someone recommended that I should make sure the speakers are 1ft away from the wall or the bass imaging gets all screwed up. My Mackie HR824s have a mode switch that you set for when they are up against the back wall (as mine are). Is this a problem? Should I be moving my desk out away from the wall a bit?

aackthpt 29th November 2011 01:01 PM


Originally Posted by Lights (Post 7277681)
Someone recommended that I should make sure the speakers are 1ft away from the wall or the bass imaging gets all screwed up. My Mackie HR824s have a mode switch that you set for when they are up against the back wall (as mine are). Is this a problem? Should I be moving my desk out away from the wall a bit?

There's no such thing as "bass imaging". The switch is to compensate for the boundary effect which changes the frequency response. Generally putting the speakers nearer to the wall improves the situation, but you should try it with the monitors in both positions and the switches in both positions, aiming for smoothest frequency response (when swept with REW w/ one speaker playing). More info here and here, note those cover interference issues for placement but not LF boundary reinforcement which is what the switch is for.

Lights 29th November 2011 09:06 PM

Thanks for the pointers!

Lights 29th November 2011 10:45 PM

Is this equivalent to FRK?
1 Attachment(s)
Hey guys:

My local insulation supplier has some Knauf 3PCF Ecose fiberboard available with the attached laminate product (see PDF). Is this equivalent to the OC703 "FRK" laminate?

amishsixstringe 30th November 2011 02:28 AM

Sounds like the stuff!


Lights 30th November 2011 02:43 AM

Great!! I'll just take the box of that and peel it off the doubled-up pieces.

Lights 3rd December 2011 03:54 AM

Ok guys here's an update. My "phase 1" project will be to fill the 6 right angle corners (2 front wall corners and the back corner behind the door) with large muslin-wrapped boxes of OC Ecotouch. The front two corners will each get 2 2x2x4ft boxes (stacked). The back corner has only 1ft between the wall and the door so it will likely get 2 1x3x4ft boxes (stacked). (All approximate sizes.)

The back angled wall will be next but poses an immediate challenge due to the 45* angles and the couch. I am trying to decide if I build a "bass trap bench" like the one DanDan linked to, replacing the couch with a functional bass trap... but I'll wait to see what my first round of bass traps yields.

I'll also be buying 10 2" sheets of Knauf Ecose (faced) fiberboard and use that to make 5 traps that can be moved around and mounted where they will have the most impact.

Lights 11th December 2011 07:29 PM


Originally Posted by Lights (Post 7280894)
Hey guys:

My local insulation supplier has some Knauf 3PCF Ecose fiberboard available with the attached laminate product (see PDF). Is this equivalent to the OC703 "FRK" laminate?


Originally Posted by amishsixstringe (Post 7281673)
Sounds like the stuff!


Hey guys--I wanted to double-check on when it's appropropriate to leave the facing on the back of the panels. I purchased 10 sheets of the faced Knauf Ecose 3PCF fiberboard. I can easily peel the facing off. I haven't seen anybody leaving the facing on when I look at poster's DIY bass traps. On the other hand, I've seen advice that the facing works better when left on the back panel for low frequencies.

Can anybody tell me (or point me to a thread that tells me) definitively when I should build a panel with the facing on and when I should remove it? I'm building the panels now and would like to know what the right solution is.

Lights 20th December 2011 03:12 AM

First Bass Traps Completed
2 Attachment(s)
Hey folks. I have the first 3 bass traps completed. Each is 4" thick with Knauf Ecose 3PCF Fiberboard (unfaced). Two are the normal 2ftx4ft dimensions and one was designed to stand on its side under my desk, so it's 20in x 4ft.

Here are some pictures.

I'm getting the mounting hardware later this week so the other two aren't yet mounted.

Next come the 4 soffit pieces that will fill the corners to the left and right of the desk. They will be 22in x 22in x 4ft (set of 4 to fill 2 corners top-to-bottom).

Edit: if you are wondering why the bass trap under the desk, when you look back at the room diagram, the standing wave around 50Hz is exactly twice the distance between the front (desk side) wall and the back wall. I took an educated guess that bass trapping under the desk was an unobtrusive way to dampen that standing wave. The open underside of the desk is a little more than 4ft wide, so almost the perfect size for a couple sheets of fiberboard.

Lights 21st December 2011 06:53 AM

Room Treatment Plan
1 Attachment(s)
Attached is my current room treatment plan. With the 2 panel traps and the under-desk panel built and of course the foam stuff I already have, I have 2 more panels and all of the soffit traps to go...

Still pondering the custom bench filled with R-30 as pictured.

Any thoughts are welcome.

Lights 23rd December 2011 07:28 AM

3 Attachment(s)
First two wall-mounted bass traps are now installed. I hung them in the side "first reflection" point. You can see from the side view that the traps used 4" dowels mounted in holes drilled in the frame's corner braces to achieve a 4" air gap.

The last picture shows that, because they're at the first reflection point, I added 2" auralex foam panels to the front because Sound on Sound recommended it, rationalizing that bass traps aren't as good at the higher frequencies. That makes these particular traps 6" thick. I don't anticipate adding this treatment to the other traps.

I'm not going to re-measure until I at least have the floor-to-ceiling 2ft thick soffits in the front corner (that would be to the left of the bass trap pictured here filling the gap between the desk and the corner).

amishsixstringe 25th December 2011 10:12 PM

Nice. Keep updating.

Note: Usually on the side wall reflection points, you'll want about a 4' wide panel on each wall in order to give you a larger 'sweet spot'. No big deal if you can't get that with what you have. Just keep in mind that as your head moves forward and backwards in the room, you could start receiving reflections that are unwanted.



Lights 25th December 2011 10:52 PM

Thanks Neil!

Good note on the side walls. Those panels are exactly in the sweet spot and directly in front of them will be the 2' deep soffits that should absorb anything that comes near it ;). I could place additional, identical panels directly behind them as well creating a 6' zone of absorbancy from the front to a couple feet behind me.

Question... I was thinking about just using the just 2'x2' auralex panels directly behind those front bass traps, perhaps setting them off the wall an inch or two. In this no reflection zone, do I need broadband trapping or just protection from flutter echo?

amishsixstringe 26th December 2011 02:30 AM

The panels on the side walls are really there to just absorb frequencies above the critical frequency of your room. They are there to get ride of first reflections from that point. They don't NEED to be that deep to do that. The bigger the space they occupy, the larger the area is (front to back) that is treated by those pieces. However, if you make that area too big, you start really getting rid of any liveliness in the room. So, you want them to be as small as you need them to be.

Have fun.


Lights 26th December 2011 03:57 AM


Originally Posted by amishsixstringe (Post 7367206)
However, if you make that area too big, you start really getting rid of any liveliness in the room.

Well that brings me to my other question ;-)

(Also there's an updated treatment plan attached to that thread.)

Lights 1st January 2012 10:26 PM

Big Boxes of Pink Fluffy Insulation
1 Attachment(s)
Here's one ~2x2x4ft box full of Owens Corning Ecotouch sent from my friend's mobile phone. (He's the woodworker... I just buy the materials and pay him in microbrew and a little extra for his time.)

Attachment 269679

Really hoping I'll have all 4 boxes to fill the front 2 corners by EOD... He's made 2 more panels and I have a bag of 10 more sheets of the Knauf fiberboard and another bolt of fabric waiting for him in my garage.

Once I get the front corners filled, I'm going to re-measure the room.

Lights 8th January 2012 06:12 AM

2 Attachment(s)
Ok folks.... I now have 5 bass traps installed and floor-to-ceiling 2ftx2ft boxes of OC Ecotouch in the front corners. This is about half the treatment I intend to have so I thought I'd take some rough measurements. Note that the dryer was running in the next room and there was a bit of other background noise, so these aren't in a perfectly quiet environment but they do look quite different from my original untreated images.

If you recall, here is the original untreated left speaker waterfall:

Here is the current left:

Here is the original untreated right speaker waterfall:

And here is the current state of the right speaker:

I'd love any thoughts...

It looks like things improved a bunch, but I do still have some low ringing as well as a few nulls. In fact with the left speaker it looks like I managed to *add* a null that didn't exist before at 41Hz although overall the graphs seem MUCH smoother.

Lights 8th January 2012 10:19 PM

4 Attachment(s)
Here are some photos of the corner boxes installed and 4" bass traps installed.

There are 4 boxes to the left and right of the desk that are 2'x2'x4' stacked on top to go floor to ceiling. I wrapped a little acoustic foam in between them around the 1.5" wood frame that allows the two boxes to stack, which explains the black band in the middle. The boxes are made with a light wood frame and muslin fabric. All sides but the top and bottom are 100% acoustically transparent (aside from a small bit of wood running up the corners).

Also attached is a closeup of the right stack of boxes, a shot of the first bass trap I mounted in the ceiling corner (pretty easy actually), and a shot of the trap under the desk meant to chip away at that 50Hz bump since it's at the right distance from the back wall for a standing wave.

I'm still planning to put 5 more of the 4" panel traps in (spaced 4" from the walls or straddling various wall-ceiling or wall-wall corners) and still figuring out if I can manage another big box directly behind me, but that one would be sticking out into the room and would feel rather claustrophobic.

Would love feedback on the graph changes, BTW!!

amishsixstringe 8th January 2012 11:56 PM

Your graphs look fantastic. Especially since you still plan to add more. Note, that your improvement will probably be less noticeable after adding the second wave of trapping. That's ok. Your room looks wayyy better than before. It kills what the auralex stuff was(n't) doing for you.



amishsixstringe 8th January 2012 11:59 PM

Also, if you want my advice, I would sell/lose the foam on your front wall. Maybe leave the LENRDs at the top of that wall, but that foam on the front wall isn't really doing anything for you acoustically, but it is probably just making your room sound kinda dead. I would like to see ETC and RT60 and waterfalls with and without that foam there.


Lights 9th January 2012 12:15 AM

I had a lot of nasty flutter echo in the room prior to adding the foam. Everything sounded kind of harsh. Just to my ear, the foam helped a lot.

I'm not going to use it all over the room, just in the key HF reflection points. That way the room can stay live enough but be far less harsh.

I think I can pull up the graphs you want pre/post foam just using the existing measurements I did for the waterfall, since they were full-range sweeps if you tell me specifically what you want there... of course the original had no treatment at all... so you'll have to tell me if that's worthwhile.

amishsixstringe 9th January 2012 12:27 AM

I would suggest moving them to the back wall then. As a LEDE design concept, the front wall is usually bare. Wait, you had an "L" shaped room right? hmm... I'd still get as much off of that foam off the front wall that you can while keeping your flutter echo problem at bay. Do it in a checkerboard pattern. Keep the opposite wall clean. I would recommend the front wall bare and absorb the back wall. Better yet, use some of your new traps and completely bail on the foam. Really, in most cases that foam stuff only hurts due to its extreme narrow band of useful absorption.


Lights 9th January 2012 01:25 AM

Thanks Neil... noted. Yea, if you look back to page one you can see the wacky shape of my room.

The reason I have the foam there (and on the ceiling and on the front of the bass traps to the sides) is that the recommendation from the room treatment section of "Mixing Secrets for the Small Studio" suggested foam on all the surfaces where the reflection will be, including the front, back, and side walls... as well as the ceiling in all the reflection points.

A similar recommendation by Sound on Sound magazine can be read here: Room For Improvement

I don't know much about LEDE, I'll read up. But for a non-acoustition like me, it's tough to balance all the conflicting suggestions :-S

amishsixstringe 9th January 2012 01:39 AM

I understand. However, those foam things absorb almost nothing in the low end of the spectrum. At the same time, your speakers don't shoot high frequencies backwards (at the front wall). Therefore, they are not doing anything really.

You are putting a crap ton of fiberglass in that room already. You are going to start really killing the top end as is. That foam stuff just absorbs even more of it.

I'm hoping that the rest of the absorbers you are making will solve your flutter echo issue and allow you to get rid of that foam completely.

Do you have an RT60 in your REW file that you can share?
You don't have to remeasure to get that info. You can generate it from the files you already have. Before and after would be cool.


amishsixstringe 9th January 2012 01:43 AM

Just to add:

These are only observations I am making based on photographs. I can't hear your room. We are also missing a lot of your measurement files. Waterfalls are only one small part of it. Remember that everything should have a reason for being there. If it doesn't help, it hurts. Can you upload the actual REW file for your before and after measurements? I can then open them in REW and see more information (as well as other members here).


Lights 9th January 2012 02:04 AM

Shoot me a PM (EDIT: with your email address) and I'll send you the REW file. As I recall, they're too large to attach to Gearslutz.

amishsixstringe 9th January 2012 03:32 AM

Cool. Thanks for the email. I'm checking things out a bit.

At first glance (I might post a few screen shots and things tomorrow) I see a pretty hot early reflection at about 2ms on both speakers. It is most likely your desk or your computer screens. It is about -15dB. I would try to find that reflection and get rid of it if possible. There are also 2 spikes in each left/right speaker. Right around 10ms and 15ms. Probably ceiling/side wall reflections. Maybe even your chair or floor or something. I'd hunt those down too.

The waterfalls look really nice. Things are SO much smoother. Not only the bottom end, but all the way up is just looking much better.

Something weird happening in the RT60. The absorption seems like it has actually made things less even in decay. Maybe someone else can look at this? I'm not exactly sure what's going on there. The low frequencies seemed to have evened out much, but the lower mids seem 'over trapped' even. I don't know if I will offer any input here. I would see if somebody that knows more than me can touch that one.

I think overall, things are shaping up nicely. The impulse response had tons of early reflections, and you seem to have gotten them taken care of besides about 3 of them. The low end/middle have much more smoothness to them. I don't get the RT60 thing going on.

Most important, have you had a chance to listen to any music in there yet? I'm sure with that drastic of a change in your measurements there should be some noticeable difference in real life sound. That is ultimately what matters.

I'll check back in tomorrow.


amishsixstringe 9th January 2012 03:38 AM

I just looked at your photos again. Are you planning to replace your cloud and side wall foam with new absorbers? I believe that those are allowing enough reflection to still see significant spikes in the impulse graph. What is odd to me is that the 2 spikes in the more recent measurements are new. As in, they don't exist in the 'before' measures. So, I think you might be seeing some grazing effect from either the bass trap or the foam cloud/side wall things.

I would try to run one more sweep with the only thing changed being the removal of those foam pieces at the side wall spots. Just to see what changes. It will help you figure out what is causing each offending reflection.


Lights 9th January 2012 06:54 AM

Posting some pictures with circles and arrows would help. I figured out how to read the waterfall, but have no idea how to find early reflections, etc. I've been mostly focused on bass measurement since that seemed to be the thing that's the hardest to deal with in small home "studios" like mine.

On the early reflection--It takes 2.69ms for sound to travel 3 feet. the distance between the tweeter and measurement mic is 3 feet. When you say there's an early reflection around 2ms, that must mean it arrives 2ms late, which implies it needs to travel a total of 5.24ft (if it's exactly 2ms) an additional 2.25ft or so. If that's the case, it's not likely the desk or edge of the monitors, right? At the strongest possible echo point would be along the straight line from the tweeter to the desk and back to the mic and at its longest, the distance is approximately 4ft--only 1ft longer than the direct signal. That would make it only .89ms. The LCDs are flush with the Mackies, so they'd be even shorter if they generated any reflection at all. Did this analysis make any sense at all? I'm just guessing at how to calculate this stuff :)

Assuming I'm right, a reflection arriving 2ms after the original one would have to travel about 5 to 6 feet of total distance between the speaker and the mic. So on that one I'm stumped. If it were coming off the desk, you'd see a MUCH louder early reflection at .89ms or even earlier.

Hmmmm... the ceiling is 4ft away from the tweeter and the mic at the "mirror" point, making a reflection there 5ft longer than the direct path for a 4.48ms early reflection. So that's not even a candidate for the 10ms and 15ms hot points you noted either. The sidewall is nearly identical--the mirror point is just about 4ft from the tweeter and the mic again making a 4.48ms reflection after the initial arrival of the sound.

Let me think here...

Ok... the back diagonal wall at its closest has a 13.3ft round trip between the left speaker and the mic. Sound travels 13.3ft in approximately 12ms. Subtract the 2.7ms it takes for the sound to reach the mic directly and you have 9.3ms. Maybe that's the 10ms peak. I guess you could come up with all sorts of wacky axial angles that could potentially be some of these reflections but I couldn't find a simple angle that would do the same for the right speaker or 15ms for either speaker. Also given the odd shape of the room, I'm stunned we're seeing the same behavior from both speakers!!! I'd imagine these have to be coming from behind the listening position if the analysis I did was right.

BTW: the chair was pulled out of the room for the measurements.

All of my calculations assume that the the miliseconds you gave me were after the initial sound hit the measurement mic (which would have taken 2.69 seconds).

Ok, onto another topic! The side mirror-point absorbers are the same bass traps (4 inches of knauf ecose 3PCF fiberboard, spaced 4 inches from the wall) with an additional layer of 2" acoustic foam on the front, as suggested by Sound on Sound's room treatment guide because fiberboard isn't good enough at high frequencies at first "mirror" reflection points. I could very easily pull the foam off (the foam tiles are simply pinned to the fabric on the front), but wouldn't that increase the reflectivity?

I'd rather get the room too dead and have a very even response with no reflections and then remove absorption or add targeted reflectivity to add liveness back into the room while making sure I'm not bringing any dangerous reflections into the picture.

I hadn't thought about replacing the "cloud" of acoustic foam on the ceiling, but to the left and right in the wall-to-ceiling corners I am planning on placing the bass traps (basically right over the traps positioned at the side).

The big boxes of OC Ecotouch are effectively behind the face of the speakers.

To answer your question about how the room sounds -- it is massively different already and I only have half the bass traps in. Just standing in the room in "silence" sounds different. The air sounds different. And the music does as well. I'm hearing all sorts of imperfections in my reference songs I never noticed before. (Wife is a big U2 fan and was listening to some of their newer CDs and wondering how they can produce such poor sounding mixes when they are the richest band in the world--I never noticed that before!)