Axiom Home Page Forums General Discussion Home Theater I need some help with room analysis and treatment…

I’ve been avoiding this for a couple years now. I’m now convinced that my room needs some help. Some of the BR movies have so much LFE that it’s hard to not notice that I no longer have smooth and linear bass response. Audysey helped, but I'd like to work on the room now with the goal being to ditch the EQ.

I know nothing about this. I believe I’m supposed to download some software and measure the room’s characteristics somehow, then based on that data, figure out if I need bass traps and where to put them. I do have a laptop, although it’s several years old and painfully slow. I have no idea how to get a microphone to work with it (assuming I’ll need one).

Anyone care to help with this? I am on infant and need to start with crawling….

Well, you could try starting here...

http://www.hometheatershack.com/forums/r...lease-read.html

You'll need "time" and "patience". How you doin' on those?

Time...not good. Patience....I'm actually getting better at this. I'm paying for the sins of my youthfully arrogant position that I couldn't ever get hurt, which has very recently made me appreciate patience.

Another solution is: money. Most of the companies which make treatments offer paid consulting services. So if you don't have the time and patience to do it on your own, you can throw cash at it.

If that's not an option, you can usually get a little free advice them them anyway when you are about to purchase some product.

I like to do things on my own; this helps my desire to understand how things work. A good introduction to the science of acoustics is the book Master Handbook of Acoustics by F. Alton Everest.

This is going to be complicated... I've been reading some info on the link Tom gave me. I'm thinking this will be a good winter project, next year.

I've always did things myself Chris. For the same reasons as you, plus I'm generally not impressed with what I've paid others to do for me.

I think Randy's old superchunk bass trap thread was pretty good, too. I'm too lazy to google it for you

I used Owens Corning 703 rigid fiberglass, that I picked up at a local insulation company that sells to builders. After building some easy DIY frames, and locating some black stretchy material like speaker grill cloth at Wally World (sorry Tom), I was good to go.. page 1 and 3 have pictures of the superchunks and first reflection panels.

http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showflat&Number=144079&fpart=1

Hi,
Safe and Sound by Roxul is a good product too to build something like that. Also, you can find accoustic foam on eBay depending on your needs. Foambymail has a product with the same density than major accoustic brands for a fraction of the price. I have some in my home studio and it does a good job for what I needed.
http://www.foambymail.com
http://www.roxul.com

I'd feel more confident if the company made the effort to correct poor spelling on their site.

"Instalation made Easy"

"Inexpesive"

"Intersted yet?"

I couldn't find the incorrect spelling you elewded to, Mark.

There are three companies that you can send room diagram to and they will suggest room treatments for your room (that they sell).

1. Echo Busters: it could run you around $4000

2. Media Specialty Resources: they have several levels of pricing but I think they are more expensive than Echo Busters in the end

3. Auralex Acoustics: it could run you around $4000

If you don't have a rectangular room, then I don't know if you will be able to figure much of this out on your own. Even if you have professionals coming on site taking measurements and such, the outcome won't be as good as if your room is rectangular to start with.

Keep us posted on the results when you actually start putting them together. This is something that I would like to do sometime down the line. I've only been lightly researching this.

- Nick

That old thread is good, thanks for pulling it back to the surface.

Thanks for posting the link Randy. I had forgotten all about that….. I have a lot of catching up to do.

Am I on the right track with this endeavor? Isn’t the first step to get the equipment and software to analyze the room? Then, based on that analysis, figure out what type of room treatments is needed and where to locate them?

My room dimensions are 12’ 2” wide X 13’ 6” deep, with a 2’ 4” X 8’ open area in the back of the room where I keep my equipment and DVD’s. The height is 8’ 6” with a soffet around the perimeter that’s 24” wide X 12” in depth. I have hard wood flooring, and am using a 8' X 10' wool rug.

I figured that I should start with the homework first, then ask specific questions as they come up. I plan to chart my progress through this as I go.

Yes, you are going about it the right way. You might also do some reading in this forum at hometheatershack as it is all about room setup. It will give you a lot of ideas about how to approach this whole thing.

Animal. That Roxul is fine for some things, but for the most part you want a high density material, at least 3lb per cf like the 703. I was lucky and was able to source some stuff from Ottawa Fibre at $60 CDN for 4 sheets of 2'x4'x2".

For instance, if you want to make a really monster corner bass trap, you could start with a 4-6" thickness of the high density stuff across the corner, and then backfill with something like Roxul.

Ethan's Realtraps website was one of the first sites I started learning about things. Of course, they manufacture their own products, but Ethan has always promoted DIY, for folks that would like to build their own.

Ethan's Acoustic Treatments and Design page also has tons of info.

You can also just google "DIY Bass Traps" or similar search..

In a nutshell, low bass collects in corners, that includes floor/wall and ceiling/wall. However, most of us can't apply bass traps to every location. The corners can either have panels stradling them (at least 4" thick), or superchunk triagles filling the void.

First reflection panels, are those that are placed on the wall/ceiling at the point where the first reflection comes from the speaker and bounces to your ears. This reduces echoing and the skewing of the sound arriving at your ears at different intervals. You don't want to completely deaden a room, but treatments are just as important in a HT environment as they are in recording studios.

I think Ethan's room has over 20 panels and he says it is about as acousticaly flat in frequency response as it can get. He can pretty much walk around the room and find very minimal peaks/nulls without multiple subwoofers or EQ. He is not a believer in EQ.

There are also companies that make very affordable great products, so you don't have to mess with making them and time required. RickF has purchased from GIK Acoustics and they make nice stuff fairly a affordable...

Those are some great links, Randy. Tks

Ya, thanks Randy!

I've got 6 sheets of 2x4" x 2" thick sheets of Owens Corning 703 that I didn't use, but not sure how I'd get them to ya.

Thanks for the offer Randy. This stuff is expensive here. $15 a sheet for plain and $18 a sheet for foil backed. (both 2" X 2' X 4')

I haven’t done a whole lot of studying other than read through some of the links provided. I’m beginning to think I’m opening a can of worms with this room analysis stuff…..

Regardless of whatever the room looks like on a graph, there doesn’t appear to be a whole lot that a person does differently. From what I have read, you still treat the room with the same things. Different insulation density for to tame different frequency spikes is about all the options available. And, it looks to me as if each room still gets the same generic treatments. Corner bass traps, ceiling mounted bass traps and traps on the forward walls at the first reflection points.

Considering all that, I think I’m just going to start with corner traps and hang a trap from the ceiling. Depending on how things sound after I build / install those, I may try adding some more treatments to the walls where it is practical to do so.

I figured I’d make the traps out of fiberglass rigid insulation, 4” think. I’ll use foil backed panels on the back side of the traps with the foil toward the walls / ceiling and un-faced panels on the room side. For the corner panels, I can’t really make them permanent like Randy’s. I’m thinking about making them 24” across the front and build them so they will be free standing with some means of attachment to the walls at the the top (chain or Velcro) to keep them from falling over. I’ll hang the ceiling trap from chains.

I’m going to buy the insulation next week and hopefully, time permitting, make and install them. The ‘store’ that sells this stuff is 300 miles away. That’s also where I’ll have to find some sort of fabric to cover them with.

Anyone see a problem with this approach? Should I just get enough of this stuff for side wall traps too? What is a good, reasonably priced fabric? Velvet is pretty expensive…..

Just a question. Why are you using foil faced insulation?

I think you want fabric that approximates "acoustically transparent" or it will defeat the purpose of using the fiberglass.

Ethan told me to.

Just kiddin. The link Randy posted above to Ethan's page discusses the merits of foil backed pannels.

Some acoustic companies use burlap - ATS Acoustics Burlap

Thanks!

Is that something that's found in a fabric store?

I can't say that I know that answer. A phone call to your local fabric store may help though.

After an hour wandering around a fabric store, the only material I found that wasn’t $30 a yard or more, and didn’t look like something you’d find on a prom queen’s dress or down comforter, I walked out with some material similar to Carhats. Of cource they didn’t have it in black though. Next time I need fabric, I’m sending the women. What an awkward experience that was….. A very nice elderly lady took pity on me as I was walking around like a zombie and helped me find the stuff I ended up buying.

I’m going to start building these boxes today. I never gave any thought to what material I should use on the back side. I was planning to just staple some ¼ plywood to the backs to enclose the fiberglass, but also give them some strength. Now I’m wondering if that’s such a good idea. It shouldn’t matter, will it??? Anyone??

That will probably change the performance a little, but I can't remember exactly how.

For the two traps I built, I just split the plastic bag the acoutic sheets came in in half and used that as a backing to keep the glass in.

By the way, now that you have gone through your fabric adventure, muslin is very acoustically transparent and inexpensive. I don't know if you can find it in black though.

If you want to know how the plywood backing will affect your trap, check out the Home Audio Acoustics forum at hometheatershack.com. The guy who moderates it and answers most of the questions does room treatments for a living and is very knowledgeable.

For the frames, a biscuit joint works great and lets you leave the back open. Then just staple the fiber to the inside edges. If you don't have a biscuit joiner, you can still just cut a slice in the corner and put a biscuit (cheap at HomeD) in and glue it up. Saves time and, more importantly, weight, without adding a reflective back. Just and idea, worked for me.

The custom Art option is a huge improvement over the burlap otherwise available. To date, I have seen nothing that makes it worth buying these pre-made. But the ability to actually cover it with OK art might be worth the huge markup on the actual trap. Thanks for the site.

I was thinking of cutting the walls prior to painting for some inset traps just at my main reflection points. I plan on putting two paintings at at these points anyways. My question is, will the painted canvas defeat the purpose of the absorbent trap hidden behind it to levels where it isn't worth it? I'm not concerned enough to bother with traps if the paintings are not a good cover. The art was a nice and generous surprise made specifically for the HT room so I'll be using them one way or the other.

I'm interested in the answer. I took several framed pieces in my room and removed the glass, and added insulation behind the print. Not sure if it works, so hopefully some can give us an answer about the reflective property of painted canvas or paper.

This is getting complicated. The more I read on Ethan’s page, the more confused I get. My lil project is on hold till I can figure this crap out a bit better. I’m not even sure I can use the fabric I bought. Ethan says you should be able to blow threw the fabric with relative ease. The stuff I bought takes effort. So if I use it, it will reflect high frequencies. Not sure if I want that to happen, it doesn’t sound good.

There’s deep bass, mid bass, high bass, mid-high frequencies. All require different trap building techniques.

What did I get myself into…………

Ditto.

OK, back on.....

I just got this from Ethan.

------------

Corner bass traps are out of the way of direct reflections, so they should have the paper/foil facing toward the room. This absorbs more bass, and avoids sucking out all the mids and highs. This article compares faced and unfaced rigid fiberglass at various densities:

Density Report: http://www.ethanwiner.com/density.html

In all cases the facing is toward the room.

Regardless, you do not want plywood behind corner-mounted panels.

--Ethan

There's a term for a bass trap design which has a solid surface on both front and back with absorbent material between, but I can't remember it. Ahh, here we go -- a membrane absorber or panel trap. Anyways, I guess the foil facing acts as the front part of that mechanism...

good stuff, thanks for the link.

Mike, did you ask if they had speaker cloth?

When I went in to the local fabric store (Jo Ann Fabrics), I asked an employee if they had speaker grill cloth... thin and stretches both ways. Yes we have 'speaker cloth' and pointed me to it. It was black and maybe 60" wide (might have been less, hard to remember). I did not buy is as I was looking for a color to match my wall. As I recall, it was not expensive at all.

Mike if you do make some bass traps post a couple of progress pics if you don't mind, I'm using the Tri-Traps from GIK but they stack and I'm considering replacing them altogether for a cleaner built-in look. Dave that's cool about Jo-Ann Fabrics having the speaker cloth, that is one store we do have in town.

Mike, if you don't have a Jo-Ann's or can't find the speaker cloth, let me know and I'll pick some up and send it out to you.

Thanks fellas. The store I went to was Jo-Ann's. The female creatures that were being paid to assist, were not very helpful. Downrite bitches actually. The elderly lady was a sweetheart though.

The stuff I have, I'm pretty sure will work just fine for corner traps. Hell, that foil backing isn't anything a person can blow through, so I fail to understand how cloth makes much differnt - at least with this type of trap.

I'll post a couple pics. Things are pretty ugly so far. I had to get creative.........

Yeah, you don't need speaker cloth for bass traps, or first reflection panels for that matter. As Ethan always said, if you can blow through it with your breath and feel it on the other side with your hands it will work. Many people use even burlap material for bass traps. Bass freq's go right through. I would not pay extra for speaker grill material, JoAnns or even places like Walmart should have some black stretchy material much cheaper.

Have any of you guys checked out Ethan's bio? The guy is quite amazing. He was a programmer who ran his own company, took up the chello (I think) in his 30s or 40s and became a professional musician and now runs a company making acoustic treatments.

What's the simplest way to do a quick before / after sweep? I see where a lot of folks on this board post before / after trends.

I'm assuming that I download and install Real Traps. It looks as if I use my RS digital meter.

Yes, I'm being lazy. I start reading and get glossy eyed. I’m looking for a real simple, step by step cheat sheet of sorts.

REW is the best way to do sweeps, once you get it set up. Its not that complicated, but there is a learning curve.

Hauling traps around is always fun...

I had an interesting (to me!) experience at an NBA game on Wednesday. Sitting in the nosebleed section, I was able to see the speaker array used, up close. To my surprise, it was not of the normal rock band size. Not small, but not what I remember from Van Halen or Metalica concerts. But, even in this massive open and hard sided arena, the bass at my seat was solid as a brick to the gut (call it bowel shaking ), with no thunder decay or muddiness at all. The more I paid attention, I was surprised that the music was very solid and clear, the announcer’s voice was clear, and there was no echo at all, despite the cavern of cement under a steel roof.

So I started to look for the acoustic secret – and I found it. First, human flesh. There was lots of it. But more importantly, I think, from the ceiling they had large rubber mats, suspended in a weak U shape. Lots of them. That was all I could see after close scrutiny. That got me thinking about some of our discussions here about the need to be able to blow through the material, the depth of insulation, etc. Relatedly, it reminded me of the well accepted use of sound deadening material on the auto side.

I know “those bass heads” have nothing offer true audiophiles (even if half the people on this thread have more subwoofers than 80% of those "mobile" bastards), but I have used several products to kill the road noise in my SUV, with exceptional results. Those products, like the rubber mats at the arena, use a rubber or tar based membrane to convert sound energy to heat. These products are less than a quarter of an inch thick, and the rubber mats at the arena were no more than an inch thick (and about 3 feet wide).

Why then, in the more heady home audiophile realm, are we constantly talking about compressed fiberglass 12 inches thick to kill a bass note or stop an echo? Has anyone seen a study of the acoustic properties of thin rubber and tar membrane products as compared to fiberglass? Please give us your thoughts on this, as we could all benefit from a half-inch solution to a 12 inch problem. . . that did not come out right.

Below are a few cites I have used to learn a bit about the tar based products for anyone interested: Tech Talk Jay Leno uses it
B-Quiet
Background

What is "REW" ? Can someone (not too) briefly explain the process and what is needed to get this graph info? Does this process give you a graph, or just individual data points you manually put onto a graph? I assume you need a laptop (not Mac), a RS SPL meter and this 'REW'.
(working to abolish [my] ignorance.;o)

Try this

http://www.hometheatershack.com/forums/rew-forum/

You might find reading through the REW user guide to be more helpful than wading into those forums. I found the forums to be for advanced users who actually knew what the heck they are doing.

http://www.hometheatershack.com/roomeq/wizardhelp/help_en-GB/html/gettingstarted.html#top

I don't think I'm going to mess with it. My laptop doesn't have enough memory or a good enough sound card......or so I think.

I used to use REW, but have had issues getting the sound card setup, using the REW interface is not exactly for newbies, and the SPL meter is not really a great Mic.

I recently came across this Frequency Response Plotter which seems to do an awesome job, and is very easy to use. Yes, I've been graphing again, and have some very impressive results. Oh yeah, and I've found that using my Mic that came with my Denon does a better job than my SPL meter as a mic, seems more accurate.

But the RS meter has Calibration files that you use to adjust for it's short comings, making its reading very reliable.

yep, I'm aware of the calibration files, the above program can use calibration files as well. Even I'm an IT guy, I just thought REW had a learning curve that many may find not worth the time. By the way, the above graphs are not mine, just a screen shot of the application.

So far I've been able to get graphs from 18-150hz in 1hz increments with less than 5dB difference across the range.

Thanks Randy. That's what I wanted to hear, easy to use....

I think I need to get a new laptop. Actually, I know I need to get a new laptop. The one I am using was a dated POS when I got it.

If anyone has a line on a good used laptop or new one, shoot me a PM. I am looking for an inexpensive laptop that will do nothing but sit in my HT and be used for equipment firmware updates, display calibration and run one of these room analysis programs. I’ve been meaning to get one for a while now. It’s just not very high on my list of stuff to buy.

One thing to keep in mind is that some that use laptops for graphing their room, use an external USB sound card, versus the built in sound card. One of the steps using rew and other programs requires you to calibrate you sound card by running a cable from the "out" jack to the "in" jack. I could never get my laptop to run this step.. I use my desktop computer, HT computer. It has jacks on the back of the pc, and I've had better luck than using a laptop. then you have to use a long cable to reach your seats.

I never thought to use my desk top. My office is roughly 40' from the HT. Do they (they being "they")make a cable long enough? What do you think????

Well, I've used my Denon mic before, that has a pretty good length. Or, if your using a Radio Shack SPL meter, it has an output jack, so you can just plug a long cable with RCA ends from the meter to the sound card jacks, you might need to get an adapter cable that goes from RCA to the jack size for the computer soundcard, I think 3.5mm or something like that.

My HTPC is hooked to my projector, so I can watch the graphs as I took measurments.

I also have an old laptop, but thankfully it was good when new so I'm getting buy. Wanted to let you know that I am headed out to buy the Behringer USB Audio Interface (U-Control UCA202), that is supposed to work as well as the external sound cards, but only cost about $30. Might bet you past needing a new sound card. Also, Creative makes a sound and video external box. For a few hundred, you could probably get all the processing you need without buying a new laptop - I assume you already have USB ports, Ethernet, a keyboard, monitor, etc?

Mike,
Thanks for the link. Before my eyes glassed over (am not an IT guy), it gave me some idea of what's involved. But not until reading more posts here, seeing the term 'program' did I get that REW is software, not an acronym for something or name of a piece of hardware. ;o) Sounds way more involved that I would want to even try getting into. I'm a Mac guy (iMac 2.16Ghz Intel Core 2 Duo. 1.5 GB ram and OLD Powerbook). My wife has a one year old Dell Laptop (Latitude D620). Do PC laptops usually come with an (internal) sound card? Would any particular input or output ports indicate the presence of a sound card? See, I am not an IT guy. Maybe this level of lack of knowledge translates to: "Dave, skip this graphing stuff!"

Yes, they do. They're generally integrated, as they are on Macs, but if it's got speakers, a headphone jack, and/or a mic jack, it's got a sound controller of some variety. Many times an outboard card/box is preferred because of higher quality or physical isolation from the rest of the (noise producing) electronics in a computer.


Also: Dave, skip this graphing stuff.

Well my traps are installed. Well the two front traps anyway. The rear (I only have three corners as a door is in one corner of the room) corner trap is just there temporarily as I have to re-mount my surround back speaker. I’ve been meaning to swap out the M3’s with another set of QS 8’s back there, so this is a good excuse to do that now. When the new one’s show up, I’ll consider doing some sweeps.

The traps definitely did something. The LFE feels as if it’s doubled. I definitely need to re-calibrate things. The house is full of women right now and they have effectively driven me out of the house. I’ll post pictures tomorrow. I’m getting out of dodge now……..

Ken,
Moving on here, nothing to see (hear)...

PS. When I saw your Mac, I knew you could be trusted!

You can run some RCA terminated coax for as long as you want to enable using your desktop.

I have been using an external creative labs sound card with great success. The initial calibration check of the SC comes back dead flat compared to my PC on board SC which takes a nose dive at 70hz and lower.

http://www.soundblaster.com/products/product.asp?category=1&subcategory=208&product=17751

Jay, are you using that Creative card with REW?

I have the older soundblaster 24 bit external but I just could not get it to work under Vista. REW with that card was butter under XP though. I don't think REW is all that difficult to use.

I am using/used that card with REW, but I have yet to try it with Vista, that was my next thing to do, but I am not doing anything these days

Rick wanted pictures….

I ended up using some ½” birch plywood for the frame. No particular reason other than that’s what I had on hand. I just cut rabbits with the table saw and dado blade, then used ¼” narrow crown staples and glue. I wanted the traps to fit snug, but be removable. That’s why they are 45’d. As luck would have it, receptacles are in the way, so I had to cut windows in the frame for those.





I cut the insulation with the tables saw. It cut easier than I thought it would. The fibers didn’t go all over the place either. I used 2” thick un-faced and 2” thick foil faced.




After the frames were stuffed with insulation, I rapped them in black felt. The felt does two things, 1) keeps the fibers contained 2) softens the corners for the fabric.



I had to make some stands for the traps that would keep them from toppling over.



For fabric, I ended up with the same material that Carharts are made of.




I got lucky with the color. The traps match my room color exactly. I couldn't have planned that if I tried.





I had to remove the surround back speakers. I was useing M3's. I have some QS8's on order. I plan to move the surround speakers toward the front of the room two feet as well. I screwed up when I ran the wire for those, placing them too far back, plus, the window and door are right where I want the speakers to be. I have some Axiom ceiling brackets on order and will hang the Q's.

Great work! Your room is definitely one of the ones I'm jealous of. That's amazing about the color.

Mike, looks awesome man! Your a better craftsmen than I hands down.

That's a pro job. Looks fantastic. But you should really get some wood tools and a shop, looks like you are kinda winging it in the tool department.

That looks great. Are you for hire?

LOL...

The traps definitely helped. I just re-calibrated things and one notable difference was that I had to lower the sub's volume control knob 25%. The 3808 had it as low as it could go (-12 db), but the LFE was still 8 - 10 db too high.

Bass in general seams tighter and more enveloping. Even my 15 year old son commented that bass sounds louder and he normally doesn’t notice things like that.

I have also found a new appreciation for just how well the QS8’s perform. With the M3 surround backs disconnected and just running 5.1, I’m doubting the need, or even felling much desire to go back to 7.1.

Chalk another one up to the "Bass Traps and Acoustic Panels" do make a difference club.

Excellent Mike! Your wood working and craftsmanship skills never cease to amaze me, and you always talk as if you just throw that stuff together in short order.

As most around here know I really don't get too overly involved with the graphing, acoustic treatments and such but I do use bass traps and do know that they really improved the bass in our particular room, I'm glad you too are having the same results ... plus, to me, they just freaking look neat as hell.

Anytime somebody sees our room for the first time they always ask about the huge speakers in the front corners of the room, I get a kick out of that.

I notice you also use white plates for your outlets on the front wall, I did also but after a while they became somewhat distracting so I painted the plates the same color of the front wall (red in our case, front wall only) and found that I really like them blending with the wall. The remainder of the room are still white plates.

Way to go big guy, that really came out first class!

Nice job on the traps. The right tools make a big difference in how easy it is to do even small projects.

You don't do anything half-assed, do you? Those look great! Thanks for taking the time to document your build process.

Beautiful job Mike! I also considered using small stands to lift my corner traps above the base boards but I have yet to make anything.

Screw how they sound. Shouldn't this be in the "Got Wood?" thread under "really, really great work"?

What are you trying to say Mark, my Play-set-Of-Death® is not, in fact, the greatest wood work you have seen? I'm hurt.

Is the "I'm hurt" directed at Mark or your abomination creation?

Lol, "Play-set-of-Death" reminds me of that Japanese show(forget the name), where contestants run across the obstacles and get knocked flying into the moat!

Well, I have a permanent scar on my calf from dropping a huge drill with an auger bit, tip first of course, during construction. Does that count?


Not far from accurate in design or implementation. Half the goal was to give some confidence on challenges, so it has its fair share of game show attributes. Swing on the trapeze the wrong way, and you will slam into a 6x6 post. Don't go down the fire pole the right way, you will pay with skin. Trust that those rocks on the rock wall will hold you - well that one is probably a lawsuit waiting to happen. I should address that.

I was trying to find out the name of that Japenese game show and found this one instead. WARNING: maybe very painfull to watch.

My swing DOES NOT have that. ouch.

I think the show was called Takeshi's Castle or something like that.

Right you are, Jay. Just looked it up on U-toob.

Beautiful work, Mike! Any questions about bass traps I get I'll just refer them to this thread and your construction details.

Regards,

Alan

"Female creatures"... that's funny stuff right there! lol!