Axiom Home Page Forums General Discussion Advice from Axiom Owners My Superchunk Bass Trap Project, Graphs included

As most of you know, I've gone graph crazy. Not sure what it is, but there is something that is interesting about improving your room response and overall sound.

Before I get started, I want to thank "Bridgman" for helping me become an Excel expert on graph plotting.

Ok, so I've been spending some time lately on various websites reading about the topic of improving your room response by using a combination of bass traps and mid-high treatments. Many believe this type of setup is mainly for recording studios, when in fact the same rules apply to a HT environment. There are tons of great websites out there on this subject. Audioholics even has some great articles on bass traps and acoustic treatments. Another great starting point is http://www.ethanwiner.com/acoustics.html or reading some of the other articles by Ethan's company at www.realtraps.com.

I decided to take the DIY route as usual to save a buck. What I really appreciate about people like Ethan from RealTraps, Bryan from SensibleSoundSolutions, and Glen from GIK Acoustics, is that they were willing to give me advice on building my own treatments using some of the same materials they use, versus trying to talk me into buying from them.

Based on my research I decided to purchase some Owens Corning 703 Rigid Fiberglass board from a local insulation distributor. This is a popular product that has been proven to have great absorption properties when installed correctly. Many people use foam products, but if you look at the stats, they just can't compare to Rigid Fiberglass board, Mineral Wool board, or cotton. The 703 I purchased came in 2' x 4' x 2" thick sheets. Many people will double these up and straddle a corner which provides good results for bass trapping, just ask Royce73. However, an even better method is to use superchunks, which basically are triangles that fill the entire void in the corner.

The OC 703 is very easy to cut. Just make sure you have some gloves on as it can make you itch, just like regular fiberglass. For starters you cut the 2' x 4' piece in half. This gives you two 2' x 2' pieces. You then cut these each diagonally to make triangles which are 24" x 24" x 34". Many people use this size for their corner chunks, however, I decided to make another cut to those pieces which gave me 17" x 17" x 24". This size worked better next to my screen and gave me room for my m60's.

Here is a picture of some of the precut OC703.


Once they are all cut, you basically stack them in the corner. I built a frame out of some 1 x 2 pine, and used general purpose velcro to attach the black felt I purchased at Walmart.









For low bass frequencies the material is not as important as it is for higher frequencies. With the higher frequencies you don't want a material that will reflect the sound. A good test is if you can see some light passing through or if you can feel your breath through the material you'll be fine. Muslin is another material often used.


Anyway, I know Bridgman told me not to worry about graphs, but I could not help myself. I didn't figure I would see much improvement just by adding two rear wall bass traps. In reality, it is best to have all your corners treated with some form of bass trap, this can include corners where ceilings meet walls also. I would then move onto treating some of the first reflection points with mid-high frequency traps. But one thing at a time.


Sooooooo without further ado.....Here is my most recent graph. In both situations I used the Real Traps test tone CD which covers from 10hz upto 300hz in 1hz increments. The master volume was set at 70dB's per the instructions. Prior to the tests all my speakers were calibrated for SPL, Delay, and dB levels using the Denon built in mic and setup. In addition, I verified the dB levels with my SPL meter prior to starting. M60's were set to small with a crossover of 80hZ.



Overall, I feel there is some good improvement if you compare the before/after plots across the entire graph. You can see the severe dips I had around 145hz and 235hz have improved. In addition some of the higher peaks around 40hz, 55hz, and 80hz, have been reduced slightly.

The most important thing that really suprised me is the sound has improved just with two rear traps. I've been listening to a variety of cd's in my collection and I am being 100% honest that I truely hear a positive difference. The bass is much tighter and individual notes are clearer and easier to hear versus the "one note bass" that some experience, especially in the lower range.

Sorry this has been such a long post, I hope some of you can provide some positive feedback for me.

Thanks for listening, Randy

Wow -- those are mighty impressive looking bass traps, and they really seem to disappear once you get the frame and grill installed. VERY nice. I'm tempted to load up the back of the Magnum with OC 703 sheets, grab a sharp knife and head over to MarkSJohnson's house.

Just a quick thought -- we look real hard at the +/-3 dB frequency response specs for speakers, ie 6 dB deviation within the listening range. Very roughly, those traps took the deviation from 42 dB (!!!) down to 26 dB. The big bass peaks came down by 5-7 dB, and in most of the other frequencies the excursions were down by a few dB.

Very interesting results. Conventional wisdom is that you need a lot more traps, but those are BIG honkin' traps. Thanks very much for taking the measurements and posting so much good information.

Randy my observation is that the significant improvement appears around 140-150Hz, but the total variation around 220-250Hz seems the same or a bit greater. Maybe just that upper bass area improvement does make an audible difference.

Very professional looking job, Randy! I am glad to hear that you are pleased with the outcome as well. Keep us informed if you decide to add more traps.

Thanks guys for looking at my results. One question I have is in regards to toe in of the main speakers. Most of the acoustic websites say the best place in a room is to be 38% back from the front wall, if this is not available, 38% from the rear wall is a good second choice. By default, these locations have the least amount of modes present and a good starting point, before bass traps.

38% back from my front wall is almost 12ft. My m60's are a tad over 10ft apart. If I have the m60's aiming just slightly behind the main seating position they are toed in very much. I wonder if this excessive toe in is not a good thing and may alter the graph above? I've read you should have an equilateral triangle to the primary position, but how is this possible if the speakers are not toed in somewhat?

Looking good, SirQ!!

Glad to see that can tell the difference like I have. It is nice to know that it just wasn't my mind playing tricks on me. I got the day off work today and the nanny is here, so your post was has inspired me to post my RealTraps Graph as well. Once you get the time, I am sure you will see a bit more improvement with the third and fourth chunk traps

I noticed you had a dip around the 140-150 area like I have as well. Anyone have any thoughts as to improving those frequencies?

Here's my first REALTrap measurement done a few weeks ago. I believe I was running my sub too hot.



Here is my room layout as well:


Any expert advice as to how to fix my highlighted problem areas?

Hey Royce, nice graph and drawing. Is the room drawing to scale? To me it appears the side reflection points may be to much into the room. How did you arrive at those locations, using the mirror trick, or the equation on the RealTraps website? If you imagine making a Pool Bank shot off the wall, it does not appear you would hit the speakers. Also, I wonder if it might help if you move the sub a little closer to the corner, not sure? I'm no expert, YET.

My statistics / econometric methods are a bit rusty. I'm wondering what the best way to interpret the data would be from an objective statistical standpoint. I suppose one would want to calculate and compare the standard deviation, variance and the number of outliers (and their magnitude). Oh oh, of course one should always be on guard for "heteroskedaticity".

I'm sure Chess will chime in. He will know.

Cheers,

J

Randy,

No, the room picture is not to scale. The side traps are about two feet away from the end of the corner trap. I used the trusty mirror trick. I did also view it as a "Pool Shot" and the bank shot would hit the side trap in the real room.

I had the sub in the corner for my first measurements. There was a HUGE dip around my crossover point so I moved the sub closer to my sweet spot. The difference was noticable sonically and on the graph, so I decided to use that location. The sub is right up against the side trap like in the diagram, but os only three feet from the corner of the room.

I just finished another reading, this time I moved my CD/DVD shelf to the back wall and the table to the side. The bookshelf should be better for disfussion against the back wall. I will post soon.

Okay, I turned down the volume on the sub as my first graph showed that my lower frequency were charting a bit higher than my mids and highs. Here is the result:

Now compare my two REALTRAP readingds side by side:

Looks like I fixed the dip at the lower frequencies at addressed the big problem between the 220-260 mhz a bit. A definate improvement.

Now, here you guys go again trying to quantify "quality". Did the 1960's teach you nothing?

Nice work, Randy. Really fantastic looking, and it makes good sense to me that you would hear an improvement. I'm jealous of you guys that have dedicated rooms.

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and head over to MarkSJohnson's house

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Now THAT is some funny stuff, right there.

Wow Royce, that seems like a large improvement over the first graph. Amazing how making minor adjustments to the sub gain and/or moving a few items around in the room make such a big difference. Just placing a throw blanket over to top of leather chairs can make a difference. Ethan Winer on realtraps mentioned a table in front of his couch was skewing results, so he just put a nice doily over the top and that tamed the response.

It appears that you have reduced your overal deviation from about 30dB down to 20dB, and the larger bass peaks appear to have dropped by about 5dB's. This is fun stuff.

>>There was a HUGE dip around my crossover point

That is nature's way of saying "fliiip the phaaaaaase switchhhh....". If your sub and mains are out of phase they will cancel at the crossover point and you will get a big dip.

I'm intrigued that the treatments helped with your ~60Hz null. I'm going to be upgrading my treatments soon (just adding more fiberglass in the corners behind existing traps). I've got a 60Hz suckout too. Perhaps I'll see some improvement as well.

Nice job Randy, man those traps look extremely good! I just did get my GIK Tri-Traps in today and due to working late just did get 'em in the corners, wife loves the look and I am enjoying the sound ... a significant difference? Probably not, but man the Axioms are sounding extremely good while playing Joe Bonamassa and the new Los Lonely Boys 'Sacred' CD. Whenever I get the time I'll do a couple of more manual graphs to see if there is a difference there but to my ear everything *seems* to be quite a bit tighter.

Upon searching I have found there must be a million ways and suggestions to *properly* set up the speakers but I did the Rives suggestion of having the mains 1/5 the distance of the room from the front wall which put my 80s 5ft from the front wall and I also put the listening position 38% from the back wall, I had to patiently adjust the toe-in 'till everything just clicked and by George the system is sounding mighty fine. My mains are 11.5 ft apart and the listening position is 13 ft from the mains and center...while listening in 2 ch stereo my son lost a bet over the weekend believing the center channel was playing.

It's amazing just how minute adjustments and tweaking does for the sound, it is fun and the music never sounded better!

I'm not 100% sure, but I think the before and after graphs also included moving the subwoofer from a corner to the side wall.

Again, suckout at crossover can often be fixed with the phase switch -- that's why it's there.

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I suppose one would want to calculate and compare the standard deviation, variance and the number of outliers (and their magnitude). Oh oh, of course one should always be on guard for "heteroskedaticity".

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Now we're talkin!! None of this subjective "hearing" nonsense that everyone keeps talking about.

Actually i think royce has had noticeable improvement towards linearity in his graph by eliminating a huge dip and reducing the magnitude of change in SPL from top to bottom. Whether the increased linearity sounds better is still subjective and obviously difficult to A/B test.

Listen to bridgman, "the phase is all around you, use the phase Luke...use the phase"

So Randy, does this mean you will have to do all these tests over again once you get your M80's

I've got it figured out, your really WID, under a new alias. ha ha

I'd love some 80's but not sure if it will happen for some time. To late to trade up with Axiom, I've owned them to long. Even though mine are like new, it still has been over a year or so... To be honest, the 60's sound awesome.

I thought I would update the above drawing to give you all a better idea of what the room looks like. Keep in mind this is not to scale.

Since I have completed my Superchunk Traps on the front wall, my next plans are to build some column traps to go in the rear corners.

I would also like to put some bass traps where the walls/ceiling meet in the HT area above where I'm thinking about putting some 1st reflection treatments. Also, I eventually might put some 1st reflection on the ceiling locations.

As you can see, there is a 10" bulk head dropped along the entire width of the room, I might be able to put some smaller bass traps up in the corner facing the screen?

What do you all think?



Also, I have a few questions for using 703 for 1st Reflection Treatments:

1) First of all, am I correct in saying I want to leave some space behind the 703 and the wall, within the frame I build?

2) Also, do I want to use the FRK(scrim) on the side facing the room, or use regular 703 with no facing?

3) For those wall/ceiling treatments do most people use 2" thick or double up and use 4" thick 703?

Thanks in advance, Randy

Take all of the following with a LARGE grain of salt...

>>1) First of all, am I correct in saying I want to leave some space behind the 703 and the wall, within the frame I build?

The space helps with bass trapping but I don't think it helps so much with absorbing higher frequencies. There was a chart somewhere with cutoff frequencies vs. thickness of 703-style fiberglass, will see if I can find it.

>>2) Also, do I want to use the FRK(scrim) on the side facing the room, or use regular 703 with no facing?

If you're talking about paper facing, I think that helps with bass trapping but reflects a lot of higher frequencies. For treating first reflections I would say "no facing".

Note that you probably want a ton of absorbtion (sp) on the left wall to balance off the fact that you have no right wall.

>>3) For those wall/ceiling treatments do most people use 2" thick or double up and use 4" thick 703?

I'm pretty sure 2" is enough for higher frequencies -- the question is whether it's worth putting more FG in there and getting more absorbtion in the lower frequencies.
I'm REALLY tempted to pick up that $150 ETF software package from Rives (also needs mic, cables and decent sound card) which indicates decay & resonances at all frequencies. That would shed a lot of light on what the room needed.


One common treatment for mixdown rooms seems to be what they call a "cloud" over the listening position, basically a big chunk of fluffy fiberglass near the ceiling with enough framing to look half-decent. Not sure if you have enough height to keep it out of the projector light cone though...

BTW I don't think bass traps at the bulkhead would be as effective as bass traps at the back wall/ceiling boundary.

Well I just got back from getting some more OC 703 Rigid Fiberglass panels and some 1 x 4's. Hope to start building some FRZ's tomorrow, and eventually some more column bass traps for the rear corners. Gotta consider the Wife Factor.

Just a quick update, I've got 3 of my FRZ (first reflection zone) panels built and installed in the correct locations on the side walls. I still need to hang 2-3 on the ceiling FRZ's as well, and then onto a few more bass traps for ceiling/wall corners and then rear column bass traps for the rear corners of the room.

I can't believe how much better the music sounds, just with the front wall superchunks and FRZs up so far. In the mids/high categories the clarity has improved greatly. I am no longer hearing the same sounds that were reflected off walls and coloring the overall sound. Percussion, Strings, etc...just sound crystal clear. My 60's sound better than I ever thought possible.

Ok, don't break out the tissues. I'll try to get some pictures up within the next week. I just wanted to let you know I'm amazed at what I'm hearing with my cd's....

talk to ya later.

Sounds good Randy, I can't image how good some M80's would sound in your setup

My 60's sound better now than 80's with no bass traps or FRZ treatments.

Great read, thank you for sharing this.

I might of missed it in this thread, but what is your ceiling and floor like? Have you done anything to help reflections/absorptions there?

My current project includes "first reflection" treatments on the side walls and ceiling locations. Then I can move on to finish a few more bass trap locations...

I am a bit worried about my theatre room. If I order M60's, i have a 16 foot long room. I don't think I'll be able to place the speakers 3 feet from the front wall (1/5 distance) because there is a door to the left of the screen and I don't want people running the risk of kicking the speaker or anything when they come into the door.

Is there a minimum distance of placement from the front wall? Ideally 1 foot for me would be best..

I am kinda freaking out about all this acoustic stuff wondering If I screwed myself over when I designed the room before It was drywalled...

My M60's are about 7-8" from my front wall, most people have them closer, 3ft seems to far. I would not worry about the acoustic stuff to much, I didnt' add my treatments until after everything was done either.

Geeze,

thanks for calming my fears. I have no idea whats wrong with me. I spend countless hours each day researching acoustics etc...I feel like I am loosing my mind with all the decisions that have to be made concering a theatre room.

My wife seems to think I am going crazy as well I feel much better that I don't need to be 3ft out! lol.

-Robb.

YOu'll get there, don't worry...

No you don't need to worry about this. Mine are 1 foot from the front wall (the back of the speaker is 1 foot away I mean). I think the 1/5 guideline you are talking about is referring to the front of the speaker anyway. Sure the further away from the walls the better as far as wall reflections, but most of us have these types of limitations.

I am sure they will sound great to you, wherever you need to place them.

Don't get too sucked in by the Golden Measurements thing. Just so you can leave enough space behind the speakers for the ports to breathe, you'll be fine.

It's supposed to be FUN, remember?

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It's supposed to be FUN, remember?

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Ain't that the damn truth.

People with OCD find fun in perfection.

Thankfully I do not have OCD

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>>I spend countless hours each day researching acoustics etc...I feel like I am loosing my mind with all the decisions that have to be made concering a theatre room

>>Thankfully I do not have OCD

That's good to know

hahah...really...i don't...

You guys all know how it was when you first started looking at this home theatre stuff. I want to know everything there is to know before I start purchasing things ya know? There is a wealth of information on the internet, it can get quite overwhelming.

-Robb.

Yeah, it's annoying-you think you've figured it all out and then you realize that you just peeled away another layer of the HT onion. Sure, get your acoustics perfect and your room to a 'magic' size, but then you'll need computer software to calculate exactly where the speakers and couches should be placed to avoid any acoustic anomolies in the listening area.

Oh, and before I started my quest for making a 'WOW' home theater, I had never found something that triggered my latent OCD.

38% back from the front wall is the best 1st choice, followed by 38% from the back wall as a good 2nd choice. 50% is about as bad as being right up to the back wall, however, some people just don't have any options.

>>Oh, and before I started my quest for making a 'WOW' home theater, I had never found something that triggered my latent OCD.

Same here. If Hilary Clinton ends up as President I imagine do-it-yourself home theaters will be banned as a mental health risk.

John, if that happens I will move to Ontario and go to work for Axiom, that is if they would take me. That would be worse then if one of the main 3 automakers ever goes under.

Wanted to show you some recent pictures I have on my website. These include the recent "front reflection zone" panels I've built for the ceilings/walls.

John, I plan to create a page on my website showing the construction of these panels, just have not got around to it yet.

Enjoy.

Very nice looking room, Randy! Wow!

Wow Randy, your theater is really looking awesome buddy! I'll be looking forward to seeing the construction process added to your website. If it's not hard and is cheaper then GIK's panels, I might have to give it a try.

Randy, that *really* worked out well. Ignoring the impact on sound quality (which is probably significant) the treatments sure make the room look good. Congratulations !!

Awsome room man...I am planning on having a drop ceiling in my theatre, otherwise I would be putting those pannels on my ceiling as well!

Your theatre is looking great man!

-Robb.

Randy,

Looks great, dude!

BTW, you planning your own Mega Movie Marathon so that you have to put in a tent to catch few Z's in?

WhatFurrer

I have another question regarding those bass traps.

I have a 14 x 16 room and the back of the room there are no doors anywhere (door is at the front of the room). I am going to be mounting my QS8's on the side walls. I don't have alot of room to work with (16 ft long room) So I was wondering if 1 foot wide bass traps would be as effective? It IS a smaller room after all. I don't want to mount my QS8's more than 1 foot from the back wall due to seating restraints.

Will 1ft wide mini bass traps be effective?

-Robb.

Looking mighty darn fine and dandy Randy ... actually darned awesome, I love the look and I'm betting the sound is just as awesome to boot!


I just ordered some panels and a couple more tri-traps from GIK this morning, man I've retired my hammer and nail apron after these last couple of years slaving on our house. Can't do the DIY at the moment.

Ok, since John Bridgman has been begging like a little puppy wanting a bone, for me to show the construction steps of my DIY FRZ panels, here we go...

First of all I would like to thank our fellow Axiom member "mrnomas" from audioholics as I used his DIY instructions to get me motivated.

http://www.audioholics.com/techtips/roomacoustics/DIYabsorbersacoustics.php


Keep in mind, these panels below are for FRZ's (first refection zones) not bass trapping. Although, they do absorb some low frequencies, the 2" thick material is more geared towards mid/high absorbtion. Treating FRZ's has dramatically improved the clarity of the music and pretty muched zapped any echo of the same signals reaching your ears at the same time.

OK, before I get started, I want you to realize that my wife noticed I was working on top of my recently re-felted pool table. Since I had many tools, including scissors, she thought I better place something on the pooltable. So that explains the tiger blanket underneath on the pictures.

This first picture shows the owens corning 703 rigid fiberglass board next to the frames I built. I just went to Menards and got the cheapest/straightest 1x4's I could find. Now that they are all finished, next time I might have spent a little more money to get the better quality boards, as a few of mine ended up being slightly warped.

Luckily, I used those on the ceiling locations, which are hanging down a few inches using wires/hooks. You can't really tell they are warped. The wall panels were perfectly straight, so I just hung them using some picture wire/hooks, etc...



I pretty much cut the longer boards exactly 4ft, and one of the end boards exactly 2ft + the thickness of the boards. I then went ahead and pre-drilled and screwed them togethor, around the panel. The final 2ft piece I cut just slightly shorter, to help hold the 703 in place. I then added a board across the back for extra support, but I don't think it was required.



The OC 703 is a great product to work with. For the most part, as long as it is not disturbed, the fiberglass particles will stay in tact. However, most people like to cover it with white batting or muslin cloth. I used white muslin from Walmart. I precut the pieces, and then used a putty knife to tuck the material nicely around the 703.





Once, I had the white muslin on the front/back of the panels, it was time to attach the black material around the front of the panel. I found some black polyester material at Walmart that had some stretch to it, and one side looked almost like speaker grill cloth.

The key here is you don't want a material that will reflect the mid/highs. Bass will pass pretty much through anything, but mids/highs can easily be reflected if you use the wrong material. If you can breath/blow through the material easily then you should be fine. Just don't use something shinny or reflective looking.

Here is a picture of the material that I precut laying under the panel. I made sure that I took the stretch into consideration before cutting the material. Next, I started on one side and stapled 4-6 staples about 2" apart. I also doubled up the edge of the material for extra support.

I then moved to the opposite side and repeated the process, then the ends, etc.. As I moved around the frame and pulled the material to staple, the front side became nice and flat and tight.



Here is a picture of how it looks once all stapled. The hardest part was figuring out how to make the corners look nice. After a few attempts, it was pretty simple. Basically, I had to trim a little excess material off, tuck one side under the other side, then take the outer piece and pull it around the back and staple.




If you scroll above a few posts, you will see some pictures I posted yesterday of the finished products in my HT. My next step is to build some more BASS traps for the ceiling/wall locations and then some rear wall columns.

ps: Bridgman, yes I will have some graphs asap.

Incredible work Randy. I really admire the ability to research, build, install and get it past the "significant-other" when it comes to puting audio enhancements in your living space. The negotiations can be the hard part!

Randy, nice job!

What did you use to hang the panels from the ceiling, eye hooks? How difficult was it to hang them (getting them tight up there and seeing what you are doing)?

Your room really looks nice and I'm sure sounds as good or better than it looks

I can't believe the sound Dave, before it was awesome as you would expect from Axiom, but it really is much better. I can distinguish the vocals/instruments on the various stage locations now.

In regards to the panels on the ceiling, I used hooks in the ceiling similar to what you would use to hang a plant. I placed eye hooks at each end of the back of the framing and used picture frame wire at each end of the panels with a little slack in them, so they hung a few inches below the ceiling.

Good job Randy. They look very well done. And your theater is to be admired (envied). Watch how many people will now enter your theater and point at the treatments and say, "Are those speakers?" completely ignoring the actual speakers in the room.

It has already happened. My wife thinks I should rename the theater to the Monolith Theater from 2001 A Space Odyssey.

I've said it before, I'll say it again.

Party at Randy's House!

Looks great, buddy. Very inspiring.

Ok, some more graphs. I was going to combine everything into one graph as I did earlier in this thread, but it was getting hard to distinguish between each one. So, here are three graphs: no treatments, front wall superchunks, and supers with ceiling/side wall first reflection panels.

I'm a little confused why it appears my lower bass numbers seemed to improve in the second graph, but have risen slightly in the third graph. I have toed in my mains a little more, and it is possible my sub dB might have been bumped up a dB or so in calibration, not sure.

Anyway, it does appear the higher bass frequencies have improved even more since adding my 6 first reflection panels.

Can I try to talk you into combining the graphs anyways, maybe with different colours for each situation ? I'm trying to look at them together but it's kinda hard on the eyes

John, I can combine onto one graph tonight when I get home. The first graph earlier in the thread comparing "no treatments" to "superchunks" looked good with Red and Blue, but when I tried to throw a 3rd color in the equation the lines intersected and it was hard to make them out. Maybe if I change the X/Y settings to make is easier to read, I'll see what I can do...

Yeah, it gets kinda busy with all three datasets on the same graph...



(The "Darken" blending mode and the "Replace Color" feature in Photoshop make quick work of superimposing charts of the same scale )

From what I can see, your most recent tweaks result in the best curve. The dip at 145Hz has been brought up by 8dB. The dips at 175Hz abd 196Hz have also been greatly improved. The unfortunate part is that the treatments don't seem to be doing much for your peaks.

Thanks Peter,

For those peaks, other than the superchunks in the front corner, I have done nothing else for bass trapping. The first reflection panels are more geared for mid/hi freq's. I still have plans to incorporate more bass traps to handle the lower frequencies.

I do like the improvements from about 160 and higher, represented by the red line in your masterpiece.

OK, here is my combined graph. What do you think?

>>> What do you think?

Patriotic!

That 35-40 Hz range sure took a swing in the opposite direction...why would that happen?

Ya got me Rick? I was pretty pleased to see the improvements in those lower numbers after just adding the front superchunks. Seems now that it is similar to my original readings. There is good improvement in the higher frequencies.

I think my sub placement may be not ideal, and I've always struggled to understand where to put the 500. Also, I think I had it running a bit hot, again, not sure where it should be when calibrating with SPL meters. I usually put everything at 75dB using the test tones on the AVR.

Is there any chance you have a bunch of things "two feet from the wall", specifically the M60s ? Only guessing, but the dip around 140-150 Hz corresponds to cancellation from being "just under two feet" from a wall.

I don't really know where to start, other than to say that it's probably mains rather than sub at that frequency, and that measuring from the fronts of the mains is probably the right thing to do.

Well Randy, I'm suitably dizzy from looking at all the response curves and trying to equate the four or so different room effects with them. The most prominent features are still the dips around 140-150Hz(wavelength about 8') and 240-250Hz(wavelength about 5'). At those frequencies the sub shouldn't have a significant cancellation effect on the mains, so the likely problem is main driver cone to room surface distance of about .25 to .30 wavelength. Following up on John B.'s reply, it appears that your M60 cone centers are about 7"+15"+4"=26" from the wall behind, so that would fall into the quarter-wavelength area around 140Hz. It might be interesting to see if moving them out at least a foot farther had a significant effect on the frequency of the lower dip. As to the higher frequency dip, possibly the floor? Get rid of it!

Of some interest relating to the alternative(or realistically, complementary)electronic room equalization process is the article by Mark Sanfilipo in Audioholics. This appears to be by far the most thorough analysis(the math doesn't necessarily have to be studied)of the Audyssey system used in some Denons and Onkyos, and explains some of the difficulties in getting good results. The graphs are interesting.

Thanks Johns

Well if you look at the white line, you can see there has been some improvement in those 140hz and 240hz dips.

The 145hz dip has gone from 52dB to 56dB to now 60dB, so an overall improvement of 8dB from when I had no treatments.

The 240ish hz dip has gone from 53dB to 63dB to 70dB which is a great improvement.

And the 250hz dip which started showing up after I added Superchunks, is now at about 70dB as well.

To me the overall results from about 160hz to 300hz have improved a lot and are much narrower than the two previous results, everything contained within about 12dB.

On the lower end, I think I need to work on my sub placement and calibration. I had my crossover on 80hz, so the mains would not have contributed to the results getting worse after my second graph, which showed much improvement in the 40hz and 55hz peaks.

You can see from my picture where I have the speakers. I already have the panels in place for first reflections, so I really don't want to move the mains much as they are imaging great. However, the sub can be moved. Also, I still have some more 703 to finish some more corner bass traps, which should help on the low end.

Wait wait wait...

You've spent how much time and money on that (gorgeous) setup but you won't entertain the notion of moving the mains?

Don't MAKE me come over there....

Do you actually listen to any music anymore, or just make graphs?

My favourite way to encounter nuts is in a chocolate chip cookie.

Randy, I've learned a lot from you. Thank you very much for documenting your adventures.

Thanks Tom.

Prior to starting down the venture of treatments, my mains/sub have been placed in a variety of locations. Keep in mind, I am limited as I can't go in front of the screen, and the stage is only so deep. Right now the sound is amazing compared to no treatments, everything is much clearer and better clarity. I know some people think this is another "snake oil" topic, but I am not one of them, my ears tell me that much. There is also plenty of research to back treating a HT/Recording room properly.

I hate when I encounter a raison in a chocolate chip cookie, even though I like raisons, it just ain't right.

Quote:

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NERRRRRRDS!!!

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Lost it laughing ...good one man!

Sorry, we're saying "move the mains temporarily so we can confirm their placement is the cause of your 145 Hz dip", not "move the mains and invalidate all of the other work you have done".

There are other options for fixing the dips, but you need to know the cause first.

I share your sense of horror at the idea of mucking everything up again and having to start over

Thanks John,

I'm sure things will improve more if I ever get more bass traps. In reality, I should have completed them first, and then worried about first reflections later. Oh well, I guess that is why my wife thinks I have A.D.D.

Who is "we"? Are we amused?

John, if rearranging Randy's room "horrifies" you, I think you need to see more and larger spiders.

Really, Randy, I'd just start over. John's just shining you on. You'll NEVER be able to tame those two enormous frequency chasms in that room, no matter what you try. And - now that you have quantified the defects - you'll never be able to REALLY enjoy it anyway. I mean seriously, aren't you going to be constantly listening for those giant suck-outs at 145 and 240 Hz? I certainly would be.

You know the family and I were planning on a big visit to Iowa next spring to spend time with you, but since I am SO susceptible to discrepancies in the 120-150Hz range and you are obviously unwilling and/or unable to actually show some sensitivity to my plight, I think we better just call the whole thing off.

Pity.

"Enjoy the music, not the big, oddly-shaped black things"

You know your welcome anytime I can talk my wife into it. ha ha

I'm sure the kids and wifes would get along great while you and I run down to a few pubs.

Don't worry, I'll have that freq response as flat as Colorado by the time you show up.

>>You know the family and I were planning on a big visit to Iowa next spring to spend time with you, but since I am SO susceptible to discrepancies in the 120-150Hz range and you are obviously unwilling and/or unable to actually show some sensitivity to my plight, I think we better just call the whole thing off.

Speaking of "are we amused", you just made me blow tequila out my nose. I hope you are happy

Seriously, I don't think this is so bad. All kinds of high quality audio systems <Bose> have big dips in this frequency range and people are really happy with them...