Axiom Home Page Forums General Discussion Technical Questions My 2nd attempt at graphing my room response?

Ok, I know I had another RealTraps post below, I'm hoping I can keep this one on topic. I'm looking for any advice on my results.

Before I ran the test today, I reset my Denon 2805 and ran the AVR's auto setup with microphone. Below are the results from the Denon setup:

M60s L/R were set to "Large"
VP150 was set to "Large"
Sub "Yes"
All 4 Qs8's set to "Small"
80hz crossover LFE+Main

Delay(dist.)
FL and FR 13ft
Center 12.6
Sub 27.3ft
SL 8ft
SR 8.6ft
SBL 7.3ft
SBR 7.3ft

Levels and SPL meter measurement
FL +8dB 78dB
FR +7dB 77dB
C +5.5dB 77dB
SR +9dB 78dB
SBR +7.5dB 78dB
SBL +7.5dB 78dB
SL +6.5dB 78dB
Subwoofer -6dB 78dB

So, I was pretty happy with the Auto Setup results, however, I did make the following changes:

L/R M60's changed them to "Small"
Center VP150 changed it to "Small"
Questioned the Sub delay of 27.3ft (normal per manual)
I manually adjusted all the speakers to 78dB's.

Also, I had previously performed the Subwoofer crawl, and determined the EP500 sounded better dead center below my screen, below my VP150 center. I mounted the VP150 up higher on the wall, so there is about 6 inches of space between that and the EP500. It looks cool anyway. I know most of you said the left corner would be better as it would be further from the opening into the larger room. We'll see, I may put it back in the corner.

Below is the first graph I did with RealTraps. The CD comes with a pink noise track and your supposed to adjust the volume to 70dB's for the test, however, I actually tried it at about 78dB's. Must explain why the overall graph is higher on the chart compared to my second attempt below.

Also, the EP500 was placed near the left corner during this first graph. This may explain the change in some of the dips in the second graph, as I moved the EP500 to the center of the wall below the screen. The microphone was placed on a tripod in the primary listening position.



The graph below is my second attempt today. I adjusted the main volume to 70dB's per the RealTraps instructions. Also, the EP500 is in the center of the screen back wall below the VP150. Don't have a picture of that yet.

Here is my second graph from today. Overall it has the same pattern ups/downs as the first graph. I am concerned about the low dips at around 50hz, 150hz, and 260hz...



Here are a few pictures of the room to give you an idea of what the room looks like. Sorry the pictures aren't the best. The overall room is about 30ft x 30ft with 9ft ceilings. As you can see the Theater area where the speakers sit is set back 6 feet from the main room to make it more private. I'm sure most of my problem stems from the large open room.

Any advice is appreciated from the experts. Overall my sound is great, so maybe I should just enjoy and stop worrying.

Well, Randy, about the only comment on the graphs is that the peak around 38Hz and smaller one around 57Hz appears to be the room mode relative to the 30' dimension. It also appears that the mode wasn't significantly affected by the changed sub position, and if anything the second graph appears to be a bit worse overall.

Possibly, as you inferred, the advice for you and Mark Johnson(he of the room that sucks)should be to add watching the making of room effects to making sausage and laws as being things better off left unseen.

John, I think you are absolutely right. It is a formula for depression--unless you've got an unlimited budget and completely free rein in the design and furnishing of the room.

Very good, Sean; and I certainly appreciate the confidence you showed in me by being willing to persevere through the agony of five readings!

That was frighteningly close to my thought process!

Yup, i'm onboard with this one too.
Sometimes you just have to sit, sigh, think to yourself "ah crap on a stick", and give in to what you've got.

Lovely graphs though.

Ok Ok. I made a few changes after reading many online articles regarding sub placement. For now I've moved my m60's as close togethor as possible, not to interfere with the 10ft wide screen.

The EP500 is now in the far left corner about 6" From the left wall and 8" from the back wall. The m60's are about 6" from the back wall and exactly the same distance from the left/right walls. Right now they are not toed in at all.

My wife likes country a lot, ok I like it also depending on what we are listening to...Right now we have some Alan Jackson cranked up pretty loud. It sounds unbelievable.

Before that we listened to a Classical CD we bought for our kids when they were babies, "Build you baby's brain". Mozart, Beethovan, Handel, Schubert, Vivaldi, Bach, and others are included on the CD.

I think I have these Axioms imaging fabulous right now.

ps: I might try one more graph to see if there are any improvements.

Randy, If you set the M60's to large instead of small, without looking at the graph, what is the difference in the sound? If they are your main speakers, excluding the sub-woofer, wouldn't you want them to be set to large?

Yes, if I was not using a sub, your correct, my 60's would be receiving the full frequency range. However, since I have a sub in the equation, and watch movies 7.1 and music, setting all speakers to small, with an 80hz crossover has given me the best overall blend for both situations. Keep in mine, "small" has nothing to do with the size of the speaker. It is related to the ability of each speaker to play freq's below the crossover setting. Yes, the 60's can go lower than 80hz, but even at 80hz, the 60's still pump out potent bass. I have tried "Large" and LFE+Main on the receiver, but think it sounds better this way. The sub is playing all the non-directional effects as it should.

Randy, Dude, Buddy, Pal...

Unless you really enjoy measuring SPL and building graphs more than you enjoy listening to music and watching movies, I'd say you're barking up the wrong tree

Tom-
You're placating him!

Seriously: Randy, you know that I, possessor of thy room that seriously sucketh, can sympathize. And I have come to believe that at some point, you need to make a decision as to whether or not you want to completely re-do a room with acoustic treatments or just learn to let it go and enjoy your system.

But you other guys need to realize that it truly IS frustrating to have really bad graphs. It's very hard to shake the nagging suspicion that others really ARE enjoying their systems more than you can in your situation.

You guys know I love analogies:

Imagine that you bought this great dream car… let's call it the Porsche M80. And you spend time on all these forums with other Porsche M80 owners describing how they can feel the texture of the road because it handles so well, and when the situation warrants it, they can floor it and just "fly" with the 300 horses under the hood. Only in the county you live in, the weird new county administrator (we'll call him Ohm) has managed to get a new law passed that restricts all cars' horsepower by 30%.

You can still enjoy your Porsche M80 to some degree, but you just know that you're not experiencing it the way others are and that there's something missing.

And the only way to get full use out of it is to make some drastic change….like hunting down and killing the town administrator and setting him up in a sleazy hotel with props that make it look like he was robbed and killed by a hooker on a four day crack binge, but then of course, you have to find a hooker that frequents the motel and kill her too, taking evidence off her to plant in the motel room to connect her with the other murder. Better: The town administrator's car needs to be given to the hooker's pimp with the murder weapon under the back seat to setup a scenario of the pimp killing them both over a payment dispute. Or…. Was she an informant to the administrator? Oh yeah. Don't forget to steal her cell phone the day before and make two calls to the county administrator's office to get him to the motel. That will set up the link between them.

See how hard it is to get good sound in a room that sucks?

Thanks Mark and Tom,

I totally agree with your comments. This stuff can drive you nuts. Funny thing, the sound is great. Imaging is unbelievable. It can't get any better, can it? I'm must weird like that, I like to play with settings and try to get the best possible results.

I used to drive my friends nuts when I was a kid playing Intellivision. I always adjusted the color, contrast, brightness, sharpness, etc. on the tv trying to get the best picture.

Anyway, last night I moved the sub back to the left corner. This time I placed it to the left side of my left m60, instead of how it is above in the picture. I move the m60's as close as possible without blocking the 10ft wide screen. Re-Calibrated of course:) Things are great right now.

One of my favorite LFE movie scenes is during Finding Nemo when they are inside the whale and the whale is gowwwwwwling, telling them to let go, it will be alright.

Man oh Man, when that EP500 kicked in, the hairs on my leg stood up, the whole room felt like it was lifting off the foundation.

Mark, you're scaring me.

John, here is the post for the PM you sent me.

Any advice would be appreciated..Randy

OK, let's see...

I took the two graphs and overlaid them in Paint, sliding the second one up several dB so the average levels matched. I haven't figured out a good way to change the dot colour in one graph so I can tell the curves apart more easily, but at least this gives an idea of what behavior is common and what is influenced by moving things around.

JohnK is spot on as usual about the peaks -- 30 feet gives you peaks around 19, 38, 57, 76, 95 and so on -- and the peaks are almost unchanged between the graphs, which makes sense. The 38 hz peak is almost 10 dB high, which might be noticeable -- having the EP500 ~7 feet from a wall might take that down a bit.

You have major suckout around 150 Hz, which might be an artifact of having the fronts of the M60s 2 feet from the back wall. You should be able to move that dip down by pulling the speakers further from the wall, but there aren't any convenient peaks to knock out that way. You could probably pull the 60s out another 2 feet and knock down the 75-80 Hz bump a bit if you had room.

It's possible that some absorbent material behind the 60s could help if you had something which worked at those frequencies (I'll look around). Maybe Mark's fat-ass dog.

There is also a dip around 250 Hz, which I'm guessing is the crossover frequency between woofs and mid on the 60s. I vaguely remember Ian or Alan telling us that moving the microphone up or down an inch in the anechoic chamber has a huge effect on the response around crossover frequencies, ie don't worry about it because it all averages out courtesy of room reflections.

One of the graphs steps up a few dB below 120 Hz, while the other steps up more like 80 or 90 Hz. I'm hoping the graph with the speakers set to large is the one which steps up at 120 [EDIT, I just confirmed that]. If so, then (a) your sub is set a few dB hotter than the mains, and (b) setting the speakers to "large" gives you a range of frequencies where both EP500 and M60s are active, so you get an extra few dB between 80 (where the 60s step down a couple of dB) and 120 (presumably where the EP500 crossover has pretty much zeroed the output).

Bottom line is that both are pretty good graphs. If you had a long sub cable, I would try the EP500 midway between the two positions you tried, ie 7 feet from the side wall, and see if that knocks down the 38 and 76 Hz peaks.

You could take the EP500 down a few dB to get rid of the step up at 80/120 Hz, but what the heck, it's a big boy and can probably handle the extra few dB just fine. [EDIT - I notice you measured the same SPL for sub as for the other speakers, so I'm guessing your meter may be reading a few dB low in the bass. The Radio Shack meter correction table on the SVS site says 2-3 dB through the upper subwoofer range, and 5-7 dB in the 20 to 30 Hz range, so you probably are set a few dB hot even though your graph says you are not. I wouldn't bother taking your subwoofer level down except as an experiment.

Again, this is a nice graph. Enjoy !

It's too bad you can't donate a couple of feet in one direction to Mark, maybe taking your room down to 27x30 or so. That would make your peaks a bit wider and lower, and would do the same for Mark's room -- right now he sorta has a cube full of Axioms ;(

I forgot to ask -- how wide is the "slightly narrower section" where the screen and front speakers are located ?

Looks like run-of-the-mill foam is not going to be effective in the 150 Hz range -- you need something more like a RealTrap (membrane trap) to work in the lower range. Peversely enough, the RealTraps SoffitTrap has an absorbtion peak right where you need it, but it's exactly the wrong shape to stick behind the M60s. Personally I would just temporarily pull the speakers out a foot, run a quick graph to satisfy myself that the 150 Hz suckout moved to the left, and then forget about it and watch some movies

Hi John, thanks for the input, I'll have to read it a few times to try to follow. Sorry about the dot color, for whatever reason, I could not figure out how to change the color in Adobe Photoshop, I would click on a different color, but it would always turn out gray, go figure.

Anyway the theater wall portion is setback 6 feet from the rest of the room, so the short wall on the right side of the screen is about 6 feet. The back wall is 15ft wide and my screen is 10 feet wide, so that leaves me 2.5ft on each side for my m60's. The ceiling is 9ft tall.

I have my m60's pulled out about 8" from the back wall. I guess I want to be careful in pulling them out to far as the the primary (ear) listening position is about 13ft when sitting in the center recliner, I don't think you want all 3 sides of the triagle to be the same, according to Axiom.

During the first graph, as the pictures show, the m60's where about 1ft from the left and right walls, toed in just slightly. The 500 was just a bit to the right of the left m60, so it was about 2.5ft from the left wall (right below the screen edge).

The second graph I had the m60's closer togethor so they are close to the edge of the screen but didn't interfere with the picture from the projector. So I would say they were about 2ft from the left/right walls. The 500 was centered right below the screen, below the VP150. The picture does not show it, but I now have the VP150 mounted on the wall, right below the screen.

I have not done a graph yet with my current 500 position of being in the left corner, about 6" from the left AND back wall. The 60's are still 8" from the back wall and right next to the screen.

I thought about some side treatments for the first reflection points, not sure if that would help any. Jakeman and Royce73 gave me some great DIY links in the other treatments post from BrotherBob. As far as corner traps, I have room on the right side, but since the 500 is in the left corner I would not have room unless I mount the trap above it on the wall? Or, I could move the 500 back to the other side of my left m60, similar to how BrotherBob has his 600 on the other side of his right m80.

I do have a pool table between the theater seating area and the bar now, so I'm sure that will have some effect on the overall room response.

I can't see that it was mentioned here, so I'd just like to point out that the distances from the speakers and the back and side walls should not be the same. A ratio of at least 1 : 1.3 (measured from the front of the cabinet) is generally recommended to prevent wavelength re-enforcement.

Nice room, btw.

-Jon

>>The back wall is 15ft wide

Aha !! That probably helps explain why the 38 Hz peak is the biggest one. I suspect that if you stuck the EP500 in the middle of the wall rather than the left hand side that would take down the 38 Hz peak. At first you would think you had less bass, but after a while you might notice that all the rest of the bass is just as strong, particularly the deepest bass, and it's actually the emphasis around 40 Hz that has been toned down.

This is all in theory, of course. We have to keep telling ourselves that.

>>I guess I want to be careful in pulling them out to far as the the primary (ear) listening position is about 13ft when sitting in the center recliner, I don't think you want all 3 sides of the triagle to be the same, according to Axiom.

Agreed. My dim understanding is that if you make the angle too wide the stereo image "collapses" at some point. I have observed that myself, although I don't fully understand why it happens.

>>I thought about some side treatments for the first reflection points, not sure if that would help any.

If I am visualizing the dimensions properly, you probably don't have a first reflection point on the right hand side. Putting anything absorbent at the first reflection point on the left would probably improve the imaging even more, although it doesn't have to be fancy foam.

>>I do have a pool table between the theater seating area and the bar now, so I'm sure that will have some effect on the overall room response.

Seems to me that you should be able to build a pretty substantial bass trap into the underside of the pool table

Just read this thread for the first time...

Mark, you have not submitted your location to the board, or else I'd look up a forensic psychiatrist in your area and put you on his radar... LOL

Maybe you watch a lot of Law and Order and/or CSI? Time to step back from the dark side, man!

>>Mark, you have not submitted your location to the board, or else I'd look up a forensic psychiatrist in your area and put you on his radar...

You haven't seen Mark's room response curve. I think he is handling the situation extremely well, all things considered

[EDIT] Randy, I'm still trying to decipher the Denon manuals but IIRC you can use the equalizer manually, not just via AutoEQ, although you lose the ability to adjust the center frequencies of each equalizer band. I don't suppose the manual EQ has a band around 38 Hz, does it ? If so, then you might want to try knocking that peak down via manual EQ.

Playing with the room responses (ie moving the EP500 to the center of the back wall) will probably still work better overall but if you are getting tired of moving boxes around the EQ thing would sure require less bending and lifting

JP:
I list my location as Concord, NH. But all of the so-called "professionals" in my area invariably throw their hands up in the air after a session or two!

John:
Someday, I'm going to offer you the $38.12 I have in my wallet right now to help me figure out my room!

>>Randy : The second graph ... The 500 was centered right below the screen, below the VP150.

>>John : I suspect that if you stuck the EP500 in the middle of the wall rather than the left hand side that would take down the 38 Hz peak.

Hmm. Think I missed something. The second graph did have the EP500 in the middle of the back wall. I'm surprised that didn't have more effect on the 38Hz peak -- is there any chance the side wall to the right of the screen is very light construction compared to the rest of the walls ?

Mark -- All I need is beer and free time

Our foundation walls are called "Ice Block". Instead of a traditionally poured foundation, these forms have foam on the inside and outside, and then 8" of concrete is poured in the center voids which are rebar strengthed. These are so much more efficient and many builders are using them.

Anyway, all the exterior walls have the iceblock, except for the walkout area, which is 2x6's. So behind the screen is iceblock with drywall and so is the left wall. The right 6ft wall is framed with 2x4's and has drywall.

I think I will try graphing the room one more time with the sub in the left corner and compare all three graphs. Right now I think I'm getting the best sound I've heard with the 500 in the left corner and the 60's as close as I can get them without interfering with the screen.

By the way, got the pool table all felted and had my first game with my 7 yr old tonight, if he keeps practicing he will be as good as his old man.

Ok folks, I just finished my third graph and am looking for advice/comments compared to my first attempts above. For this test I moved the 500 to the left corner on the left side of the left m60. I ran the realtraps test tones in Direct mode on the receiver with a crossover set at 80hz and mains set to small. The Radio Shack meter was placed in the center lazy boy at ear level, which would simulate my main listening position for music. Thanks in advance for any comments...

Your room sucks.

Oh, wait, that's not really what you're looking for, is it?

to be honest it really sounds good even though it looks bad on the graph. It takes about an hour to graph this out in 1Hz increments from 10 to 300 HZ, fun fun.

Who needs to hear 150 Hz, anyway?

Randy, apparently our rooms sound better to our ears than they do to our microphones.

OK, that was interesting. Some things I might understand, some things I don't even have a good guess about, but maybe JohnK or others can pitch in.

First step was to get some comparison graphs, including shifting graph 1 down by ~7 dB in each case, although I'm not sure that was the right amount. Comparing graph 1 vs graph 2 showed that the low frequencies were very similar, with more differences up around the crossover region.

The more I look at these graphs, the more I am starting to suspect that the second graph did NOT have the EP500 in the middle of the wall at all. Randy, is there ANY chance that both #1 and #2 were measured with the EP500 in the same position and that there is a graph #4 floating around somewhere on your hard drive ?



OK, now let's look at #1 vs. #3, which shows more significant differences. The most obvious difference to my eyes is that the 25-40 Hz range is significantly higher with your current layout. The graph for #3 is even bumpier than for #1 or #2, but you have "narrow dips" rather than "narrow bumps" -- my guess is that the dips are harder to hear and the results more satisfying. This all seems to make sense -- when you put the sub closer to the wall (ie on the outside of the M60 instead of inside) you will get a few dB more reinforcement at the lower frequencies.

What I don't understand so much is that graph #3 steps down above 100 Hz while graph #1 and 2 both step down closer to 120 Hz. My best guess is that this is a cancellation thing having to do with the M60s now being about 2.5 feet from the side wall as well as the back wall, but not really sure.



Comparing #2 and #3 doesn't really have any surprises. The difference between #1 and #2 is much less than the difference between either of those and #3. Again, I really believe the sub must have been in the same spot for #1 and #2.



Anyways, bottom line IMO is that by putting the EP500 close to the wall you were able to bump up the 25-40 Hz range which effectively smoothed out your response. I'm not sure why it didn't make the 38-ish bump higher, only broader, but the results seem pretty good.

Please go and find graph #4, the one that REALLY has the EP500 in the middle of the wall

Ok John, now your starting to make me wonder about myself and what order I've done everything, no wonder my wife thinks I have ADD. Anyway, I went back and read my first thread regarding realtraps back in May.

There is no 4th graph.

OK, the first graph was done with the EP500 to the right side of my left m60 right below the left edge of the screen, similar to what the pictures show. The m60's were a little closer to the left/right walls at the time.

After I ran that first graph, I then did the sub crawl by placing the EP500 in my center recliner and played some boss bass tracks. At the time I felt the best position was dead nuts in the center of the wall below the screen. So, I mounted my VP150 up on the wall just below the screen, and then put the EP500 below the center channel speaker with about 6" of space between them.

For the second graph, the EP 500 WAS in the middle of the back wall. I also moved the m60's as close as I could, but not interfering with the screen viewing.

One other note, the realtraps cd comes with a pink noise track. Your supposed to adjust your main volume to 70dB while watching your spl meter. During the 1st graph I had it at 78dB by mistake as I didnt' read the instuctions. For the second graph I did use the 70dB reading, I'm sure that is why the overall graph 1 is higher in relation to graph 2.

Now for graph 3, the m60's have not moved, but the EP500 is on the left side of the left m60.

Also, I'm fairly certain I had my m60's set to small and a 80hz crossover for all of the graphs. I can't remember for sure, but there is a very very slight chance I might have had Large and LFE+main for graph 1. I just can't remember 100%.

Overall, it appears graph 1 has the best overall results, so I may have to move the 500 back on the right side of the m60 further along the back wall, but not all the way to the middle. hmmmmm

>>Ok John, now your starting to make me wonder about myself and what order I've done everything, no wonder my wife thinks I have ADD.

>>There is no 4th graph.

Hmph. Maybe I should be talking to your wife.

Seriously, it's just hard to believe that graphs #1 and #2 have the sub in such totally different positions. They *really* look like almost the same graph.

Oh well... good thing this is a hobby

In the two graphs, the sub would have only been moved about 4.5ft.

Y'know, I was just looking at the 1 vs 2 graph and thinking "if the sub had been more like 5.5 feet from the wall, not 7.5 (middle), that would explain why we're seeing a dip at 50 rather than taking down the 38 hz peak a bit".

Do those dimensions fit ? I'm not completely hopeful because the centerline of the sub was probably a couple of feet from the wall already to leave room for the M60...

If the sub might have been 5.5-ish feet from the wall in graph #2, however, any chance you could try with the centerline of the sub about 7 feet from the left side wall ? I assume that's the "Ice Block" wall not the one on the right ?

Note that the calculated distance is about 7.5 feet (1130 / 38 / 4) to give a quarter wavelength at 38 Hz -- I subtracted 6 inches or so for the ICF foam and your wall framing etc...

[EDIT] Hold on -- graph #3 has that 50 Hz dip as well. I don't understand that at all... Randy, hold off on moving the sub until we figure this one out.

JohnK, any idea where the 50 Hz dip is coming from ? It's a bit dramatic to just be "the hole between the 38 and 57 Hz peaks" but maybe with the sub against the wall the effect of the peaks is being accentuated that much.

If so... "mmmm, bass traps" says Homer.

I guess I'm not sure when I measure how far a sub is from a back/side wall, if I measure from the front of the sub. When you say centerline, are you saying where the horizontal and vertical lines cross on the front of the sub?

The back wall is 15ft wide. The screen is 10ft wide and is centered dead nuts in the middle. This gives me 2.5ft left over on the right/left sides.

So, in graph 1, the sub was right below the left side of the screen. The left side of the cabinet on the sub was lined up with the left side of the screen.

In graph 2, I moved the sub exactly in the middle of the back wall, so if your measuring from the center of the driver, it would be 7.5 ft from the left/right walls.

In both cases, there was about 6-8" of room behind the sub cabinet to the back wall.

In regards to the ICF forms, the back wall and left side wall would have this product behind the drywall.

Another thing I'm sure you saw in the pictures, is that I have a stage built below the speakers. It is built out of 2x8's and the top is covered with padding/carpeting.

Your correct about the 50hz dip, but if you look at graph 1, it does not appear to be as severe as 2,3 when looking at the other frequencies around it...

Well, Randy and John, the wavelength at 50Hz is about 23', so if the dip is a result of boundary interference effects this would call for a quarter-wavelength distance of about 6' to some surface to be causing a problem(yes, the distance is from the center of the subwoofer cone, not from any part of the enclosure).

Yeah, that's what is baffling us. We can't FIND that 6' distance, unless Randy is a big guy like me and was standing in front of the subwoofer holding a pool table while watching the meter