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#141420 - 07/06/06 06:57 PM Re: My 2nd attempt at graphing my room response? [Re: SirQuack]
Ken.C Offline
shareholder in the making

Registered: 05/03/03
Posts: 17768
Loc: NoVA
Your room sucks.

Oh, wait, that's not really what you're looking for, is it?
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#141421 - 07/06/06 07:04 PM Re: My 2nd attempt at graphing my room response? [Re: Ken.C]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13333
Loc: Iowa
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.
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#141422 - 07/06/06 10:56 PM Re: My 2nd attempt at graphing my room response? [Re: SirQuack]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16273
Loc: Leesburg, Virginia
Who needs to hear 150 Hz, anyway?
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#141423 - 07/06/06 11:14 PM Re: My 2nd attempt at graphing my room response? [Re: SirQuack]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10385
Randy, apparently our rooms sound better to our ears than they do to our microphones.
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#141424 - 07/07/06 12:06 AM Re: My 2nd attempt at graphing my room response? [Re: SirQuack]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5382
Loc: Bowmanville, Ontario, Canada
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

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#141425 - 07/07/06 12:59 AM Re: My 2nd attempt at graphing my room response? [Re: bridgman]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13333
Loc: Iowa
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
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#141426 - 07/07/06 01:08 AM Re: My 2nd attempt at graphing my room response? [Re: SirQuack]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5382
Loc: Bowmanville, Ontario, Canada
>>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


Edited by bridgman (07/07/06 01:13 AM)

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#141427 - 07/07/06 09:20 AM Re: My 2nd attempt at graphing my room response? [Re: bridgman]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13333
Loc: Iowa
In the two graphs, the sub would have only been moved about 4.5ft.
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M22-OWM22-VP100-Denon2805
Audio Nirvana

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#141428 - 07/07/06 09:32 AM Re: My 2nd attempt at graphing my room response? [Re: SirQuack]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5382
Loc: Bowmanville, Ontario, Canada
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.


Edited by bridgman (07/07/06 09:38 AM)

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#141429 - 07/07/06 10:07 AM Re: My 2nd attempt at graphing my room response? [Re: bridgman]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13333
Loc: Iowa
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.
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