# ***Working man's home theater measurements*****



## nottaway (Jan 19, 2009)

Ok this is my first graph, played around with it last night long enough to get one graph off.

The room has 3 of 4 corners treated with bass traps and 5 other broadband absorbers. Three on front wall two on the side walls first reflection points.....

I know the subs need to be turned down, i didn't adjust anything just took a preliminary measurement.

How does this look? I have the BFD but it's not in the setup yet so I hope to get pretty flat in the end....


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## gorb (Sep 5, 2010)

Where's the graph?


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## nottaway (Jan 19, 2009)

Woops, forgot to attach the graph......


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## JohnM (Apr 11, 2006)

If the SPL meter cal is right those subs certainly are very loud at the bottom! The graph has a huge vertical span at the moment, which together with the fairly heavy smoothing does flatter things quite a bit. Try a vertical span of 60dB (say 60dB at the bottom and 120dB at the top for that graph) and less smoothing. You can adjust the range using the "limits" button to the top right of the graph.


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## nottaway (Jan 19, 2009)

JohnM said:


> If the SPL meter cal is right those subs certainly are very loud at the bottom! The graph has a huge vertical span at the moment, which together with the fairly heavy smoothing does flatter things quite a bit. Try a vertical span of 60dB (say 60dB at the bottom and 120dB at the top for that graph) and less smoothing. You can adjust the range using the "limits" button to the top right of the graph.


the subs are way hot, I've bottomed them occasionally and that never happened before, but my previous setup did not have anywhere near the dynamics of this one so I didn't need as much spl. 

The levels are pretty much what audyssey spat out, I haven't done much else yet.

ok I'll change the window tonight, and use a smaller smoothing factor, I just grabbed the first one I came to....


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## nottaway (Jan 19, 2009)

OK so reduced the smoothing and changed the graph axes to zoom in on the response. This is the same measurement as last night just reformatted. Anyways I'm gonna reduce the levels and measure again, try to get it flatter instead of flying off the handle on the low end....


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## nottaway (Jan 19, 2009)

OK so I did a bit more with the subs. Changed the position a bit moving farther away from the center of the room towards the corners. Also turned them way down, and ran out of control on the controller for turning them down so I'll have to go behind the screen wall to turn the subs down themselves......

Heres what I ended up with before girlfriend insisted we do something besides play with my geeky toys.....

Any recommendations?


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## Wayne A. Pflughaupt (Apr 13, 2006)

Not bad! A BFD could fill in that 32 Hz depression and you’d have picture-perfect response. :T

Regards,
Wayne


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## savior sound (Nov 30, 2008)

nottaway said:


> Any recommendations?


If that were my graph, I might try to cut some of the 20-25Hz hump rather than boost 32Hz. See what that does for you. That will give you a flatter response to down in the subsonic region. But that might not be what you're after. I don't know. BTW what sub(s) are you running?


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## nottaway (Jan 19, 2009)

I've been playing with the filters in REW to see what the predicted response would be.... I don't have a power cord for the BFW yet so all these filters are just hypothetical until I pick up a IEC cord. 

Anyways it looks pretty flat all the way out to about 10 according to the graph. I used the "target" line for reference, but I'm not sure if that is where I should be. Does this graph look good or ideal or should I be targeting something similar to a house curve which accentuates the lower bass?

I'm running two MFW-15s in about 2500ft^3.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Looks pretty good, but the scale you’re using – 150 dB wide – makes response look better than it really is. Try re-scaling the graph for something like 60 dB wide for a more realistic picture.

When you get the BFD up and running you can experiment with house curves vs. flat response. :T

Regards,
Wayne


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## nottaway (Jan 19, 2009)

So I put the BFD into the system last night. Got a better response with about 7 filters. I'm sure I could do better with less filters if I had more experience, but thats another story. Here's the before and after:










Here is the final result with 7filters:











On a side note I was having problems with Audyssey detecting my right speaker. The problem followed the speaker so I measured. Looks like either the tweet is blown, came loose, or the crossover has a component failure. The tweet doesn't make any measurable ouptut after the mids crossover from 2-3K. Looks like ill have to do surgery sometime soon.


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## savior sound (Nov 30, 2008)

Looks good. How does it sound? What does it look like out to 200 Hz? What's your x-over at? I'm curious about something else as well. Where is the door to the room located and what does having it open do to your FR?


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## nottaway (Jan 19, 2009)

I think it sounds pretty good. I have only watched Secretariat on it since calibration and its not a sub slug fest by any means. It has some issues on up in the frequency range I don't have all the acoustic panels I need yet just the front wall and primary reflections on side walls. I don't have a current full range sweep, maybe I can work on that tonight.lddude:

I get a bigger hump in the high 20Hz to mid-30Hz with the door open. Its in the back of the room. Wait here's some pics.....


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## fitzwaddle (Aug 25, 2010)

The response looks good to me! Where did you locate your subs?


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## nottaway (Jan 19, 2009)

Thanks it will get better!


Behind the screen wall equidistant from center and front corners.


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## nottaway (Jan 19, 2009)

If your running two subs in front of room spread apart, should you eq them seperately or together? I currently have them EQed together using summed response, but should I EQ them seperately? I'm pretty happy with the response I was able to achieve, but got curious about the proper way to do it.....


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## JohnM (Apr 11, 2006)

nottaway said:


> If your running two subs in front of room spread apart, should you eq them seperately or together? I currently have them EQed together using summed response, but should I EQ them seperately? I'm pretty happy with the response I was able to achieve, but got curious about the proper way to do it.....


EQ them together, neither sub alone will drive the room the same way as both do running together.


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## nottaway (Jan 19, 2009)

Ok, Thanks!


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## guerrax (Jul 2, 2011)

Yes, thank you for this information.


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## nottaway (Jan 19, 2009)

OK a couple more plots... I have no idea what they mean so could someone take a look. Where are my problem areas? What needs to be done? I know I need a bunch more bass trapping and broadband absorption but I really want to know how to interpret the graph as I go forward with acoustic treatment. Current treatments are:

Front wall: three abosorption panels centered behind LCR 2" OC703 with 4" air gap, and 4" OC703 in both corners floor to ceiling.

Side walls: 2" OC703 4" air gap primary reflections L and R.

Back: One corner 4" OC703 floor to ceiling, 4th corner has rack and shelf built into wall no treatment possible.


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## cjv998 (Jul 6, 2011)

I can comment on the plots somewhat (but keep in mind I'm just getting into the REW stuff myself, so take the opinions with a grain of salt - I do have a solid background in science though, so I'm decent with reading graphs...maybe not so good at explaining them though, but I'll give it a shot.)

Not sure if you're familiar with waterfall plots or not. What you're looking at is how quickly the frequencies decay over time - basically a good measure of how effective your room treatments have been. So at the back of the plot, you see your initial frequency response, which matches the plot you posted below it. (It should match, because it's plotting the same thing.) Then, as you look "forward" on the plot (along the axis that comes "out of the page"), you see the sound level of the frequencies start to drop off. This tells you how quickly a given frequency gets quieter after the speakers have stopped emitting that frequency. So it's related to how reverberant or "echo-ey" a room is - which, like I said, will show the effectiveness of your acoustic treatments. Just at a glance, it looks like your treatments aren't too effective below 50-100Hz - which isn't too surprising. From what I've read, that's the hardest range to treat with conventional acoustic treatments.

Personally, I'd love to see a waterfall plot all the way out to 20kHz - it should do a nice job of showing off those acoustic panels, since they'll probably be most effective above ~250Hz or so. (That said, they still look like they're doing quite well at 100Hz; definitely better than my untreated room I recently made a thread about...I'll have to post a waterfall in that thread tonight that you can compare to. I have a spectrogram I posted, which is similar to a waterfall plot, but they're hard to compare by looking at them side-by-side. Basically, a spectrogram is like a waterfall plot if you looked at it from the top down, in a birds-eye view.)

The spectral decay plot you posted at the top is similar to the waterfall plot, but all the data has been "collapsed" or compressed into the same plane. It's like if you took each "slice" of the waterfall plot, and made it a slightly different color, and laid them all on top of each other. At least, that's my understanding of what the plot shows. (you'll notice the results from spectral decay plot seems to look different than the waterfall plot - until you realize that the vertical scales of the two plots are different)


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## nottaway (Jan 19, 2009)

OK so it looks like I need a lot of work in the 10-20Hz area for sure. I only have about half the acoustic treatments I want in the end so with that in mind I'm looking for suggestions on treatments.

Here is the full respose, decay, and waterfall.... Suggestions?:


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## cjv998 (Jul 6, 2011)

That looks really nice! What main speakers are you using?

I'd do something about the peaks at ~250 and 500Hz if you can. Also, try to address the dips at 300-400Hz, and 2kHz, if you can. (I'd move the listening position a little, to see if they're due to the place you're sitting at, or if they come from something else). They don't look too bad though.

The sub still looks 10-20dB too high for my tastes, but that's a personal thing. If you like the way it sounds, go for it! Might be worth turning the sub down a bit, and listening to it for a while to see what you think. :huh:

That waterfall plot looks awesome, I wish mine looked half that good! (Here's my thread, so you have something to compare your results to.)


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## nottaway (Jan 19, 2009)

CJ,

I appreciate the responses!

All the speaks in my system except the mains are identical: EMP EF30Cs which are the internet direct version of RBH's TK515Cs MTM bookshelves.

The mains are the EF30Ts or RBH TK5CTs, TMMW Towers

Those front wides are on DIY stands made to look like the towers. I had to make them extra tall to align the tweets but they turned out real good I think. The speakers are the best I've ever had. Heres a pic of the mains lined up with the wides in case your interested....










The window seen behind is now filled with insulation and acts as an acoustic panel.

Like a proud parent I whip out some pics:bigsmile:


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