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This plot looks really nice too. I guess I need to study REW more! What window are you using to plot this? Also, how do you plot percent instead of dB?

4.3 meters comes out to about 14 feet. I know for sure the mic was between 4.3 to 4.4 meters from the front as I just check using one of these: http://www.boschtools.com/Products/Tools/Pages/BoschProductDetail.aspx?pid=dlr130k Your plot looks nice. Is there some benefit to using the impulse plot over the ETC plot? I posted a ETC plot a few posts back (post 57). The speakers are rear ported, should I still move them 1 foot from the front? If I don't move the speakers toward the front wall, it sounds like I need to better treat the front which is hard as there's a screen in the way. I could place two layers of foam every where I see wall and see what happens... Or would treating the back wall really well work instead? I went back and looked at the right channel ETC plots, and it also has a peak near 4.38 meters. Thanks for your help!

Just woke up! It's a nice day off work as my sister is in town. Her and my wife talk really fast when they get together, so I'm hiding

I agree. I'm learning slowly a few of the things ChrisA has already learned (thanks to his help). Even with Audyssey Pro, studying room acoustics has increased performance for me, far beyond what I thought it would. Guitar Noir from AIX records is pretty neat, as are some of their samples. They'll probably throw in a free sampler with your order if you call and order from them directly. Nora Jones Come Away With Me SACD is another excellent recording. If you can find one used on Amazon, this is an extremely dynamic multi-channel recording; definitely one of my favorites: Gordon Goodwin's Big Phat Band - XXL

I never liked Audyssey MultiEQ XT. Audyssey XT32 is much better, but I still wasn't satisfied with it. The good thing is newer AVR's have an "Audyssey Flat" setting to bypass the HF roll off. I don't know if it bypasses the midrange compensation, but this is something the Pro kit allows you to disable. The Audyssey Pro kit + license works great for me, but adds a lot to the cost. There's also SubEQ HT on newer AVRs that independently adjust both subs, then calibrates them together. This works great for me too.

You can use an extraction tool to get the dts files out, then use foobar2000 to convert them to flac. I think I used DVD decrypter in the past to extract the dts audio, but can't remember now.

Doh! I just remembered something strange about my preamp, the multi-channel inputs (e.g. "7.1CH IN") bypass Audyssey XT32 This means buying an external sound card will not be indicative of real performance as it bypasses Audyssey altogether.

Mike, The main speakers are crossed at 80Hz. The preamp (Marantz AV8801) manages the crossover point and roll off internally. I'll have to change my test setup to send three signals at once. I was using HDMI to send the signals to the preamp, but Room EQ (REW) only lets you select one channel over HDMI for each test. The mic I'm using is one of those USB Dayton Audio calibration mics (UMM-6). Cross-Spectrum Labs calibrated it, and I've been using the narrow band 90 degree calibration file, with the mic pointed towards the ceiling. I'm going to study and see if I can devise a way of using y-cables from the analog outputs of a sound card. The problem is my laptop doesn't have any analog outs except stereo, and my home theater PC is in another room 50' away. I take it you are saying I need to run multiple channels together to get a feel for the room response. I'll have to buy a USB analog sound card just for testing purposes then. I think the USB sound card would come in very handy any ways, so I'm not against buying it though. It may be a few days as I'll likely have to order online, but I can see what Guitar Center has as they just opened up here. EDIT: Please see next post, I don't think using analog outputs from a sound card will work in my testing?!? EDIT 2: I can run two channels of HDMI at once, and leave the crossover to the subs via the preamp. This sort of gives what you are looking for: http://www.hometheatershack.com/forums/rew-forum/72320-multiple-hdmi-channels-simultaneous-outputs.html#post668794 PS: The article you linked to is very good information. It makes sense to use 1/4 wavelength to account for travel time. Thanks!

Is this how one should look at the dip?!?: f = 111 Hz, 343 m/s = c (speed of sound) lambda = c/f = 3.09 meters = 10.1 feet This distance doesn't match any boundary to the mic, except that one of the ceiling corners to the mic measures very close to 10.1 feet. However, it seems the dip would be due to phase cancellation, so maybe I should be looking for distances of n = (lambda/2), where n = 1,3,5... so that the reflected waveform would travel back and be 180* out of phase? Of course, the mic was 3.1 feet from the floor, not 5 feet. The ceiling distance wasn't 5 feet either. I'm really not sure what boundary is 5 feet or some odd multiple of (15,25, etc...) ?!?

Mike, Below is my ETC plot. It looks like the ETC plot is useful for determining reflections, hence would be indicative of imaging performance? The peak I've marked at .6 meters is the same distance to the large projector (PJ) overhead to the mic. The second peak at 4.3 meters is the distance of the front wall to the mic. Unfortunately, due to the PJ screen, I can't easily treat the front wall. I'm really constrained on the PJ placement due to attic that fold down out of the ceiling. I could move the speakers towards the front wall though and move the MLP out from under the PJ if you think this would help? I can post some updated pics of how the room looks now if it'd help as I've changed things from the original post. Thanks!

Hi Mike, The FR plot looks good, except for the dip at 111Hz, which is the same one on the waterfall plot. I guess the thing I should try is moving the mic around the MLP to see if it goes away? I measured everything with the mic at the MLP. I had my chair back all the way down, so there isn't much to interfere with the mic, except the projector above the MLP.

The Palladiums really are great sounding speakers. They sounded good with no room treatments, but truly blow me away with bass traps and 4" foam. My La Scala's sound great, but really can't compare to the detail and clarity of my system now. The imaging is better than its ever been. On tracks such as this 3 ft dry drum imaging test: http://www.hdtracks.com/best-of-chesky-jazz-and-more-audiophile-tests-volume-2, the imaging and bass is nothing but incredible. Admittedly, one could upgrade the LS II with a bigger horn and a better compression driver such as the TAD 4002 and get the clarity and detail, but I didn't have the room to do this.

I bet a near field measurement would more accurately measure the THD of my midrange -great idea! Supposedly its under 1% according to the reviews. I guess the noise floor of my room and distance from midrange is effecting my result. I hear you about the bass measurement though. If the things weren't so heavy one could take them outside to measure THD.

Everything sounds great as one would expect! Definitely better than some $140k+ systems I've heard in shops.

Thanks Chris, no hurry. I won't be able to measure these until later this week or next week as my sister is in town. She and my wife are using the theater now watching Interstellar. It's a great movie by the way! If you can dig up two old files for IMD and THD, I can level match my system to yours (and use the same test tone for IMD). I've heard your system and really loved it, so it would be interesting for me to study the REW files (now that I'm slowly learning more about REW and room acoustics).

Old REW sealed mode test data (prior to GIK bass traps). sealed only.zip

Thanks! I'll have to play with this later in the week. I also edited my previous post (aka added a bunch of questions ) with the sealed THD measurements just above your's; probably why you were typing your last post.

Old sealed mode comparison (all measurements are following an Audyssey Pro calibration each time). What is interested is sealed mode causes an increase in THD at lower frequencies? Also, 15% THD @20Hz seems really high to me, especially given 95dB is no where near the full output of my system. Is this an accuracy issue with REW? All reviews of the SVS PB13 ultras showed very low THD when measured outside. The 3% THD of the mid-range is disappointing too (compared to this review of the P39f)?

I definitely hear things clearer in the room versus untreated. I can hear every lip smack as well as air movement from well recorded vocals. This makes a lot of sense now that you mention it; thanks for this great insight! The mic was in the middle of where the main listeners head would be, right at ear level (seated in the money seat). I lowered the chair back all the way down so there should have been very little influence from it this time around. I think the first time the chair back was lowered only partway. I just looked at the distortion graph. How does this compare to an excellent all horn loaded setup like yours? (which is what I really would like if I had the necessary space) Also, does REW have the capability to feed a complex signal (containing multiple frequencies), to measure IMD? I'm assuming there's some standard waveform that is used for IMD measurements? I want to experiment with sealed versus 16 Hz mode some more. I have some prior measurements from before the bass traps that I'm going to compare. I briefly tried sealed when I set up the room, but had read that this would take away a lot of the output capability (not that I'd ever use it), and this could be missed for LFE in movies. I'm going to post some old files here shortly. Happy Easter everyone!

Here's a better "before" waterfall of the left P39f with Audyssey Pro and the SVS PB13 ultra's. I forgot what the crossover was at, but it'd be 60 or 80 Hz. The improvement is pretty neat to hear (and feel) first hand. AFTER: BEFORE:

I'm not sure why the files wouldn't work unless the forum's software did something to them. They do need to be unzipped before REW will open them. Anyone else having issues? The more I think about it, the more I think 4 more soffit traps probably won't give me much better performance. No way are they going to do anything about the decays below 50 Hz. I promise to measure one with just a P39f with no crossover and Audyssey enabled. I'm in listening mode now It's really beyond words about the tactile and articulate bass I have now. I'm truly speechless about the sound. I'm running out of ways to squeeze performance out of my current room. I think a bigger room would definitely help below 40 Hz.

Yes, yes, I know. Younger folks like me really aren't into vinyl or reel to reel. In fact, I use my PC to play all of my music. I'm definitely not a traditional audiophile.

Attached is the newer REW file with just the left P39f measurement (due to size), crossed at 80Hz to dual SVS PB13ultras. P39f crossed at 80Hz.zip

Attached is the newer REW file with just the left P39f measurement (due to size). This is with "pure direct" enabled on the AVP, meaning no crossover and Audyssey XT32 is disabled. P39f only.zip

Chris and friends, I finally reran Audyssey XT32 pro this weekend after adding 4 GIK soffit bass traps and 2 GIK monster bass trap panels. These new panels were added after leaving the foam in my previous pictures, but relocating some of it within the room to make space for the bass traps. The results are very interesting. It looks like from a decay time perspective, my P39f's perform better at 40 Hz than when crossed over to the SVS PB13 ultras (when the preamp is in "pure direct" mode)?!? Could this be because the DSP of the subs are negatively affecting decay times or is it due to the driver size difference (13.5" versus 3 9" drivers)? How much better do you guys think the subs could perform if I run it in sealed mode (they are in 16Hz ported mode now)? Any thoughts on these new measurements compared to my old ones? Is it worth buying 4 more soffit bass traps (new REW file will be in next post)? I think overall, the subs seem better performing (in the important 60-80hz region) than running with just the mains and no Audyssey. I think the 60-80Hz improvement confirms the little extra punch I'm feeling now. Note that the response curves have no smoothing applied, but look pretty good I think.