etc6849 Posted April 5, 2015 Author Share Posted April 5, 2015 Old REW sealed mode test data (prior to GIK bass traps). sealed only.zip Quote Link to comment Share on other sites More sharing options...
minermark Posted April 5, 2015 Share Posted April 5, 2015 I like seeing someone who knows what they are doing, before and after REW tests Rule! Move stuff around, Test, move stuff around, (panels). Quote Link to comment Share on other sites More sharing options...
etc6849 Posted April 5, 2015 Author Share Posted April 5, 2015 (edited) 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). I'll look around to see if I've got a plot that is close to the SPLs that you posted. I haven't saved any two-tone test results, i.e., modulation distortion levels. Note that these are also very level dependent. Edited April 5, 2015 by etc6849 Quote Link to comment Share on other sites More sharing options...
Chris A Posted April 5, 2015 Share Posted April 5, 2015 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 You may find your answers here: http://www.data-bass.com/data?page=system&id=55 1 Quote Link to comment Share on other sites More sharing options...
garyrc Posted April 5, 2015 Share Posted April 5, 2015 Remember that horns and vented enclosures typically have about the same harmonic distortion levels, but vastly different modulation distortion levels This was missed in the THX folder of c.1979. They based their preference for bass speakers that were not horn loaded on harmonic distortion only, and did not even mention modulation distortion! Maybe they got around to it in later years, but I see that almost all theater speakers (including subs) are now direct radiators. To my ears and emotions, the old monster bass horns by JBL and Altec, especially in theaters designed for Todd-AO, sounded better -- so impactive, so clean, so effortless! 1 Quote Link to comment Share on other sites More sharing options...
Chris A Posted April 6, 2015 Share Posted April 6, 2015 (edited) The 3% THD of the mid-range is disappointing too (compared to this review of the P39f)? That's basically second harmonic distortion that you're looking at. I pay more attention to the third and higher harmonics myself. However, that's not to say that any harmonic distortion is good--it's not, since any harmonic distortion also contributes to modulation distortion products on the lower sidebands, and to the overall muddiness/opaqueness of the sound stage. I've attached a FR+distortion plot of my right Jub plus the TH subs, microphone at 1 metre from the front of the Jub centered between the bass bin and the K-402, looking up at approximately 20 degree angle. Note that nearfield effects on bass measurements and floor, ceiling, and sidewall bounce cancellations of the recorded response are present: Edited April 6, 2015 by Chris A 1 Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted April 6, 2015 Share Posted April 6, 2015 I am enjoying following this thread. etc 6849, how do things sound in the room and your overall impression of the Palladiums? 1 Quote Link to comment Share on other sites More sharing options...
etc6849 Posted April 6, 2015 Author Share Posted April 6, 2015 Everything sounds great as one would expect! Definitely better than some $140k+ systems I've heard in shops. how do things sound in the room and your overall impression of the Palladiums? 1 Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted April 6, 2015 Share Posted April 6, 2015 Now that's the ticket, lo. I am glad things sound great! Quote Link to comment Share on other sites More sharing options...
etc6849 Posted April 6, 2015 Author Share Posted April 6, 2015 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. I've attached a FR+distortion plot of my right Jub plus the TH subs, microphone at 1 metre from the front of the Jub centered between the bass bin and the K-402, looking up at approximately 20 degree angle. Quote Link to comment Share on other sites More sharing options...
Chris A Posted April 6, 2015 Share Posted April 6, 2015 Yes - I found that measurements at the listening position are corrupted by room acoustics. Quote Link to comment Share on other sites More sharing options...
etc6849 Posted April 6, 2015 Author Share Posted April 6, 2015 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. Now that's the ticket, lo. I am glad things sound great! Quote Link to comment Share on other sites More sharing options...
Chris A Posted April 6, 2015 Share Posted April 6, 2015 It was Greg Oshiro that encouraged me to continue my experimenting with in-room measurements (using REW), so I did the trial-and-error thing for several weeks until I started to get better data. Here a brief synopsis of what I learned: https://community.klipsch.com/index.php?/topic/123370-settings-for-tri-amping-an-82-belle-with-an-active-digital-crossover/?p=1807354 1 Quote Link to comment Share on other sites More sharing options...
DrWho Posted April 7, 2015 Share Posted April 7, 2015 What is causing the big notch at 120Hz in your waterfall? Is that a reflection from a nearfield boundary? I think it's easier to analyze the effects of acoustic treatment if you don't change the EQ between treatments. Rerunning Audyssey is changing your EQ. Have you taken any looks at the ETCs yet? That's where most of your imaging information will be. Quote Link to comment Share on other sites More sharing options...
Chris A Posted April 7, 2015 Share Posted April 7, 2015 Hi there Mike. How ya doin'? Coming to Hope this weekend? Chris Quote Link to comment Share on other sites More sharing options...
etc6849 Posted April 8, 2015 Author Share Posted April 8, 2015 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. What is causing the big notch at 120Hz in your waterfall? Is that a reflection from a nearfield boundary? Quote Link to comment Share on other sites More sharing options...
etc6849 Posted April 8, 2015 Author Share Posted April 8, 2015 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! Have you taken any looks at the ETCs yet? That's where most of your imaging information will be. Quote Link to comment Share on other sites More sharing options...
etc6849 Posted April 8, 2015 Author Share Posted April 8, 2015 (edited) 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...) ?!? Edited April 8, 2015 by etc6849 Quote Link to comment Share on other sites More sharing options...
DrWho Posted April 8, 2015 Share Posted April 8, 2015 What is your subwoofer xover frequency and slope? A good place to start would be to measure the response of the mains with the sub turned off, then measure the sub with the mains disconnected, then measure the sum of the two. Plot all three responses on the same chart and you should see +6dB where the sub and main frequency responses intersect. You should also see flat passband to both sides of the xover frequency. One thing I've seen in the past is that if you have the subwoofer too hot, then the slope of the xover causes the acoustical xover frequency to move higher in frequency. This can in turn cause cancellation of the direct sound. I'm not sure if this is happening in your instance or not, but it's a good place to start. Then your comments about looking for 180 degrees phase shift in the reflections is also a good place to start. Keep in mind to account for the time the wave takes to travel....so generally you see the boundary about 1/4 wavelength away: http://peavey.com/support/technotes/soundsystems/boundarycancellation.cfm The 1/4 wavelength is a rule of thumb btw...as you get further away the frequency moves higher because the angle gets smaller between the direct sound and reflected sound. If you draw the triangle and measure the pathlength difference you'll see what I'm talking about. Quote Link to comment Share on other sites More sharing options...
etc6849 Posted April 8, 2015 Author Share Posted April 8, 2015 (edited) 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! What is your subwoofer xover frequency and slope? Edited April 8, 2015 by etc6849 Quote Link to comment Share on other sites More sharing options...
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