Bossobass Dave Posted February 9, 2015 Report Share Posted February 9, 2015 Still waiting for pricing of the particle velocity probe and vibration meter hardware. Musing in the meanwhile... If sound pressure, acoustic impedance and particle velocity are parts of a mathematical formula, for example, specifically, if you know the acoustic impedance and sound pressure, you can calculate particle velocity, then is must be the acoustic impedance that changes the equation, and subsequently, the sensation difference. We know the sound pressure by measuring it. The only way for particle velocity to change when sound pressure is identical is if acoustic impedance changes. Otherwise, if we know the sound pressure and acoustic impedance, we can calculate the particle velocity, which will be the same for both placements when the sound pressure and the acoustic impedance are the same for both placements. _____________________________ Max, In looking at just the near vs far placement measurements, they show the classic difference of room gain, even though your resonances are far more challenging than what I'm used to. As I mentioned weeks back in another thread, your response seems to have the classic resonant frequency (and multiples thereof) bumps. Peaks appear in multiples of the 6.x Hz peak. http://data-bass.ipbhost.com/index.php?/topic/255-questioning-conventional-wisdom/?p=3736 Otherwise, the near field is tiled toward the top end while the far field is flatter. You reconcile them to a compromise response which is less flat than the far field and flatter than the near field. I'm positively certain that we'll see that basis in every room with whatever sub, assuming the near and far field placed subs are the same model/design/alignment. Link to comment Share on other sites More sharing options...
maxmercy Posted February 10, 2015 Report Share Posted February 10, 2015 Right now I am using a global EQ solution, which is pretty good, only a small dip at ~20 Hz. I may also try to EQ each sub separately and see how they combine, both with and without the delay. JSS Link to comment Share on other sites More sharing options...
MKtheater Posted February 10, 2015 Report Share Posted February 10, 2015 I ran some sweeps last night. I still have some leaks going on in the wall so this is not final. I ran -20 MV, -10MV, 0 MV, and then +5 MV. What happened to last sweep? I did hear some rattles behind the wall. I have a 120 hz 48 dB per octave LR on the subs. This was with HDMI input and RS meter C-weight. For some reason this computer does not recognize my Umik and the one that does was in operation with the wife. Link to comment Share on other sites More sharing options...
Ricci Posted February 10, 2015 Report Share Posted February 10, 2015 My room response looks quite similar to Max's with the position of the nodes a little bit different. I suspect his seating is towards the center of the space. I have a huge peak at 46Hzish. This is common with seating in the center of the room. Link to comment Share on other sites More sharing options...
maxmercy Posted February 11, 2015 Report Share Posted February 11, 2015 I ran some sweeps last night. I still have some leaks going on in the wall so this is not final. I ran -20 MV, -10MV, 0 MV, and then +5 MV. What happened to last sweep? I did hear some rattles behind the wall. I have a 120 hz 48 dB per octave LR on the subs. This was with HDMI input and RS meter C-weight. For some reason this computer does not recognize my Umik and the one that does was in operation with the wife. Compression? Either in the signal chain, amp or speaker. JSS Link to comment Share on other sites More sharing options...
maxmercy Posted February 11, 2015 Report Share Posted February 11, 2015 My room response looks quite similar to Max's with the position of the nodes a little bit different. I suspect his seating is towards the center of the space. I have a huge peak at 46Hzish. This is common with seating in the center of the room. MLP Just a bit forward of the center of the room's longest dimension. EQ'ed I am +/-2dB save for the dip at 20Hz, +/-2dB throughout if I boost 20Hz by 2dB. The room is not a rectangle, the back corner is intruded into by the utility room of the house, so it's a rectangle with a piece of a corner taken away. I'll experiment more next week with individual sub EQ to try to get the best FR, ETC and impulse. JSS Link to comment Share on other sites More sharing options...
MKtheater Posted February 11, 2015 Report Share Posted February 11, 2015 Max, I thought the same but 3-4 hz is higher than a 5 dBs gain. I would think more mic error, maybe? Link to comment Share on other sites More sharing options...
Ricci Posted February 11, 2015 Report Share Posted February 11, 2015 MLP Just a bit forward of the center of the room's longest dimension. EQ'ed I am +/-2dB save for the dip at 20Hz, +/-2dB throughout if I boost 20Hz by 2dB. The room is not a rectangle, the back corner is intruded into by the utility room of the house, so it's a rectangle with a piece of a corner taken away. I'll experiment more next week with individual sub EQ to try to get the best FR, ETC and impulse. JSS Mine is just a bit back from the center of the long dimension and instead of a corner intrusion I have a large hallway off of one corner. Link to comment Share on other sites More sharing options...
maxmercy Posted February 11, 2015 Report Share Posted February 11, 2015 Max, I thought the same but 3-4 hz is higher than a 5 dBs gain. I would think more mic error, maybe? That would be my guess, as it looks like you have 2dB compression throughout except there. From my experience with mashed up waveforms on the OScope when playing above 0dBMV, it could be digital clipping somewhere....hard to say. JSS Link to comment Share on other sites More sharing options...
maxmercy Posted February 11, 2015 Report Share Posted February 11, 2015 Great graphs, thanks I have been pondering nearfield myself recently - perhaps a couple of nearfield would fill my huge 30Hz null nicely and also give some added tactile effect, same as yours do? I will have to do some room modelling to see if I can find an ideal solution... (I'm not too keen on the idea of subs over downstair's living space, at least where the current ones are now they are over the entrance hall, but if needs must... lol. I could allways turn them off of an evening!) Do you find adding the delay to the nearfield subs makes them sound a bit 'smeared' and a little less punchy? Or is it the case that you add a delay that means the front subs' wavefront hits you as the delayed nearfield subs kick you in the back, meaning you get a tight, time-aligned wavefront and maximum impact? I added a nearly time-aligned delay to the rear subs. Basically I played around with different delays until I got rid of the suckouts in the midbass as much as I could, it turned out that it was very close to the same delay I would have used to time-align. JSS Link to comment Share on other sites More sharing options...
MKtheater Posted February 12, 2015 Report Share Posted February 12, 2015 Max, Good call, I never even thought about clipping from the input side of things or the mic. It was a monster sweep! Link to comment Share on other sites More sharing options...
Bossobass Dave Posted February 14, 2015 Report Share Posted February 14, 2015 MLP Just a bit forward of the center of the room's longest dimension. EQ'ed I am +/-2dB save for the dip at 20Hz, +/-2dB throughout if I boost 20Hz by 2dB. The room is not a rectangle, the back corner is intruded into by the utility room of the house, so it's a rectangle with a piece of a corner taken away. I'll experiment more next week with individual sub EQ to try to get the best FR, ETC and impulse. JSS Mine is just a bit back from the center of the long dimension and instead of a corner intrusion I have a large hallway off of one corner. flora raw vs gp.jpg Wow. Looks like you guys got together in PM and rigged these: Link to comment Share on other sites More sharing options...
Bossobass Dave Posted February 14, 2015 Report Share Posted February 14, 2015 Watched Lucy and bumped the SW trim as Abraham suggested. Not much below 30 Hz in this one and the low end is indeed weak vs something like Godzilla. It did have a couple of scenes with some unfiltered effects, most notably the flips backward in time. I thought I had capped the one back to dinosaurs, but apparently I lost it in the transfer from Dell to Mac. Anyway, here's 2 scenes, typical of the rest of the flick (and these are mic'd with the trim bumped +6dB): BTW, I really liked this movie. SJ does a great job of transition from ditz-blonde to super intellect and the visuals and stunts are well done. I'll prob buy it. With a couple of scenes with appropriate ULF, this one would have been a contender. Ah, well... those French dudes will have to get religion. Link to comment Share on other sites More sharing options...
Bossobass Dave Posted February 14, 2015 Report Share Posted February 14, 2015 If the Denon is kept at MV -11dB with the individual channels at 0dB, clean waveforms with worst case scenario. I didn't turn down the speaker trims individually to see if I could turn the MV up higher. What I did do was turn down the digital input (there is a setting for this) and at -11dB, you can be at 0dBMV and still have clean waveforms with WCS. But then you essentially have to set your amps to play 11dB higher, which could elevate the noise floor, but only if you want to hit reference. I get around the entire issue by using nanoAVR to bass-manage, and ensure that a WCS won't clip the nano. I can set individual crossover frequencies and slopes for every channel, both for the low and highpass. I intend to do that in the next few days once I get a full measurement salvo done (for all the seating positions), and after the EQ experiments with the sub clusters I mentioned in Bosso's thread. Too bad nanoAVR requires decoding to LPCM prior, it's main disadvantage. But then, there would be Dolby and DTS licensing problems (and $$$) if it could decode. JSS I nicked this ^^^ from the other thread. You should use a real worst case soundtrack for comparison to your theoretical worst case results. The 2 in my library were 1) the Red Death dragon crash scene in HTTYD and 2) the bridge collapse scene in WOTW. That was with MVL at 0dBRL and all trims to '0' (whatever RL is for the DUT). There are, of course, many titles I don't have in my collection that are contenders for worst case scenario. Maybe you could measure a few and see how they compare? Link to comment Share on other sites More sharing options...
Ricci Posted February 16, 2015 Report Share Posted February 16, 2015 Wow. Looks like you guys got together in PM and rigged these: Very similar indeed. I had done nothing more than look at his response but thought it looked VERY similar. I'm glad my guesses on his placement of the seating and room shape were close. It confirms what I suspected. Link to comment Share on other sites More sharing options...
maxmercy Posted February 16, 2015 Report Share Posted February 16, 2015 I nicked this ^^^ from the other thread. You should use a real worst case soundtrack for comparison to your theoretical worst case results. The 2 in my library were 1) the Red Death dragon crash scene in HTTYD and 2) the bridge collapse scene in WOTW. That was with MVL at 0dBRL and all trims to '0' (whatever RL is for the DUT). There are, of course, many titles I don't have in my collection that are contenders for worst case scenario. Maybe you could measure a few and see how they compare? HTTYD (all channels mixed in) vs 7.1 Worst-Case-Scenario (all channels mixed): The difference is only 3dB (linear vertical scale), that Dragon Crash is a truly powerful effect, being only 1dB away from the 5.1 Worst-Case. That means EVERY processor I have tried will not output HTTYD's Dragon Crash correctly if speaker/sub trims are set at 0dB and MV is at 0dB, as the best processor so far measured required ~10dB of attenuation to output a clean signal with the trims set as above. JSS Link to comment Share on other sites More sharing options...
Madaeel Posted February 16, 2015 Author Report Share Posted February 16, 2015 Wtf Earth to Echo made me dive for the remote... Link to comment Share on other sites More sharing options...
Madaeel Posted February 16, 2015 Author Report Share Posted February 16, 2015 So is the Denon going back? Link to comment Share on other sites More sharing options...
maxmercy Posted February 17, 2015 Report Share Posted February 17, 2015 So is the Denon going back? I am keeping it. NanoAVR will handle bass management and prevent the clipping in any scenario including worst case. JSS Link to comment Share on other sites More sharing options...
MKtheater Posted February 17, 2015 Report Share Posted February 17, 2015 Is that because the NanoAVR has a wide range for levels? With high sensitivity speakers I usually have the processor's trims at 0, MV at 0 for reference but the levels in the NanoAVR are at -10 to -20. Link to comment Share on other sites More sharing options...
maxmercy Posted February 17, 2015 Report Share Posted February 17, 2015 Careful with lowering nanoAVR levels by 20dB as you could lose sound data above your noise floor (if you have a quiet room). Once you are below a certain threshold, attenuated data is lost. But most rooms are not as quiet as we think they are, and with dialogue at 75-85dB, a 10dB signal is likely to be masked. The nanoAVR bass manages by lowpassing all the LCRS channels and then taking the lowpassed signals and turning them down by 10dB, then adding the LFE in, then I put the WCS in and set levels so that no digital clipping is present. I know that some data is lost with the attenuation, but my noise floor is around 25-35dB (40dB when the HVAC is on), so I can only resolve so much to begin with... JSS Link to comment Share on other sites More sharing options...
MKtheater Posted February 17, 2015 Report Share Posted February 17, 2015 My mains and surrounds usually get set to -10 to -5 where the bass is usually set to -20. Of course I can turn the trims down in the processor and increase the NanoAVR levels. It sounds awesome either way. Link to comment Share on other sites More sharing options...
Madaeel Posted February 17, 2015 Author Report Share Posted February 17, 2015 I am keeping it. NanoAVR will handle bass management and prevent the clipping in any scenario including worst case. JSS Nice. It doesn't do 4K right? $900 isn't bad I'd just prefer my next pre/pro to do 4K. Link to comment Share on other sites More sharing options...
maxmercy Posted February 17, 2015 Report Share Posted February 17, 2015 I really don't know....I do not plan on upgrading to 4k until it is adopted by broadcast TV. Then I'll upgrade to 4K and see if 3D sound has caught on before buying a new processor....to take advantage of 4K, I would need nearly a >150" screen at my current viewing distance. I need a bigger front wall for that. With my current space and low ceilings, ceiling sound really won't be that big a jump. Considering most sound production on big films is compressed and clipped, I could probably not justify adding 2-6 more amp channels and speakers just to hear clipped sound coming out of all of those new channels, to say nothing of the SW out headroom problems that already exist and will become worse, by another 2-3dB. Best soundtrack of this year that I have experienced so far in regards to clipping with a terrific presentation was Fury, and it is a 5.1 track (just needed a little more ULF). With BEQ, it should become even better. I probably need to experience the ceiling channels in a well-done setup, because the jump from 5.1 to 7.1 was not near as large an impact as ProLogic to Discrete 5.1 was. I think adding the wide L/R channels would add more than just the ceiling channels. Getting way OT now... JSS Link to comment Share on other sites More sharing options...
Shredhead Posted February 17, 2015 Report Share Posted February 17, 2015 Dragon Crash is a truly powerful effect, being only 1dB away from the 5.1 Worst-Case. That means EVERY processor I have tried will not output HTTYD's Dragon Crash correctly if speaker/sub trims are set at 0dB and MV is at 0dB, as the best processor so far measured required ~10dB of attenuation to output a clean signal with the trims set as above. Here is a test I did on the OPPO BDP-105. First some back-story: The OPPO does not have a volume scale in dBV. It is like a cable box in that it's volume levels go from 1-100. I found the OPPO's reference level by using a meter as a comparative tool. I had Madaeel set up his receiver to reference level with sub trim set to 0dB, we ran a scene from the movie "9", I measured the voltage out and then I matched the voltage out on the OPPO using the same scene (both processors had the same x-over settings and no EQ engaged). That gave me the number 91 on the MVL (master volume level) for the OPPO's reference level. The OPPO has a maximum rated voltage out of it's sub jack of 2.1V. I spoke with a tech at OPPO and confirmed that it reaches it's maximum clean output at 2.1 peak volts. The MVL of 91 happened to work out so that many of the hottest movies' bass transients approach but do not exceed that level. Reference at 91 also allows for a usable portion of gain past 91 for weak source material. On to the test: I put the sub out from the OPPO into an interface. I ran Speclab with the same Dragon Crash scene from HTTYD at 2 volume levels, 66 and 91 on the OPPO with the sub trim at 0dB, all 5 speakers set to small and the crossover at 100Hz. I used the interface's input sensitivity control to level match the 2 different out levels from the OPPO into SL as close as I could get it. As you can see at the top of the pic, there is no noticeable difference between either of the 2 volume level's waterfall or waveform. I then used a DAW (digital audio workstation) to further analyze the waveform to see if there was any compression or clipping. For folks that don't know, this is basically using an interface and DAW as an oscilloscope to capture and view the analog sub out's waveform, digitally. In the picture you can see the 66MVL and 91MVL lined up, zoomed in and out and the 91MVL waveform is the one on top. I once again used the interface's input sensitivity control to level match them as closely as I could but I could only get them this close. Any difference in what they look like is because of this difference in the 2 waveforms' amplitude. As you can see in the zoomed in picture of the 2 volume levels waveforms, there is no indication of clipping or compression (on the wave that is zoomed in the most, the highest point in the very middle of the screen is the highest transient peak of the scene). I then used a Fluke 87-V meter to measure the peak voltage out of the sub out for both volume levels. For the 66MVL, it read 550.5mV and for the 91MVL it read 2.344V. The Fluke's 250 microsecond peak voltage hold isn't going to be spot on with frequencies around 20Hz and below but in my experience, it's pretty damn close. I then ran the scene at 91MVL into the SEQSS to see if it would trip the peak voltage circuit indicator light (set to 2.1V peak) and it did not. This agrees with the 87-V's spec of +/-100 counts for transients >250us in duration (you can figure on a little more error due to low frequency content). I believe that setting up your system with the BDP-105's volume of 91 for reference is a winner for a worst case scenario with sub trim at 0dB. The SEQSS is perfectly mated to it in gain structure and even in a worst case of it's peak light tripping, it is not going to clip. It's just going to stare back at you and flex. Now on to another test: I measured the subwoofer voltage out with the meter of an Onkyo AVR that DID have it's volume in the dB scale. The AVR was set to 0dB MVL, 0dB sub trim, 5 speakers set to small and x-over set to 100Hz. The peak voltage reading for the Dragon Crash scene was 14.87V. I then tested a Sony's sub out. The only x-over point possible was 77Hz for 5 mains set to small and it's sub out is 3dB down at 7.4Hz. The sony's volume level goes from 1-74... don't ask me what sense that is supposed to make. I figured I would test the volume at ~9/10 of full level. I tested the Dragon Crash scene at 66 for the MVL, and with the sub's trim set to 0dB the Dragon Crash scene gave a peak reading of 8.19V. So it would seem that there is no standard for levels on the sub out. I've known this for a while which is why I designed the SEQSS with a peak voltage indication light so that you can play a worst case movie scene like HTTYD's Dragon Crash and ease your sub trim's level up while at the number you pick on MVL for your reference until it just starts to blink. I had to pick a safe low enough peak voltage level out so that most AVR's or pre/pro's wouldn't go into saturation but still have the level robust enough to not degrade the signal. Then your gain stages are optimized all the way to the amp for the most dynamic range without clipping. For the average user though, you will have to test all of your small signal equipment (because it's apparently all designed differently) to find just under it's breaking point for worst case scenario in order to optimize the gain stages on the way to the amplifiers to maximize dynamic range. Max's test disc will be very helpful for this but as I've shown, you can also use real world source material. Damn, this is a long post. Link to comment Share on other sites More sharing options...
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