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Post by Boomzilla on Aug 2, 2016 16:50:45 GMT -5
Netbooks are wimpy little PC machines (Windows 7) intended for browsing, email, and light note taking. ARM Dragonball processors & munchkin RAM (512K ?). Probably not REW-ready... I don't need the microphone preamp or USB interface. My audio amigo & tech mentor, garbulky has the goods! Since I don't have a PC laptop (or desktop, for that matter), I either borrow the Gar's or else I run Windows in emulation via VM-Ware Fusion on a Mac. Since I get the impression that REW has to get snuggie with the hardware, it would be best to do this on Gar's Windows machine. Or, (plan B), I can just buy a Windoze laptop at the next garage sale for $25 and make it the "REW machine." Note that this rig isn't something I want to ever admit I even touched, much less kept... When the measurements are over, it's sanoyara to all this measuring junk and I'm back to enjoying music!  |
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Post by yves on Aug 2, 2016 18:09:02 GMT -5
After you are ready to get serious about room measurements... Well, I'm NOT really ready to "get serious about room measurements." Instead, I just want a one-time overview of where the peaks & valleys (if any) are in the bass. After that, THEN I'll decide whether to "get serious" or not. My gut feeling is "not," but depending on what I see on the curves, then I'll decide. Background - I've tried multiple versions of room correction software before and none (NONE) made any improvement at all. In fact, most made the bass not only worse, but SIGNIFICANTLY worse. "Flavors" tried include the Emo correction on their first processor, Yamaha correction (three different receivers), Denon room correction, and at least one other. Each and every one sucked eggs. My room has far, far less bass than any other room I've heard. I don't mean that some frequencies are missing - the room response seems smooth, but it sounds like a bass tone control is turned down between one and two notches. The bass is clean, tight, & tuneful, just gradually decreased in amplitude (unless the two 15" subwoofers are also working). This has been true through multiple speakers, multiple speaker positions, and both before & after room treatment. It's a big room with ATS treatment panels on all four walls. But there's an opening in EVERY corner (kitchen, foyer, hallway, & open stairwell). I've heard the SAME speakers in other rooms where they produced LOADS of bass, but not in my room. So if the bass response rolls off smoothly (as it seems to by ear), then a slight bass boost via equalizer or tone control should restore roughly flat response. If, however, the bass has huge peaks & throughs in addition to being gradually rolled-off, then some judicious EQ of the parametric nature may be required. We'll see... I don't use room correction software either. You can't use EQ to make huge troughs disappear, but that's no surprise to me because it is just how physics works. I.e., by trying to boost those frequencies with EQ you are only increasing the amplitudes of the sound waves that are actually *causing* the problem so it is only natural the fact it is making things worse, and, yes of course this is exactly why bass traps are typically *always* being used by people who do have a basic understanding about room acoustics. FYI, having an opening in every corner is not the same thing as having installed a corner bass trap in every corner. Bass waves that exit the room via these openings can be reflected back into this same room via these same openings so I agree you should take measurements to find out, among several other things, whether or not this is part of a problem you might be experiencing without necessarily being aware that you are experiencing it. (In Dutch, we have a saying about this, "meten is weten"...). In the region below 300 Hz, if measurements are accurate then if the frequency response data is visualized as-is (i.e., no "octave smoothing" is applied to it), a room response with peaks and nulls between +12dB and -12dB is considered really good. Without bass traps, peaks and nulls are very often between +30dB and -30dB or worse. So even if no huge bumps or troughs are visible after 1/6 octave smoothing has been applied to the graph shown on your computer screen, these wild variations still exist. And, as much as I hate to say this, they are very much audible in every room regardless of what people choose to believe. Even though, in pure terms of how it will sound like, narrow peaks and nulls are not as big a problem as wide peaks and nulls, and, even though narrow dips are not as big a problem as narrow peaks, taming these wild variations with broadband bass traps as much as possible is still going to be a starting point towards better room acoustics nevertheless. Remember the fact not all peaks and nulls in the frequency response are directly related to room modes. Some are related to SBIR (Speaker Boundary Interference Response), some are related to room modes, and some are related to both. Further, bass waves do not only reflect in the twelve corners of the room. As a result, standing waves occur everywhere throughout the entire room except of course if your room has no walls nor a ceiling.... But I have said it before and I will keep saying it, there is more to optimizing bass response in a room than dealing with peaks and nulls alone. At certain bass frequencies, DECAY TIMES are much longer compared to other frequencies. Looking at a frequency response plot alone is pointless because it ignores this equally important fact. That said, in a big room with lots of hard flat reflective surfaces it pays off to install pressure based bass trap panels each of which can be built specifically to be tuned strategically to a given frequency and frequency range, or Q. By placing along the big surfaces, in an alternating fashion, multiple pressure based bass trap panels of varying widths, thicknesses, and optionally also varying tilt angles, it is possible to more uniformly spread out the various interactions between bass trapping effects as well as to help reduce flutter echo. In smaller rooms there is not enough total surface area to work with pressure based bass traps, and peaks and nulls in the bass are more severe as well as are spaced less far apart in frequency. That's why heavy broadband porous absorbtion (velocity based, as opposed to pressure based) is a much better choice if the room is small. But using too much absorption can very easily make the room sound dead. (Dead rooms tend to emphasize bass problems more than live ones do). |
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Post by Boomzilla on Aug 2, 2016 18:19:33 GMT -5
Further room treatment may be problematic. Since I plan to sell this house within a relatively few years, I don't plan to make any permanent changes, and any temporary ones must be removable and not require damage to the paint or floors. Cylindrical, free-standing bass traps might be feasible, but there's no sense speculating about what might be needed until I know what the problems (if any) is. I'm relatively convinced that there are NO plus or minus 30 dB nodes in this room. But if there are, they'll be extremely narrow bandwidth. The REW curve will confirm this.
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Post by yves on Aug 2, 2016 19:16:28 GMT -5
I would start with a plot of room modes to see where the peaks and valleys are (i.e. points of reinforcements and nulls). See if your seating is on/near a null. As a one-time offer, if you send me your room dimensions (width, height and length) I will send you a plot. The real world room modes can differ substantially from the calculated ones. This is due to rooms not being perfectly box shaped, the rigidity of the walls/floor/ceiling, openings, doors, windows, ducts, a fireplace, alcoves, wall coverings, carpets, rugs, curtains/drapes, furniture... and besides, SBIR is at least as important as, if not more important than room modes... and then there's also the fact not all room modes are being equally excited anyway in the first place, so... |
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hemster
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Post by hemster on Aug 2, 2016 19:21:18 GMT -5
I would start with a plot of room modes to see where the peaks and valleys are (i.e. points of reinforcements and nulls). See if your seating is on/near a null. As a one-time offer, if you send me your room dimensions (width, height and length) I will send you a plot. The real world room modes can differ substantially from the calculated ones. This is due to rooms not being perfectly box shaped, the rigidity of the walls/floor/ceiling, openings, doors, windows, ducts, a fireplace, alcoves, wall coverings, carpets, rugs, curtains/drapes, furniture... and besides, SBIR is at least as important as, if not more important than room modes... and then there's also the fact not all room modes are being equally excited anyway in the first place, so... ...So, that's why I said that's the place to start, not finish.  |
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Post by garbulky on Aug 2, 2016 19:32:25 GMT -5
Glenn the laptop is unavailable for some time. It is at her school being used for work. The SPL meter I have is designed specifically for frequency response work like this. It's a pretty expensive unit - about 4 x the price of your mic. It's likely going to be more accurate than the mic you are using without calibration data. I think it has multiple options inlcuding b weighting and unweighted but am not sure about it.
But whatever you prefer works, just saying the laptop isn't avaialable right away. Your netbook will likely do fine. Even though it is slow, for audio measurements, it should be a breeze. But likely NOT for correcting an audio signal in real time. That's what REW is used for. For simple audio measurements, the SPL meter and the youtube video I linked is way simpler.
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Post by yves on Aug 2, 2016 19:36:05 GMT -5
Further room treatment may be problematic. Since I plan to sell this house within a relatively few years, I don't plan to make any permanent changes, and any temporary ones must be removable and not require damage to the paint or floors. Cylindrical, free-standing bass traps might be feasible, but there's no sense speculating about what might be needed until I know what the problems (if any) is. I'm relatively convinced that there are NO plus or minus 30 dB nodes in this room. But if there are, they'll be extremely narrow bandwidth. The REW curve will confirm this. The plus or minus 30 dB variations aren't necessarily always nodes, though. Like I said up thread, peaks and nulls in room response are not caused by the effects of room modes alone, but rather, they are caused by the combined effects of both room modes *and* SBIR. www.gikacoustics.com/speaker-boundary-interference-response-sbir/ |
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Post by yves on Aug 2, 2016 19:39:22 GMT -5
The real world room modes can differ substantially from the calculated ones. This is due to rooms not being perfectly box shaped, the rigidity of the walls/floor/ceiling, openings, doors, windows, ducts, a fireplace, alcoves, wall coverings, carpets, rugs, curtains/drapes, furniture... and besides, SBIR is at least as important as, if not more important than room modes... and then there's also the fact not all room modes are being equally excited anyway in the first place, so... ...So, that's why I said that's the place to start, not finish. It's neither a place to start *nor* a place to finish. Its usefulness essentially is limited to educational purposes only.  |
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hemster
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Post by hemster on Aug 2, 2016 19:47:03 GMT -5
...So, that's why I said that's the place to start, not finish. It's neither a place to start *nor* a place to finish. Its usefulness essentially is limited to educational purposes only. Au contraire! Education is the place to start. Don't you read instructions before tinkering? |
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Post by yves on Aug 2, 2016 19:51:36 GMT -5
It's neither a place to start *nor* a place to finish. Its usefulness essentially is limited to educational purposes only. Au contraire! Education is the place to start. Don't you read instructions before tinkering? Nah. Ignorance is bliss IMO! J/K...  |
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klinemj
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Post by klinemj on Aug 2, 2016 20:45:25 GMT -5
But likely NOT for correcting an audio signal in real time. That's what REW is used for. Actually...REW is for measurements. REW will generate information you can input into other devices for doing PEQ, but even that is not correcting in real time via the PC used for measurements. Mark |
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Post by klinemj on Aug 2, 2016 20:47:49 GMT -5
Further room treatment may be problematic. Since I plan to sell this house within a relatively few years, I don't plan to make any permanent changes, and any temporary ones must be removable and not require damage to the paint or floors. Cylindrical, free-standing bass traps might be feasible, but there's no sense speculating about what might be needed until I know what the problems (if any) is. I'm relatively convinced that there are NO plus or minus 30 dB nodes in this room. But if there are, they'll be extremely narrow bandwidth. The REW curve will confirm this. I vote you just build a custom new home now and pay big $ to have the room tuned in perfectly from the start. Why wait? Woulda could shoulda... Mark |
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Post by geebo on Aug 2, 2016 20:57:19 GMT -5
But likely NOT for correcting an audio signal in real time. That's what REW is used for. Actually...REW is for measurements. REW will generate information you can input into other devices for doing PEQ, but even that is not correcting in real time via the PC used for measurements. Mark Real time correction is something that OmniMic can do. You can take readings of their special pink noise files and adjust the PEQ while watching the results onscreen. But it ain't free and you must use the mic that comes with it. |
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Post by Boomzilla on Aug 3, 2016 8:10:13 GMT -5
...The SPL meter I have is designed specifically for frequency response work like this... No, it isn't. The meter you have is designed for use in the workplace to measure ambient noise. It is both expensive and accurate, but the built-in response curves can not be bypassed. The meter is usable for room correction, but an additional calculation will be needed to compensate for the weighting curves. Since weighting curve data is readily available, this won't be a problem.  ...For simple audio measurements, the SPL meter and the youtube video I linked is way simpler. I agree - and it doesn't even require use of a computer at all. It may miss some narrow-range peaks & dips, but should still be usable. So, at your convenience, if you'll be so kind as to loan me that meter, I'll get it on with room measurements. Thanks! |
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Post by KeithL on Aug 3, 2016 10:18:04 GMT -5
The hardware requirements to run REW well will vary..... and will depend specifically on what you're doing. For example, doing a "full up analysis" will take a lot more processing power than just running a meter function. Just running the SPL meter will require much less processing power that running the RTA (real time analyzer). And running the RTA as 1/6 octave takes a lot more power than running it as 1/2 octave. (Usually, if you don't have enough power, it will just run horribly slow - or outright crash - you won't get wrong values.) Most computers are powerful enough to run basic measurements with REW... and it's FREE. Also, while REW is very complicated, and does a lot of stuff.... it's not bad at all if you only want to do one or two simple things. For adjusting EQ in a room, you REALLY do want some sort of spectrum analyzer..... The old way - of making dozens of measurements, plotting them on graph paper, and the figuring out what to correct - is horribly labor intensive. It always takes several passes of "measure, tweak, measure again" - and it takes an awful lot of measurements to get accurate results (1/3 octave means 30 measurements - PER SPEAKER - PER PASS). It's MUCH easier, and more precise, to just play a test tone, look at the graph on the screen, and adjust the sliders until you like what you see. This is ESPECIALLY true if, rather than making the room "dead flat", you simply want to look for and correct significant dips and peaks. To use the RTA in REW, just call up the RTA screen...... (click the red record button on the top right corner to start taking measurements) Note that, for simply smoothing out your room, you don't HAVE to have a microphone calibration curve. It will be more accurate if you have the calibration info, but simply looking for obvious peaks and dips, and removing them, will often still be an improvement. (and many good microphones are at least reasonably flat without correction over the middle of their range). Try it with just the Pink Noise test tones and EQ on the XMC-1 ........ A FEW MORE IMPORTANT NOTES: 1) White Noise should yield a flat graph, while Pink Noise should slope downwards at something like 3 dB / octave (for a flat result). 2) What you're actually measuring with an RTA is "power response" (averaged over some time), and most people agree that a flat response doesn't necessarily sound the best. 3) Some of the measurement methods that use "chirp tones", or other forms of windowing, will produce different results; they're all "useful", but a "flat" response measured using one of them will probably be audibly different than a flat response measured with another, and the difference will vary depending on the room and your speakers. en.wikipedia.org/wiki/Pink_noiseOK - klinemj has convinced me. REW it is. Now a stupid question - Does a netbook have enough guts to run REW or must I have a "real" computer? I can do the latter if I need to, but since the netbook is just sitting around... Is REW smart enough to test the speed / ram of the platform it's running on & say OK or No? |
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Post by millst on Aug 3, 2016 10:38:56 GMT -5
Netbooks are wimpy little PC machines (Windows 7) intended for browsing, email, and light note taking. ARM Dragonball processors & munchkin RAM (512K ?). Probably not REW-ready... I don't need the microphone preamp or USB interface. My audio amigo & tech mentor, garbulky has the goods! Since I don't have a PC laptop (or desktop, for that matter), I either borrow the Gar's or else I run Windows in emulation via VM-Ware Fusion on a Mac. Since I get the impression that REW has to get snuggie with the hardware, it would be best to do this on Gar's Windows machine. Or, (plan B), I can just buy a Windoze laptop at the next garage sale for $25 and make it the "REW machine." Note that this rig isn't something I want to ever admit I even touched, much less kept... When the measurements are over, it's sanoyara to all this measuring junk and I'm back to enjoying music! Just run REW on your Mac. REW is Java-based and supports the major OSes. I'm sure the hardware will be an order of magnitude better than the netbook. -tm |
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Post by Wideawake on Aug 3, 2016 16:08:57 GMT -5
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Post by AudioHTIT on Aug 3, 2016 18:15:31 GMT -5
This doesn't meet your OS requirement, but the easiest measurement software I've seen is AudioTools by Studio Six Digital. It runs on iOS, I have it on both my iPad and iPhone. I think the paid version is $10, but there's also a free one. For measurement it includes both RTA (Real Time Analyzer) and FFT (Fast Fourier Transform) functions, as well as a basic SPL meter and some audio utilities. The RTA does both octave and 1/3 octave, weighted or unweighted, varying decay times, other options - several with FFT as well. For best results you need a calibrated mic, but it includes calibration curves for the built in mic that can do basic measurements - the external mic will only work with Apple devices. Here's a photo with mic Attachment DeletedRTA Screen Shot  FFT Screen Shot  SPL Screen Shot Attachment Deleted |
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Post by Priapulus on Aug 3, 2016 19:56:11 GMT -5
Forget the microphone.
I just use my iPhone and the app "Audiotools" by Studio Six Digital. It can do room reverberation curves, and has Sound level meters,real time analyzers, speaker tests line level measurements, etc. We use it at work all the time.
Sincerely
/blair
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Post by novisnick on Aug 3, 2016 22:57:29 GMT -5
Forget the microphone. I just use my iPhone and the app "Audiotools" by Studio Six Digital. It can do room reverberation curves, and has Sound level meters,real time analyzers, speaker tests line level measurements, etc. We use it at work all the time. Sincerely /blair Is that by Andrew Smith? |
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