Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 45

^^^^ Which reminds me...someone seems to have gone missing for longer than usual!

Quote:

Originally Posted by baniels 

Quote:

Originally Posted by kbarnes701 

Select Ch1 (LF) for the Output and Ch2 (RF) for the Timing Reference Output.

Fantastic, thank you.

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I just received my UMM-6. I had only a few minutes to play with it last night - I was able to get MCH output via HDMI, and got the mic working. Now that I have my cal files from Herb, and the downloaded cal file from Dayton that includes the sensitivity, I thought I'd try to create a text file that matches the format from the UMIK-1 cal file - ie. containing the sensitivity and the CSL cal data.
 

What's this downloadable cal file?  Do I need it?  I thought all I needed was Herb's cal file included with my UMM-6?  Or I am barking up the wrong tree?

Quote:

Originally Posted by jkasanic 

Quote:

Originally Posted by kbarnes701 

The thread is starting now to move on to the next stage as we are getting our mics - the stage of measuring and discussing the measurements and their implications.  If amirm wants to pursue a different objective with legacy REW, then he is free to leave and do so elsewhere. I may be speaking only for myself, but his derailing of threads is not welcome to me, nor is his attempt to change the focus of the thread from the very clear thread title.

 

+1  I tried giving some members the benefit of the doubt as I've just recently become more active at AVS but I can certainly understand why what I've come to regard as highly respected members of the community tend to take such a hard line when it comes to agendas that other forum members continue to push ad nauseam.  I've tried to refrain from commenting but just spending a few months regularly at AVS in various threads, I've started to see patterns developing from certain members (and this is certainly not exclusive to any one member as I've found they are scattered throughout the forum).  I think if you just look through the content of this thread then you can start to draw your own conclusions.  One thing I've learned for sure is that just because a member has a high post count doesn't mean they have any clue about what they're talking about...and vice versa.

You are 100% correct.

Quote:

Originally Posted by AustinJerry 

We sent a copy of the UMM-6 calibration files to JohnM (REW author), and we may see the UMM-6 supported in future REW releases.

When we say 'supported' do we mean that the mic no longer requires the calibration step where you match it to the level shown on the SPL meter?

I haven't found it especially onerous to do that step, but I guess if it is eliminated then so much the better.

OK - I have done a set of initial measurements today, mostly to get the feel for REW. I have to say I am highly impressed at how easy it is, once you have the Windows part set up and also thanks to Jerry's guide. I was also highly impressed at the way one can easily take the different measurements and then examine the graphs in a multitude of ways. It is all a huge step forward from my OmniMic.

I did all of the Jerry-recommended tests today, but limited myself to Audyssey ON at this stage.

Frequency response: this was more or less as expected and broadly in line with my OM graphs. The same problems are there and mostly they are things that I either cannot change or they don't matter all that much anyway. My personal goal with FR is to be +/-3dB across the spectrum and I am not too far from that. I will post graphs later - I want to concentrate on problem areas right now.

Waterfalls: here I have problems. Persistent ringing in the 20-30Hz range. I am investigating more sophisticated room treatments but I am not hopeful of fixing this in such a small room with so many limitations on placement etc.  As above, graphs later. If anyone has any experience or advice on fixing 20-30Hz ringing, I am all ears...

ETC: this is the interesting one for me right now and I would welcome advice from members because this is an area I can actually control. I am posting below the ETC graphs for my front left, front right and centre channels. They are not too bad and the spikes that need attention are, I believe, fixable with additional treatments. (Jerry, you were right about that picture!). I have not done the string test yet but I am fairly confident that the obvious reflection points are the ones causing the issue. I will confirm with the string test but right now I am clean out of string!

One question concerns the sort of treatments I need for these reflections - will GIK's 242s be OK or would I be better off with their 244s, which I am using in the rest of the room?  I would prefer 242s if they are sufficient because they are less expensive and if they do the job then they do the job. OTOH I am happy to spend the cash if 244s are required. Anyone any thoughts?  Jerry, I would appreciate a comment from you especially as I know you also use GIK treatments.

Final problem is one for me - one of the reflection points is bang across the pair of doors which now serves as the sole entrance to the room. These doors are glazed and the room on the other side is our sitting room. Although Mrs Keith is amazingly tolerant, I do not want to push her over the edge, so I have refrained from treating these doors on the HT side even though I have known for some time, intuitively, that they need it. It is easy enough to fix some 242s to the back of the doors, but of course their backsides will be seen from the sitting room. If anyone has any suggestions, again I am all ears.

I would also welcome any other comments on the graphs below as this is the first time I have made ETCs so all help is welcome.  Thanks guys.

Right front, Audyssey ON:

Left Front, Audyssey ON:

Centre, Audyssey ON:

Quote:

Originally Posted by baniels 

The UMM-6 on it's own, as sold by Parts Express, is an individually calibrated mic, as was the EMM-6. We go the extra step of having ours "better" calibrated by CSL. As such, Dayton provides calibration files for the mic's from their web site. This calibration file also includes the sensitivity factor, which is not included with the files we get from CSL. This sensitivity value is essential to getting the native SPL support that is available to the UMIK-1.

Head over HERE. Enter the serial number from your mic. You'll be provided with a link to save a txt file. For giggles you can compare the calibration file from Dayton and that from CSL.

Quote:

Originally Posted by kbarnes701 

What's this downloadable cal file?  Do I need it?  I thought all I needed was Herb's cal file included with my UMM-6?  Or I am barking up the wrong tree?

Ah right - perfectly clear now, thanks.

Quote:

Originally Posted by kbarnes701 

 

 

Waterfalls: here I have problems. Persistent ringing in the 20-30Hz range. I am investigating more sophisticated room treatments but I am not hopeful of fixing this in such a small room with so many limitations on placement etc.  As above, graphs later. If anyone has any experience or advice on fixing 20-30Hz ringing, I am all ears...

 

ETC: this is the interesting one for me right now and I would welcome advice from members because this is an area I can actually control. I am posting below the ETC graphs for my front left, front right and centre channels. They are not too bad and the spikes that need attention are, I believe, fixable with additional treatments. (Jerry, you were right about that picture!). I have not done the string test yet but I am fairly confident that the obvious reflection points are the ones causing the issue. I will confirm with the string test but right now I am clean out of string!

 

One question concerns the sort of treatments I need for these reflections - will GIK's 242s be OK or would I be better off with their 244s, which I am using in the rest of the room?  I would prefer 242s if they are sufficient because they are less expensive and if they do the job then they do the job. OTOH I am happy to spend the cash if 244s are required. Anyone any thoughts?  Jerry, I would appreciate a comment from you especially as I know you also use GIK treatments.

 

Final problem is one for me - one of the reflection points is bang across the pair of doors which now serves as the sole entrance to the room. These doors are glazed and the room on the other side is our sitting room. Although Mrs Keith is amazingly tolerant, I do not want to push her over the edge, so I have refrained from treating these doors on the HT side even though I have known for some time, intuitively, that they need it. It is easy enough to fix some 242s to the back of the doors, but of course their backsides will be seen from the sitting room. If anyone has any suggestions, again I am all ears.

 

I would also welcome any other comments on the graphs below as this is the first time I have made ETCs so all help is welcome.  Thanks guys.

 

Nice progress, Keith!

Regarding the Waterfalls, almost everyone will have issues below 40Hz, and ringing in this range is extremely difficult to fix.  244's won't help at all at that frequency.  GIK makes what they call "tuned membrane" bass traps, i.e. the "Scopus" product, but they are expensive, and it takes quite a few of them to make any difference.  I have no room for these, so I have no personal knowledge of the product.  IMO, ringing at 40Hz and below should not cause too much heartburn for anyone other that someone who has a couple of Submersives.  Wait, don't you have....

If you recall from that other thread I started, I hung an 18" thick piece of R30 insulation over the area I suspected was causing the reflection.  Sure enough, the R30 nipped it in the bud.  Very effective, but not very pretty.  So, I replaced the R30 with two GIK 244 traps, which were not nearly as effective.  This is the time when we would expect Jason to start sharing his knowledge, but unfortunately Jason has been absent for quite some time.  As I recommended to another poster a while back, once you have the measurements and are reasonably sure what the issues are, a call to a company like GIK will usually get you in touch with an expert who can make knowledgeable recommendations.  I have dealt with Bryan Pape, who is their chief acoustics consultant.  And buy some string while you are at it!

As far as the ETC graphs themselves, I see a couple of early reflections that are above the -20dB threshold which should be the focus of your string exercise.  No advice on what to do with the door into the sitting room.  From what I have heard you say about Mrs. Keith, I wouldn't want to jeopardize such a wonderful relationship!

Quote:

Originally Posted by AustinJerry 

Quote:

Originally Posted by kbarnes701 

Waterfalls: here I have problems. Persistent ringing in the 20-30Hz range. I am investigating more sophisticated room treatments but I am not hopeful of fixing this in such a small room with so many limitations on placement etc.  As above, graphs later. If anyone has any experience or advice on fixing 20-30Hz ringing, I am all ears...

 

ETC: this is the interesting one for me right now and I would welcome advice from members because this is an area I can actually control. I am posting below the ETC graphs for my front left, front right and centre channels. They are not too bad and the spikes that need attention are, I believe, fixable with additional treatments. (Jerry, you were right about that picture!). I have not done the string test yet but I am fairly confident that the obvious reflection points are the ones causing the issue. I will confirm with the string test but right now I am clean out of string!

 

One question concerns the sort of treatments I need for these reflections - will GIK's 242s be OK or would I be better off with their 244s, which I am using in the rest of the room?  I would prefer 242s if they are sufficient because they are less expensive and if they do the job then they do the job. OTOH I am happy to spend the cash if 244s are required. Anyone any thoughts?  Jerry, I would appreciate a comment from you especially as I know you also use GIK treatments.

 

Final problem is one for me - one of the reflection points is bang across the pair of doors which now serves as the sole entrance to the room. These doors are glazed and the room on the other side is our sitting room. Although Mrs Keith is amazingly tolerant, I do not want to push her over the edge, so I have refrained from treating these doors on the HT side even though I have known for some time, intuitively, that they need it. It is easy enough to fix some 242s to the back of the doors, but of course their backsides will be seen from the sitting room. If anyone has any suggestions, again I am all ears.

 

I would also welcome any other comments on the graphs below as this is the first time I have made ETCs so all help is welcome.  Thanks guys.

Thanks Jerry. I do feel I made useful progress today. Once all the setup niggles are out of the way, REW is very easy to use. I will post my waterfalls in a day or so - I want to play around with one or two things first. I looked at the tuned membrane traps but, as you say, you need several and I have no room for several! I am not especially dismayed by the ringing centred at 20Hz and 30Hz - it was what I expected and generally I don't hear too much of an issue with it. For music it is more or less a non-event and the only things down there that I listen to are in movie soundtracks and tightness isn't all that much of an issue with explosions etc - and for other effects down there they are often of very short duration (eg gun shots) and they seem to sound very good and powerful even with the waterfalls showing too much overhang. Maybe I am fretting over nothing - this was always an issue with me for measurements and why I held off for so long - they can show me things that I cannot fix because of my room limitations and that can lead to frustration. 

I looked at that other thread yesterday as it happens - it has a lot of useful info in it. String is on my to-do list :)

I am very wary of upsetting her :)  Would 242s be better than 244s for those reflections do you think?  I was intending to order a couple more 244s for the back of the room anyway and I will go ahead with these regardless as they can do no harm there. 242s would look better on the side walls (and the doors!) than the 244s - what do you think?  Do you think those ETCs look OK other than the obvious spikes we just discussed?

^ Keith, I understand you are anxious to fill in the back wall, but you are on the cusp of learning how to analyze your room effectively.  Why not wait a while to make sure your next treatment is the most effective.  For example, the back wall is a common place for early reflections.  My experience is that 244 traps are not very effective in dealing with reflections.  So if you use the remaining space on the back wall and find out that wall is a source of reflections, then where are you?

We have come a long way, and now is the time to apply what we have learned.  Analyze your reflections, and then discuss how to address them.

Quote:

Originally Posted by AustinJerry 

^ Keith, I understand you are anxious to fill in the back wall, but you are on the cusp of learning how to analyze your room effectively.  Why not wait a while to make sure your next treatment is the most effective.  For example, the back wall is a common place for early reflections.  My experience is that 244 traps are not very effective in dealing with reflections.  So if you use the remaining space on the back wall and find out that wall is a source of reflections, then where are you?

 

We have come a long way, and now is the time to apply what we have learned.  Analyze your reflections, and then discuss how to address them.

Thanks Jerry. My back wall is already effectively treated for reflections by the heavy drapes that cover the window behind the MLP. GIK advised me to add a couple more 244s there to deal with lower frequency issues. I agree it coud be a waste of money, even if it does no harm, but I am fairly sure that the spikes in those ETCs aren't coming off the back wall. I won’t buy anything though until my string arrives from Amazon, probably the day after tomorrow.

Are you saying that the 242s are better for reflections than the 244s? I need to know this because I am 95% sure that the spikes shown in the ETCs are from the walls to the left and right of the MLP (one of them with the double doors) and hanging 244s on the walls and doors is not going to look all that great aesthetically, whereas the thinner 242s wouldn't look bad at all. 

Quote:

Originally Posted by lbrown105 

Quote:

Originally Posted by AustinJerry 

^ Keith, I understand you are anxious to fill in the back wall, but you are on the cusp of learning how to analyze your room effectively.  Why not wait a while to make sure your next treatment is the most effective.  For example, the back wall is a common place for early reflections.  My experience is that 244 traps are not very effective in dealing with reflections.  So if you use the remaining space on the back wall and find out that wall is a source of reflections, then where are you?

We have come a long way, and now is the time to apply what we have learned.  Analyze your reflections, and then discuss how to address them.

why would the 244's not be effective at first reflections? I thought they were braod band above 125hz? what are better options?

That was my understanding too. 242s are good for higher frequencies but not so good for the lower ones. 244s are good from about 100-125Hz up as you say. I am wondering if 242s will kill those spikes in my ETCs - they are not too bad (the spikes I mean) and maybe 242s will be fine. 

^ I didn't know you had drapes on the back wall.  If you are talking about 244's in the corner between the back wall and the ceiling for bass control, that sounds appropriate.  I have no experience with the 242's, but according to their specs, they should provide the broadband absorption you are looking for.

Quote:

Originally Posted by lbrown105 


why would the 244's not be effective at first reflections? I thought they were braod band above 125hz? what are better options?

Yes, they are supposed to.  I am only going by my own experiences.  On my back wall where the 18" of R30 effectively tamed the reflections, the 244's didn't do nearly as well.  

Quote:

Originally Posted by AustinJerry 

^ I didn't know you had drapes on the back wall.  If you are talking about 244's in the corner between the back wall and the ceiling for bass control, that sounds appropriate.  I have no experience with the 242's, but according to their specs, they should provide the broadband absorption you are looking for.

Yeah, sorry, I should've mentioned them. I may well get some 242s for experiment purposes. I can either return them or find a use for them one way or another. I doubt if I could ever have too many treatments (realistically) - I am of the view that, for multichannel movies, the room can’t really be too dead simply because any ambience or reflections or sense of space etc are already in the soundtrack. One of the benefits of using the room only for movies and nothing else.

Quote:

Originally Posted by AustinJerry 

Quote:

Originally Posted by jkasanic 

 

@AJ:  Did you by chance happen to download my latest mdat files?  I was curious if you were able to make anything out of waterfall plots?  I've been playing around using the guide as a reference but I'm not sure which sets of measurments are the most meaningful (i.e. sub only, L+sub, R+sub, L+R+sub etc.) for generating waterfalls?  It's pretty clear that I have a major issue at 30 Hz (even with the sub relocated to the mid front wall):

 

 

 

 

 

Well, I'm not a waterfall expert either.  Looking at two measurements (#8 and #17), the first one looks better to me.  Looking at the waterfall associated with #8:

 

 

I see a lot of ringing below ~45Hz.  If you narrow the time window below 600ms, say to 400ms, then the ringing issues persist all the way up to 80-90Hz.  Bass treatments may help here.  However, I would focus on the 10dB dip from 90Hz to 160Hz before doing anything else.  That is a pretty important frequency range, which provides "bottom" and "punch".

Thanks for the feedback.  I understand based on your response to Keith that ringing in the 30Hz region may be tough to deal with so is that another reason (besides the bottom and punch) that I should focus on the 90-160Hz region?  What effect, if any, do you think I could expect Audyssey to have in this region?  My previous OM mic results with Audyssey engaged (not sure why I didn't take the Audyssey measurements again when I had the UMM-6 out the last time!) seemed to improve this region if I'm interpreting the graphs correctly (unfortunately, these are the measurements where I forgot to measure L+R+Sub so I only have R+sub, L+Sub and C+Sub).  Or is this just wishful thinking on my part??

Left+Sub no Audyssey

Left+Sub with Audyssey

Right+Sub no Audyssey:

Right+Sub with Audyssey:

Center+Sub no Audyssey:

Center+Sub with Audyssey:

Quote:

Originally Posted by RUR 


Keith, try running band-limited ETC's to find the offending frequency range(s).

Testing for understanding:  by bandwidth-limited ETC measurements, do you mean run several frequency sweeps using different ranges, generating the ETC graphs, and observing which range of frequencies are causing the reflections?  Are there any prescribed frequency ranges?  What about 500-1,000Hz, 1,000-2,500Hz, 2,500-5,000Hz, 5,000-10,000, and 10,000-20,000?  Is that too granular?

BTW, here are the absorbtion stats for GIK 244 bass traps:

Below about 80Hz, they really are not very effective, and above 1kHz, they are not truly "broadband" absorbers.  So, they do the most good in the 80Hz-1kHz range.

So far, we have only bentioned velocity absorbtion treatments.  Is anyone using a diffusion product?  Also, GIK panels can now be ordered with a "scatter plate", which adds diffusion characteristics to their absorbtion panels.  Interesting, but in what situation would this be useful?

Quote:

Originally Posted by jkasanic 

 

Thanks for the feedback.  I understand based on your response to Keith that ringing in the 30Hz region may be tough to deal with so is that another reason (besides the bottom and punch) that I should focus on the 90-160Hz region?  What effect, if any, do you think I could expect Audyssey to have in this region?  My previous OM mic results with Audyssey engaged (not sure why I didn't take the Audyssey measurements again when I had the UMM-6 out the last time!) seemed to improve this region if I'm interpreting the graphs correctly (unfortunately, these are the measurements where I forgot to measure L+R+Sub so I only have R+sub, L+Sub and C+Sub).  Or is this just wishful thinking on my part??

 

 

What you are seeing between 20-40Hz is similar to what I am seeing between 20-30Hz. I had Audyssey ON for all my measurements yesterday. Reason is I wanted to see the results as I would actually be listening, ie with Audyssey ON. I can see the value and purpose of doing measurements with Audyssey OFF and will do those next time I have the mic out.

My waterfalls are much smoother across the top of the mountains than yours, but I do get a fairly flat frequency response, so that may account for that. I fear that Jerry is right and that I will not ever be able to get rid of the resonances at 20-30Hz no matter what I do, short of moving house. HST, it does sound very good.

Quote:

Originally Posted by RUR 

Quote:

Originally Posted by kbarnes701 

I am wondering if 242s will kill those spikes in my ETCs - they are not too bad (the spikes I mean) and maybe 242s will be fine. 

Keith, try running band-limited ETC's to find the offending frequency range(s).

Quote:

Originally Posted by AustinJerry 

Quote:

Originally Posted by RUR 


Keith, try running band-limited ETC's to find the offending frequency range(s).

 

Testing for understanding:  by bandwidth-limited ETC measurements, do you mean run several frequency sweeps using different ranges, generating the ETC graphs, and observing which range of frequencies are causing the reflections?  Are there any prescribed frequency ranges?  What about 500-1,000Hz, 1,000-2,500Hz, 2,500-5,000Hz, 5,000-10,000, and 10,000-20,000?  Is that too granular?

Well, you're at least one chapter ahead of me there, Jerry :)  If RUR would confirm that is the way to do it, I will give it a go.

Quote:

Originally Posted by AustinJerry 

BTW, here are the absorbtion stats for GIK 244 bass traps:

 

 

Below about 80Hz, they really are not very effective, and above 1kHz, they are not truly "broadband" absorbers.  So, they do the most good in the 80Hz-1kHz range.

 

So far, we have only bentioned velocity absorbtion treatments.  Is anyone using a diffusion product?  Also, GIK panels can now be ordered with a "scatter plate", which adds diffusion characteristics to their absorbtion panels.  Interesting, but in what situation would this be useful?

Speculating here, but above 1kHz you don't need the absorption to be as effective do you, due to the very small wavelengths?  Isn't this why a 242 is effective at the higher end but nt as effective as a 244 at the lower end? I would welcome enlightenment as I am not even sure what the coefficient of absorption means (as is probably obvious).

Quote:

Originally Posted by sdurani 

Quote:

Originally Posted by AustinJerry 

Testing for understanding:  by bandwidth-limited ETC measurements, do you mean run several frequency sweeps using different ranges, generating the ETC graphs, and observing which range of frequencies are causing the reflections?

If you can get past the authors 'not knowing what the E in ETC stands for', then this is the guide I would recommend:

http://www.hedbackdesignedacoustics.com/files/QuickSiteImages/AMS_for_Stereo_List._Rms.pdf

First read section B (pps 5-9), then go back and start from the begining.

Ah yes - this was the document which, IIRC, Jason took a little umbrage at as he said that it was not the best idea to give 'absolute' values as we will all have different objectives and different room models in mind. Personally, I find this sort of document immensely useful at my current level of understanding - I think I need to be told things like 'resonances from 35Hz-300Hz should not extend beyond 350ms before decaying into the noise floor or reaching a level of -40dB. Below 350Hz this standard is relaxed to 450ms'.  I like the idea of a 'target' to aim for even if it is less than ideal. Some target is always, IMO, better than no target at all.

The paper is concerned with stereo reproduction which is the least of my concerns, my room being for movies only, and the room sizes they use are very different to my room, so I will need to be somewhat circumspect in my interpretation of the 'targets' - but I understand those caveats and am prepared to try to accommodate them. I have printed the paper out and put into my binder along with Jerry's Guide. Thanks for reminding me about this one, Sanjay.