Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 100 - AVS Forum
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post #2971 of 12859 Old 05-26-2013, 09:26 AM
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Originally Posted by AustinJerry View Post

Jim,


And what is the "Filtered IR" tab in REW good for?  Anyone?

The filtered IR in REW does something similar to what I was showing in Omnimic with the sliced ETC curves (just got through playing with it to see what it does)

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post #2972 of 12859 Old 05-26-2013, 09:26 AM
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Turning the fan on should break up the reflections enough to not matter to the listener.

If the fan is not used he could remove the blades.

A minisplit unit would provide HAC (no "V) if an outside wall is available and a place to mount the inner and outer units. I did that in my media room, both foir climate control and to isolate the room from the house ducts.

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post #2973 of 12859 Old 05-26-2013, 10:03 AM
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Originally Posted by sdrucker View Post

More seriously, speaking of compromises, Keith:

I've taken a measurement break to determine what my next move will be, based largely on reading your and AustinJerry's adventures on the REW thread. I realized that while I'm getting more proficient in using Audyssey Pro + Target Curve editor to get a reasonably flat (1/6th, i.e. the audible level) FR response for mains+subs and as good as I'm going to get for the center+subs (and not too shabby waterfalls at 600 ms), I don't know much about impulse response at all.

Also, thinking about room treatments, I've got to get the hang of the string test and pick an acoustic model to go further. Worse than that, our room is problematic: instead of side walls, we have a short mirrored area and entrance to the hallway/dining room on the left, and a full side of windows on the right. To top that off, the front of the room is where the speakers and TV are, co-located with an 72" wide and high entertainment center, and in the back, we have a large piece of artwork on the back wall. Not much room for treatments either side.

Having said that, unless I get WAF to make furniture compromises (and just wait till we see what the bassinet and baby play stuff will do to early reflections in the fall!), outside of maybe ceiling treatments and PEQ, I may be out of luck outside of 'suffering' with an electronic-based solution.

That's actually why I started lurking on some of the Trinnov threads and 'dreaming big', BTW.

You know, I was perfectly happy with my old Klipsch reference system, a KSW-10 sub, and a Denon 5803 with no RC until I discovered AVS, and I fell into this rabbit hole thanks to the now-absent ccotenj, who's busy restoring 70's-era pinball machines instead of this stuff. Geez, thanks guys cool.gif

 

I've been on an extended break for a few weeks. I was spending far too much time on acoustics and not nearly enough time on watching movies (my true passion). I realised that a lot of the time I was chasing graph differences that didn't necessarily translate into audible differences, so I called a (temporary) halt. I will go back to measuring again at some point though as there are still things I want to address and also things I have learned along the way that I want to experiment with.

 

Is Chris active on a 70's Pinball thread somewhere? LOL...

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post #2974 of 12859 Old 05-26-2013, 11:19 AM
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Originally Posted by kbarnes701 View Post

I've been on an extended break for a few weeks. I was spending far too much time on acoustics and not nearly enough time on watching movies (my true passion). I realised that a lot of the time I was chasing graph differences that didn't necessarily translate into audible differences, so I called a (temporary) halt. I will go back to measuring again at some point though as there are still things I want to address and also things I have learned along the way that I want to experiment with.

Is Chris active on a 70's Pinball thread somewhere? LOL...

Beats me....but from a few emails we've exchanged and FB pictures, he's certainly thrown himself into it whole-heartedly. I think he just decided he got bored, and/or reached a point of diminishing returns with measuring as a hobby.

You know, sooner or later you'll watch too many movies and want to tweak reflections or bass slam....your time will come LOL tongue.gif...

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post #2975 of 12859 Old 05-26-2013, 11:22 AM
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Originally Posted by Selden Ball View Post

Installing central air conditioning would be one way to eliminate the overhead fan. Of course, it'd be quite a bit more expensive.

I have a very modern and efficient central A/C system. A ceiling fan keeps air circulating all the time, increasing comfort level. Without one, the A/C would need to be set 2-3 degrees lower to achieve the same comfort level. Remember, we are talking about weather that exceeds 100 degrees for 30-60 days of the year.
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post #2976 of 12859 Old 05-26-2013, 11:22 AM
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Originally Posted by DonH50 View Post

Turning the fan on should break up the reflections enough to not matter to the listener.

If the fan is not used he could remove the blades.

A minisplit unit would provide HAC (no "V) if an outside wall is available and a place to mount the inner and outer units. I did that in my media room, both foir climate control and to isolate the room from the house ducts.

Just imagine--seasonal calibrations (and room treatments)! Good thing that Jerry's 4520 has save/load tongue.gif

I'm mostly kidding, AJ.

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post #2977 of 12859 Old 05-26-2013, 11:24 AM
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Originally Posted by AustinJerry View Post

And what is the "Filtered IR" tab in REW good for?  Anyone?
Did you call? smile.gif It is a useful feature of REW and lets you properly determine if you have enough total absorption in your room or too much. It is the logic behind "RT60" measurement. You use the filtered IR to properly focus in the mid-frequencies where speech occurs and hence the impact reverberations can have on its intelligibility. Contrary to statements made otherwise in this regard, this measure is valid for our listening spaces (and if it is not, you can determine that using Filtered IR). For an exhaustive proof of this, and examples of how filtered IR is used, see this post I wrote in GS forum: http://www.gearslutz.com/board/8887203-post397.html

For more examples and less math, see this thread that was the origin of the argument that dragged into GS forum: http://www.avsforum.com/t/1453370/do-bass-traps-produce-noticeable-audible-difference/90#post_23024737.

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post #2978 of 12859 Old 05-26-2013, 11:59 AM
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Originally Posted by sdrucker View Post

You know, sooner or later you'll watch too many movies and want to tweak reflections or bass slam....your time will come LOL tongue.gif...

 

LOL. I am sure you are 100% right, Stuart.  Meanwhile, I am getting this pleasure vicariously, from following Jerry's latest journey...

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post #2979 of 12859 Old 05-26-2013, 12:11 PM
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Originally Posted by kbarnes701 View Post

LOL. I am sure you are 100% right, Stuart.  Meanwhile, I am getting this pleasure vicariously, from following Jerry's latest journey...

Me too. One rainy weekend afternoon when nobody's home, I'll pull out REW and do some IR and other ETC plots, cut some 20-40 foot string (Audyssey puts my L/C/R distances in the 18-19 ft. range), and go reflection hunting on the ceiling and maybe the mirrored leftside wall or a limited area on the back wall. But I don't think I can cover a side of windows looking out at Lake Shore Drive, Lake Michigan, and Monroe Harbor with acoustic panels frown.gif. Life is tough.

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post #2980 of 12859 Old 05-26-2013, 12:48 PM
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For more examples and less math, see this thread that was the origin of the argument that dragged into GS forum: http://www.avsforum.com/t/1453370/do-bass-traps-produce-noticeable-audible-difference/90#post_23024737.
Hi Amir,

Took a quick look at the first post. It says:

>>The origin of Reverberation Time is from Wallace Clement Sabine who around 1890 performed a ton of experiments in his basement to see how long it would take for sound to decay 1,000,000 times once it is shut off. Expressed in dB, we get 60 dB which happens to also be the sound level of a human.<<

I'm confused by that. If a sound decays by 60 dB, that has nothing to do with how loud it was before it was shut off. So what has that ratio got to do with the typical loudness of human speech?

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post #2981 of 12859 Old 05-26-2013, 01:05 PM
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Hi Amir,

Took a quick look at the first post. It says:

>>The origin of Reverberation Time is from Wallace Clement Sabine who around 1890 performed a ton of experiments in his basement to see how long it would take for sound to decay 1,000,000 times once it is shut off. Expressed in dB, we get 60 dB which happens to also be the sound level of a human.<<

I'm confused by that. If a sound decays by 60 dB, that has nothing to do with how loud it was before it was shut off. So what has that ratio got to do with the typical loudness of human speech?
I am not sure I am understanding your question so this may be the wrong answer smile.gif. Clarifying what I said anyway, RT60 is the decay of 60 dB. Human speech at 1 meter is said to be 60 dB SPL. So a 60 dB decline can be said to be the time it takes for human voice to reach 0 dB SPL. This may have been justification after the fact though. What we know is that Sabine was interested in measuring decay of 60 dB. And clearly then as you state, if the level is above 60 dB to start, we will not be 0 db SPL.

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post #2982 of 12859 Old 05-26-2013, 01:30 PM
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Quote:
Originally Posted by kbarnes701 View Post

LOL. I am sure you are 100% right, Stuart.  Meanwhile, I am getting this pleasure vicariously, from following Jerry's latest journey...

Me too. One rainy weekend afternoon when nobody's home, I'll pull out REW and do some IR and other ETC plots, cut some 20-40 foot string (Audyssey puts my L/C/R distances in the 18-19 ft. range), and go reflection hunting on the ceiling and maybe the mirrored leftside wall or a limited area on the back wall. But I don't think I can cover a side of windows looking out at Lake Shore Drive, Lake Michigan, and Monroe Harbor with acoustic panels frown.gif. Life is tough.

 

Sometimes, the pursuit of aural perfection has to take a back seat. I'd say that this was one of those times :)

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post #2983 of 12859 Old 05-26-2013, 01:49 PM
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Quote:
Originally Posted by amirm View Post

For more examples and less math, see this thread that was the origin of the argument that dragged into GS forum: http://www.avsforum.com/t/1453370/do-bass-traps-produce-noticeable-audible-difference/90#post_23024737.
Hi Amir,

Took a quick look at the first post. It says:

>>The origin of Reverberation Time is from Wallace Clement Sabine who around 1890 performed a ton of experiments in his basement to see how long it would take for sound to decay 1,000,000 times once it is shut off. Expressed in dB, we get 60 dB which happens to also be the sound level of a human.<<

I'm confused by that. If a sound decays by 60 dB, that has nothing to do with how loud it was before it was shut off. So what has that ratio got to do with the typical loudness of human speech?

 

I looked at the post you linked in the quoted part of your reply, Roger.  Clearly, a decay of 60dB has nothing at all to do with the actual level at the end of the decay time. let alone the level of the human voice. The level post-decay could be anything, depending on the starting value as you say. 

 

But I found some pure gold further on in the post:

 

"Imagine you are playing a movie and [the] actor says the word “hat.” We have three distinct parts to that with different loudness levels: “h,” a” and “t.” Let’s say it takes one second to pronounce “hat.” That means each part of it roughly takes 1/3 of a second or ~0.3 seconds. In our sample room we had a reverberation time of 0.8 seconds. This means that the pronunciation of “h” lasts another 0.8 seconds after it stops. That 0.8 seconds then overlaps the rest of the word. That may make it harder to hear the softer (in level) parts of that word. We may think the person said “had” instead of "hat." If we shortened our reverberation time to say, 0.2 seconds, the chances of that happening becomes much smaller and intelligibility improves." (My bolding.)

 

This is so far from being correct, as anyone who has studied any form of linguistics would appreciate, that it really is pure gibberish. I imagine it has been included as some form of justification of the view that we require certain types of reflections in order for speech to be rendered intelligible (let's pretend for a moment that headphones had never been invented, or if that is a stretch too far, that speech played back through headphones, being totally lacking in any form of reflected sound from the room, is always therefore going to be unintelligible wink.gif). As we know, the research that goes to support the view that we require reflections for speech intelligibility was conducted in rooms such as classrooms where the increased level may indeed have rendered speech more intelligible, but which is not required in a typical playback environment where we can raise level with that pesky little doohickey, the volume control. 

 

If anyone has difficulty differentiating the word "hat" from the word "had" I suggest they get out their earphones and play it again. Then I suggest they actually try speaking the two words out loud - when they do so they will appreciate that the entire phoneme is different between the two words - not simply the last consonant. The quoted (and especially the bolded) text is pure, unadulterated bunkum.

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post #2984 of 12859 Old 05-26-2013, 01:55 PM
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Sometimes, the pursuit of aural perfection has to take a back seat. I'd say that this was one of those times smile.gif

I had a smaller tradeoff when I bought our Panny 55" VT50. For years, we were limited to a 43" physical width for a TV, because we had a 44" cavity in our entertainment center. Last fall I broke down and got the VT50, and picked up an external TV stand (with staggered, open shelves) and a vertical mount for the plasma to fit it properly. However, the stand sits outside the entertainment center by necessity, and my powered center channel now rests on the top shelf with open space above it.

The practical implication is that instead of my mains and center being roughly horizontally parallel to one another, the center is now about a foot physically closer to the MLP than the mains (which can't be moved without having them bump up against furniture or an AV stand). I can't say (using OmniMic at the time) that the FR after rerunning Audyssey Pro was much different - certainly the crossovers were identical, and if anything CC dialogue is a little clearer - but I've wondered if that 'live bass' perception in the center of the room may have taken a slight hit due to changes in reflection pattern as a result. Maybe I should get the REW sooner rather than later after all. But I'd still rather have the bigger Panny.

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post #2985 of 12859 Old 05-26-2013, 02:11 PM
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Me too. One rainy weekend afternoon when nobody's home, I'll pull out REW and do some IR and other ETC plots, cut some 20-40 foot string (Audyssey puts my L/C/R distances in the 18-19 ft. range), and go reflection hunting on the ceiling and maybe the mirrored leftside wall or a limited area on the back wall. But I don't think I can cover a side of windows looking out at Lake Shore Drive, Lake Michigan, and Monroe Harbor with acoustic panels frown.gif. Life is tough.

I envy you, Stuart. Being a Northwestern graduate, I remember that view well. Curtains would tame the window reflections, and allow you to have the view as well, no? You could have a "curtains open" Audyssey calibration, and a "curtains closed" calibration. wink.gif
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post #2986 of 12859 Old 05-26-2013, 02:23 PM
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As we know, the research that goes to support the view that we require reflections for speech intelligibility was conducted in rooms such as classrooms where the increased level may indeed have rendered speech more intelligible, but which is not required in a typical playback environment where we can raise level with that pesky little doohickey, the volume control.
Do you think that intelligibility can be improved such that you find yourself reaching for the volume control less often? Or do you think that's just impossible and that the only way to improve intelligibility is to turn up the volume control?

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post #2987 of 12859 Old 05-26-2013, 02:25 PM
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I envy you, Stuart. Being a Northwestern graduate, I remember that view well. Curtains would tame the window reflections, and allow you to have the view as well, no? You could have a "curtains open" Audyssey calibration, and a "curtains closed" calibration. wink.gif

We have stock adjustable blinds--maybe we can upgrade to 'acoustic blinds', like this:
http://smg-corp.com/products/acoustical-blinds/

Maybe I'll give them a call and get some pricing--but the other side would still be an issue even if I found reflections these blinds might belp.

Anyone try something like this in the States?

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post #2988 of 12859 Old 05-26-2013, 02:35 PM - Thread Starter
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Jerry,

I've been thinking about your ceiling fan conundrum and have a few suggestions for you.

First, you need to make sure it's the blade(s) causing the reflections and not the fan itself, so you can pretty easily/quickly remove the blades and retest without having to remove the whole fan.

Assuming it's just the blades causing the reflections, I've seen all kinds of ceiling fans at my local Lowe's that I believe would work for your situation.

You could replace the ceiling fan (they aren't very expensive and most are less than one GIK panel) with one that has wicker or fabric blades instead of solid wood and that should allow you to keep your fan and get rid of the reflections at the same time.

I'd hate to see you give up now when you've come so far.

Please let me know if you'd like more suggestions, but I at least wanted to get you started thinking outside the box because there are definitely solutions out there for you none of which should cost you your fan, comfort, or a lot of money. wink.gif

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post #2989 of 12859 Old 05-26-2013, 02:46 PM - Thread Starter
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Jim,


And what is the "Filtered IR" tab in REW good for?  Anyone?

The filtered IR in REW does something similar to what I was showing in Omnimic with the sliced ETC curves (just got through playing with it to see what it does)

Jerry et al,

All you have to do to replicate what Jim did in Omnimic is select the "Filtered IR" tab in REW (be sure you've selected the individual channel you wish to look at first and NEVER look at the combined L/R channels together, for instance).

Then you put a check mark in the ETC box.

You'll see the same ETC you see when viewing it the normal way. Be sure to set the parameters the same as normal, viewing from 0ms to about 40ms at the most and be sure you're zoomed in enough to see detail, so it's not all bunched up. I like to take up about 3/4 of my screen or so for enough detail.

Then, near the bottom left hand corner, you will see a selection box that says, "No Filter."

Simply click that box to choose your 1/1 octave filters. Nyal gave some good examples of what to look for and this is one part of his white paper I absolutely agree with.

The thing is, the higher the frequency response you measure, for instance all the way up to 20khz, the more the regular unfiltered ETC will show those higher frequency reflections. So you could easily fool yourself into thinking you have tamed or redirected all the reflections if you don't filter by frequency.

If, for instance, you take a measurement that stops at 5khz then another that stops at 10khz, the ETC's will look totally different.

By filtering and looking at different bands in 1/1 octave, you'll be able to see for sure that you've tamed the whole bandwidth of the reflection.

This way you'll be able to see if your 2", or 4" panel did it's job, or just EQ'd the reflection by only taking out the high frequencies.

This is a good way to see how thick and how large your panel needs to be and not over do it, too.

Bandwidth filtering of ETC's is imperative. I've not mentioned it yet because I wanted to get everyone used to finding reflections and figuring out how to tame them, and nobody has yet to explore redirecting them and/or using diffusers instead of just absorbing them.

I don't want folks to get overwhelmed or confused, so I'm more than happy to try and explain better if this doesn't make sense, but I think you're ready, Jerry. wink.gif

I can see you going all the way with this and having a truly wonderful room, feel your on the way, and am so proud of you and happy that you've seen the light and already heard the difference that extending your ISD Gap makes. It's wonderful, isn't it? cool.gif

Let me know if I can be of further assistance. That goes for anyone looking to tame reflections. This is a good lesson to be sure you are truly using "Broadband" absorbers that really do a full job of taking care of the problem and not just EQ'ing the top end out.

Also, remember, the ETC is for specular reflections so you don't need to be looking at band limited ETC's below 500hz and if you can take care of the reflections from 1000hz and above you're really doing a great job.

--J

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post #2990 of 12859 Old 05-26-2013, 02:53 PM - Thread Starter
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More seriously, speaking of compromises, Keith:


I've taken a measurement break to determine what my next move will be, based largely on reading your and AustinJerry's adventures on the REW thread. I realized that while I'm getting more proficient in using Audyssey Pro + Target Curve editor to get a reasonably flat (1/6th, i.e. the audible level) FR response for mains+subs and as good as I'm going to get for the center+subs (and not too shabby waterfalls at 600 ms), I don't know much about impulse response at all.


Also, thinking about room treatments, I've got to get the hang of the string test and pick an acoustic model to go further. Worse than that, our room is problematic: instead of side walls, we have a short mirrored area and entrance to the hallway/dining room on the left, and a full side of windows on the right. To top that off, the front of the room is where the speakers and TV are, co-located with an 72" wide and high entertainment center, and in the back, we have a large piece of artwork on the back wall. Not much room for treatments either side.


Having said that, unless I get WAF to make furniture compromises (and just wait till we see what the bassinet and baby play stuff will do to early reflections in the fall!), outside of maybe ceiling treatments and PEQ, I may be out of luck outside of 'suffering' with an electronic-based solution.


That's actually why I started lurking on some of the Trinnov threads and 'dreaming big', BTW.


You know, I was perfectly happy with my old Klipsch reference system, a KSW-10 sub, and a Denon 5803 with no RC until I discovered AVS, and I fell into this rabbit hole thanks to the now-absent ccotenj, who's busy restoring 70's-era pinball machines instead of this stuff. Geez, thanks guys cool.gif

I've been on an extended break for a few weeks. I was spending far too much time on acoustics and not nearly enough time on watching movies (my true passion). I realised that a lot of the time I was chasing graph differences that didn't necessarily translate into audible differences, so I called a (temporary) halt. I will go back to measuring again at some point though as there are still things I want to address and also things I have learned along the way that I want to experiment with.

Is Chris active on a 70's Pinball thread somewhere? LOL...

Keith,

If you're making changes and not hearing differences, something is wrong/causing that.

If you could post your ETC's and updated FR and Waterfalls, I'd be happy to take a look and give you some pointers. As always, a pic of the room/layout would help, too.

You mentioned you were working towards an NE model, so let's see the results and see if we can help you get there. There's always room for improvement.

Personally, my passion is acoustics, understanding and applying, and the science of it. I spend so much more time reading, learning, and tweaking my own theater/system than I do listening/watching, but only because I enjoy that aspect even more than I do watching movies!!

I totally understand if this journey in acoustics for you is a means to a different end goal, which is total enjoyment of your movie watching, but again, if you cannot hear differences when you add/change treatment, something is wrong with that picture and that's a for sure sign that you may have overdone/over dampened your room, so let's break out the charts and graphs! wink.gif

--J

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post #2991 of 12859 Old 05-26-2013, 02:58 PM - Thread Starter
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Hi Amir,

Took a quick look at the first post. It says:

>>The origin of Reverberation Time is from Wallace Clement Sabine who around 1890 performed a ton of experiments in his basement to see how long it would take for sound to decay 1,000,000 times once it is shut off. Expressed in dB, we get 60 dB which happens to also be the sound level of a human.<<

I'm confused by that. If a sound decays by 60 dB, that has nothing to do with how loud it was before it was shut off. So what has that ratio got to do with the typical loudness of human speech?
I am not sure I am understanding your question so this may be the wrong answer smile.gif. Clarifying what I said anyway, RT60 is the decay of 60 dB. Human speech at 1 meter is said to be 60 dB SPL. So a 60 dB decline can be said to be the time it takes for human voice to reach 0 dB SPL. This may have been justification after the fact though. What we know is that Sabine was interested in measuring decay of 60 dB. And clearly then as you state, if the level is above 60 dB to start, we will not be 0 db SPL.

T60 is the amount of time it takes for sound to decay 60db, no matter what the start db level is.

RT60 is used in Large Acoustical Spaces and does not apply to our types of rooms as we don't have a reverberant field.

Not everyone speaks in a monotonous tone all at the same SPL. I cannot believe that anyone would believe that human speech is 60db at 1 meter. This makes no sense.

So much of this information is wrong and contested by individuals with much higher and more specific credentials than myself, but how exactly does any of this "mis" information apply to anyone's question here or help them in any way??

--J

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As we know, the research that goes to support the view that we require reflections for speech intelligibility was conducted in rooms such as classrooms where the increased level may indeed have rendered speech more intelligible, but which is not required in a typical playback environment where we can raise level with that pesky little doohickey, the volume control.
Do you think that intelligibility can be improved such that you find yourself reaching for the volume control less often? Or do you think that's just impossible and that the only way to improve intelligibility is to turn up the volume control?

 

I don't know, Sanjay, as I have zero issues with intelligibility and never have to reach for the volume control in order to make dialogue intelligible (not that I said that I did of course). But I do know that reflections are not required for dialogue to be intelligible, and I do know that dialogue is intelligible when listened to through headphones where there is clearly no possibility of reflections being an aid to intelligibility. I also know linguistic gibberish when I see it - if the issue of reflections and intelligibility is a real one, it shouldn't need pure bunkum to make the point, should it?

 

I do not doubt that in a classroom the teacher's dialogue might be rendered more intelligible if reflections are allowed or even encouraged. But this is because the reflections raise the level of the dialogue. As I said, we don't need to do that in playback rooms because we have the volume control as the means of raising the level. If the dialogue is unintelligible because it's not loud enough, then the volume control represents an easy and universal solution.

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As we know, the research that goes to support the view that we require reflections for speech intelligibility was conducted in rooms such as classrooms where the increased level may indeed have rendered speech more intelligible, but which is not required in a typical playback environment where we can raise level with that pesky little doohickey, the volume control.
Do you think that intelligibility can be improved such that you find yourself reaching for the volume control less often? Or do you think that's just impossible and that the only way to improve intelligibility is to turn up the volume control?

Not Keith but....

The most common problem relating to dialog intelligibility in my opinion has less to do with reflections than one may think and a lot more to do with available dynamic range which is hindered in most residential living spaces by a high noise floor.

I never have to mess with the volume control in my dedicated and properly treated room. I realize a lot of folks listen above ground (I have a dedicated theater in a basement) in a standard living room or extra bedroom and have to contend with windows and non-sealed rooms, so the noise floor (and therefore the dynamic range) will have to suffer, but in that case, there's not a whole lot you can do other than use some of the new technologies by Audyssey, Dolby, et al.

I'm not saying that controlling early reflections (key word there is controlling, as there are a lot of things you can do with them) isn't key, but it definitely isn't the only thing to consider and quite frankly I'm not convinced that it is even the most important aspect to consider regarding intelligibility of speech in reproduction of dialog on movies.

Decreasing your noise floor and increasing your dynamic range is imperative to good speech intelligibility.

--J

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So much of this information is wrong and contested by individuals with much higher and more specific credentials than myself, but how exactly does any of this "mis" information apply to anyone's question here or help them in any way??
 

 

It doesn't. Misinformation might assist in the selling of 'high end' equipment though. Certainly misinformation must be the main sales aid for 'magic cables' for example. And if a salesman can persuade someone that a hugely expensive amplifier will contribute to hugely better sound, well, that's a given too. 

 

When someone tries to tell you that the 'word' "hat" has "three distinct parts (sic) to it with different loudness levels", it's time to run for the hills ;) (I put the word 'word' in quotes because the written word and the spoken sound of the written word are two distinct phenonema.)

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Jerry,

I've been thinking about your ceiling fan conundrum and have a few suggestions for you.

First, you need to make sure it's the blade(s) causing the reflections and not the fan itself, so you can pretty easily/quickly remove the blades and retest without having to remove the whole fan.

Assuming it's just the blades causing the reflections, I've seen all kinds of ceiling fans at my local Lowe's that I believe would work for your situation.

You could replace the ceiling fan (they aren't very expensive and most are less than one GIK panel) with one that has wicker or fabric blades instead of solid wood and that should allow you to keep your fan and get rid of the reflections at the same time.

I'd hate to see you give up now when you've come so far.

Please let me know if you'd like more suggestions, but I at least wanted to get you started thinking outside the box because there are definitely solutions out there for you none of which should cost you your fan, comfort, or a lot of money. wink.gif

--J

Good suggestions, J. I'm pretty sure it is the blades causing the reflections, since I can get varying reflection intensities by simply rotating the blades. You are correct--removing the blades and re-measuring would be a simple exercise. More difficult would be selecting a replacement fan assuming that its blades would be less reflective, installing it, and then finding it to be reflective as well.

I understand now how early reflections can adversely affect the sound in our listening rooms. However, I don't think I have developed "golden ears", meaning that if there were a magic way to run an A/B comparison with and without a particular early reflection, would I be able to immediately tell the difference? In other words, what does an early reflection sound like?

Maybe I will just have an electrician give me a quote to move the ceiling fan out of the center of the ceiling....
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post #2996 of 12859 Old 05-26-2013, 03:09 PM
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I am not sure I am understanding your question so this may be the wrong answer smile.gif. Clarifying what I said anyway, RT60 is the decay of 60 dB. Human speech at 1 meter is said to be 60 dB SPL. So a 60 dB decline can be said to be the time it takes for human voice to reach 0 dB SPL. This may have been justification after the fact though. What we know is that Sabine was interested in measuring decay of 60 dB. And clearly then as you state, if the level is above 60 dB to start, we will not be 0 db SPL.
Thanks for the reply. I'm still a little confused, because 0 dB SPL has no significance in a discussion of intelligibility.

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In other words, what does an early reflection sound like?

You could listen to a room that doesnt have any wink.gif

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post #2998 of 12859 Old 05-26-2013, 03:15 PM
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I've been on an extended break for a few weeks. I was spending far too much time on acoustics and not nearly enough time on watching movies (my true passion). I realised that a lot of the time I was chasing graph differences that didn't necessarily translate into audible differences, so I called a (temporary) halt. I will go back to measuring again at some point though as there are still things I want to address and also things I have learned along the way that I want to experiment with.

Is Chris active on a 70's Pinball thread somewhere? LOL...

Keith,

If you're making changes and not hearing differences, something is wrong/causing that.

If you could post your ETC's and updated FR and Waterfalls, I'd be happy to take a look and give you some pointers. As always, a pic of the room/layout would help, too.

You mentioned you were working towards an NE model, so let's see the results and see if we can help you get there. There's always room for improvement.

Personally, my passion is acoustics, understanding and applying, and the science of it. I spend so much more time reading, learning, and tweaking my own theater/system than I do listening/watching, but only because I enjoy that aspect even more than I do watching movies!!

I totally understand if this journey in acoustics for you is a means to a different end goal, which is total enjoyment of your movie watching, but again, if you cannot hear differences when you add/change treatment, something is wrong with that picture and that's a for sure sign that you may have overdone/over dampened your room, so let's break out the charts and graphs! wink.gif

--J

 

Thanks J. What I meant by that remark was, for instance, when I was obsessing about my waterfall graph showing some ringing down at 20Hz or less. I was obsessing about this when someone mentioned that I might be suffering from graphitis nervosa and pointed out that the initial impulse is pretty hard to hear at below 20Hz, so the chances of hearing anything at 30 or 40dB below that would be more or less zero. So this seems to be something that it would be less than rewarding to try to fix - sure, I'd get a better looking waterfall, but if I can't actually hear any difference, what's the point? 

 

There's also the issue with my room that it is so small that it is very hard to make any changes - speakers and seats, for example, are all but fixed here, unfortunately. When I decide to get back to measuring etc you can be sure I will be seeking your help to make my fledgling NE room even more NE!

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You could listen to a room that doesnt have any wink.gif

I'm trying, Jim! rolleyes.gif I'm also trying to avoid false steps that cost money.
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post #3000 of 12859 Old 05-26-2013, 03:24 PM
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As we know, the research that goes to support the view that we require reflections for speech intelligibility was conducted in rooms such as classrooms where the increased level may indeed have rendered speech more intelligible, but which is not required in a typical playback environment where we can raise level with that pesky little doohickey, the volume control.
Do you think that intelligibility can be improved such that you find yourself reaching for the volume control less often? Or do you think that's just impossible and that the only way to improve intelligibility is to turn up the volume control?

Not Keith but....

The most common problem relating to dialog intelligibility in my opinion has less to do with reflections than one may think and a lot more to do with available dynamic range which is hindered in most residential living spaces by a high noise floor.

I never have to mess with the volume control in my dedicated and properly treated room. I realize a lot of folks listen above ground (I have a dedicated theater in a basement) in a standard living room or extra bedroom and have to contend with windows and non-sealed rooms, so the noise floor (and therefore the dynamic range) will have to suffer, but in that case, there's not a whole lot you can do other than use some of the new technologies by Audyssey, Dolby, et al.

I'm not saying that controlling early reflections (key word there is controlling, as there are a lot of things you can do with them) isn't key, but it definitely isn't the only thing to consider and quite frankly I'm not convinced that it is even the most important aspect to consider regarding intelligibility of speech in reproduction of dialog on movies.

Decreasing your noise floor and increasing your dynamic range is imperative to good speech intelligibility.

--J

 

I too never have to mess with my volume control to make dialogue intelligible. I live in the middle of the English countryside in a tiny village surrounded by farms and fields -- and I watch movies late at night (after 10pm) when things are even quieter (I am blessed with Mrs Keith who can -- and has -- slept through an earthquake). My house is a modern build so it has very effective double glazing, cavity wall insulation etc etc that does tend to keep noise out fairly well. This would tend to support the view that a low noise floor is a valuable aid in this regard. I also cite headphones: if reflections are necessary in order to render dialogue intelligible then the time when we would struggle most is when listening via headphones, but this does not happen.

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