Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 22

I personally think addressing noise/hum is very important as it could and does easily skew measurements and the whole point of the measurements is to make our systems better. If we don't first take care of getting the absolute lowest noise floor both electrically and acoustically, then we have already limited the results we'll be able to expect.

Plus it's pretty easy.

But the real reason is because I just made a novel of a post and did it when I should be sleeping and I'd hate to have to delete it lol.

Great point, Stuart.

I am one of those users. I have a dedicated HTPC and always have my test rig hooked up as I'm measuring "something" just about every day so it's extremely important to isolate and fix any noise/hum issues.

I think it's important to start from the ground up and it doesn't get lower than the noise floor. Okay, bad attempt at a joke, but a clever person could find one in there somewhere.

--J

Hi BP,

You can absolutely use the RS meter for measurements. Surprisingly, it is pretty darn accurate and is great for relative measurements. It's best to only trust the results from about 20hz to about 3khz though. From 3khz to 7khz it's "ok" but not great and it's pretty useless above 7khz or so.

It gets a bad rap for some reason, but I started with one, have tested several, and they honestly aren't bad and a great, easy, and inexpensive way to get started.

You do NOT need a pre-amp.

However, you should use a Line Input on your computer/sound card and not a Mic input because the RS meter is powered and the mic input will cause too much boost/noise since it's used for non-powered (IE: Audyssey mic) inputs.

All you have to do is plug the RCA cable into the meter and on the other end get an RCA to 1/8" (3.5mm) mono adapter to plug into your computer.

That's it as far as input goes. The output cabling doesn't change and you can still use analog or HDMI.

I wouldn't trust the calibration files that are floating around though.

You'll be able to do everything with the RS meter that you can do with any other calibrated or uncalibrated mic, but I wouldn't make tough (read: expensive) decisions based on the readings on anything other than a calibrated mic from CSL.

It's perfect for relative measurements and will get you in the ballpark for absolute measurements up to around 3khz, so go for it!

--J

Hi Michael,

You DO NOT use a pre amp when using a Radio Shack SPL Meter. Without going into detail, I'm surprised you were able to get this to even work reliably and without all kinds of issues.

The RS meter should be plugged directly into the computer's sound card. No additional hardware is required or recommended.

As far as output, you can still use analog/headphone out or go with HDMI if you wish, but the RS meter should be plugged directly into a "Line In" connection on your computer's sound card.

--J

Hi Jerry,

First of all, you're right... I need to learn not to assume and am still getting used to giving advice on public forums where I am not in direct control or at least have knowledge of what my advice might lead to in the real world. Point taken, I apologize, and I'm glad you didn't hurt your speakers or your ears.

While it isn't necessarily imperative you take all measurements at 100db, it truly is important to get 60db above your noise floor if you want truly accurate and absolute measurements.

My recommendation is not for everyone to take all measurements starting at 100db, even if it came across that way before. (Who knows, I might have even specifically said to do that in my haste without further explanation and if I did, for that I also apologize.)

This is yet another reason why it is so very important to start with the absolute quietest noise floor possible.

I realize not everyone is going to tear down and start over with true isolation and room inside a room construction nor is everyone going to feel comfortable taking 100% of their measurements at 60db above whatever their noise floor is.

There are some very good reasons for doing this, though.

Once you "think" you're finished with speaker/listener placement, treatments, etc, and you want to see how you did and what your absolute measurements are (assuming you have a properly calibrated at 90 degree mic) THEN you must measure 60db above your noise floor to be able to trust the measurements.

Even then you'll always want to take two or three measurements in EACH mic position, moving the mic several times just as you did when running Audyssey, and you want to do this with Audyssey on and off, too.

You'll quickly fill up the 30 maximum measurement slots in REW this way, with each session, but it's the only way to get trustworthy measurements.

Max brought up some very good points and tips too, and got to it a few days before me. Sorry again for being so slow.

You can start out at 75-80db and then move up in 5db increments, not only to at least 60db above your noise floor, but until you start seeing compression, which will simply look like measurements that don't show 5db louder when you did indeed turn the volume up 5db (frequency response graph for this one). Once that happens, the measurement directly under it is the loudest your system can comfortably play without compression/distortion/who knows what else.

If you can't get to 105db (115db for subs) then you need to move your speakers closer, get new amps, new speakers, or simply not listen so loud.

Once you measure, again do this in 5db increments, and find the maximum clean level you can play, subtract this from your noise floor (most rooms in the US will be somewhere around 40-45db if not treated) and that is your dynamic range. It WILL be a far cry from those extraordinary Dynamic Range specs on all your awesome gear, which is one good reason why you shouldn't base your decisions on which gear to purchase based on this figure, THD, etc, as ALL modern gear (and most older gear) is going to outperform what you can get in room anyway. That's why I always "listen" to gear, in my room if possible, before deciding what to buy and only based unseen/unheard purchasing decisions based on features I want as I know my room is the limiting factor for ANYTHING I could buy.

It is important to know the dynamic range of your room though and it is important to get your room as isolated from outside noise as possible. For certain types of music, IE: Classical, that can go from very quiet to very loud and back to very quiet again in a second, and do this over and over, it is critical you have the largest dynamic range possible or you'll surely miss a lot of what is on the recording.

This is yet another reason why people always fiddle with the remote turning things up and down. I can ASSURE you that if you have the volume set to a reasonable level and ever have to "turn it up" to hear what he/she said, your room is too noisy.

Moving on, besides knowing how your equipment performs and the dynamic range of your room, it's also important to measure loud because it will show any resonances you have. These could be coming from your speakers themselves, light fixtures, items in your room, even your acoustic panels! You don't want to hear these buzzes/rattles when your watching/listening to content and this is the only way to surely excite them and be able to fix them.

Don't worry about the graphs you posted. Something is obviously wrong. When changing the volume, you always need to recalibrate REW, especially the SPL. It's always a good idea to click the "calibrate" button in the REW preferences and just run through the steps, also doing the same thing with the SPL meter in REW just to be sure all the levels are set right. Once you recalibrate everything and have made sure there are no noises/buzzes/rattles in your room when your taking measurements, start back around 80db, moving up 5db at a time, taking 2 or 3 readings without moving the mic at all in between them, and look at the waterfalls. Once you find where these funky graphs start showing, post them again, and I'll have a look. We'll figure this out. I'm SURE this isn't indicative of what's truly going on in your room, since I'm pretty familiar with your actual room.

So for folks reading this, yes, it's important to measure 60db above your noise floor for absolute measurements.

However, always wear ear protection and get there in 5db increments, and of course don't ever measure above the limits of your system.

For every day measurements though, not for ones you're posting here, when you've just tried this or that, something small, and just want to see if it had an effect on your FR or Waterfall, or possibly when you're trying to find a point of reflection with the ETC, it is not necessary to measure this loud and somewhere around 85db is fine.

I personally only measure that loud when I feel I've done the best I can do setting up a room/system with what I have to work with that day and the time I have, to show the absolute and accurate results of my efforts.

REW does have noise filtering built in and you won't "necessarily" start seeing nothing but noise starting exactly where your noise floor begins.

For instance, Jerry, I believe your noise floor was measured at 57db, right? (I'd recalibrate the SPL meter, make sure everything is as quiet as possible, do it late at night when it's quiet outside too, and verify that - it seems like a very high noise floor and 57db is actually pretty bad. I don't trust that measurement.) If you look at your waterfall graphs, you're not going to see nothing but noise starting right at 57db.

This is another good reason to use a very long sweep, too. Always set your measurement sweep length to 1 pass, but a MINIMUM of 512k and preferably 1mb for the most accurate measurement sweeps to get rid of the most noise.

TIP: A good way to see the limits of REW's noise filtering is to look at a Waterfall somewhere in the range of 500hz up to 10khz and then click the "Limits" button, clicking the "bottom" limit down, down, and down some more, until you start seeing "mountains" appear out of nowhere. In the range of 500hz to 10khz or so, we know these aren't actual modes or modal issues, so it's certainly noise.

Next, wherever your noise starts to appear in the graphs, set your permanent "bottom" limit a few DB above this and you'll know you aren't looking at your noise floor, but you are seeing how long it takes for each actual mode to decay TO the noise floor, as actually measured by REW and its noise filtering algorythms. This way you don't have to rely on an actual SPL measurement which can be flawed, especially if just a few frequencies are loud while the rest is much quiter.

Finally, use 60db above that level as your actual measuring level when you wish to make absolute/accurate measurements. You'll likely find that most of the time, in most situations, you won't have to measure much above 90db or so, especially if you have a reasonably quiet room and don't live in Midtown Manhattan.

Hope this clears some things up for some folks.

Keith/Jerry, I believe the info/tips in both this post and the one about noise/hum should be added to "A" document sooner or later, whether it be a FAQ or "other" document as this is some important info, especially since it concerns possible damage to speakers and humans. Just a note so hopefully you guys can bookmark these posts for later compilation.

Thanks,

--J

Sorry for the delayed response. Better late than never, right?

Please see my answers above, bolded, in between your questions.

Hope this helps,

--J

Hi Nyal,

We haven't had the pleasure of meeting or speaking before. Although I don't know you and am not familiar with your work, I know Jeff and his work very well and respect him very much.

I'd love to have further conversations with you since we don't exactly have the largest pool of acousticians and acoustical consultants to pick from when seeking new friends with our common interests.

With that being said and with all due respect, I must humbly disagree with several recommendations your white paper recommends, though.

I actually did read the paper shortly after you published it, but didn't give it too much thought as at the time it didn't concern me or affect anything I was personally involved in and I'm definitely not one to criticize just to stir up trouble.

If you will kindly read the first page (second post) of this thread, you'll see that I started this thread to help people set goals and work towards achieving them regarding the acoustics of their listening rooms.

I've offered my time and participation in this thread to give back to this community for all the invaluable information and knowledge I've received from this forum and forums like it over the last several years.

I know what it's like to spend a lot of time reading, learning, and then through further research and way down the line find out I was given so much misinformation that I have to try and unlearn and then start all over relearning things the right way and I want to try to teach people the "right" way from the beginning.

The problem is, "right" isn't necessarily fully defined unless your goal includes an acoustical model in which you are trying to achieve.

The first main post of this thread states just how critical it is to set this goal as otherwise, what exactly are we working towards?

Once one has chosen an acoustical model, there are absolute guidelines that are in place to assure certification spelled out in great detail as to what each of the parameters your white paper has mentioned above should actually be, and quite frankly a lot of what you state is simply not supported by these models.

I understand that most people reading this thread and planning on taking measurements and applying treatment to their rooms aren't going to have them LEDE certified for instance, but I strongly believe you must set a goal and have specific ideals to work towards if you ever hope to accomplish anything close to what you set out to do.

In the second post of this thread, I recommended, and for those reading this, am recommending again, that you all read this fine document that details each of the most popular room models from which to choose then pick one to model your own room after. http://www.eetimes.com/design/audio-design/4015907/Acoustics-and-Psychoacoustics-Applied--Part-1-Listening-room-design

Another great article comparing the different acoustical models is from RPG and it goes into even more detail yet is very well written and easy to understand. http://www.rpginc.com/docs%5CTechnology%5CPresentations%5CStudio%20Design%20From%20Mono2Surround.pdf

The point is that this thread is geared towards learning what the different acoustical models are, picking one (setting that as the ultimate goal) then working towards achieving it, starting with learning how to use REW and progressing through all the different graphs and functions of REW, what they mean, how to interpret them, and what to actually "DO" about whatever problems your room has so you can achieve your initial goal.

We're obviously in the very beginning of this process with most here not even having their mic's yet and very few folks are comfortable using REW past very basic measurements and I'm sure it will be quite some time before we get into intricate details on exactly what some of these parameters are and how they'll end up in most folks rooms.

With all that being said and understood, I have to say I believe your white paper can very easily confuse people and deter them from following the proper steps already set in place to participate in this thread.

I suppose what I mean by that is that your white paper is simply arbitrary targets that don't adhere to any standard, especially any standard for an actual and proven room model which people have built and use either to record or for critical listening.

If there were no standards then this would be fine.

Since the whole purpose of this thread is for folks to pick an existing and well proven standard acoustical model, most of which I assume will work towards LEDE/RFZ or NE standards, what exactly do you hope to accomplish here by posting "your" targets?

I mean no disrespect at all and welcome you to continue participating in this thread as I know the knowledge you have was not easily attained nor did it happen overnight. I also know you have surrounded yourself with folks whom I deeply respect and admire, so you're not all bad... But I have to say, I do discourage folks from selecting these arbitrary numbers/targets you've set, at least until you can explain exactly what you're trying to accomplish with them.

Are you suggesting a new acoustical model? Are these the targets for this new model? Why do you feel we need a new model/targets? What's wrong with what we have to choose from?

I don't believe the many different acoustical models (which accommodate many different needs and purposes already) need to be changed as they have all worked quite well and are proven and have been around for many years. Do you?

I'm not trying to be rude or harsh, but I just want people to learn the "right" way to begin with. Most of these folks probably have no idea who Don and Carolyn Davis are and don't know of Trevor Cox's work, or Manfred Schroeder, and all the other pioneers in acoustics. They may have heard of Floyd Toole (whom I also admire and respect, but...) who has his own ideas which are very different from the norm on reflections and the ISD for instance. Most of the folks on this thread aren't going to read the text books that we read/have read and aren't in this due to their passion for acoustics and furthering their education.

Most folks (I'm assuming again) are here to learn how to measure their rooms and make them sound better/perform better.

We've done the hard work and have amassed a lot of information over the years but we have to be very careful in how we disseminate it as it is very frustrating to try and unlearn or relearn something, sometimes to the point that one simply gives up or worse yet, doesn't know they have learned "wrong."

So to keep it "right" I am going to specify exactly what I disagree with and I welcome you to let me know why it is you made the recommendations you did in your white paper and what you're trying to accomplish by changing the standards already set in place long ago that have been working quite well for everything from recording/mastering studios to critical listening rooms for several decades now with few updates/changes to the models in which they're based.

First, why do you feel the ETC should show "10db reduction by 40ms?" Do you not believe in an ISD Gap? Do you not believe early reflections high in amplitude are destructive? Do you not believe in the termination of the ITG?

LEDE standards are pretty clear that energy should not be above -20db from 0 to "around" 20ms or so to create an effectively anechoic gap which is then strongly terminated to increase the apparent size of the room and so the direct signal has time to form free of clutter. This will reduce muddiness and improve the listening experience with absolutely no argument against doing this from most well respected people in the field. What would the purpose of having a ton of high energy reflections all the way out to 40ms only 10db down be?

Second, you reference RT60, 30, 20 yet there is absolutely NO REVERB TIME in Small Acoustical Spaces!! I'm SURE you know this. You stated these targets you set were for two-channel and you may amend them for home theater so this paper was obviously not written for concert halls, yet you reference taking RT measurements!

While looking at modal decay times and insuring they are even and contained to the appropriate range for the size of the room and the actual proven acoustical model targeted is necessary you won't find it by looking at the RT60 nor will that measurement help for the mid-hi frequencies either.

You can simply use the ETC and Cumulative Spectral Decay plot to find decay times and setting specific decay targets without taking into consideration the model, the room, etc, in my opinion is far from ideal.

You suggest targeting between .2 and .5 seconds with not much more explanation than that, but that is a HUGE difference. A room that has an overall average decay time of .2 seconds will sound quite dead no matter the size, especially considering you stated this document was created with two channel in mind, whereas with HT you'd at least have the surrounds so .2 wouldn't be so dead and dry, yet .5 in small rooms can be WAY too long. So have you defined specific targets for specific rooms in this new model of yours? What are the "why's" behind these numbers or are they just arbitrary limits you selected?

Next, you suggest a +/- 10db FR in the low frequencies at 1/24th smoothed! That isn't much of a goal! First, low frequencies should NEVER be smoothed at all. We need to see all the resolution possible here. Second, a 20db swing is worse than most people that have taken 5 minutes to "try" will ever see, especially now that RC software like Audyssey is now so popular. Anybody that would actually be reading your paper or this post is not going to accept a 20db swing in the most important frequency band in the audible spectrum whether 1/24th, 1/48th, or totally unsmoothed, which is the only way the FR should be viewed in this range.

The effects of what you've recommended here are much more devastating than those of what you recommended for the ETC.

As for decay times, should not the target be simply as even throughout the entire audible spectrum as possible with as little deviation as possible?

Again, it may not be likely that everyone will be able to get to within 10% of the full spectrum regarding decay times like the BBC demands for its rooms, but if you don't set the goal and understand the importance of ringing and vastly different decay times, especially in the lower frequencies, then your "critical" listening room is going to sound pretty bad.

Nyal, I know reading this probably upsets you and may even come across as preachy or arrogant but I assure you the intent of this reply is nothing more than an attempt to keep everyone on the same page and encourage them to read up on the TRUE - ACTUAL Acoustical Room Models that are proven with specific targets that which rooms have been built to for decades now.

There is no reason to invent the wheel. The information is out there. The acoustical models we have now work. I'm simply trying to condense as much of the information that is already out there as possible and slowly work through each step in this thread so that in the end, or at least months down the road, other folks will have a reliable source to visit and learn correct and proven factual information so they too can hopefully achieve acoustic nirvana.

I actually agree with all the points in your white paper that I didn't specifically call out, and there are more things I agree with than I don't, but some of the things I don't agree with are critical to the acoustical response of a room and quite frankly are too "easy" and I'd bet a lot of people reading this thread are already within most of your specified targets.

Sorry for this novel of a post and sorry if you take offense to this. I've not once written one post in my tenure at AVS that I feel is likely to offend anyone, yet I'm afraid this may be my first, although I honestly assure you that the education and enjoyment of the readers of this thread are all I truly care about and I wish to preserve the integrity of this thread and all of the masters of this industry that paved the way and wrote the true manuals for us to achieve the best listening rooms possible.

I do hope we can talk again under more pleasant circumstances and get to know each other.

Also, as I'm sure regular readers of this thread have figured out, I am a few days behind as I'm launching a new company soon and just don't have the time I wish I had to dedicate to this thread right now, so if you reply, I may be a bit behind on getting back with you but rest assured I will respond.

Thanks,

--J

Well Stuart,

If you're in Chicago, in a high rise, in a Condo, with thin walls and can't make noise, you're screwed.

Honestly, you can only do what you can do. If all you can comfortably do is 85-90 then so be it.

It's not like your measurements are going to be invalid.

They just won't be "absolutely" accurate. You'll still get a VERY GOOD idea of what's truly happening in your room if you can measure at 90db though, I promise.

Also, remember, if you're in the middle of changing things around, moving MLP/Speakers, adding/moving treatments, etc, and are simply measuring in between each change to see what effect it had, measuring around 75-80db is just fine.

This goes for everybody, no matter what their noise floor is or how loud they can measure. I measure at 85db regularly even though I have a 35db noise floor as right now I'm testing some changes I made recently.

When I test the effects of new diffusors and reflectors I'm designing I do the same thing. When I design a new bass trap and test it though, you better believe I'm measuring with a full 60db to work with, though.

It just depends on what you're doing and what the measurements are going to be used for/how accurate you need them to be.

I hope people are not absolutely shocked when they see the difference between RS meters, Audyssey Mics and their new $100 calibrated mics because unless something is actually physically wrong with the mics, there honestly shouldn't be a "huge" difference over most of the frequency band.

What you're getting with the calibrated mic is peace of mind. You know for a fact it's accurate. That's worth $100 to me!

Same thing with measuring louder... More accurate but not going to be totally different than measuring at more reasonable levels, however, much more important in the bass/modal range.

Hope this helps,

--J

Hi Keith,

I promise you that most of your measurements, most of the time, are going to be perfectly fine at 90db or even 85db. (Wouldn't go lower than that though)

You should absolutely verify the limits of your system to calculate your dynamic range as I stated in a previous post (which Max beat me to; again ) and when you have made a major change or feel you're "done" with treatments, at the end of class, (and maybe for mid-terms too) when you're ready to put this thread away forever, that's when you need to measure at 100db (in your case, since your noise floor is actually 40db) but in between, which is most of the time, when you just want to compare one measurement to another to see what effect that last change you made had, measuring at a reasonable level such as 85db is more than adequate!

Don't even think twice about this again. I promise you it's fine.

I actually stated exactly this in one of my previous posts, but it was buried in one of my novel posts since I had so much to cover and catch up on while I was sick with the Flu

Since you're so great at writing and putting things together, maybe you can pull this part (as it's sure to be on a lot of people's minds) and also the tip I gave about using REW noise filters to your advantage and checking the actual noise floor as shown in a waterfall graph by looking at higher non-modal frequencies, and maybe put a new post together in your words which are much more eloquent (and shorter) than mine. I know there are some good tips and some gems in there but I also know I use way too many words to get my points across and things get buried. I need to work on that, but if everyone will bare with me, I promise you I'll eventually get better, but I doubt I'll ever be able to write like you and Jerry.

Don't you love how every time I answer one of your posts I volunteer you for more work?

--J

Sorry Jerry, I didn't see that question. I really do try to answer every question I see that hasn't already been answered. I'll just have to look harder. Let me know if I've missed anything else.

Narrow band simply means more point of measurement/comparison than 1/3rd. It's just like viewing an unsmoothed vs 1/3rd octave smoothed FR.

You definitely want to use the narrow band files for REW as we'll mostly be viewing at high resolution unsmoothed or maybe 1/48th smoothed for higher frequencies.

If you look at the difference (in the same measurement) between a FR graph that is unsmoothed and 1/3rd smoothed you'll see that the comb filtering in the higher frequencies shapes the 1/3rd graph differently and artifacts can cause the 1/3rd graph to not be as accurate.

The 1/3rd files are used on equipment that doesn't have high resolution. For instance, if you use an actual Real Time Analyzer that maxes out at 1/3rd octave then the most accurate results would be to use the 1/3rd cal file as it takes into consideration the smoothing you're using to provide more accurate data.

If you really want to get anal about it ("I" don't even do this) you could load the narrow band for all unsmoothed down to 1/24th smoothed and load the 1/3rd file for when you're looking at 1/3rd smoothed graphs, but since 1/3rd smoothed graphs are absolutely useless and I won't be recommending we use them AT ALL, I see no point.

It's just that Herb doesn't know who will be using software like REW and who will be using specific hardware solutions with built in RTA's at 1/3rd, so he is thorough enough to provide both.

Hope that clears it up for you,

--J

I'm a HUGE baby and PITA when I'm sick and believe me, you all should be very happy I wasn't around in the last few days as I know for sure my family wishes that.

You know, since Jerry has done such a great job and has gone into so much detail I do feel his guide would be a good place for the FAQ's and TIPS.

I must admit, I feel like a lot of the tips I've written and a lot of the information (not all the words in between, but the actual info lol) will be coming up again and again and I do wish you and/or Jerry could/would go through my last several posts and pull out the actual pertinent information (which should be rather obvious to pick out) and if nothing else, copy it to a notepad of some kind for future inclusion in the guide because I just know a lot of this stuff is going to start coming up soon, especially since the mics are on the way. (Funny thing is I don't know if I made it into the first batch of UMM-6's yet!! Plus, as soon as I get one I have to send it off to John for inclusion in REW so I'm not even going to have one of these for awhile lol)

Anyway, thanks for everything, Keith... I most definitely could not get this thread going and keep it going without you and Jerry. I really mean that. With the little time I have and sometimes not being able to get on here for a few days, then being sick recently, I do at least feel between you two everyone is in great hands and you all can hold the fort down until I come back.

I have some exciting things to announce soon which will hopefully be of use to most in this thread and hopefully soon I will have a little more time open up to where I can at least get back on here regularly every evening, at a minimum.

For now though, I must head to the office for even more acoustics fun!

See ya,

--J

Cool beans... I was just talking to Keith and have to admit I do feel there are several nuggets from my latest few posts (especially the long ones) that I feel would be pertinent to the guide.

What is your opinion on a separate faq vs adding some of the tips and other bits o' info to the guide you've already created?

I don't want to intrude or alter what you've set out to create, and I do appreciate all you do very much, but if you have time would you mind going through today's posts and possibly grabbing the tips, tricks, how-to's, etc for possible inclusion into, if not your guide, some type of document? I just put way too much "noise" in between all the good info and I'm afraid not everyone is going to read the long posts... See, I can't even make a simple request without turning it into a novel.

Thanks Jerry,

--J

Here's what I can do.

I have a lot of knowledge of the different targets for the different room models and even know which few most here are going to pick to model.

I do not have a lot of time right now nor quite frankly do I have the skill that you guys have in creating documentation.

I can give you the info for a LEDE/RFZ room and for a NE room that Nyal gave for whatever he calls his "model" and if you have the time, patience, and skill (I'm only sure of the last one) to help translate my hard data into the pretty guide/graph then as a team we can finally get this "Correct" information out to the masses so they don't have to read textbooks and study for years like a few of us have.

I STRONGLY suggest reading the seven page article I linked to and downloading RPG's paper that both explain the different room models and targets, though.

I really hope everyone does this and then selects one. It's the absolute first step. If we can't get folks to do this then I don't see how we're going to move past the "how to use REW" which is coming up next, because after that we should all be working on specific goals to accomplish a specific model to get known results that many many people are happy with.

Tell me what you don't understand or what you'd like more of from those two documents so I can get a few opinions and start crafting the beginnings of a more thorough document and compile more information for a simple chart/graph folks can quickly refer to along the way (like Nyal made) to check their rooms against the actual targets.

If you guys can do that and help me help you, I promise to spend the time to compile all relevant information and I know between you two, the end result will be easy to read and very worthwhile.

Thanks a bunch,

--J

Hi John,

Great to see you over here!

I hope you'll subscribe and stick with us.

BTW, I plan to send you a UMM-6 mic as soon as the backorder comes in in the next week or two.

Of course, you are right and you were more specific than I was.

Again folks, read my latest posts and see that I do not recommend taking all your measurements at that level and John has given you yet another way to calculate a level to take "regular" measurements at.

Between his example above and my previous example in looking at the noise floor of the higher (non modal) frequencies in the waterfall you should be able to easily find a happy medium that is both loud enough but also doesn't damage your ears or equipment.

I must reiterate though, IMO it "IS" important to measure 60db above the noise floor at least twice. Once to see the limits of your equipment and where compression and distortion start to go into full swing and if ever a time comes when you feel you are truly done tweaking the acoustics of your room.

I'm sorry I wasn't this specific in the beginning and you guys got the idea I recommended taking 100db+ measurements every single time, but at least we got the man himself to join our discussion, right!

Thanks again John, for all you do.

I'm sure you realize by now, with the latest improvements to REW a lot more people will be using and enjoying your software and I sure hope others remember to kindly donate to the cause as John has put countless hours into making REW free for all of us and asks for nothing in return. REW is quickly becoming (I believe it already has) the most powerful acoustical measuring software available and it does all it does, for free!

--J

Keith,

Your request is simple enough and I think I can accomplish what you want. I won't have the time to make it pretty like Nyal did, but I can and will compile all the raw information and send it to you and/or Jerry to work on because if I post it here, not only will it not be pretty but it will surely also be too wordy.

BTW, MHOA is a wonderful book and is the first one I read, too! It is definitely not comparative to a first grade reader. Once you read, then re-read, and start applying some of the things you learned in MHOA you'll find that most other text books are on specific subject matter and are more of expansions on specific chapters in MHOA.

For instance, for anyone interested in making their own acoustical treatment instead of buying it (it's actually great for folks buying, too, as just because you own something doesn't mean you know how to use it/where to place it) I strongly recommend THE BOOK, "Acoustic Absorbers & Diffusers" by D'antonio and Trevor Cox of RPG. These folks "LITERALLY" wrote the book in this case and brought us LEDE, developed QRD Diffusors, and have done so much for us, and a lot of it is just given away in that book... All you have to do is read it.

It just depends on how far you want to take your knowledge, how passionate you are about acoustics, and what you want to do with the knowledge you gain.

I fully understand most people haven't viewed the field of acoustics and psychoacoustics their hobby and passion for several years as I have and most people don't want to read all the posts in this thread let alone textbooks on the subject, so I will try to compile some data and if you and/or Jerry can put it in an easy to read/understand form like Nyal did, all the better.

The info IS there. It's different for each model and there are ranges and there are of course caveats which we can explain in the thread in more detail and as the questions arise, but there is no reason we can't start by getting the criteria for a certified LEDE room out there and even offer some examples and projects along the way, as I personally have both of those.

I'll work on this but don't expect it "today."

As for your room, no, with the size of your room, you probably won't be able to get it LEDE Certified, but you'd never try to do that anyway. None of us would since we are critical music listeners and not recording studios. However, there is no reason you cannot "approach" a LEDE room. You won't get a 20ms ISD Gap but with the proper compromises and the proper treatment, as long as you're willing to invest the time to gain the knowledge, you can get very close. A few compromises a room your size will most likely end up with is around a 10ms ISD Gap and a relatively even modal decay rate that is longer in time than the mid-hi range which we'll have to be very careful to not overdeaden but it can be done and in fact HAS been done.

There is a great thread by a member called Lupo, over on Gearslutz (I "think" that's his name - will have to look up the thread when I get back tonight) who lives in Europe, has a very small room, and he has achieved LEDE without a million traps through clever use of reflection and diffusion with a moderate amount of bass trapping. He shows pictures and his ETC's along the way and the result is quite nice! So you can do it, but you'll only get out of it however much you put into it.

Hope this helps, and I'll be back this evening to talk more.

See ya,

--J

Sorry Jerry, I thought I saw a measurement of yours showing the SPL reading from REW and it showed 57. I must be thinking of someone or something else.. Was only going from memory, and a bad one at that.

40db is pretty normal for a quiet house.

Even if it sounds dead quiet to you it's reading around 40db because of lower frequencies that have long wavelengths that also travel far and aren't audible at that level.

You won't get it much below that without working on your transmission loss levels and the only way to do that unfortunately is construction. Your situation is very common which is why in fact "most" people's noise floor is right at 40db. I've put a TON of work into my room, everything short of building it all over again, and I've only gotten to 35db so don't feel bad. It's a ton better than the 57db I thought you had!

If you truly want to know what you could do to lower it more and improve your dynamic range and get the most out of your listening experience, I'd be happy to discuss it with you, but be forewarned, it's a lot of work and will cost a bit of money, too.

Let me know,

--J