m00n Posted September 30, 2003 Share Posted September 30, 2003 For those of you interested, artto has been helping me start my room acoustics. Here is one of his posts that started what you could call my first task at really determining my room problems and how to fix them... This came from this thread Ports on the RF7s up in technical questions... For a bit of background. ======================================================================= artt's original assignment Moon, first let me say that some of the most renown auditoriums in the world have been gutted & acoustically redone because some nit wit architect thought he could predict the acoustical performance before it was built. And these are large spaces that are actually easier, in some ways, to deal with. Its my personal perspective that measurements should be used as a confirmation to test the results, rather than a starting point to analyze the situation. You are absolutely correct that every seat is going to have a bit of a difference in frequency response and that I will never get them identical. Regarding: doesn't it make sense to have a fair amount of absorption? Seems like without it, I am getting a lot of extra reflections going on. Its not the amount of reflection thats important, per se. The best sounding halls in the world have plenty of reflection. Lots of it. The main difference here is that the time difference between the direct sound from the speaker (verses live music in a large hall for instance), and the first reflections of that sound, are very small. In a larger hall or room, the first reflection takes much longer to reach your ears compared to the initial direct sound. Once this time difference gets too small, the human ear/brain can no longer distinguish between the reflected sound & the initial direct sound. Notice I said distinguish, not that it cant hear the sonic result. The initial result, as our ears hear it and our brain analyzes it, is a smearing of the sound. Loss of detail. Sound localization becomes more difficult. Now I must admit that I have very limited experience with HT & surround sound systems where there are additional multiple channels, primarily to carry ambient & sound effects information. And the room in your case, as you already know, is not proportioned well, & it is a on the small side. These combination of factors may very well point to using more absorption than what would be usual in a typical 2 or 3 channel stereo setup. However, the same principals still apply (albeit, maybe to a different degree). BROADBAND still applies. So, with all of this in mind, lets start at first base. What I want you to do is take your SLM (sound level meter) & using your favorite sounds or a test recording with pink noise & white noise, is go to the middle of the room & note the sound level, both from the meter, and subjectively, how it sounds. Does it seem to lack bass? Is it fine? Etc. Then go to the rooms far right & left rear corners, mid height & do the same thing. Let me know what you come up with. ======================================================================= I did 2 types of testing. One was using my AVIA Home Theater DVD, the second was listening to the music of David Arkenstone's Quest of the Dream Warrior. @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ TEST TONES USING AVIA DVD @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ WB Asynchronous Pink Noise tests. =============================================== Volume: -35 Channels: 5 Center seat front row: 72db Center seat middle row: 71.5db Left corner of room: 72 db Right corner of room: 71.5 db SPEAKER BALANCE - FRONT LEFT =============================================== Volume: -35 Channel: Front Left Center seat front row: 65db Center seat center row: 64db Center seat rear row: 62db Left corner of rom: 64db Right corner of room: 64db SPEAKER BALANCE - CENTER =============================================== Volume: -35 Channel: Center Center seat front row: 64db Center seat center row: 62db Center seat rear row: 62db Left corner of rom: 61db Right corner of room: 61db SPEAKER BALANCE - FRONT RIGHT =============================================== Volume: -35 Channel: Front Left Center seat front row: 65db Center seat center row: 64db Center seat rear row: 61db Left corner of rom: 64db Right corner of room: 63db @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ MUSIC LISTENING RESULTS - David Arkenstone Quest of the Dream Warrior @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Results Center Seat Front Row =============================================== Louder More Detail Narrower sound sage Results back left seat =============================================== Wider soundstage A tad muddier More bass response Sometimes seems boomy Results back right seat =============================================== Smoother bass response Just a little less volume in bass output than the left seat Wider soundstange than front center seat General comments on music test. ================================================ The further back I got from the speakers, I definitly noticed the soundsage just widen way up. in the back row, it seemed like my room was 20 foot wide, where as in the front row, my room sounded much narrower. There is definitly a trade off between front and back. Front is more detailed, but does not sound open. The back sounds much more open but not as full, mids don't seem as strong as the front row. Quote Link to comment Share on other sites More sharing options...
artto Posted September 30, 2003 Share Posted September 30, 2003 OK. Good start. Although you didn't quite do what I asked. So let's continue. Using the broad band pink noise, measure (objectively) & listen (subjectively) (making notes as previously stated) at the usual 'sweet spot' or best listening/viewing position, which is probably near the center of the room. Then do the same thing in the right & left REAR corners of the room (not at the seats) , at mid level between the floor & ceiling. Then do the same thing with some kicka$$ music. We're just looking for relative averages here. This is not a 'test'. Quote Link to comment Share on other sites More sharing options...
m00n Posted September 30, 2003 Author Share Posted September 30, 2003 ---------------- On 9/30/2003 1:32:15 PM artto wrote: OK. Good start. Although you didn't quite do what I asked. So let's continue. Using the broad band pink noise, measure (objectively) & listen (subjectively) (making notes as previously stated) at the usual 'sweet spot' or best listening/viewing position, which is probably near the center of the room. ---------------- What do you mean by measure objectively and listen subjectively? Quote Link to comment Share on other sites More sharing options...
artto Posted September 30, 2003 Share Posted September 30, 2003 Measuring IS the 'objective' part of this exercise (not a test). Listening IS the 'subjective' (opinionated) part. Don't ask so many questions right now, or we'll never get thru this. Quote Link to comment Share on other sites More sharing options...
m00n Posted September 30, 2003 Author Share Posted September 30, 2003 I am just trying to ensure that I understand what you want, cause I didn't give you what you wanted the first time. Quote Link to comment Share on other sites More sharing options...
DrWho Posted September 30, 2003 Share Posted September 30, 2003 lol! btw, i hope you don't mind me watching all of this...im hoping i might learn something too i think arto wants you to listen in the corners of the room because that's where the "absorbtion crap" is gonna go...if there's no bass in the corners, then what's a bass trap gonna help? Quote Link to comment Share on other sites More sharing options...
dbflash Posted September 30, 2003 Share Posted September 30, 2003 m00n and Artto I hope you don't mind me listening in on your conversation. I am going to be rebuilding my HT den for 2 channel only. I have wanted to do many on the technics that Artto did to his room. I know I never will get it to come any where close to his, but I am going to try. "OK. Good start. Although you didn't quite do what I asked. So let's continue." m00n what exactly did Artto ask you do do? m00n if it makes you feel any better alot of what Artto mentions is over my head too. I wish he would start a basic class. His room is the coolest setup I've ever seen. m00n you should also be very proud of all the work you have done on you HT room. Next spring I am going to get started. Sorry for butting in. Danny Quote Link to comment Share on other sites More sharing options...
m00n Posted September 30, 2003 Author Share Posted September 30, 2003 I don't mind. I only nope that if people come in and make posts that this stays focused on acoustics and applies to what we are doing . If it does, this could end up being a very helpful thread for many people. dbflash, I just edited my first post in this thread. Oh and thank you very much for your kind words! It's been a ton of fun building this theater. Quote Link to comment Share on other sites More sharing options...
Bill H. Posted September 30, 2003 Share Posted September 30, 2003 m00n, I don't know about the numbers........but I was able to look up and listen to David Arkenstone , whom I have never heard....beautiful music, almost like water flowing over rocks, smooth. Thanks. Opps! didn't mean to get off track!......... Quote Link to comment Share on other sites More sharing options...
m00n Posted September 30, 2003 Author Share Posted September 30, 2003 Ok, I did the exact same test as last night, 5 channel pink noise. I did not do individual speakers though, just all 5 at once. Objective results of the WB Asynchronous Pink Noise tests. =============================================== Volume: -35 Channels: 5 Center seat middle row: 72db Left Corner: 78db Right Corner: 77db Subjective results =============================================== Same as last night. Cleaner up front, sounded a bit more refined, back corners more bass, especially in the back left corner. Kinda muddy but very full sounding bass. Almost overwhelming. Intersting to really sit and listen in different locations just how much the sound varies. I know this was not part of what you were looking for, butI am beginning to have a new favorite spot. Center seat back row for 2 channel. For movies with 5.1, it's yet to be determined if my favorite spot will change which his second row center seat. Quote Link to comment Share on other sites More sharing options...
dbflash Posted October 1, 2003 Share Posted October 1, 2003 m00n, thanks for the edit. i am just going to sit back and watch. i am very interested in this. i had moving pads (thick blanets) hanging on my walls hoping this would make a difference. i then read what Artto had to say about curtains and took them down. they made a slight difference, but not enough to keep all the sunlight from coming in. if you get a chance can you put the measurements from the distance between your front speakers and your new sweet spot in the center back row. thanks again, danny Quote Link to comment Share on other sites More sharing options...
artto Posted October 1, 2003 Share Posted October 1, 2003 Great Moon. Now we are getting somewhere! The room response measures 4-5dB higher in the rear corners of the room as compared to the center of the room. This is approximately a subjective 50% increase in sound level (10dB increase 'sounds' twice as loud). The subjective part of your listening experience confirms this. And that it is predominantly in the bass range. Now, my first question to you is, why and/or how did you determine that you needed bass trapping in the other locations? And remember, this is simply an exercise. It's not meant to insult or intimidate you. It's a discovery process. Quote Link to comment Share on other sites More sharing options...
artto Posted October 1, 2003 Share Posted October 1, 2003 ---------------- On 9/30/2003 7:04:25 PM dbflash wrote: m00n and Artto I hope you don't mind me listening in on your conversation. alot of what Artto mentions is over my head too. I wish he would start a basic class. Danny ---------------- Danny & Dr. thanks! I was kind of thinking the same thing. And I really don't mind. Maybe start a separate thread? I just didn't want to seem too arrogant on this subject as there are many ways to 'skin the cat'. But some ways are obviously much more effective than others. Not to mention the variations of interior or architectural design possiblities that might be applied. But there are definitely 'right ways' & 'wrong ways' of doing this. Do somethings wrong in the first place & there's basically no going back. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 1, 2003 Author Share Posted October 1, 2003 ---------------- On 10/1/2003 1:14:00 PM artto wrote: Now, my first question to you is, why and/or how did you determine that you needed bass trapping in the other locations? And remember, this is simply an exercise. It's not meant to insult or intimidate you. It's a discovery process. ---------------- Assumptions mostly as well as some degree of guestimation and common sence. I know that I have lots of sound in a small room, for the most part it's rectangular. What changes the rectanglur aspect is the riser floor and the back shelf I build and the vaulted ceiling. Those I suspect to some degree actually help. Also the walls are sheetrock and I have no wall hangings or anything to diffuse or absorb sound. And I have read and listened to people talk about frequencies canceling each other out. Also, i would like to mellow the room out. Try to warm it up just a bit. Also as mentioned, I have a lot of speakers in teh rear of the room. I feel confident that even though I may not be able to spot the problems right now, I have no doubt that treating my room will yield a smoother frequency response across the spectrum. Quote Link to comment Share on other sites More sharing options...
dbflash Posted October 1, 2003 Share Posted October 1, 2003 Artto, Sign me up for the class. When I redo my den I am going to talk to you. I have found that you can have a very expensive system and if your room is wrong you might as well buy a Boom box. What you are saying about understanding why I am doing something is so true. I was already to add the curve panels in my present room. I then started asking myself what exactly am I trying to accomplish? I really didn't have a good answer. I knew I wanted to make my room sound better, but I couldn't even answer what was wrong with it. Please keep this thread going. Danny Quote Link to comment Share on other sites More sharing options...
artto Posted October 1, 2003 Share Posted October 1, 2003 ---------------- On 10/1/2003 2:10:52 PM m00n wrote: I feel confident that even though I may not be able to spot the problems right now, I have no doubt that treating my room will yield a smoother frequency response across the spectrum. ---------------- This will be true ONLY if the treatment is done correctly. If done improperly, conditions can & will get worse. We are going through the process of spotting the problems. And the degree to which any problems exist. Yes, some of these things are assumptions. Never 'assume'. To borrow a line from the old 'The Odd Couple' show, "when you 'assume', you make an '***', out of 'u' and 'me'." OK. Next step. Now I want you to do the same thing, starting with the listening postion as you did above. Then do the same thing in the two seats immediately to the left & right of the center seat. Then also do the same thing right up against the side walls near the middle of the wall. Is this also where your side speakers are located, or close to it? Quote Link to comment Share on other sites More sharing options...
m00n Posted October 1, 2003 Author Share Posted October 1, 2003 artto, I have updated the image of my room layout. I added the surrounds and the rears. The position of them are within an inch of being accurate to real positioning in my room I did not put dimensions on them as you can tell, but if you need or want I can. As you can see, the surrounds sit a bit back from the center. I have not yet had the chance to do the audio listening tests yet this, I will later tonight, just wanted to update the pic real quick so you can get a better feel. Also I have some photos on my website if you want to go look at them. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 1, 2003 Author Share Posted October 1, 2003 Ok... Ok, I did the exact same test as last night, 5 channel pink noise. I did not do individual speakers though, just all 5 at once. Objective results of the WB Asynchronous Pink Noise tests. =============================================== Volume: -35 Channels: 5 Center seat middle row: 72db Left seat middel row Corner: 73db Right seat middel row Corner: 73db WB Asynchronous Pink Noise tests. =============================================== Volume: -35 Channels: 5 Left wall middle of room: 76db Right wall middle of room: 76db WB Asynchronous Pink Noise tests. =============================================== Volume: -35 Channels: 5 Left wall between the two surrounds: 75db Right wall between the two surrounds: 75db (I am not sure you wanted the readings along the walls between the surrounds. But, I wanted to make sure that you got them just in case.) Subjective results =============================================== I sat in all three seats in the middle row as you asked. the only difference I could hear was the soundstage shifted to the left and right as I switched seats. Ok i would expect that. The only thing I could really tell a difference in was the left seat again had a tad more bass response. Other than that, the overall tones clairity all seemed the same to me. I listened from the center left wall... Again I could not really hear much difference between anything other than low frequencies tended to be a bit more elevated. This would also go for center of the right wall. Obviously, everything was louder because I was closer to the speakers. There are some patterns I am seeing for sure. The left wall which is adjacnet to the subs, definitly seems have higher bass volumes. now this is going to sound strange but here it goes. As I move closer into the front of the room, the overall sound seems crisper, cleaner. However, the further back I go, the sound/music seems to sound fuller, more spacious. Not as constricted sounding. Now that's not to say that as I move forward in the theater it sounds like someone is putting something in front of the speaker, it's just not as.... Oh shall we say, flowing in the front as the back.... Something else I want to point out here is that when i am doing my decible tests, I am using a wideband pink noise 5.1 signal. However, for the subjective music listening, I am only stereo with help from the subs. Yes, i want my subs when listening to 2 channel stereo Quote Link to comment Share on other sites More sharing options...
artto Posted October 2, 2003 Share Posted October 2, 2003 That's Ok. We're just trying to get a general idea of what's going on & how that translates subjectively to what you're hearing. You've probably already noticed that the sound, particularly the bass, is louder in the rear of the room, especially in the rear vertical corners. Now, I need you to measure the response in the front left & right corners, & the middle of the front wall about mid level. No subjective listening required. Just measure. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 2, 2003 Author Share Posted October 2, 2003 WB Asynchronous Pink Noise tests. =============================================== Volume: -35 Channels: 5 Center of front wall: 74db Left corner front wall: 80~81db Right corner front wall: 80~81db Quote Link to comment Share on other sites More sharing options...
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