m00n Posted October 13, 2003 Author Share Posted October 13, 2003 Ok... so I did a second sound test (I have only sat in the middle row of seats). This time I listened to Star Wars and Titan AE... Without the second set of surrounds what I am finding is that there is: A slight overall improvment in sound. More in Titan AE than Star Wars. The seating position does not seem to be.... For the lack of a better term, stuffed and it sounds a bit more refined. It seems to sound a bit more direct. All this leads me to two questions as to why 2 surrounds sound a bit better than 4 surrounds: How much of that is because of phaze cancelations and anomolies? How much of that is because of so much sound in a small area and all the reflections? Which again leads me to wonder... If I had all 4 surrounds running, some absorbtion in the right places would the room sound better and could I bring it to a level where it would sound as good as running with only 2 side surrounds. Because running with only 2 side surrounds only sounds marginaly better. I think before I can make a definitive decision, I need to listen more and I definitly want to experiment with some absorbtion and possibly some diffusion. I definitly don't want to rush into this decision. If it was a HUGE difference I would do it hands down, but because it's only marginaly better I think I want to see if I can do some experimenting first. I hope all that babble made since. Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 13, 2003 Share Posted October 13, 2003 sounds like you're describing the effects what it likes to get rid of comb-filtering different types of speakers wouldn't change the phenomenom. as far as your rear surrounds, they don't seem placed very effeciently for the back row of seats (which you don't seem to care about). nonetheless, their placement would be much better if it was somehow lower and further back (thus, why soffit mounting might be a good option). Quote Link to comment Share on other sites More sharing options...
m00n Posted October 13, 2003 Author Share Posted October 13, 2003 When you say sofit mount them, are you referring to going with an in-wall speaker or using the RS7s, but mounting them differently? You are right about the back seats. I am not too worried about them at all, they are mostly filler seats in the event I do have a large crowd. I am trying to talk myself into doing awawy with the extra RS7s... I really am. I have even thought about getting rid of ALL my RS7s, and getting two more RC7s. Ok I must ask, why is it ok to have sides as well as rears, but it's not ok to have 2 sets of side surrounds? Is it just because my surrounds are too close together? Or is it that the processors will do something to the rears so that combing is not an issue? Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 13, 2003 Share Posted October 13, 2003 i think soffit mounting is the correct term...it means cutting a hole in the drywall and sticking your RC7's in as far as they'll go (you'll prob need to build a little shelf sticking out or something)...dunno if you'll have to go vertical with this either (dunno how your joists and wall loading and all that crap works out). there's more to soffit mounting than just that, but it's the basic concept. the reason it's "OK" to have rears and surrounds is because they contain different signals (i think) AND are aimed at a different direction (a 90 degree angle gets rid of most all comb filtering if i remember right). However, if 7.1 doesn't have more material than 5.1, you better believe that two surround speakers would prob be better (or maybe a 6.1 setup)...while you're at it, why don't you just get rid of your mains too? you won't need them either arto is gonna hate me, but i think the "cool" factor of 2 side surrounds and 2 rear surrounds would have a larger effect than the increase of any amount of clarity you might obtain...it takes extended lengths of listening to begin noticing those kind of things and it's always more fun to impress the guests however, if you really want the best quality, get rid of as much as possible...or if you want both, only connect what you need and leave the rest for looks... Quote Link to comment Share on other sites More sharing options...
m00n Posted October 14, 2003 Author Share Posted October 14, 2003 So you think my rears would be better placed if they were lower eh... And what did artto mean by placing them so they would have better coverage? Well, there is not much I can do about lowering them due to the shelf I built into my wall which I am not sure helps or hinders the overall sound quality of the room. Maybe I should think about getting rid of the back row of seats all togeher, as well as get rid of that shelf and build columns for the rears to sit on. Not sure if I want to sofit mount them. Wouldn't that have a bad affect on them since they too are rear ported? Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 14, 2003 Share Posted October 14, 2003 yikes, didn't know they were rear ported! forget that idea then The reason for moving the rear speakers around was largely to make their coverage better for the rear row. As far as the shelf, that's artto's world Quote Link to comment Share on other sites More sharing options...
artto Posted October 14, 2003 Share Posted October 14, 2003 10/11/2003 8:51:14 PM Moon said So if I understand it correcty, comb filtering is a result of two speakers sound waves canceling out and the response pattern that it makes... Yes? They did help me out. But what they didn't tell me is how to create magic solution to my surrounds. Answer: No magic. This is a phenomena which is the result of our real three dimensional world. The only way to eliminate this is to have both speakers occupy the same space & time, which is obviously not possible (yet). 10/11/2003 8:51:14 PM Moon said Will diffusion help out with comb filtering? Answer: No. This is primarily the result of the amount of direct sound reaching your ears (or test instrument/pickup) relative to the distance/time difference of any reflections (or in this case, your second speaker. You might want to think of that second speaker being a reflection)). Remember, we want a longer time delay between the initial direct sound & any reflected sound so they dont smear together diluting imaging & detail. 10/11/2003 8:51:14 PM Moon said Now given my room where I have 2 surrounds on teh same wall about 2 feet appart, could I put diffusers between them and if so, would it help? Answer: No. Diffusion is not a piecemeal patch. Remember, we are treating THE ROOM! Not the speakers! 10/12/2003 1:03:34 AM DrWho said for your rear surrounds...have you ever considered using in-wall speakers or even soffit mounting your current speakers in the wall? from all the pics, it seems like that would do wonders for providing more present rear effects (especially in the last row). Answer: This is a good suggestion. Get those rear speakers up high & point them downward into the listening area. Also, Use only one speaker system (as you should on the sides). The same comb filter effect is occurring here by feeding the same signal to two speakers in close proximity to each other. 10/12/2003 6:22:24 PM Moon said When you refer to columns, do my RS7 colums count? Answer: Not really. When I said freestanding, I meant away from the wall surface. It would be exposed on all sides to obtain maximum reflection/diffusion in all directions. 10/12/2003 6:22:24 PM Moon said I am not too worried about going below 75hz anyway. I can't remember exactly what frequency it was, but I read somewhere that at a certian frequency, sound waves will penetrate the sheet rock anway. Is that true? Answer: Sort of/Not really. As the frequency gets lower, the wavelength gets longer. As the wavelength gets longer, it takes larger & thicker & more massive materials to absorb the sound and block transmission. And while SOME of the low frequency sound will penetrate the sheetrock, SOME is also reflected back into the room. The more substantial the room surfaces (ie: sheetrock on concrete walls below grade) the more energy gets reflected back into the space. 10/12/2003 6:22:24 PM Moon said There are two things you never mentioned... 1. You never mentioned the corners where my ceiling and side walls connect. Should I not worry about these for now? 2. Doing something to that first reflection point. Answer: 1. If you want to treat the horizontal (wall/ceiling) corners with absorption, thats fine. I suggest taking things step by step that so you can evaluate the benefits or detriments of each application. Otherwise, how will you know the results of what does what and to what degree? 2. Quit worrying about the first reflection point. In practice, this point is not a simple single point, but rather an area. We are dealing waves here, not a bullet or a baseball. And, this is not as important as the time difference between the initial direct sound from the speaker, and that of the first reflections. Keyword=time difference. 10/13/2003 12:07:23 AM Moon said All this leads me to two questions as to why 2 surrounds sound a bit better than 4 surrounds: How much of that is because of phaze cancelations and anomolies? How much of that is because of so much sound in a small area and all the reflections? Answer: As myself, and others have previously stated, this is the result of the comb filter effect which is primarily the result of the time difference between direct & delayed (reflected) sound. When you have 2 speakers reproducing the same signal in close proximity to each other, especially in a small enclosed space, you are compounding this effect. Its the result of phase cancellations, whether it be from the two speakers reproducing the same signal in close proximity to each other, or reflections interacting with the direct sound from the speaker(s). 10/13/2003 12:07:23 AM Moon said Which again leads me to wonder... If I had all 4 surrounds running, some absorbtion in the right places would the room sound better and could I bring it to a level where it would sound as good as running with only 2 side surrounds. Answer: NO. As you begin to get the rooms acoustics right, the anomalies caused by the two speakers will become even more apparent. You dont need the coverage. You dont need the acoustic power output. Even at this stage, you admit experiencing a marginal improvement by eliminating one of the two speakers. Why do you still want to keep going in this direction? To look impressive? Put a bunch of fake ones in if thats your objective. Thats what the rock bands do. You really think all those Marshall heads & cabinets have power & speakers? LOL. Ive been there. I know. They dont. Just props my friend! Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 14, 2003 Share Posted October 14, 2003 "You really think all those Marshall heads & cabinets have power & speakers? LOL. Ive been there. I know. They dont. Just props my friend!" woah there! i thought we were supposed to keep that a secret!!! Quote Link to comment Share on other sites More sharing options...
m00n Posted October 15, 2003 Author Share Posted October 15, 2003 ---------------- On 10/14/2003 6:23:00 PM artto wrote: 10/12/2003 1:03:34 AM DrWho said “for your rear surrounds...have you ever considered using in-wall speakers or even soffit mounting your current speakers in the wall? from all the pics, it seems like that would do wonders for providing more present rear effects (especially in the last row). Answer: This is a good suggestion. Get those rear speakers up high & point them downward into the listening area. Also, Use only one speaker system (as you should on the sides). The same comb filter effect is occurring here by feeding the same signal to two speakers in close proximity to each other. ---------------- Then why do they have 7.1? I am not splitting that rear channel, I have two sepparate rear outs. ---------------- On 10/14/2003 6:23:00 PM artto wrote: 10/12/2003 6:22:24 PM Moon said “There are two things you never mentioned... 1. You never mentioned the corners where my ceiling and side walls connect. Should I not worry about these for now? 2. Doing something to that first reflection point. Answer: 1. If you want to treat the ‘horizontal’ (wall/ceiling) corners with absorption, that’s fine. I suggest taking things step by step that so you can evaluate the benefits or detriments of each application. Otherwise, how will you know the results of “what does what” and to what degree? ---------------- Good point. Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 18, 2003 Share Posted October 18, 2003 well how's things coming along? or has the decorator person lady taken over already? Quote Link to comment Share on other sites More sharing options...
m00n Posted October 18, 2003 Author Share Posted October 18, 2003 ---------------- On 10/18/2003 12:21:34 AM DrWho wrote: well how's things coming along? or has the decorator person lady taken over already? ---------------- No man no... No decorator lady has taken over. As a matter of fact, I had to cancel that idea. Something inside me told me that it was not a good idea, good thing I listened to that something because my wife was not pleased with the idea. As far as my room goes. Not much has happened this week due to not being able to find time to get to home depot to get stuff. I am hoping to get to home depot today though so I can build at least 2 bass traps. Gonna be hard though considering todays is the wifes birthday. That leaves tomorrow only really... Furthermore, I am torn between two different bass trap designs. I was reading in my Master Handbook of Acoustics, Chaper 9 Page 215~231. There are pics on page 231 He has a design that is based on the Helmholtz principal by using pegboard. I am also really interested in the Ethan design where his solution is air tight. and I am not sure which is better. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 20, 2003 Author Share Posted October 20, 2003 Artto... Ok man. Here is an update. I have started working on my bass trap. I have modified the Ethans design. not only do I want this to be a bass trap but I also want them to be absorbing mids and highs too... You said the back wall should be absorbing. Here is what I did, I put the frame up. You may not be able to tell from this first image, but I put a 1x1 all the way around the frame of the box. It's up agaist the wall. This allows me to put a layer of soundboard in and create a 1" air gap behind the soundboard. Next you can see that I have actually applied the soundboard and some of my DIY rigid fiberglass. If you want to see how I made my DIY rigid fiberglass you can see it down in odds and mods. And lastly you can see a zoomed out shot of the entire multi frequency absorber. Yes, it may look like a basturdized hack, but it works. It's very dead in front of it as well as it does not have all the bass build up in that corner like it used to. Now, I have to do my other coner now. One thing I want to ask you though before I go much further... Do you suggest that I remove the insulation and cover it up with the 1/8" plywood to make just a low frequency trap or can I leave it as a multi trap like it is? It's no big deal at all to pull that insulation out. However, it was a REAL PAIN IN THE ARSE making that DIY rigid fiberglass. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 24, 2003 Author Share Posted October 24, 2003 artto, Just an update. I have both traps done now. however that does not include the little areas between the shelf and the walls. I will be working on those this weekend. I must say that while they may look big and ugly (will dress them up) they do seem to be working. I noticed when watching the pod race that some of the LFE was a bit more distinguished and was hearing affects that I had not noticed before. Maybe it's wishfull thinking, but I don't think so. The room feels just a bit less conjested with those traps in place. I have not covered them with plywood or anything, they are still bare. I really makes me whish I had not build that damn shelf into my wall now. It's really kind of drag that it's there. But on the other hand, in some way, it's working as a diffuser so to speak. Quote Link to comment Share on other sites More sharing options...
danechristian Posted October 24, 2003 Share Posted October 24, 2003 glad to hear about your project m00n. about your bass traps. why not cover them with a very thin fabric. in a way, still the bass trap will be the same as without fabric. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 24, 2003 Author Share Posted October 24, 2003 I will be covering them, I just have not gotten to it is all. Quote Link to comment Share on other sites More sharing options...
m00n Posted November 2, 2003 Author Share Posted November 2, 2003 Ok artto... I have completed building my rear traps. I can definitly notice the difference. The low frequencies definitly sound cleaner not as muddy. This was definitly worth doing. I know it may not have been as ideal as your idea, but I just need to be money thrifty right now. I went and listened from top to bottom, all that bass build up is gone. These are definitly working very well. The top traps sit on top of the bottom traps, they were constructed the same way. I have an air gap created by useing a 1/2 rip of soundboard, in front of the soundboard I have a small air gap and then my DIY Rigid fiberglass. Image of top trap innerds Image of top trap with fabric stretched over it. The traps are the same on both sides. Oh and before anyone things eeewwww look at all the staples... I will someday be putting molding in place to hid the stapels. That will happen when I start working on the decore. So at any rate artto, I'm ready to move onto the next step which is step 2 and you said this =================================================== 2. Get rid of the extra speakers. They are diluting, not enhancing, the effect that multi-channel sound produces. =================================================== For now, can I just leave the there? Or do I really need to remove the one set and then reposition the other before we move forward? Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 3, 2003 Share Posted November 3, 2003 m00n: I gotta hand it to you! You definately have lots of energy to improve the looks and performance of your system. You can tell that you take pride in what you do. Quote Link to comment Share on other sites More sharing options...
artto Posted November 3, 2003 Share Posted November 3, 2003 OK Rick. Great! Yes, I still think you should get rid of the two extra speakers. But before you do that, I would like you to go through the room SPL measurement exercises you did at the beginning. I hope you noted some sort of reference level from the main speakers so the results wont be unknowingly biased. If not, I guess its my fault for not mentioning it. What we want to see is how much change has occurred to see how effective the new sound absorption is. Quote Link to comment Share on other sites More sharing options...
m00n Posted November 8, 2003 Author Share Posted November 8, 2003 artto, I only took these measurements because I figured those would be the ones you were really interested in. If you want others let me know. ======================================================= WB Asynchronous Pink Noise tests. Volume: -35 Channels: 9 (includes both surrounds and rears) ======================================================= OLD MEASUREMENTS PRE-BROADBAND TRAPS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Top left corner of back wall: 83db Bottom left corner back wall: 81db Top right corner of back wall: 83db Bottom right corner back wall: 81db Center seat center row: 73db NEW MEASUREMENTS POST-BROADBAND TRAPS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Top left corner of back wall: 79db Middle left corner of back wall: 78db Bottom left corner back wall: 78db Top right corner of back wall: 79db Middle right corner of back wall: 77db Bottom right corner back wall: 77db Center seat center row: 73db CONCLUSION ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Left side dropped 4db Right side dropped 5db Sweet spot stayed the same I guess that's not too bad is it? Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 11, 2003 Share Posted November 11, 2003 yay, thx for the numbers i was trying to find this out for myself, but is it safe to assume that doubling the thickness would also double the results? (how bout tripling the thickness to double the results?) i ask because im interested in using this design, but need it to do a lot more (like on the magnitude of 12db?...i will be doing other room treatments too). Quote Link to comment Share on other sites More sharing options...
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