m00n Posted September 26, 2003 Share Posted September 26, 2003 So, if you have ever taken the grill off your RS7s and I suspect your RS3 you will see that on the sides there are ports. What are these really doing? If you have seen my website you have seen this pic . I am going to be building a low/medium range frequency trap right in between them and the sides of the trap will be wide within 1/4 of the ports on the surrounds. So basically I want to know if covering up these ports is going to have a huge impact on the sound of the RS7s.... Quote Link to comment Share on other sites More sharing options...
ygmn Posted September 26, 2003 Share Posted September 26, 2003 Are they not the ports for the center woofer.....that way they vent sound to the sides in the dipole fashion? Quote Link to comment Share on other sites More sharing options...
artto Posted September 26, 2003 Share Posted September 26, 2003 MOOOON!!!!!!!! after all that has been said & done......this is what you want to do? shame on you you have learned ABSOLUTELY nothing. I'm so ashamed. what in the hell is the matter with you man? Quote Link to comment Share on other sites More sharing options...
m00n Posted September 26, 2003 Author Share Posted September 26, 2003 Eh? What are you talking about? What's wrong with absorbtion? artto, this is going to sound good. I don't get it the *** gnawing. What's wrong with my idea? Good thing I've not done much yet but I have started my columns for my surrounds to sit on. I will post some pics in a sec... BRB with those. Quote Link to comment Share on other sites More sharing options...
m00n Posted September 26, 2003 Author Share Posted September 26, 2003 The support Quote Link to comment Share on other sites More sharing options...
m00n Posted September 26, 2003 Author Share Posted September 26, 2003 The frame. Quote Link to comment Share on other sites More sharing options...
m00n Posted September 26, 2003 Author Share Posted September 26, 2003 Close up look at the framing. Quote Link to comment Share on other sites More sharing options...
m00n Posted September 26, 2003 Author Share Posted September 26, 2003 Bottom plate framing. Quote Link to comment Share on other sites More sharing options...
m00n Posted September 26, 2003 Author Share Posted September 26, 2003 Soundboard added to help with catching low frequencies... This is where it will sit until I can get some ridged fiberglass to put in around the frame.. The ridgid fiberglass will catch high frequencies and some mids. Quote Link to comment Share on other sites More sharing options...
Fish Posted September 26, 2003 Share Posted September 26, 2003 m00n,you are one industrious dude,looks good.The ports do play a very important role in the overall sound.Covering them completely up would not be good. Quote Link to comment Share on other sites More sharing options...
m00n Posted September 26, 2003 Author Share Posted September 26, 2003 ---------------- On 9/26/2003 8:39:17 PM Fish wrote: m00n,you are one industrious dude,looks good.The ports do play a very important role in the overall sound.Covering them completely up would not be good. ---------------- LOL... Inustrious dude. Hey I like to build stuff. I used to frame houses, now I sit behind a desk all day long. Not to mention, I simply have a calling hobby right now and thats building this theater. Quote Link to comment Share on other sites More sharing options...
formica Posted September 27, 2003 Share Posted September 27, 2003 MooN... Your surrounds are of the "ported" variety. If you've ever wondered what the ports do on a speaker... well it acts exactly like the passive radiator on you RSW15. It is not a vent The port's length is calculated to hold a "mass" of air in it... and that air will resonate at it's natural frequency (varies with it's mass). The port is calculate to resonate at the frequency the woofer begins to roll off... so as the woofers volume begins to drop, the port's begins rise. It basically extends to frequency response. Note that air will only resonate for a narrow frequency band, so the speakers response will drop quickly below the ports tuning. Ported definition at www.diysubwoofers.org hope it gives a better feeling of what they do... Rob Quote Link to comment Share on other sites More sharing options...
m00n Posted September 27, 2003 Author Share Posted September 27, 2003 So then if I have a board that is only about 1/2" away will it or will it not affect the sound? From what you are saying it makes me belive it won't... BTW, what does resonate mean? I have been hearing that a lot lately. Quote Link to comment Share on other sites More sharing options...
m00n Posted September 27, 2003 Author Share Posted September 27, 2003 ---------------- On 9/26/2003 8:39:17 PM Fish wrote: m00n,you are one industrious dude,looks good.The ports do play a very important role in the overall sound.Covering them completely up would not be good. ---------------- You know I just read your post closer... I don't intend to cover it completly... I may have a 1"x4" sitting about 1/2 away from the port. So, air will be ablel to get in and out, just I don't know how much space they need to work right. Quote Link to comment Share on other sites More sharing options...
formica Posted September 27, 2003 Share Posted September 27, 2003 Think of the port as a small speaker... obstructing it would be like placing something in front of a driver... sound will travel around the object (low frequencies)... but less of it. To close and it may act like extending the port length... and the mass of air in the gap will be added to the one in the port. Big difference? Probably not, but I would avoid it if it were me. Can you slide the speaker forward a little? For resonance, the WordNet Dictionary definition: RESONANCE, Pronunciation:'rezununs, , 3. a vibration of large amplitude produced by a relatively small vibration near the same frequency of vibration as the natural frequency of the resonating system An example of a resonant system would be a waterbed... (esp the ones with large chambers) which will have very large "waves" when you push it just at the right rhythm... the "right rhythm" would be it's resonant frequency. Later... Rob PS: I'm sounding more and more like a geek... got to get to bed. Quote Link to comment Share on other sites More sharing options...
artto Posted September 27, 2003 Share Posted September 27, 2003 Moon, Honestly, the best advice I can give you right now is just leave well-enough alone. You're in way over your head trying to alter a lot a things which you do not understand yet. It's great that you're so industrious & motivated. But how about slowing down a bit and learning a lot more about the things you need to understand before tackling construction projects that are, for the most part, somewhat permanent in nature. I don't mean sound like a 'know-it-all', but the fact is I didn't learn what I know overnight. I've had things like the Klipsch Audio Papers & Dope From Hope publications at my access for 30 years to study & refer to. I've played music professionally (on & off) for over 30 years. As an architect I've studied auditorium and theater design, indoor & outdoor acoustics, and sound transmission in building structures. Not mention the 20+ years of building, experimenting & modifying my own dedicated listening/music room which has been published in several major audio magazines over the years. And I'm still learning. You have to learn to crawl before you can run. Peace Quote Link to comment Share on other sites More sharing options...
m00n Posted September 27, 2003 Author Share Posted September 27, 2003 artto, based on the private message I just sent back to you, would you agree on at least these two ideas for now. First reflection traps (mirror trick) Corner bass absorbers along my ceiling and walls. And what about my RS7 column mid/high absorbers? As you can see I am smack dab in the middle of that. However, only one of them has any soundboard in it. I can always take it out. My goal was to have the soundboard behind some rigid fiberglass. I don't have the fiberglass yet though. If you feel like it, your comments would be very welcome in my posts over in the www.recording.org forums. Their site is all about recording studios and what not but they do have a small section on acoustics. Perhaps your extensive background and home theater knowledge will put a new twist on things over there. It could be quit possible that all their acoustic ideas are very recording studio biased. I know it seems like I am in a hurry and you are right, but I simply want to start decorating the place but I can't do that until I get my acoustics in place. And also.... I am sure my bass response has got too be as jagged as the Rocky Mountians You suggest I hold off... Ok, but then what? After that, do you have any suggestions? A plan of attack from there? I don't have years and years to develop this theater. Hell, we are going to be in this house a MAX of five more years so I am kinda in the mind set that if it's not 100% perfect, that's ok because I can make it perfect in my next house. I suppose you could almost consider this my training ground . Quote Link to comment Share on other sites More sharing options...
artto Posted September 28, 2003 Share Posted September 28, 2003 Moon, your first really big mistake is, wheres the diffusion? All I see mentioned is absorption & trapping (essentially more absorption). Second, how did you determine that any one of these individual traps are going to absorb the frequency range that you want, under these specific circumstances? Third, how did you determine the amount of absorption required? Fourth, how did you determine the frequency range that needed the absorption? And fifth, how did you determine where this absorption was required? Last but not least, I cannot stress enough about how important BROADBAND treatment of the entire frequency range is. AND, that this applies to BOTH absorption, and DIFFUSION. Now, Im not saying that the way I built my room is the one & only way. But it does take advantage of some basic principals which can be applied in different ways. For example, the large curved Masonite panels. These panels absorb more bass than treble. This is desirable. In smaller spaces bass is usually the biggest problem in regards to bumpy frequency response & reverberation time due to the build up of standing waves (reflected frequencies that get reinforced by the next wave of that frequency from the loudspeaker, and/or reflections). These same standing waves often also cause the opposite effect in other parts of the room, particularly at the location of the usual sweet spot, or favored listening position, where cancellation of those same tones can occur. Consider for a moment what those large curved Masonite panels are doing. The panels do not hang symmetrically. Gravity quickly makes the panels sag. This basically forms a polycylindrical surface. In other words, the radius or curvature is continuously variable across the entire surface. In this way, it effects a broad range of frequencies equally, while providing a continuously variable angle of diffusion as well. It is very efficient at diffusing a broad range of frequencies while at the same time absorbing more bass than treble. So the idea here is NOT to absorb everything, or even most of it. The goal is to absorb ALL FREQUENCIES EQUALLY (or at least in a desirable way), but not entirely, while at the same time DIFFUSING ALL FREQUENCIES EQUALLY (remember, these are 'goals', objectives), with the end result having uniform frequency response AND uniform reverberation time with regards to frequency, and ultimately, being able to do this over a wide range of volume levels, from very soft to very loud. And to achieve those results throughout as much of the room as possible. BROADBAND ABSORPTION and DIFFUSION = more uniform frequency response & reverberation time (with regards to frequency) over a wide dynamic range over a wide listening area Quote Link to comment Share on other sites More sharing options...
m00n Posted September 28, 2003 Author Share Posted September 28, 2003 artto as always, thank you very much for your input. But I would ask, how do I go about finding these issues? Should I get the special software and hardware and start taking measurements in my seats? I realize that every seat is going to have a bit of a difference in frequency response and that I will never get them indentical. So with that said... What do I do next? One other thing... With such a small room 10'x22'ish, doesn't it make since to have a fair amount of absorbtion? Seems like without it, I am getting a lot of extra reflections going on. Just a thought. Quote Link to comment Share on other sites More sharing options...
artto Posted September 28, 2003 Share Posted September 28, 2003 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. Quote Link to comment Share on other sites More sharing options...
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