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Post by antonmcmillan on Apr 8, 2018 11:13:55 GMT
Hello, Hexspa, Thanks for you answer once again! I had thoughts about the speaker box, but at this point im not sweating about the measurements that much. I am waiting for some materials to arrive that will eventually go into covering the speaker enclosure with a massive sandwich type plate (MDFxMLVxMDF). Once I add that i will obviously do measurements and see how the response changes. I am assuming some of the stuff will immediately diminish or even disappear from the graphs. Yes, like you mentioned - I did look into waterfalls. I also like spectrogram to see the more precise picture. There are things in the waterfalls and spectrogram that show longer ringing at certain frequencies. Some of them I can explain very well (I added the 19" rack metal cover plates and when testing I can clearly hear them resonate very long after the test, so I guess ill get rid of those, even though the desk looks nicer with them at the moment). There are some ringing, that changes frequency( ). I dont know how to explain that, but its pretty much like this: After about 180 ms the decay at 40 Hz drops down from around 80 dB to 45 and after it get there it rings for more than a second and switches from 40 Hz to around 42 Hz. Maybe you have an idea of why this might happen? I have also attached the waterfall if anyone is interested: I have also smoother out the SPL graph: I actually did all measurements at 89 dB level.. I dont know if that is good or not, but for some reason my soundcard really had some issues putting out the volume and REW always asks to increase the level as the signal is supposedly too low to measure (I think its the reason for using a USB microphone of my RME).
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Post by antonmcmillan on Apr 8, 2018 11:38:46 GMT
Oh, ANd I also sat down to do a small sketch of the cloud im thinking of building. The basic idea is that it will be a 18mm (3/4 inch) MDF plate with the same with pine frame of 100mm (4") around it. Inside that framework I will either add insulation of maybe build one of Ethans panels for certain frequency range. It is so far a rought sketch - the end product will definitely include lighting mounted in it. I have also decided to put a LED strip on the back side of the MDF plate all around the perimeter, so it will have a nice effect when turned on. Im planning on digitally controlled RGB LED strips for some programming maybe to maybe swith around the mood around if wanted. The Cloud would cover almost all the area from the front of the room to behind the listener position and a 10-11 degree angle. I will alternate the angle with measurements and see what works best. The cloud will be fixed to the ceiling with a metal chain and anchored to the ceiling. You can see the basic drawing: And the placement in the design: Thanks for you input!
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Post by Hexspa on Apr 9, 2018 0:41:03 GMT
Ya, I don't know why ringing moves like that over time. It could be that both modes are actually ringing but the one is stronger so it takes precedence until it doesn't at which point the weaker one continues. I couldn't access your REW file. If you want, I'll download it and make a better waterfall for you. All you really care about is what's happening within 300ms or so and even then only below around 300Hz. The reason for this is that you want your bass to decay at least 20dB within 150ms so any more data is useless since decay tends to be linear. The exception, of course, being modal ringing which the room's treatment doesn't adequately deaden or if you decide to use a different metric as your standard. Related to linearity is your SPL level when measuring. Technically, your room will give an identical SPL whether you measure it at 60dBA or 90dBA. The only thing that may happen at higher levels is rattling and too low of levels may be subject to noise. The cloud idea looks good. I advise for broadband as opposed to frequency-targeted absorption but its your room after all. The other thing I'll advise for is use of at least an 8" cloud if you're going to use fluffy. One of the guys on here, Pasim, has something like a 14" cloud and his room's response is very crisp. I'm not sure whether LED lights affect the acoustics but I doubt it
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Post by rock on Apr 9, 2018 3:25:48 GMT
Regarding your cloud design which you have with an MDF backing: Designing without the MDF backing will double the surface area of your cloud and extend the LF performance; two big functional improvements. Support for the fiberglass can be taught wires or "hardware cloth" (rigid screening) attached to the bottom of the frame.
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Post by antonmcmillan on Apr 22, 2018 14:48:17 GMT
I couldn't access your REW file. If you want, I'll download it and make a better waterfall for you. All you really care about is what's happening within 300ms or so and even then only below around 300Hz. The reason for this is that you want your bass to decay at least 20dB within 150ms so any more data is useless since decay tends to be linear. The exception, of course, being modal ringing which the room's treatment doesn't adequately deaden or if you decide to use a different metric as your standard. Hey Hexspa, Thanks for your reply. I have updated the file in the download link and forgot to update the link. It is now fixed, but I added a shortcut in this post: HEREAs to regarding the waterfall - I would be glad if you checked out and came back to me with your thoughts. Thanks!
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Post by antonmcmillan on Apr 22, 2018 14:58:23 GMT
Regarding your cloud design which you have with an MDF backing: Designing without the MDF backing will double the surface area of your cloud and extend the LF performance; two big functional improvements. Support for the fiberglass can be taught wires or "hardware cloth" (rigid screening) attached to the bottom of the frame. Hello, Rock, Thanks for your reply! I somehow had the idea I needed to have the backing for the cloud to be a sort of an imitation of a ceiling that is angled.. But now thinking about your comment it makes sense. With the rigid backing I would create some sort of resonance and prevent some frequencies from going through the insulation. Without the backing the cloud can act on sound waves that go through it and come back from the surfaces behind the cloud for added absorption. I also decided to do as Hexspa said and increase the depth of the cloud to 200 mm (8"). More that that would really take up a lot of space in the room.. I am also thinkiong about adding some acoustic hangers above the cloud to use that empty space for additional absorption. What do you guys think? Maybe you would reccoment something different?
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Post by antonmcmillan on Apr 22, 2018 15:01:11 GMT
Oh, And I have received my speaked boxes recently as well as some SORBOTHANE DURO 70 pads to put underneath. You can see the picture HERE. As you can see - the speaker cabinet is very tightly anchored to the soffit frame and the compressed sorbothane pad is acting as a spring to help absorb some of the low frequency vibrations that the speaker is transmitting to the soffit framework.
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Post by Hexspa on Apr 23, 2018 12:58:29 GMT
Good to see you're making progress. I think you'll be happier with 8" of insulation. Remember to FRK non-RFZ points before you seal it. I reviewed and edited your graphs. You're doing well considering the room isn't finished. Check it out: What I go for is 20dB decay within 150ms. Most your ranges are doing pretty good. A few need work - particularly around 53Hz and 117Hz. There's also a narrow SPL notch at 150Hz. This is something I've repeatedly observed. It's that many rooms seem to get a null around their Schroeder frequency. Maybe the answer is always more absorption. I think the increased panel thickness should help. Don't forget the FRK! It looks like you want to add more absorption behind your cloud and that's perfect. Thanks.
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Post by Hexspa on Apr 23, 2018 15:03:12 GMT
Here are a few more for reference. I like to see a full smoothed SPL for bearing. Of course the gonzo bass graph is good for problem solving.
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Post by antonmcmillan on Apr 27, 2018 6:01:05 GMT
Thanks Hex!
What would you say would be best to tackle the flatter frequency response? The decays are more or less clear to me, but the response.. Im a bit puzzled on how to target that one..
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Post by Hexspa on Apr 27, 2018 20:14:19 GMT
Thanks Hex! What would you say would be best to tackle the flatter frequency response? The decays are more or less clear to me, but the response.. Im a bit puzzled on how to target that one.. Hey, I think it's all related. Sometimes it seems hard to predict. A small throw rug behind my speakers gave me a null once. You've got a few variables to work with: speaker position, listening position, absorption placement, and movable boundaries. Given those options you can listen closer, further, higher or lower. Your speakers seem locked in but maybe some wiggle room is possible. The null is probably from the desk but you need to calculate it. If you don't know how to predict modal response then take the time to check that out. You can use that to tailor your options - particularly treatment. For instance, I'd originally placed panels on my rear wall. Turns out they were better on my side walls and angled. Basically once you've gotten your basic setup it's on to the tweaking phase. Experiment, measure, analyze, post, improve. Cheers.
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Post by antonmcmillan on May 1, 2018 8:31:03 GMT
Yeah, I guess youre right. I have a thought that the null is because of the speaker enclosure not being closed up and the reflections from the inner walls interfere with the original signal. Seems like through this month I will be able to close down the enclosure, add the stands, completely close the walls with fabric and install the cloud hopefully. I hope these will help with the FR of the room Ill post whats going on when I have more info Thanks for your input. M
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