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Post by dok on Jan 23, 2022 12:06:00 GMT -6
Or is the idea to just use the sub to compensate and simply overpower the null ? Interesting articles:thx, the monitor height relative to room dimension argument is compelling as is the do whatever it takes to fix the sonic canyon at your listening position : he is just being sensible. That's the idea with getting it right at the listening position - your nulls and peaks are occurring in different positions of the room due to the relationship between wavelengths and your room dimensions. The trick is to get your speakers and ears into positions that are in a good relationship to each other as well as not sitting in the biggest nulls in your room. This is going to be different in every room. Carl Tatz (author of the first article I posted) offers an axial mode calculator on his site along with some other tools for determining this: carltatzdesign.com/acoustic-tools/axial-mode-calc-example.pdfAs far as subwoofers go, yes it's absolutely counterintuitive and I'd encourage everyone who's curious to try it out for themselves. You may have learned your room without one and it might sound great and your mixes may even translate, but there's every chance you're dealing with that "Grand Canyon of low frequency information" if your monitors are not soffit-mounted (on stands or your desk or console). So yes, you are absolutely wanting to excite the room modes in order to fill in that gap at your listening position. And none of this is to say that you shouldn't still use bass traps and acoustic treatment. From that first article: Yes, subwoofers. Properly positioned — and two are always better than one for phase-correcting axial modes — they will begin to fill in your Grand Canyon of missing bass information. This is the only way the canyon can be filled, and no room is too small for this to work. Positioning is key to attain the best results, but it is a subject too expansive to thoroughly cover here. Without powerful analysis software and digital processing, perfection will be elusive. However, great improvement can be yours if you are diligent in your approach. Front-corner subwoofer positioning will offer the largest piece of clay to work with as you experiment with the high- and low-pass crossovers, frequency settings and subwoofer volume. A subwoofer placed in each front corner will also attenuate the first and third axial-width mode null at the listening position. By the way, you can ignore those who profess not to corner-load the subs because it excites all the room modes. It does. And who cares? All you should be concerned about is the listening position; to hell with the rest of the room. This is as true in a bedroom as it is in a well-designed commercial studio control room. You don’t tune a room: you tune the monitors. There is only one position that can be accurate and that’s your position in front of the monitors. The laws of physics dictate this, not me. A next step would be to take advantage of DSP room correction systems such as those supplied with some Genelec and Dynaudio monitors, or third-party units, that could greatly help fill in the canyon and smooth your monitor’s frequency response in the room.
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Post by kcatthedog on Jan 23, 2022 14:54:36 GMT -6
interesting set up my not great sub on the centre axis, played with it at front wall and coming forward in 1 foot increment, flipping phase but kept cross over at 100. the all sweeps plot is a mess but the brown sweep, 0 feet off wall and in phase, had no deep nulls, lowest more uniform bass response and varied by 10-15 db or so I think the best sweep so far and rt60 and clarity acceptable to keep consistent with other sweep, I did not high pass filter the focal so will redo with focal filter set at 90 and compare.
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Post by dok on Jan 23, 2022 15:10:54 GMT -6
Nice! Is your sub side or bottom-firing? If the latter it's worth trying firing toward the wall. I've found good results about 3-4 inches away from the wall (or the width of my fist). And don't be afraid to try the corners (measure facing in each direction and both polarity settings each time) while you're measuring and moving stuff around.
The nice part is that the sub doesn't have to be top of the line - as long as it's not introducing a ton of distortion or decay it's really just there to activate those modes. In my last space where I had a nice 18x21 room, I used the $80 Monoprice unit as a third sub and it was totally fine.
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Post by Tbone81 on Jan 23, 2022 15:54:14 GMT -6
To add to what Dok already said, try rotating the sub in 90 degree increments and see how it performs. I cleared up a huge null in my low end by turning my sub 90 degrees so that it was facing to the side. Also, play with the volume of the sub in relation to the mains. I noticed that my nulls and peaks were relative to the volume of my monitors (and sub), the louder everything was, the bigger the nulls/peaks. It was a hug "Duh" moment for me.
Its worth noting that after I went through the same process as you, I ended up picking the position that sounded best, not looked the best. And that's completely subjective. But after sorting out the major problems I believe you come to a point where you have to subjectively decide what you "like to hear" vs what "looks the flattest". I'm talking about that in the context of a well treated, but very imperfect room. Pick your poison so to speak.
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Post by kcatthedog on Jan 23, 2022 16:31:33 GMT -6
I think side firing. I’ll experiment with orientation, ah, the sub’s not mine, not that there is anything wrong with that? I tried the focal hpf at 90 and this reintroduced a low null. So, set focal back to no hpf, just proved that need to excite that freq with the combined volume. If any one orientation is better, then I’ll play with sub volume too. but having the high low within about 10 db and the ft60 1/3rds within a small range is consistent with the bbc standard. So, I’m pleased. Thx for all the great insights .
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Post by kcatthedog on Jan 23, 2022 18:27:38 GMT -6
So put sub back to the front wall, then oriented 90 degrees each time and switched phase so 8 plots discarded the worst, above 200 they were essentially the same but below 200 there are some differences I would think best to go with the line (brown) with the most consistent volume by freq but that one has a reduced null the other two, actually both have peaks and their volume range is greater so they are less consistent. thoughts ?
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Post by dok on Jan 23, 2022 19:40:29 GMT -6
I'd probably pick the brown one too, it's lower and there's less stuff usually happening in that range, plus you're not dealing with that huge peak between 40 and 50 - I'd say with this Geddes/Tatz theory of subwoofers the idea is that a second (and potentially third) sub will continue to fill in that null you're seeing in case you find that one sub isn't cutting it. You're really close to +-5dB which is really great for us DIYers. Can't do much better than that without going insane, but this is where you want to be if you decide to do something like Sonarworks later.
Something I meant to ask earlier - are you sweeping with one speaker at a time? I can't tell from your REQ Wizard captures. This way you can compare L to R and see if you have major issues on one side vs the other.
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Post by kcatthedog on Jan 23, 2022 20:27:36 GMT -6
Thx.
I had been doing stereo then L R separately, just didn’t over these last few as it was really the mono sub that was new ?
Tomorrow, I’ll do a l/r separated as I am curios too, also curious about varying crossover and volume ?
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ericn
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Post by ericn on Jan 23, 2022 21:08:27 GMT -6
I think side firing. I’ll experiment with orientation, ah, the sub’s not mine, not that there is anything wrong with that? I tried the focal hpf at 90 and this reintroduced a low null. So, set focal back to no hpf, just proved that need to excite that freq with the combined volume. If any one orientation is better, then I’ll play with sub volume too. but having the high low within about 10 db and the ft60 1/3rds within a small range is consistent with the bbc standard. So, I’m pleased. Thx for all the great insights . 2 things to try 1. Raise the x-over freq to 120. 2 try using asymmetrical crossover points, play around with slope and freq of sub and mains individually. Again though as you move the sub around listen and measure individual ch as well, you might find on the graph it looks good but LR balance is wrong. Also watch for suck out exactly 1 and 2 octaves above crossover points.
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Post by kcatthedog on Feb 1, 2022 9:02:23 GMT -6
I have been rebuilding my current absorbers, building out some to six inches deep 2x4 feet. Going to put these 2 on my front wall behind monitors and at my side first reflection points. I will be adding a rockwool rigid 2x4 1.5 inch comfort board to the front, retaining the fluffy rockwool behind. IF I can add an air gap, between these too I will. I have been reading about the benefits of adding a reflective front material (rpk) for mids and highs to ensure room does not get too dead. I have also read that people use thin plastic .7m or heavy paper for this as well. But at my local Home Depot they have two interesting products, that have a reflective material either in both sides or one side and thin plastic on the other. The latter sandwiches thin styrofoam, which I have always understood is sonically very porous. The styrofoam product comes in a big sheet and could be easily cut to fit inside my absorber. I will be recovering the fronts and using a spray adhesive to secure material to the back and planning on cutting either the styrofoam or the rigid panel to achieve a tight compression fit. see pics below What do you think, just try the styrofoam as it is inexpensive and would liven up each absorber but not prevent absorption ? ibb.co/zGFvfy9ibb.co/XzYghfnibb.co/Lthm5G3ibb.co/N3Hnsfd
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Post by kcatthedog on Feb 1, 2022 11:01:40 GMT -6
I bought the styrofoam and will experiment, think I’ll do a sweep as is, then but the styrofoam reflective side out over my two side first reflection points and two behind my monitors centre on front wall and see/hear!
I’ll just tape them in place on the fronts for now .
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Post by kcatthedog on Feb 3, 2022 10:09:40 GMT -6
Hey so I built those two new 6 inch 4 x 8 absorbers withreflective foil on the front m, rock wool rigid comfort board in the front position and 3 inch insulation in the back and sealed the back with some thin plastic I redid measurements best response so far, but still have problem kinda 50-100, red looks most regular has the new panels in place and Clarity and rt60 by 1/3rd octave played around with the subwoofer volume and crossover point, I think Eric wins the day as he first recommend sub woofer raising crossover to 120 and playing with the volume I think I’ll go ahead and build two new front tuned absorbers following the BBC plans and replace my 2 super chunks which are made poorly anyway. Stay tuned. ibb.co/5sR7tFvibb.co/z7cVRwL
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Post by Bat Lanyard on Feb 3, 2022 12:35:25 GMT -6
kcatthedog I built these membrane absorbers from Acoustic Fields for the back corners. They worked out great in my room. They have plans for several different designs based on ranges. I think the suite of plans was $49? Included traps and all sorts of other stuff. JFYI - another option. Could be a bit complex if you don't have the right tools though.
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Post by kcatthedog on Feb 3, 2022 12:46:02 GMT -6
Looks great, the bbc schematics come from real traps on line and include a detailed parts list, most of which I have and they can be made easily. I’ll start there, if I need anything after that, think I would just use Sonarworks. My room is much improved from where I started a month ago and at some point, you just need to get out of the rabbit hole !
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Post by Bat Lanyard on Feb 3, 2022 12:46:56 GMT -6
Looks great, the bbc schematics come from real traps on line and include a detailed parts list, most of which I have and they can be made easily. I’ll start there, if I need anything after that, think I would just use Sonarworks. My room is much improved from where I started a month ago and at some point, you just need to get out of the rabbit hole ! That's awesome, man. Look forward to more updates!
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Post by kcatthedog on Feb 3, 2022 12:57:50 GMT -6
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Post by kcatthedog on Feb 5, 2022 5:32:20 GMT -6
When I price out building 2-4 bbc panels , basically a similar cost to buying Sonarworks.
SW’s controls the frequency issues below 100hz. It not the reverb time issues, but if I just rolled off the lower bass with eq, then that energy isn’t put into the room in the first place. The bbc panels are toggle bolted to the drywall and caulked to be airtight, but could be moved, if and when I might move.
I feel like building the panels but,,,,
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Post by dok on Feb 5, 2022 10:56:36 GMT -6
Can't you demo Sonarworks to see if there's an improvement before you buy?
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Post by kcatthedog on Feb 5, 2022 13:09:33 GMT -6
I have owned it twice and did just demo it again twice, there was improvement but as I have retuned my room the improvement becomes more marginal.
It would be a way of being lazy rather then building a few more traps. Also, I think ID overpriced would prefer the old ref 4 at a lower price.
Anyway, I started making the new low bass traps today, turns out I have about half the materials I need, so cheaper to build then buy and this should fix delay and freq linearity: will complete and remeasure .
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ericn
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Post by ericn on Feb 5, 2022 19:09:20 GMT -6
I have been rebuilding my current absorbers, building out some to six inches deep 2x4 feet. Going to put these 2 on my front wall behind monitors and at my side first reflection points. I will be adding a rockwool rigid 2x4 1.5 inch comfort board to the front, retaining the fluffy rockwool behind. IF I can add an air gap, between these too I will. I have been reading about the benefits of adding a reflective front material (rpk) for mids and highs to ensure room does not get too dead. I have also read that people use thin plastic .7m or heavy paper for this as well. But at my local Home Depot they have two interesting products, that have a reflective material either in both sides or one side and thin plastic on the other. The latter sandwiches thin styrofoam, which I have always understood is sonically very porous. The styrofoam product comes in a big sheet and could be easily cut to fit inside my absorber. I will be recovering the fronts and using a spray adhesive to secure material to the back and planning on cutting either the styrofoam or the rigid panel to achieve a tight compression fit. see pics below What do you think, just try the styrofoam as it is inexpensive and would liven up each absorber but not prevent absorption ? ibb.co/zGFvfy9ibb.co/XzYghfnibb.co/Lthm5G3ibb.co/N3Hnsfd The front wall is tricky, I would never advise anyone to add reflective material till I spent time in the space, speaker choice position and position of everything else is just to big of a factor.
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Post by kcatthedog on Feb 5, 2022 19:35:44 GMT -6
I was experimenting. My rigid insulation is just a compression fit inside the frame so if I want to I can easily open them up and remove the reflective element. Anyway it’s just two of all the panels. You don’t see much of an apparent difference in measurement but the reflective panel shows a little more volume by freq here and there: I thought subjectively it seemed a little airier but it was subtle.
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