bluepill193 Posted June 6, 2016 Posted June 6, 2016 I have a boom at 70Hz. Some 蔡琴 tracks on the 金片子 become unlistenable. Funny thing is it is present no matter how far i move the MLP, at sitting height. But it disappears when I stand up! Is this due to standing waves between floor n ceiling? Any DIY options to solve it? Thinking of making 2" rockwool panels to place behind speakers, with 2" air gap, dunno whether will help at all?
joamonte Posted June 6, 2016 Posted June 6, 2016 On 06/06/2016 at 6:35 AM, bluepill193 said: I have a boom at 70Hz. Some 蔡琴 tracks on the 金片子 become unlistenable. Funny thing is it is present no matter how far i move the MLP, at sitting height. But it disappears when I stand up! Is this due to standing waves between floor n ceiling? Any DIY options to solve it? Thinking of making 2" rockwool panels to place behind speakers, with 2" air gap, dunno whether will help at all? Bass trap all along ceiling corner will help.
bluepill193 Posted June 6, 2016 Posted June 6, 2016 Thanks Bro. Along the whole ceiling/wall junction, or just at the 4 tri-corners?
joamonte Posted June 6, 2016 Posted June 6, 2016 best can do whole ceiling junction , if cannot do 4 corner and center make sure the panel use work down to 70 hz
andylovesaudio Posted June 6, 2016 Posted June 6, 2016 On 04/06/2016 at 2:52 AM, joamonte said: siblilance most of the time is cause by system matching instead of room acoustic.... This diffuser scatter sound above 1 kHz and impove mid range clarity provided you system and room wasn't sound bright, if you have siblilance problem possible it will get more obvious after using it. But for those want more detail and resolution from their system can consider this panel...it help to reduce some mid bass muddyness too. @Joamonte....thanks...:))
andylovesaudio Posted June 7, 2016 Posted June 7, 2016 You think the skyline diffuser works...since is just styrofoam?
joamonte Posted June 8, 2016 Posted June 8, 2016 On 08/06/2016 at 12:37 AM, tane0019 said: Look easy to DIY ;D ;D ;D My guess is the height they anyhow hantam one lah, the 2 D diffuser step suppose to follow a mathematic sequence... The skyline is good diffuser , only thing is the bandwidth is quite limited.
joamonte Posted June 10, 2016 Posted June 10, 2016 There are some enquiry about how to use my BAD panel, this 4 position is where I would recommend to feel the effect of the panel first. 2 pair behind speaker ,another 2 pair at the wall opposite of speaker if have enough budget , between the diffuser use thin Rug or fabric to reduce some high frequency reflection if the sound become too "thin", this BAD panel tends to add in some high frequency above 1 kHz make the sound tonal like become "thinner" , it is Psychological illusion because when there are more high frequency, mid range will sound like become leaner ..... so the thin rug will help to reduce high frequency reflection at center area between speaks and regain the "thickness" of the sound , at the same time , sound stage become wider and attack of the music transient will improve because of the diffuser. Cover the TV screen with cotton fabric if there are TV between the panel, usually I would recommend use diffuser to cover TV screen but in the case of BAD foam panel , soft fabric is perfect for the job. For those who cannot glue the panel on on wall, this is what I did in my room . Tension Poster hanger, I brought 4 pole from bas Basah complex ground floor This is from Taobao https://item.taobao.com/item.htm?spm=a230r.1.14.31.jVwpwM&id=35672018041&ns=1&abbucket=9#detail After this 4 area is treated , use more panel as mid bass trap at room corner or ceiling area above speaker and listener, that would bring in more improvement on the high frequency dispersion , reduce muddy bass and make the room ceiling "sound higher".
andylovesaudio Posted June 10, 2016 Posted June 10, 2016 @Joamonte....very useful information...esp for those who are approaching room treatment by trial and error and by ear...ie...no measurement/non scientific.
joamonte Posted June 10, 2016 Posted June 10, 2016 On 10/06/2016 at 6:43 AM, andylovesaudio said: @Joamonte....very useful information...esp for those who are approaching room treatment by trial and error and by ear...ie...no measurement/non scientific. Every room situation and problem is different, measuerment useful at one room don't mean it will be useful on another room, measurement is very useful when comparing before and after in the same room, but at the other room we might need different result to solve other kind of problem , for example , a bass trap work at 60hz solve a room 60 Hz problem , but it don't mean it will solve another room bass problem at 80 Hz....if you get what I mean. ....the point I mention above are for general purpose of improving sound , I sure it will work at most different situation ; if anybody want to use the panel for specific purposes (eg early reflection point) other than listening , some measurement of how the panel affecting the overall sound is prefer...but again, that measurement result is only apply in that room---unless you room is anechoic chamber. ;D
andylovesaudio Posted June 10, 2016 Posted June 10, 2016 Yup...makes a lot of sense. I am attempting to obtain a thicker sound with more relaxed HF. I tried absorbers (4 inch thick foam panels) between speakers ...result was the reverse of what I am seeking. Removed that. Then I treated back wall reflection point with 2 inch thick foam. Back wall is actually a floor to ceiling wardrobe. My head is only a foot in front of foam. More definition but HF bit more rough and overall presentation "phasey" sounding. Could be placebo effect though. Front wall now just thinnish drapes covering glass windows. Side walls 1st refection treated with 4 inch thick foam panels and front wall corner bass traps were constant. Gonna leave the back wall treated with foam for now and play with speaker position. See how it goes.
joamonte Posted June 10, 2016 Posted June 10, 2016 This is a brief summary of where to put the panel , all under different room layout. The best point in the drawing is refer to where the BAD foam panel should put when first trying the effect. 2nd best point is under some situation when cannot place the panel at the best point, you can put it there. Bear in mind that the drawing is design for room treatment for sound improving purpose, it is not for dealing with any specify room acoustic problem, most room will benefit from this arrangement but if your room have other serious problem like standing wave, flutter echo , bright etc , this package will not help much....it do help solve If you feel your room is too dead though. As for the bass trap , this panel will make the room corner become more "open" due to the mid bass absorption and better high frequency dispersion at corner, but again , if you feel your room is already a little to bright , boardband bass trap might be better choice. For ceiling treatment , no matter what room , my principal of treatment is the same -- 2/3 diffuser, 1/3 thick absorption , but the light weight BAD foam panel Is quite easy to paste directly onto the ceiling... Skyline is also suitable for ceiling but some may find those design look bad for Fongshui , especially in living room, BAD foam in white on the other hand look quite ok to me. ;D
joamonte Posted June 11, 2016 Posted June 11, 2016 Got back my measurement kit today, finally able to do some measuerment in my new room. After some adjustment , the result is this... 1/12 smoothing , left + right channel 1/12 smoothing , left and right channel Most of the frequency range of left and right channel are matched , this indicated that my effort of try to to make the left and right as symmetrical as possible do work well... During my measurement on different room , I saw very big different frequency response at left and right channel, especially bass, that indicate that that room will have problem in getting the best sound stage and imaging from 2 channel play back 1/3 smoothing Other than frequency above 10 kHz, most frequency are within +4 - 1 dB.....the high frequency roll off is due to the attenuation of high frequency power responce, the software pick the sound within a period of time frame and because high frequency "died off" faster than lower frequency, the graph will show this roll off as the overall amount of high Frequncy is lesser than mid and low( have more energy to sustain in the room longer), other thing like distance from the speaker to the mic and the off axis dispersion responce of tweeter also affect how much the HF roll off in the graph... This don't mean the sound become too dark or too dull, it is just a usual responce of measurement and in fact, if the FR is flat all the way to 20 kHz , most likely the system will become too bright. Side note: and that is the reason why high frequency diffuser is need in a room to help the high frequency "spread" more evenly in the room, while absorbing panel usually only make the sound become too dull.
joamonte Posted June 11, 2016 Posted June 11, 2016 The Reverberation Time graph. I am quite happy with the result, the RT stay below 0.4 sec and is very linear from low 60 Hz to high 10 kHz , the peak at 100 Hz actually is the aircon fancoil blowing sound disturbing the result ( will show it at the waterfall graph later) As we can see now, at 100hz there are a background noise at low level refuse to dead of, that is cause by my aircon fancoil , this is the reason why I alway emphasis try to put the aircon fancoil at the center of the room or use 2 fancoil at both side of the room, it is quite annoying to hear the noise alway come from one side of the room. The overall result for the water fall graph indicate than my bigger Helmholtz bass trap only work to 35 Hz , we can see the dip at 35 Hz in the graph, quite disappointed , I think maybe I have caculated wrongly or the contractor have did something changes without notice me, will need to modify the port later to try make it absorb Lower to 30 Hz ( my lowest room mode) :'( Good news is my side wall ceiling Helmholtz bass trap work well down to 50 Hz, I did not use a single boardband bass trap in the room ( real trap, Rockwool panel etc) but the mid bass from 50 Hz to 200 Hz is quite fine, spectrograph also show it. Clean and clear from 50 Hz to the top :)
joamonte Posted June 11, 2016 Posted June 11, 2016 Below is more technical part for those who are more familiar with this measurement things......hope some expert can give me more point of view. Step response , it show that my speaker tweeter is revise polarity connected , the 2nd rise at 1.5 msec after I suspect coming from the back fire bass reflect port....anyway there are nothing much I able to adjust on this but I think maybe seal up the port after I connect a pair of subwoofer wasn't a bad idea at all (if my suspect is true). 0.1 ms smoothing, I think the decay is quite dense and smooth , it show that the diffusion in the room is enough , dense reflection come back after 5 msec of direct sound give me some spaciousness feel ( ref from graph below) but I hope I could remain more energy to give me even more ambient ........ so 2 more floor to ceiling full height diffuser , to cover some of the absorbing wall of my room , is in process and on the way from the Carpenter . ;D Tomorrow I will try to integrate the pair of subwoofer into this system.
Jag Posted June 12, 2016 Posted June 12, 2016 Great measurements. Wouldn't worry too much about the step response. Only very few speakers that pay attention to transient response in speaker design will get this right. But I don't consider this to be a major issue to most situations. Electrostatics and few dynamic speakers (Vandersteen is one of them) tend measure well. http://www.stereophile.com/content/measuring-loudspeakers-part-two-page-3#hBSgGXhkm1Q00w0D.97 ETC is very good. Your efforts are paying off! I guess you already know your 30hz mode and 50hz antimode problem. Hope you get to alter your HR to cut off that 30hz slow decay resonance. I'm guessing your dual subs will resolve the 50hz antimode. I wish I have the means to treat my HT acoustically as what you've done....
joamonte Posted June 12, 2016 Posted June 12, 2016 Someone email me ask about how I do the side wall ceiling bass trap....this is how I do it, we call it Helmholtz Slot Absorber , it can be tune to different frequency if do it in this way, just by adjust the distance between the slot, you can use different slot size to absorb different bass frequency or adjust the slot same distance to solve some standing wave problem at mid bass frequency, work quite well in my room. Here is the caculator http://www.mh-audio.nl/acalculators.asp#showcalc
joamonte Posted June 12, 2016 Posted June 12, 2016 On 12/06/2016 at 10:37 AM, Jag said: Great measurements. Wouldn't worry too much about the step response. Only very few speakers that pay attention to transient response in speaker design will get this right. But I don't consider this to be a major issue to most situations. Electrostatics and few dynamic speakers (Vandersteen is one of them) tend measure well. http://www.stereophile.com/content/measuring-loudspeakers-part-two-page-3#hBSgGXhkm1Q00w0D.97 ETC is very good. Your efforts are paying off! I guess you already know your 30hz mode and 50hz antimode problem. Hope you get to alter your HR to cut off that 30hz slow decay resonance. I'm guessing your dual subs will resolve the 50hz antimode. I wish I have the means to treat my HT acoustically as what you've done.... Thanks Jag for the comment. Yes I am aware of the 30 Hz peak even before the room is built , that why a huge HR is built but unfortunately some calculation is wrong...I will use the PEQ of the sub to solve this problem temporary , but I will need to do some caculation again to figure what is wrong with the bass trap.. :'(
joamonte Posted July 1, 2016 Posted July 1, 2016 http://www.xtremeplace.com/yabbse/index.php?topic=233719.0 For those who show interest for my BAD foam panel , here is it , pls pm me for collection.
wechnivag Posted July 17, 2016 Posted July 17, 2016 Bro Joamonte, I'm wondering what is the way you normally deal with speaker- boundary interference notch from sidewall and front wall behind the speakers? Moving the speakers around with placement tweaking just moves the cancellation notch to a different frequency, but doesn't really eliminate the problem. Thanks for your advice! Sent from my GT-I9505 using Tapatalk
joamonte Posted July 17, 2016 Posted July 17, 2016 On 17/07/2016 at 3:02 PM, wechnivag said: Bro Joamonte, I'm wondering what is the way you normally deal with speaker- boundary interference notch from sidewall and front wall behind the speakers? Moving the speakers around with placement tweaking just moves the cancellation notch to a different frequency, but doesn't really eliminate the problem. Thanks for your advice! Sent from my GT-I9505 using Tapatalk 1) soften the wall, partition wall is better than concrete wall. 2) for HT, place the speaker as close to front wall as possible as it will shift the reflecting freq. higher , which can be easily damp by absorber or diffuser. 3) for 2 channel try shift the speaker as far away from back wall as possible , this will lower the reflecting freq. and narrow the Q of the dip. But actually IMHO SBIR is not a too huge problem although it don't look good in measurement , the reason is human ear is not so sensitive to dip especially when the Q of the dip is high....
wongkahkui Posted July 18, 2016 Posted July 18, 2016 Can anyone introduce room acoustic company/person whom is reliable and superb? I'm keen to improve my area but just too bad in DIY...
wechnivag Posted July 18, 2016 Posted July 18, 2016 On 17/07/2016 at 6:29 PM, joamonte said: 1) soften the wall, partition wall is better than concrete wall. 2) for HT, place the speaker as close to front wall as possible as it will shift the reflecting freq. higher , which can be easily damp by absorber or diffuser. 3) for 2 channel try shift the speaker as far away from back wall as possible , this will lower the reflecting freq. and narrow the Q of the dip. But actually IMHO SBIR is not a too huge problem although it don't look good in measurement , the reason is human ear is not so sensitive to dip especially when the Q of the dip is high.... I'm just looking at the sbir calculator, and an idea struck me. The sbir actually cause nulls and peaks. Is it possible to position the front and side wall distance so that the first sidewall null is filled in by the first front wall peak? Then only the front wall null is left.. For example, 650mm from front wall will have null at 132hz, peak at 396Hz. 215mm from sidewall has the null at 399hz. I'll have to give it a try later with measurements. Sent from my GT-I9505 using Tapatalk
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