frednork Posted February 27, 2020 Share Posted February 27, 2020 (edited) looking for info/experience with Helmholtz absorbers and treating ringing. Is it the right absorber for the job? will it work? this it the fr decay this is the room from https://amcoustics.com/tools/amroc?l=570&w=440&h=270&re=EBU listening room and potential designs for helmholtz from http://www.acousticmodelling.com/helmholtz.php Edited February 28, 2020 by frednork Link to comment Share on other sites More sharing options...
andyr Posted February 27, 2020 Share Posted February 27, 2020 5 hours ago, frednork said: looking for info/experience with Helmholtz absorbers and treating ringing. Is it the right absorber for the job? will it work? this it the fr decay Wow! That indeed is a troublesome spike! Can you tell me how you generate the 'Spectral Decay" plot? In the REW version I'm running, I only see these plots: Thanks Andy Link to comment Share on other sites More sharing options...
frednork Posted February 27, 2020 Author Share Posted February 27, 2020 42 minutes ago, andyr said: Wow! That indeed is a troublesome spike! Can you tell me how you generate the 'Spectral Decay" plot? In the REW version I'm running, I only see these plots: Thanks Andy Andy, its the decay tab Link to comment Share on other sites More sharing options...
andyr Posted February 27, 2020 Share Posted February 27, 2020 42 minutes ago, frednork said: Andy, its the decay tab Aah, thanks fn. (I don't get a 'Spectral Delay' heading. ) Actually, here is mine: Very different to yours ... and my room is a similar size: 5.8 x 3.6 x 2.7m. I have no idea whether the above shows me I have any issues! (Whereas your Decay plot clearly showed the large anomaly at 37Hz.) Andy Link to comment Share on other sites More sharing options...
tubularbells Posted February 27, 2020 Share Posted February 27, 2020 Your obviously a pipe organ music fiend as that would not present as an issue for the majority of regordings I reckon. My 50hz issue on the other hand dangled beneath the dog so bad that as your aware (and have observed) necitated radical changes to tame. Link to comment Share on other sites More sharing options...
frednork Posted February 27, 2020 Author Share Posted February 27, 2020 (edited) 1 hour ago, andyr said: Aah, thanks fn. (I don't get a 'Spectral Delay' heading. ) Actually, here is mine: Very different to yours ... and my room is a similar size: 5.8 x 3.6 x 2.7m. I have no idea whether the above shows me I have any issues! (Whereas your Decay plot clearly showed the large anomaly at 37Hz.) Andy look ok above 1k but what about below 1k which is where problems occur, would be good if you can adjust the scale to show from 10-20hz up to 20k and on the y axis to show down to about 30db Edited February 27, 2020 by frednork Link to comment Share on other sites More sharing options...
frednork Posted February 27, 2020 Author Share Posted February 27, 2020 55 minutes ago, Tubularbells said: Your obviously a pipe organ music fiend as that would not present as an issue for the majority of regordings I reckon. My 50hz issue on the other hand dangled beneath the dog so bad that as your aware (and have observed) necitated radical changes to tame. Cant say I notice it that much but the objectivist part of me thinks it might better if I fix it! This is yours when on the long wall and mine with a similar scale Link to comment Share on other sites More sharing options...
tubularbells Posted February 27, 2020 Share Posted February 27, 2020 Hmmm yours is way flatter but mine is more fun But nah it would be interesting to see what mine now measure at (once again on the long wall but way further out) 1 Link to comment Share on other sites More sharing options...
frednork Posted February 27, 2020 Author Share Posted February 27, 2020 1 hour ago, andyr said: Aah, thanks fn. (I don't get a 'Spectral Delay' heading. ) Actually, here is mine: Very different to yours ... and my room is a similar size: 5.8 x 3.6 x 2.7m. I have no idea whether the above shows me I have any issues! (Whereas your Decay plot clearly showed the large anomaly at 37Hz.) Andy Ahh I see you have shown from below 1 k but we just cant see it. you need to change from linear scale to logarithmic on the x axis Link to comment Share on other sites More sharing options...
andyr Posted February 27, 2020 Share Posted February 27, 2020 45 minutes ago, frednork said: Ahh I see you have shown from below 1 k but we just cant see it. you need to change from linear scale to logarithmic on the x axis Sorry about that! I think this is it? Looks a lot worse! Andy Link to comment Share on other sites More sharing options...
Ittaku Posted February 27, 2020 Share Posted February 27, 2020 I have the tunable helmholtz resonators in my room. They do not go down to 37Hz. Lowest setting is 56Hz. So for that particular type of resonator, the answer to your question is no. Link to comment Share on other sites More sharing options...
frednork Posted February 27, 2020 Author Share Posted February 27, 2020 8 minutes ago, andyr said: Sorry about that! I think this is it? Looks a lot worse! Andy I could be wrong but it looks like the slices are too short . try to set it up like below for a good comparison to mine and zoom out the y axis till you can see 20 dB. if you hit the controls icon the popup screen on the right top side it will pop up just copy the settings as on mine. Link to comment Share on other sites More sharing options...
frednork Posted February 27, 2020 Author Share Posted February 27, 2020 19 minutes ago, Ittaku said: I have the tunable helmholtz resonators in my room. They do not go down to 37Hz. Lowest setting is 56Hz. So for that particular type of resonator, the answer to your question is no. yes have looked at those but alas too small for that design to go that low Link to comment Share on other sites More sharing options...
andyr Posted February 27, 2020 Share Posted February 27, 2020 8 hours ago, frednork said: I could be wrong but it looks like the slices are too short . try to set it up like below for a good comparison to mine and zoom out the y axis till you can see 20 dB. if you hit the controls icon the popup screen on the right top side it will pop up just copy the settings as on mine. Thanks, fn. How about this? Andy Link to comment Share on other sites More sharing options...
frednork Posted February 27, 2020 Author Share Posted February 27, 2020 @andyr looks a bit too different . The whole decay is only about 30db and should be around 60+. Did you hit the default settings button by chance? settings are time slice 50ms window 500, rise time 100 smoothing 1/12 Link to comment Share on other sites More sharing options...
andyr Posted February 27, 2020 Share Posted February 27, 2020 (edited) 3 hours ago, frednork said: @andyr looks a bit too different . The whole decay is only about 30db and should be around 60+. Did you hit the default settings button by chance? settings are time slice 50ms window 500, rise time 100 smoothing 1/12 Yes, had those settings - as you can see from the below graph. However, it's possible the smoothing in my previous graph was 1/48? Andy Edited February 27, 2020 by andyr Link to comment Share on other sites More sharing options...
Ittaku Posted February 27, 2020 Share Posted February 27, 2020 8 minutes ago, andyr said: Yes, had those settings - as you can see from the below graph. However, it's possible the smoothing in my previous graph was 1/48? Geez you're measuring it loud! You're game. Link to comment Share on other sites More sharing options...
frednork Posted February 27, 2020 Author Share Posted February 27, 2020 (edited) 20 minutes ago, andyr said: Yes, had those settings - as you can see from the below graph. However, it's possible the smoothing in my previous graph was 1/48? 14 minutes ago, Ittaku said: Geez you're measuring it loud! You're game. Ok def looks better than mine! but still some ringing at 50. regarding loudness it doesnt make sense. It actually looks to me like you measured at pretty low volume and then somehow the levels got pushed up to 100. if you look at decay for yours at around 2k over the 500ms its about 45db on mine its about 55db, on dougs its about 65db. And ambient noise at around 50db thats a noisy room! Edited February 27, 2020 by frednork Link to comment Share on other sites More sharing options...
andyr Posted February 27, 2020 Share Posted February 27, 2020 (edited) 38 minutes ago, frednork said: Ok def looks better than mine! but still some ringing at 50. regarding loudness it doesnt make sense. It actually looks to me like you measured at pretty low volume and then somehow the levels got pushed up to 100. if you look at decay for yours at around 2k over the 500ms its about 45db on mine its about 55db, on doug's its about 65db. And ambient noise at around 50db thats a noisy room! Thanks, fn. Aah, OK - now I see how to interpret the graph. I presume my decay of 45dB (at 2kHz) instead of yours at 55dB ... means my room is 'livelier' than yours? But which is 'better' - 65dB of decay ... or 45dB? Yes, mine is a noisy room - your level (of 20dB?) is much better! Andy Edited February 27, 2020 by andyr Link to comment Share on other sites More sharing options...
frednork Posted February 28, 2020 Author Share Posted February 28, 2020 Hmm, still not 100% convinced, but regardless you dont have a big ringing problem like me. Happy to pop round sometime and measure with my mic to compare ( and more importantly have a listen to those big maggies) Link to comment Share on other sites More sharing options...
Ittaku Posted February 28, 2020 Share Posted February 28, 2020 37Hz wouldn't happen to be the tuning of the ports on your woofers, would it? Link to comment Share on other sites More sharing options...
frednork Posted February 28, 2020 Author Share Posted February 28, 2020 Just now, Ittaku said: 37Hz wouldn't happen to be the tuning of the ports on your woofers, would it? good thought but sealed cabs Link to comment Share on other sites More sharing options...
Ittaku Posted February 28, 2020 Share Posted February 28, 2020 (edited) 4 minutes ago, frednork said: good thought but sealed cabs Fair enough. Mine does a huge jump from when the (closed) sub kicks in at 35Hz and remains high below that. Given the nature of ultra low frequencies I'm not sure it's much of a problem, but sure anything can always be improved upon. Edited February 28, 2020 by Ittaku Link to comment Share on other sites More sharing options...
frednork Posted February 28, 2020 Author Share Posted February 28, 2020 2 minutes ago, Ittaku said: Fair enough. Mine does a huge jump from when the (closed) sub kicks in at 35Hz and remains high below that. Given the nature of ultra low frequencies I'm not sure it's much of a problem, but sure anything can always be improved upon. yes not the end of the world but just rethinking my treatment and how this might fit in and is it likely to work and worth the effort Link to comment Share on other sites More sharing options...
Ittaku Posted February 28, 2020 Share Posted February 28, 2020 36 minutes ago, frednork said: yes not the end of the world but just rethinking my treatment and how this might fit in and is it likely to work and worth the effort For what it's worth, I have a (main driver related) peak and ringing at 56.6Hz and have tuned the varibass helmholtz resonators to that frequency and found their effect to be about 3-4dB attenuation of ringing. 1 Link to comment Share on other sites More sharing options...
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