Acoustic Panels and Bass Trapping a new lounge

[DVDHack]

1 hour ago, playdough said:

There is no consideration for surface area of the trap , or near  air tight volumetric air space area application either, weather either are relevant is conjecture.

That's what I was asking you a while back, I think that's why they specify a 600x400mm size box.  I also read that you multiply that figure by 0.84 to account for the sealed air - need to re-look to get specifics.

Edited August 16, 2023 by DVDHack

[playdough]

7 hours ago, DVDHack said:

need to re-look to get specifics

I'm narrowing it down to 

1, Enclosure volume, to be more precise, covering it with a 0.84 doesn't really cut it, if the enclosure volume is  4 times the volume in this  case

2, Might be wrong, but this 900 x 600 sounds like about 15Kg ready to hang,  easy to handle. Not some mega membrane with a damped frame case that's "an element of structure" 

 

Progress photos, looking tidy. It's ready to go, core is in and the outer case is sealed to the wall. Went over it with the old thump the wall with the fist test and only found an aluminium window architrave on the outside of the cladding vibeing. Have to fix that before testing again. One of my favourite rig of all time, but I'm bias.

Edited August 16, 2023 by playdough

[playdough]

http://arqen.com/acoustics-101/room-setup-acoustic-treatment/

 

Quite enjoyed this read. 

Quote

 

Room correction software is NOT your secret weapon!

Alas, you can’t simply apply digital room correction to fix your acoustics.

Room EQ can tame some issues, but it can’t correct for long reverberation times or comb filtering caused by strong early reflections (like those nasty reflections produced by speaker-boundary interference).

To tame these problems you have two weapons in your arsenal: smart room layout and acoustic treatment.

 

[playdough]

On 15/08/2023 at 10:58 PM, playdough said:

There are 3 main seals to address during this insane experiment.

No, there are more, see photos.

No point rushing, do it properly miss nothing

[playdough]

Waterfall plot, Aug 17  the traps are in.  Looks half way there, better make another for behind the speakers, only 200mm off the wall.

Edited August 17, 2023 by playdough

[playdough]

Doesn't look too bad. Before reveal, time for a full manual EQ, see if I can improve the bass SPL Graph. Very strange happening things at 50Hz I dont understand'

Edited August 17, 2023 by playdough

[davewantsmoore]

6 hours ago, playdough said:

Room correction software is NOT your secret weapon!

Alas, you can’t simply apply digital room correction to fix your acoustics.

You might have misunderstood what I was trying to say, when I told you earlier to correct your charts.

[playdough]

3 minutes ago, davewantsmoore said:

misunderstood

No, no I didn't, not my words either so no responsibility for them, check out the link with that post. 

My charts show steady reverb mitigation  progress to 40Hz with the new kit.

[playdough]

@davewantsmoore

Comb filtering eliminated (which is prevalent in untreated areas an evil thing), the lounge is at a point it's actually worth  sitting down with a coffee, and getting all critical. 

There is 1 more wall to do

[davewantsmoore]

1 hour ago, playdough said:

check out the link with that post

Which post/link, sorry?!

[playdough]

9 hours ago, playdough said:

http://arqen.com/acoustics-101/room-setup-acoustic-treatment/

 

Quite enjoyed this read. 

Quote

 

Cheers Dave. Enjoy was ok.

[playdough]

Is this any easier to read @davewantsmoore 

Sounds thin, I like more bass   

Give the old walrus ported bass  cabs a break they kind of wig out doing sub to 150Hz even with EQ, and I'm fairly well sure those horns  hit at a brick wall down from 250 Hz, never the less here it is.  

 

[playdough]

To be fair I dunno how the chip amp is doing it, 25w pc. Pass,, doesn't even get warm much and it's been on for months. 

[almikel]

On 16/08/2023 at 1:09 PM, playdough said:

Only 3 variables, with an outcome of  frequency, mass, depth and 600 are considered, in this particular calculator "accepted as the norm" 

There's not the same science developed around mass loaded vinyl (MLV) traps compared to say QRDs or plain absorption with a defined gas flow resistivity...it will come...and your own experiments contribute to the knowledge pool 

 

Props to you for having a crack at building your own MLV traps to manage bass in your room!

 

I've been interested in MLV traps for a long time, but I've never made sawdust, as my room is lightly constructed and leaks out all the low bass, and as a lazy DIYer, EQ and absorption treatment is doing OK for a great "in room" bass response in my room.

 

Without actually having built a mass loaded vinyl trap, but having some understanding of the science:

• an MLV trap needs to be sealed to operate
• MLV traps are still "membrane" traps - yes much lower Q than using say thin plywood as the "membrane", but their bandwidth of absorption will still be vastly narrower than plain absorption - hence they need to be "designed" to trap specific frequencies 
• the absorption inside a sealed MLV trap broadens/lowers the Q (identical to any other membrane trap with absorption inside.)
• you likely could interchange MLV trap depth with trap volume...but no-one has come up with the calcs yet

The usual rules apply for managing "in room" bass - traps need to be large and deep to manage bass...not dissimilar to Hoffman's iron rule for subs

 

cheers

Mike

[almikel]

35 minutes ago, playdough said:

Is this any easier to read @davewantsmoore 

Sounds thin, I like more bass   

Give the old walrus ported bass  cabs a break they kind of wig out doing sub to 150Hz even with EQ, and I'm fairly well sure those horns  hit at a brick wall down from 250 Hz, never the less here it is.  

 

 

36 minutes ago, playdough said:

Sounds thin, I like more bass   

I'd be focusing on getting the baseline frequency response more even - you have a big dip 30-60Hz and another at 100-150Hz - treatment can't help as it's at time=0.

 

Are either of these dips close to crossover points in your setup?

 

cheers

Mike

 

 

[playdough]

@almikel

Thanks for you post's a lot to absorb and there is more I think I ve found out , tomorrow

Been a big day and brown out imminent.

Tried to make some cool graphs of the traps up sealed on the wall while dozing off

 

Looks ok to me some progress

 

 

[playdough]

11 minutes ago, almikel said:

points in your setup

There is no crossover until 250Hz, (DSP convolving does SFA really  from what Im seeing) the pair of 21" in a big ported box,  is what she is in this lounge. Might be better with Dirac 

I hope so some day get some better speakers, maybe smaller, sadly we are stuck with the spikey test bass line speaker in the graphs, for now. sorry

 

[davewantsmoore]

10 hours ago, playdough said:

Is this any easier to read @davewantsmoore 

Not really.

You could try some small smoothing, assuming there is none.

Or you could use a spectrogram with "normalise peak to each frequency " box checked.

 

Without a before and after chart, with the frequency response totally normalised (or EQed to within 5dB, or similar) then there's just little useful information in the charts.   I can't really tell if it's working or how much.    DOn't get me wrong, I'm sure it is (doing something)... but.

 

10 hours ago, playdough said:

Sounds thin, I like more bass   

Don't worry about how it sound for this part (as you are only comparing the relative decay of A vs B)  ... or just choose a different target that you do like the sound of.

[davewantsmoore]

Eg. show the normalised spectrogram of the before and after.

 

Waterfall and decay charts are pretty, but also usually pretty useless.

[DVDHack]

10 hours ago, playdough said:

Looks ok to me some progress

95-100dB....  That's really loud.  100dB is safe to listen to for about 20 mins.  Think I've said before I listen at about 70dB with 80dB peak.  That's from a dB meter with C weighting.

Edited August 17, 2023 by DVDHack

[davewantsmoore]

8 minutes ago, DVDHack said:

80dB peak

It depends a lot on the peak to average ratio of the music as to how loud this sounds.

If the 100dB peaks are very short, and the average level is low, then it's not too bad.

... but that's pretty loud for a test tone that has ~ peak == average.   

 

... but it's the right level to measure at if you're looking to uncover worst cases.

[playdough]

12 minutes ago, DVDHack said:

Think I've said before I listen at about 70dB with 80dB peak

We back here again,

 

I'm trying to test reverberation and the performance of the 5m2 plus of 2 MLV Bass traps

 

I have earmuffs on for testing

 

Sometimes another Audiophile will drop by and the system will get a bit of a rev with music at 90dB but mainly I respect others trying to  to sleep and not disturb, others that live here.

 

They were quite disturbed enough when the plastering was happening, nightmarish 

 

 

[DVDHack]

1 minute ago, davewantsmoore said:

It depends a lot on the peak to average ratio of the music as to how loud this sounds.

If the 100dB peaks are very short, and the average level is low, then it's not too bad.

... but that's pretty loud for a test tone that has ~ peak == average.   

 

... but it's the right level to measure at if you're looking to uncover worst cases.

I guess it does depend on the music, if you include canons in the 1812 it's all good but if it's anything recently recorded music they seem to compress everything to one level.  
 

I'm not sure loud level optimisation for a room is the way to go, over pressurising the room might just create problems that dint normally exist.  Also I'm interested in understanding what happens to speaker performance when you drive them at different levels.  I've had speakers that only sound good when they're loud, as an example.  
 

I have a mate who optimised his room, when he was done he added a 'house curve' to bring g the bass back....  I prefer to optimise my room at a lower level and when the obvious problems are dealt with spend some time listening before going overboard.  I learnt from my mistakes in the first room.  The second room sounds better now and I've only done a few things.

[playdough]

7 minutes ago, davewantsmoore said:

loud for a test tone

What better to TEST a membrane room treatment  theory

 

A very loud test. Rises from 5 Hz and has decent magnitude at 12Hz, 

The trap is doing things from frequencies reproduced from above  these figures. 

 

This thread is not about Speakers and a ruler flat response

It's about room decay times and testing tones

 

We could use a book shelf speaker which would probably give you what you want Dave, a sanitised FR that drops off the scale at 30Hz or we could use the rig in place which is a bit lumpy, but quite obviously useful outputting from at 10Hz and beyond

 

No amount of EQ  has helped to fix the 50Hz suckout measured in the graph, it's what the room does to the bass.  It tends to stay similar, I can only do some things with EQ, that's becoming very obvious 

 

Slow progress with the MLV Trap, has gone some way to fix this. More than digital convolution AAMOF

 

 

 

[playdough]

25 minutes ago, DVDHack said:

looking to uncover worst cases.

Imagine  if you will we have a few largish bass speakers to test some 15's and 18s sealed/ ported, Wbinned , for fun and merriment over a beer, steak and cheese platter, whatever you fancy

We know already the room curve, what it does at 50Hz that spike peak suckout. The room trapping however has made a monumental difference to the, bloated room flex bass that I was experiencing

We have 25w RMS to do this and we know already the 21's hit 105dB at 20Hz at 25w@3.5m

 

Would be a good job, fun.