On 25/08/2023 at 9:00 AM, playdough said:

There is a cunning plan a foot to hang a group of QRD's at a first reflection point,

If you're designing QRDs, make sure you use QRDude to "design" them - an amazing free tool!

 

https://www.subwoofer-builder.com/qrdude.htm

 

I'm happy to assist

 

Mike

Edited August 27, 20232 yr by almikel
additional info

4 hours ago, almikel said:

there's less science available for limp mass traps

It's not that the science isn't there it's just that it is very complicated.  It required accurately measuring the mechanical properties of the material... and this is more difficult than it sounds.

It's much easier just to build and measure 17 prototypes to get where you need to go.

7 minutes ago, davewantsmoore said:

It required accurately measuring the mechanical properties of the material..

is the equation above wrong then?  Seems to me measuring the mass and the depth isn't particularly difficult.

A short recap of the whole job yea.

Started this job 2 years ago, was in 2 stages.

First stage, strip it out utterly but leave a sink hot and cold tap, oven a power point. Took out a structural chimney, inner centre load bearing wall, old door and a window. Re  window all double glaze, UV Tinted bronze. Add a window and install a new DG slider door. 

Ensuing timber floor repairs, re hash internal walls, more floor repairs.

So, after a fair bit of studwork, installing 2 off 5m internal beams center supported with a single, figured, blackwood post. Windows within a mm. 

Put a skin of Tyvek round and went into Winter, had a rest for a couple of months. Had a little paid help on that, was no small task.

Second round I was a lone ranger this time.

 

"I could hear the water splash and the dunny flush  in the neighbours place early in the morning sitting in my kitchen having a coffee" Tyvek comes off after a few months of stormy weather. The Dog almost went crazy a cat was getting in taking it;s grub during the night.

 

Soundproofing the weatherboard was a huge priority, the place is elevated. In the 20 odd years the Cops have been here 1 time for excessive noise. Prefer not to see them at all.

 

I found a local sawmill who was doing these nice macracarpa 25mm x 110 kiln dried, T and G machined  external cladding, Paid the man for 400Lm pack. Wallet hurt for a month after that.

Ripped  off the Tyvek and installed Foil Board, 5.5mm jacket onto the whole frame and gable. Carefully all taped and sealed, When that went on things changed. 

The Maccra boards went on after, 3 weeks of mostly ladder work, they went on quite nice 

 

 Glued every end, corner, joint, knot, crack. pre drill and punch every galvanised nail for filler before painting. 

So, after a month of that I had a week off. Came up ok, happy.

Walls above are  where the 21's and other noise are, so there was a need to soundproof it.

Started on internals about 10 weeks or so ago 🙂 just ticking over building every day.

Had the wiring done. and insulated with heavy quality bats.

Nothing special about the double plaster job  although there was a metal angle iron  glued and screwed the whole way around the floor, lounge, hall, kitchen. Surprising the draft, rodents and noise, gets in a home at this floor wall intersection.  Double plaster, 57 sheets later, more steel around for a square set. Was a big terrible job. Used Stud adhesive fairly well, 5 or 6 buckets, fist pumped the entire job, for those sheets that like to flap on a stud.

A month ago I started a thread here. 

Just needed a post to recap. 

 

Thanks for replies I thought the thread had gone dead 🙂, I did take a few measurements today and will spend some with answers and an explanation for what I"ve done over a coffee tomorrow morning, yes there is a lot to this job. I didn't really know how it would end, but I'm here,

Just listening for a spell. Soaking it up.  Cheers

 

Playdough

 

Edited August 27, 20232 yr by playdough

1 hour ago, DVDHack said:

is the equation above wrong then?

It's just an approximation....  I haven't seen this one before, but they are usually based on things like the membrane moving without deforming at all (like a big simple piston), and that whatever is inside is linear.

 

To really work it out, you need to determine how the membrane will move... and this can be quite complicated.   In a very simplistic sense you could say that the membrane will move at it's lowest eigenmode, in which case the (area) dimensions of the membrane would be relevant (this is a discussion we were having earlier in this thread, about the trap needing to be a certain size) ... but this relies on the the notion that the membrane will move in a consistent in/out over it's whole surface... and that's likely overly simplistic.

 

It certainly doesn't hurt to have the traps big... but making them precise dimension relations of the frequency of interest isn't needed.

 

I would say do not get hung up at all on the calculators... use them to get a feel for a starting point, and then build something janky, and measure the results... and the go back and build again.   This is how most pros go it (if the opportunity exists), only their calculators might be a bit more complex, and the prototypes a bit less jank.

31 minutes ago, davewantsmoore said:

I would say do not get hung up at all on the calculators

I'll probably achieve what I need with just absorption, both my rooms are a good size.  The largest room needed very little treatment to achieve excellent sound quality, Im delighted with how it's turned out and quite by dumb luck I sit at the 38% mark in the room and I have side firing subs.  The other room is smaller and I've over dampened it, Im adding diffusion to reduce absorption of mids and highs (BAD panels).  I have skylines going in at the first reflection, 3.2cm elements with max length of 42cm so 400Hz to over 5kHz.  When that's all done I'll decide on these membranes.

 

The trouble with any of these solutions is they're usually one offs for your own application and then you need ro build a lot to measure a real difference and work out if it's doing what you want.

18 hours ago, almikel said:

Gyprock does act as a membrane trap, and absorbs energy through flexing a bit, and lets most of the low bass right through

Hi Mike 

Yea correct, the walls, ceiling and floor  do act as a membrane trap fundamentally.

Ceiling and floor aside for a moment. Vertical propagation of LF up through the roof is not a huge problem neither is through the floor for the neighbours 🙂. 

Single plaster wall, not insulated, no sarking hardwood weatherboard,

 

They let through (without much hinderance) the walls into nature from 35Hz and down roughly measured outside.  Up the frequency from there the SPL is reflected back into the room, The problem occurs at this frequency transition for the listener as the flexing walls create a "bubble of reverberation in the listening zone" if you will at the 35Hz ish up to around 80Hz. At this 80 Hz the wall stops moving and act as a mirror to sound, at this frequency reflected back into the listening area.

Not ideal, bloating (room imposition) the bass response. Yea it's not the worst to listen to bass is fairly clean up to 30Hz, unlike a solid rendered wall, however the Neighbours can and do complain and I agree with them.

One neighbour 2 doors down (used to have a problem) has a particular cupboard that he could hear bass notes emanating from.......pot lids. 🙂

 

The double plaster wall and heavy outer cladding, insulated to R2.5 with heavy bats and foil foam board as the thermal break. DG thermally broken aluminium windows, metal angle sealing the wall floor/corner/ceiling intersection.

Outcomes here realised at least a 20 dB decrease of SPL getting out into nature. however the frequency range of the "leaky walls" was only lowered not stopped. At this point the walls do still leak from 20Hz and down but at -20dB. You could have a party now and no one would be the wiser as outside is now peaceful with only a little very LF almost sneaks out.

This nice new reasonably sound proof room comes with a caveat to the Audiophile, now the reflected bass transition is around 20Hz, the walls start moving and de articulates SQ with reverberation evident from 20Hz.  Good to meh. the SQ. That and a really terrible clap test, similar to that of a large room sized cement water tank.

18 hours ago, almikel said:

Rattles are a totally different issue - very evil and hard to track down

Indeed there were a few internal timbers I (Builders) call rattlers. Trust me when I say every mm of the build was in keeping with a resonant rattle free listening zone, to at least 105dB at 20Hz,

 

The partly glass external back door does start to vibrate quite violently beyond this. The 25w power amp is the awe inspiring beast at this point, the 4 x21's excursion is about 1mm power amp tapped out.

 

Yea, this is how the whole thing is run, Sadly I had a loss of a set of large A/B Power amps to poor service and back up by Manufacture, had to scrap the whole lot. Haven't really recovered my amp rack since, so started small is all I could afford. The little amps bring a World of discovery, they sound,,,,,,well quite ok, I cannot hate them (would probably like to)  due to their rather tidy performance and their ability at "tapped out" is TBH, ok. Particularly at 10Hz, crazy I know, $50 well spent yea. Oh, $100 now the little 12v Wondon 30 x 2 sitting there is to be brought into the mix.

 

I'm an efficiency lover and proven you can get beast mode 0% linear distortion ULF from the smallest low powered amplifiers. Obviously as @davewantsmoore suggests, you need 670litre refrigerator sized enclosures and be brave enough to mount 2 drivers and tune to a target, then build 2 of the things. THen be even braver and drag them into a lounge.

17 hours ago, DVDHack said:

In my experience it's unevenness that's hard to treat more than a long Rt60.

 

Not to take away from anything @almikel  has posted, quite correct as detailed  above in this post,

The soundproofed timber home lounge is a complete PITA to treat, 20 to 80Hz. This bubble of reverb, seen in the graphs, has been the target of the 3 large membrane traps and you are spot on here.

 

TBC.......Couple more posts to address

 

Edited August 27, 20232 yr by playdough

10 hours ago, DVDHack said:

just absorption

You won't be able to affect the frequencies being talked about in this thread (<<<80Hz).

 

10 hours ago, DVDHack said:

both my rooms are a good size

This helps.

 

10 hours ago, DVDHack said:

I sit at the 38% mark in the room

You mean 38% of the length dimensions, back from the front wall (ie. close-ish to the front).   This is good.

It's one of the biggest mistakes IMVHO (too far back) ... but often unavoidable.

 

10 hours ago, DVDHack said:

one offs for your own application and then you need ro build a lot to measure a real difference and work out if it's doing what you want.

Yep.  You can get professionals to do it for you... but that is super spendy.

58 minutes ago, davewantsmoore said:

You won't be able to affect the frequencies being talked about in this thread (<<<80Hz).

Sure you can, here's the prediction...  In blue.  It's not a maximum absorption but I don't have massive issues.  My main problem is around 70Hz.

 

 

58 minutes ago, davewantsmoore said:

You mean 38% of the length dimensions

Yep, just dumb arse lucky where I already had the couch, the kitchen and dining area are behind me.  Since I'm not best at keeping the kitchen cabinets empty of crap, it's probably not bad diffusion either, certainly random...  This room isn't real important, it's casual listening that's just worked out.  JBLs sound great in here.

 

1 hour ago, davewantsmoore said:

You can get professionals to do it for you...

Yeah....Nah....  Maybe one day for the other room if I run into issues but not yet.

 

 

1 hour ago, davewantsmoore said:

You won't be able to affect the frequencies being talked about in this thread (<<<80Hz).

Quite correct. you could have a sea of absorb, I'm talking 60m of good quality of Polymax that rates well, rolls and rolls at transition corners, centre walls across the cieling, and not get any change of reveb. in sub 80Hz, nada and measure it true.

 

Will do no more than dry out and kill dead the live quality of a lightly treated for  HF  lounge, with a very high co efficient down to 80 HZ. 

 

I feel we can all agree on this 

 

12 hours ago, DVDHack said:

 The largest room needed very little treatment to achieve excellent sound quality, Im delighted with how it's turned out and quite by dumb luck

This is also true, as the first reflection points of a large room are an order of magnitude further away. 2700mm high, 12m x 5m is it ? Well furnished, couch, single arm chairs, land so on with large windows.  QRD diffusers would probably do

Just looking at this above waterfall, yea. Kindly supplied with thanks, the room would sound way better than mine for sub 80Hz, really quite low "bloat" there. 

With what I've learn't with work and measurements. the above Waterfall graph reverb, could be "flattened" with high co efficient absorb above 1KHz. A few 60mm ceiling panels, and QRD arrays at first reflection point ?

 

To get treatment into the sub 80Hz in a large (if required at all) area I would be deploying either a 200mm + thickness absorb with a tuned face plate, say 40Hz, there is a calc. online or maybe a membrane trap, locally with each sub position.

But that's only my opinion 🙂 for what it's worth 

The messy kitchen, well I'm still without a kitchen really, but it's clean and tidy, maybe it shouldn/t be if it adds to the acoustic flavour of a dual purpose living area.. 

 

And yea, if the little 3 way JBL speaker is any thing close to it's Theatre Pro, 4732T, 3 way 115dB efficient horn/bass cab combo, they would be reasonable sounding thing with very large domestic rated  sub support. I do love JBL Speakers, big ones.

 

Edited August 28, 20232 yr by playdough

The room is 12.8 x 6.5 x 3.1m, the primary modal frequencies are a very low.  I expect that the fact that one long wall is basically a window wall, the bass energy probably disappears through that.

 

I need to remeasure the response now, I've added a cloud at the first reflection area that's 4 lots of 600 x 1800mm.  I'm currently framing the corner absorption since it was just propped there to test, when done I'll remeasure. 
 

Got fire prep to do on the farm so it's a fill in job.

6 minutes ago, DVDHack said:

12.8 x 6.5 x 3.1m

Nearly as big as this house. 🙂

7 minutes ago, playdough said:

Nearly as big as this house. 🙂

The benefit of abandoning civilisation for farm life.

15 minutes ago, playdough said:

the above Waterfall graph reverb, could be "flattened" with high co efficient absorb above 1KHz.

Is this a SPL calibrated chart?   If it is, then we're already at the room noise floor above 1khz.

 

21 minutes ago, playdough said:

Just looking at this above waterfall, yea. Kindly supplied with thanks, the room would sound way better than mine for sub 80Hz, really quite low "bloat" there. 

Not 100% sure what you mean by bloat (as in what that means for the chart)

 

.... but looking at your "July 31" data (which I'm not really sure if is treated or not - I think not, but) .... yours is about the same, if not marginally better.

41 minutes ago, DVDHack said:

In blue.

"An effective absorber will have an AC of > 0.75"

It will do something... but I think it's easy to over estimate the results.

 

41 minutes ago, DVDHack said:

Yeah....Nah....  Maybe one day for the other room if I run into issues but not yet.

DIY is the way.   😄

A

Above 80Hz in this graph, Polymax  trap 120mm cores only on wall and 40mm on ceiling doing a job, obviously a smooth reverb time all the way to measurable HF and quite flat, so acts "similarly" through that frequency range. 

 

Here is where it get's harder and harder to measure as only half of the entire area is actually treated. 

The Postie dropped of some rolls of filament for the Printer, so the Chiwawah is barking at the back door and I can still hear the ping echo from every little bark, bark, from that untreated space only 3m away

This is getting harder 

In the green 40ms zone, I can hear the reberb, it sounds like a bloated one note to a degree,  to the inexperienced they might be impressed with the room flex, but not I

There is some of that in the @DVDHack measurement but IMHO not as much as mine.

Latest measurements to come.

 

Edited August 28, 20232 yr by playdough

2 minutes ago, davewantsmoore said:

It will do something... but I think it's easy to over estimate the results.

Very true but my problems are not huge.  I'm also guessing that the chances of me accurately hitting the exact frequencies I need with limp mass traps is pretty low and with the narrow bandwidth I doubt I'd be better off.  I wouldn't actually know if I just need more panels or if my frequency tuning is off, unless it badly affects something else.  There's the real issue, you could easily suck out adjacent frequencies and cause peaks followed by massive dips...  tuning would be a nightmare.  I did some modelling of different absorption in the limp panels etc to try to generate a smoother broader response but I think it would be quite the challenge to construct and then change.

 

My other room is smaller but dedicated (7.5 x 5.4 x 3.1m) and I don't sit in the ideal spot so I will do more work in there.  It's carpeted and has heavy curtains, both are a real pain to deal with...

3 minutes ago, DVDHack said:

exact frequencies I need with limp mass traps is pretty low and with the narrow bandwidth I doubt I'd be better off

That is conjecture hahaha educated guessing, which is ok, let off

 

That aside, did you read my prognosis and criteria I set out for treatment of your lounge ?

 

Please kindly supply more measurements as you come to see treatment work really done in that dance hall you have there. 

53 minutes ago, playdough said:

Just looking at this above waterfall, yea. Kindly supplied with thanks, the room would sound way better than mine for sub 80Hz, really quite low "bloat" there. 

With what I've learn't with work and measurements. the above Waterfall graph reverb, could be "flattened" with high co efficient absorb above 1KHz. A few 60mm ceiling panels, and QRD arrays at first reflection point ?

 

To get treatment into the sub 80Hz in a large (if required at all) area I would be deploying either a 200mm + thickness absorb with a tuned face plate, say 40Hz, there is a calc. online or maybe a membrane trap, locally with each sub position.

But that's only my opinion 🙂 for what it's worth 

The messy kitchen, well I'm still without a kitchen really, but it's clean and tidy, maybe it shouldn/t be if it adds to the acoustic flavour of a dual purpose living area.. 

 

17 minutes ago, DVDHack said:

There's the real issue, you could easily suck out adjacent frequencies and cause peaks followed by massive dips

This will definitely not happen. You will find this out soon enough, the large room treatments as described "simply put, don't in any way equate to that"

Actually I struggle to think how that would apply ? Help wit this statement from actual work or measurements please.

 

As suggested, I've done a little in this field,  maybe more than I let on, in Churches as an example.

1 hour ago, DVDHack said:

 

Well, maybe if you do this, which I wouldn't unless there is a specific thing you actually want out of the scope of a flat reverb time

What was the thickness of such tuned modrl panel ?  it's cut the number off the bottom of the drawing.

43 minutes ago, playdough said:

Above 80Hz in this graph, Polymax  trap 120mm cores only on wall and 40mm on ceiling doing a job, obviously a smooth reverb time all the way to measurable HF and quite flat, so acts "similarly" through that frequency range. 

This chart is cut off at least 20dB higher than the other chart.

Show this chart again, but with the same settings (SPL down to ~zero, and t=600ms)

16 hours ago, DVDHack said:

is the equation above wrong then?  Seems to me measuring the mass and the depth isn't particularly difficult.

Not wrong, it'a a guide stuck to 600 x 900. going 2400 x 1300 x 3 in a medium lounge  that;s outside the scope of this equation, we have consensus on this ?  

5 minutes ago, davewantsmoore said:

This chart is cut off at least 20dB higher than the other chart.

Show this chart again, but with the same settings (SPL down to ~zero, and t=600ms)

Just an idea, get the ruler off the desktop you are sitting at and slap it on the 300ms line on the DVDhack graph.

I am hoping that those looking at this thread can actually read a waterfall graph, er properly sort of.

😁

 

1 hour ago, DVDHack said:

It's carpeted and has heavy curtains, both are a real pain to deal with.

Please expand your prognosis of the actual PITA you experience here ? TBH actually need to know, it's a non statement no one will fathom, really without ezplanation. 

Quick measurement would be helpful, ah and 300ms depth of field in graph pls.

Respectfully

Edited August 28, 20232 yr by playdough

19 hours ago, almikel said:

The Toole/Olive perspective is not to damp/alter 1st lateral sidewall reflections so long as your speakers have a smooth "off-axis" response, such that the 1st lateral reflection has the same spectral content/frequency response as the direct sound....

Hi Mike, this post got me thinking, thanks 🙂 you must have a photographic memory to pull "perspectives" from these manuals, yea.

 

About not worrying about reflection or first harmonic away from the fundamental, with a known "good wide dispersion speaker set"

 

I can understand how important it is although not completely. About the only speaker I've heard that actually behaves reasonably  like this is a di pole open or curvilinear electrostatic type speakers, even ribbons for HF.

 

Does this actually contradict time alignment and impulse time correction theory a little ? or is it describing in a round about way keeping a lively character about the space the speakers house.

 

Keep the "over active Acoustic Engineering  zealot" product spend down, use furniture and wall shelving, carpet...   just a suggestion 😅

 

Perspective is a wonderful thing.   Was this The Toole/Olive perspective written before the advent of DSP convolution and impulse TD employment ? Will look it up.

Link ?

 

 

Edited August 28, 20232 yr by playdough