Jump to content

Recommended Posts

I have no idea yet where to take this, or where I will end up. I am going to end up with a good room either done by myself or done by an professional.

 

At the moment I have started taking measurement with REW, which is confusing and satisfying at the same time. It is confusing as I haven't made much progress in taming the real problems but satisfying as I do discover things that I would not have picked up by ear, even knowing they possibly exist.

 

To name a a few things that I discovered in the impulse graph, is that Martin Logan's have a very controlled mid-high frequency dispersion pattern with no early reflections on side walls, ceilings or floor. That the back wall early reflection point is producing the most early reflections, simply due to the fact I am sitting closer to this early reflection point than any other inside the room. In my case it also reflects the first front wall early reflection point, and di-pole wave early reflection point. Another eye opener is that opening the door in the back of the room is also eliminating a peak in the impulse graph. Confusing as I don't know yet why this is happening nearly 5ms after the first back wall early reflection point.

 

Another thing that I discovered what kind of impact a window can have on the speaker graph. I have a window in the right wall of the room and not in the left and the right subwoofer and main speaker measure different in a specific region, which seem to be related to room nodes.

 

Both interesting discoveries for a newby, but hardly useful. I rather avoid damping the early reflection points as they make the sound more lively. Another thing is that my Martin Logan's aren't very energetic in the HF. So damping the room isn't going to improve this, even when I might need to take a look at this, as the T30 time  is above 0.5. Confused again! How am I going to lower the reflection decay time without killing all the HF.

 

One thing is very clear,  that my room needs a lot off Bass management. The thing that isn't completely clear to me is that if EQ-ing an SPL graph fall's in the same category as acoustics? a SPL graph is only a single point in the room, but room nodes exist through out the room. But I have tweaked the SPL graph into a flatter response, and room node peaks are contained and I can no longer hear them. But acoustic treatment is also handling decay time of reflections which is a different aspect than an SPL graph. Argh, confused again!

 

Now after reading into what types of bass traps are available, things get difficult. As broadband absorbers are the first go to, but what if you don't want to dampen the room so much? 3 out of the 4 corners of my room aren't suitable for these type, as the front 2 corners are "needed" to keep my speakers "alive", and 1 corner in the back of the room has a door opening. A bulkhead trap all around the room would be a better option.

Membrane traps would be the alternative option, but these can be hard to build.

Then there is the anti mode DSP, which is basically a real live anti wave producer which requires an additional sub. But this comes down to a type of EQ again.

 

Slowly making my way, but creating more confusion than progress at the time.

 

 

867153d44783562197d0ae7cad775975.jpg21407b94fd478fe205a3dde91b316019.jpg73e809a665877550f31c22fa8f49d68b.jpg

To end with a few first questions.

Can EQ be considered acoustics?

Can you lower decay times using diffusion?

Can you lower decay times by using EQ?

Are there broadband bass traps that don't trap mid or high frequency?

Can room nodes being EQ, or do you need traps?

Share this post


Link to post
Share on other sites

Hi PK,

getting a measurement rig is one thing - as you've worked out, properly understanding the results is another...

I think your learning curve would accelerate if you found the right professional who could measure your room, recommend treatments and explain why those treatments will work and you track the changes they make to your measurements.

Applying acoustic treatment successfully tends to be an iterative process..

22 hours ago, Primare Knob said:

Can EQ be considered acoustics?

EQ changes the sound, so yes I consider EQ as part of room acoustics

22 hours ago, Primare Knob said:

Can you lower decay times using diffusion?

depends on the diffusion - QRDs (for example) won't change decay times, but 1D and 2D BAD panels diffuse using absorption and reflection, so they will tend to lower decay times

 

22 hours ago, Primare Knob said:

Can you lower decay times by using EQ?

Yes - with caveats

If you identify a room mode that creates a peak in frequency response that has a long tail in the Cumulative Spectral Decay (CSD) graph, then implementing an EQ cut of that peak will remove energy of the peak and lower the decay time at that position, and any other room position that had the same peak. This may make things worse elsewhere in the room - but generally I've found using EQ to tame peaks (ie EQ cut) to be quite effective below 150Hz or so, and especially effective below 100Hz where absorption treatment simply gets too large.

22 hours ago, Primare Knob said:

Are there broadband bass traps that don't trap mid or high frequency?

Yes - the easiest approach is to cover the absorption with a membrane (eg builders plastic) that reflects the higher frequencies, but lets the bass through - the membrane can actually improve bass performance.

Another approach is to cover parts of the absorption (as suggested by @Peter the Greek ) in simple strips of masking tape to reflect some higher frequencies, or go a bit further and apply the masking tape or say wooden slats in a 1D BAD panel sequence generating some diffusion at the same time as keeping higher frequencies inside the room.

I've seen 2D BAD diffusion masks available made from perforated metal to go over absorption also.

 

22 hours ago, Primare Knob said:

Can room nodes being EQ, or do you need traps?

Yes  room modes can be EQ'd, but best to target peaks, not troughs with EQ, and the same caveat applies as above. EQ is position dependent  - you can make things worse elsewhere in the room.

 

cheers

Mike

 

 

Edited by almikel
typo

Share this post


Link to post
Share on other sites

I'd be filling that ceiling with rock wool and covering in slats as a starting point....

Considered carpet?

Cover the back wall in absorbers. With something like a BAD 300mm around all 4 sides of the surrounds.

If the ceiling trap doesn't sort out the bass, I'd build a riser trap

Share this post


Link to post
Share on other sites

Hi PK,

6 hours ago, Primare Knob said:

 3 out of the 4 corners of my room aren't suitable for these type, as the front 2 corners are "needed" to keep my speakers "alive", and 1 corner in the back of the room has a door opening.

I wouldn't regard the 2 front corners as "off limits" for absorption - many owners of open baffle speakers damp the back wave, and you'll still have plenty of treble spraying around if you used the 3 vertical wall/wall corners available for absorption traps targeted at lower frequencies (ie floor to ceiling straddling the corners, as wide and deep as you can get away with - say 600mm wide and 200mm deep)

 

6 hours ago, Primare Knob said:

 A bulkhead trap all around the room would be a better option.

and expensive - but you're thinking on the right track - there are 20 corners in a rectangular room to consider for treatment - floor/wall corners are just as good for bass traps if you can yield the space - even just to experiment.

Normal fluffy poly batts will freestand on their long edge - but they need to straddle the corner to get an air gap to work lower.

 

6 hours ago, Primare Knob said:

Membrane traps would be the alternative option, but these can be hard to build.

This is a bit left field, but with your exposed rafters, you could turn your whole ceiling into a massive membrane bass trap.

Assuming you were prepared to lose that height, attach vinyl flooring (lino) across the entire ceiling with fluffy above for a huge limp mass membrane  trap...bass management likely done.

 

cheers,

Mike

 

Share this post


Link to post
Share on other sites
22 minutes ago, Peter the Greek said:

I'd be filling that ceiling with rock wool and covering in slats as a starting point....

 

7 minutes ago, almikel said:

This is a bit left field, but with your exposed rafters, you could turn your whole ceiling into a massive membrane bass trap.

Assuming you were prepared to lose that height, attach vinyl flooring (lino) across the entire ceiling with fluffy above for a huge limp mass membrane  trap...bass management likely done.

Lol - not so left field - PtG's suggestion would also work well.

 

Mike

Share this post


Link to post
Share on other sites
57 minutes ago, Peter the Greek said:

I'd be filling that ceiling with rock wool and covering in slats as a starting point....

The above would help lots...

But IMHO, any time you deploy slats, I would go that extra step and deploy them in a 1D BAD panel sequence - a bit more work, and on a ceiling you may need something to support the absorption across the gaps (eg fishing line), but you get diffusion, not just scattering, which is worthwhile (again just IMO).

 

Mike

Edited by almikel

Share this post


Link to post
Share on other sites


On 1/12/2018 at 10:21 PM, Peter the Greek said:

I'd be filling that ceiling with rock wool and covering in slats as a starting point....

Considered carpet?

Cover the back wall in absorbers. With something like a BAD 300mm around all 4 sides of the surrounds.

If the ceiling trap doesn't sort out the bass, I'd build a riser trap

Thanks Peter,

 

What are slats? BAD, are these the same kind of panels as @almikel it talking about?

I do like the riser idea. I could potential build a riser on top of the floor at the front of the room. Max 25cm high, max 337cm wide, min 85cm deep or deeper with a cutout for the front speakers.

What is the basic principle for the workings of the riser, as it seems to be a combination of an absorption and helmholz trap.

Share this post


Link to post
Share on other sites
On 1/12/2018 at 10:36 PM, almikel said:

Hi PK,

I wouldn't regard the 2 front corners as "off limits" for absorption - many owners of open baffle speakers damp the back wave, and you'll still have plenty of treble spraying around if you used the 3 vertical wall/wall corners available for absorption traps targeted at lower frequencies (ie floor to ceiling straddling the corners, as wide and deep as you can get away with - say 600mm wide and 200mm deep)

 

and expensive - but you're thinking on the right track - there are 20 corners in a rectangular room to consider for treatment - floor/wall corners are just as good for bass traps if you can yield the space - even just to experiment.

Normal fluffy poly batts will freestand on their long edge - but they need to straddle the corner to get an air gap to work lower.

 

This is a bit left field, but with your exposed rafters, you could turn your whole ceiling into a massive membrane bass trap.

Assuming you were prepared to lose that height, attach vinyl flooring (lino) across the entire ceiling with fluffy above for a huge limp mass membrane  trap...bass management likely done.

 

cheers,

Mike

 

Thanks Mike,

 

I have tested with absorbing the the early reflection points and back wave reflection, and it would not be my preferred option, as it makes it sound rather uninteresting. I would prefer to dampen decay times while keeping the early and back wave reflections "alive". I haven't tested this with diffusion, or a combination of absorption and reflection as I do not have this option at this time.

 

Not ruling it out, but I prefer to keep the ceiling as much as it is. As covering it, will lower it an internal ceiling height of 220cm.

Edited by Primare Knob

Share this post


Link to post
Share on other sites
On 1/12/2018 at 11:11 PM, almikel said:

The above would help lots...

But IMHO, any time you deploy slats, I would go that extra step and deploy them in a 1D BAD panel sequence - a bit more work, and on a ceiling you may need something to support the absorption across the gaps (eg fishing line), but you get diffusion, not just scattering, which is worthwhile (again just IMO).

 

Mike

Could you show me a picture of these BAD panel sequence? When I google it, I find these panels with a specific pattern of holes.

Share this post


Link to post
Share on other sites

Here are some graphs of my room node problems.

 

I would like to setup the subs for LFE movies, and my main speakers for full range Music to keep things simple. The subwoofer graph is made with an xover setting of 80Hz in the PrePro. The speakers graph is made with the speakers set to large, ignoring the xover setting in the PrePro

 

Do Bass traps also help in reducing the dips in the response?

 

Measurements are made with a -20dBu setting at 85dB at the LP

I can adjust the LF gain (x - 100Hz) for my front speakers to +10, which does raise the dip between 50Hz-65Hz to around 80-85dB.

I can adjust the gain of the subwoofers as well as their output level is +/- at 25%

The difference between L-R or A-B, in the 50Hz-65Hz has to do with the large window sitting halfway the right wall.

RoomNodes_01.jpg

RoomNodes_02.jpg

LF_Speaker_L_R_Adjustment_Range.jpg

Share this post


Link to post
Share on other sites
2 hours ago, Primare Knob said:

Thanks Peter,

 

What are slats? BAD, are these the same kind of panels as @almikel it talking about?

I do like the riser idea. I could potential build a riser on top of the floor at the front of the room. Max 25cm high, max 337cm wide, min 85cm deep or deeper with a cutout for the front speakers.

What is the basic principle for the workings of the riser, as it seems to be a combination of an absorption and helmholz trap.

Howdy,

Here is what I'm talking about. To make that diffusive, you'd need to vary the slat size and gap size. I dont know if I'd bother, but I suppose if you're going to the effort. Here is a good example:

 

image.png.0eea601021abb10e9f658fd4bb314659.png

 

BAD's look like this:

image.png.7887368a7dc5fc9b161aa954996d43fe.png

 

For around the surrounds, I'd use Quest AI's Q-Perf product, its better for this type of thing compared to RPG's product. Acoustic Vision sell both.

 

You don't want a speaker of any kind (LCR or sub) sitting on a riser. If you want to do that, build a "stage" (big braced ply box filled with sand)....this will help with damping....apparently. I've always used them so I cant comment on its effectiveness....much more smarter brains who came up with this stuff swear by it. I'm not sure the space you outline would be large enough. I did one as a bulkhead in our last place that was the width of the room, 1200 deep and 300 high. You can see the bones of it here (that black box at the top is an AC supply vent):

 

image.png.b0845e22200462ebcdaade223067dc0e.png

 

If you build a riser at the back, then you want to build it per this article:

image.png.dd837430fd8621afea6ad18d6d9f65ea.png

image.png.a02e2fe7cc0cd8347485cc86262a58c3.png

image.png.48833ad1ec4be20fa250b7508507fa9b.png

 

image.png.6b2fa75d414944c1e320377de29b8168.png

 

Share this post


Link to post
Share on other sites
2 hours ago, Primare Knob said:

 As covering it, will lower it an internal ceiling height of 220cm.

IMHO, so long as you're not 225cm tall, this isn't a problem....so long as you can walk around I wouldn't worry about it. Its a very good, useful space for fixing your problems....cheap too....I'd use it

Share this post


Link to post
Share on other sites


1 hour ago, Primare Knob said:

Thanks Peter,

 

What are slats? BAD, are these the same kind of panels as @almikel it talking about?

 

Slats are (usually) timber strips with gaps in between and absorption behind. The hard surfaces reflect energy helping to stop the room getting too dead.

You get scattering if the pattern (gap and slat) is regular. If the gap/slat pattern is random you get diffusion - this is a 1D Binary Amplitude Diffuser (BAD) panel - invented by the gurus of diffusion - Cox and D'Antonio.

 

I've never found good sources on where diffusion starts/stops with 1D BAD panels.

They don't generate as much diffusion as say QRDs, but because they don't, their sitting distance restrictions aren't as strict as with QRDs.

I tried to pull a little bit of information together in this thread - not necessarily all technically correct

The BAD sequence needs to be random to generate diffusion.

Flipping a coin works, head=slat, tail=gap, or use a random sequence like this one

https://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/395773-diy-binary-amplitude-diffuser-anyone.html

 

1D BAD as slats on a wall

5a5ac5cbae2ab_1DBAD.jpg.09a650a853d491b43074fc0e1d41082d.jpg

 

2D BAD panel

5a5ac62f460bd_2DBAD.png.4a11e828431d28719cdbe651c2d823b4.png

 

cheers

Mike

 

 

Share this post


Link to post
Share on other sites
IMHO, so long as you're not 225cm tall, this isn't a problem....so long as you can walk around I wouldn't worry about it. Its a very good, useful space for fixing your problems....cheap too....I'd use it
What kind of effect can one expect from such a ceiling trap? The 1/4 wavelength rule suggest it is not going to be very effective below 200Hz.

Share this post


Link to post
Share on other sites
Slats are (usually) timber strips with gaps in between and absorption behind. The hard surfaces reflect energy helping to stop the room getting too dead.
You get scattering if the pattern (gap and slat) is regular. If the gap/slat pattern is random you get diffusion - this is a 1D Binary Amplitude Diffuser (BAD) panel - invented by the gurus of diffusion - Cox and D'Antonio.
 
I've never found good sources on where diffusion starts/stops with 1D BAD panels.
They don't generate as much diffusion as say QRDs, but because they don't, their sitting distance restrictions aren't as strict as with QRDs.
I tried to pull a little bit of information together in this thread - not necessarily all technically correct
[/url] The BAD sequence needs to be random to generate diffusion.
Flipping a coin works, head=slat, tail=gap, or use a random sequence like this one
https://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/395773-diy-binary-amplitude-diffuser-anyone.html
 
1D BAD as slats on a wall
5a5ac5cbae2ab_1DBAD.jpg.09a650a853d491b43074fc0e1d41082d.jpg
 
2D BAD panel
5a5ac62f460bd_2DBAD.png.4a11e828431d28719cdbe651c2d823b4.png
 
cheers
Mike
 
 
I honestly like the look of those 2D panels.
The 1D version could potentially be used for the ceiling trap.

Is there a pattern behind the chaos?

Share this post


Link to post
Share on other sites

I had a plan for a BAD grating in copper sheet in an RPG waveform....then we moved....

Playing around with the slotted scenario....without giving it too much thought, its decent....and consider the size of the thing

image.thumb.png.2a0e8e3716b6b8f7fb99eb865e5b8740.png

Share this post


Link to post
Share on other sites
1 hour ago, Primare Knob said:

yes they look very cool - if you could source the perforated masks, the rest would be very  easy to DIY.

Making the mask yourself is a lot more work - drilling all those holes - even if you just copy the mask, blow it up on a printer and use it as a template.

 

1 hour ago, Primare Knob said:

 

1 hour ago, Primare Knob said:
4 hours ago, Peter the Greek said:
IMHO, so long as you're not 225cm tall, this isn't a problem....so long as you can walk around I wouldn't worry about it. Its a very good, useful space for fixing your problems....cheap too....I'd use it

What kind of effect can one expect from such a ceiling trap? The 1/4 wavelength rule suggest it is not going to be very effective below 200Hz.

PtG's idea still has merit.

Don't take "too" much notice of the 1/4 wavelength criteria (it's certainly not a "rule"). 1/4 wavelength is just where air velocity is maximum - trapping still occurs wherever the velocity is >0.

Bass traps are also about size, and the models ( eg this one  http://www.acousticmodelling.com/porous.php  ) only cater for depth and air gap. Another member here discussed the "grazing" benefit of large traps, that the models don't show, resulting in the measured performance of a room with this sort of trap being better in the low end than the models predict. If you did cover the ceiling in slats with absorption above, I'd be confident the performance of the absorption would work much lower than 200Hz.

 

As I suggested above, an alternative to the slats/absorption approach on the ceiling would be a "limp mass" membrane trap (or multiple limp mass traps so the whole ceiling wasn't covered). IMO this would achieve better low frequency performance, but not as good broadband performance as slats/absorption.

 

I'll have to go searching, but @svenr posted a thread for low cost treatment, and a component of that treatment was a limp mass membrane trap across a large part of the ceiling - my recollection is that he didn't require any additional "bass" traps beyond the ceiling limp mass trap for modal control.

Svenr used ordinary flooring vinyl as the "membrane" with fluffy above, but "Mass Loaded Vinyl" (MLV) is a more typical product used - and can be sourced from the same insulation providers that sell Ultratel etc (but MLV is much more expensive than flooring vinyl).

A good thread that includes design parameters for limp mass traps here:

https://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/743040-tims-limp-mass-bass-absorbers.html

 

In your case you could just consider the depth parameter set at the depth of your rafters - and ignore Tim's advice about size - use the channels between your rafters and make them as long as you choose, but leave some ceiling space free since you're worried about losing the ceiling height . The cavity behind the limp mass needs to be sealed for them to work though - you'd need "noggings" at each end of every trap.

 

3 hours ago, Primare Knob said:

well it's meant to be random, hence why flipping a coin works for a 1D BAD slat pattern.

You "could" create a 2D BAD sequence just by laying another layer of slats over the top of the 1D slats at 90 degrees.

This will then diffuse in 2 planes (hence their name 1D and 2D - similar to QRD diffusers - a 1D QRD looks like a cutlery drawer with different depths in each longitudinal "slot", and only diffuses in 1 plane. A 2D QRD "Skyline" diffuser looks like buildings (skyscrapers) all at different heights - these diffuse in 2 directions.

 

@hochopeper did the maths to generate an "original" 2D BAD sequence based on Cox and D'Antonio's work.

RPG (Cox and D'Antonio) introduce symmetry in their 2D pattern for looks, but still maintain sufficient "randomness" for diffusion.

 

8 hours ago, Primare Knob said:

Do Bass traps also help in reducing the dips in the response?

Yes they do - peaks and troughs exist based on the room response and sound waves bouncing off boundaries and combining - where the waves are in phase, they add, when they're out of phase, they cancel (drop a pebble into a fish tank and watch how the ripples bounce of  the boundaries and re-combine after a few seconds).

Pull energy out (via  traps) and peaks and troughs are reduced.

 

cheers

Mike

 

Share this post


Link to post
Share on other sites


On 1/14/2018 at 6:55 PM, Peter the Greek said:

I had a plan for a BAD grating in copper sheet in an RPG waveform....then we moved....

Playing around with the slotted scenario....without giving it too much thought, its decent....and consider the size of the thing

image.thumb.png.2a0e8e3716b6b8f7fb99eb865e5b8740.png

Hi PtG,

I've never mucked with the multi layer aspect of this tool - even has limp mass - thanks heaps!

What absorber type were you using in the example above? 27000 is very high - must be 96kg/m3 or something?

 

What I found interesting when I plugged some numbers in is that the slats improve the bass performance over no slats, rather than just reflecting higher frequencies - prob not surprising when I think about it, as the solid (slat) part would operate as a membrane once you got enough coverage say >50%  (ie more slats than gaps).

 

Good to know the multi layer capability is there - hours of tinkering - thanks again.

 

cheers

Mike

Edited by almikel
typo

Share this post


Link to post
Share on other sites

@almikel

 

Howdy Mike - 27000 is about right for rockwool, so yes, super high density. If it were my room, I'd be doing it for sure, but I reckon instead of plain slats, if I could make the performance work, I'd used these things (easy to DIY with a router table):

 

image.png.00e90f2bf00028ed83c6fe1fe8f0afc1.png

Share this post


Link to post
Share on other sites

loads of fun mucking with the multi-layer part of the calculator  http://www.acousticmodelling.com/multi.php    modelling some limp mass traps.

based on a previous post by  @svenr  I just used his figure of 1.8kg/m2 for the mass of ordinary flooring vinyl (if building a trap you'd obviously want to check this). 

I couldn't find Svenr's build thread, but he mentioned his vinyl membrane trap in another thread here (scroll down a few posts for simulation graphs of the limp mass traps):

Here's the model of the bass performance for a 200mm deep (estimation of your rafters) limp mass trap using 1 and 2 layers of flooring vinyl with 200mm of fluffy above (fluffy Gas Flow Resistivity estimated at 5000 thingies)

5a5c6f70d9912_limpmassvinylflooring1and2layers.JPG.cb053b603382dc4f5a85eeb9eea5d51d.JPG

As with any pressure trap they are quite "narrowband".

If you want to experiment with different parameters, once you hit "Calculate" it takes you to the "Results" tab, just hit the "Calculator" tab to re-enter different parameters (hitting the back button means you need to enter everything again).

 

Using expensive Polymax XHD for the damping above the vinyl in this scenario reduces performance. Another tick for Svenr.

 

You could place several of these on your ceiling with a mix of 1 layer and 2 layers of vinyl and achieve good "bass" trapping - possibly enough not to need additional corner traps.

 

I have the same ceiling as you do - just lower :( - if I stand on my toes my head brushes the bottom of my rafters (no pogo dancing for me in my room!).

The cost of Mass Loaded Vinyl (MLV) has always put me off, but I might try some of these in the parts of the room I don't stand using off cuts of flooring vinyl and a bag of poly fluffy.

 

Hats off (again) to @svenr for showing ways of using "non acoustic" products for room treatment.

 

Mike

Edited by almikel

Share this post


Link to post
Share on other sites
43 minutes ago, Peter the Greek said:

@almikel

 

Howdy Mike - 27000 is about right for rockwool, so yes, super high density. If it were my room, I'd be doing it for sure, but I reckon instead of plain slats, if I could make the performance work, I'd used these things (easy to DIY with a router table):

 

image.png.00e90f2bf00028ed83c6fe1fe8f0afc1.png

Now those as slats would be way cool

Share this post


Link to post
Share on other sites
Now those as slats would be way cool
It would be a good reason for buying another tool.

Share this post


Link to post
Share on other sites
loads of fun mucking with the multi-layer part of the calculator  [mention=123017]svenr[/mention]  I just used his figure of 1.8kg/m2 for the mass of ordinary flooring vinyl (if building a trap you'd obviously want to check this). 
I couldn't find Svenr's build thread, but he mentioned his vinyl membrane trap in another thread here (scroll down a few posts for simulation graphs of the limp mass traps):
Here's the model of the bass performance for a 200mm deep (estimation of your rafters) limp mass trap using 1 and 2 layers of flooring vinyl with 200mm of fluffy above (fluffy Gas Flow Resistivity estimated at 5000 thingies)
5a5c6f70d9912_limpmassvinylflooring1and2layers.JPG.cb053b603382dc4f5a85eeb9eea5d51d.JPG
As with any pressure trap they are quite "narrowband".
If you want to experiment with different parameters, once you hit "Calculate" it takes you to the "Results" tab, just hit the "Calculator" tab to re-enter different parameters (hitting the back button means you need to enter everything again).
 
Using expensive Polymax XHD for the damping above the vinyl in this scenario reduces performance. Another tick for Svenr.
 
You could place several of these on your ceiling with a mix of 1 layer and 2 layers of vinyl and achieve good "bass" trapping - possibly enough not to need additional corner traps.
 
I have the same ceiling as you do - just lower - if I stand on my toes my head brushes the bottom of my rafters (no pogo dancing for me in my room!).
The cost of Mass Loaded Vinyl (MLV) has always put me off, but I might try some of these in the parts of the room I don't stand using off cuts of flooring vinyl and a bag of poly fluffy.
 
Hats off (again) to [mention=123017]svenr[/mention] for showing ways of using "non acoustic" products for room treatment.
 
Mike
I thought by reading a BBC document which uses hardboard instead of Vinyl, that filling it up with absorption drops the peak but widens the bandwidth.

Share this post


Link to post
Share on other sites


You guys have made a strong case for the ceiling that I truely considering it.

I am thinking about a combination of limp traps and absorber with a diffuse pattern of slabs.

I hope to be able to DIY this, but it will depend on material costs as well.

The cost of those slabs could quickly become rather expensive.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Snoopy8
      Introduction
      The purpose of this post is to re-introduce a software tool that configures multiple subwoofers (subs) to produce smooth bass in a room and at the same time, make it even across sitting positions.  A common misconception of adding subs for music is that they will artificially boost the bass.  Well integrated subs help restore the missing bass caused by the room and brings the body back to music.
       
      The usual approach to managing bass was room treatment first, followed by careful placement of speakers & subs. Hardware and/or software, often expensive, were also used. This case study shows why MSO is a good cost-effective software option.
       
      What is MSO?
      Multi-Sub Optimiser (MSO) is a FREE software tool to optimize multiple sub woofers by integrating the subs with main speakers and improving the evenness of bass response across the whole listening area. MSO is especially useful in non-dedicated rooms where there is limited (or no?) room treatment and WAF considerations dictate sub size, number and placements.  MSO also solves the difficult task of getting even bass across seating positions e.g. in multi row home theatres.
       
      MSO runs on a Windows laptop and requires a digital signal processor (DSP) and a calibrated microphone for use with REW (Room Equalisation Wizard) measurement software. There is some learning effort and time required to understand the concepts and set up the optimisation, but the results are worth it!  There is excellent documentation and a good tutorial.
       
      The program was written by AndyC on AVS Forum (discussion thread hosts all discussions, support, bugs etc.). Andy @andyc56 specifically joined SNA to support MSO.
       
      Why MSO? – A Case Study
      2 channel system was located in a non-dedicated open plan family room with high ceiling, hardwood floor on slab, blank wall in front, large windows with blinds on right, sliding glass doors with heavy curtains behind, left side opened to kitchen.  Thick rug, cushions and sofas (with some sound absorbing foam underneath) completed the “room treatment”.
       
       

       
      Main speakers were a pair of active SGR CX3Bs (Mk 1) and the measurements showed how good the speakers were by themselves. However, the room muddied the bass and there was less body in the music.
       
       
      Listening positions were in a single row with the main listening position (MLP) in the centre. Right4 was better half’s favourite spot and depending on how far she stretched her legs on the sofa, Left2 became a regular listening spot!   Left1 opened out to kitchen. The middle positions Left 2 and Right 3 graphs were offset -15 dB to improve readability.  Similarly,  outside positions Left 1 & Right4 offset -30 dB for readability.
       

       
       
      Subs were SVS SB13U and SB2000, located using “thirds criteria” in the front.  The room had limited options for subs placement and WAF considerations further restricted things. The unintegrated subs  (no adjustments to phasing, no eq, no cross over etc.)  made things  worse between 65 and 90 Hz.
       
       

      MSO used gains, delays, cross overs and PEQs to optimise the subs. Weightings for seating positions were Left1=0.5, Left2=0.9, MLP=1.0, Right4=0.8, Right5=0.5.  A target curve was used to lift the bass and compensate for large and open room.  
       
       
      Bass was even across 20 to 90 Hz and the dips were removed.  More impressive was the evenness across listening positions, even in Left1.  Right4’s improvement was under appreciated (everything was treated as muzak! SIGH!).  The graphs showed that excellent results could be achieved with dual subs and MSO, but what about listening tests?
       
       
      Using a SoTM SMS-200 Ultra network player and a Gieseler Groß DAC, Diana Krall’s My Love (double bass), Bach’s Tocatta & Fugue (organ) and Fleetwood Mac’s Dreams (drums) showed how good the bass was.  MSO brought the body back to the music and was probably the key enabler for further improving the 2 channel setup. Without MSO, I doubt I would have appreciated and enjoyed the Groß DAC as much.
       
       
      While this was 2 channel focused, MSO was also good for the home theatre. Using a different subs-only configuration, MSO took movies up a notch with additional slam on Anthem MRX 710 setup in same room. It made my favourite movie opening scene in Fellowship of the Rings superb. Was (and still am) no bass head, but understood why so many pursue this!
       
       
      SNA Reviews & Impressions
      There were at least 2 threads on MSO in the Room Acoustics, Construction and Design sub-forum.  Below were the reviews and impressions posted by members (will update if there are more posts):
      baMarek  8 Sep 16
      BradC 22 Nov 16
      mcb 23 Apr 17
      Snoopy8 5 Jun 17
       
       
       
      Conclusion
       
      This case study has shown that MSO is a good cost-effective software option to overcome the bass issues brought about by the room.  Hopefully, some here will try it for your setup.  And more than happy to assist you in your journey.
       
       
       
       
       
    • By Alpine Electrocats
      Item: Richard Allen bass drivers
      Location: Canberra
      Price: $200
      Item Condition: great
      Reason for selling: no longer needed
      Payment Method: Pickup - Cash, Paypal, COD Only
      Extra Info: I can post for $20. I bought these years ago thinking they were full range drivers- there are lots of jerks on eBay selling them as that, so not needed
       
      Pictures:






    • By Alpine Electrocats
      Item: Richard Allen bass drivers
      Location: Canberra
      Price: $200
      Item Condition: great
      Reason for selling: no longer needed
      Payment Method: Pickup - Cash, Paypal, COD Only
      Extra Info: I can post for $20. I bought these years ago thinking they were full range drivers- there are lots of jerks on eBay selling them as that, so not needed
       
      Pictures:
    • By baMarek
      Item: Tesla ARO 942 bass drivers
      Location: Perth
      Price: $700 ono
      Item Condition: very good (for vintage gear)
      Reason for selling: Moving
      Payment Method: Pickup - Cash, Paypal, COD Only
      Extra Info:
      Highly sought after and rare, the first edition of the iconic vintage bass drivers from Tesla. Paper cone, huge magnet, very high sensitivity. I had many drivers including Altecs and nothing in my experience came close in terms of quality of bass. This is the driver Lampizator used in his reference system.
       
      They are 30 Ohm. I have never had problems driving them but it's worth noting. One has a slight tear on the suspension part seen on the photo but it does not affect sound and stays covered behind the metal grill (included in price).
      Each speaker weighs 10kg.

      Pictures:
       
       




    • By Halfcast
      Near new, perfect condition and ready for Jaw dropping Hifi reproduction in your home are my Black
      Definitive Technology BP7001SC speakers (pair) which feature 1500 Watt Powered built in 10 inch subwoofers,
      Bi-polar design for the Ultimate Soundstage and Huge performance from a pair of floorstanding speakers that truly do not require a separate subwoofer.
      I will sell them for $2000 (Half of what I paid a year ago) including the boxes etc. RRP is $7999.
      Local pick up from Parklea NSW or Shipping Australia wide can be arranged at buyers expense.
      Please let me know if interested and come over for a demonstration.
      I'm selling the speakers way too cheap (losing $2000) in the hope that one of you guys will jump on it.
      The speakers are very efficient and will work with any amp with power output as little as 15W up to 500W RMS, They're 8ohm and a very healthy 92db.
      www.definitivetech.com/products/bp7001sc
      I'm happy to answer any enquiries..
×