Jump to content

Acoustic treatment.


Recommended Posts

Hi guys.

I need bass traps for my room to go behind my head on the wall. I just want to treat the low end. I don't mind making them but i have no idea what's the best to use or where to get them. I live in Melbourne. Ill take a picture of my bedroom. Any advice would be greatly appreciated. I don't want to absorb the bass, i just want it to sound better. The photos are of my room clockwise. b3a6127833ce5d92e36ed2bcbc9865e7.jpg562b55a66780ea647bd863f8bffeae14.jpg69efa41ed525a0391c6d8cbe6ba40663.jpg46af647c823530bf2e8490a4197a5d82.jpg8c6fe06a8f349b0d21cf70cbab256707.jpg

Link to comment
Share on other sites



On 19/11/2017 at 11:59 PM, jmouss said:

 

I don't want to absorb the bass, i just want it to sound better.

 

How does the room sound when you do a loud single hand clap?  Is there much reverb?
I'd start with some front and side wall treatments first to reduce reflections and add thicker material as you go. 

 

Bass traps are designed to "trap the bass" so that it does not reflect uncontrolled around the room.  When that happens, you get inphase and out of phase collisions and this creates the peaks and dips.  Adding traps really requires in room measurements.  Typically bass traps are big and made from dense materials like fibreglass (the stuff you stick in the walls.)  Be careful, I have heard a room that over did it and in the end, they had a suck out in the range most rooms peak (40Hz~70Hz).     

 

When I added foam to my corners, I had measured 10dB peaks at 35Hz!  Adding foam plus moving the subs a bit and I was able to pull that down to just 4dB.  EQ is really the next step for me. 

I am looking at a mini DSP (EQ and crossover) and 6CH Rotel amp for my LCRs.    

Link to comment
Share on other sites

How does the room sound when you do a loud single hand clap?  Is there much reverb?
I'd start with some front and side wall treatments first to reduce reflections and add thicker material as you go. 
 
Bass traps are designed to "trap the bass" so that it does not reflect uncontrolled around the room.  When that happens, you get inphase and out of phase collisions and this creates the peaks and dips.  Adding traps really requires in room measurements.  Typically bass traps are big and made from dense materials like fibreglass (the stuff you stick in the walls.)  Be careful, I have heard a room that over did it and in the end, they had a suck out in the range most rooms peak (40Hz~70Hz).     
 
When I added foam to my corners, I had measured 10dB peaks at 35Hz!  Adding foam plus moving the subs a bit and I was able to pull that down to just 4dB.  EQ is really the next step for me. 

I am looking at a mini DSP (EQ and crossover) and 6CH Rotel amp for my LCRs.    
Hey thanks cavx for your response. Appreciate it. When i clap my hands there is no reverb. I think this is due to the big mattress and other stuff in my room. So you think just start with some side and front wall stuff. When you say front wall that always indicates the wall at which you view everything? Do you think the foam stuff from Clark's rubber is fine?
Link to comment
Share on other sites

8 hours ago, jmouss said:
10 hours ago, CAVX said:
How does the room sound when you do a loud single hand clap?  Is there much reverb?
I'd start with some front and side wall treatments first to reduce reflections and add thicker material as you go. 
 
Bass traps are designed to "trap the bass" so that it does not reflect uncontrolled around the room.  When that happens, you get inphase and out of phase collisions and this creates the peaks and dips.  Adding traps really requires in room measurements.  Typically bass traps are big and made from dense materials like fibreglass (the stuff you stick in the walls.)  Be careful, I have heard a room that over did it and in the end, they had a suck out in the range most rooms peak (40Hz~70Hz).     
 
When I added foam to my corners, I had measured 10dB peaks at 35Hz!  Adding foam plus moving the subs a bit and I was able to pull that down to just 4dB.  EQ is really the next step for me. 

I am looking at a mini DSP (EQ and crossover) and 6CH Rotel amp for my LCRs.    

Read more  

Hey thanks cavx for your response. Appreciate it. When i clap my hands there is no reverb. I think this is due to the big mattress and other stuff in my room. So you think just start with some side and front wall stuff. When you say front wall that always indicates the wall at which you view everything? Do you think the foam stuff from Clark's rubber is fine?

Not no reverb, maybe just not hearing anything offensive.  If the room has reflective walls, it is going to have some reflection.  Whether it bothers you or not is another thing.    

 

I never really understood what I was supposed to hear or not hear until I added foam and other sound absorbing panels to walls. Then, when I couldn't hear certain things, I suddenly realized how much I was ignoring the issues in the room.    

 

Yeah front wall is screen or LCR wall. 

 

Link to comment
Share on other sites

Not no reverb, maybe just not hearing anything offensive.  If the room has reflective walls, it is going to have some reflection.  Whether it bothers you or not is another thing.    
 
I never really understood what I was supposed to hear or not hear until I added foam and other sound absorbing panels to walls. Then, when I couldn't hear certain things, I suddenly realized how much I was ignoring the issues in the room.    
 
Yeah front wall is screen or LCR wall. 
 
Hey bro can you send me a pick of your treatment. Is that ok.?
Link to comment
Share on other sites



36 minutes ago, jmouss said:
38 minutes ago, CAVX said:
Not no reverb, maybe just not hearing anything offensive.  If the room has reflective walls, it is going to have some reflection.  Whether it bothers you or not is another thing.    
 
I never really understood what I was supposed to hear or not hear until I added foam and other sound absorbing panels to walls. Then, when I couldn't hear certain things, I suddenly realized how much I was ignoring the issues in the room.    
 
Yeah front wall is screen or LCR wall. 
 

Read more  

Hey bro can you send me a pick of your treatment. Is that ok.?

HERE is a link to my blog where I documented my room build.  

Link to comment
Share on other sites

I'd get a pack Polymax XHD 100mm thick. Put a full sheet (2.4m x 1.2m x 100mm) behind each front speaker/subwoofer and cut the third sheet into 4 pieces (1.2m x 60cm x 100mm) and put 2 at the first reflection points and 2 either side of the picture behind your head. It comes in black or white and if your neat enough with the cuts it doesn't "require" covering to look acceptable. Also completely safe and non itchy like fibreglass. 

  • Like 2
Link to comment
Share on other sites

15 hours ago, jamiebosco said:

I'd get a pack Polymax XHD 100mm thick. Put a full sheet (2.4m x 1.2m x 100mm) behind each front speaker/subwoofer and cut the third sheet into 4 pieces (1.2m x 60cm x 100mm) and put 2 at the first reflection points and 2 either side of the picture behind your head. It comes in black or white and if your neat enough with the cuts it doesn't "require" covering to look acceptable. Also completely safe and non itchy like fibreglass. 

Sounds (yes pun intended) like a good solution.  How much is this stuff and where do you buy it?  

  • Like 1
Link to comment
Share on other sites

Also look into Bradford Soundscreen, harder to work with and needs frames built but i believe its the new industry standard from Bradford (replacing the polymax although they still sell polymax), ive got 9 panels in my room and its done the trick.  Depending on you situation and space i would also look into the "Limp Membrane" bass trap.  Its the best DIY solution to dealing with the real deep lower frequencies.  But you need to be a handy DIYer and they take up a fair bit more space than insulation batt panels.

Link to comment
Share on other sites



9 hours ago, CAVX said:

Sounds (yes pun intended) like a good solution.  How much is this stuff and where do you buy it?  

Yes it's very good stuff, I've had mine a while, from memory I think a pack was around $300(ish). Mine was a bit more because I wanted the Black colour . I got it directly from Bradford in Brisbane, I had to drive nearly an hour each way to get it , and now their new plant is 5 mins from my house lol. I think they call it "Absorb XHD" now though

 

 

 

Edited by jamiebosco
  • Like 1
Link to comment
Share on other sites

The R-value is a measure of the product's thermal performance, i.e. resistance to transfer of heat through the material. A higher R-value means greater resistance or more thermal insulation. R-value is not directly relevant for your intended purpose as acoustic treatment, though indirectly related insofar as R-value is largely a factor of material thickness and density and these things also influence acoustic performance.

Link to comment
Share on other sites



Just looking at the first image and I'd be moving the right speaker in closer to the TV.  Non-uniform spacing of L and R would drive me crazy.  Room boom could even be addressed by turning a sub 90 degrees, but the picture/sound cues being out due to speaker mis-placement is a much bigger concern.  

Link to comment
Share on other sites

On 11/26/2017 at 8:37 PM, CAVX said:

Isn't R4 more dense?  Therefore would it not treat to a lower frequency?   

typically R value relates to thickness when comparing similar products - so an R2 product will be thinner than R2.5 or 3 or 4 - but likely all the same density in the same product range, just thicker/thinner.

 

If you're seeking best performance as low as possible, then stick with Polymax XHD - the others work fine also, but you need more of it. I prefer Poly over Fiberglass, but Fiberglass works at least as well as Poly - but needs to be covered.

On 11/19/2017 at 11:59 PM, jmouss said:

 

Hi guys.

I need bass traps for my room to go behind my head on the wall. I just want to treat the low end. ...

.... I don't want to absorb the bass, i just want it to sound better.

 

mmmm - you only want to treat the low end, and not absorb the bass, but you want it to sound better...??

  • Treating only the low end requires a tailored approach using pressure traps rather than absorption, or absorption covered in a membrane to reflect higher frequencies
  • You do want treatment to absorb bass, as that will make it sound better - much better
On 11/26/2017 at 8:37 PM, CAVX said:

Isn't R4 more dense?  Therefore would it not treat to a lower frequency?   

Density doesn't equate to better low frequency performance - put simply, large and larger traps help lower frequencies - once traps get too big, EQ works well.

With large enough traps, ordinary "fluffy" insulation works as well as PolyMax XHD, but takes up more real estate in the room.

 

cheers

Mike

Link to comment
Share on other sites

Just looking at the first image and I'd be moving the right speaker in closer to the TV.  Non-uniform spacing of L and R would drive me crazy.  Room boom could even be addressed by turning a sub 90 degrees, but the picture/sound cues being out due to speaker mis-placement is a much bigger concern.  
Hi cavx. I would move the right speaker closer but i don't know where to put the sub. These xs30s are really heavy. Any ideas?
Link to comment
Share on other sites

Density doesn't equate to better low frequency performance - put simply, large and larger traps help lower frequencies - once traps get too big, EQ works well.
With large enough traps, ordinary "fluffy" insulation works as well as PolyMax XHD, but takes up more real estate in the room.
 
cheers
Mike
Hey almikel . Thanks for your response. I'm thinking of getting the xhd 50mm. Would that make a good difference to the bass? Also do i need to cover the face of them with some membrane .
Link to comment
Share on other sites



16 hours ago, jmouss said:
On 26/11/2017 at 10:40 PM, CAVX said:
Just looking at the first image and I'd be moving the right speaker in closer to the TV.  Non-uniform spacing of L and R would drive me crazy.  Room boom could even be addressed by turning a sub 90 degrees, but the picture/sound cues being out due to speaker mis-placement is a much bigger concern.  

Hi cavx. I would move the right speaker closer but i don't know where to put the sub. These xs30s are really heavy. Any ideas?

Whilst I am not a fan of corner placement, I'd rather have the sub fire across the LCR array than have a mis-aligned LCR array.  Is it possible to swap the sub and stand placement?

Link to comment
Share on other sites

Whilst I am not a fan of corner placement, I'd rather have the sub fire across the LCR array than have a mis-aligned LCR array.  Is it possible to swap the sub and stand placement?
Hey cavx. I can move the sub closer to the corner and move the stand closer to the tv. I just hope the leads hdmi cables etc will reach. But then again maybe i can get a little stand and put the avr on it. I'm not a fan of corner placement either. I find the bass is bigger but the quality and smoothness isn't.
Link to comment
Share on other sites

Hey almikel . Thanks for your response. I'm thinking of getting the xhd 50mm. Would that make a good difference to the bass? Also do i need to cover the face of them with some membrane .

50mm won’t do much for bass
Do a google search for “porous absorber calculator”
Have a play - polymax xhd is approx 14000 rayls for gas flow resistivity

100mm thick 600mm wide straddling corners or gapped 100mm would be the absolute minimum size to get much performance below 150-200hz

200mm deep 1000mm wide floor to ceiling straddling corners required to trap down to 100hz

Cheers
Mike
  • Like 1
Link to comment
Share on other sites

7 hours ago, jmouss said:
8 hours ago, CAVX said:
Whilst I am not a fan of corner placement, I'd rather have the sub fire across the LCR array than have a mis-aligned LCR array.  Is it possible to swap the sub and stand placement?

Hey cavx. I can move the sub closer to the corner and move the stand closer to the tv. I just hope the leads hdmi cables etc will reach. But then again maybe i can get a little stand and put the avr on it. I'm not a fan of corner placement either. I find the bass is bigger but the quality and smoothness isn't.

There is always going to be a level of compromise in a HT.  I think symmetrical placement of LCR speakers around the screen is more important than a sub close to corner.  

  • Love 1
Link to comment
Share on other sites

19 hours ago, CAVX said:

There is always going to be a level of compromise in a HT.  I think symmetrical placement of LCR speakers around the screen is more important than a sub close to corner.  

totally agree this is critical. 

Placement of sub is important also, but can't be allowed to impact LCR - get longer cables for the sub.

The sub needs to go wherever your get the smoothest/best response - which "could" be anywhere in the room (hidden under the bed may work very well) - the best way to tell what sub positions are best is to place the sub at the listening position and measure the response (preferably with a measurement mic) at each likely sub position. Room EQ Wizard (REW) and a USB measurement mic is perfect for this.

https://www.minidsp.com/products/acoustic-measurement/umik-1

REW is free but requires a Windows laptop.

 

On 11/29/2017 at 4:54 PM, almikel said:


50mm won’t do much for bass
Do a google search for “porous absorber calculator”

here's a handy tool for modelling absorption

http://www.acousticmodelling.com/porous.php

I used the 14000 for the Gas Flow Resistivity of Polymax XHD - this was from memory, and it could be closer to 12000 - someone may be able to confirm?

This tool doesn't model corner straddling absorption, nor am I aware of any tools that do.

 

The attached screenshot compares 50mm of Polymax on a wall with 200mm of Polymax with 100mm air  gap

5a1fcc3fb2128_50mmvs200mmPolymax.thumb.JPG.d27584702fb709a89026fa3eec1d149a.JPG

You can see that 50mm of Polymax on a wall is not a bass trap and has almost no effect on bass frequencies.

200mm of Polymax with 100mm gap is not a "bass trap" either, but a broadband absorber working pretty well down to 400Hz with still reasonable but reducing effect below. You could cover this with a membrane (eg builders plastic) that would reflect higher frequencies and make it a "bass" trap (ie trap bass, but not absorb higher frequencies).

Unless absorption is covered in a membrane to reflect higher frequencies, it's never a "bass" trap, but if large enough and gapped enough it can be a broadband trap able to absorb "lower" frequencies - how low depends on the size and gapping.

Another approach for "bass traps" is a tuned membrane (pressure) trap - these can work for problem areas lower than absorption can, but are "narrow band" devices and need to be tuned for the specific problem frequencies - I've never built one, as I've achieved an "acceptable" response in my room with absorption working above 100Hz, a leaky room from a bass perspective (lightly constructed) and EQ.

 

At some stage I'm keen to experiment with some Mass Loaded Vinyl as the membrane on some pressure traps in the corners - lack of spare funds and the lazy DIY in me has meant this hasn't occurred yet (same for Diffusion projects etc etc). 

 

My lightly constructed room with lots of absorption and EQ below 100Hz sounds pretty good - far better than any cinema I've been in.

IMHO if you want to achieve the best "In Room" sound, then target treatment in the low end first - once you get the bass under control (using treatment and maybe EQ below 100Hz), further treatment may not be required - or you may find you've added so much absorption that the room has become "too dead" - in which case you can maintain the bass absorption, but keep treble energy in the room by covering the absorption with any membrane, or maybe slats in a random pattern to generate some diffusion at higher frequencies (eg like a 1D BAD panel approach).

 

Some good articles that I've found very informative are @Paul Spencer bass integration guides.

Part 1 linked here:

http://www.hifizine.com/2011/06/bass-integration-guide-part-1/

 

The over use of absorption in rooms when not targeting bass as the priority can lead to terrible results. 

I've been in many band practice rooms with besser block walls (ie rigid and very bass reflecting) with carpet/egg crate foam/thin absorption on the walls - leading to boomy bass with the treble chopped out - just awful.

If you target bass with absorption, you place absorption straddling corners (any corner of the 24 corners available in a room), which won't absorb direct treble or 1st reflected treble - very little chance of making the room "too dead". Keep adding absorption straddling corners until the bass is under control, using EQ for issues <100Hz..

 

IME once the bass is clean and tight, you've got great sound in the room - better sound is possible, but the usual rules of diminishing returns apply.

 

Treatment IME is the best "bang for buck" improvement to the "in room" sound possible when done well - but in the case of many band practise rooms I've been in, can make things worse.

 

I would focus your treatment approach at the bass end first for best results.

 

cheers

Mike

  • Like 3
Link to comment
Share on other sites



  • Recently Browsing   0 members

    • No registered users viewing this page.




×
×
  • Create New...
To Top