DIY - Room Acoustics..

[elangoas]

Hi All,

Been reading some articles on room acoustics and some previous threads on this forum as well as other forums related to the topic.. I don't know if am right, but low density Broadband absorption seems to be one of the solution to address modal responses..

Here is a response of dual subs + Fronts..

From 10Hz - 20Khz..

From 10Hz - 500Hz..

and my living room room layout.. Room height is 9feet, 7 inches..

Am still trying to minimise the peaks/dips in sub-woofer range by re positioning dual DIY sealed subs in the room (or) would add 2 more if that would help for a smoother response below 80hz..

Above the sub-crossover range of 80Hz, to minimise the peaks/dips in the modal responses the most common suggested solution seem to be 6 inch of absorption on the front wall & part of back wall.. This being a living room, am limited with options to place 6 inch thick panels on walls.. There is lot of space in the ceiling that i can use.. Abt 18 ~ 20 inches from ceiling, i have no issues to use them..

Would it be better to use the entire ceiling space of 14 (W) x 11 (L) X 1.5 (H) feet for absorption in the room?.. Would absorption on ceiling help.. If so, how much thickness is good / how much area is good?..

If adding absorption to ceiling will not help, i will re-consider walls..

 

[Dr.Lakshay]

@elangoas Though I am not the best person to have a say in this topic as I have very little knowledge but from what I have read, bass traps are best put in the corners of the room first. As those are the major hot spots. At the junction of wall and ceiling, At the junction of 2 walls. As you have stepped into diy I would say you can try a diy and make a triangular shaped bass trap with wood wool or rock wool and cover it with a good looking cloth to match your room so that it doesn't look ugly. If you have the space and if planned well base traps can fit in the room very well. Something like this : https://www.bajaao.com/products/aur...9hn5dGgac9CoHGvVClOc5kEdVRLPtyDEaAmWGEALw_wcB

 

[elangoas]

@elangoas Though I am not the best person to have a say in this topic as I have very little knowledge but from what I have read, bass traps are best put in the corners of the room first. As those are the major hot spots. At the junction of wall and ceiling, At the junction of 2 walls. As you have stepped into diy I would say you can try a diy and make a triangular shaped bass trap with wood wool or rock wool and cover it with a good looking cloth to match your room so that it doesn't look ugly. If you have the space and if planned well base traps can fit in the room very well. Something like this : https://www.bajaao.com/products/aur...9hn5dGgac9CoHGvVClOc5kEdVRLPtyDEaAmWGEALw_wcB

Thx for the suggestion.. Am trying to interpret from the specs in the link,

• Bulk density: 23 ±2kg/m³.
• Dimensions: 24" x 12" x 8"
• NRC: 1.4

From very lil of what i have been reading, this seems to be low density 24kg/m3 and thickness of 8 inches., with a coefficient of 1.4, but no mention of which freq.. I think it should be between 100 - 200 Hz..

Am thinking in the lines of having an 6 / 8 inch absorber on ceiling with larger panels, which can absorb more range of frequency..

Here is a link that was shared in previous threads - https://www.bobgolds.com/AbsorptionCoefficients.htm

From the above link, here is an image of the details in a spreadsheet..

If you look at the highlighted part, 4/6 inch panels for the same density (48kg/m3), 6 inch panel has more absorption below 500Hz.. So my guess is 8 inch absorber would be more effective for < 500hz.. (though not very sure)..

Am still unsure which among 24 (or) 48 kg/m3 is better?, how much area is needed?, if thick ceiling absorber will be better?.. No idea on what is balanced approach..

The idea for my living room is to have thicker absorbers (6 ~ 8 inch) on ceiling and thinner absorbers (if reqd) on walls (2 ~3) inch.. (if the idea is right, so fingers crossed)..

 

[Dr.Lakshay]

Sir have you thought about adding a dsp from the likes of minidsp or may be an amp with dsp like behringer inuke 3000dsp. I believe a dsp will do more wonders than any room treatment as you can control very specifically on a dsp. It could prove quite costly to get that perfect room treatment.
I saw a video by audioholics on YouTube where they said that dsp is a better option than putting those huge bass traps. They also have a 50 min video tutorial on how to tame bass using a minidsp, didn't get the time to watch it.

Thx for the suggestion.. Am trying to interpret from the specs in the link,

• Bulk density: 23 ±2kg/m³.
• Dimensions: 24" x 12" x 8"
• NRC: 1.4

From very lil of what i have been reading, this seems to be low density 24kg/m3 and thickness of 8 inches., with a coefficient of 1.4, but no mention of which freq.. I think it should be between 100 - 200 Hz..

I pasted the link just for reference. I think foam absorbers wouldn't do much for bass for that they'll need to be bulky. I guess Rockwool, mineral wool would be more suited for bass entrapment.

 

[elangoas]

Sir have you thought about adding a dsp from the likes of minidsp or may be an amp with dsp like behringer inuke 3000dsp. I believe a dsp will do more wonders than any room treatment as you can control very specifically on a dsp.

Am a novice with dsp and tweaking, so not getting there for now.. My AVR already has Audyssey XT32, which is one of the better room correction comparable with Dirac & other similar offerings.. Also have the Multi EQ Editor mobile app, which i think gives the flexibility to user, to apply EQ only for the selected range of freq..

It could prove quite costly to get that perfect room treatment.

True.. Am not chasing perfect response (or) perfect room treatment.. Just trying to minimise the peaks / dips for a certain range of freq thru these absorption and use Audyssey EQ..

I saw a video by audioholics on YouTube where they said that dsp is a better option than putting those huge bass traps. They also have a 50 min video tutorial on how to tame bass using a minidsp, didn't get the time to watch it.

Ok..Will check them..

I pasted the link just for reference.

Got that.. I too was just interpreting the specs to understand and get corrected if it was wrong..

I think foam absorbers wouldn't do much for bass for that they'll need to be bulky. I guess Rockwool, mineral wool would be more suited for bass entrapment.

Yes.. Looking for more inputs on right density, right area, right thickness..

 

[prateekatasniya]

First a room should be treated only then dsp should be used..
Peaks can be treated using dsp.. But what about dips ? How will one correct the dips (which might be 10db or more) using dsp ?

 

[prateekatasniya]

40-50kg/m3 should be the target density..

 

[prateekatasniya]

Try mmt bass traps.. 40kg/m3 density..
Others are 24kg/m3.

 

[matbhuvi]

Low frequency is very tough to control through acoustic treatment. If your AVR support parametric EQ, try to apply manual correction to tackle resonance. It is very simple and it is based on room dimensions

 

[prateekatasniya]

Hi All,

Been reading some articles on room acoustics and some previous threads on this forum as well as other forums related to the topic.. I don't know if am right, but low density Broadband absorption seems to be one of the solution to address modal responses..

Here is a response of dual subs + Fronts..

From 10Hz - 20Khz..

From 10Hz - 500Hz..

and my living room room layout.. Room height is 9feet, 7 inches..

Am still trying to minimise the peaks/dips in sub-woofer range by re positioning dual DIY sealed subs in the room (or) would add 2 more if that would help for a smoother response below 80hz..

Above the sub-crossover range of 80Hz, to minimise the peaks/dips in the modal responses the most common suggested solution seem to be 6 inch of absorption on the front wall & part of back wall.. This being a living room, am limited with options to place 6 inch thick panels on walls.. There is lot of space in the ceiling that i can use.. Abt 18 ~ 20 inches from ceiling, i have no issues to use them..

Would it be better to use the entire ceiling space of 14 (W) x 11 (L) X 1.5 (H) feet for absorption in the room?.. Would absorption on ceiling help.. If so, how much thickness is good / how much area is good?..

If adding absorption to ceiling will not help, i will re-consider walls..

People think bass trapping will reduce the bass intensity.. But its opposite.
A small subwoofer in a treated room sounds much better than a big sub in a untreated room.
Reason is untreated room causes cancellation. Look at those dips in the frequency response. Extreme dips. At around 90 hz there's more than 25db dip. That's staggering.

 

[prateekatasniya]

Low frequency is very tough to control through acoustic treatment. If your AVR support parametric EQ, try to apply manual correction to tackle resonance. It is very simple and it is based on room dimensions

Getting perfection is difficult.. but first treat with acoustics then using EQ.

 

[prateekatasniya]

Getting perfection is difficult.. but first treat with acoustics then using EQ.

How will one decrease the decay time using EQ ??
People forget that part.
Lesser the decay time- tighter the sub will sound.

 

[matbhuvi]

Getting perfection is difficult.. but first treat with acoustics then using EQ.

Room treatment for below 100hz?. Good luck. Unless you have insanely expensive diaphragmatic absorbers or the ones which run into feet's, it is pretty difficult. 6 - 8 inch absorbers or not going to help.
Dual subs do cancel out the dips. So, I am surprised here a bit. May be there is an issue with placement?

With very conservative q factor as explained in the video, you can takle the resonance in the listening area. But again, it is going to be small area. Definitely worth it.

 

[elangoas]

People think bass trapping will reduce the bass intensity.. But its opposite.

Think trapping depends on the frequencies.. Anything below 80Hz is most difficult to treat, where multiple subs help minimise the peaks and dips.. These absorbers seem to work from 100Hz, according to the absorption co-efficient..

A small subwoofer in a treated room sounds much better than a big sub in a untreated room. Reason is untreated room causes cancellation.

When you say treated rooms, for what freq are the room treated?.. For smoother response below 80Hz, think only placement can help..

No one at home would be able to do room treatment for freq below 80Hz - https://www.jdbsound.com/art/frequency wave length chart 2013.pdf

To treat a 80hz, the bass trap has to be 42 inches thick, and anything below 80Hz, it will Just be impractical..

Look at those dips in the frequency response. Extreme dips. At around 90 hz there's more than 25db dip. That's staggering.

Yes.. It was there in my earlier measurements, but not 25 dB deep.. I don't know why it happened.. Front L-C-R are wall mounted..

Here is my earlier measurement with Dual subs + L/R speakers at the same place as it is now (with 80Hz crossover).. There is no dip at 90Hz..

 

[elangoas]

Good one.. There wasn't a mention of height of the room (height room mode) in this video (or) i guess he was probably helping to calculate length & width of his room as examples..

Just asking for clarity - If one were to use this, then i guess he needs to calculate the resonant modes with all three room dimension.. (Width, length & height) and the multiples of it until which freq?.. (500 - 600hz)?..

Although am novice to Parametric EQ and its functions, there is a mention of reducing resonant freq by -15dB, max of -20dB.. But in actual room conditions, a peak is sometimes 25dB.. So i guess, this method will help to minimise the peaks to the extent possible..

Sorry, if i have asked anything incorrectly in relation to this topic and help me understand better..

 

[prateekatasniya]

https://www.auralexchange.com/produ...-0-6m-mineral-wool-acoustic-insulation-board/

Nrc 0.76 at 50hz
Check this.
Is it possible ?

 

[sound_cycle]

Just asking for clarity - If one were to use this, then i guess he needs to calculate the resonant modes with all three room dimension.. (Width, length & height) and the multiples of it until which freq?.. (500 - 600hz)?..

Amroc room calculator ? It has a three D visualization. IIRC REW also has a room simulator. you plug in your room dimensions and then it shows you the room modes overlaid on your measurements.

ciao
gr

 

[elangoas]

https://www.auralexchange.com/produ...-0-6m-mineral-wool-acoustic-insulation-board/

Nrc 0.76 at 50hz
Check this.
Is it possible ?

This seems to be high density 120kg/m3, not very sure if it would actually absorb a 50Hz freq, but might absorb more in >50hz.. Measurements pre & post adding panels should help validate it..

Here is a thread from AVS forums - https://www.avsforum.com/forum/19-d...a-budget-9-1-6-12x12-room-4.html#post50720297

This member has actually used 10Kg/m3 Rockwool density, with 10 inch thickness on his ceiling..

If you look at the REW measurements in the above post on AVS forums, the decay times has reduced to great extent from 50Hz - 700Hz..

You can also see decay time at 50Hz hasn't reduced for this member even after adding so much absorber on ceiling.. So in that regard, the above absorber in your link might not cut it for 50Hz..

The AVS FM room height was only 8.2 feet, of which he did this.. I have 9.7 feet height ceiling, of which 18 inches from ceiling is unused space.. So if i do a similar approach, it might work..

 

[elangoas]

Amroc room calculator ? It has a three D visualization. IIRC REW also has a room simulator. you plug in your room dimensions and then it shows you the room modes overlaid on your measurements.

Yes, i have used the room mode simulator in REW.. But wasn't aware that the room modes simulator results can be overlaid on the measurements.. Will check them..

 

[matbhuvi]

Good one.. There wasn't a mention of height of the room (height room mode) in this video (or) i guess he was probably helping to calculate length & width of his room as examples..

Just asking for clarity - If one were to use this, then i guess he needs to calculate the resonant modes with all three room dimension.. (Width, length & height) and the multiples of it until which freq?.. (500 - 600hz)?..

Although am novice to Parametric EQ and its functions, there is a mention of reducing resonant freq by -15dB, max of -20dB.. But in actual room conditions, a peak is sometimes 25dB.. So i guess, this method will help to minimise the peaks to the extent possible..

Sorry, if i have asked anything incorrectly in relation to this topic and help me understand better..

This is my understanding. Sound does go in all directions. But, where the large wavelength of low frequency gives more problem is the reflected sound from back wall. Hence he is guessin

Good one.. There wasn't a mention of height of the room (height room mode) in this video (or) i guess he was probably helping to calculate length & width of his room as examples..

Just asking for clarity - If one were to use this, then i guess he needs to calculate the resonant modes with all three room dimension.. (Width, length & height) and the multiples of it until which freq?.. (500 - 600hz)?..

Although am novice to Parametric EQ and its functions, there is a mention of reducing resonant freq by -15dB, max of -20dB.. But in actual room conditions, a peak is sometimes 25dB.. So i guess, this method will help to minimise the peaks to the extent possible..

Sorry, if i have asked anything incorrectly in relation to this topic and help me understand better..

You don't need that calculation as you have already measured the frequency response. Just cross verify whether the peaks/dips occuring at the intended frequencies based on room dimensions. The solution in plain words is pretty simple. Suppress the peaks with conservative Q factor so that DSP effect are minimal. Do not alter other areas as we don't want any filter to impact the natural DAC's flavor as much as possible. I won't be bothered with 2/3db peaks/dips for the same reason.