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I want to tweak the live room acoustics - Home style..
Old 8th August 2019
  #1
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I want to tweak the live room acoustics - Home style..

My live room is 110"w x 144"L x 81" ~(9'w x 12'L x 6'9"h)

Floor is concrete.
3 walls are cinder block.
4th wall is 2 layers of 5/8" dry wall
Ceiling rafters are stuffed with R19 pink fluffy and finished with 12" "acoustical tile" from Lowes.

I have treated the corners with 72"h x 15"w x 6"d traps filled with R19 pink fluffy. straddling the corners.

Each wall has 1 Large absorber - 70"h x 48"w x 6"d filled with roxul Safe n' sound spaced 2-3" from the wall

I forgot about the Arqen diffuser I built. Its in their too

Is it significantly better overall with thedescribed treatment? Yes.
Is it dry as dust sonically? Yes

It still feels like I have not gotten to the lowest frequencies. Drums still feel boomy in the lows and light in the top end.

A few questions:

1) Should I "double up" 2 of the large wall panels on one wall to get more depth to address lower frequencies than I can with 6"?

I have 2 DIY 4' x 2' Polys built from left over materials and filled with 2 sheets of Safe n Sound and two 4' x 2' "diffusors" made from Auralex T fuser and Metro fusors I bought many years ago when I was ignorant of such things that have been collecting dust. Working with what I have on hand

2) How effective would these be in livening up the room a touch if used in place of the wall absorber I moved to double up on the other wall ?

3) Would adding slats to the large panels help with balancing the room? how much coverage vs how much space? I have read the coverage needs to be a significant percentage to be effective. 90% and up. Is that correct?

4) Do the slats need to be a particular thickeness to be effective? ie do they need to be 3/4" or more thick or could I cut them out the extra pegboard I have laying around?
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Last edited by AudioWonderland; 9th August 2019 at 02:20 PM..
Old 9th August 2019
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Updated with Photos
Old 10th August 2019
  #3
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I don't see any modal region treatment. Hence your problem with your drum sound.
Old 10th August 2019
  #4
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Quote:
Originally Posted by JayPee View Post
I don't see any modal region treatment. Hence your problem with your drum sound.
Can you clarify? Are you talking about the dips and peaks in the low-end small rooms have? Doubling up the existing panels was meant to be an attempt to do that. 12" safe n sound probably is not deep enough to get there. I think at least 18 to get down to 40hz?

Last edited by AudioWonderland; 10th August 2019 at 04:18 PM..
Old 10th August 2019
  #5
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Dip and peaks occur in every untreated rooms. Or in every badly treated rooms.

But it's not all bout dips and peaks but decay (resonance).

First, there is no right or wrong way to design a live room. Design depends on your instruments as well and their position within the room.

But in every designs, bass should be under controlled to avoid what you described : boomy low end and 'light on high frequencies'.

You absorbed your highs and left the basses unnafected by your treatment. Leading to dead sounding space, like you described.

Adding slats might recover your highs but won't do anything for your basses if not done in a proper design.

Velocity based vs. pressure based absorbers
Old 10th August 2019
  #6
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Quote:
Originally Posted by JayPee View Post
Dip and peaks occur in every untreated rooms. Or in every badly treated rooms.

But it's not all bout dips and peaks but decay (resonance).

First, there is no right or wrong way to design a live room. Design depends on your instruments as well and their position within the room.

But in every designs, bass should be under controlled to avoid what you described : boomy low end and 'light on high frequencies'.

You absorbed your highs and left the basses unnafected by your treatment. Leading to dead sounding space, like you described.

Adding slats might recover your highs but won't do anything for your basses if not done in a proper design.

Velocity based vs. pressure based absorbers
I have read through the link. I agree with the need to do something to address the low end. The question is how, what and how much?

Much of the discussion was a bit above my current understanding of the nuances.
A tuned absorber is probably the most space efficient but if you don't hit all the marks it's not going to help. I don't have five feet of space to give up. Do nothing isn't a good option but firing blind is equally untenable.

It's not a pro room obviously. There is no budget to hire pros. I am on my own to sort it out. A wall of 18" rockwool did good things in the control room but it doesn't address how dry the room is. How do you bring life to a room like this?
Old 10th August 2019
  #7
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Quote:
A wall of 18" rockwool did good things in the control room but it doesn't address how dry the room is. How do you bring life to a room like this?
Cover the Rockwool with reflective and/or diffusive surfaces. Either partial or total coverage, as needed.

- Stuart -
Old 11th August 2019
  #8
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Quote:
Originally Posted by Soundman2020 View Post
Cover the Rockwool with reflective and/or diffusive surfaces. Either partial or total coverage, as needed.

- Stuart -
Thickness matter? 1/8" plywood or pegboard work or does it need to be thicker?
Old 15th August 2019
  #9
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Quote:
Originally Posted by Soundman2020 View Post
Cover the Rockwool with reflective and/or diffusive surfaces. Either partial or total coverage, as needed.

- Stuart -
I keep seeing that pegboard is bad to use for fronting the Rockwell because of the perforations.. How is that different than slats? Would pegboard material without the holes be acceptable?

I have moved the 6" and 12" absorbers 4" off the walls which should help get a little deeper. I just don't have the space or budget to do much more so just trying to maximize what I have
Old 4 weeks ago
  #10
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If sealed, you'll get a' helmholtz resonator.

Since pegboard has fixed ratio porosity, you'll need to tune your device by playing with cavity behind your pegboard.

More thickness will lower the fc.
Old 4 weeks ago
  #11
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Quote:
Originally Posted by JayPee View Post
If sealed, you'll get a' helmholtz resonator.

Since pegboard has fixed ratio porosity, you'll need to tune your device by playing with cavity behind your pegboard.

More thickness will lower the fc.
Not sealed. Just hung by two nails so it could be easily be added/removed/adjusted as desired. They would probably only cover 1/3 to 2/3 of the front of the absorber. A solid surface alternative is possible. I just want to understand the differences between the two, if any, in this application.

Does the thickness of the material impact the range of frequencies reflected or is that just a function of surface area? If I understood you correctly a thicker material will reflect to a lower frequency?

Last edited by AudioWonderland; 4 weeks ago at 01:21 PM..
Old 4 weeks ago
  #12
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As JayPee mentioned, pegboard can be used to create a tuned resonant trap, if the cavity behind it is sealed. But that's not what you want to do: you just want to have it sitting there, with no sealed cavity. So, it will just be a reflector, basically... but it might also resonate! Pegboard is thin and somewhat flexible, so if there's a large unsupported area then it can vibrate in sympathy with certain frequencies. Probably not to much of an issue, to be honest, but it is possible.

So, as a reflector: it will reflect highs back into the room, and allow lows to pass through, where they can be absorbed by the Rockwool. The question is: where is "crossover" point for that? If lows pass through and highs are reflected, then you'd expect there must be some point on the spectrum where it stops reflecting: everything above that is reflected, and everything below that is not reflected but allowed to pass through. And if you suspected that, then you'd be right! There is, indeed, such a point.. but it isn't a sharp step. Rather, it's a gradual curve. There is a center point, and the reflections rise at about 6 dB per octave above that point, falling about 6 dB per octave below that. In other words, at 20 kHz it will reflect pretty much everything, and at 20 Hz it won't reflect at all, being basically transparent to that low frequency.

The location of that center point is not so easy to define, but it basically depends on the density and thickness of the material, in this case the pegboard. There's an equation that I have that I'm a little suspicious of because I can't find the justification for it, or the original source, but seems to work reasonably well: F = 90 / m, where "F" is The frequency at which it transmits 80% of the sound (reflecting 20%), and "m" = The surface Mass in kg/m2. Take that with a grain of salt, though! But it should give you a rough idea of what to expect.

In other words, for a thick, heavy panel, it reflects way down into the lower mids, whereas for a very thin, very light material it only reflects the highs.

There's another issue here too: the size of the panel. One useful rule of thumb is that an object can only affect sound waves whose wavelength is larger than the dimensions of the object. So very large objects (meters wide) can affect most of the spectrum, but very small objects (just a few cm wide) only affect highs. So even if you had a thick, heavy panel but it is only 10cm wide by 10cm high, it only affects frequencies above about 3500 Hz, since that's aprox. the frequency for a wavelength of 10cm. On the other hand, a panel 2m wide by 2m high can have an effect on everything above about 170 Hz.

So there's lots to consider here! As with most things in acoustics, the issue seems simple at first glance, but there's a whole bunch of factors to consider: sealed/not sealed, if sealed then cavity depth, hole size/spacing, panel thickness, absorption, if not sealed then panel density, width, height, flexibility, coverage percentage,.... etc.

It would be nice if acoustics where simple!

Short answer? Use pegboard on the front, unsealed, if you want to reflect back some of the highs but allow the lows through. Vary the percentage coverage to vary how much reflection you get.

Also, for rear wall bass traps, I usually try to avoid puting anything on them that is specularly reflective around ear height: just absorption, or if the room is large enough, then diffusion. Reflective surfaces can be placed higher up or lower down, but be careful around ear height: you don't want strong reflections coming back to your ears from behind you.

- Stuart -
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