Large speaker improvements

[QuadDiffuser]

Here’s a review of the latest generation bearing/footers, engineered and machined to exquisite perfection and precision:
https://6moons.com/audioreview_articles/hifistay3/

 

[sbnx]

Steve, which crossover is that? I searched GP acoustics but nothing obvious showed up except the KEF importer.

 

[fuscobal]

If i might ask where you live as i see steve invited you over

If the question is for me, I'm from Romania

Only ¨ problem ¨ i see with the room is the opening in the right corner , i believe you close this with a curtain .
If you put a solid door there , you have more pressure build up in the room

Yes, I know that large opening is a problem. I've put a curtain to at least stop higher frequencies from going to the hall and back. Can't close it with a door but maybe put a large absorber to close half of it. Do you think this would help ?

 

[sbnx]

Oh, then I guess I can't just drop by for a visit and a listen since I am in the US.

Try building a couple of the large bass traps and place them at point of first reflection, Then in the opening to the hall and see what seems to make the largest impact on the sound. Unfortunately, I have discovered that all you have to do to know where to put a large absorber is to look at your room and ask yourself "where is the most visually obtrusive spot that I could put acoustic treatment?"

 

[andromedaaudio]

If the question is for me, I'm from Romania


Yes, I know that large opening is a problem. I've put a curtain to at least stop higher frequencies from going to the hall and back. Can't close it with a door but maybe put a large absorber to close half of it. Do you think this would help ?

I dont know, maybe if its a solidly made absorber and it would close much of the opening it would help

 

[fuscobal]

I'll try to build some of variuous widths (15-30cm) and play with them to see what happens. Maybe the room not being pressurized does still some of the energy !

 

[fuscobal]

 

[sbnx]

Real traps uses Owens Corning 703 compressed fiberglass. This is the "old" way of thinking. The 703 or 705 does work well at below 4" (10cm) but for thicker traps fluffy insulation works best.

I attached a pic of the graphs for comparison. you can see that 10cm of 705 beats out 10cm of fluffy below 300 Hz (which is where it really counts). But looking at 30cm you can see how (way) much more absorption there is all the way down to 30Hz.

 

[fuscobal]

Do you have a link for this fluffy insulation ? Trying to identify the name in my country (if it exists at all).

 

[sbnx]

There are a lot of companies that sell what I am calling "fluffy" insulation. You can use rolls of R13 or R19 insulation. Owens-Corning is the big name brand and is pink fiberglass. Just get the "unfaced". Use a facemask, gloves and safety glasses when working with it. To make it:

1. use MDF or Baltic birch ply (1/2" thick is fine) to make a 4 sided box that is the depth you want -- 12"
2. Cut a few narrow (1 to 1 1/2 inch) as cross braces. I typically use 1 per foot of length. this adds stability to the box.
3. use "poly fill" or some other similar thing on each side to make sure the fiberglass fibers stay in th box.
4. Cover the outside of the box with "acoustic fabric".

Hope this helps.

 

[QuadDiffuser]

Fiberglass insulation does not “trap” long-wavelength (ex. 33Hz bass has a wavelength of 33 feet) air pressure generated by low bass:

 

[fuscobal]

Yes, I know the theory. For a certain frequency you'd need 1/4th of it's wavelength in the bass trap which equals several meters ! As for the fiberglass, we don't have Owen's around here but Knauf and Isover (ridgid boards and rolls). Rolls have less density and are not stable physically so they need to be contained in a frame. Might as well buy a Dayton mic and use the Macbook + REW software to see the room's frequency response.

 

[sbnx]

Fuscobal, Knauf works fine. As I mentioned use the fluffy not the hardboard. Yes, you will have to construct a frame as I mentioned in my earlier post to "contain" it.

Getting a mic and installing REW will definitely show you specifically what frequency the issue is occurring.

And in response to quadfuser -- fluffy will absorb, it just has to be thick. Fuscobal is not trying to absorb 30Hz. He is needs to absorb in the 80Hz range. As I mentioned 12" will get about 60-70% of it. There is no other way to deal with SBIR dips. (Except using subwoofers)

 

[tkoslek]

One old trick that works well (but will be awkward given the size and weight of your speakers) is to place one at your primary seating position and then, while music is playing, crawl/walk around the front of the room until you find the place that sounds the best to you. You then place your speaker there. It isn't a perfect process, but it does work.

 

[fuscobal]

Played with this calculator today after moving the bass traps and absorbers a bit with no improvement. Distance from wall was 205cm and it seems there was a null there. Moved the speakers 20cm closer to me @ 225cm from the wall behind them and sound became much more linear with bass and midbass catching up and showing some energy. 1st pic shows a dip at 50-60Hz. On the second pic, the dip was smoothed. Problem was, theory was telling me this a long time ago but left the speakers closer to the wall because the right one is now right in the middle of the entrance in the room

 

[sbnx]

Glad to hear you have smoother bass by adjusting your speakers. similar to my other post...It always seems that where you don't want something to go is exactly where it has to go to sound best.

Modeling and theory is great and can steer you in the right direction. But once you start measuring you can see exactly where you want to go and the impact of everything with ease. Of course, your ears are the final judge but in the bass region I have found that a flatter frequency response always sounds better to me.

 

[fuscobal]

Well, at 300cm the graph is perfectly smooth but I'd also have to take out my furniture ))

 

[QuadDiffuser]

Fuscobal, Knauf works fine. As I mentioned use the fluffy not the hardboard. Yes, you will have to construct a frame as I mentioned in my earlier post to "contain" it.

Getting a mic and installing REW will definitely show you specifically what frequency the issue is occurring.

And in response to quadfuser -- fluffy will absorb, it just has to be thick. Fuscobal is not trying to absorb 30Hz. He is needs to absorb in the 80Hz range. As I mentioned 12" will get about 60-70% of it. There is no other way to deal with SBIR dips. (Except using subwoofers)

The wavelength of a 80Hz wave is 14 feet. It’s not about diffracting 80Hz with 3.5 ft. deep wells in a quadratic diffusor, but rather about absorbing the air pressure and flattening the undesirable constructive and destructive dips and peaks, right?
Insulation material absorbing bass is a myth; 12” will likely absorb less than 10% of the air pressure. Either an active bass absorber (like the PSY Audio AVAA) or a passive diaphragmatic absorber utilizing activated carbon and sympathetic resonance is required to answer any questions! ;-)

 

[QuadDiffuser]

Here’s the thread on the AVAAs which I started; I have four units in my setup.
https://www.whatsbestforum.com/threads/psi-audio-avaa-c20-active-bass-absorber.26122/

 

[QuadDiffuser]

This video’s pretty old, but there are other linked videos which add to the info: