Bass traps and other room treatments

tomlinmgt

Moderator
Have you considered getting a digital room correction unit of some type for the subs? I went all in with floor to ceiling bass traps ("superchunk" style using OC703) in all corners and though that did tighten up LF content a good bit, it did virtually nothing to smooth out the peaks the room's dimensions were creating...so I was still plagued with nasty spikes at several points along the response curve. My silver bullet to eliminate the peaks was a DSpeaker Anti-mode 8033. G-damn thing was a game-changing life saver. The methodology is as follows...locate the subs where they get maximum room loading (typically in corners) and then let the digital filter shave down the peaky frequencies (determined after the unit listens to the room's response and decay characteristics with its own microphone...not unlike Audyssey but with better processing or algorithms or whatever). I simply won't use a sub(s) without one, and strongly recommend getting one in any hifi system that uses a sub or subs before you tackle the bass traps thing...which is a helluva lot of work. You can get control of mid and upper bass energy without going full monty floor to ceiling bass traps...thick corner traps can do the trick. And I definitely encourage doing something to remove the boom or overhang in that spectral region aa doing so really does wonders for the overall presentation from top to bottom...so I consider it pretty critical in a serious room tuning scenario.

As far as your first reflection locations and your furnishings creating an obstruction for the installation of any absorption panels (or diffusion if you're so inclined...or if you're really nasty, a mix of the two) I like portable panels as a solution to that pickle. Easy to make and particularly useful when experimenting with sitting position location, speaker placement, experimentation with location of acoustic treatment devices, etc. And it's easy to make any panel portable...a few different ways to skin that cat.

So, what kind of response do you get when you walk around the room and do a clap test? You hear many or any "zings", "pings" or any other goofiness? I'm betting not many...if any at all...with all of those non-parallel, opposing surfaces and carpet.

Michael
 
Last edited:

MWalt

Active Member
Mike, I have seen pics of your listening room and it is amazing! That said, the room I have now is surprisingly good without treatment, but I do know that I have bass modes that can be addressed. What do you suggest for me to use as far as digital correction? This is an area I have ZERO experience with so any guidance is much appreciated.

Mark
 

tomlinmgt

Moderator
Thanks for the kind words, Mark. I use the DSpeaker unit I mentioned earlier. I have three of them now...one in the living room system with two SVS 12" sealed subs (both in the same corner) and one in the garage rig with a pair of DIY 12" sealed subs in stereo (that's the system you've seen pictures of). Both of those units are the 8033s ii. About six years ago I was at Lone Star Audio Fest talking to a dude about my early trials with distributed bass and he was very enthusiastically recommending the Anti-mode. So a few months later I got my hands on a used 8033 Cinema and became an instant proponent of the technology. Shortly after, I went to the 8033s ii because it's designed to work with OB subs (which I was playing with at one time) as well as conventional box subs, and does correction over a broader spectral range. Just this past week I loaned the 8033 Cinema to a friend who has been trying to integrate a Rythmik sub with his Acoustats (my old Spectra 22's). He's been struggling with it for a while but finally found a spot in his room he was pleased with. I knew he could do better with DRC filtering, so I suggested (well, insisted) he try the 8033 Cinema I had sitting on the shelf. He was floored with the results. Another instant convert. LOL About a year ago I saw that Parts Express had come out with a DRC unit of their own and that it had a lot of features the DSpeaker units don't (such as app that gives you control from your hand held device and a PEQ) and, perhaps the best part, that's it's dirt cheap. My friend ordered one right away. I'll let you know how his experience with it plays out.

Michael

 

MWalt

Active Member
That looks promising. I could potentially use it with my second string amp (NAD C356bee) because it has a pre out, but not with my primary amp (Primaluna Prologue Classic) for which I have to use low level speaker leads to both subs. I will wait patiently for your feedback on it.
 
Last edited:

tomlinmgt

Moderator
Ok...feedback from my friend on the Dayton DSP/DRC unit is positive. He said it took a bit to figure out how to use all the features (UI not all that great), but once he did he was very pleased with the results.
 
Her is a question for those above my mental capicity .
I have been searching some of the web writings on acoustic treatment trying find out how to treat for a null.
I have a dip in the 250 hz range that has always showed up when measured as long I have been living in this house.
Any ideas or links to papers about how to deal with a "suck out"?
I would think difusion might be the answer but I dont know if can be effective with lower frequency.

Is your listening chair centered between the two side walls? If so, and especially if your room is a rectangular box, you will have a null point at that spot centered between the side walls. You may find a better bass balance if you move the chair about 1.5’ towards one of the side walls, and move the two speakers the same distance towards the same side wall.

I had precisely this problem in my old room. This was during my Dark Years when I had Thiel speakers and a Classe solid state amp. They were lean to begin with and the centered listening chair made the problem much worse.
 

MrEd

Senior Nobody
Is your listening chair centered between the two side walls? If so, and especially if your room is a rectangular box, you will have a null point at that spot centered between the side walls. You may find a better bass balance if you move the chair about 1.5’ towards one of the side walls, and move the two speakers the same distance towards the same side wall.

I had precisely this problem in my old room. This was during my Dark Years when I had Thiel speakers and a Classe solid state amp. They were lean to begin with and the centered listening chair made the problem much worse.
Yes... center of the room.
Your observations concur with mine.
My room is small so not a lot of options, especially with A5's they have to live pretty close to the walls . I have a sofa and often sit to one side and not in the sweet spot.
 
Totally agree with @Hifi Speaker placement is critical and if the room alows definitly experiemnt.
Here is a good link for building diffusors.
The links on the website for downloading plans don't work. Do you have any plans you could post or send me directly instead?
 

MrEd

Senior Nobody

Try1256

Very Special Member
I have a difficult room. 13'6'x10'x9' My speakers are on the long wall. I have 4 - 2'x2' corner traps at the ceiling and 1- Stillpoints Aperture on the front wall. Sounds so much better than it should. The Aperture is an incredible piece. Replaced several other panels and the room sounds much better than it ever has.
 
This one I have saved.
This is from diy audio
Thanks for posting these links. Lots of interesting options. I will put DIY Diffusers on my 2021 Projects lust.
 

MrEd

Senior Nobody
So.... back to bass nodes .
I moved my seating forward a bit and changed the angle of the speakers.
Helped with bass. Have not measured but to the ear better.
Been listening for two days now and realized that now my brain is locating the speakers.
Before they pretty much diaspered into the sound stage.
 
Concerning where and with what treatment to start with, I'd recommend bass traps as your first concern. Without handling those problem frequencies below 100hz, their harmonics will distort/cloud/color the higher bands.
Here are a couple sites that deal with room modes and speaker location:



First discovering the rooms inherent freq modes, then finding the proper speaker placement, then then sub placement and then voicing the room.
Finding your speaker placement will take much time but very worthwhile. For the sub, get it out of the corner and maybe put it where your listening chair will be. Play music with good base tunes yhat you know very well and walk around the room to locate where the sub sounds the best to you. That will be where you place the sub and don't be bashfull, try elevating it as well.
Concerning voicing the room, you'll find the strongest modes are between parallel walls; axial modes. Without getting too complicated or expensive, you can tape a sheet of paper on the wall every 3' and have printed on them frequencies starting at 30, 40, 50 etc up to 100hz. one column at 75 spl db and another at 85 spl db.
with an spl meter at your listening position, ear high, play a 100hz signal and adjust volume to 75 spl db. You can download a frequency generator app for free on you phone. feed that signal to your pre-amps line level input using a cable with a 3.5m jack for the phone and RCA for the pre-amp. Start at 30hz without changing the volume, walk around the perimeter wall. facing the wall measure the spl level pointed at the wall for that frequency and write it down. do all around and then advance to 40hz and start over until you reach 100hz. Adjust your volume now for 85 spl db like you did for 75 spl db. and start anew brginning at 30hz again.
Graph it out manually or in a spreadsheet and youll have your low frequency problems identified and where they are in the room. Now you can research what type of treatment can deal with those frequency peaks or attenuations that you logged.
You most probably will see a difference of +/- 15 spl db from the original setting of 75 spl db. An equalizer will never fix that, only room treatment. For low end absorbtion, 4'' or 12'' of roxwool will never do it. You'll need mass and lots of it. Diaphragmatic absorption will have the highest horsepower.
 

Olson_jr

Active Member
@Frank A

The graph paper procedure seems an Interesting method. I have an oddly shaped room, with one long wall having a fireplace and 3-4 different distances to the other sidewall. The rear wall also has 2 different distances to the front.

I have been playing around with some of the room mode calculators, but none that I have found allow for the unusual shape of the room. I have fudged some numbers to try to get the room volume close to what I believe is correct.

REW has a room simulation tab that I find interesting. When I set it up it seems to correlate with what I believe I am hearing in my room, bass-wise at least.

Hope to learn a bit more about my room, speaker position, and bass control this winter.

Screen Shot 2021-11-26 at 10.35.07 AM.png
 
Top