Helmholtz resonator and room modes

miroslav said:
Are you doing measurements with or without the sub?
Also, are you doing measurements at the mix position or somewhere else?
And...are you measuring one side/speaker at a time or both together?

The other thing...as I said earlier...did you consider moving your speaker toward/ and even up against the front wall...along with moving your mix position.
You appear to be sitting in the center of a small room...not really good. I know some common wisdom is to have the speakers as far away from the front wall as possible...but that would really apply IF you have the big enough space. The other options is to move them right up against that front wall, and you may see some of your nodes disappear. You have to try a variety of positions for the speakers and your mixing position...along with moving the trapping to different areas of the room and measuring.
You also have to measure the same way, the same level every tine. Have you calibrated you measurement level and speaker loudness for a single reference level?
Click to expand...

I'm doing the measurements with the sub and in the mix position. One side at a time and both speakers together, no difference. Tried moving the sub and moving the speakers towards the walls, fixed the nodes but made the modes worse...
Would hire a professional acoustician but I live in a small town in Croatia, no such thing here...
Starting to feel a bit desperate... :(
 
MagashMusic said:
...fixed the nodes but made the modes worse...
Click to expand...

I think you mean peaks and nulls... so what got better, and what got worse?

What Are Room Modes

Room Acoustics Primer

Basics of Room Setup

Should You Use A Sub In Your Home Studio Monitor System?

Tech Tip Of The Day: Studio Subwoofer Placement - ProSoundWeb


You don't need to measure the speakers together. You only want to only do one side at a time.
Are you calibrating your monitor level and using that same level for all you measurements?

Have you tried doing measurements without the sub? I think that sub may be adding to your problems.
I would get the room set up without the sub...and then add it and see what it does, and how it changes things. Then place it where it works best.
You don't have unlimited options with a small room. The sub may be too much for it if you push it too hard.
Set up the sub so it only extends your low end...but not to make it louder.


MagashMusic said:
... I live in a small town in Croatia...
Click to expand...

Zdravo
 
Last edited:
Just reading through this thread reminded me of a similar problem I had in my old studio about 20 years ago. We had a problem around 40Hz in the recording room. I had my tech over who had built a few studios over the years and the comment was to trap the 40Hz we would need to build a bass trap the size of the room LOL. So we tackled it a bit different, instead of aiming at the 40 Hz we aimed to heavily trap around 120Hz. 120Hz is a multiplier or relative frequency (hope thats the right term) to 40Hz, by reducing the 120Hz the problems with the 40 will be reduced, and it is much easier to reduce 120Hz than 40Hz. I have used a similar approach to my current studio and we have no bass problem at all.

By the way I use this often when using a graphic EQ in a live venue mixing situation, reducing say 800hz when the problem could be 400Hz but I don't want to pull out all the 400Hz, so reducing both the 800Hz and 400Hz by a smaller amount. I often tell younger sound guys about this when I see that they have pulled a frequency right out and effectively lost vocal clarity, pull that frequency out less and pull 1 or 2 of the relative frequencies out a little also. Sorry to get side tracked there but I was pointing out my theory.

Ready to be shot down in flames now LOL
Alan.
 
Not sure about the port...but with a sub in general (and I don't know what size sub the OP has)...in a small room, placement will be difficult, because I think you would just be moving all the nulls and peaks around. IOW, placement will be almost meaningless with regard to finding a spot that really improves things...only changing.

I've kicked the sub idea around a few times...and my space is bigger than the OPs, and not a perfect box like he has, which is a bitch with creating room modes...but I always walk away from the sub idea. Just not seeing a real need for it, unless I start doing EDM or Hip Hop. :D

If the sub crossover point is 80Hz or lower...the wisdom says placement is not all that critical, you just find a spot where you think it sounds best....but the level can be a problem, if people over do it because they want to feel the rumble. It should just add a smooth extension to the lows...without adding obvious loudness.
 
miroslav said:
Zdravo
Click to expand...

Zdravo! Kad sam ti pročitao ime sam pomislio da bi i ti trebao biti tu negdje... :)

Tnx for the links, I'll see if I can find some usefull information there. I try to keep the measuring consistent but also I tried measuring at different levels and the only thing that changes is the amplitude, but the modes (peaks) are still there at the same frequencies... Also tried to move the sub, no luck. I also tried lowering the sub, then the graph looked similar to the one I uploaded but the low end below the crossover frequency was quieter, but same shape. I need the sub because I do a lot of mixing below 80Hz... Bass guitar is 40Hz, the bass I often use for recordings goes to 30Hz (low B string on a 5 string) and I do some cinematic stuff (drops, explosions etc...) And I tried moving the resonator around and no luck...
 
witzendoz said:
By the way I use this often when using a graphic EQ in a live venue mixing situation, reducing say 800hz when the problem could be 400Hz but I don't want to pull out all the 400Hz, so reducing both the 800Hz and 400Hz by a smaller amount.

Ready to be shot down in flames now LOL
Alan.
Click to expand...

Haha, I'm not trying to shoot you down in flames but doesn't that theory apply only for the upper harmonics..? That's why I was fixated on the ~38Hz problem because I thought that if I eliminate it i would also eliminate its upper harmonic ~76Hz... I think It doesn't work the other way around...
Please someone correct me If I am wrong...
Btw, the sub I use is 8'', max spl 103dB and goes down to 30Hz -3dB.
 
MagashMusic said:
Haha, I'm not trying to shoot you down in flames but doesn't that theory apply only for the upper harmonics..? That's why I was fixated on the ~38Hz problem because I thought that if I eliminate it i would also eliminate its upper harmonic ~76Hz... I think It doesn't work the other way around...
Please someone correct me If I am wrong...
Btw, the sub I use is 8'', max spl 103dB and goes down to 30Hz -3dB.
Click to expand...

My own feelings and results are that attacking the 76hz would also attack the 38hz to some degree, I also agree that attacking the lowest frequency would obtain better results but as I said attacking the lowest frequency is also a lot more difficult and requires a much larger bass trap.

Alan.
 
I am not a guru in any way as far as room treatment goes. I have just been lucky enough to have a couple large rooms and two smaller that work well for recording/mixing with the standard type of acoustic treatment for the most part. I also have been blessed with advice from JH Brandt that showed me the correct way to make the best of what I have.

That being said, have you looked at John's site? LINK There is much information there. I am not sure a room of your size will actually benefit from a helmholtz resonator. Seems the room modes would require a resonator in every corner. I don't know. But small rooms also do not benefit from diffusion things either.. Every room is different and it takes some dealing with what you have and using your ears to adjust for the 'non perfect' size.

I personally wouldn't worry so much about REW measurements. Seems you have taken care of most of the bad things acoustically. Props to ya! Use your ears to make the mixes sound the way you want them to.
 
jimmys69 said:
I personally wouldn't worry so much about REW measurements.
Click to expand...

I agree.

It's OK to do some and then make some changes and what not, and see if/what is different....but if you try to chase REW measurements, it will just make you nuts. I bet many commercially treated rooms have some weird REW measurements...and I doubt any have something even close to a flat-line response curve.

Bottom line...small room....stuff the shut out of it...and then go back to making music. Learn what the problems are, and work with and around them.
Now if your mixes always translate very poorly across other playback systems after that...then you just need to find a better (and bigger room) to work with.
 
Square room is the biggest problem here unfortunately. My control room is only 3.8 mtrs wide and roughly 6 mtrs long, with the bass trapping there are no problems with the bass at all.

I actually planed the control room size around the building restraints and by picking a golden ratio, 1.00 x 1.50 x 2.50. I know everyone does not have the luxury of building a room the size they want but unfortunately it's a fact that a square room is one of the worst rations you can have and there will always be a compromise.

Alan.

Acoustics_July_GoldenRatios-1.jpg
 
I was recommended- and almost broke up my mixing room to get the best dimensions, but I just couldn't bring myself to do it in my situation.

I like the large/long room even if the modes fuck with me half way back. I don't care. It works for mixing in the front 15' of space where my desk is. That is treated with fluffy pink stuff as I was advised. Rockwool bass traps in the corners blah blah...

Vocals midway through the room with a 'v' shaped hanging of 4" thick panels just works.

The end result is that I know what I am hearing. I have monitor speakers that do not lie to me (well they don't seem to). And I have the experience with them that allows me to make such judgments about my room.

Fuck what the results from measurements tell you. No room is perfect. We do what we do with the knowing of how it sounds. If it works, then it works...
 
I've been reading a lot of online articles and research papers about Heimholtz Resonators and one thing that kept coming up in the experimental studies was that the resonators they built always had to be tested impirically to determine the actual resonance, and then adjusted, by changing the volume or size/lenth of the port/neck on the resonator. And, of course, any change of volume changes the resonance, so adding rockwool is not just increasing the damping, it's changing the frequency.

So, to have any hope of something like that actually making a difference, you need to be measuring it with something like a sine wave generator and a microphone inside the box to figure out what frequencies really get sucked into that thing. Once you've made adjustments to tune it to the frequency you're trying to affect, then you can see whether it makes a difference.

Some studies were inconclusive. One in particular had some small resonators built as monitor stands, and it only succeeded in moving the room resonance to some point between the lowest and next harmonic. (I don't know if that would be considered a success, but it wasn't the hoped-for outcome.)
 
Some years ago Keith I helped a mate build the Mother of all subs. Fridge-freezer sized and 4 12" car woofers.

Not having mics mixer and certainly not PC recording! I taped a bit of tissue (aka bog paper) across the port and tuned for maximum flap.

If you read the T/Small design notes for reflex speakers they tell us to design for at least 20% over size then kludge it a bit!

Dave.
 
In the end it really just comes down to how your mixes come across as your ears tell you... You mix as good as you can because of your ability to do it well in the room you have and the quality of monitors you are working with.

Unless you build a perfect room which is as I hear is not really actually possible, then you make decisions based on what you have and hear.

I wouldn't get anything done if I spent time stressed about frequency response in my room. Granted I have a shitload of room treatment. But I know what I hear in my room and have learned to deal with what it tells me.

I suggest just doing what you do with what you have, and not trying to over-fix a room that is what it is.
 
jimmys69 said:
In the end it really just comes down to how your mixes come across as your ears tell you... You mix as good as you can because of your ability to do it well in the room you have and the quality of monitors you are working with.

Unless you build a perfect room which is as I hear is not really actually possible, then you make decisions based on what you have and hear.

I wouldn't get anything done if I spent time stressed about frequency response in my room. Granted I have a shitload of room treatment. But I know what I hear in my room and have learned to deal with what it tells me.

I suggest just doing what you do with what you have, and not trying to over-fix a room that is what it is.
Click to expand...

It's just so frustrating that the bass sounds too muddy in mya room and I have to mix the song by adding even more bass so it can translate well, It's a pain working like that...
 
keith.rogers said:
I've been reading a lot of online articles and research papers about Heimholtz Resonators and one thing that kept coming up in the experimental studies was that the resonators they built always had to be tested impirically to determine the actual resonance, and then adjusted, by changing the volume or size/lenth of the port/neck on the resonator. And, of course, any change of volume changes the resonance, so adding rockwool is not just increasing the damping, it's changing the frequency.

So, to have any hope of something like that actually making a difference, you need to be measuring it with something like a sine wave generator and a microphone inside the box to figure out what frequencies really get sucked into that thing. Once you've made adjustments to tune it to the frequency you're trying to affect, then you can see whether it makes a difference.

Some studies were inconclusive. One in particular had some small resonators built as monitor stands, and it only succeeded in moving the room resonance to some point between the lowest and next harmonic. (I don't know if that would be considered a success, but it wasn't the hoped-for outcome.)
Click to expand...

When I built the resonator it was just a sealed box. Then I drilled a small hole, then gradually made it bigger untill I hit the calculated dimensions meanwhile, I made measurements after each hole enlargement and saw nothing in the graph. The theory says that I should have been changing the frequency and thus the graph should have shown it...
What am I doing wrong..?
 
MagashMusic said:
When I built the resonator it was just a sealed box. Then I drilled a small hole, then gradually made it bigger untill I hit the calculated dimensions meanwhile, I made measurements after each hole enlargement and saw nothing in the graph. The theory says that I should have been changing the frequency and thus the graph should have shown it...
What am I doing wrong..?
Click to expand...
Well, like I said, it seems like the theory is just that. You need to actually know the resonance of your box to decide what to look for, and then adjust from there to get to the frequency you're trying to impact.

But, honestly, I'm still trying to understand how your resonator box, which I guess is about .75m on a side, if it's a cube, is going to impact a room's sound pressure in any meaningful way. I mean, if I take a a hundred or so 2L empty wine jugs, with a resonant frequency of 60Hz, and place them around the walls of my room, do you think I'll see a significant drop in the room's frequency response at 60Hz? I don't, but if someone wants to send me the wine, I'm willing to take on the challenge and issue a report :).
 
keith.rogers said:
I mean, if I take a a hundred or so 2L empty wine jugs, with a resonant frequency of 60Hz, and place them around the walls of my room, do you think I'll see a significant drop in the room's frequency response at 60Hz? I don't, but if someone wants to send me the wine, I'm willing to take on the challenge and issue a report :).
Click to expand...

I was thinking the same thing with empty beer cans, if someone wants to send the beer :drunk:

Alan.
 
keith.rogers said:
Well, like I said, it seems like the theory is just that. You need to actually know the resonance of your box to decide what to look for, and then adjust from there to get to the frequency you're trying to impact.

But, honestly, I'm still trying to understand how your resonator box, which I guess is about .75m on a side, if it's a cube, is going to impact a room's sound pressure in any meaningful way. I mean, if I take a a hundred or so 2L empty wine jugs, with a resonant frequency of 60Hz, and place them around the walls of my room, do you think I'll see a significant drop in the room's frequency response at 60Hz? I don't, but if someone wants to send me the wine, I'm willing to take on the challenge and issue a report :).
Click to expand...

The box is 1.52mx0.54mx0.52m And you're right, that box is about 100 times smaller than the room. I always wondered how it could ever imact the room response but the internet is full of people claiming (even graphs proving it) that they got a difference of 6-10dB...
Btw, I'm more of a whiskey kinda guy ;)
 
You must log in or register to reply here.
Back
Top