so i set up my new home studio.. and at the mix position testing with an extremely flat sm81 with pink noise and a waves frequency analyze plugin i have a huge problem at 125-130hz, even generating sine wave tones i noticed the same problem audibly as opposed to graphically.. about ten db higher than the average, i built two bass traps with 703, 5" thick with a 5mm wooden cover (with two previously existing 4" think bass traps) and noticed no difference in that frequency range.. any suggestions? eq in the monitor chain? or should i really keep building bass traps for such small result?
125-130hz boost problem
- Thread starter Davidblais
- Start date
How big is your room, and how big are the traps? Unless the traps are huge, I wouldn't expect only two to make much improvement. Bass trapping - and indeed all acoustic treatment - is about surface coverage. Further, by covering the 703 rigid fiberglass with 1/4 inch plywood you effectively block higher frequency bass waves from getting into the fiberglass. It's not a bad idea to cover 703 with paper or thin cardboard to reduce absorption at mid and high frequencies, but plywood is way too thick. So the solution is more and better bass traps, rather than EQ.
--Ethan
--Ethan
A 10db "hump" sounds to me like something from your room decoration, like a big sofa not filled in or a wooden box or platform resonating. Have you tried moving the speakers upfront just for experimentation purposes and see if the boost persist?
My room is 9' high 11' wide and length wise there are two dimensions due to a closet, one half of the length is 12 and one is 16.. The two bass traps I made were 2' x 4' and 5" thick with a 5mm thick woodpanel cover, I got a 31 band eq for a monitor chain today and it helped alot but I still have a big resonance at 125hz even after a 12db cut!, but there is another peak at 100 and a big null around 80, I guess it takes alot of bass traps huh, what thickness would you recommend for 100-125hz?, also that won't absorb more at the 80hz dip will it? And yes I tried moving the monitors back and forth with no real improvement, thanks for the advice!
Your room is relatively small, which makes getting reasonably good bass that much more difficult. It takes a lot of bass traps to get a noticeable improvement and being in a small room requires taking a large percentage of space for placement of bass traps. I use 36 ASC tube traps with the majority of the traps being large bass traps in all the corners, mid wall, and the junction between wall and ceiling, and a few on the floor next to the wall. As Ethan Winer has said, one can never have enough bass trapping, and I totally agree with that statement. When dealing with the frequency range which you mentioned, ASC calls this Head End Ringing. I place 16" round and half round bass traps, floor to ceiling, behind the front speakers which helps significantly with this frequency range. Also placing speakers well away from the walls helps too. See my system and room pictures. (bwraudio)
Bruce B
WBF Founding Member, Pro Audio Production Member
In our mix room, we lost almost a 3rd of the cubic volume in bass trapping. That's how much you need!
Yes, decent traps will absorb also at 80 Hz, but I'd suggest you are looking at it the wrong way. Bass traps are more than just "passive EQ." They will make a global improvement in bass quality. At the same time, they flatten the response but perhaps more significantly, they reduce modal ringing in the time domain. Modes decay at a slower rate, muddy up the bass and make it sound artificially loud. When you add bass traps, the peaks and dips become damped and their Q is less narrow. You get a big step forward in quality. Keep in mind that in a rectangular room you have 20 corners (including tri corners). I'd call the 4 main vertical corners floor to ceiling a starting point, even better to do the 4 ceiling/wall corners as well.
In a studio, I'd think you would want more trapping than any other application, especially since it's a dedicated room that does not have to look good.
In a studio, I'd think you would want more trapping than any other application, especially since it's a dedicated room that does not have to look good.
Bruce B
WBF Founding Member, Pro Audio Production Member
More trapping than any other location?? Now that's funny! Doesn't have to look good?? That's funnier still. We pride ourselves on the aesthetics of our rooms and the acoustics are built-in, so you can't tell where the trapping is. The rooms have 50% absorption, 35% reflection and 15% diffusion, were designed by Chris Huston and the acoustics by Bob Hodas. You can't get much better than that! You only need as much trapping as called for, studio or not.
I strongly agree with Ethan in regard to EQ as it would only cause multiple other issues.
The boost you've well described is going to be a factor of your room, your speakers, their locations and your location. By process of elimination, the most adjustable elements are locations and acoustical devices.
If you would post a pic or two and an overhead diagram, it's likely that some reasonable options will present themselves.
The boost you've well described is going to be a factor of your room, your speakers, their locations and your location. By process of elimination, the most adjustable elements are locations and acoustical devices.
If you would post a pic or two and an overhead diagram, it's likely that some reasonable options will present themselves.
I would strongly advise you to at least try a parametric EQ in your monitoring chain. You WILL need to measure your room though in order to determine what the EQ should look like. Then setup the EQ then measure again to confirm it worked. There is a whole set of articles stickied on Ethan's forum about room measurement but nothing on setting up an EQ as yet. But if you are interested in that I can tell you what to do, its not that complicated a procedure as long as you have the right measuring equipment and a couple of formulas to determine the Q of the EQ filter.
IMO EQ is extremely effective at dealing with bass issues when there is only one listening seat you care about and you are trying to fix a frequency near, at or below 100Hz.
Don't think of bass trapping and EQ as an either / or. In my mind they are complimentary and you do need both, but bass traps aren't generally very effective below 100Hz or so unless you have lots and lots of them. Which of course you can do but you might not want to due to cost and / or space considerations.
IMO EQ is extremely effective at dealing with bass issues when there is only one listening seat you care about and you are trying to fix a frequency near, at or below 100Hz.
Don't think of bass trapping and EQ as an either / or. In my mind they are complimentary and you do need both, but bass traps aren't generally very effective below 100Hz or so unless you have lots and lots of them. Which of course you can do but you might not want to due to cost and / or space considerations.
That's certainly fair (Nyal's point on EQ) and worth a try. I would suggest going into the application with an expectation of a benefit at a single location (not across a larger area). At ~130Hz, you may improve the freq response but might at the same time mess with overtones 2 & 3 octaves above (a fix in the freq domain does not yield a fix in the time domain).
Very well stated Nyal on not being an either/or proposition.
Nyal, what EQ would you suggest?
Very well stated Nyal on not being an either/or proposition.
Nyal, what EQ would you suggest?
Bruce B
WBF Founding Member, Pro Audio Production Member
This is the same thing that Bob Hodas recommends when problems can't be fixed by acoustics. Of coarse, Bob uses the Meyer Sound Labs EQ's, but any "good quality" EQ should work.
I would use a software plugin in your recording / mastering software. If you are Mac OSX there is a free Apple provided parametric EQ that you can use (it is an Audio Unit). Not sure on the free options on PC. Some of the EQs I have used include FabFilter, Flux Epure. FabFilter has a 15 day no limits free trial I think.
Oh Jeff, I would be interested in your opinion on Floyd Toole's assertion relative to fixing time domain by fixing frequency domain:
Floyd Toole states: “Room resonances at low frequencies behave as “minimum phase” phenomena, and so, if the amplitude vs. frequency characteristic is corrected, so also will the phase vs. frequency characteristic. If both amplitude and phase responses are fixed, then it must be true that the transient response must be fixed – i.e. the ringing, or overhang, must be eliminated” (Toole, The Acoustical Design Of Home Theaters, 1999). The paper contains measured evidence of the efficacy of magnitude based equalization in reducing time domain ringing (see Fig 3, Pg 8 in particular).
Ethan and I had a debate on this over on audiocircle, not sure on what you thinking is on this?
Floyd Toole states: “Room resonances at low frequencies behave as “minimum phase” phenomena, and so, if the amplitude vs. frequency characteristic is corrected, so also will the phase vs. frequency characteristic. If both amplitude and phase responses are fixed, then it must be true that the transient response must be fixed – i.e. the ringing, or overhang, must be eliminated” (Toole, The Acoustical Design Of Home Theaters, 1999). The paper contains measured evidence of the efficacy of magnitude based equalization in reducing time domain ringing (see Fig 3, Pg 8 in particular).
Ethan and I had a debate on this over on audiocircle, not sure on what you thinking is on this?
Bruce B
WBF Founding Member, Pro Audio Production Member
Thanks Nyal, but our rooms don't need any EQ. We do on occasion use software EQ on problem mixes when the hardware (Millennia, Neve, Weiss and TC Electronic) won't do for our clients. We also use Flux, Sonnox and Algorithmix.
Nyal,
Very glad to comment. I think the KEY qualifier is what is a minimum phase event or non-minimum phase event. In simplest terms to me: the more an event is heard/measured consistently throughout the space, then the more likely it is minimum phase and EQ can be successful (yielding an accurate reproduction of input). The more an event is heard/measured with obvious deviations throughout the room it is non-minimum phase. In that case, EQ is not going to "fix" what is happening in the time domain= less accurate reproduction.
Of course, Bruce's quote from Bob Hodas says the same much simpler.
At 125Hz-130Hz, my first take would be to look at possible small changes in speaker locations or listening location. Maybe the 10dB issue can be brought down a few dB and then EQ. Those are two non-invasive options.
Very glad to comment. I think the KEY qualifier is what is a minimum phase event or non-minimum phase event. In simplest terms to me: the more an event is heard/measured consistently throughout the space, then the more likely it is minimum phase and EQ can be successful (yielding an accurate reproduction of input). The more an event is heard/measured with obvious deviations throughout the room it is non-minimum phase. In that case, EQ is not going to "fix" what is happening in the time domain= less accurate reproduction.
Of course, Bruce's quote from Bob Hodas says the same much simpler.
At 125Hz-130Hz, my first take would be to look at possible small changes in speaker locations or listening location. Maybe the 10dB issue can be brought down a few dB and then EQ. Those are two non-invasive options.
That's a good way to look at it. Of course, we know that the LF response in domestic size rooms varies all over the place. And my own measurements at multiple location with two separates tests in two separate rooms confirms that EQ always makes things worse somewhere else. That said, I'm not opposed to a modest amount of cut at the one or two worst peak (only) frequencies.
--Ethan
Hey Bruce, I was meant to direct that at Jeff, since he asked what EQ could be used. Sorry if you thought I meant your rooms needed EQ!
Thanks for your response.
I don't know if you have been keeping up with what John (author of REQ Wizard) has been doing on Room EQ Wizard but in v.5 he has put together an algorithm that attempts to correct room modes. His thinking behind the correction algorithm as here is an interesting read.
Nyal,
THANK YOU...100% support John's updates. I had actually blown off the REW update notice putting it in the "I'll do that soon enough" category. I will now update right away.
Ironically, I just last week used the Group Delay to determine secondary space cause/effect of a gentleman's room: having data from each speaker individually and both, the Group Delay shows clearly these issues. The relationship of the Group Delay from V.4 had me thinking of how to properly apply EQ. John is a leader.
Very exciting.
THANK YOU...100% support John's updates. I had actually blown off the REW update notice putting it in the "I'll do that soon enough" category. I will now update right away.
Ironically, I just last week used the Group Delay to determine secondary space cause/effect of a gentleman's room: having data from each speaker individually and both, the Group Delay shows clearly these issues. The relationship of the Group Delay from V.4 had me thinking of how to properly apply EQ. John is a leader.
Very exciting.
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