Subwoofer Frequency Response question
A 10db peak is not uncommon at all, you could eq that down. Peaks are better than nulls, you can't eq a null up and out. Some subwoofers (they call them hometheater subwoofers), do indeed have built-in bass peak, I don't know anything about your sub though. At any rate...you could eq that out too. Dave |
Most bass traps I've seen are designed to reduce peaks at 80hz upward though some provide a little boost at 50ish hz (bass busters). You can eq nulls, but it's not easy for a 20 db problem, I'd guess you might get some improvement via PEq, but not a full fix. I would have seconded Eldartford's recommendation, but it seems from your post that you've already tried that with no success. I use a Velodyne SMS-1 x-over, analyzer, and PEq unit that is fantastic, but in your case I'm not sure what will help. Marty |
It could simply be room modal - this will not go away no matter where you place the sub. Your only hope would be to add plenty of bass traps and EQ down the peaks to make the trough relatively less big. It also may be caused by your speakers - as the bass is omnidirectional it will reflect off the wall behind the speakers. You get quarter wave cancellation across the entire room. Are your speakers on when you make this test? Or is it just the sub playing? Just in case - perhaps I should explain what you should do with speakers... You should try to avoid middle ground - either place your speakers within 1 M of a wall or more than 2.2 M to help reduce this problem. there are formulas to work out at what frequency you will get cancellation - remember this applies to the ENTIRE room. I put my large full range speakers into a soffit mount - only this way you can completely eliminate the problem - that is what studios do. I leave my surround satellites within two feet from the wall (they roll off at 60 Hz). I quote from Genelec For large loudspeakers, with very The cancellation frequency is Fc = C / 4 * D. D= Distance from front baffle of speaker to rear wall behind speaker. C= 344 Meters/sec Fc is in Hz. In your case a suckout at 45 Hz equates to a Distance of 1.9 meters. And 70 Hz equates to a distance of 1.2 Meters. If your Europa speakers are in between these two limits then it could well explain your problem. Typically this yields a 20 db suckout. Most people have this problem as they use large full range free standing speakers. Since most people ignore it - even a 20 db suckout - as bad as it seems - is it not likely to ruin your enjoyment of music. Sometimes other room modes can compensate at the listening position. Hopefully you can see that speaker position can be important too - not just the sub. |
Sharome, That is one very handy bit of info. It implies that there will always be an Fc, which can be raised as we place the speaker closer to the rear wall and lowered as we move it away. However, it leads to 2 questions: First question: If the cancellation frequency is -round numbers- 90 divided by Baffle to wall (in meters), does the size of the suckout change predictably as Fc changes. That is, if we move a speaker to 2m out from its original position 1m from the front wall and Fc drops from app 90hz to app 45hz, have we reduced the magnitude of the problem or merely shifted it downward? If the latter, then is the idea simply to move the speaker so far out (the recommended 5m equates to app 18hz)that the suckout is below the range of the speaker's output? Conversely, is the idea behind <1m to keep the suckout in the same region as bass peaks in a typical room? Given the variation in peaks from room to room, this strikes me as quite a risky approach. (I see why you like the soffeted approach.) Second question: Which baffle? In a Mains/Subs set up, you will likely have 2 different Baffle to front wall distances. Do you know how to determine which is relevant (or in what ratio relevance can be determined) to the calculation? Is the crossover point relevant in making this determination? Does staggering the Baffle to wall distance create 2 problems equal in magnitude or 2 problems smaller in magnitude than the original? I guess that's more than 2 questions Thanks in advance. Marty Marty |
