Danny Danzi

Dean, can't that 67 Hz cancellation be cured with an eq?
-Danny

No, unfortunately cancellations can't be cured by EQ. The issue is that, if you have a peak, then basically it's two waves adding together at a particular frequency. You can EQ that down (though you may not be able to EQ that big a peak in some cases) because you are just lowering the overly high combined waves. If you cut the energy of the wave going out at that energy, then the lower energy outgoing and reflected waves add up to a lower over all level.
 
With a cancellation they are cancelling each other out. If you push up the EQ, they still cancel each other out. If you lower it they still cancel each other out. So you can only deal with cancellations by preventing the signal from reflecting back to the listening position. That's generally done with traps that are broadband, meaning they suck up a wide range of frequencies. You don't want really any strong bass energy getting back to you from the walls if you can avoid it anyway, so if it sucks up other frequencies besides the ones you have trouble with, that's all good, too. And generally you have problems with more than one frequency anyway.
 
If you can't do it sufficiently with broadband absorption you would have to use a tuned trap that's able to suck up more energy at specific frequencies. Tube traps and those slatted type traps and the like are used for that, though it seems that some of the acoustics guys kind of poo-poo these sorts of tuned traps a bit.
 
Another issue is that 67Hz is getting down low enough that even pretty thick broadband traps have trouble with it effectively as well.

droddey

Danny Danzi

Dean, can't that 67 Hz cancellation be cured with an eq?
-Danny

No, unfortunately cancellations can't be cured by EQ. The issue is that, if you have a peak, then basically it's two waves adding together at a particular frequency. You can EQ that down (though you may not be able to EQ that big a peak in some cases) because you are just lowering the overly high combined waves. If you cut the energy of the wave going out at that energy, then the lower energy outgoing and reflected waves add up to a lower over all level.
 
With a cancellation they are cancelling each other out. If you push up the EQ, they still cancel each other out. If you lower it they still cancel each other out. So you can only deal with cancellations by preventing the signal from reflecting back to the listening position. That's generally done with traps that are broadband, meaning they suck up a wide range of frequencies. You don't want really any strong bass energy getting back to you from the walls if you can avoid it anyway, so if it sucks up other frequencies besides the ones you have trouble with, that's all good, too. And generally you have problems with more than one frequency anyway.
 
If you can't do it sufficiently with broadband absorption you would have to use a tuned trap that's able to suck up more energy at specific frequencies. Tube traps and those slatted type traps and the like are used for that, though it seems that some of the acoustics guys kind of poo-poo these sorts of tuned traps a bit.
 
Another issue is that 67Hz is getting down low enough that even pretty thick broadband traps have trouble with it effectively as well.

Great response Dean, thanks so much. So what would happen to you in this situation....you mix and never hear the low end you need to add in? Did you over-compensate for it until you knew there was a problem and wind up having mixes that were too bassy due to compensation? Man, what a tough situation to be in. I really appreciate the response because I honestly don't know a thing about this. I turn on my stuff now and it just works for me in spite of what may still be wrong in my rooms. But I did have problems with the frequencies I mentioned before. They just were never there...especially with my NS-10's. When I got the Adams and the sub, the low end was then audible, but then I was missing some mids from like 400-500 that were making me mix a bit too mid range congested.
 
Are you done with the new room set-up yet? Have you analyzed it? I hope it all goes well for you. :)
 
-Danny

I too read Mixing Secrets. 

I did not read all the posts to this point. I may go back and read them later when I have time. Someone may have already covered this aspect.


After reading that in the book, it makes sense and is true no doubt.  However..... I don't have the money to buy the top of the line speakers that are not ported and still have a good flat response.  Do you?  Remember that ALL speaker design...ported or other, is basically a trade off a compromise ..... one design gets you a certain benefit, a different design gives you a different benefit, BUT there is no design that is 100% perfect and delivers all the advantages with no downside. It is always a compromise of the characteristics. 

I think the advantage here is KNOWING that the speakers you are using have that false bias caused by the port. Knowing it is there, you are able to work with or around it more easily. If you do not know that there is a false frequency issue, how can you possibly compensate for it? 

At the end of the day, we all are likely using ported speakers since they are the most common and affordable design on the market.  

My music sounds good to me. So with that, and the knowledge of the shortcomings of the speakers I am using...... I march forward into my next musical project.  

In other words..... don't freak out. Knowledge is good. but don't let it throw you off course and distract you from the goal.  

I'm not taking sides here, so let's not mis-interpret things ok?
 
I've been working in critical listening environments since the late 1970s, and I've developed MY version of what's what. I make no claims that this is cast in stone, just that it has worked well for me.
 
First - you have to identify the task at hand. When I was building broadcast control rooms the goal was first to make sure that the operator (DJ) could hear everything clearly. That meant the music, certainly, but more important, if the listeners could hear his chair squeak, or air conditioners rumbling when the microphone was open they needed to know that! We tried to make the listening itself as fun as possible, and oh yeah, non-fatiguing!
 
Second - you have to respect your budget. I can find good and bad examples of pretty much every loudspeaker design, and I can find decent examples in any price range. While we are restricted, somewhat, by the laws of physics most blanket generalizations are, well, generalizations - what's that say about this paragraph??? Listen to the monitors in your environment and judge accordingly.
 
FWIW, it is easier to build a large loudspeaker than it is to build a small loudspeaker, and it is easier to build a sealed enclosure than to build a ported enclosure. Further, horns sound different than cones, and ribbons sound different than either! So assertions in previous posts than large, sealed enclosures sound better, while not complete, is not a bad rule of thumb. Sadly few of us have the space to use them!
 
Third - and this will sound paradoxical, but there is no way around it. As you spend more time listening critically your listening skills will improve. You will suddenly hear problems with your monitoring environment you never heard before (same goes for microphones, processors, etc.)
 
This is a very difficult issue. If cost were no object you'd hire Tom Hidley to design your monitors, and Russ Berger to design your control room, and you'd have a long wait till you heard any problems - maybe even never.
Sadly, few of us have that luxury. Your options are to build something and get on with the music making (with apologies to Apple and Guy K), or study physics and experiment with room construction (probably nearly as expensive as hiring Russ<G>!)
 
Fourth - it is FAR MORE IMPORTANT to know your monitoring environment than any other factor. If you know you have a bump (or hole) at 63 Hz then eventually you'll learn to mix such that it isn't a problem when you leave your room. It's more work than mixing in a better room, but it is absolutely possible.
 
Fifth, and this is important, and it is backed up with solid science (IOW, flame away, I can take it)... You can NOT yet fix time domain problems with frequency domain tools. I have no doubt that someday sufficient processing power will make this statement false, in fact the LARES system can do this today, but it requires a metric ton of microphones and loudspeakers and processing power. The key is to realize that there are no magic solutions. ARC or similar tools can tame some problems, but they will not, today, eliminate them.
 
So what are the priorities when designing a critical listening space?
 
My version, and it has worked well for me:
A) Isolation - plan for sufficient isolation to keep noises out (in return you'll keep the music in!)
 
B) Geometry and placement - these are so intertwined that you need to consider them together. You can, absolutely, build a reasonable listening space in a cube or rectangle (some designers prefer these simple shapes because they can predict behavior better). If you look at studio designs in Europe you'll discover that you can also build a reasonable listening space in a very small room. The catch is that it is quite difficult to build a reasonable listening space in a very small cube or rectangle - there are limits to everything!
 
C) Treatments - start with simple!!! Broadband diffusion, absorption, and reflection are easier to do, and work better. When you start tuning treatment devices, especially absorbers, you start to create unintended effects, some (most?) of which will not be immediately evident. Reserve tricks like tuned traps for your last resort. You will probably need it if your space is small, but you won't need as much of it - and therefore you will minimize the bad effects - if you start with simpler, broadband treatments.
 
D) MEASURE AND DOCUMENT EVERY STEP!!! Nuff said... there are tools available at no cost that do a very good job, and there are tools at low cost that are used by the pros. When you do this you'll know when you make a wrong turn.
 
My next room, when finances allow, will be relatively small, but it will provide ample isolation from the rest of the world, which was one of my priorities.
 
It will be rectangular, except that it will be aligned diagonally, and the front wall will cut off one corner.
 
The mains will be mounted in the walls, and the near field monitors will be stand mounted.
 
The rear wall and ceiling will have some form of quadratic diffusors located strategically (not sure exactly where, but I know the starting points, immediately above and behind me. It is important to note that there is an eleven foot space between the rear wall and my ears specifically to support the use of diffusors. Sadly there is not that much space above me<G>!
 
Absorption will be scattered on the side walls, and concentrated in the front walls. For now I hope not to need to tune it, but I won't know for sure until it is built.
 
There will also be polycylindrical diffusors on the side walls. I love these things - they can be modified to be absorbers, and they sound very natural, even in cramped quarters.
 
All this to suggest that the next time someone says that all ported nearfield monitors are junk - or that they can solve all your acoustical problems in software - or any other outlandish generalization, you need to think it through.