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.

Barring the ported issue, most of the things I'm reading makes perfect sense to me, as the in my post #60. To be honest he backs up his arguments very well so far. I'm trying to give as accurate a picture as I can of his views. I bought the book to learn and so far so good. And I'm learning something here as well. Thanks to all you guys for the enlightenment and entertainment!

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 guess this is one area where it can be potentially useful to check things with a spectrum analyser. Something with a decent resolution and has the ability to perform averaging over different time intervals.

We all know how much these things can occur in different positions in the room. Different speaker locations as well as listening positions. I'm with Dean on the idea that you can only use eq to cut as you can't eq back something which is nulled completely or significant in the first place. You're just making your speaker work hard for nothing and introducing potentially audible eq artefacts. You have lots of different sets of monitors. Maybe you may wish work out exactly where you problem frequencies are (you mention 67Hz specifically) and try to find another position in your room where this isn't so prevalent. It's possible with a bit of experimentation (but not definite) that you'll find another spot which eliminates the positions in your current area. It will, of course introduce other issues, but that's ok. Now you can compare both of these two positions when you master. Use your normal set-up, then every now and then, switch over to your other location just to check these particular areas you know are a problem in your room. Obviously this takes a great deal of understanding of your gear/set-up to work, but it might be a pretty simple compromise to allow you to master with a little extra confidence, knowing you have not missed anything (or reduced the things you might miss).

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.  

Guitarhacker


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.  

Agree wholeheartedly.  We can think of a million reasons not to make music, but letting them distract you from doing it is a step too far.  Ones gear may be a limitation, but it's not an excuse to keep plugging forward.  Learn to use what you have, it's weaknesses, those that can be overcome and those that possibly can't, but don't use it as an excuse to not make music with what you have.  I've said it before but I'll say it again, I think too many people give up on the tools they have and look to the next tool too quickly, hoping it will be the magic piece of equipment that will change everything for them.  


Sure, there are some problems that can't be overcome easily and it's true, you can't adjust what you can't hear - I think a point that, earlier in this thread, some may have misconstrued.  You can't compensate for something if you can't hear it, but you work with what you have and you find methods/tools to make up for the weaknesses you can control as best you can.



But in the end - keep making music.

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.

While it's clear that a full range non-ported monitor is going to be quite large, if you want something to supplement your near fields in the critical mid range here's a DIY project from Thomas Barefoot who makes some well respected and expensive studio monitors.

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=297

He calls them Killatones