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PostPosted: Sun Mar 16, 2014 3:42 am 
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Location: New York, NY
Hello all - longtime lurker, first post.

My room details aren't really relevant to this question, but I want to follow the rules :) Small, purpose built studio primarily used for writing and mixing. The dimensions are 17L x 12W x 7.5H

I currently have a 2.1 system and I have a fairly good frequency response in my listening position. But the upper lows (95-120) have been difficult to tame. Specifically, 93-97 and 112-117. This isn't a surprise, because these areas correspond to known room modes and quarter-length waves. I've managed to smooth everything else out with a combination of room treatment and monitor placement. Everything above 140 is +/- 3db from the mean and everything below 90 is +/- 1db. Obviously I'm extremely happy with the low end.But the areas I have problems with are critical for me, and I'm always on the hunt for new things to try.

Based on some reading I've done, I'm currently experimenting with two matched subwoofers. I'm still working out the positions in the room and crossover settings that work best, but I'm still left with a question I don't know the answer to. In my current 2.1, the outs from my interface go to the sub and then get pushed back out to the near-fields. Before anybody says anything, I have tried running the near-fields at full range via a mirrored output from the interface, but it just didn't produce as even of a response.

So my question is this: which of these two ways should I connect the subs?

1. Keep it mostly the same, except add the 2nd sub between the 1st sub and near-fields? Therefore: Interface L/R out > Sub 1 L/R in > Sub 1 L/R out > Sub 2 L/R in > Sub 2 L/R out > Monitor In.

or

2. Split the stereo signal to L/R.Therefore: Interface Left out > Sub 1 Left in > Monitor Left in (and vice versa - Interface Right out > Sub 2 Right In > Monitor Right In

I can see pros and cons for both scenarios. I understand that placing subs is largely dependent on each rooms unique profile, but was wondering if there was commonly accepted wisdom in this matter.

Thanks in advance for any guidance or shared experiences that anyone can share.


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PostPosted: Wed Mar 19, 2014 4:19 am 
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Hey Mike, not being a fan of subwoofers for mixing (I do have one so I can occasionally check what is going on down there) I don't have much to tell you about how to connect them. I know that it is easier to deal with one subwoofer instead of two.

What is the crossover frequency that you are using? I wouldn't have the crossover set high enough that it would effect those frequencies. (then again, as I said, I don't like subwoofers for mixing)

What have you done with room treatment to specifically treat those frequencies?

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PostPosted: Thu Mar 20, 2014 12:24 am 
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Hi Eric,

I am not necessarily a fan of the idea of subs either, but most of my income comes from dance music and having an accurate sub in place helps me avoid overhyping the low end during the mix. That's been an issue for me personally for a long time. My brain wants to hear the thump and when it doesn't I tend to overcompensate for what I don't hear in the near fields.

As for crossover frequency, I've been experimenting relentlessly. I'll try one, take measurements, and then adjust it in tiny increments until I find which seems to work the best. Same with sub positioning - move it a bit, test and pick the best.

But no matter which combination of position, crossover and volume, I get peaks in the 93-97 hz area and nulls in the 107-114 area. Changing those variables results in a shift of which of these issues becomes better or worse. For example, some positions relax the peak but accentuates the null. And vice versa. Regardless, I'm talking about 10-15 db swings.

This is why I'm trying two subs. I've read a few things here and there that say two subs set up properly will excite different room modes. I was hoping some one has had success with this method and could share their experience about the best way to place it in the wiring path to avoid potential challenges.

As for treatment, I've got DIY floor to ceiling traps which perform extraordinarily well in all other areas. As I mentioned above, I am almost completely flat all the way down to 45hz. And 115 to 200 has only 2-3db variations. To me, that seems like a miracle.


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PostPosted: Thu Mar 20, 2014 3:23 am 
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Quote:
Same with sub positioning - move it a bit, test and pick the best.
There's actually an easier way to position subs, by doing it backwards: set up the sub where your head will be while mixing, then walk your head around possible locations for the sub while listen carefully... Down on your knees and close to the front wall, mostly, of course. It's a lot easier to move your head around the room, than it is to move the sub around!

True, this method won't necessarily excite exactly the same modal response as having things the other way around, but it can get you in the ball-park, then you can tweak it the final bit the way you are doing it now.

Quote:
But no matter which combination of position, crossover and volume, I get peaks in the 93-97 hz area and nulls in the 107-114 area
Then those are very likely modal issues, or SBIR issues, and NO amount of EQ or sub-walking is going to fix that. It is a room problem, not a sub problem, so the ONLY way to fix that is to fix the room.

Quote:
This is why I'm trying two subs. I've read a few things here and there that say two subs set up properly will excite different room modes.
Perhaps, and perhaps not... And that's assuming that your room even HAS other modes! Most small rooms have only a very tiny handful of modes in the low end, to play with, which is part of the problem. Exciting more modes is not the solution: damping all of the modes is the solution, best accomplished with large bass traps in the room corners.

Quote:
As for treatment, I've got DIY floor to ceiling traps which perform extraordinarily well in all other areas
How were those built? What materials, what technique, and what size.

Quote:
But the upper lows (95-120) have been difficult to tame. Specifically, 93-97 and 112-117.
94 Hz is your 0,2,0 axial mode, and 9.7 is your 3,0,0 axial, but you also have tangential modes at 88.8 and 99.8, and an oblique mode at 94.9. Not a happy picture!

Quote:
This isn't a surprise, because these areas correspond to known room modes and quarter-length waves.
It isn't just quarter waves on the room axes that you need to worry about: Harmonics are also an issue, and so are tangential and oblique modes.

Quote:
Everything above 140 is +/- 3db from the mean and everything below 90 is +/- 1db.
Did you measure that with REW? If not, then please do that. Then post the MDAT file here, so we can analyze it, and try to figure out where the problems are coming from, and how to deal with them.

Quote:
I have tried running the near-fields at full range via a mirrored output from the interface, but it just didn't produce as even of a response.
That won't work very well! (As I guess you already discovered). Doing that, you'd have multiple sources trying to produce the exact same very long waves, at different locations in the room. That's a recipe for acoustic disaster... :)

Quote:
So my question is this: which of these two ways should I connect the subs?
I would go with method #3: if the first sub has a direct out (post-crossover) then use that to feed the second sub, hopefully on an input that does not do any more filtering.

Failing that, go for method #4: Use an external stereo crossover, and pipe the "low" output to both subs in parallel, and the "high" output to each main monitor. In that case, you CAN set the built-in controls on the mains to "no sub" or set the crossover control (if there is one) way down as low as it will go, since you are doing the crossover elsewhere. Ditto for the subs: set the cross-over controls as high as they go, or use the direct input that does not go through any filtering, if there is one.

Quote:
I can see pros and cons for both scenarios. I understand that placing subs is largely dependent on each rooms unique profile, but was wondering if there was commonly accepted wisdom in this matter.
You'll need to set up the subs symmetrically, tight up against the front wall, and keep them in phase (both set to "0" or both set to "180", whichever works best). So if your left sub is two feet left of the center-line, then the other sub should be two feet right of the center-line.

But anyway, post the MDAT file from REW so we can take a look at that: it will lay bare all the secrets of the room! Then we can try to figure out the best way to deal with the issues.

Also please post some photos of the room, so we can SEE what it looks like, and how you have it set up. That helps a lot to understand what you are dealing with.


- Stuart -

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 Post subject: Re: nice
PostPosted: Thu Sep 25, 2014 1:39 am 
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muneeb wrote:
This isn't a surprise, because these areas correspond to known room modes and quarter-length waves.

Why are you repeating exactly what Mike said in his original post? What is your point?


EDIT: UPDATE on October 14: He was a spammer. Banned and blocked permanently. Bye! :)

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PostPosted: Tue Feb 24, 2015 8:10 pm 
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The internal volume - in order to maintain the correct low frequency cutoff and damping characteristics.

2. The front baffle dimensions - the baffle step compensation filter is designed to compensate specifically for the response shelf which occurs due to an 8" wide baffle. :horse:


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PostPosted: Wed Feb 25, 2015 7:22 am 
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glaxy wrote:
The internal volume - in order to maintain the correct low frequency cutoff and damping characteristics.

2. The front baffle dimensions - the baffle step compensation filter is designed to compensate specifically for the response shelf which occurs due to an 8" wide baffle. :horse:
What exactly are you trying to say? You are not making much sense...

UPDATE: As I suspected, he was a "signature spammer", who has now been banned and blocked permanently. Just one more sad, hopeless, low-life, in a long line of similar scum. They never seem to learn, though... Do they really think that anyone is even slightly inclined to click on their virus-and-malware infected links? If so, they must be dumber than I give them credit for...


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PostPosted: Tue Mar 10, 2015 10:50 pm 
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PostPosted: Tue Mar 10, 2015 10:50 pm 
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