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PostPosted: Sun Apr 29, 2012 2:27 am 
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Location: Florida
I posted here some time ago ,and thanks to the knowledge that everyone shares on this forum so generously I was able to help my room as much as I could.Quick reminder:
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ceiling 8 feet high.
I don't know If I'm going in the right direction ...Still my mixes don't sound too good.I was wondering how the REW document compares to your measurements and vice versa.What would you guys change in my room if it was the only place you could mix in? REW document :http://dl.dropbox.com/u/19906273/HELP.mdat ...and also pix of my room:
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PostPosted: Sun Apr 29, 2012 2:29 am 
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more pix
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Thanks guys!


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PostPosted: Sun Apr 29, 2012 8:15 am 
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First question: Did you roll of the bass correctly on your Adam speakers? From the REW file, it looks like you didn't do that. There's a control on the back that you can use to roll off the bass. Set that to -6 dB. That should help to compensate for the baffle step issue.

Second, lose those diffusers! That room is way, way too small to be able to benefit from most types of diffuser, and especially QRD based designs, even more so ones tuned to such low frequencies as yours!. They are causing you way more problems than they are solving. Worst of all, they seem to be right at your first reflection points! Moving your head even slightly is going to change the way you hear things like that.

Get those out of the room, and replace them with thick absorption panels.

Next, how did you build those soffits? There's only one photo of the construction, and it doesn't show enough to be useful. What's that large whit thing in the bottom of the box that surrounds the speaker, and also between the box and the shelf?

Also, what type of insulation did you use on your side panels, rear panels, and cloud? And how are they built? Are they hard-backed or not? If so, with what?

Finally, which speaker did you use for the REW test? The files only show one measurement, so I'm not sure if that is from the left speaker or the right speaker. In your room, that might make a difference, give the alcove off to one side. So it's important to know which speaker you used when you did the test.

Also, maybe you can describe how the room sounds: When you play a commercial recording that you know really well, what do you hear? Don't use anything that you mixed in the room, for obvious reasons: Use a commercially recorded song that you know very well, and have heard hundreds of times in different places, and listen to it carefully as you play it in your room. Try to describe what seems to be wrong with it.

But first set your speakers correctly, and also post the other information.


- Stuart -

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PostPosted: Mon Apr 30, 2012 11:00 am 
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Location: Florida
Hi,Thank you for your response, Stuart. I did some homework! So,....I did not have the bass rolled off on my Adams until yesterday - "better late than never" - Thanks.
The material under the speakers and the speaker shelves themselves, is a thick foam similar to the one usually found while unboxing electronics. I got some of that stuff in my Adam speaker boxes when I bought them. The idea was to prevent the vibration from the speakers going to the floor and the desk(seemed pretty cool to me at the time).
All my panels were built with Owen's Corning 703 ,and they all have soft back. The cloud and the outside panels on the back of the room, have the craft paper spray glued on the front behind the fabric. For the REW I actually used both speakers at the same time. Oops! The new REW test:http://dl.dropbox.com/u/19906273/NEW%20MEASUREMENTS.mdat. In this test, you can find four different measurements: two left and right with sub disengaged, and two left and right with sub engaged. I didn't have time to built two extra panels, so I just swapped them around. The QRDs took place of my back panels that were sitting in the middle and the ones from the back are now in the place of the QRDs.
To describe what is going on in the room to begin with, I must say that while listening to professional recordings I always, always felt like there was too much of 1.5 kHz -5 kHz range almost to the point that it was irritating. And again, until yesterday. What I did was I cut off the low shelf on my speakers -6dB like you suggested, then I cut some of the tweeter level around -2dB. And...boom all of a sudden - no problem!
After all the rearrangements and speaker adjustments, I noticed the following: 1. Larger area of the "sweet spot" -like you mentioned. 2. Wider stereo spread. 3. being able to hear reverb and the rest of the details. And 4. The right channel sounds a bit darker than the left (it always has). Is it pretty common or is it just me?

Thank you.


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PostPosted: Tue May 01, 2012 1:33 am 
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Great! Glad it came together for you. :)

That foam stuff under the speakers probably isn't doing all it is supposed to do. You have the right concept with that (decoupling the speakers from everything else), but maybe not the best implementation. That looks like just packing foam, which isn't really the right stuff to decouple the speaker from the stand. If you ever decide to upgrade your soffits, then you might consider changing that, and replacing it with something like neoprene or Sorbathane. Probably not worth doing now, as you'd have to disassemble the soffits completely and re-build them.

Talking bout the soffits, you didn't mention what the front panels are made of: MDF? Plywood? Drywall? And how thick are they?

On the issue with the right channel sounding different: No, that isn't normal, and is probably due to the asymmetrical shape of the room. To confirm that, try physically swapping the left and right speakers (take the right one out and put it in the left soffit, and vice-versa, to see if that changes anything. My guess is that it will still sound the same. Also try swapping the cabling and channels on your interface, but I doubt that is the issue. I suspect the room, and seeing that the absorption panels are not hard backed, that might be the issue to. You could try putting a couple of large sheets of thick plywood (5/8 or even 3/4) on the backs of the side absorbers, to help a bit with that.

I'm looking at the new REW data, and the overall response is MUCh better now. Night and day! You have about +/- 8dB across the entire spectrum now, and that's pretty good for a room like that. However, as you say, there's a big difference between left and right speakers, and I'm almost certain it is the room symmetry causing that. see how it goes after putting thick, massive, heavy hard backs on those side panels.

You also need more bass trapping in that room: I'd suggest doing something large and thick on the rear wall. There's a lot of energy still bouncing around at low frequencies, so large bass traps would really help to tighten that up.

Finally there's an overall dip on all your tests, centered around 500 Hz (350 hZ to 700 hz, aprox), which is hard to explain. (It might also be a rise at around 1.5k: hard to say for sure). I wonder what might be causing that in your room? Is there anything that might be acting as a some sort of panel trap, tuned around there? Maybe that closet? What's inside there? You could try repeating that test with the closet doors open, and see if that makes a difference. If it is a rise at 1.5 k, then that's a little confusing: not clear what could be causing that. Maybe its something to do with the measurement mic? What mic are you using for that?

Final suggestion (for now!) roll off another 2dB on the tweeters. You still have a bit of a peak at the very high end, so that might help a bit.

But overall, that's a big improvement over what you posted yesterday! Even if it doesn't get any better than that, it's still very good for a small and asymmetrical room like that.


- Stuart -

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PostPosted: Tue May 01, 2012 1:55 pm 
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Wow, that's good news. Could be much worse.
"Talking bout the soffits, you didn't mention what the front panels are made of: MDF? Plywood? Drywall? And how thick are they?"

I made them 10 " thick, so the speakers can sit in the shelves nicely(speakers are 10 " long as well). There is no plywood, MDF ,or drywall on the front of the panels. There's that blue fabric, a few layers of Owen's Corning (2") and the fabric on the back.

Swapping cables on the speakers didn't fix the issue of L&R channels sounding differently.

What type of bass traps would you recommend on the back wall? I know the old saying :"the thicker, the better" :D , but if I decided to stick with 703 what would be the desired thickness of the panels?

In my closet I mostly store my old clothes, but the closet doors are made out of tint. Is that what's resonating around 1.5K? Another thought is my ceiling fan (I never turn it on, but it's up there).

For my tests I use a dbx mic:
http://www.sweetwater.com/store/detail/ ... 7AodWjeFAQ

Thank you.


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PostPosted: Tue May 01, 2012 2:36 pm 
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Quote:
There is no plywood, MDF ,or drywall on the front of the panels.
:shock: :!: Then they aren't soffits! If all you have there is absorption surrounding the speakers, then you don't have a soffit at all. You just have a speaker mounted in an absorptive panel.

The purpose of a soffit is to act as an "infinite baffle", meaning a very solid, very rigid front panel that is very large, as compared to the size of the sound waves emitted by the speaker. Part of what it does is to ensure that the speaker can ONLY emit sound in the one direction, towards the room, and therefore it must prevent any sound waves from "wrapping" around behind the speaker, and bouncing off the front wall, where they cause interference patterns, comb filtering, phasing issues, reflections, and other nasty things that you don't want. This might well be the reason for that dip-rise-dip in the mids and highs: you might be getting phase cancellations, reflections and comb filtering going on, from the sound bouncing off the front wall and coming back at you. In a correctly built soffit, that simply should not be able to occur. There should not be any way that sound can even get to the front wall: in effect, the front panel of the soffit IS the front wall! That's why soffit mounting is sometimes called "in wall" mounting or "flush" mounting. The idea is that the front of the original speaker cabinet is "flush" with the front wall of the room (the soffit panel), so that the soffit basically acts as a new and super-sized speaker cabinet.

Another thing that the soffit does, is to force correct power balance of the speaker output. That's a bit harder to explain in simple terms, but in practice it means that you get smooth, tight. clear bass response, obviating the need for the baffle stop compensation the your speaker must do otherwise. A speaker sitting on a stand without a soffit (like yours is right now) is radiating twice as much power in the high frequencies as it is in the lows, and therefore the lows are boosted to double the power, but selectively, based on the width of the front panel of the original cabinet. When you mount the speaker in a soffit, that "selective boost" (correctly called "baffle step compensation") is no longer needed, and all the issues created by the circuit that does that can be avoided. That's what you did bu adjusting the bass roll-off: you negated the internal baffle step compensation. The reason why it worked somewhat, even though you don't have a soffit, is because your speakers are so close to the front wall that it is sort of doing the same thing, but not very well.


In order to do all of the above, a soffit MUST be a sealed, airtight box, with both a front and a back panel that are very solid, hard, rigid and massive. Some people even make them out of concrete, but thick plywood or MDF is fine.

So, I'd suggest that you add the front and rear panels to your soffits, cut a hole for the speaker to poke through, and seal the whole box airtight. But before you do that, take a look around the forum to see how soffits are supposed to be made, so you get a good feeling for the concepts. Use the search feature to look for "soffit", "flush mount", "baffle step", and things like that, to get a better idea of how to build them right.

The good news is that you have a good basic frame for your soffits, and you only need to add the front and rear panels. And since you'll be doing all that work on them, you might as well fix the issue with the packing foam too!

Quote:
Swapping cables on the speakers didn't fix the issue of L&R channels sounding differently.
It's not just the cables I was talking about: you need to physically swap the left and right speakers. Take the left one out of its "soffit" and put the right one in that space, then put the left one where the right one was.

Quote:
What type of bass traps would you recommend on the back wall? I know the old saying :"the thicker, the better" :D , but if I decided to stick with 703 what would be the desired thickness of the panels?
As thick as you can! :shot: :) I'd go with at least 4" spaced another 4" away from the wall, and even more if you can. I'd also consider building "superchunk" bass traps in at least some of the corners of the room.

Quote:
For my tests I use a dbx mic:

Great! That's a nice mic for testing, so that isn't the problem.


- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.


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