Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 351 - AVS Forum
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post #10501 of 10806 Old 06-19-2014, 11:20 AM
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Originally Posted by jim19611961 View Post
JohnPM's response suggests the filters are the reason for the delay.
true but you are still aligning different peaks to 0 which is not how, in my experience, one aligns IRs. Since an ETC is the envelope of the IR then it's reasonable to wonder whether you can simply shift the IR like that and still get accurate results out of it. I don't know the answer to that (but would be interested to know).
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post #10502 of 10806 Old 06-19-2014, 11:23 AM
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Originally Posted by 3ll3d00d View Post
true but you are still aligning different peaks to 0 which is not how, in my experience, one aligns IRs. Since an ETC is the envelope of the IR then it's reasonable to wonder whether you can simply shift the IR like that and still get accurate results out of it. I don't know the answer to that (but would be interested to know).
Certainly, my contention is speculative. I could be wrong. Thus, posting my view to see if it stands up or not. Your query is valid. Perhaps JohnPM can give clarity.

My perspective rests on the crest of the first peak being equal to time zero. If this is wrong, then my argument is wrong. But intuitively, it seems right.

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post #10503 of 10806 Old 06-19-2014, 11:39 AM
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Quote:
Originally Posted by Rheagar View Post
Thanks for the reply and suggestions. I have read thru the guide, and still cannot get it to show up. I went thru every option I could find on the AVR(RX-A720) and as far as I can tell it should be working. I tested my bluray player thru that input and it worked fine. This lead me back to thinking the cable may be bad.

One important fact that I did not mention. I am attempting to connect my PC across the room to the AVR. This need lead me to purchase this 50' cable.

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

I attempted to use it just now from the bluray player to the AVR, and it didn't work. Could it be bad, or the length is the problem somehow?

Thanks for your thoughts!
PC's generally won't run more than one sound output at a time due to HDCP. So, at a minimum, unplug your PC speakers, or better yet, disable the Realtek in the BIOS or at least uninstall it, assuming you don't really use your PC speakers.

Does your Nvidia really have 4 HDMI outputs, or is that another issue?

Also, 50' is really pushing it. Can you at least test with a sub-30' cable?
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post #10504 of 10806 Old 06-19-2014, 12:05 PM
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Originally Posted by AustinJerry View Post
Looking at the Waterfall graphs, I see a significant improvement 35-40Hz for the left speaker, and a modest improvement 60-70Hz. I don't see any improvement for the right speaker. there is a modest improvement for the center speaker at 60Hz.

Looking at the ETC graphs, I see one reflection for the left speaker at 4m that has improved, and one improvement for the right speaker at 8.1m, but no improvement for the center speaker.

So, the existing treatments have had some positive impact, but I agree, there is room for more improvement.
Ah, I didn't look at the waterfalls at all. I'll do so tonight.

I'm a bit surprised that there was any effect on the center speaker. The first reflection point for that speaker on my left wall falls smack on the love-seat and therefore, under the panel that I mounted there.

Likewise, I'm surprised that the right speaker isn't showing something from this panel as I tried hard to make it low enough over the love-seat to catch the first reflection point from that speaker...I'll measure again, and maybe try REW with that panel 6 inches lower (resting on top of the love-seat) to see if it needs to be moved down some.

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Originally Posted by Audionut11 View Post
Anything bigger then a suggested minimum. Ideally, one that covers all 3 speaker reflection points. For me personally, as a minimum, I would use double width of your current panels over each speaker reflection point.
Do you mean double the depth? As in 6" instead of 3"? That's the plan (plus an air gap). Or do you mean 4' by 4' instead of 4' by 2'? Anyway, I've got plenty of space up there between the lights, so I'll do my best to cover the FRPs without covering any of the lights. :-)
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post #10505 of 10806 Old 06-19-2014, 12:11 PM
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Originally Posted by AustinJerry View Post
Or, you can look at the pics of my ceiling-mounted panels in the MySetup link in my sig (which were a DIY solution and not that easy).
I wasn't able to see anything that really shows how they are mounted. Can you point it out, or give me a quick overview?

Thanks.
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post #10506 of 10806 Old 06-19-2014, 12:25 PM
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Originally Posted by Audionut11 View Post
When using ASIO, plug any old output, into any old input, and select the appropriate settings in REW. "Timing reference output" + "Timing reference input". When you have an device connected to the input, you gain the use of that input in REW for timing, rather then just the USB mics.

@3ll3d00d has a handy reference here.


It's well worth the while also. I was surprised how far my timings were out when not using a reference signal.

edit: I've only just started using timing references in the last day or 2. Great for time aligning multiple speakers.
does that mean you're using 2 different devices for timing vs actual signals? If so, I'm not sure how reliable or precise that is as the timing reference is used to remove electronic signal delays (software, OS buffers and so on) from the time of flight. Hence if you use a different device then it may not go down the same path through the OS at the same time and hence might experience different delays thus yielding a false sense of accuracy. This is another one for John to confirm though.
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post #10507 of 10806 Old 06-19-2014, 01:52 PM
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Originally Posted by KevinG View Post
I wasn't able to see anything that really shows how they are mounted. Can you point it out, or give me a quick overview?

Thanks.
I will send a PM.
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post #10508 of 10806 Old 06-19-2014, 05:30 PM
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Quote:
Originally Posted by KevinG View Post
I wasn't able to see anything that really shows how they are mounted. Can you point it out, or give me a quick overview?
The acoustics treatments master thread might have helpful info on how to do what you're trying to do.
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post #10509 of 10806 Old 06-19-2014, 05:46 PM
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Tonight's efforts:

Mdat file:
https://drive.google.com/file/d/0B-G...it?usp=sharing

Description of what I did.

Took all 3 traps off the wall, move sub out of the room.
1) Measured just the left speaker.
2) Measured just the left speaker with a trap leaning on the wall (right where it would normally be mounted, but slightly lower)
3) Took all three traps and put them on the floor lining the path between the speaker and the mic
4) Took all three traps and put them side by side leaning against the wall near the speaker
5) Removed all traps, and put the sub back
6) Added back the single hanging treatment next to the speaker
7) Added a trap leaned against the "pillar" near the couch (facing the seating position)
8) Took the trap from the pillar, and the remaining trap and leaned them both against the closet door that would be the first reflection point on the right hand side wall.

Microphone set up.


I think there are a few take home points from this data.

1) The floor isn't one of the spikes (since I couldn't really do anything to any of the spikes with the treatments on the floor).
2) It does not seem as if the right hand wall is contributing much to the problem (which seems odd). Maybe I didn't look far enough away from 0ms to find it though?
3) The ceiling almost certainly is, but that is to be expected, since it is sheetrock, and untreated.
4) The sub being in place actually helps somewhat, because it is pretty well blocking the first reflection point off the left wall. It does, however, seem to contribute a spike of its own, but at least I know what it is coming from.
5) There are still numerous peaks that are unexplained.

Thanks for any and all insight!
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post #10510 of 10806 Old 06-19-2014, 05:52 PM
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Unless you really lean back, the mic placement seems to be too far back. Sit in the MLP and have someone assist you in determining how far forward the mic should be placed.

Regarding the reflections, it seems like you are guessing as to the sources. There are documented techniques to identify exactly what is causing them. The REW ETC graph has a tool that measures the distance to the reflection. And the "blocking technique" is also a good approach. Both are briefly described in the Guide. Did you read that section?
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post #10511 of 10806 Old 06-19-2014, 05:56 PM
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Quote:
Originally Posted by KevinG View Post
I think there are a few take home points from this data.

1) The floor isn't one of the spikes (since I couldn't really do anything to any of the spikes with the treatments on the floor).
2) It does not seem as if the right hand wall is contributing much to the problem (which seems odd). Maybe I didn't look far enough away from 0ms to find it though?
3) The ceiling almost certainly is, but that is to be expected, since it is sheetrock, and untreated.
4) The sub being in place actually helps somewhat, because it is pretty well blocking the first reflection point off the left wall. It does, however, seem to contribute a spike of its own, but at least I know what it is coming from.
5) There are still numerous peaks that are unexplained.

Thanks for any and all insight!
You can try the blocking method for a quick and easy way to narrow down the spike's location.

The blocking method involves placing the absorber right at the speaker, i.e.
- to check ceiling reflections, place the absorber on the top of the speaker extending at least 1' past the front of the speaker (further if possible). Note how the spikes change.
- repeat with the panel on the right side and then on the left

This will help narrow down the possible reflection points based on how the ETC changes with the panel placements (i.e. instead of absorbing them at the reflection point, you're placing the panels to absorb/block the direct wave before it even heads in the direction of the reflection point).


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post #10512 of 10806 Old 06-19-2014, 05:58 PM
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Quote:
Originally Posted by AustinJerry View Post
Unless you really lean back, the mic placement seems to be too far back. Sit in the MLP and have someone assist you in determining how far forward the mic should be placed.

Regarding the reflections, it seems like you are guessing as to the sources. There are documented techniques to identify exactly what is causing them. The REW ETC graph has a tool that measures the distance to the reflection. And the "blocking technique" is also a good approach. Both are briefly described in the Guide. Did you read that section?
LOL, looks like I was typing while you were posting.


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post #10513 of 10806 Old 06-19-2014, 09:28 PM
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Originally Posted by 3ll3d00d View Post
does that mean you're using 2 different devices for timing vs actual signals?
No. Sorry, I probably should have said, any old channel, not any old input/output.



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Originally Posted by KevinG View Post
Likewise, I'm surprised that the right speaker isn't showing something from this panel
It did. Look at the area 8-9ms. Unless you're responding directly about the waterfall discussion. IMHO, bass trapping is an entirely different room treatment to FRP, and the waterfalls will not hold any useful data wrt FRP. Any changes to bass ringing from FRP treatment, is simply a side benefit.


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Originally Posted by KevinG View Post
Do you mean double the depth? As in 6" instead of 3"? That's the plan (plus an air gap). Or do you mean 4' by 4' instead of 4' by 2'? Anyway, I've got plenty of space up there between the lights, so I'll do my best to cover the FRPs without covering any of the lights. :-)
4 by 4. At the end of the day, I would make them as big as you personally feel appropriate, wrt aesthetics etc.


Quote:
Originally Posted by KevinG View Post
1. The sub. It does reduce the FRP somewhat, but overall, the effect is negative IMO. Most noticeably, is @ 1.17ms where it increases an already high reflection by 4dB, and @ 7.05ms where it increases amplitude by 13dB. Somewhat obviously, the "wall with 3 traps" does a much better job. Having said that, the area @ 7.05ms looks to be a multiple reflection, and this may get caught by other treatments. Otherwise, you can try the blocking method on the sub, and try and find the location of the second bounce.

2. The floor treatment has an overall positive effect. Not so easy to see in the full band ETC due to the existing floor coverings. Look at around 10ms in 1000-2000hz sliced ETC.

3. The pillar is 6ms and 16ms. I would wrap the front, left (couch side), and rear to make sure it is not contributing to multiple reflections. Measuring that is your prerogative.

4. The right wall FRP is 16-17.5ms. The left wall FRP from the right speaker, is 8-9ms as noted above.

5. Most of the treatments have an effect on the tail end of that first reflection @ 1.17ms, but none actually really affect the peak at 1.17ms, expect the sub, which boosts it. This needs further investigation. Since the sub boosts that area, that should give you a few ideas.

6. 2.98ms is probably the ceiling, although the distances don't make sense. As Jerry and djbluemax1 mention, the blocking method will help determine that.

7. 29ms and later is probably the rear wall. Standing behind the microphone with 2 panels should confirm that.

8. All the other peaks are multiple reflection points, furniture, and whatnot. The overall levels will drop considerably when all treatments are in place.

Last edited by Audionut11; 06-19-2014 at 09:41 PM.
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post #10514 of 10806 Old 06-20-2014, 04:17 AM
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Excellent,

Thanks for all the advice. Without knowing the name "blocking method", last night I realized that I should suspend a panel right over the speaker to figure out exactly what the ceiling's contribution is. I like the idea of blocking each side separately to help identify at least the initial direction the sound is taking that is causing individual spikes. That being said, you guys are much better at identifying which spike is effected by each panel location. Maybe I'm not looking at the data correctly, but I find it pretty hard to eyeball by flopping back and forth between them.

Unfortunately, the room will be in heavy use tonight and tomorrow, so Sunday is the next time I'll be able to play in there. I'm going to start building the ceiling traps this weekend as well.

About this:
"5. Most of the treatments have an effect on the tail end of that first reflection @ 1.17ms, but none actually really affect the peak at 1.17ms, expect the sub, which boosts it. This needs further investigation. Since the sub boosts that area, that should give you a few ideas."

I guess that confirms that I'm not dealing with a reflection off the boom-stand for the mic, then? I'm not really sure what to think about the spike @ 1.17ms if the three traps on the wall didn't catch it, I don't know what will. With such a short duration, it has to be VERY close to the speaker, or VERY close to the mic. Maybe it's the couch itself? I do think that the mic is VERY close to where my ear ends up when seated (the couch is VERY soft, and you sink into it nicely). But, maybe I should move the mic just to see if that 1.17ms spike moves. OH! Actually, now that I think of it...these measurements were taken with the mic about 6 inches further back, and two inches lower than the first set that I posted. (since I realized the mic was too far forward (closer to my nose) in those tests). I should compare those and see if the 1.17ms spike is different.

-Kevin
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post #10515 of 10806 Old 06-20-2014, 08:45 AM
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Quote:
Originally Posted by Audionut11 View Post

5. Most of the treatments have an effect on the tail end of that first reflection @ 1.17ms, but none actually really affect the peak at 1.17ms, expect the sub, which boosts it. This needs further investigation. Since the sub boosts that area, that should give you a few ideas.
I did a ETC slice analysis and this peak is most prominent in the 6-8K range. That tells me it is a near and small reflective surface either to the mic or at the speaker. I would remove those couch pillows and see if anything changes.


I would say the peak around 3ms is a larger issue than the 1.17ms one. This one also is most prominent above 4K. That timing could be the floor, or coffee table. But the frequency content suggests a smaller reflective object more than a carpeted floor. Perhaps a side table or nearby chair. Or the sitting chair itself.

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Last edited by jim19611961; 06-20-2014 at 09:28 AM.
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post #10516 of 10806 Old 06-20-2014, 09:06 AM
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Quote:
Originally Posted by KevinG View Post
Excellent,

Thanks for all the advice. Without knowing the name "blocking method", last night I realized that I should suspend a panel right over the speaker to figure out exactly what the ceiling's contribution is. I like the idea of blocking each side separately to help identify at least the initial direction the sound is taking that is causing individual spikes. That being said, you guys are much better at identifying which spike is effected by each panel location. Maybe I'm not looking at the data correctly, but I find it pretty hard to eyeball by flopping back and forth between them.

Unfortunately, the room will be in heavy use tonight and tomorrow, so Sunday is the next time I'll be able to play in there. I'm going to start building the ceiling traps this weekend as well.

About this:
"5. Most of the treatments have an effect on the tail end of that first reflection @ 1.17ms, but none actually really affect the peak at 1.17ms, expect the sub, which boosts it. This needs further investigation. Since the sub boosts that area, that should give you a few ideas."

I guess that confirms that I'm not dealing with a reflection off the boom-stand for the mic, then? I'm not really sure what to think about the spike @ 1.17ms if the three traps on the wall didn't catch it, I don't know what will. With such a short duration, it has to be VERY close to the speaker, or VERY close to the mic. Maybe it's the couch itself? I do think that the mic is VERY close to where my ear ends up when seated (the couch is VERY soft, and you sink into it nicely). But, maybe I should move the mic just to see if that 1.17ms spike moves. OH! Actually, now that I think of it...these measurements were taken with the mic about 6 inches further back, and two inches lower than the first set that I posted. (since I realized the mic was too far forward (closer to my nose) in those tests). I should compare those and see if the 1.17ms spike is different.

-Kevin
Id like to see pics of more of the room.

Believe it or not, that corner pillow is suspect (most pillows are more reflective than people realize. Couch cushions as well)

Looking at the spectrogram in the early timing, you have a bizarre looking graph. A mirror of reflections in the 35ms range.

kevin spec.jpg

Also some abnormally high distortion peaks (>10% @ 100hz)(>35% @30Hz )(>190% @ 20hz)

kevin dostortion.jpg

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Last edited by jim19611961; 06-20-2014 at 09:18 AM.
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post #10517 of 10806 Old 06-20-2014, 10:25 AM
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Originally Posted by jim19611961 View Post
Id like to see pics of more of the room.


Looking at the spectrogram in the early timing, you have a bizarre looking graph. A mirror of reflections in the 35ms range.

Also some abnormally high distortion peaks (>10% @ 100hz)(>35% @30Hz)(>190% @ 20hz)
More pics are here: http://imgur.com/a/YOLoo

Happy to provide more if they can be of any assistance.

I can remove the throw pillows from the couch & loveseat, but the back of the couch that looks like pillows is actually attached. The air hockey table is too far from the mic position to be contributing, right? I really need to do the blocking test, and try blocking the rear of the room as well.

Not sure what to say about the bizarre waterfall, or high distortion. I can try measuring at lower volumes to avoid exiting the harmonics (rattling, vibrating) of the room, if you think that might help.
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post #10518 of 10806 Old 06-20-2014, 10:48 AM
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Quote:
Originally Posted by KevinG View Post
More pics are here: http://imgur.com/a/YOLoo

Happy to provide more if they can be of any assistance.

I can remove the throw pillows from the couch & loveseat, but the back of the couch that looks like pillows is actually attached. The air hockey table is too far from the mic position to be contributing, right? I really need to do the blocking test, and try blocking the rear of the room as well.

Not sure what to say about the bizarre waterfall, or high distortion. I can try measuring at lower volumes to avoid exiting the harmonics (rattling, vibrating) of the room, if you think that might help.
I dont really know:

1) How much you want to improve things
2) How much work your willing to do
3) How many aesthetics your willing to sacrifice for better sound

I don't mean this to sound overly critical, but your setup violates a fundamental practice.

Room symmetry - You want the area behind the speakers and all around to the sides of the listening position to be symmetrical.

In your case, you have huge openings on one side (behind and to the side of the right speaker), and not the other. One speaker is barely a foot or two from the side wall, while the other is 6 feet or more.

--- ---- ---- ----

I would consider putting the speakers and screen on the long wall in your case. While I usually don't recommend this, in your case, you get much better L to R symmetry . And you would still have >19' to work with back to front. I know this would be a lot of work, but I would at least move the speakers and listening area into that configuration and see how things sound and measure. While I can see a few things being more problematic, I think the pluses out weigh the minuses by a good margin.

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Last edited by jim19611961; 06-20-2014 at 11:09 AM.
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post #10519 of 10806 Old 06-20-2014, 11:45 AM
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Originally Posted by jim19611961 View Post
I dont really know:

1) How much you want to improve things
2) How much work your willing to do
3) How many aesthetics your willing to sacrifice for better sound

I don't mean this to sound overly critical, but your setup violates a fundamental practice.

Room symmetry - You want the area behind the speakers and all around to the sides of the listening position to be symmetrical.

In your case, you have huge openings on one side (behind and to the side of the right speaker), and not the other. One speaker is barely a foot or two from the side wall, while the other is 6 feet or more.

--- ---- ---- ----

I would consider putting the speakers and screen on the long wall in your case. While I usually don't recommend this, in your case, you get much better L to R symmetry . And you would still have >19' to work with back to front. I know this would be a lot of work, but I would at least move the speakers and listening area into that configuration and see how things sound and measure. While I can see a few things being more problematic, I think the pluses out weigh the minuses by a good margin.
Understood. But that's the one thing that is off limits. The room must stay the way it is (for lots of reasons).

So, to answer your questions:
1) As much as possible, given the current room layout.
2) Lots of work. I've already done lots, and plan to have to do lots more.
3) Aesthetics are of some concern, but I'd want to know the trade-offs.

If everyone thinks that the room, as it is, isn't worth treating because the end results will never be "amazing", then I'm willing to accept that, and live with it the way it is. However, if by spending a few more hundred dollars, and a bunch of hours of time, I can improve the room significantly (while still not making it great) then I'm happy to do so. That being said, I can't imagine that adding treatments is ever a "bad" thing to do...

Maybe what you are saying is that nitpicking at the level I am now isn't worth it...and I should just finish building and installing, and call it a day. In the end, it'll be better than it is, but still not perfect. I'm okay with that.
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post #10520 of 10806 Old 06-20-2014, 11:49 AM
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Understood. But that's the one thing that is off limits. The room must stay the way it is (for lots of reasons).

So, to answer your questions:
1) As much as possible, given the current room layout.
2) Lots of work. I've already done lots, and plan to have to do lots more.
3) Aesthetics are of some concern, but I'd want to know the trade-offs.

If everyone thinks that the room, as it is, isn't worth treating because the end results will never be "amazing", then I'm willing to accept that, and live with it the way it is. However, if by spending a few more hundred dollars, and a bunch of hours of time, I can improve the room significantly (while still not making it great) then I'm happy to do so. That being said, I can't imagine that adding treatments is ever a "bad" thing to do...

Maybe what you are saying is that nitpicking at the level I am now isn't worth it...and I should just finish building and installing, and call it a day. In the end, it'll be better than it is, but still not perfect. I'm okay with that.
I wouldn't go that far. But the setup as is will only yield pennies on the dollar in pursuit of further treatment and investment.

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post #10521 of 10806 Old 06-20-2014, 11:57 AM
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I wouldn't go that far. But the setup as is will only yield pennies on the dollar in pursuit of further treatment and investment.
Okay, fair enough. I'll consider the materials that I've already purchased to be sunk costs, finish building what I can, and consider it "as good as it gets."
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post #10522 of 10806 Old 06-20-2014, 12:02 PM
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Okay, fair enough. I'll consider the materials that I've already purchased to be sunk costs, finish building what I can, and consider it "as good as it gets."
I didn't say that. Further bass trapping resulting in better decay is certainly something you can do to improve things.

But trying to achieve amazing imaging and channel balance may be too far a bridge to cross.

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post #10523 of 10806 Old 06-20-2014, 12:04 PM
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I didn't say that. Further bass trapping resulting in better decay is certainly something you can do to improve things.

But trying to achieve amazing imaging and channel balance may be too far a bridge to cross.
Understood.
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post #10524 of 10806 Old 06-20-2014, 03:14 PM
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Would it be possible to normalize the timing as well as the amplitudes via software in future REW versions via extra control features?
Most things are possible, not clear what that would achieve though? The main purpose of the fractional octave filtering of the IR is to examine the rate of decay in the different bands, that is not affected by time alignment.

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Additionally, would it be possible to make fullrange ETC's reflect even amplitudes for all frequencies rather than favoring the upper registers?
I don't think I understand the question - did you mean to write filtered ETC's rather than full range? To allow comparison of the amplitudes of different fractional octave bands just turn off normalisation.
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post #10525 of 10806 Old 06-20-2014, 03:22 PM
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Most things are possible, not clear what that would achieve though? The main purpose of the fractional octave filtering of the IR is to examine the rate of decay in the different bands, that is not affected by time alignment.
Perhaps that is what many use it for. But if your trying to glean the frequency makeup of a reflection, then timing is an issue.

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I don't think I understand the question - did you mean to write filtered ETC's rather than full range? To allow comparison of the amplitudes of different fractional octave bands just turn off normalisation.
The full range ETC seems to favor the higher registers. So I was wondering if a feature could be constructed so it treats them all equally.

See Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs for my analysis/comments on this subject.

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post #10526 of 10806 Old 06-20-2014, 04:02 PM
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The full range ETC seems to favor the higher registers. So I was wondering if a feature could be constructed so it treats them all equally.
The envelope of a time signal doesn't favour anything, it simply reflects the signal's content. You are perhaps being misled by the logarithmic dB scaling and normalisation. Try looking at the effects of the different filters with the linear %FS scale and no normalisation (you will have to zoom the magnitude in to the limits of REW's display) to see what actually happens to the time signal and its envelope as different filters are applied.
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post #10527 of 10806 Old 06-20-2014, 04:17 PM
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The envelope of a time signal doesn't favour anything, it simply reflects the signal's content. You are perhaps being misled by the logarithmic dB scaling and normalisation. Try looking at the effects of the different filters with the linear %FS scale and no normalisation (you will have to zoom the magnitude in to the limits of REW's display) to see what actually happens to the time signal and its envelope as different filters are applied.
Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs

Looking at this ^^^^, it sure seems like REW is seeing 4K and 500hz t=0 at VERY different magnitudes. Additionally, when you normalize several filtered ETC's and compare them to the full range ETC, the full range ETC always most resembles the higher frequency slices. Can you explain this?

I have no idea what %FS is showing me.

It is quite possible I am not getting something. But unfortunately, your response hasn't clarified anything for me.

edit: I suppose what I am after is what does a full range ETC really represent? Full range implies all frequencies are represented. Yes? If one had a perfectly flat FR curve, shouldn't every filtered slice have the same magnitude at t=0 in such an example? If not, why?

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Last edited by jim19611961; 06-21-2014 at 09:37 AM.
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post #10528 of 10806 Old 06-21-2014, 04:46 PM
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%FS is percentage of full scale. It is a linear axis, so if the value it is showing is halved the trace would only go up half as far. A linear Y axis is common with time signals, unless there is a need to show a very large dynamic range, in which case a logarithmic axis makes it easier to get the range of interest onto the plot. The impulse response and its envelope are time signals.

"Full range" means without any filter applied to limit the range. The filtered IR graph allows various octave and one-third octave bandwidth filters to be applied to the impulse response. It then shows the impulse response after the filter has been applied. The envelope changes correspondingly. Applying a filter to a time signal changes its shape. In particular, applying low centre frequency bandpass filters to a signal will suppress all its rapid changes, since the filtered output will by definition not have high frequency content - just as a subwoofer cannot reproduce a finger snap, for example. Generally speaking, the lower the filter's centre frequency the more the amplitude of any sharp features passed through it will be reduced and the more they will be spread out in time. If the original signal did have a perfectly flat response it would itself be a perfect, single sample duration impulse. The outputs of the various filters would then be their own impulse responses, since the signal going into them would be an impulse.
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post #10529 of 10806 Old 06-21-2014, 08:59 PM
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So, I just got a new laptop and checked the HDMI Supported Formats...it's 2 channel only.

Is there any way (install different drivers or something) to get it to output 7.1, or am I just screwed?
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post #10530 of 10806 Old 06-21-2014, 09:02 PM
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Mine only supports stereo and I have not felt this is a big deal. I don't think measuring surrounds and surround backs is important, and you can do everything else with two channel support.

HST, return it for a different model if you feel 7.1 support is important.
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