Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 931 - AVS Forum | Home Theater Discussions And Reviews
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post #27901 of 28192 Old 09-21-2019, 05:45 AM
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Originally Posted by pau View Post
Could someone wiser than me check my REW measurements after ARC and see if they can figure why there is so big dip in response on front channels between 100-200hz compared to what Anthem's ARC calculated. All crossovers are set to 80hz for FR/C/FR and subwoofer. Attached a picture of fronts+sub sweeps.


REW measurements,

https://drive.google.com/file/d/1Tl0...8Qsw97A31_sxBV

Allso looking at the impulse response from REW, it shows FR and Surrounds impulse going opposite from FL, C and Subwoofer. Does that indicate those speakers are at wrong phase / polarity ?

Too much things happening after buying miniDSP and UMIK. Atleast finally i got to see what ARC does and how should go forward with room acoustics etc. ARC doesn't seem to do well on taming 300Hz - 1000Hz range so i guess that could use some room threatment?


Also woofer is far from ideal and has to be done starting with possible moving things around, but would like to first set the front stage correct and go from there.
My observations:

1. Your measurement level is quite low. I would shoot for a level of ~90dB. This doesn't affect the validity of your measurements, just something to consider in the future.
2. If you use the more conventional 50-100Hz range for the vertical axis, the measurements don't look that bad. A variances of 10dB over a measurement range is reasonable. A 5dB variance would be exceptional. And the ARC results are likely an average over multiple listening positions, which could be why they don't match the REW measurements.c
3. You should look at the sub response from 15-300Hz, un-smoothed (see attachment). This reveals a dip at ~40Hz, which might be eliminated by better sub placement, or additional subs.
4. Your mains are not precisely time-aligned (2nd attachment). I am surprised ARC does not do a better job. You might try experimenting with the manual distance setting.
5. The mains indeed look to be of opposite polarity as the surrounds, not sure why.
6. The mains and the sub seem to have opposite polarity as well (3rd attachment). Reversing the sub polarity may affect that 40Hz dip.
7. The ETC (4th attachment) shows quite a few early reflections greater than -20dB, which carefully-placed treatments should resolve.
8. The waterfall (5th attachment) shows quite a bit of bass ringing, which could be alleviated with bass traps.
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post #27902 of 28192 Old 09-21-2019, 10:50 AM
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First time messing around with REW today. Got all my subs level matched and a few other tweaks. This is the graph I got which I’m thinking is pretty good. But maybe I’m missing something so I figured I’d post.
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post #27903 of 28192 Old 09-21-2019, 11:33 AM
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Originally Posted by dwander View Post
First time messing around with REW today. Got all my subs level matched and a few other tweaks. This is the graph I got which I’m thinking is pretty good. But maybe I’m missing something so I figured I’d post.
Looks pretty good. Suggestions for presenting REW measurements:

- Set the vertical scale 50-100dB. 0-100dB makes the measurements look better than they really are. And present sub measurements 15-300Hz, no smoothing.

- Rather than taking a photo of the screen, click the Camera icon in the upper left corner to do your screen captures.
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post #27904 of 28192 Old 09-21-2019, 11:55 AM
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Quote:
Originally Posted by AustinJerry View Post
Quote:
Originally Posted by dwander View Post
First time messing around with REW today. Got all my subs level matched and a few other tweaks. This is the graph I got which I’️m thinking is pretty good. But maybe I’️m missing something so I figured I’️d post.
Looks pretty good. Suggestions for presenting REW measurements:

- Set the vertical scale 50-100dB. 0-100dB makes the measurements look better than they really are. And present sub measurements 15-300Hz, no smoothing.

- Rather than taking a photo of the screen, click the Camera icon in the upper left corner to do your screen captures.
Thanks very much. Gonna do that now and repost. Btw your guides are amazing. My next step was to get a minidsp So I can eq the subs all separately. Right now, sub1 handles an identical pair in the front and sub2 handles a different identical pair in the back. The front pair are each the same distance to the MLP, as are the back. So assuming my current response is pretty good then is there still a lot of Benefit to be had by adding the miniDSP?

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post #27905 of 28192 Old 09-21-2019, 12:08 PM
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Quote:
Originally Posted by AustinJerry View Post
Looks pretty good. Suggestions for presenting REW measurements:

- Set the vertical scale 50-100dB. 0-100dB makes the measurements look better than they really are. And present sub measurements 15-300Hz, no smoothing.

- Rather than taking a photo of the screen, click the Camera icon in the upper left corner to do your screen captures.
Yea not so pretty anymore. didn't extend to 300 hZ bc i didn't want to turn everything back on at the moment but any comments would be helpful.
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post #27906 of 28192 Old 09-21-2019, 12:49 PM
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Quote:
Originally Posted by dwander View Post
Yea not so pretty anymore. didn't extend to 300 hZ bc i didn't want to turn everything back on at the moment but any comments would be helpful.
Change it to 5db increments and include legend so we know its not smoothed at all. Or just screen shot your pc and post it in here. Bet you it won't look as pretty either. lol But that's the fun part!

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post #27907 of 28192 Old 09-21-2019, 12:59 PM
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Originally Posted by ereed View Post
Change it to 5db increments and include legend so we know its not smoothed at all. Or just screen shot your pc and post it in here. Bet you it won't look as pretty either. lol But that's the fun part!
think this is it.
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post #27908 of 28192 Old 09-21-2019, 02:14 PM
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Originally Posted by dwander View Post
think this is it.
Yes, the un-smoothed response has revealed that there is still some work to be done.

Couple of things to check. How to do these recommendations are included in the 2x4 guide linked in my sig.

1. Check individual time alignment for all four subs using REW impulse measurement. With your placement, there shouldn’t be a significant problem with alignment, but it is always nice to check.
2. Check polarity, also using impulse measurement. Make sure you measure two front subs and two rear subs, and check the polarity of the pairs. My two rear subs have opposite polarity from the front pair.
3. If your front pair and rear pair are equidistant from the MLP, the sub pairs are probably well time-aligned. And if you are using Audyssey XT32, than the front and rear pairs should be aligned with each other. If this is the case, I see little value in adding a MiniDSP2x4. Only if you find sub-to-sub alignment issues would a 2x4 be warranted.
4. After you run automated room correction, you should do the Sub Distance Tweak to smooth out the alignment between the combined sub signal and the mains (specifically the center channel).
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post #27909 of 28192 Old 09-21-2019, 02:43 PM
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Quote:
Originally Posted by AustinJerry View Post
Quote:
Originally Posted by dwander View Post
think this is it.
Yes, the un-smoothed response has revealed that there is still some work to be done.

Couple of things to check. How to do these recommendations are included in the 2x4 guide linked in my sig.

1. Check individual time alignment for all four subs using REW impulse measurement. With your placement, there shouldn’️t be a significant problem with alignment, but it is always nice to check.
2. Check polarity, also using impulse measurement. Make sure you measure two front subs and two rear subs, and check the polarity of the pairs. My two rear subs have opposite polarity from the front pair.
3. If your front pair and rear pair are equidistant from the MLP, the sub pairs are probably well time-aligned. And if you are using Audyssey XT32, than the front and rear pairs should be aligned with each other. If this is the case, I see little value in adding a MiniDSP2x4. Only if you find sub-to-sub alignment issues would a 2x4 be warranted.
4. After you run automated room correction, you should do the Sub Distance Tweak to smooth out the alignment between the combined sub signal and the mains (specifically the center channel).
I’m going to get on all of this. Really been a huge help. Just want to clarify one thing: the rear subs are actually closer to the MLP than the fronts. I meant the two fronts are equidistant to the MLP and the two rears are equidistant to the MLP. If that makes sense.

I do have one more question. One of the reasons I was considering the minidsp is bc the rear subs are split with an amp running some buttkickers. So I was looking to run the buttkickers on their own output and delay without any eq on them. It’s just about 4 ft from the subs to the MLP and Buttkickers. So maybe you could comment on whether I’m over thinking that.

Is it fine to just split them with whichever pair of subs has a more similar audyssey determined distance and call it a day?

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post #27910 of 28192 Old 09-21-2019, 03:29 PM
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I’m going to get on all of this. Really been a huge help. Just want to clarify one thing: the rear subs are actually closer to the MLP than the fronts. I meant the two fronts are equidistant to the MLP and the two rears are equidistant to the MLP. If that makes sense.

I do have one more question. One of the reasons I was considering the minidsp is bc the rear subs are split with an amp running some buttkickers. So I was looking to run the buttkickers on their own output and delay without any eq on them. It’s just about 4 ft from the subs to the MLP and Buttkickers. So maybe you could comment on whether I’m over thinking that.

Is it fine to just split them with whichever pair of subs has a more similar audyssey determined distance and call it a day?
I understand that you have two sub pairs, and within each pair, the subs re equidistant.

I have no experience with Buttkickers, so someone else will need to provide advice.
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post #27911 of 28192 Old 09-21-2019, 11:16 PM
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Quote:
Originally Posted by AustinJerry View Post
My observations:

1. Your measurement level is quite low. I would shoot for a level of ~90dB. This doesn't affect the validity of your measurements, just something to consider in the future.
2. If you use the more conventional 50-100Hz range for the vertical axis, the measurements don't look that bad. A variances of 10dB over a measurement range is reasonable. A 5dB variance would be exceptional. And the ARC results are likely an average over multiple listening positions, which could be why they don't match the REW measurements.c
3. You should look at the sub response from 15-300Hz, un-smoothed (see attachment). This reveals a dip at ~40Hz, which might be eliminated by better sub placement, or additional subs.
4. Your mains are not precisely time-aligned (2nd attachment). I am surprised ARC does not do a better job. You might try experimenting with the manual distance setting.
5. The mains indeed look to be of opposite polarity as the surrounds, not sure why.
6. The mains and the sub seem to have opposite polarity as well (3rd attachment). Reversing the sub polarity may affect that 40Hz dip.
7. The ETC (4th attachment) shows quite a few early reflections greater than -20dB, which carefully-placed treatments should resolve.
8. The waterfall (5th attachment) shows quite a bit of bass ringing, which could be alleviated with bass traps.
Hi Jerry and thanks for the great insight. I'm aware of the dip in subwoofer response. Haven't had much luck with where to place subwoofer in the house. Might need another subwoofer to tame that one. Hopefully i have time next weekend to see what can be done about it with just one subwoofer in different positions.

I checked the polarities on all speakers and now they should be better. Did a fast impulse measurements last evening just to see they are going same direction (attachment). About the distances, Anthem's ARC doesn't set speaker distances so it is all put manual with measuring tape. They should be pretty close now.

I allso had HDMI channel 2 and 3 messed in the first measurements. Thought they were center(2) and FL(3) but its the opposite. Subwoofer distance tweaking is allso in the to-do list for next weekend.

Surely there is lot to learn about all REW data that can be collected. I'm going to hold on to those ETC measurement as its a bit too much for one sitting to digest.
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post #27912 of 28192 Old 09-22-2019, 05:48 AM
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Yes, polarity seems to be correct now. It is hard to believe that ARC doesn’t set speaker distances. Using a tape measure is not very accurate acoustically, but thankfully REW will allow you to do it precisely. And achieving flat response with only one sub is challenging.
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post #27913 of 28192 Old 09-22-2019, 06:51 AM
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Quote:
Originally Posted by pau View Post
Hi Jerry and thanks for the great insight. I'm aware of the dip in subwoofer response. Haven't had much luck with where to place subwoofer in the house. Might need another subwoofer to tame that one. Hopefully i have time next weekend to see what can be done about it with just one subwoofer in different positions.

I checked the polarities on all speakers and now they should be better. Did a fast impulse measurements last evening just to see they are going same direction (attachment). About the distances, Anthem's ARC doesn't set speaker distances so it is all put manual with measuring tape. They should be pretty close now.

I allso had HDMI channel 2 and 3 messed in the first measurements. Thought they were center(2) and FL(3) but its the opposite. Subwoofer distance tweaking is allso in the to-do list for next weekend.

Surely there is lot to learn about all REW data that can be collected. I'm going to hold on to those ETC measurement as its a bit too much for one sitting to digest.
What are you looking for in the impulse measurement chart to tell if the polarity is right? thanks
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post #27914 of 28192 Old 09-22-2019, 07:10 AM
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What are you looking for in the impulse measurement chart to tell if the polarity is right? thanks
Look at the initial impulse. It will go either upwards or downwards. The direction indicates the speaker’s polarity. For a set of speakers (including subs), all initial impulses should go in the same direction.

I have attached an example of two sets of subs which have opposite polarity.
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post #27915 of 28192 Old 09-22-2019, 07:58 AM
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2 sub polarity

Are you pros saying that 2 subs polarity can be wrong, even if the wired connections are correct?

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post #27916 of 28192 Old 09-22-2019, 08:37 AM
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After testing and reposition things in my listening room, can anyone share thoughts about my response in my room? Would be much appreciated!
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post #27917 of 28192 Old 09-22-2019, 09:23 AM
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Quote:
Originally Posted by AustinJerry View Post
Yes, the un-smoothed response has revealed that there is still some work to be done.

Couple of things to check. How to do these recommendations are included in the 2x4 guide linked in my sig.

1. Check individual time alignment for all four subs using REW impulse measurement. With your placement, there shouldn’t be a significant problem with alignment, but it is always nice to check.
2. Check polarity, also using impulse measurement. Make sure you measure two front subs and two rear subs, and check the polarity of the pairs. My two rear subs have opposite polarity from the front pair.
3. If your front pair and rear pair are equidistant from the MLP, the sub pairs are probably well time-aligned. And if you are using Audyssey XT32, than the front and rear pairs should be aligned with each other. If this is the case, I see little value in adding a MiniDSP2x4. Only if you find sub-to-sub alignment issues would a 2x4 be warranted.
4. After you run automated room correction, you should do the Sub Distance Tweak to smooth out the alignment between the combined sub signal and the mains (specifically the center channel).
So time alignment between the two pairs definitely an issue as was polarity. Polarity was easy enough to check and fix but I'm not sure about the delay. I know I'm closer now but im not really 100% sure in what im looking for, so if you see something worth noting in this graph please let me know. Not sure if it matters but i fixed the polarity after i created this graph.

thanks
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post #27918 of 28192 Old 09-22-2019, 11:16 AM
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Originally Posted by IMWhizzle View Post
After testing and reposition things in my listening room, can anyone share thoughts about my response in my room? Would be much appreciated!
The waterfall you posted is formatted strangely. I have attached a waterfall from the MDAT you shared that looks more like what we are used to seeing. Unfortunately, it is showing quite a bit of bass ringing.
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post #27919 of 28192 Old 09-22-2019, 11:24 AM
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Originally Posted by dwander View Post
So time alignment between the two pairs definitely an issue as was polarity. Polarity was easy enough to check and fix but I'm not sure about the delay. I know I'm closer now but im not really 100% sure in what im looking for, so if you see something worth noting in this graph please let me know. Not sure if it matters but i fixed the polarity after i created this graph.

thanks
The graph you posted looks to be a frequency response graph. Time alignment is viewed with the Impulse response overlay, as shown in the attached screenshot.
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post #27920 of 28192 Old 09-22-2019, 11:24 AM
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Quote:
Originally Posted by AustinJerry View Post
The waterfall you posted is formatted strangely. I have attached a waterfall from the MDAT you shared that looks more like what we are used to seeing. Unfortunately, it is showing quite a bit of bass ringing.


Yes, I’ve heard that before. Don’t know what to do anymore since I don’t have the freedom to reposition the subs and treat the room with absorbers, etc. It’s a living room.

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post #27921 of 28192 Old 09-22-2019, 11:26 AM
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Originally Posted by IMWhizzle View Post
Yes, I’ve heard that before. Don’t know what to do anymore since I don’t have the freedom to reposition the subs and treat the room with absorbers, etc. It’s a living room.
It is only an issue if you don't enjoy how it sounds.
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post #27922 of 28192 Old 09-22-2019, 11:42 AM
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Hi -- new to this. Attached are 3 graphs made from 2 measurements

- Left + Right + Sub
- LFE

I think the waterfall and spectrograph look ok, but I am really a novice, so maybe totally wrong.

The frequency response looks to have a big drop just above 100Hz. What does that indicate?

Thanks so much!
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post #27923 of 28192 Old 09-22-2019, 12:15 PM
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Quote:
Originally Posted by freshmanjs View Post

I think the waterfall and spectrograph look ok, but I am really a novice, so maybe totally wrong.

The frequency response looks to have a big drop just above 100Hz. What does that indicate?

Do you listen only to the subwoofer?


Joking aside, that's some impressive short bass decay. Tight! Have you installed bass traps? How big is the room?


Regarding the 100 Hz dip: have you tried to change the sub's distance in the AVR, yet?


I'd also measure L+sub and R+sub, too, to see if the dip changes.


You don't have a center speaker?

Good sound is always the result of engineering. And engineering always starts with measuring. Consumer industry and mainstream will never tell customers about that: improvements in room acoustics are worth roughly ten (10!) times the amount spent on equipment like speakers and receivers. For example: only $500 in room treatment is worth more than spending $5000 (fivethousand) on equipment.

Last edited by Skinfax1; 09-22-2019 at 12:20 PM.
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post #27924 of 28192 Old 09-22-2019, 12:52 PM
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Quote:
Originally Posted by AustinJerry View Post
The graph you posted looks to be a frequency response graph. Time alignment is viewed with the Impulse response overlay, as shown in the attached screenshot.
Yea I’m sorry about that. Realized about 30 minutes ago I was confusing two things. But I definitely have time alignment issues. Front subs definitely not aligned with each other. Also seems like front and rear pairs are off based on the graphs but either way I’m all over the place with this right now. Gotta spend some more time with your guides and some other research and get a little more educated.

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post #27925 of 28192 Old 09-22-2019, 12:55 PM
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Update - full set of measurement data and a few more graphs attached here. I'd love any feedback, particularly what is happening to Center Channel and Sub 1 in the 120Hz range or so.

https://drive.google.com/open?id=1xi...uRdG0Lm8ZZg-bC
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post #27926 of 28192 Old 09-22-2019, 01:24 PM
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Quote:
Originally Posted by freshmanjs View Post
Hi -- new to this. Attached are 3 graphs made from 2 measurements

- Left + Right + Sub
- LFE

I think the waterfall and spectrograph look ok, but I am really a novice, so maybe totally wrong.

The frequency response looks to have a big drop just above 100Hz. What does that indicate?

Thanks so much!
Waterfall and Spectrogram look respectable. I would experiment with the sub distance tweak to see if you can improve on that dip, or try different crossover values. And I would measure center+subs, not LR+subs.
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post #27927 of 28192 Old 09-22-2019, 01:28 PM
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Originally Posted by dwander View Post
Yea I’m sorry about that. Realized about 30 minutes ago I was confusing two things. But I definitely have time alignment issues. Front subs definitely not aligned with each other. Also seems like front and rear pairs are off based on the graphs but either way I’m all over the place with this right now. Gotta spend some more time with your guides and some other research and get a little more educated.
With sub pairs, there are two approaches to time-aligning the subs within the pairs: either re-position the subs until they are precisely equidistant from the MLP, or utilize a device like the MiniDSP 2x4, which can time-align four sub channels. My 2x4 guide explains how to do this.
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post #27928 of 28192 Old 09-22-2019, 04:45 PM
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Hey all, trying this here for the umpeenth time, lol. - REW, BEW, and messing around w/ my mini that is.

These measurements are from my FV25HP -

I am measuring the Center, the xover is @ 80, hence the giant dip @ 80hz.

Anyhow - the green line is before Audy and the Red is after Audy. Seems it did a pretty good job but about 30-50hz there is a pretty big dip I'd like to clean up.

Oh, and this is with my sub in a new position as well - about 10 feet behind me. Before I had it in the front left corner (about 6 feet away - was loud, but maybe a bit too much in your face and the measurements left much to be desired.) and directly behind me (super awesome TR, but took away from the movies itself and did not pressurize the room AT ALL).

But now that it's behind, I think I'm losing a bit of "punch" in the volume dept but it spreads throuhught the room a lot more evenly and even pressurizes it some, even w/ an open floor plan.

Anyhow, going to look into correcting this now w/ the Mini, wish me luck!
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post #27929 of 28192 Old 09-22-2019, 05:04 PM
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Originally Posted by javan robinson View Post

I am measuring the Center, the xover is @ 80, hence the giant dip @ 80hz.
Why do you think the crossover is causing the dip? Did you change the crossover, and did the dip move?

Regardless, a 20dB suck-out from 50Hz to 100Hz must be audible, and suggests you have yet to find the best placement for the sub. Of course, if you really want to improve things, additional subs would be the way to go.

And for future presentation of your measurements, show only 15Hz to 300Hz, which would make the results much easier to analyze.
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post #27930 of 28192 Old 09-22-2019, 07:08 PM
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Quote:
Originally Posted by AustinJerry View Post
Why do you think the crossover is causing the dip? Did you change the crossover, and did the dip move?

Regardless, a 20dB suck-out from 50Hz to 100Hz must be audible, and suggests you have yet to find the best placement for the sub. Of course, if you really want to improve things, additional subs would be the way to go.

And for future presentation of your measurements, show only 15Hz to 300Hz, which would make the results much easier to analyze.
hey, yeah when I had it on Output 4 (just the sub, right?) that dip @ 80 was not there. Sorry I did not take screenshots or save those measurements but I can measure again.

The dip is anywhere from 10-20db depending on how you look at it lol, but I'm happy for now. I keep waiting on what Tom is cooking up over @ PSA for my next purchase..!

Anyways - this is the first time i'm hooking up the Mini DSP hd. I hooked it up, pulled some levers, undid the levers (just input some numbers on gain in the 20hz realm but think I did it wrong so I reset it), but my question is - am I supposed to have the mini in the chain when I'm running REW?

Just took some measurements and they're looking way out of line with what I had last night.

What is this craziness?

Once I get the mini working properly - will I see my current subwoofers frequency response in the Mini DSP program, so I will be able to adjust peaks and nulls respectively while seeing my FR response in real time?

Or

Will I be looking at the graph in REW, and then making adjustments in the Mini dsp software and then re-measuring with REW , to see if the specific "improvements" took?

thanks!

Note: again - this FR attached was w/ the Mini in the chain. It did NOT look like that earlier. I hope I didn't break anything! :0
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