Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 710 - AVS Forum | Home Theater Discussions And Reviews
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post #21271 of 28212 Old 01-28-2017, 12:46 PM
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Originally Posted by AustinJerry View Post
So, would you say that these results are reasonable or not?
I would, but I don't consider myself anything of an authority in these matters.
I guess a good target would be 25% or less at 20Hz, less than 1% starting at about 50Hz.
I guess my question should be "Can you hear distortion of 25% at 20Hz or 1% distortion at 50Hz?"
"You" addressing the world at large, of course.
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post #21272 of 28212 Old 01-28-2017, 12:56 PM
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Originally Posted by MBrown2020 View Post
What do you mean by time-aligned? Audyssey was completed using the pro kit before I started tweaking the distances of the subs and that was the smoothest I could get it.
You have three subs on two sub outputs. I don't recall, but if you have two equidistant subs on one output and the third sub on the second output, then Audyssey has time-aligned the three subs properly. Is this the case?
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post #21273 of 28212 Old 01-28-2017, 12:59 PM
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Audibility is a difficult one. However the more pertinent point is that if your sub is genuinely producing 25% distortion then you are driving it well beyond what it can handle and it (distortion) will escalate extremely quickly if it is driven any harder. ie you need to back off

The question is whether it is a room artifact or it is your sub begging for mercy
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post #21274 of 28212 Old 01-28-2017, 01:01 PM
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Originally Posted by LastButNotLeast View Post
I would, but I don't consider myself anything of an authority in these matters.
I guess a good target would be 25% or less at 20Hz, less than 1% starting at about 50Hz.
I guess my question should be "Can you hear distortion of 25% at 20Hz or 1% distortion at 50Hz?"
"You" addressing the world at large, of course.
Michael
IMO, the real question is what is producing that 20Hz tone? Clearly not the type of music content that I listen to. Perhaps a special effect in a movie? If yes, then what does an exploding bomb with 25% distortion sound relative to one with only 10% distortion?

I my case, hearing something at 20Hz is so rare that the distortion figures I measured don't bother me at all.
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post #21275 of 28212 Old 01-28-2017, 01:02 PM
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Originally Posted by 3ll3d00d View Post
Audibility is a difficult one. However the more pertinent point is that if your sub is genuinely producing 25% distortion then you are driving it well beyond what it can handle and it (distortion) will escalate extremely quickly if it is driven any harder. ie you need to back off

The question is whether it is a room artifact or it is your sub begging for mercy
Thanks for the valid points. But as I said, I'm not losing any sleep at the present time.
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post #21276 of 28212 Old 01-28-2017, 01:21 PM
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Originally Posted by AustinJerry View Post
You have three subs on two sub outputs. I don't recall, but if you have two equidistant subs on one output and the third sub on the second output, then Audyssey has time-aligned the three subs properly. Is this the case?
Yes I have 2 equidistant subs on output 1 and the back sub on output 2. They all have same driver and amp so I set all 3 to the same gain level (approx. 10oclock) and ran audyssey. The trim levels were set to -10.5 for subs 1 and -6.5 for back sub 2. I then set both trims to -8.5 (halved them). Is that correct? I attached pictures of the placements front and rear.
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post #21277 of 28212 Old 01-28-2017, 01:27 PM
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Originally Posted by MBrown2020 View Post
Yes I have 2 equidistant subs on output 1 and the back sub on output 2. They all have same driver and amp so I set all 3 to the same gain level (approx. 10oclock) and ran audyssey. The trim levels were set to -10.5 for subs 1 and -6.5 for back sub 2. I then set both trims to -8.5 (halved them). Is that correct? I attached pictures of the placements front and rear.
I would not adjust the trims. The two front subs have a lower trim setting because two subs should be ~6dB higher output than one sub. Audyssey is essentially gain-matching the levels across the two sub outputs. If you change the trims, you have negated what Audyssey did, and it probably will sound worse. Try restoring the trim values and measuring the results.
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post #21278 of 28212 Old 01-28-2017, 03:20 PM
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Originally Posted by AustinJerry View Post
Thanks for the valid points. But as I said, I'm not losing any sleep at the present time.
Then this thread is no longer serving its intended purpose.

Michael

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post #21279 of 28212 Old 01-28-2017, 04:04 PM
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Quote:
Originally Posted by AustinJerry View Post
I would not adjust the trims. The two front subs have a lower trim setting because two subs should be ~6dB higher output than one sub. Audyssey is essentially gain-matching the levels across the two sub outputs. If you change the trims, you have negated what Audyssey did, and it probably will sound worse. Try restoring the trim values and measuring the results.
I read posts from user craig john about gain matching the subs, he takes the trims from sub1 and sub2 and halves them. So you think I should just leave the audyssey trims alone? Wouldn't that put more strain on the back single sub as they will no longer all be gain matched?
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post #21280 of 28212 Old 01-28-2017, 04:20 PM
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Originally Posted by MBrown2020 View Post
I read posts from user craig john about gain matching the subs, he takes the trims from sub1 and sub2 and halves them. So you think I should just leave the audyssey trims alone? Wouldn't that put more strain on the back single sub as they will no longer all be gain matched?
There are many theories. The only way to know for sure is to try the different ways, measure the results, and decide for yourself. Nothing beats doing the detective work yourself.

In my case, I rarely listen at levels that are likely to push any of my subs over the edge. Your listening habits may be different.
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post #21281 of 28212 Old 01-28-2017, 04:31 PM
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Originally Posted by AustinJerry View Post
There are many theories. The only way to know for sure is to try the different ways, measure the results, and decide for yourself. Nothing beats doing the detective work yourself.

In my case, I rarely listen at levels that are likely to push any of my subs over the edge. Your listening habits may be different.
Ok, thanks. I usually listen around -5 to -8 for movies, so I like it fairly loud. I have never heard these subs really ask for mercy so I am comfortable with what audyssey does. I read they have some sort of built-in limiters to protect them from over driving anyway. My living room is 11.5 x 22 x 8 = 1840 ft2, so 3 subs should not be strained. Thanks for your help! The wife and dogs are back so I have to wait till next Saturday to do some more measurements. I will update then.
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post #21282 of 28212 Old 01-28-2017, 04:31 PM
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Originally Posted by MBrown2020 View Post
I read posts from user craig john about gain matching the subs...
I should add that I have nothing but the highest respect for Craig and what he has accomplished with sub integration.

However, I would like to point out a significant difference between what you are doing, and my configuration. I have four subs connected to a MiniDSP 2x4, which in turn is connected to a SINGLE sub output. So I gain-match my subs carefully, use the 2x4 to time align them, and then my room calibration software (Dirac Live) establishes a single trim level for the combined sub channel. So, I don't have to follow Craig's guideline, and my subs always stay in a gain-matched state.

If you were so inclined, you could do the same thing. It is the approach described in the guide linked in my sig. BTW, when I first purchased the 2x4, I went through a rigorous exercise to see if connecting subs to two outputs on the AVR produced better results than consolidating the subs onto one output. My tests revealed that I was able to achieve similar results using the 2x4 and only one sub output. So if you decide to try this, feel confident that you will lose nothing with respect to overall sub performance.
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post #21283 of 28212 Old 01-28-2017, 04:49 PM
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Quote:
Originally Posted by AustinJerry View Post
I should add that I have nothing but the highest respect for Craig and what he has accomplished with sub integration.

However, I would like to point out a significant difference between what you are doing, and my configuration. I have four subs connected to a MiniDSP 2x4, which in turn is connected to a SINGLE sub output. So I gain-match my subs carefully, use the 2x4 to time align them, and then my room calibration software (Dirac Live) establishes a single trim level for the combined sub channel. So, I don't have to follow Craig's guideline, and my subs always stay in a gain-matched state.

If you were so inclined, you could do the same thing. It is the approach described in the guide linked in my sig. BTW, when I first purchased the 2x4, I went through a rigorous exercise to see if connecting subs to two outputs on the AVR produced better results than consolidating the subs onto one output. My tests revealed that I was able to achieve similar results using the 2x4 and only one sub output. So if you decide to try this, feel confident that you will lose nothing with respect to overall sub performance.
So you were able to get similar results using the 2x4 vs the 2 sub outs on the AVR(8802a). If that is the case I would like to try to get things working with 1 less piece of hardware to deal with, or is the 2x4 something to make it easier?
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post #21284 of 28212 Old 01-28-2017, 05:04 PM
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Originally Posted by MBrown2020 View Post
So you were able to get similar results using the 2x4 vs the 2 sub outs on the AVR(8802a). If that is the case I would like to try to get things working with 1 less piece of hardware to deal with, or is the 2x4 something to make it easier?
Keep in mind that I had no choice. I use the MiniDSP 88A for room correction, and it requires the subs to be consolidated on a single input.

I made sure that consolidating the subs would result in an equally effective solution before I purchased the 88A and switched from Audyssey to Dirac Live. If you want to stay with Audyssey, there is no reason you would add the 2x4 at this time. As I recommended earlier, try the various options you have now--I am sure you will find the sweet spot. The only reason why I mentioned this was to show why I am not following Craig's recommendation.
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post #21285 of 28212 Old 01-28-2017, 10:06 PM
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Originally Posted by AustinJerry View Post
All the mentioned graphs except subs by themselves, 15-300Hz, no smoothing, room correction off.

And you might explain what caused you to move the subs from their original location to stacked in the corner. That doesn't sound like an ideal location, and why stack them?
Hi Austin,

Ill post these graphs tonight. It's been awhile since my last msg on here regarding this lol....

I have already gain matched my subs so they are all equally powered now and no signs of clipping on any of the subs even at reference with the subs playing 5db hot ....Finally!...Looks like gain matching definetly fixed the problem as my nearfields were clipping well before the farfield ones all the time.....turns out they were 4 clicks above the farfield subs....it sounds absolutely insane how good it sounds and has tightend up the bass now....where it always sounded abit bloated and over the top before when i ran the subs running hot....now i can run it hot but it still sounds tight as anything.

I ran some sweeps but at around 60hz i got a big null with the CC + All Subs measurement....ill post the graphs tonight and hopefully i can get a time alignment done on my subs with your help using the mini dsp?.....or if you have any other better way of doing it. Im willing to move the subs around....will post pictures of where the subs are situated at the room now

Thanks for the help again and also the guys in the MBM thread
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post #21286 of 28212 Old 01-29-2017, 05:12 AM
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Hi guys,

Here is my mdat file.
All subs had zero delay for this ...I also included individual sub responses with the CC as well but it didnt say it in the measurement titles...so thought i better say that. It was all done on a 80hz crossover. Hope this is OK?

https://www.dropbox.com/s/0ybv4fkv4a...ONSE.mdat?dl=0

Subs are located at

Front Left Corner *under screen wall*
I have 2 Nearfield Subs *flanking to a two seater couches for the front row*
Rear Right Corner *behind the Rear Row*

Cheers,
Kevin
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post #21287 of 28212 Old 01-29-2017, 05:34 AM
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Hi guys,

Here is my mdat file.
All subs had zero delay for this ...I also included individual sub responses with the CC as well but it didnt say it in the measurement titles...so thought i better say that. It was all done on a 80hz crossover. Hope this is OK?

https://www.dropbox.com/s/0ybv4fkv4a...ONSE.mdat?dl=0

Subs are located at

Front Left Corner *under screen wall*
I have 2 Nearfield Subs *flanking to a two seater couches for the front row*
Rear Right Corner *behind the Rear Row*

Cheers,
Kevin
What kind of subs are these? How does the response look like at other locations within the listening area?
Subs to the left and the right of a couch aren't near field. Near field is 1-2ft from ears.

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post #21288 of 28212 Old 01-29-2017, 05:38 AM
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What kind of subs are these? How does the response look like at other locations within the listening area?
Subs to the left and the right of a couch aren't near field. Near field is 1-2ft from ears.
They are Submersives but only the 1000w versions. The NF subs are literally sitting to the right of me... The front row *where I sit* only has two couches.... Left couch has left sub beside it... Right couch has a right sub beside it.

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Originally Posted by buddhamus View Post
They are Submersives but only the 1000w versions. The NF subs are literally sitting to the right of me... The front row *where I sit* only has two couches.... Left couch has left sub beside it... Right couch has a right sub beside it.

Sent from my SM-G900I using Tapatalk
Got a floorplan or picture?

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post #21290 of 28212 Old 01-29-2017, 05:40 AM
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What kind of subs are these? How does the response look like at other locations within the listening area?
Subs to the left and the right of a couch aren't near field. Near field is 1-2ft from ears.
BTW I haven't moved the subs... But can post photos and show where they are situated and maybe u guys can give me some ideas where I can put them. I'm open to moving them around... Will have to post photos tommorow night tho.... I'm in Australia BTW

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post #21291 of 28212 Old 01-29-2017, 06:10 AM
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Originally Posted by buddhamus View Post

I ran some sweeps but at around 60hz i got a big null with the CC + All Subs measurement....ill post the graphs tonight and hopefully i can get a time alignment done on my subs with your help using the mini dsp?.....or if you have any other better way of doing it. Im willing to move the subs around....will post pictures of where the subs are situated at the room now
Yes, two steps are required. First, because the four subs are at different distances from the MLP, the subs need to be time-aligned with each other. Measure the physical distance from the center of the sub dustcap to the spot where your ears are in the MLP and then follow the instructions in the 2x4 guide to enter the appropriate delay. Since physical measurements can be slightly off, you can use REW to fine-tune the delay for smoothest response on the sub channel.

Once the subs are time-aligned with each other, use the sub distance tweak to align the combined sub signal with the mains. When tweaking the sub distance, make sure the tweak is applied to all four subs but the same amount, or you will alter the inter-sub time alignment. The sub distance setting in the AVR is a handy place to make this adjustment.

Happy to hear you are making progress.
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post #21292 of 28212 Old 01-29-2017, 07:38 AM
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Difficulty integrating two different subs

Using REW and a miniDSP 2x4, I have been trying to integrate two subs into my system using AustinJerry’s miniDSP guide. The two subs I am using are a PSA V1500 and a Paradigm PW-2200.

So far, I have not been able to produce a frequency response with the two subs running that is better than what I get when running a single sub, with one exception. On one occasion, with the two subs set-up in specific locations, running both at the same time, after setting proper delays using the Audyssey method, I was able to achieve a very smooth frequency response (the best I’ve had – it didn’t have any major valleys). However, when going through the impulse response step in the guide, it indicated that my subs were out of polarity. Which was surprising to me because the frequency response I was getting was very smooth. If the subs were out of polarity, I would have expected to see a few peaks and/or valleys in the frequency response.

After inverting the polarity of the first sub (as per the guide), it now showed my subs in the same polarity. But this ended up vastly worsening the frequency. By a mile. All of a sudden, I had all sorts of valleys (none of which I had in the previous measurement before reversing the first sub’s polarity). I was surprised at this result because I thought this is the type of graph I might get if my subs were running out-of-phase, not in-phase.

One thing to note is that the PSA has a front-facing port, whereas the Paradigm has a rear-facing port. Could this be contributing to the difficulties I’m having integrating these two?
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post #21293 of 28212 Old 01-29-2017, 07:50 AM
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Using REW and a miniDSP 2x4, I have been trying to integrate two subs into my system using AustinJerry’s miniDSP guide. The two subs I am using are a PSA V1500 and a Paradigm PW-2200.

So far, I have not been able to produce a frequency response with the two subs running that is better than what I get when running a single sub, with one exception. On one occasion, with the two subs set-up in specific locations, running both at the same time, after setting proper delays using the Audyssey method, I was able to achieve a very smooth frequency response (the best I’ve had – it didn’t have any major valleys). However, when going through the impulse response step in the guide, it indicated that my subs were out of polarity. Which was surprising to me because the frequency response I was getting was very smooth. If the subs were out of polarity, I would have expected to see a few peaks and/or valleys in the frequency response.

After inverting the polarity of the first sub (as per the guide), it now showed my subs in the same polarity. But this ended up vastly worsening the frequency. By a mile. All of a sudden, I had all sorts of valleys (none of which I had in the previous measurement before reversing the first sub’s polarity). I was surprised at this result because I thought this is the type of graph I might get if my subs were running out-of-phase, not in-phase.

One thing to note is that the PSA has a front-facing port, whereas the Paradigm has a rear-facing port. Could this be contributing to the difficulties I’m having integrating these two?
I would stick with the smoothest frequency response. In my case, the frequency response was smoother after inverting the polarity.
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post #21294 of 28212 Old 01-29-2017, 04:46 PM
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Hi Jerry:
Thanks for the REW Guide.
I was having a very hard time getting my Lenovo Yoga laptop/ASIO to recognize my UMM-6. I almost tried using a bigger hammer, but that would have been expensive.
I finally figured it out: click on the "Parachute", which is the Restore Defaults button. Haven't had any problems since then. I penciled it in on page 43 of your guide.

BTW, I live not too far away from you, just past New Braunfels, in Garden Ridge.

Rick
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post #21295 of 28212 Old 01-29-2017, 06:34 PM
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I was surprised at this result because I thought this is the type of graph I might get if my subs were running out-of-phase, not in-phase.
Phase is a tricky business. It could be that having your subs in-phase accentuates all the room modes and/or cancellations/reinforcements and that out-of-phase smooths those out. Maybe you could try moving one of the subs to look for a smoother in-phase response. If your room is amenable to it the room simulator in REW might offer some insight into what's going on.

I spent a few days re-reading everything by Geddes et al on AVS and a few other places. AIUI, he actually uses phase variance amongst his subs specifically to flatten the response. Again, AIUI/IIRC, he does not appear to be too concerned with phase in the lower (sub-100Hz) bass because it cannot be heard.

On the other hand, I have traded off some flatness for better impact from my subwoofers by better phase-matching them. Drums sound much more percussive with the subs now.

On the gripping hand, a lot of people like the fatter bass that results from not-in-phase and/or time-aligning subs give.

This is a very subjective hobby for things like that.
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post #21296 of 28212 Old 01-29-2017, 09:43 PM
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Do I still need to use my Newly Purchased UMIK-1 (calibrated) if I am using ARC2 from Anthem?

I noticed there are some quick look features for repeatedly chirping speakers with a test chirp.

The display then gives a response where peaks and nulls are shown for a given microphone location.

I originally purchased the UMIK-1 to use with REW and learn my room before additional HT purchases.

Circumstances led to a purchase of a MRX720 Receiver before I learned or used the UMIK-1, but I still have it.

The microphone that comes with the MRX720 receiver is also calibrated and integrates nicely with the ARC2 room correction software.

So now I am wondering if I still need the UMIK and REW or if I can get the information I need to start adding Absorption from the ARC2 SW.

Any thoughts? Thanks!
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post #21297 of 28212 Old 01-30-2017, 07:16 AM
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Yes, two steps are required. First, because the four subs are at different distances from the MLP, the subs need to be time-aligned with each other. Measure the physical distance from the center of the sub dustcap to the spot where your ears are in the MLP and then follow the instructions in the 2x4 guide to enter the appropriate delay. Since physical measurements can be slightly off, you can use REW to fine-tune the delay for smoothest response on the sub channel.

Once the subs are time-aligned with each other, use the sub distance tweak to align the combined sub signal with the mains. When tweaking the sub distance, make sure the tweak is applied to all four subs but the same amount, or you will alter the inter-sub time alignment. The sub distance setting in the AVR is a handy place to make this adjustment.

Happy to hear you are making progress.
Thanks Austin,

Followed the guide and did all the measurements and calculated all the distances.

Sub 1 - Front Right Corner - 137 inches
Sub2/3 - 2 Subs Nearfield daisy chained - 56 inches
Sub 4 - Rear Left Corner - 118 inches

Difference between the furthest sub was 137 inches and my Nearfield subs were 56 inches....take away 56inches from 137 and we get 81inches.

So 81 divided by 13512 x 1000 gives me - 5.99ms delay for the nearfield subs...which i put into the MiniDSP and I got this....pic attached: Red is before and Green is after....must say its a lot better than before lol. Hope the math is right?

Pic was taken on my phone as I got excited and didnt even think of taking a screenshot lol...........
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post #21298 of 28212 Old 01-30-2017, 07:21 AM
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Im guessing the dips i have atm at 70hz and 90hz will be smaller after Ive ran Audyssey Pro?...if not, ill do the sub distance tweak through the AVR correct? So the subs now time aligned?

Im only using one sub out, so I have one trim setting for all 4 subs...so should be simple to do that.

Is this good enough or can we squeeze out a smoother unequalized response
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post #21299 of 28212 Old 01-30-2017, 07:25 AM
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Quote:
Originally Posted by AustinJerry View Post
Yes, two steps are required. First, because the four subs are at different distances from the MLP, the subs need to be time-aligned with each other. Measure the physical distance from the center of the sub dustcap to the spot where your ears are in the MLP and then follow the instructions in the 2x4 guide to enter the appropriate delay. Since physical measurements can be slightly off, you can use REW to fine-tune the delay for smoothest response on the sub channel.
Jerry, I think it's worth mentioning to those that are new to time-aligning multiple subs that it doesn't always produce the best result. When I was troubleshooting an issue with SubEQ HT and my 2 18's upfront (1/4, 3/4 wall locations equidistant to MLP) with a dual front-firing 12" sub directly behind MLP, the response from SubEQ HT was significantly worse than with no delay at all between subs. As it turned out, combining the response with a Y-adapter and using the sub distance tweak on the combined response was what worked best in my particular situation. Sanjay even noted to me at that time that in his own personal experience, it's about 50/50 with respect to time-aligning vs. not. I've also read in the Submersive thread where Mark Seaton notes every room is different with respect to it.

The good news is that anyone in this thread has likely purchased a mic for use with REW and can measure for themselves!
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post #21300 of 28212 Old 01-30-2017, 07:44 AM
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Originally Posted by buddhamus View Post
Thanks Austin,

Followed the guide and did all the measurements and calculated all the distances.

Sub 1 - Front Right Corner - 137 inches
Sub2/3 - 2 Subs Nearfield daisy chained - 56 inches
Sub 4 - Rear Left Corner - 118 inches

Difference between the furthest sub was 137 inches and my Nearfield subs were 56 inches....take away 56inches from 137 and we get 81inches.

So 81 divided by 13512 x 1000 gives me - 5.99ms delay for the nearfield subs...which i put into the MiniDSP and I got this....pic attached: Red is before and Green is after....must say its a lot better than before lol. Hope the math is right?

Pic was taken on my phone as I got excited and didnt even think of taking a screenshot lol...........
I've asked this before but will try again: what does the response look like at other locations within the listening area? Optimizing a single curve can be counterproductive.

Could you also upload your .mdat to Dropbox or similar?

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
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