REW subwoofer alignment Video using MiniDSP complete walk through! - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 254 Old 10-10-2019, 01:50 PM - Thread Starter
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REW subwoofer alignment Video using MiniDSP complete walk through!

So after helping dozens of guys align subs on a facebook page I moderate peer pressure has won and I made a video on it. The channel was started really just to make this one video but I decided to cover everything. Here's the REW sub alignment walk through for those that may be interested.


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post #2 of 254 Old 10-10-2019, 09:55 PM
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Originally Posted by cdy2179 View Post
So after helping dozens of guys align subs on a facebook page I moderate peer pressure has won and I made a video on it. The channel was started really just to make this one video but I decided to cover everything. Here's the REW sub alignment walk through for those that may be interested.

https://www.youtube.com/watch?v=_A6gPCczhuU
Thank you so much for doing this!
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post #3 of 254 Old 10-11-2019, 01:13 PM
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post #4 of 254 Old 10-11-2019, 03:15 PM
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Quote:
Originally Posted by cdy2179 View Post
So after helping dozens of guys align subs on a facebook page I moderate peer pressure has won and I made a video on it. The channel was started really just to make this one video but I decided to cover everything. Here's the REW sub alignment walk through for those that may be interested.

https://www.youtube.com/watch?v=_A6gPCczhuU
Very well done and excellent job of showing steps in detail. Have you done anything similar for impulse response?
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post #5 of 254 Old 10-13-2019, 08:53 AM
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Quote:
Originally Posted by cdy2179 View Post
So after helping dozens of guys align subs on a facebook page I moderate peer pressure has won and I made a video on it. The channel was started really just to make this one video but I decided to cover everything. Here's the REW sub alignment walk through for those that may be interested.

https://www.youtube.com/watch?v=_A6gPCczhuU
This is awesome on so many levels! thanks so much for making the videos. I watched this one (Episode 7) and left a comment with some questions that you could hopefully answer. Then I went back to watch all the videos beginning with Episode 1.

Great job!
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post #6 of 254 Old 10-15-2019, 08:32 AM - Thread Starter
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Thanks Guys.

as for impulse no I've always done sweeps as it verifies placement and can look at other seats where as impulse doesn't. Also once two subs are aligned the virtual sub would be what sub 3 is aligned to. I just recently played with impulse but found it lacking and i like to work with a representation of what is heard.
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post #7 of 254 Old 10-15-2019, 02:38 PM
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Thanks a lot for this.

Regarding the gain matching, is it necessary to go through that whole process if you have two identical subs? Could you not just set the gain to the same position on each sub and call it a day?
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post #8 of 254 Old 10-15-2019, 02:43 PM - Thread Starter
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Thanks a lot for this.

Regarding the gain matching, is it necessary to go through that whole process if you have two identical subs? Could you not just set the gain to the same position on each sub and call it a day?
Yeah I think i mention that but may not have. It still wouldn't hurt to verify but they should have the same output if the gain knob is in the same position. If they were heavy I'd probably just set the gains the same and roll on!
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post #9 of 254 Old 10-15-2019, 02:49 PM
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Originally Posted by cdy2179 View Post
Yeah I think i mention that but may not have. It still wouldn't hurt to verify but they should have the same output if the gain knob is in the same position. If they were heavy I'd probably just set the gains the same and roll on!
Thanks, I haven't gotten past the the first few minutes yet (where you mention gain matching). I used REW many years ago for a single sub and don't really remember what I did/had to set in REW, so I am sure this video is going to come in very handy.

Really appreciate the effort you put to do this.
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post #10 of 254 Old 10-15-2019, 02:53 PM - Thread Starter
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Originally Posted by pheare View Post
Thanks, I haven't gotten past the the first few minutes yet (where you mention gain matching). I used REW many years ago for a single sub and don't really remember what I did/had to set in REW, so I am sure this video is going to come in very handy.

Really appreciate the effort you put to do this.
You're welcome. Hope you find it helpful.
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post #11 of 254 Old 10-15-2019, 04:13 PM
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Just a heads up, in your video you say you need to purchase the miniDSP 2x4 control plug-in separately. According to the miniDSP 2x4 HD product page, the plugin is included with purchase.
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post #12 of 254 Old 10-15-2019, 05:10 PM
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Hey. So I have just gotten to the point where you have aligned the 2 subs. Will watch the rest later.

Regarding the miniDSP, In a two sub setup, I am a little confused as to its purpose vs. Audyssey (version that can calibrate 2 subs separately) - maybe you get into this later in the video? Since you leave the miniDSP connected after setup, I guess you would never use the second sub output on the receiver? Or should both minidsp inputs be used with receivers that can distinguish between the individual subs?

Does Audyssey bugger up the work done using REW?

One suggestion: given the length of the the video, it would be nice if you put time stamps in the description. i.e. umik purchase xx:xx, minidsp purchase xx:xx, calibrate sub 1 xx:xx, etc. Though, I know this would be a lot more work and you have probably had enough already.

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post #13 of 254 Old 10-16-2019, 08:18 AM - Thread Starter
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Originally Posted by pheare View Post
Hey. So I have just gotten to the point where you have aligned the 2 subs. Will watch the rest later.

Regarding the miniDSP, In a two sub setup, I am a little confused as to its purpose vs. Audyssey (version that can calibrate 2 subs separately) - maybe you get into this later in the video? Since you leave the miniDSP connected after setup, I guess you would never use the second sub output on the receiver? Or should both minidsp inputs be used with receivers that can distinguish between the individual subs?

Does Audyssey bugger up the work done using REW?

One suggestion: given the length of the the video, it would be nice if you put time stamps in the description. i.e. umik purchase xx:xx, minidsp purchase xx:xx, calibrate sub 1 xx:xx, etc. Though, I know this would be a lot more work and you have probably had enough already.

Everything you asked is explained in the video. Why we only use one sub out even when 2 are available is mentioned several times and I also show how to setup minidsp routing.

Yeah I have some serious time in that video.. I have over 20 hours in it total. As I mention in the video I have links in the description for everything you'll need. Yes it's a little long but if you want to learn to set everything up that little bit of time spent watching it will save you days fiddling and guessing and honestly many just give up.
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post #14 of 254 Old 10-16-2019, 03:58 PM
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Originally Posted by cdy2179 View Post
Everything you asked is explained in the video. Why we only use one sub out even when 2 are available is mentioned several times and I also show how to setup minidsp routing.

Yeah I have some serious time in that video.. I have over 20 hours in it total. As I mention in the video I have links in the description for everything you'll need. Yes it's a little long but if you want to learn to set everything up that little bit of time spent watching it will save you days fiddling and guessing and honestly many just give up.
Hi,

I watched the entire video, mostly - I admittedly 10-second skipped through a lot of the 3rd and 4th sub setup. So maybe I missed it, but the only place I could find you speaking about the one input is about 18 minutes in when you talk about how input 2 may be enabled by default. And there was no reason stated why input 2 would not be used. I suspect it is because by the time you are done, you have set up the proper delays with miniDSP and are basically treating all subs as a single unit, so no need for Audyssey to treat the subs differently?

Regarding the EQ stuff - if one is happy with/uses Dynamic EQ (I have a Denon x4500), is it necessary to have REW/miniDSP do the EQing? I think you mentioned your receiver didn't have the latest version of Dynamic EQ (or something like that) and that was why you didn't use Dynamic EQ? Wasn't clear to me if it should be an either-or for the EQ.
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post #15 of 254 Old 10-16-2019, 04:48 PM - Thread Starter
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Hi,

I watched the entire video, mostly - I admittedly 10-second skipped through a lot of the 3rd and 4th sub setup. So maybe I missed it, but the only place I could find you speaking about the one input is about 18 minutes in when you talk about how input 2 may be enabled by default. And there was no reason stated why input 2 would not be used. I suspect it is because by the time you are done, you have set up the proper delays with miniDSP and are basically treating all subs as a single unit, so no need for Audyssey to treat the subs differently?

Regarding the EQ stuff - if one is happy with/uses Dynamic EQ (I have a Denon x4500), is it necessary to have REW/miniDSP do the EQing? I think you mentioned your receiver didn't have the latest version of Dynamic EQ (or something like that) and that was why you didn't use Dynamic EQ? Wasn't clear to me if it should be an either-or for the EQ.
You may wanna watch it again..

At 10 minutes I explain why one input it is used and why we don't let the AVR have control of more than one output. Your assumption as to why is correct but it's explained for the first time at that point in the video.

As for dynamic Eq I explain during the eq section how to eq a manual house curve when you don't want to use room correction eq and a loudness compensation and how to eq when using room correction eq or dynamic eq. As mentioned in the video You should be using a house curve either manual or loudness compensation like dynamic eq. If you use audyssey at all or any room correction eq that will remain on you need to eq to a flat target in REW. In the video I explain why.
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post #16 of 254 Old 10-16-2019, 05:11 PM
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Ahhh.

I remember seeing that at the 10 minute mark the first time I watched. Couldn’t find it again when I was sort of skipping through looking for it again.

I will have to rewatch the EQ section again. Too much info (in a good way) for a single viewing for someone who has not seen this stuff before.

Thanks again for making this.
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post #17 of 254 Old 10-17-2019, 04:47 AM - Thread Starter
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Ahhh.

I remember seeing that at the 10 minute mark the first time I watched. Couldn’t find it again when I was sort of skipping through looking for it again.

I will have to rewatch the EQ section again. Too much info (in a good way) for a single viewing for someone who has not seen this stuff before.

Thanks again for making this.
Totally understand. I'm the worlds worst about skimming through stuff and missing stuff then putting my foot in my mouth. It is a lot of info. For a few years I've been walking people through this over Messenger. You can imagine how painful that was for me and the guy trying to learn without a video to follow.
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post #18 of 254 Old 10-17-2019, 08:07 AM
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In a 2 sub situation, assuming one has used REW to determine the best location for each sub, I have a question:

If a guy has a receiver with Audyssey XT32 - where each sub is configured separately, doesn't the Audyssey routine determine the proper delays and whether to invert or not?

I am trying to understand if, for aligning subs, miniDSP provides a significant benefit over just using Audyssey XT32?

I get with miniDSP you can make changes on the fly and immediately see the impact of those changes via REW (which is no doubt beneficial), but after all is said and done, would one typically net out to basically the same end-result between miniDSP and XT32 for sub alignment?
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post #19 of 254 Old 10-17-2019, 01:37 PM - Thread Starter
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Originally Posted by pheare View Post
In a 2 sub situation, assuming one has used REW to determine the best location for each sub, I have a question:

If a guy has a receiver with Audyssey XT32 - where each sub is configured separately, doesn't the Audyssey routine determine the proper delays and whether to invert or not?

I am trying to understand if, for aligning subs, miniDSP provides a significant benefit over just using Audyssey XT32?

I get with miniDSP you can make changes on the fly and immediately see the impact of those changes via REW (which is no doubt beneficial), but after all is said and done, would one typically net out to basically the same end-result between miniDSP and XT32 for sub alignment?
With two subs only yes xt32 is an option. It doesn't always get it right, it also won't say hey sub 2 needs to be moved to fix that null at sub one. Room correction uses impulse to align subs and isn't as accurate especially with multiple seats and once you get more than two subs you're in minidsp territory for sure.

Bottom line, If placement is good xt32 often does fine aligning dual subs for one row but it needs to be verified via measurements and also as mentioned in ep 7 you need to verify main to sub alignment too.
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post #20 of 254 Old 10-17-2019, 01:56 PM
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Thanks.

Now that I've removed my back row of seating (and riser) and my single row now only has 2 seats (instead of 4), think I will re-figure out the proper sub placement with REW and then use XT32 and see what happens. MiniDSP would be nice, but at $300 CAD, would be nice if I could get away without it and put that money towards dual 15s.
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post #21 of 254 Old 10-17-2019, 09:22 PM
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@cdy2179 , great job with video. Watched till 40 mins. A few points
1 - Always better to name your measurements. When you took measurement for first sub on front left, name that measurement Front Left instead of Sep 25. This will become very handy when you open the measurements sometime later.
2 - I saw that when you were aligning your subs, you did it manually. You don't have to do that anymore with REW. When you measure, you can use REW new feature called "Impulse Response Calculation" under Analysis tab. Select "Use acoustic timing reference" and when you are on Measurement tab, select your left speaker as a timing reference. Now when you take measurement, you will hear a squeaky sound followed by your regular measurement tone. Take 1 reading of each sub. Then use Overlay Window and go to impulse screen. There you'll see the impulse response of both subs. Zoom into the first peak of response for better viewing (Press Ctrl Key and the Right click and drag a window around the peak and then double click on the highlighted area). Once zoomed in, you'll see two different peaks. Using your mouse go to the peak of first impulse. Then press the CTRL button on keyboard and keep it pressed. Press right mouse button and keep it pressed and drag mouse to the next peak of other response. Once you do that, REW will draw a box and will also show the distance b/w the two peaks and also the difference in ms. That's the exact ms number you need to put in minidsp delay. Its calculated to precision.

Step 2 might seem a bit tedious but once you know how to do it, its real quick way to figure out the delay. Also, using the impulse response, you can easily determine if you have to inverse the phase of a sub. If the first peak of subs don't face the same direction, you need to invert one of the sub.
Hope this helps.
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post #22 of 254 Old 10-18-2019, 04:46 AM - Thread Starter
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Originally Posted by harrisu View Post
@cdy2179 , great job with video. Watched till 40 mins. A few points
1 - Always better to name your measurements. When you took measurement for first sub on front left, name that measurement Front Left instead of Sep 25. This will become very handy when you open the measurements sometime later.
2 - I saw that when you were aligning your subs, you did it manually. You don't have to do that anymore with REW. When you measure, you can use REW new feature called "Impulse Response Calculation" under Analysis tab. Select "Use acoustic timing reference" and when you are on Measurement tab, select your left speaker as a timing reference. Now when you take measurement, you will hear a squeaky sound followed by your regular measurement tone. Take 1 reading of each sub. Then use Overlay Window and go to impulse screen. There you'll see the impulse response of both subs. Zoom into the first peak of response for better viewing (Press Ctrl Key and the Right click and drag a window around the peak and then double click on the highlighted area). Once zoomed in, you'll see two different peaks. Using your mouse go to the peak of first impulse. Then press the CTRL button on keyboard and keep it pressed. Press right mouse button and keep it pressed and drag mouse to the next peak of other response. Once you do that, REW will draw a box and will also show the distance b/w the two peaks and also the difference in ms. That's the exact ms number you need to put in minidsp delay. Its calculated to precision.

Step 2 might seem a bit tedious but once you know how to do it, its real quick way to figure out the delay. Also, using the impulse response, you can easily determine if you have to inverse the phase of a sub. If the first peak of subs don't face the same direction, you need to invert one of the sub.
Hope this helps.
thanks!

I do normally label them and I do mention it in the video and explain it'll help them keep up with whats what.

I have played with impulse and do like it and yes it does really help to determine if phase should be reversed. Impulse Is timing based on one position and doesn't verify other seats or rows which I mention in the video. It also doesn't confirm sub placement is good and it doesn't look at the actual response. Also once two subs are aligned the the third sub is aligned to their virtual sub so timing of the 3rd sub and those proceeding it aren't always right. For instance in my room impulse wants my rear subs to have 10ms or so of delay but with sweeps I get negative summation when thats done. The front subs which I align first it does fine. I just find SPL graphs much more thorough and it's also the method used by Mark Seaton and many others in pro HT room tuning although some will use RTA and have mic arrays they still align off the response of course I'm sure some use impulse too.

That said I may do a video on it to help guys get the delay faster and then confirm with the response and tweak it for any similarity issues at other seats. Of course they'd have to confirm placement first using spl graphs.

Most guys watching the video this is all new so they're getting hammered with a lot of new stuff.
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post #23 of 254 Old 10-18-2019, 11:26 AM
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Thanks for the video, very informative and well explained!
I just tried this for 2 subs and this was the result:
Click image for larger version

Name:	alligned-sub-only.png
Views:	120
Size:	36.3 KB
ID:	2629040

So not that bad I was thinking. However, this was of course without my front speakers, and with my AVR set to 200Hz crossover (which is the max, to kind of "disable" the crossover during alignment, not sure if this is the way to go or not).
When I enable my speakers, still 200Hz crossover, this is the result:
Click image for larger version

Name:	alligned-sub+fronts-200hzX.png
Views:	104
Size:	33.9 KB
ID:	2629038
And after changing crossover to 80Hz:
Click image for larger version

Name:	alligned-sub+fronts-80hzX.png
Views:	118
Size:	38.3 KB
ID:	2629036

So isolated the subs are fine, but when adding the other speakers it's all messed up again
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post #24 of 254 Old 10-18-2019, 12:16 PM - Thread Starter
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Thanks for the video, very informative and well explained!
I just tried this for 2 subs and this was the result:
Attachment 2629040

So not that bad I was thinking. However, this was of course without my front speakers, and with my AVR set to 200Hz crossover (which is the max, to kind of "disable" the crossover during alignment, not sure if this is the way to go or not).
When I enable my speakers, still 200Hz crossover, this is the result:
Attachment 2629038
And after changing crossover to 80Hz:
Attachment 2629036

So isolated the subs are fine, but when adding the other speakers it's all messed up again
Nice response.

It looks like you just have negative summation at the crossover point. Room correction doesn't always get this right. To do it manually check out this link here. Now keep in mind as you cross to the main you're crossing to a single source of bass so the response will not be as nice as you have with your subs. You just get the best summation you can to verify the sub distance is correct.

https://www.avsforum.com/forum/155-d...ow-thread.html





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post #25 of 254 Old 10-18-2019, 12:21 PM
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thanks!

I do normally label them and I do mention it in the video and explain it'll help them keep up with whats what.

I have played with impulse and do like it and yes it does really help to determine if phase should be reversed. Impulse Is timing based on one position and doesn't verify other seats or rows which I mention in the video. It also doesn't confirm sub placement is good and it doesn't look at the actual response. Also once two subs are aligned the the third sub is aligned to their virtual sub so timing of the 3rd sub and those proceeding it aren't always right. For instance in my room impulse wants my rear subs to have 10ms or so of delay but with sweeps I get negative summation when thats done. The front subs which I align first it does fine. I just find SPL graphs much more thorough and it's also the method used by Mark Seaton and many others in pro HT room tuning although some will use RTA and have mic arrays they still align off the response of course I'm sure some use impulse too.

That said I may do a video on it to help guys get the delay faster and then confirm with the response and tweak it for any similarity issues at other seats. Of course they'd have to confirm placement first using spl graphs.

Most guys watching the video this is all new so they're getting hammered with a lot of new stuff.
time for me to watch the rest of the video then . Thx for sharing info. I am currently building two Devastators which makes my current 2 Mini Marty spare. I think I might move them to front and the your video will be a spot on experimental tool since I'll have 4 subs in a sealed rectangular dedicated TH room 23x12x8 .
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post #26 of 254 Old 10-18-2019, 12:45 PM - Thread Starter
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time for me to watch the rest of the video then . Thx for sharing info. I am currently building two Devastators which makes my current 2 Mini Marty spare. I think I might move them to front and the your video will be a spot on experimental tool since I'll have 4 subs in a sealed rectangular dedicated TH room 23x12x8 .
Here's the compilation I made which led to the video.

https://www.avsforum.com/forum/155-d...l#post46473737

You'll see Harmon studies is linked and you may find that interesting. If you watch the Home Theater Geeks video also linked notice 4 corner loaded subs is also one of Grimani's favorite.

Watch out! The Devastator can do some serious damage!
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Originally Posted by cdy2179 View Post
Here's the compilation I made which led to the video.

https://www.avsforum.com/forum/155-d...l#post46473737

You'll see Harmon studies is linked and you may find that interesting. If you watch the Home Theater Geeks video also linked notice 4 corner loaded subs is also one of Grimani's favorite.

Watch out! The Devastator can do some serious damage!
Oh yeah. Running them 9dB hot and they can bring some scary stuff . I'll have 2nd one done tonight. Once I get home, just need to put the driver in and wire it and see how it goes. Based on my analysis, having a sub in each back corners gives flat response with 2-3dB from 27-100Hz at MLP. 2nd seat though suffers and having a sub on the front is the only way to make that go smooth.
Just visited the link you provided (thx for that). I need to understand that excel file with room modes. Wanted to see what can be done to remove that 27Hz suck up I have at MLP. Well, I know what to do but wanted to replicate it in excel file to see how accurate it is. My room is 23Lx12Wx8H. Seats are 65" from back wall. So wanted to see how the modes are playing.
Having a sub on the front takes care of the suck up. Front of room sub has crazy gain below 30Hz but bad above 30Hz. Back of room has very good gain above 30Hz and bad below. Combining front and back can give a very smooth response but it bothers me that I'm loosing a whole sub to get 30Hz and below smoothened out .
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Oh yeah. Running them 9dB hot and they can bring some scary stuff . I'll have 2nd one done tonight. Once I get home, just need to put the driver in and wire it and see how it goes. Based on my analysis, having a sub in each back corners gives flat response with 2-3dB from 27-100Hz at MLP. 2nd seat though suffers and having a sub on the front is the only way to make that go smooth.
Just visited the link you provided (thx for that). I need to understand that excel file with room modes. Wanted to see what can be done to remove that 27Hz suck up I have at MLP. Well, I know what to do but wanted to replicate it in excel file to see how accurate it is. My room is 23Lx12Wx8H. Seats are 65" from back wall. So wanted to see how the modes are playing.
Having a sub on the front takes care of the suck up. Front of room sub has crazy gain below 30Hz but bad above 30Hz. Back of room has very good gain above 30Hz and bad below. Combining front and back can give a very smooth response but it bothers me that I'm loosing a whole sub to get 30Hz and below smoothened out .
I plan to shoot room modes and seating this weekend. Subs placed just right can do some magic on room modes which helps open up more good spots for seating.

At 5'5 back you have a null at 35hz. If the MLP is in the middle of the room you have a null at 47hz. You should be able to fix the 35hz null by placing one sub 1/3 along side wall. A sub on each side wall at those points will put the virtual sub in the center and also kill the modes you have in the middle too. Placed on one wall at 1/3 and 2/3 on the other would place it dead middle of the room and kill more modes.

Last edited by cdy2179; 10-18-2019 at 02:26 PM.
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post #29 of 254 Old 10-22-2019, 12:52 PM
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Thanks for the video, very informative and well explained!
I just tried this for 2 subs and this was the result:
Attachment 2629040

So not that bad I was thinking. However, this was of course without my front speakers, and with my AVR set to 200Hz crossover (which is the max, to kind of "disable" the crossover during alignment, not sure if this is the way to go or not).
When I enable my speakers, still 200Hz crossover, this is the result:
Attachment 2629038
And after changing crossover to 80Hz:
Attachment 2629036

So isolated the subs are fine, but when adding the other speakers it's all messed up again
This is basically the next step of the subwoofer optimization after you get the subs working together well at the listening position. This is also one aspect where having a single subwoofer output to the external EQ makes adjustment much easier, as you can work with a single distance/delay setting. Of course after you set this up, remember that if in listening you decide to apply significant gain to the subwoofer (nothing wrong with that if it sounds appropriate), you want to come back and double check the crossover integration as the relative levels through the crossover can change significantly.
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post #30 of 254 Old 10-22-2019, 01:22 PM
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Thanks

cdy2179, Thanks for pulling this and your other tuning how-to videos together. Over the course of this year, had made multiple attempts to tune my subs with miniDSP 2x4 HD with mixed results. This past weekend, after reviewing your Episode 7 I have my best results to date. Thanks for taking the time to put this together. Well Done!
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