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ttocs

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I spent most of the last week dealing with positioning and testing 3 subwoofers as the culmination of previous testing and moving. I'm posting this with the hope it can help others achieve similar results, and this is before using calibration software like Dirac etc.

I've got a pair of 12" Sumiko S.10 subwoofers and an older 10" Rel. I used REW and a miniDSP 2x4HD along with a UMIK-1 microphone for doing this.

The Microphone Crawl
I did NOT do the normal sub-crawl. I did the mic-crawl. I placed my small down-firing subwoofer upside down at the MLP. Then used REW which has a couple valuable tools, RTA and Generator. Generator will play pink noise at whatever range of frequencies you want, and Real Time Analyzer will "record" the noise and make a plot in real time. The reason this works so well is due to the mic being able to "hear" all the frequencies and REW turning that info into something meaningful. I scoped out my entire great room this way. Whilst dangling the mic and swinging it around an area the size of a subwoofer, I recorded for a short time until the curve materialized then stopped, then repeated this in spot after spot after spot, etc. The RTA will record the peaks so when the curve slows down its progress to almost no change then it's time to stop and move on. Over the course of 20 minutes I covered the whole space and didn't have to bend over. Once I saw what was happening in different areas I got a handle on seeing how the curve changes and it became more predictable as time went on.

Once I found all the interesting spots, I put triangle casters under the feet of the heavier subs to be able to move each of them easily. If the sub was on a rug I left the casters on, but if on the wood floor I would remove the casters once in the right area and just shove the sub from there. You could always use rags under the feet to be able to slide the sub around.

Attachment 010012-PLAN is the layout (and this version happens to show the first real successful sub combo). The spots that showed promise from the mic crawl are shown in yellow CAP letters.
The first day of real measurements I tested Positions A with S2 and B with S1, individually, then together. Not great.

The next day I tested all the spots in the dining area and ended up putting S1 in Position D, and kept S2 in Position A, and put S3 in Position C. This wasn't horrible, but had a large dip that I couldn't reduce.

Test day 3. I moved S2 to H and I, and everywhere within 8' of the wall and ended up using H. So this was S1D, S2H, and S3C. This was really great!
Attachment 010012-3-S1D-S2Hinverted-S3C is the result of S1D, S2H, S3C with no PEQ, no crossover, no Dirac or other calibration. In the miniDSP I only used Delay, Inverting S2H, and Subwoofer Gain to adjust.

The day after this result, and after knowing a little more about what can be done to improve things and thus also understand more about what I wanted to get from each subwoofer, I checked a little more and found two more spots that improved upon the previous results: K and L.
Attachment 010031-PLAN shows the new Positions for S2 and S3.
Attachment 010031-S1K-S2Hinverted-S3L is the final plot. This result shows that central peak at about the same level, but all the frequencies below and above have higher output by 2-3dB vs the other plot, and that narrow deep dip is gone.

I found that adjusting the delay can be quite tedious. So I came up with something that got me in the ballpark quicker. I used Generator and RTA while adjusting the delay and looking at the RTA screen. It needs refreshing a few times, but it's really quick doing it this way.
 

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fcel

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I used REW and a miniDSP 2x4HD along with a UMIK-1 microphone for doing this.
I was trying to learn how to use these tools but somehow didn't get very far. Your post about mic-crawl has re-ignited my interest to take another crack at them.

I placed my small down-firing subwoofer upside down at the MLP.
What does MLP stand for?

Correct me if I'm wrong, are you saying you pick a few spot to measure the frequency response and then pick the best response to place your subwoofer? How far apart do you take the measurements?

I will probably have more questions later.
 

ttocs

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I was trying to learn how to use these tools but somehow didn't get very far. Your post about mic-crawl has re-ignited my interest to take another crack at them.

What does MLP stand for?

Correct me if I'm wrong, are you saying you pick a few spot to measure the frequency response and then pick the best response to place your subwoofer? How far apart do you take the measurements?

I will probably have more questions later.
MLP=Main Listening Position

Yeah, these things don't come with really good instructions. I bought the miniDSP back in April, and viewed LOTS of videos on how to use it. I also viewed lots of REW videos. Took a long time for things to sink in.

And yes, I chose to put the subs in the spots that measured best, except for S3, which is not in the best spot, but is instead in a really good compromise. While S3L is not a spot where anyone would be walking, it is visually in a spot that no interior designer would approve. And, S1K is under my dining table, so if I have a large group over for dinner I'll need to move it - so - I am leaving the casters under it since that area has a thick rug so the sub stays put easily.

When I did the mic crawl, I would dangle the mic in a location and swing it around a little while looking at the curve as it's being created. Once the curve had formed, I made a mental image and measured a spot a couple feet away, then repeated this sequence numerous times. When I saw a curve that looked encouraging is when I'd write that down. THEN, after the first pass, I went back to the spots I wrote down and checked which might be the better candidates. It was after this point that I began moving the subwoofers into place to begin actual measurements.

So, it's really a multi-pass situation.
Pass 1: First round of mic crawl.
Pass 2: Best spots of mic crawl.
Pass 3: Measure a sub in each spot to weed out the worst, keep the best.
Pass 4: Start measuring sub combos.

The mic crawl didn't take long. Including setup, taking time to figure out some things, and doing the crawl, probably took about an hour and a half. Moving and measuring one sub in all the different locations took the rest of the day, taking lots of breaks. When the measurements don't work, it's obvious, so this doesn't take long. It's only when things look promising that I tried lots of variations, like rotating the sub, lots of increments from against the wall to 6' from the wall. I kept all the sweeps on the screen to see which direction the peaks and dips were moving. It's all incremental.

I began Pass 4 on Sept. 28 with two subs in Positions A and B: S2A, S1B. Measured each one, then together. Attachment S2A-S1B is both together. That peak is common everywhere in my room.
Sept. 29 was S1D, S2A, and S3C. Big dip that couldn't be reduced.
Sept. 30 I took the day off from subwoofers.
Oct. 1 was a successful day! I moved S1 around a little, then settled on Position K.
Oct. 2 morphed into the wee hours of Oct. 3. Attachment greenS1D-S2H-S3C--blueS1K-S1h-S1C shows the difference between Position D and K. S1K-S2H-S3C is the blue line and improves the lowest frequencies and also the freqs around 100Hz, but also increased a dip in the 90Hz range. Very successful progress so I kept at it and achieved a great outcome once S3 was moved to Position L.

Better interior design considerations could be employed, but would require DSP correction and would work as well as it is expected to work. But, this exercise proves to me that location and determination can have great results without DSP when I'm a form follows function kinda' guy. I'm willing to live amongst the speakers considering that there's already Width speakers in the middle of the room. To me, that's the decor.

I should note something here. I currently am only using the subwoofers for LFE. As such, the Bass Management for the speakers set to Small goes to the Front Left and Right speakers set to Large. The Expressions really have great bass down to just below 20Hz in my room.
 

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fcel

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Thanks ttocs for your detail description of your process. Likewise, I bought the miniDSP 2X4HD and the UMIK-1 microphone about two months ago and have viewed quite a few REW videos but unfortunately I don't have much success with them. I will try again when I got a chance.
 

ttocs

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One thing that greatly helped me was when I was told to use HDMI as the connection from the computer to the processor. duh. That way REW, and miniDSP both know to allow up to 7.1 speaker setup. Before I found out about that I was using a audio interface with extra cables, extra adjustments, lots of frustration.

I use a MacBook Pro and the HDMI works very well. I've heard that the PC users need to use ASIO, which I'm not familiar with.
 

ttocs

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I finally got serious about adding subwoofers to augment the Expressions. Adding stereo stacks of subs is something I've been interested in trying for several years. I've tried to find information on what to expect, how to set them up, etc, but there's simply not much specific info out there. So now it's time to act. So I've been looking at different subwoofers and really wanted to try Rythmik since I've read so many good reviews about their subs. The issue for me has been trying to decipher the info on their web site, as well as getting specific questions answered by phone. It ends up that what they recommended at first is not what they recommended once they understood what I wanted to do, plus some of the confusion was caused when one of them thought I was someone else so the phone conversations conflicted with the emails. My confidence was not great, but I still think they make good products, but I went in a different direction.

So I bought a couple ML Dynamo subs, a 1100X and a 800X. The 800X I was going to keep no matter what as a dedicated Center channel sub for my Motif. The 1100X was to try out. I was keenly interested in a couple features, the fact that they have ARC, and being intrigued with the amount of control via the app. After trying them out for a couple days I got a few more 1100X's so I could finally try the 3 sub stack idea, and have enough for stereo pairs. The app offers a great amount of settings that makes adding a second and third sub into a group pretty easy. I was able to get really good results with a lot less effort than I imagined.

Where the Expressions are located is not ideal, but it's where they must go. So putting subs there is also not ideal, but when there's more than one, and they have lots of tweaking ability, then the results get better with each added sub. The biggest improvement is when the second sub was added. The third sub is such a minor difference it's not worth the expense for me, I get what I want from two. So far it's just been measuring and tweaking for frequency response because I'm waiting for some parts to come tomorrow so I can make the cables I need to make a fully functional pair instead of just one setup. That's when I can do some listening to music.

There's more than one reason for me doing this exercise. First is that I want to find out if the bass can be made to be like it's more encompassing when listening to two channel music by using more drivers. The Expressions do a fine job on their own, but my room is pretty big, so a little help may go a long way. The connection for this is via the High Level Inputs on the subs.

Second is that by adding subwoofers I can, and have, reduced the bass that the amps in the Expressions need to produce. I used both bass controls to blend with the subs. The Mid-Bass switch is in the +2dB position, and the Bass Control knob is at -8dB. So now when I measure the Expression by itself the bass starts slowly rolling off at 150Hz, and by 40Hz it's 16dB lower and flattens out from there on down below 20Hz at that level. So that means the amps are working way less than before, so between say 120Hz and 300Hz they "might" work better? Don't know, just a theory, but the bass being produced by the woofers has got to be less distorted when super low frequencies aren't involved as much, just like when I separated LFE from being mixed with bass management for watching movies and the sound got clearer for all the speakers with bass management.

Third is simply that the Bass Management for all Small speakers for HT usage can go through these four subs via the LFE Inputs and be controlled with settings in the processor. Remember, this is not for LFE, it's Bass Management that's just using the LFE input. The true .1 LFE is going to other subs dedicated just for LFE and nothing else. Whether it will be all four subs, or only two is yet to be determined. Probably this coming weekend is when I'll have the first opportunity to test out the complete system but the subs will still be very new with very few hours on them.

It's been a fun learning experience, with lots more learning yet to come. These Dynamo subs are a lot easier to work with than my other subs.
 
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ttocs

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A lot of change has happened in the background, but here is where things are at the moment, and as always - subject to change based upon performance.

The 13A's, as of this week (at least - officially) each have two stacked ML 1100X subs attached via Speaker Level connection. These subs are great! They are very versatile in the way they can be setup using the onboard controls, plus they have ARC. It's a Tweakers' Delight! This setup is primarily for the benefit of two channel music, but as I'm finding out, home theater results are really, really good! More on that in a bit because the HT usage is not what you're thinking.

My processor, the Emotiva XMC-2, has the ability to dedicate one of its subwoofer channels ONLY for LFE, the true .1 Low Frequency Effects channel. This has been setup this way for months with great results and I really don't know why this isn't an industry-wide feature! What this means is that when the Center Sub output is used for LFE, it is only for LFE and Bass Management must send all the bass from all of the Small speakers somewhere else, like another subwoofer setup as Mono, or, in my case, capable speakers setup as Large in the processor. With Front speakers which can handily spit out bass down below 20Hz, AND, are very capable above 20Hz, it seems to be a no brainer to send the BM to them, unless you really only want them to JUST be a Left and a Right and not share. I was in that last camp for a while, but now I'm changing my vote. I've been using my Expressions for BM for quite a while now and it sounds great. I do however want to relieve some of the extra burden from the Expression's woofers, so another reason for the Stack Of Subs for each speaker. Originally, I wanted the BM to ONLY go to the subwoofers and never enter the 13A, but this has been proving to be more tricky to accomplish from a multi-subwoofer implementation point of view. I can get each pair of subs to produce really good results, and I can get all four subs - two stacks of two in a stereo configuration - to calibrate nicely, but I can't get BOTH scenarios to happen in the way I need to connect them, at least, not yet.

So, right now, each Stack Of Subs (SOS) is connected via the Speaker Level input to the subs, ARC has been run on each sub and each Expression individually - but it would be great to be able to calibrate the group AUTOMATICALLY, and results are pretty good and getting better. So that takes care of two channel, and now Bass Management, good.

Then comes the reworking of the subs dealing with LFE. My biggest complaint with what I did months ago is the fact that one of the subs is under my dining table, not good. Since these ML 1100X subs are really doing an outstanding job I decided to check out what would happen if I used one or two of them for LFE along with the other subs in the LFE group. Well it didn't take long to discover how much better the ML subs are than the Sumiko subs I bought four years ago! As of last night I'm using one left and one right sub of the SOS's for LFE along with one Sumiko sub at the back of the room. The result is fantastic! Bass extends even lower than before with just one narrow dip that might be able to be fixed. So instead of seven subs for BM and LFE, there's five.

How does it sound? I watched some scenes from several movies last night and the bass is SOOOO instant and articulate!!!! The bass ambiance is what it should be, nice and accurate, not too much, not bloated, not shy, scary when it needs to be like that part in The Dark Knight when that guy HITS the window outside the building! That gets me every time, but now I have to wonder if my friend with a heart condition should be warned when it's about to happen.

I won't have my tube amps hooked up again until I'm satisfied with tweaking, so I don't know yet how music really sounds. Yes, I know the tubes aren't powering any of the bass, but it's different with the Krell multi-channel so it's difficult to compare multi-solid-state to mono-tubes. The bass is great! It's competent, full, voluminous, and all those good things, but still won't know till the tubes are back.

How is each SOS integrated with each 13A? Per ML, I ran a test tone at a frequency I wanted to use to blend the subs to the 13A. I used the Low Pass Filter settings in the Subwoofer App to adjust until I found the point where the test tone was quietest. This meant that I had to use the Inverted feature to test 360 degrees. Once I found the quietest point, I simply toggled to the "other" inverted position in the app, and viola (voila)! I started with a 13A and one sub, then added the second sub. This is really simple and quick, and now wires need to be reversed.

Then I tested different settings using the Bass Control on the 13A, as well as the Mid Bass Switch. I ended up setting the Bass Control to -8db, and the Mid Bass set to +2dB. I wanted to test to see where the bass should start to rolloff from the 13A and at what levels the bass would be at different frequencies. In other words, I had an idea of how much "less" bass I wanted to relieve the 13A's of having to produce, but needed some verification as to what this really means in practice. After that I tweaked one sub at a time, then a back and forth operation began but it wasn't too bad.

When both the Left and Right channels are playing a mono signal there's a null that I've been able to reduce quite a bit, but needs more attention. I'm confident that this will almost disappear after some more tweaks.

Here's a graphic to give some idea of what's involved with this setup.
View attachment Sub-Elevation-210105-newLFE-2.jpg

More to come.
 

ttocs

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The Front Left and Right speakers are setup as Large, and they each use two subwoofers for augmented bass.
All speakers except the Front Left/Right are setup as Small.
Center Sub is setup as LFE. Bass Management will not send any bass to this subwoofer channel.
No other Subwoofer channel is setup in the Processor.

Since there is no subwoofer setup as Mono, Bass Management will send all bass for Small speakers to the Left and Right speakers. In my case that means the Left Speaker with Sub-ML1 and Sub-ML2, and the Right Speaker with Sub-ML3 and Sub-ML4. When Bass Management Bass is sent to both Front speakers, the Front Left and Right and 4 subwoofers all produce the Mono bass audio.

Here is the simplified wiring diagram for the current setup.
 

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