Finding Subwoofer

[ttocs]

I've been concentrating on finding answers to everything subwoofer.
There are currently 3 subwoofers in my system, 2 Sumiko S.10 12" Down Firing Driver with Front Firing Passive Radiator: 22Hz@-6dB, and a Rel R-218 10" Down Firing Driver: 25Hz@-6dB.

Over the last couple months there's been quite a lot of moving all the subs around in many combinations in an attempt to discover what frequency ranges work best in the different locations and combinations. I have been stymied by the fact that, as I discovered just yesterday, the UMIK-1 Mic is set from the factory to a 18dB sensitivity making it more sensitive and thus necessitating the mic to be SPL limited to 100dB "plus or minus a little" according to miniDSP. In practice I found that my subs in every combination are limited to 94dB maximum in the measurements. That's it. No more.

It was very confusing for someone like me who had never done any of these kind of measurements before, so I thought there was something wrong with my subwoofers. After scouring the web for answers I came across some testing in various forms which used the UMIK mic while testing subs as loud as 115dB, so I knew it was possible to accomplish, I just had to find the info that tells me how to setup REW with the UMIK to get beyond the 94dB limit. This is where I found out about the sensitivity adjustment in the mic, so I changed mine to 12dB, but this also meant I had to edit the calibration file that came with the mic. All I did was to change the "Sens Factor" from the number it was to 0.0dB. I verified this worked as intended by checking the mic with a calibrated test tone from a mic calibrator tool. The downside to doing this mod is that this setting will not work well with Dirac. Since I have two of these mics, I'll keep the Cross Spectrum Labs 18dB UMIK-1 stock and use it for Dirac, and use the 12dB modded mic for higher SPL tests.

So this allowed me to test the max output of my subs to confirm that they are not limited to 94dB output in my 5400 cubic foot space. This leads this dissertation to a point about being careful to limit the bandwidth to what a sub is capable of producing with no problems. There is the word "compression" used when testing subs. This is the point where a test sweep begins to distort at the highest output a sub is capable of. Starting at a nominal volume level, like -12dB on the XMC-2 volume scale, and keeping the default -12dB output in REW, and setting the sub's gain control to an arbitrary setting - in this case about 30%, I began to make measurement sweeps from 15Hz-200Hz. Then when compression started and affected the frequencies below 22Hz, I changed the starting point of the sweeps to 20Hz. This allowed a higher output level without compression down to 20Hz. 

In this image note the top 4 lines. The purple line is the final sweep that started at 15Hz without compression. The red line is 3dB higher output and shows compression. When the starting point of the sweep is changed from 15Hz to 20Hz, the compression goes away as the black line shows. But then when the output is increased by 1dB more, compression shows up again as seen in the light blue line, and is evident up to 34Hz. So this puts the max output of this sub without compression at 97dB. The point here is when the frequencies below which the sub is not meant to operate are removed, the sub performs as expected. This test is something I will use when choosing a frequency cutoff point in the miniDSP.


Today I begin anew with testing sub locations and combinations. Since I have previously found the best locations in most of the space, I already know where the subs can be placed, for the most part, there is one location that hasn't been tested with a subwoofer but one that I scouted last week when using my version of the subwoofer crawl, I use the microphone crawl. I put the Rel sub with the woofer facing up in the MLP seat, then I use the RTA function in REW and start pink noise using Generator, and record the pink noise whilst moving the mic around in spot after spot after spot after spot . . . . . , all the while viewing the generated curve. The recording has to be started and stopped once the curve has been generated enough to get an idea of how the frequencies are looking. After doing things the hard way for so long, I knew some locations in the space where subwoofers measure the best, and I confirmed that the mic crawl duplicated the results, so I'm happy with the method.

The mic crawl method is how I found a spot in the dining area near one corner of the dining table that looks promising. What's interesting about this is that it's the mirror image location to a spot I already know works well for subwoofers, which partially blocks the Front Right speaker when the sub is in its optimum spot. The results are not horrible when the sub is backed off a little to allow the Right speaker to perform at its best. Here is a plan view showing the spot under the dining table. 


At the moment I have chosen to use the subwoofers for LFE only, which forces Bass Management to push the bass from the Small speakers to the Fronts which are set to LARGE. The woofers on my Fronts work very well up to their crossover point of 300Hz. So this allows me to use them for the bass for all the Small speakers up to the crossover settings allowed in the processor, which are 200Hz for most speakers, and 250Hz for ATMOS speakers. This already has been a huge benefit with my Center speaker that now sounds so much better when it is crossed over at 150Hz. All the boxy-ness from its 5-1/4" woofers is gone. I'm still playing with the Surrounds and Tops which are currently set to 120Hz for the Surrounds and 150Hz for the Tops, but these don't seem to matter as much as the Center Channel does.

I'll post results as they are available showing success hopefully, as well as fails when there is something to learn from it, like what is attached above. It's a learning adventure. Everyone is welcome to share knowledge that is beneficial to the subwoofer cause. Posting visuals is really helpful.

edit 4/2/2021: This post, being the first one, has info that now out of date. I choose to leave it unedited for context.

[ttocs]

System Setup Milestones

Page 9
Dual 2-Sub Stacks  This was the first big leap in a better sounding subwoofer setup that had very good impact and articulation. Bass was appropriately prominent without interfering with other frequency ranges, definitely not boomy. For 2 channel music this was the best sounding setup to date, but it presented some challenges for HT usage that I knew could be better, but would also mean a compromise for 2 channel usage.


Page 38
6 Sub Line Array  This is the first setup with sound that would best the Dual 2-Sub Stacks connected via Speaker Level Connection. It also didn't need subs in other places of the room to smooth dips in the Frequency Response for summed BM or LFE like other setups I've tried.


emotivalounge.proboards.com/post/1127347/thread

[ttocs]

Some resources

Floyd Toole
Audio Science In The Service Of Art
www.harman.com/documents/AudioScience_0.pdf

Floyd Toole Comments
www.audiosciencereview.com/forum/index.php?threads/some-comments-from-floyd-toole-about-room-curve-targets-room-eq-and-more.10950/

Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms (Audio Engineering Society Presents) 3rd Edition
By Floyd E. Toole
www.amazon.com/Sound-Reproduction-Psychoacoustics-Loudspeakers-Engineering/dp/113892136X/ref=sr_1_1?dchild=1&qid=1596124842&refinements=p_27%3AFloyd+E.+Toole&s=books&sr=1-1&text=Floyd+E.+Toole

Something written in 2007, so keep that in mind because there's a recommendation to "not do" what I "am doing", using dedicated subwoofers just for LFE. Technology catches up.
The Misunderstood 0.1 LFE Channel in 5.1 Digital Surround Sound
hometheaterhifi.com/editorial/the-misunderstood-01-lfe-channel-in-51-digital-surround-sound/

Good video showing how to use REW for aligning multiple subs connected to a miniDSP. Simple explanation and demonstration.


Double Bass Array info: en.wikipedia.org/wiki/Double_bass_array

[thezone]

I just bought a pair of RS-13's and they have redefined bass for my living area. The way they extend and control the lower end is phenomenal. I haven't bothered with dirac or any calibrations, just found the best spots for them and let them do the work. I have one hooked up for bass management at 120hz, and one for LFE. I am surprised at how much bass there is in the main channels (non LFE) for movies and I believe that giving this bass to a dedicated sub is the best outcome rather than sending it combined with LFE track to a sub or doubling it up in the mains. I think that enabling LFE and bass management to separate sub outputs was a genius move by emo, that way the two different subs are focusing on completely different information. I seriously believe we are over complicating things with room correction. All my opinion of course!

[ttocs]

Sept 28, 2020 2:23:16 GMT -5 thezone said:

I just bought a pair of RS-13's and they have redefined bass for my living area. The way they extend and control the lower end is phenomenal. I haven't bothered with dirac or any calibrations, just found the best spots for them and let them do the work. I have one hooked up for bass management at 120hz, and one for LFE. I am surprised at how much bass there is in the main channels (non LFE) for movies and I believe that giving this bass to a dedicated sub is the best outcome rather than sending it combined with LFE track to a sub or doubling it up in the mains. I think that enabling LFE and bass management to separate sub outputs was a genius move by emo, that way the two different subs are focusing on completely different information. I seriously believe we are over complicating things with room correction. All my opinion of course!

I agree with all. What I was intrigued with was how the bass management portion improved so much after separating it from the dedicated LFE.

One of the scenarios I'm going to try is using the smaller of my three subs for the bass management portion. I doubt it will work as well as sending the bass management to my Mains, but I need to try it. So then it would be twin 12" subs for LFE, and one 10" sub for bass management. 

[DYohn]

My first question is what are trying to accomplish? You seem focussed on max dbSPL, which is not the correct thing to focus on unless you are a car audio competition builder. So what are you looking for in your room?

[ttocs]

Sept 28, 2020 9:43:17 GMT -5 DYohn said:

My first question is what are trying to accomplish? You seem focussed on max dbSPL, which is not the correct thing to focus on unless you are a car audio competition builder. So what are you looking for in your room?

The max SPL stuff is just baseline testing. I wanted to know. I also want to test the max output of each layout to see at what point the output is lower, and that point happened last night when I tested an arrangement and lost 2dB and lots of headroom forcing REW to stop due to clipping.

What am I looking for? Knowledge. I want to find out what happens:
When I combine two subs together.
When I combine three subs together. 
When one or more subs is located in any of the spots that I may want to choose to put one, or two, or three subs.

Based on results, I may want to add more subs, only use two subs, whatever. I'm open to discovery. I may end up with an entire wall of subwoofers a'la Van Halen with his wall of 412 cabs! Actually I don't, I've already seen the charts that show subwoofer combos and the radiated patterns when stacked or all at the ground plane, separated, etc, and it pays to have some idea of what arrangement can cause nulls in the middle. It's easier than I thought to create a null at the MLP simply by arranging two sub sources (singles or multiples) at the wrong distance apart from each other.

What's most interesting about combining subs is being careful about the arrangement. For example, when subs are stacked, the radiation pattern is wider than it is tall; and when the subs are next to each other the pattern is taller than it is wide.

From Electro-Voice: "The basic directivity rule applies independently in the horizontal and vertical planes. For example, a horizontal line of subwoofers might be large horizontally and small vertically. Therefore, its directivity would be narrow horizontally and wide vertically".

So if you want to have wide (horizontally) dispersion then it is better to array subwoofers in a stacked formation, or tall. I have tested stacking my 3 subs with good results, but it would be better - I suspect - to have a pair of matching stacks. But the results were good enough to perform more tests, although, when doing maximum output tests I'll need to secure the subs on top better, the top one started "walking" to the edge of the cliff and I was barely able to stop disaster.

So far, I'm not too old to learn new tricks.

[megash0n]

Sept 28, 2020 11:38:26 GMT -5 ttocs said:

Sept 28, 2020 9:43:17 GMT -5 DYohn said:

My first question is what are trying to accomplish? You seem focussed on max dbSPL, which is not the correct thing to focus on unless you are a car audio competition builder. So what are you looking for in your room?

The max SPL stuff is just baseline testing. I wanted to know. I also want to test the max output of each layout to see at what point the output is lower, and that point happened last night when I tested an arrangement and lost 2dB and lots of headroom forcing REW to stop due to clipping.

What am I looking for? Knowledge. I want to find out what happens:
When I combine two subs together.
When I combing three subs together. 
When one or more subs is located in any of the spots that I may want to choose to put one, or two, or three subs.

Based on results, I may want to add more subs, only use two subs, whatever. I'm open to discovery. I may end up with an entire wall of subwoofers a'la Van Halen with his wall of 412 cabs! Actually I don't, I've already seen the charts that show subwoofer combos and the radiated patterns when stacked or all at the ground plane, separated, etc, and it pays to have some idea of what arrangement can cause nulls in the middle. It's easier than I thought to create a null at the MLP simply by arranging two sub sources (singles or multiples) at the wrong distance apart from each other.

What's most interesting about combining subs is being careful about the arrangement. For example, when subs are stacked, the radiation pattern is wider than it is tall; and when the subs are next to each other the pattern is taller than it is wide.

From Electro-Voice: "The basic directivity rule applies independently in the horizontal and vertical planes. For example, a horizontal line of subwoofers might be large horizontally and small vertically. Therefore, its directivity would be narrow horizontally and wide vertically".

So if you want to have wide (horizontally) dispersion then it is better to array subwoofers in a stacked formation, or tall. I have tested stacking my 3 subs with good results, but it would be better - I suspect - to have a pair of matching stacks. But the results were good enough to perform more tests, although, when doing maximum output tests I'll need to secure the subs on top better, the top one started "walking" to the edge of the cliff and I was barely able to stop disaster.

So far, I'm not too old to learn new tricks.

Did you ever run MSO to see what it will do to 2 and 3 sub combos? I found this to be far better than more manual efforts when I was testing through all my scenarios. They let you simulate 1 or more All Pass Filters as well which was a huge help in some of my testing. My final layout didn't need one tho. I've somewhat tabled my sub tailoring for now. When I can get the time, and caught up in other areas, I'm planning to build 2 Full Martys(18s) for the low end and 2 Devastators(21s) for the 60-100 hz range. With the right amp, these should crack the drywall mud. I'm just not moving enough air in my room and I'm using low efficiency subs in way too big, sealed boxes.
Keep posting as I'm hoping to learn something new from all your testing.

[DYohn]

Sept 28, 2020 11:38:26 GMT -5 ttocs said:

What am I looking for? Knowledge. I want to find out what happens:

So far, I'm not too old to learn new tricks.

Right on. Enjoy the ride! And by the way if you haven't read this paper, give it a look:

Floyd Toole paper

[ttocs]

Sept 28, 2020 13:28:22 GMT -5 DYohn said:

Sept 28, 2020 11:38:26 GMT -5 ttocs said:

What am I looking for? Knowledge. I want to find out what happens:

So far, I'm not too old to learn new tricks.

Right on. Enjoy the ride! And by the way if you haven't read this paper, give it a look:

Floyd Toole paper

Thanks for this! Yes I have, and thanks for posting the link. marcl has been very supportive and vocal about the writings of Floyd Toole as well. Dr Toole's intricate testing is amazing. His work cannot be overemphasized. 

One of the most basic conclusions that I find fascinating is what one of his associates, Todd Welti, said about how many subwoofers are enough:

"CONCLUSIONS
• How many subwoofers are enough?
Four subwoofers are enough to get the best results of any configuration tried. Two subwoofers is very nearly as good and has very good low frequency support as well."

It was eye opening to discover that 50 subwoofers still doesn't make perfect results for a group of 16 seats, and he then goes on to talk about 5000 subs. Quoting again: "With 5000 subwoofers, modal variation is virtually eliminated. The frequency response at all 16 seats is nearly identical."

My room is not ideal. It's got a lot going on with incongruous wall types meeting at corners. There's the front of the house which is 100% windows that meets an interior wall at one end with studs and 1" thick plaster, and wraps around the corner with another window that I've filled in with rock-wool. Then in the dining area the exterior 10" thick brick wall has a solid, heavy door that meets the interior plaster wall, and it's this corner that is looking promising. I put a subwoofer under one corner of the dining table and am getting some good results. This is only the beginning however, just scratching the surface. I bought some 3-wheel dollies to put under the feet of the two larger subs to make them easy to move because I expect to be moving them a lot in the next few weeks.

My real main goal in all of this, while having fun and learning, is to end up finding out what the smoothest uncorrected frequency response can be for this room between 20Hz and 200Hz. I won't be unhappy if that range is less at the top end, but if it looks as though 150Hz + is possible, that would mean that I could use these subs for Bass Management and get more subs - maybe larger - just for LFE, and return my L&R Mains to normal operation. Just a thought.

[marcl]

Sept 28, 2020 15:13:29 GMT -5 ttocs said:

Sept 28, 2020 13:28:22 GMT -5 DYohn said:

Right on. Enjoy the ride! And by the way if you haven't read this paper, give it a look:

Floyd Toole paper

Thanks for this! Yes I have, and thanks for posting the link. marcl has been very supportive and vocal about the writings of Floyd Toole as well. Dr Toole's intricate testing is amazing. His work cannot be overemphasized. 

One of the most basic conclusions that I find fascinating is what he said about how many subwoofers are enough:

"CONCLUSIONS
• How many subwoofers are enough?
Four subwoofers are enough to get the best results of any configuration tried. Two subwoofers is very nearly as good and has very good low frequency support as well."

It was eye opening to discover that 50 subwoofers still doesn't make perfect results for a group of 16 seats. Quoting again: "With 5000 subwoofers, modal variation is virtually eliminated. The frequency response at all 16 seats is nearly identical."

My room is not ideal. It's got a lot going on with incongruous wall types meeting at corners. There's the front of the house which is 100% windows that meets an interior wall at one end with studs and 1" thick plaster, and wraps around the corner with another window that I've filled in with rock-wool. Then in the dining area the exterior 10" thick brick wall has a solid, heavy door that meets the interior plaster wall, and it's this corner that is looking promising. I put a subwoofer under one corner of the dining table and am getting some good results. This is only the beginning however, just scratching the surface. I bought some 3-wheel dollies to put under the feet of the two larger subs to make them easy to move because I expect to be moving them a lot in the next few weeks.

My real main goal in all of this, while having fun and learning, is to end up finding out what the smoothest uncorrected frequency response can be for this room between 20Hz and 200Hz. I won't be unhappy if that range is less at the top end, but if it looks as though 150Hz + is possible, that would mean that I could use these subs for Bass Management and get more subs - maybe larger - just for LFE, and return my L&R Mains to normal operation. Just a thought.

I think the asymmetry of your room combined with the large volume (not just square feet) all work in your favor with regard to resonance modes and the Schoeder Frequency.  I might be a little concerned with the subs on dollies though ... Newton's Third Law being what it is 

[ttocs]

Sept 28, 2020 15:31:17 GMT -5 marcl said:

Sept 28, 2020 15:13:29 GMT -5 ttocs said:

Thanks for this! Yes I have, and thanks for posting the link. marcl has been very supportive and vocal about the writings of Floyd Toole as well. Dr Toole's intricate testing is amazing. His work cannot be overemphasized. 

One of the most basic conclusions that I find fascinating is what he said about how many subwoofers are enough:

"CONCLUSIONS
• How many subwoofers are enough?
Four subwoofers are enough to get the best results of any configuration tried. Two subwoofers is very nearly as good and has very good low frequency support as well."

It was eye opening to discover that 50 subwoofers still doesn't make perfect results for a group of 16 seats. Quoting again: "With 5000 subwoofers, modal variation is virtually eliminated. The frequency response at all 16 seats is nearly identical."

My room is not ideal. It's got a lot going on with incongruous wall types meeting at corners. There's the front of the house which is 100% windows that meets an interior wall at one end with studs and 1" thick plaster, and wraps around the corner with another window that I've filled in with rock-wool. Then in the dining area the exterior 10" thick brick wall has a solid, heavy door that meets the interior plaster wall, and it's this corner that is looking promising. I put a subwoofer under one corner of the dining table and am getting some good results. This is only the beginning however, just scratching the surface. I bought some 3-wheel dollies to put under the feet of the two larger subs to make them easy to move because I expect to be moving them a lot in the next few weeks.

My real main goal in all of this, while having fun and learning, is to end up finding out what the smoothest uncorrected frequency response can be for this room between 20Hz and 200Hz. I won't be unhappy if that range is less at the top end, but if it looks as though 150Hz + is possible, that would mean that I could use these subs for Bass Management and get more subs - maybe larger - just for LFE, and return my L&R Mains to normal operation. Just a thought.

I think the asymmetry of your room combined with the large volume (not just square feet) all work in your favor with regard to resonance modes and the Schoeder Frequency.  I might be a little concerned with the subs on dollies though ... Newton's Third Law being what it is 

Subs On Dollies: Is that something like the Duran Duran song: Girls On Film?

Yeah, the dollies are only for moving the subs and initial testing, and can't use them for any test on the hardwood floor. When things get serious the feet hit the ground. BTW when doing the 107dB test last week with the stack-o-subs, no dollies were employed when the top sub started dancing, its feet just weren't as "grippy" as the two larger subs.

[marcl]

Sept 28, 2020 15:41:21 GMT -5 ttocs said:

Sept 28, 2020 15:31:17 GMT -5 marcl said:

I think the asymmetry of your room combined with the large volume (not just square feet) all work in your favor with regard to resonance modes and the Schoeder Frequency.  I might be a little concerned with the subs on dollies though ... Newton's Third Law being what it is 

Subs On Dollies: Is that something like the Duran Duran song: Girls On Film?

Yeah, the dollies are only for moving the subs and initial testing, and can't use them for any test on the hardwood floor. When things get serious the feet hit the ground. BTW when doing the 107dB test last week with the stack-o-subs, no dollies were employed when the top sub started dancing, its feet just weren't as "grippy" as the two larger subs.

I was picturing the subs moving back and forth and the air standing still ... 0db!

[DYohn]

Discovering what works in your room is the key and there is NO one size fits all. My recommendation is to set up your test mic in the primary seating position and run sweeps from 20-200Hz at 85dbSPL. Look for valleys, not peaks, and move your subs if you can to minimize these. Then look at peaks and if there are no peaks greater than +10db above 100Hz you are good. If you do have big peaks above 100Hz, you can EQ them out. I use two subs in the front of my room and two subs on the sides crossed below 150Hz, with my mains high-passed @ 80Hz. And then when watching movies I also have a IB manifold in my ceiling loaded with 4X15 subs crossed below 65Hz, which creates a nice THX house curve when I want it. .

[megash0n]

Sept 28, 2020 17:06:22 GMT -5 DYohn said:

Discovering what works in your room is the key and there is NO one size fits all. My recommendation is to set up your test mic in the primary seating position and run sweeps from 20-200Hz at 85dbSPL. Look for valleys, not peaks, and move your subs if you can to minimize these. Then look at peaks and if there are no peaks greater than +10db above 100Hz you are good. If you do have big peaks above 100Hz, you can EQ them out. I use two subs in the front of my room and two subs on the sides crossed below 150Hz, with my mains high-passed @ 80Hz. And then when watching movies I also have a IB manifold in my ceiling loaded with 4X15 subs crossed below 65Hz, which creates a nice THX house curve when I want it. .

love some infinite baffles. I hope to use mine again someday. I have never heard anything handle the really low end like them.

[405x5]

I bought a big ass subwoofer.....cranked the volume until it matched my system, then walked away....end of story

[ttocs]

Sept 28, 2020 17:59:52 GMT -5 405x5 said:

I bought a big ass subwoofer.....cranked the volume until it matched my system, then walked away....end of story

Can you at least draw a horizontal line on some graph paper? 

[405x5]

Sept 28, 2020 18:47:00 GMT -5 ttocs said:

Sept 28, 2020 17:59:52 GMT -5 405x5 said:

I bought a big ass subwoofer.....cranked the volume until it matched my system, then walked away....end of story

Can you at least draw a horizontal line on some graph paper? 

I can’t draw ✍️ as straight line without it!

[ttocs]

This installment highlights the preferred locations for a two subwoofer setup. This is where I "want" the subs to be in a perfect world. As shown in the plan the subs are inboard of the Front Left and Right main speakers, under the tv. The attached plots are with no correction, no PEQ, but where the two subs are measured together there is delay added to one of them, which happens to be S2.

S2 and S1 are at the top of the plan.


The first two plots are of each subwoofer individually. The third plot is both together with some delay on S2. Notice the boosted bass below 40Hz with both subs together, but also notice some loss of SPL on both sides of the 50Hz peak.
      

I've done enough testing to know that there are other locations and combinations that work better, but wanted to share this scenario first. I played a little with PEQ and was able to reduce the peak around 50Hz but chose not to confuse things. I want to show all the different combinations, this combo and the others to follow, without corrections before delving into any type of correction other than delay.

[marcl]

Sept 30, 2020 1:16:13 GMT -5 ttocs said:

This installment highlights the preferred locations for a two subwoofer setup. This is where I "want" the subs to be in a perfect world. As shown in the plan the subs are inboard of the Front Left and Right main speakers, under the tv. The attached plots are with no correction, no PEQ, but where the two subs are measured together there is delay added to one of them, which happens to be S2.

S2 and S1 are at the top of the plan.


The first two plots are of each subwoofer individually. The third plot is both together with some delay on S2. Notice the boosted bass below 40Hz with both subs together, but also notice some loss of SPL on both sides of the 50Hz peak.
      

I've done enough testing to know that there are other locations and combinations that work better, but wanted to share this scenario first. I played a little with PEQ and was able to reduce the peak around 50Hz but chose not to confuse things. I want to show all the different combinations, this combo and the others to follow, without corrections before delving into any type of correction other than delay.

How does this compare to having S2 where it is, and S1 back by the refrigerator?