*** 2 Subwoofers Size vs 1 - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 21 Old 05-21-2020, 08:34 PM - Thread Starter
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*** 2 Subwoofers Size vs 1

In rebuilding my system starting L/C?/R prob go with Kef R3, R5, LS50 or Canton reference 9.2. Room is 12' x 15' 17ft ceilings. Don't listen loud too much in HT in music around 75db. Heading towards more music than I thought but 60% HT/40%music. Love clarity project wide stage vocals.

everyone has told me advantages of 2 vs 1 sub. IF 2 sub my original thought was going to do 2-HSU VTF3 MK5, but then I saw how large they are and not likely to be WAF approved. Can I get away with 2 - 12" or 10"'s or better with 1-15" HSU or Rythmik? Others?


Thank You,
Dan
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post #2 of 21 Old 05-21-2020, 08:42 PM
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2 12" Subs should be fine at your listening levels, I actually think that's the sweet spot for most people. 10" Subs might not dig deep enough unless you get the Monoprice Monolith 10's, which are about the size of most 12" Subs anyway.
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post #3 of 21 Old 05-21-2020, 08:57 PM
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Quote:
Originally Posted by LuigiF1 View Post
In rebuilding my system starting L/C?/R prob go with Kef R3, R5, LS50 or Canton reference 9.2. Room is 12' x 15' 17ft ceilings. Don't listen loud too much in HT in music around 75db. Heading towards more music than I thought but 60% HT/40%music. Love clarity project wide stage vocals.

everyone has told me advantages of 2 vs 1 sub. IF 2 sub my original thought was going to do 2-HSU VTF3 MK5, but then I saw how large they are and not likely to be WAF approved. Can I get away with 2 - 12" or 10"'s or better with 1-15" HSU or Rythmik? Others?


Thank You,
Dan
Subs that large can be used as end tables or hidden in other ways. That being said, I think it's very common for people to go from, say, one 15" sub to dual 12".

If you're leaning more towards music, the HSU ULS-15 might be an option. It's got a smaller spacial footprint, and I can attest based on first-hand experience that it's an excellent subwoofer.
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post #4 of 21 Old 05-22-2020, 05:57 AM
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When placed properly, a pair of well-integrated subs will sound better throughout the room than a single larger sub.
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post #5 of 21 Old 05-22-2020, 06:23 AM
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Is your main concern the MLP? If so, you might have better luck with one 15" sub over dual 12" subs. It will be easier to integrate the single sub and take up less floor space overall.


If you are going to try and nail the subwoofer performance for multiple seats you "might" (probably likely) need multiple subs.


Do you have any starting point of knowing how much subwoofer is enough for you? If this is an experiment I would suggest starting with one sub to find out what enough volume is for you and then get a 2nd one of those to add headroom and smoother response throughout the room. Starting with two can be difficult if you don't "know" those two are enough for you. You might struggle determining if the two subs are not capable enough for your needs or the two subs just aren't aligning well. Experimenting with one unknown is doable. Experimenting with two or more unknowns can be very difficult.
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post #6 of 21 Old 05-22-2020, 07:38 AM
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That depends,

Generally speaking, "normal" people ask me about subs--be they teenagers about car subs, folks that want some oomph for their music/HT systems or bands that need to get subwoofers for their gigs. All of them have the same things in common, they all do! So I ask these simple questions:

1. How large/heavy can the subwoofers be for your needs?
2. How many subwoofers can you put in the room/car/gig?
3. How much money is in your budget?
4. How much SPL do you require?
5. How low in frequency do you desire? Spec it at -3dB and -6dB to fill out the spec.

If they say they want "tens" and they demand 16Hz -6dB--they can get that but it severely limits options. Something like a CSS SDX10 can be forced to do that ported but you'll need a rather large quantity to get the SPL up and it can get expensive and they will be quite large for a "ten". If you want Bose bass module small or as small as posssible--get sealed ten (SDX 10 or UM10) and keep adding them with EQ to get the SPL and frequency response you desire. Sure, you might need four, eight or 32 of them but at least you can keep adding until you get what you want. Start blowing breakers? Add more electrical lines--you can get what you want without having a clue by just adding more! I call it the "government money" option, keep throwig money at it untill the problem goes away!

Most people learned about "subwoofers" from the Bose School of the AM-5-they teach you only need one and it can be thrown anywhere and hidden with a flower pot on the top. I am talking real world here, not forums--you know, real people that ask me things in person. It is difficult to deprogram the Bose graduates of bass and they are everywhere! The easiest way to derail them is to offer THX and Dolby recommendations which are two or more subs and to mention that three (Earl Geddes alignment) or FOUR subs (Harmon International) are recommended for larger rooms with multiple seats. It does not matter if it is music in mono, 2 channel, quadraphonic or 5 to 13 channel HT systems--bass is bass and there are rules. The first "audiophile" system I saw as a kid had TWO subwoofers and they were diagonal from each other and not aethetically pleasing. The guy had measuring gear, books on acoustics and so on and I soon learned the method behind the madness.

Once they get that, then I ask about "how low do you want to go" and inform them that the difference in size between 16Hz and 32Hz is the box will be four times larger. That wakes them up! Everyone wants 120dB at 16Hz--I know I do but the math gets insane. Luckily, it is much easier to explain with calculators on the internet. Plug in your SPL demands in dB, plug in your frequency demands then plug in the Sd (surface area of the driver) and press go. You will get the stroke (Xmax) required to move that amount of air. Sometimes you'll see something like 300 mm or more which is impossible so keep adding to the quantity until the Xmax reaches what drivers can actually do.

Most people's eyes start to glaze over once the evil math shows up--so I offer this: Tell me what you want for extension in frequency be it 16Hz, 20Hz or 25Hz and purchase whatever subwoofer that is in the size/weight/price you want to deal with. Be aware that, generally speaking if you see 10, 12, 15, 18, 21, 24 or..you can get an 80 inch sub from China--generally the larger diameter the more air it can pump so you'll have higher output. Also, because life tends to suck that way--the lower you go the higher in SPL you need to actually hear it--don't ignore our very insensitive hearing!

Over the years, I tend to push people into at least 12 inch subwoofers for several reasons. They are the most produced size subwoofer drivers so have a lower cost due to economy of scale. Generally speaking,they can go low in frequency at enough SPL that you can hear it. For the most part, people can deal with the size of them (4 cubic feet or so) if they really care about audio. If they are not sure about frequency response (most people don't hang around discussing audio) I offer THX specifications for sub bass or 20Hz at -6dB or IMAX which is 20Hz at -3dB. This is very easy to understand and removes my opinion from the equation so they can't shoot the messenger! If they want the subwoofers for music, I offer up that the 88 key piano has a low key of 27.5 Hz so might as wel cover the piano--blame the piano--not me!

For the most part, a single 12 will get them the frequency response but it can't do the SPL in most typical living rooms. This is a GOOD thing because most of the people I deal with have friends and family so don't sit alone in a single chair and need good bass response across multiple seats. They get the SPL they want while the rest of the family gets the coverage so they can hear it also by using two or more subs. Say the "bug bites" them and they want MORE! Keep adding subs, three of them and read this configuration from Earl Geddes or four of them and here is a Harmon "white paper". Generally speaking, once a person hits say four 12" subwoofers in their living room and still wants more.., they can use all of them for nearfield "tactical" subwoofers and go nuts with 15/18/21/24 and so on. At least if they know what frequency they want, the system then can be scaled up without throwing everything away and starting over. For real world when you are either related to the people and can't hide from them--they wlll complain about you "getting it wrong" for life... I tend to use THX, IMAX or the 88 key piano for specifications so they make the decision, not me and if the system scales they can always add more.

The great thing about forums is I have no responsibility and if you blow your budget on something that won't work--no skin off my butt! Plenty of information a simple Google search away from THX, Dolby, IMAX and the Acoustic Engineering Society--if you don't want to bother learing about that, more power to you. I do strongly advise to at least have a familiarity with the recommendations from the folks that set the standards though, saves a ton of time in the long run.

In summation, it the most generic terms possible... start off with a 10/12 inch sub that does THX standards for frequency response and keep adding them until you get the SPL you desire. For music, go for the low note on the 88 keys at a minimum and for PA systems.. 27.5 Hz at -6dB (high passed a 25Hz) should do it for moden dance music. If you desire 8 Hz for cannon fire, pipe organs or special effects... sealed, infinite baffle or LLT and keep stacking until you either get there, divorce happens, the dwelling burns down or you run out of space

In the end, this is supposed to be fun and is just a hobby--a first world silly little hobby at that. For clarity, I use 12 and 15 inch subs in sealed, ported, push-pull slot loaded and eventually a tapped horn. Smaller for cars, medium for houses and larger for PA/party systems works for me. Enjoy your new subs!
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post #7 of 21 Old 05-22-2020, 08:35 AM
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Originally Posted by badtlc View Post
Is your main concern the MLP? If so, you might have better luck with one 15" sub over dual 12" subs. It will be easier to integrate the single sub and take up less floor space overall.


If you are going to try and nail the subwoofer performance for multiple seats you "might" (probably likely) need multiple subs.


Do you have any starting point of knowing how much subwoofer is enough for you? If this is an experiment I would suggest starting with one sub to find out what enough volume is for you and then get a 2nd one of those to add headroom and smoother response throughout the room. Starting with two can be difficult if you don't "know" those two are enough for you. You might struggle determining if the two subs are not capable enough for your needs or the two subs just aren't aligning well. Experimenting with one unknown is doable. Experimenting with two or more unknowns can be very difficult.

I agree about starting with one sub and then replacing or adding depending upon the result. Several months ago, I purchased a single 15" ported sub for my gameroom. I never had a sub in this room before so I was doing a bit of guesswork. After quite a bit of tweaking, I am fairly happy with the result, but I now realize I want a sub with usable extension below 20 Hz. Consequently, I am considering selling or trading in my sub, but this change would have been complicated if I had started out with two subs.
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post #8 of 21 Old 05-22-2020, 09:08 AM
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Buy the SVS pb3000. On sale this weekend, better looking than hsu, rhythmik, monoprice. Only 75#. Ports can be blocked for sealed mode. Cell phone control app. Buy a second if you can. Far better than 12” subs and split voice coil lets it compete with bigger subs. You have to like the black ash finish though (I do).
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post #9 of 21 Old 05-22-2020, 09:40 AM
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Originally Posted by LuigiF1 View Post
In rebuilding my system starting L/C?/R prob go with Kef R3, R5, LS50 or Canton reference 9.2. Room is 12' x 15' 17ft ceilings. Don't listen loud too much in HT in music around 75db. Heading towards more music than I thought but 60% HT/40%music. Love clarity project wide stage vocals.

everyone has told me advantages of 2 vs 1 sub. IF 2 sub my original thought was going to do 2-HSU VTF3 MK5, but then I saw how large they are and not likely to be WAF approved. Can I get away with 2 - 12" or 10"'s or better with 1-15" HSU or Rythmik? Others?
40% music in a 12 x 15' room, I'd go with a pair of sealed Hsu ULS-15, smaller but also tighter/faster for music ... dual VTF-3 would be overkill, unless the 12 x 15' room opens out onto a bunch of other rooms.

~ Are you a "geek hobbyist" obsessed with squeezing out that last 5-10% improvement? The economy will thank you...especially the Chinese one. Or are you more of a get-set-and-forget "casual user" who simply wants to increase your enjoyment of movies, TV and gaming? Relax, HT isn't rocket science, nor does it have to cost an arm and a leg---especially if you ignore the aforementioned vocal minority. And remember to smile...it's just a silly hobby, after all. :)
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post #10 of 21 Old 05-22-2020, 11:27 AM
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I think two 12" sealed subwoofers will be all you need in that size room.

I have 2x Rythmik F12G in a 13x16x8 room and they are overkill. I had two 12" Dynaudio subs with diminutive cabinets in the same room before and they were overkill too.

If you have flexibility in where you place the subs, then two subs can give you flatter frequency response than one.

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post #11 of 21 Old 05-22-2020, 12:08 PM
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Quote:
Originally Posted by LuigiF1 View Post
In rebuilding my system starting L/C?/R prob go with Kef R3, R5, LS50 or Canton reference 9.2. Room is 12' x 15' 17ft ceilings. Don't listen loud too much in HT in music around 75db. Heading towards more music than I thought but 60% HT/40%music. Love clarity project wide stage vocals.

everyone has told me advantages of 2 vs 1 sub. IF 2 sub my original thought was going to do 2-HSU VTF3 MK5, but then I saw how large they are and not likely to be WAF approved. Can I get away with 2 - 12" or 10"'s or better with 1-15" HSU or Rythmik? Others?


Thank You,
Dan
That is an awfully small room where loud volumes are not your goal; even one VTF3 would have been overkill IMHO.

ULS 15 is sealed and "tiny" by comparison to a VTF3 as they are essentially 18" cubes.

Using HSU's numbers, compared to a single ported VTF3 dual sealed ULS15s have the same volume potential from 16-31.5HZ and a 3db advantage 40-63HZ, and much better bass spread across a wider area.

Using Rhythmik's numbers the smaller 15-3/4"(W) x 15-3/4" (H )x 17"(D) - (18-1/2" D with grille) two sealed F12s have just 2db less sound pressure level at 20hz than a single ported FVX15.
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post #12 of 21 Old 05-22-2020, 01:41 PM
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That is an awfully small room where loud volumes are not your goal; even one VTF3 would have been overkill IMHO.

ULS 15 is sealed and "tiny" by comparison to a VTF3 as they are essentially 18" cubes.

Using HSU's numbers, compared to a single ported VTF3 dual sealed ULS15s have the same volume potential from 16-31.5HZ and a 3db advantage 40-63HZ, and much better bass spread across a wider area.

Using Rhythmik's numbers the smaller 15-3/4"(W) x 15-3/4" (H )x 17"(D) - (18-1/2" D with grille) two sealed F12s have just 2db less sound pressure level at 20hz than a single ported FVX15.
One ULS-15 should be sufficient, yes.

The area my HT is in is 12 x 16, but it's an open concept space, and it feeds right into the 14 x 30-ish area of the "dining room" and "kitchen." The ULS-15 has no trouble IMO, and Audyssey had me turn the gain knob to about the 7:30 mark.

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post #13 of 21 Old 05-22-2020, 02:15 PM
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One ULS-15 should be sufficient, yes.

The area my HT is in is 12 x 16, but it's an open concept space, and it feeds right into the 14 x 30-ish area of the "dining room" and "kitchen." The ULS-15 has no trouble IMO, and Audyssey had me turn the gain knob to about the 7:30 mark.
You and I are the tiny minority on AVS in going with sealed vs ported for our theater rooms; mine is even larger than you with a a similar larger kitchen space opening in the right rear of the theater room.

So even two Rhythmik L12s should be sufficient if he want to go two subs in your opinion?

That's what I'm going to do in my larger space in which I have a single 15" 1250 watt sealed servo sub now.

Go with two smaller Rhythmik 12s.

L12 is quite compact; 14"(W) x 14" (H )x 15-1/2" (D) with grille and amplifier knobs.
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post #14 of 21 Old 05-22-2020, 02:45 PM
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You and I are the tiny minority on AVS in going with sealed vs ported for our theater rooms; mine is even larger than you with a a similar larger kitchen space opening in the right rear of the theater room.

So even two Rhythmik L12s should be sufficient if he want to go two subs in your opinion?

That's what I'm going to do in my larger space in which I have a single 15" 1250 watt sealed servo sub now.

Go with two smaller Rhythmik 12s.

L12 is quite compact; 14"(W) x 14" (H )x 15-1/2" (D) with grille and amplifier knobs.
2 Rythmik L12s would probably be even better than 1 ULS-15.

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post #15 of 21 Old 05-23-2020, 10:26 PM
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2 vs 1 sub
2x10" is roughly equivalent to a 15 as far as cone area plus two subs load each other. But as pointed out physically smaller speakers have trouble playing as low as larger due to physical construction constraints and Hofmann's Iron Law. As for two subs being able to produce smoother bass throughout a larger area, I'd observe that's true if (IF!) you either have room correction that can handle two independent subs (Audyssey SubEQ HT) OR you spend a lot of time moving and tuning crossovers and measuring. If neither of those applies then I'd agree one sub is simpler to integrate.
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post #16 of 21 Old 05-23-2020, 10:43 PM
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my rythmik fv15hp is all around better than my 2 velodyne 12in subs. I would decide based on my space/placement/decor options.

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post #17 of 21 Old 05-24-2020, 05:51 AM
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Your room really isn't that small, and I would start with a 15" sub if you have the space. Dual 15" sealed subs would probably work well in your room.
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post #18 of 21 Old 05-24-2020, 01:47 PM
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As for two subs being able to produce smoother bass throughout a larger area, I'd observe that's true if (IF!) you either have room correction that can handle two independent subs (Audyssey SubEQ HT) OR you spend a lot of time moving and tuning crossovers and measuring. If neither of those applies then I'd agree one sub is simpler to integrate.
You don't need an AVR or pre/pro that supports two independent subs. You can split a single subwoofer output. Both subwoofers get the same signal and use the same crossover settings. If the two subs are not equidistant from the MLP, then you do have to independently adjust the subwoofer's level and phase controls, but that's straightforward and can be done by ear.

There are many things you can do placement-wise to get smoother bass response with two subs, including cancelling room modes and filling in nulls. Four is even better than two.

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post #19 of 21 Old 05-25-2020, 03:01 PM
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...You can split a single subwoofer output...If the two subs are not equidistant from the MLP, then you do have to independently adjust the subwoofer's level and phase controls, but that's straightforward and can be done by ear. There are many things you can do placement-wise to get smoother bass response with two subs, including cancelling room modes and filling in nulls. Four is even better than two.
Hmmm. Being equidistant from the main listening position won't guarantee the response of the subs is the same, unless the entire listening space is symmetric. Yeah perhaps adjustable "close enough" with a level control and phase if the sub has that. I'm feeling to really truly get the smoothing benefits of two (or four) you'd need software to integrate and/or measurement equipment and adjustable crossovers and spend a chunk of time tweaking. That's more a theoretical engineer's perspective; hopefully others who've really messed with that will chime in
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post #20 of 21 Old 05-25-2020, 04:16 PM
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Hmmm. Being equidistant from the main listening position won't guarantee the response of the subs is the same, unless the entire listening space is symmetric. Yeah perhaps adjustable "close enough" with a level control and phase if the sub has that. I'm feeling to really truly get the smoothing benefits of two (or four) you'd need software to integrate and/or measurement equipment and adjustable crossovers and spend a chunk of time tweaking. That's more a theoretical engineer's perspective; hopefully others who've really messed with that will chime in

I can vouch for this. I ran symmetrical dual subs up front next to my towers and I still had to adjust one by about 90 degrees for optimal integration with each other. More than distance factors in to it.
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Sub: P̶L̶-̶2̶0̶0̶I̶I̶ | (̶2̶)̶ ̶F̶V̶X̶1̶2̶ | V1812
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post #21 of 21 Old 05-26-2020, 09:18 AM
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Quote:
Originally Posted by head_unit View Post
Hmmm. Being equidistant from the main listening position won't guarantee the response of the subs is the same, unless the entire listening space is symmetric. Yeah perhaps adjustable "close enough" with a level control and phase if the sub has that. I'm feeling to really truly get the smoothing benefits of two (or four) you'd need software to integrate and/or measurement equipment and adjustable crossovers and spend a chunk of time tweaking. That's more a theoretical engineer's perspective; hopefully others who've really messed with that will chime in
Obviously, two is more effort than one, and four is more effort than two. That's as far as I've gone. I'm back to using two in both of my rooms.

Almost all the effort is in finding the best placement. That's true whether you're setting up a single sub or multiple. There are some simple rules of thumb you can follow if you have a mostly rectangular room. The more irregular the room, the more trial and error. Measurements make the process quicker. I think you can do just as well with test tones, but it's more tedious.

EDIT: Even if you only have one sub in an optimal location, and plonk the second sub down wherever it's convenient, their combined FR is likely to be flatter than the single sub alone. In fact, Earl Geddes and some others even recommend random placement with four subs.

Once you've found the optimum locations for two subwoofers, the rest is easy. Suppose your AVR only supports one subwoofer. Here is what you can do:

1. Split the sub out and run to both subs
2. Set both subs initially to the same level, zero phase, crossover bypassed.
3. Run your AVR's auto-setup. The purpose of this step is just to get an initial setup so you can perform the next two steps.
4. Adjust phase. Do this one subwoofer at a time, with the other sub off. Play test tones around the crossover frequency, or a noise signal in the sub channel only, and set the phase to maximize loudness at the listening position. It's quick if you have a helper to adjust the phase control while you sit in the listening position.
5. Balance the levels (optional). Unless your subs are symmetrically placed, it's likely that one sub is louder than the other at the main listening position. Depending on the difference in loudness, your crossover frequency, and source material, this may or may not contribute to being able to localize some bass frequencies. To minimize the chance of that, you can balance the levels of the two subs to have equal loudness at the listening position. This will also be really quick if you have a helper.
6. Run your AVR's auto-setup once again.

The only part of the process that's different from what you'd do with a single sub is the balancing, which is best done by ear.
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HT: Dynaudio C2, Contour S CX, 2x BM14S, Aperion surrounds, Simaudio Titan, Marantz AV8801, Oppo 103, Linn Majik DS, and a Pioneer Kuro
Stereo: Dynaudio Focus 160, Simaudio W-5 LE or Luxman M-600A, Linn Akurate DSM, 2x Rythmik F12G
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Last edited by Red MC; 05-26-2020 at 09:28 AM.
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