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Your setup works for you, and thats great. You are getting an increase in SPL, your frequency response is decent, and they meet your aesthetic requirement. My only intention was to point out that mutual coupling is not required to get the 5-6 dB increase in output from dual subs, especially since many people have a very poor response with a single sub, or mutually coupled dual subs. I think it is a disservice to the community for anyone to think they MUST mutually couple their subs in order to get the 5/6 dB increase, especially for those that have a poor FR with their subs set up in this manner. You can have your cake and eat it too.


I have to admit that you educated me on that. I thought that the further away they were that you would only get a coupling at the very lowest frequency is where the wavelength are further


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Dual subs do not have to be mutually coupled(placed close together as yours are) to realize the 6 dB gain in output. This is a horrible myth that just won't die no matter how many times it is explained and dispelled.

Yes, it is EASIER to get a completely linear, 6 dB increase in output that matches whatever FR a single sub has when you add a second sub nearby.

Yes, dual subs, when spread out, placed and setup poorly, may not yield a 6 dB increase in output.

However, with measurement equipment and placement flexibility, there is absolutely no reason dual subs, spread out, placed and setup properly, not to be getting a 6 dB increase in output, ALONG with improved FR. It's a fact. Many have done it, not only myself.

It's like saying your MT-110 speakers have horrible imaging, but you have one under the couch and the other in the closet. You have to place them and set them up properly to get the performance they are capable of producing.

I'm really glad you posted this Bear. It made me think about coupling a little more and got me thinking about adding a couple of subs in my room. Having co-located or mutually coupled subs (stacked or side by side) is one way to guarantee that room modes will not affect the 3 - 6 dB increase across the frequency response differently than with one subwoofer. Having the sub in another part of the room can have the same 6 dB increase, however, the room modes now come into play. You may have +6 dB in some spots where the standing waves create peaks while you could have -6dB (or more) cancellation where the standing waves cause nulls. Having the subwoofer in the ideal spot will smooth out both the peaks and the nulls, creating a smoother frequency response across the board. That doesn't mean that you won't have a really nice +6 dB coupling at a few frequency bands in certain spots, but it's no guarantee. The only guarantee is when they are stacked or side by side.
 

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I'm really glad you posted this Bear. It made me think about coupling a little more and got me thinking about adding a couple of subs in my room. Having co-located or mutually coupled subs (stacked or side by side) is one way to guarantee that room modes will not affect the 3 - 6 dB increase across the frequency response differently than with one subwoofer. Having the sub in another part of the room can have the same 6 dB increase, however, the room modes now come into play. You may have +6 dB in some spots where the standing waves create peaks while you could have -6dB (or more) cancellation where the standing waves cause nulls. Having the subwoofer in the ideal spot will smooth out both the peaks and the nulls, creating a smoother frequency response across the board. That doesn't mean that you won't have a really nice +6 dB coupling at a few frequency bands in certain spots, but it's no guarantee. The only guarantee is when they are stacked or side by side.


Partly correct. More likely, dual subs that are properly spread out and setup will often result in filling in a huge 10-15 dB null, flattening huge boomy peaks, etc. So it is likely that huge nulls can be filled in 10-15+ dB, huge messy peaks cut more than 6 dB, with the average, broadband pink noise increase being 6 dB across the frequency range.

It is true that mutually coupled subs will increase the poor frequency response of the single sub by exactly 6 dB at all frequencies. Huge peaks will be 6 dB higher, huge nulls will be 6 dB higher. I’ll take a smoother response with smaller peaks, no nulls, and the same overall 6 dB increase with proper placement, rather than negating the main benefit of dual subs by stacking them.


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Thanks Rolls. While making my first post I realized I signed up for AVS in 2008, so I’m a long time reader and observer of folks going down the rabbit hole. Now that I finally jumped in I’m having a hard time being patient. I figured I’d pop in here and say hello to maybe ease the waiting process. What do you have/what are you upgrading to?


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I have 1 S7201 and 2 V3611. I tried out 2 S3601 in the V's places but did not like it. There are too many pros from both of what I have to not mix them. Eventually I am going to upgrade the 2 V3611 to 72s; however, it probably won't happen until there is a v2 of them or something else over them that I swap all 3 out for. I've run into several issues but the biggest one is a 7 foot null zone through the middle of the room. I have found making a triangle of subs makes it go away. If you get all crazy with it I suggest getting a ton of the Atmos/THX/Etc. openings and sitting in your MLP as well as the other areas people sit and listening to them all. I also suggest cutting several scenes from movies like Ready Player one, Blade Runner 20w/eitis, horror movies, etc. and listening to them. Do this in addition to staring at the REW line, you may hear and feel something opposing what your eyes see.
 

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I have 1 S7201 and 2 V3611. I tried out 2 S3601 in the V's places but did not like it. There are too many pros from both of what I have to not mix them. Eventually I am going to upgrade the 2 V3611 to 72s; however, it probably won't happen until there is a v2 of them or something else over them that I swap all 3 out for. I've run into several issues but the biggest one is a 7 foot null zone through the middle of the room. I have found making a triangle of subs makes it go away. If you get all crazy with it I suggest getting a ton of the Atmos/THX/Etc. openings and sitting in your MLP as well as the other areas people sit and listening to them all. I also suggest cutting several scenes from movies like Ready Player one, Blade Runner 20w/eitis, horror movies, etc. and listening to them. Do this in addition to staring at the REW line, you may hear and feel something opposing what your eyes see.
I know it is generally recommended that sealed and ported subs not be mixed as it could create cancellations, but wouldn't mixing ported subs with different tuning frequencies create the same issues? In your case, you like the sound of your ported and sealed subs combined despite what the graphs say and what we hear should trump any graph.
 

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The reason why it still sounds good is because the cancellation between the 2 different alignments are down in the frequency range that is basically inaudible if the distortion is low. Infrasonic frequencies 20hz and lower are like waves of silent pressure. Most rooms just creak and rattle like crazy down that low. So basically you are giving up some room pressurizing capability or a loss of weight to the bass on certain scenes. It's by no means a deal breaker.

I
think most are trying to point out that you are not getting the full benefits of your investment is all. To each is own.
 

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I'll withhold final judgement for a while. But this is seeming more and more like having a big banner at HTR. Oh the traffic was easy to follow. TONS of traffic. Sales? not so much..:) Of course there are benefits to traffic without sales for many business models...just not so much OUR specific model. But some of the chat chatter got me to thinking too. I've had more than one chat with the following(paraphrasing of course).

THEM: I just heard of you guys from youtube, I was going to get a XYZ sub. Why should I buy from you.

ME: Well, we have a much longer warranty.

THEM: I dont care about that. 2/3 years is plenty.

ME: Okay, we do have the 60 day trial versus 30 as well and our products are typically in stock and ready to ship within a few days.

THEM: I buy to keep, trial period doesn't matter at all, and I don't mind waiting 2-4 weeks.

ME: Okay. Well, we only charge for the return shipping if you DID decide the product wasn't meeting your needs, the other company charges shipping both ways.

THEM: Already said, I won't be returning it.

ME: Okay, hmmm. We also have a trade in policy which typically gives you a very good percentage of your original purchase price toward a new model.

THEM: Not interested. When I buy, I buy to keep.

And that goes on a little longer. All the "perks" I might think are essential others may not. Got me thinking a little(I know uh oh). Anyway, I'll post more soon.



Tom V.
Power Sound Audio
I am extremely curious what the other subs were there are looking at. Are they the crap they find in big box stores?
 

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The reason why it still sounds good is because the cancellation between the 2 different alignments are down in the frequency range that is basically inaudible if the distortion is low. Infrasonic frequencies 20hz and lower are like waves of silent pressure. Most rooms just creak and rattle like crazy down that low. So basically you are giving up some room pressurizing capability or a loss of weight to the bass on certain scenes. It's by no means a deal breaker.

I
think most are trying to point out that you are not getting the full benefits of your investment is all. To each is own.
That is exactly what they are trying to point out. What isn't being taken into account is the size of the room nullifying the benefit I am not getting either way. I am happy with what I have for now.
 

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I am extremely curious what the other subs were there are looking at. Are they the crap they find in big box stores?
Oh nothing like that. For the above scenarios it is usually all of the quality ID guys.

Tom V.
Power Sound Audio
 

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Hi all, a few more things heading to the outlet soon. I don't think I can post pricing here but just pop into chat or email if you're interested.

one s3601-b
one v1510df-b

three mtm210 (sq-edge)

Thanks!

Tom V.
Power Sound Audio
 

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I agree with Bear's observation that it's typically better to spread subwoofers out, usually on opposing walls, to take advantage of the benefits of helping to reduce peaks and dips in the frequency response.

I would also make two theoretical observations. First, two subwoofers occupying the same room are said to be "collocated". And, two identical collocated subs should average a 6db increase in SPL, across the full passband of the subs. Of course, as climber07 pointed-out, there will be individual peaks and dips where more or less than +6 is occurring. In theory, however, if you played pink noise (~30Hz to 80Hz) and measured the change in SPL, the full 6db increase would be there.

The second observation is that subwoofers don't actually have to be stacked in order to be "mutually-coupled". They just have to be within 1/4 wavelength distance of the frequency where mutual-coupling occurs. For example, to be mutually-coupled at 80Hz, the subwoofer separation would have to be about 3.5' or less. At 40Hz, two subwoofers would be theoretically mutually-coupling when they were 7' apart. The lower the frequency, the further apart the subwoofers could be for the full 6db of reinforcement.

It's a little hard to be sure sometimes where theory leaves off and something unexplained occurs. But, I believe that the above constitutes an accurate explanation of the theory involved.

Regards,
Mike
 

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Yeah, good choice if you’re only movies.
See... I'm mostly movies in my setup, but I definitely prefer the sealed a lot more than ported for which I have detailed the differences earlier in this thread. I think the benefit to my home is the ideal room construction as well as a wooden framed couch that responds readily to the wide gamut of vibrations. And I'm on a concrete slab as well... albeit with shaggy 70s carpeting. :D
 

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I already have a plan to add a 3rd sub to the back right corner of my room. Most likely it will be after Christmas though


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I think it's safe to change your avatar pic:)
 
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