Eh hem!...Subwoofers... What do ya know?

Also ...

If your speaker is solidly above 6 Ohms across the bass, you can disregard my caution. :)

So far this turned out to be not another non sense poisoned discussion, seems subwoofers are "a thing to avoid" for the usual trolls,which is great

We are getting now into time alignment, dsp and such, keep it coming, I will take my minidsp mic and rew out of storage and do some measurements on my own system.

Thanks to the OP, I bet the short cryptic title is a deterrent 😉

@erik_squires thanks good info;

I agree the using a pre-out (or active crossover) the preferred way and so does JL audio, but in my case I am running my XLR only DAC directly into my Amp; I will need to play around in the speaker level input regime until I either get an active preamp or the JL CR-1 (preferred);

I actually sold my preamp because I found no real advantage using that vs DAC direct; So, with those funds I diverted into the JL subs and some cables (I digress); Now, it seems that plan was half baked and I would have been better off keeping the pre and stretching the budget to get the subs but I'm already way over my audio budget for the next 10 years, lol

Anyone: please take a look at my setup; do you think the subs should go on the inside or outside?

https://imgur.com/Paj46Ti

-Cheers

I would try everything. Even keeping that position and aiming at each other . You may find only one is needed there and another in the back corner . Take one of them place it on your chair and check the room for standing waves as noted before . Then place the sub where the bass was the loudest. And keep them turned down . Or the bass will sound loose . 

Good idea davekayc
Keep all options on the table!!

The JL E-112 subs have a fair amount of built in tuning so hopefully this proves helpful;

Since I am nuts about this stuff, I am going to grab our nice Oscilloscope from work and my omni mics (or use a Laptop with some USB mics) and capture the onset of various test tones;

Once I have alignment temporally (overlapping first cycles of sine wave) and magnitude wise, I can play with the sub gain setting if the actual listening test prove excessive bass or what have you. I think the sub/speakers must align time wise for max potential, at least this is what I have read and it makes sense, on paper;

I was going to place a mic directly in front of the sub 3 inches away; same for the speaker woofers mic;
Cue up some bass tracks or just a sine test tone, trigger the scope on one mic and see how they line up. I am 100% positive if I run the sub off the amp output; the acoustic rising wavefront (the first cycle) will arrive at least 10 ms after the rising slope on the woofer output, due to the delays in the sub;

I will repeat the test at the listening chair to see how the alignement changed after wave fronts traveled 9 feet;

Once the entire room "pressurizes" does this time alignment still matter that much? -- we don’t listen to successive impulse trains...we listen to music in a complex environment with lots of interference patterns;

I can, in theory adjust the JL phase to exactly overlap the sine waves but the sub woofer will always lag the speaker woofer by a whole cycle. This may mean absolutely nothing  sonically, or it may be perceived as muddy or too fat.

It’s going to be a fun few weeks figuring all this stuff out!

If I end up hating the subs / can’t get them to gel, I guess I can toss them in our home theater or sell them;

In my previous post seconds should be milliseconds.

Dpac996 place your main speakers where they sound best first, then place your sub-woofers. Symmetrical placement looks good but may not result in the best sound. Use the sub crawl if you can place them anywhere in your room. If you have limited placement options, put them where you can and tune them the best you can.  

Also for measurements use your main listening position. I made the mistake of pointing the mic forward when I began trying REW. The microphone should be on a mic boom, pointing up, where your head would normally be. 

Downloading REW is free, you do have to join the forum. REW comes with a test tone generator that will sweep all speakers or just subs. The results from the sweep can be displayed in several ways. You won't need an O'scope. There is a learning curve and some equipment to buy but there are several tutorials available if you search. There is also a forum where you can ask questions. 

Good Luck!



        

I have 20.7 Maggie’s running full range with two stereo Kinergetics sub towers of 5x10” subs and two SVS 16 Ultras. When I hooked up the Ultras to complete my sub array I scared the s**t out of myself and literally jumped off the couch as my stomach flipped, water rippled in a glass on the table, wife jumped out of the shower and yelled about the thunder that was shaking the house to turn off the stereo due to the storm. That was out of control bass and what I suspect is the issue for a lot of people with integration.

I have a fully active set up with a Mini DSP, used REW with an Earthworks +-30k to measure the speakers and room. I followed the tutorial and used my own data in MSO and made 12 biquad filters per channel (8 of them) to optimize the room and have reached sub bliss. It is absolutely perfect and there are no modes.

I had a friend over for an extended listening session and they asked to take the subs offline because the 20.1’s are full range. They couldn’t believe the difference as they couldn’t “hear” the subs but not being on made a world of difference. No room for the subs as I read above? Make them into end tables like I did. Very WAF friendly with a 1” thick piece of glass on them. Guests have no idea they are speakers. 
If you can take the time to do it right with a sub array (four is the minimum in my opinion) you won’t regret it. 

I am reading the JL Audio article on sub integration.  I'll be responding to it shortly. Honestly it's a bit of a mess, but I agree with their main points.


As much as I like how well their room correction works, I find this article attempting to make things a lot harder to understand than really necessary. It's trying to scare you out of trying.

But their main point, that adding a sub is like adding a driver to a speaker design, is spot on, and exactly what I've said before.

Like they'd loose any money. :)

hifidream, did you have a chance to compare the Mini DSP / Earthworks with the Ultra's processing and use its three presets? I'd be interested to hear your opinion regarding their degrees of adjustability and ease of use. 

Hi m-db,

      I wish I could speak to it but I didn’t take advantage of the SVS DSP. I didn’t think it could really compare to the processing power of REW and MSO. Using those programs with the Earthworks Mic I could see what was happening in the room and angle, move, shift the speakers for an optimum result. As others have noted, placing four 150lb subs in the room can be challenging. I also was integrating two subs that don’t have the DSP built in so I opted for one total solution rather than mixing them. It’s pretty exciting to see the hot spots and what MSO does to combat them using time delay, inversion and some wild looking slopes. I also time aligned my mains to the listening position at the same time. It’s easier than you think once you try. It’s just a path that isn’t well tread and it took me a lot of reading and trial and error to get it all to work. I’m a firm believer that the two most important parts of the system are first your speakers then the room. 
I bought the SVS because of their quality 1,500W MOSFET amps and massive driver motors and bracing they have internally. They can keep up with the Kinergetics driven by my Pass amp very well. I will also say that the SoundPath feet offered by SVS are a huge bargain. I had nasty vibration induced distortion in the room till I bought those and put them on all the subs. The rubber durometer is perfect and totally isolated the subs from the floor and the bass became so much clearer. I also have everything connected via balanced cables, it’s dead quiet. You can hear a pin drop and the ‘lovely’ tape hiss on older recordings. 
The OP asked when we learned about Subs and I knew how important it was playing in an orchestra as a kid. There are vibrations from a live performance that can’t be “heard” but are essential to the experience. That’s when I started reading about music reproduction and the physics behind it. . . Love how accessible sound is. The highest sound we can hear is 1” long the deepest is 50’ long. It’s amazing. And once you know the science it makes sense why a sub array is such an effective tool to counteract the physics of the room. You’d need 50’ of dampening material to absorb the wave and prevent a back wave from reverberating in the room which simply isn’t possible and why one sub is usually so hard to integrate properly even with DSP as the other speaker waves are truly the vehicle for DSP to be effective. What a great hobby. . . 

I want to be clear on my position in a few ways:

• Multiple subs are great
• 1 sub, properly integrated is much better than most people know about.
  
• Hsu makes great subs too, and more people should try them.
  

Does anyone technically know what happens when you aim two subs at each other?  Say a foot or 2 feet apart . Is there an ideal distance apart to do with frequency? Does it have an affect on the opposing woofer itself such as improving the rearward movement of each other? Would have to be a specific distance i assume . A possible equation ?

Reason i ask is i have 2 x18” jbl 2245 aiming at about 20” apart and hung from the underside of floor . And they sound incredible . Not  boomy sound but accurate and on cue. They have a very black background. And only reveal themselves when there is very low program material. 

If you time align the back sub to fire when the front wave hits him and you also phase it 180 degrees, theoretically both waves cancel each other and you don't hear the reflections again

This is theoretically of course in the real world it won't happen unless the room have nothing in it, it is a geometric cube (or sphere) reflective materials all the same etc

I'm sorry I am assuming front and back subs, if you have them on the sides the effect kind of would be the same

And these are not my ideas or research, you can ask Duke LeJeune with Audiokinesis from which I learned everything I know about subs and which swarm array (trolls like the word or not) is the best bass solution I found after trying the conventional ones, he is IMO the one source of truth to go for these matters, I think he have commented in this thread already

Duke LeJeune is Da Man. Aka Audiokinesis, he has done more for this than anyone, which this will probably instigate a reaction owing to the fact his one fault is being blessed with an overabundance of modesty. 

Seriously though the research goes back to Dr Earl Geddes, and another whose name eludes me just now. Anyway, point being what Newton said, if we seem to see far it is because we stand on the shoulders of giants. These guys did the heavy lifting, the down and dirty grunt work of painstakingly measuring actual room modes in actual rooms with different numbers of actual subs in different locations. And then as if that was not enough they applied the brain power to first work out and then ultimately demonstrate- prove!- just how well lots of subs really does work.

Duke however is so much a part of the whole thing that not only did I learn about this from him here, but when I went looking for Swarm type subs and was able to find only two systems on the market, it turned out the other one was designed by Duke as well!

Anyway, congratulations! You did the research, asked the questions, learned what needed to be learned, and then had the courage to buck the trend and the trolls and do what's right. Good for you. Enjoy!

Does anyone technically know what happens when you aim two subs at each other?  Say a foot or 2 feet apart .

What do you mean? In phase? Or out of phase?

Is there an ideal distance apart to do with frequency?

What do you mean? Are we still talking about pointed at each other? Why would you even want to do that?

Does it have an affect on the opposing woofer itself such as improving the rearward movement of each other? Would have to be a specific distance i assume . A possible equation ?

Only thing I can think you might possibly be trying to get at is what's been covered a zillion times, that waves propagate and bounce and reinforce and cancel, everywhere and all the time, and at all frequencies. And regardless of which direction they were pointed first.

@millercarbon Very well said
Emphasis on this

his one fault is being blessed with an overabundance of modesty

Duke has made available to audiophiles an integrated multi subwoofer system at a great price. Kudos to him. 
There are three considerations when it comes to accurate bass performance. The woofer itself by which I mean the driver and it's enclosure, the amp driving it and it's integration with the satellites including crossover cut off points, slopes, phase/ time alignment and room control. There are plenty of high powered amps capable of great bass. More electronics are including digital bass management and room control with delay capabilities which makes integration a snap TACT, Anthem and Trinnov come to mind. It turns out the most difficult part to do correctly is the subwoofer itself. Making an enclosure capable of perfectly isolating a high power, long excursion 12" driver is very difficult. Put you hand on your subwoofer while it is playing. Feel that vibration? That is distortion. Any flex or movement of the enclosure is distortion. The ideal enclosure would be infinitely heavy and infinitely stiff. It would be a concrete bunker. This of course is commercially impractical. Designing the internal dimensions of a sealed subwoofer enclosure is easy. Making it acoustically dead is another story altogether. This is where the home hobbyist has a great advantage. There are a slew of great drivers out there and you don't have to worry about shipping and labor costs. You can make an enclosure as heavy as you want as long as it does not fall through the floor. We made killer enclosures with a sandwich of Corian and 1" MDF  Corian/MDF/Corian 2" thick. They weighted 250 lb each and when you put your hand on them you felt nothing. 

davekayc, two drivers operating in phase with each other are acting acoustically as one driver if they are within 1/2 wave length of each other at their highest operational frequency. It does not matter where they are pointed. As an example if the woofers are crossed out at 100 Hz, 100 Hz has a wavelength of 10 feet. If the woofers are closer than 5 feet they are functionally one driver assuming they are operating in phase with each other. I have two 12" drivers pointed right at each other 3 feet apart right up against the middle of the front wall. There are two other identical woofers one in each front corner. They are placed so that the edge of the driver is right up against a wall. They are over twice as efficient this way. They are all acting as one driver, one wave front. Since the woofers are right up against the wall the first reflection off the front wall is exactly the same as the initial propagation so essentially there is no first or early reflection. Since the drivers form an infinite line source there is no reflection from the side walls either. 

I would think that within a certain distance . One opposing driver would either assist or hinder the other at a given frequency. Taking all walls and reflective surfaces out of the equation . Dead of space. Think about a truly tuned exhaust. It reflects a sound wave within to increase power . At some point i would assume the area of an 18” speaker would be affected by the other . In phase. Question is how. 

http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm
This is the design used to build the subs . I built them exactly to design , 12cuft version