It looks like a great product line and has cool integration with REW. At the time we didn't see one with enough outputs that had balanced/xlr lines to run 4 subs and two mains. I think they have a multi channel with unbalanced RCA outs though, and, there software looks great

I've also played with some multi-sub setups

It seems to me that the big shortfall is that it's effectiveness is inversely proportional to the effectiveness of the rooms LF treatment. Ultimately in free space, subs that vary in distance (or time of arrival) to the listening position will interfere with each others response.

So the downside is any treatment you do add to the room will actually tend to make the multi-sub less effective.

If you look at Dr Geddes approach, he is adamant that you DON'T have any ER treatment on the sidewalls. Instead the constant directivity speakers are used to eliminate L speaker to Left side reflections- but then the downside is that left speaker to right wall reflection is effectively the ISD termination (which is going to be less than ~20ms in most rooms). There was a thread where he reluctantly admitted to having some sort of cloud/kicker on the ceiling though.

Also Geddes advocates only one full range sub, and then the filler subs to be bandpass enclosures that are custom built to cover the Schroeder range (and not below)- I guess to minimize the need for time correction. If you look at his (*ahem* aggressive) posts over at DIYaudio he certainly does not approve of most multi-sub implementations.

IMO Dr Geddes overall approach is an amazing balance of available compromises- but I'm not sure it takes into account the idea of a bespoke listening room. I heard his setup at RMAF a while back- it was frankly stunning for such a humble setup. Totally the wrong market for his message though...

Hey they have units with balanced outputs like this one:



Or this one that has both rca and balanced:




The green sockets (called phoenix ? i see them for the first time) are balanced outputs and you get these cables with it:

Thanks for piping in Ryan, it's great to talk with others who have experience with this. My take on Geddes is that he is very advanced in his understanding and implementation, and, pretty unique in that he has a full understanding and real engineering abilities in sound reproduction as a whole system- actually designing speakers around the way they interact with a room. As you say I don't think his work is necessarily aimed at bespoke listening rooms or music production spaces. It seems many people who equip nice home listening rooms actually prefer early reflections whereas audio/music types perceive how they smear things and that too many early reflection makes it hard to listen/mix. Would love to hear a full-on Geddes room!

What I have been interested is how to take the more typical residential rooms we all live in and bring them up to a very useable professional level for music production. I am 53 and started playing/recording guitar in pro studios when I was 16. I have composed, performed played and recorded all these years and worked as an audio engineer in the 80s and 90s. Even most of the big studios were generally disappointing in how they sounded, ie you could not simply listen to what you heard and trust it. Nowadays it seems like most people are working in either residential or light commercial spaces which are even worse then the big studios of yesteryear (mostly because of small room modal type issues).

There are awesome acoustical products these days to help address reflections, diffusion, absorption that are all effective in highs, mids and even low mids. However me and my obsessively nerdy music/audio friends have struggled for years and year to make real progress in our residential rooms with being able to trust the low end. All of us have been told over and over to keep adding more fiberglass products and when that just does not work add more "bass traps" - except these dont really work either, at least the ones that anyone can actually afford enough of and can physically fit in these rooms!

This is where the multi-sub thing caught our attention and being ridiculous obsessive nerds we have gone somewhat bat-sh*t-crazy in testing far too many iterations for sane people!! Trying different speakers, placements, DSP units, ways of tuning them, brands of subwoofers, etc. and yes we have very annoyed spouses and contracts in place to NOT play pink noise or sweeps while they are home!!

But the bottom line is that multiple subs along the lines of the Harmon research allow you to take an otherwise acoustically crappy residential room and be able to really hear and trust the low end. Is it a Northward level room- Of Course Not!! But it is possible to create a trustable reference listening environments by simply adding 4 subs, some smarts around configuring a DSP processor, careful placement, etc. --YES!!!

BTW- here is that same crappy room I posted before using the JBL 308s mains with cheap-a$$ Behringer subs with both the 2 sub and 4 sub config....

good to know- thanks

Steve, you have been granted Gold Status in RTA (Room Tuners Anonymous)

RTA - Room Tuners Anonymous

Keep up the great work!

Joe

Joe, I dont have a problem, really, I can stop anytime I like, I choose to do this

....gotta run now and shoot the new treatment location



thanks!

On the plots with the subs the FR flattens up in the 250-300hz area.
What crossover frequency are you running?
If running it above 100hz can you hear the subs physical location?

Interesting stuff!

The crossover frequency varies depending on a bunch of factors but is it generally below or around 90-110Hz

with all 4 subs firing the bass is extremely even across much of the room and does not localize, it just sounds like it is all around you. If you turn on and off individual subs it does move around and you can steer it forward or back with volume levels, but generally it has an immersive quality and you cannot localize it. There is some eq up in that 200-300 range to help flatten it out some

This concept is enlightening. Steve, for those currently mixing on just a pair of nearfields or midfields, what would you say is the best practice to help the low end? Simply add 2 (or 4) subs to the system, and locate appropriately as previously outlined?

I suppose each sub (including DIY made subs) will have unique specs, e.g. faster/slower response time, sound quality, noise level.. I notice you mention the Behringer. Any specific recommendations for mid & higher-end studios using high-end monitors (DIY or off the shelf subs) ?

Thanks.

Not doing corrections in parallel / symmetrically is a pretty bad idea yes.

We're keeping an eye on this technology, but we never needed it for work so the only intensive / in-depth experiences we had were with the systems / software manufacturers who often came to a studio we built to show us extensively what it can do and try to sell it to us. Conclusion was always the same, although some systems were much better than others.

Have you used/tried the SAM system from Genelec?

Have you talked to Ruairi about it? Still in for this.

Yes, but I never use it. I prefer to do any correction manually with separate DSP for full control.

What DSP correction would you recommend for smaller studios with semi-treated rooms (think DIY) ?

The Behringer was mentioned because we tested it and it is by far the lowest cost components available. They have their Behringer DCX2496 Ultradrive Pro DSP ($299) system and the BEHRINGER NEKKST K10S Subwoofer. This would be the cheapest way to go, it works but we could hear some degradation when processing the L/R mains through this unit.

The JBL LSR310s subwoofers that I posted results from earlier are probably right in the mid range. They are pro quality and actually allow you to defeat the onboard processing so you can fine tune with an outboard DSP. This is an important point because very few commercial subwoofers allow you to defeat the onboard processing.

On the mid/high end the Subwoofer Pro 12" units sound awesome!

All of these configs sounded really good, but you do get what you pay for and the JBL sounds better than Behringer and the Subwoofer Pros sound better than the JBL 310s!

MiniDSP 4x10 Hd / 10x10 Hd.

Not recently. I think he may even be here, selling the house.....
I will get back to it in time though. Thanks for approving it.
DD

I think the assumption that adding a second sound source will help in accuracy is false. The issue with sound is it is a 4 dimensional thing. You have 3d axis of sound waves and their interference with each other then you also have to factor in time. The biggest issue facing achieving a good monitoring environment is ringing. This is most problematic in sub frequencies where the wavelengths are very long or longer than the room itself so can self oscillate making nodes. You are better off with a tight monitor if you can't fix your room issues. Adding a sub might cancel some nodes or smooth them but you will still be reflecting sub around the room.

You absolutely need to be absorbing or diffuse scattering those waves to deal with the real problems. I'm a bit annoyed anyone would suggest two subs, which is expensive compared to acoustic treatments is a solution.

Just to be clear, this discussion is not about using multiple subs to increase the energy in the room but in fact to contain it, cancel it, and, average it out at ~100Hz and below because of exactly the problem you describe. There are specific ways to place them based on research/testing that a number of us have been trying and it turns out they really work. This is not the typical suggestions about sticking one in a corner, or doing the "sub woofer" crawl to try to find a spot in the room that works for one listening position. The idea is to use multiple subs to create a drastically more flat low end response across a large area in the room.

What acoustic treatments do you find effective in these small room modal frequencies? We have tried a bunch of approaches but they all were less effective and actually cost more, I am hoping you can show us something for less $$ !! We just want what works best, fits in a small room and cheaper than multiple subs and DSP would be awesome!

I'm not suggesting that multiple subs doesn't help with flattening the low end it most certainly does help. But it's only half the solution. No bass trap can target very low frequencies "efficiently," because no matter what approach you use it will be very large and take up a lot of space. But porous traps can still have a profound effect as low as 30 or 40 Hz and most definitely do stop time related bass issues faster than ignoring that ring. Two subs makes the ring worse and higher up the bass region too, so you still need to compensate for it. Literally sheep's wool in wooden frames as deep as you can make it, floor to ceiling will cost next to nothing to make as deal with the issues. The less square the room is the the better the situation will become.

No, not if used properly.

In an untreated room yes most certainly it does. Even used right, the cancellation of waves goes both ways at certain frequencies and creates ringing at multiple new frequencies. Two subs doesn't cure the issue it only flattens the frequency spectrum by cancelling out the fundamental room tone. I've always used two subs and it most certainly can't just be used in any old room.

@ gowers , I take it you don't agree then? ;-)
DD

Let me try and demonstrate why I say you’re wrong, using the good old ripple tank simulator:

One sub placed against the front wall (all walls completely reflective, note that there’s no rear wall), playing a frequency that matches the first axial mode related to width (0,1,0):


As you can see; there’s a big null/node (stationary dark region in the middle of the room) in the sweet spot due to the standing wave created between the side walls (the dark horizontal line does not move when “playing” since it´s a standing wave between the side walls).

Two subs places symmetrically against the font wall, playing the same frequency:


As you can see; the two subs together create a plane wave like behavior, completely eliminating the troublesome null in the sweet spot related to the first axial width mode (0,1,0). Again; do note that there is no wall drawn on the right hand side; the rear wall (not in any of the examples), since I´m focusing on issues related to width), so the wave front in this example is continuously propagating from left to right so the vertical dark lines shown here are not nodal lines (like in the first example where the wave is interfering with itself, bouncing back and forth between the side walls creating a standing wave. In the first example; the dark horizontal region is stationary and thus a node).


How about if we place the single sub in the center of the front wall:


Well, also kind of a plane wave looking thing going on, but since the source (and receiver) is in a null for the width mode; not much energy will be produced in the sweet spot (or anywhere else for that matter since there’s no rear wall to create any length modes …)


So what about the second axial mode related to width? Well, one sub:




Two subs:



As you can see; using only one sub, there’s definitely a high risk of a resonant peak in the sweet spot (and if placing it exactly in the null; you´ll have the same problem as above: close to no pressure in the sweet spot), but with two subs; there’s still close to a plane wave behavior, so no resonant peak (again; the vertical dark lines are not node lines since the wave progresses from left to right). This makes sense since if you fire up your polar plot calculator and use two woofers spaced about 1,6 - 2 meters or so apart (a normal distance between monitors), you´ll see that you get a polar pattern that is down close to minimum at 90 degrees for the frequency matching the second axial width mode in a normal sized room (about 4 meters wide, so about 85 Hz), so not much energy is directed to the side walls: perfect!



Finally; one of the biggest advantages of using subs (or woofers close to the floor) is that you can eliminate the otherwise troublesome cancellation related to SBIR due to the floor bounce by crossing over to the mains above this frequency range. This normally happens in the 120-140 Hz range (depending on position of source and receiver naturally) and if you want to cross over to mains as high as about 150 Hz or higher; you’re bound to use two subs (dedicated L & R sub).

I´ve never ever been in a situation where one sub was a better option than two (and I´ve done this for a while now …) even in poorly treated rooms.

You seem pre-occupied with frequency response over bass smearing issues from using two subs. The relatively simple task of moving one sub and treating the room so the listening position is both time coherent and within tolerable frequency responses is a far more reasonable a solution. Most speakers don't need a dedicated sub, especially if you are dealing with small rooms. When you say better, you mean flatter, but that's not the only thing to consider and I would argue it's has less value than you are currently placing on it.

It seems like you completely missed my point ...

Please read my post one more time.

Jens is talking about modal issues, which cause both frequency response and time response ("bass smearing") problems. You are separating two things that cannot be separated in this context.

How do you define "bass smearing"?

Hello,

When the two sub play a different signal and not the same signal, what is happening ?

Thank you

Is there even a possibility to have a completly flat bass response, but lots of ringing?
I can't see how this could be possible well below the schröder frequency.