A lot has changed over the years. Many of the assumptions around studio monitoring are based on the older practices and the challenges of rooms from the 60s, 70s and 80s...

Other fields such as live sound, theater, gaming, cinema, automotive etc. have adopted and optimized systems with subs, multi-channel, DSP, etc. These technologies have gotten very good and are now fully applicable to studio monitoring. In fact, many modern commercial monitors incorporate these into the products themselves. While it is common to want to avoid adding DSP to the monitoring chain, the fact is that it is already there in the DAW, outboard gear, power amps, monitors, etc.

After reading through this thread I'm wondering, for a smallish halfway treated room with full range mains and one sub, would it be better to:

1. buy another sub (currently using a JL Audio Fathom f012, could pick up another one)

2. buy a pair of PSI AVAAs

Which would be a better choice, and why would I pick one over the other? I.e. what solution is best suited to which situation/room?

Cheers,
Thor

Hello,

With an another sub (in stereo) you increase the emissive surface and reduce the distortion for the same spl.

Wow, that's actually a tough question for a few reasons! Reason #1 is we found the AVAAs to be capable of significant absorption but not in all the rooms we tried. We thought for sure that the smaller rooms with very regular dimensions would be ideal for the AVAAs as they have pronounced boosts and dips in the room modes. However, the two rooms that worked best were actually the rooms that were irregularly shaped. This involved 5 rooms so not a large sample to generalized from. So basically you have to try them out in your space to know how well they will work.

Multiple subs work extremely well in smaller, regularly shaped rooms that are not fully treated (especially lacking effective bass trapping). For the best results you would want to do use a professional multi-channel DSP unit and do a room tuning and system calibration. The subwoofer you have appears to be pretty expensive so a good DSP plus another sub would actually cost more than (2) AVAA C20s plus you need to learn to calibrate the DSP channels or get someone to do it.

One recommendation would be to see if you can try out the AVAAs and return them if you do not achieve your target results. This way there is no risk or harm in testing them.

From my own experience I believe that two matching subs, one in mid of front wall and one in mid of back wall can work extremely well. I never used the sub you have, but it looks like an excellent, high power unit. When we tried the Subwoofer Pro's in this configuration it sounded great, two did the job versus needing 4 when using more modest subwoofers

Here is a new room we just worked on, adding the multi-sub system, with a number of refinements that have produced results that even surprised us. In particular, full range extension from 15Hz, near perfect time alignment and unanimously positive response from a number of pro engineers who had a chance to spent some real time in extended listening. Everyone describes as a new experience of hearing true full range where everything is properly aligned and it 'feels right'. Results attached are before and after the dsp/alignment/tuning process

Main monitors - ATC 20s
Subs- (4) HSU ULS-15 MK2

That looks great SteveGTR. What are you using as DSP?

Thanks, in this case its the Danley 8 channel dsp unit

Nice, and from what I read the listening experience matches the measurements.

I see you chose a very flat target with no bass lift, and with full range extension and smooth response it often ends up sounding balanced like this, the bass level sounds just right.

Yes, you obviously have experienced this! The reason I say that is when using conventional systems it feels better to have a tilt or BK style curve. However, when experience time aligned, full range linear energy all the way down to 15Hz, it sounds more natural to be flat. It is really an amazing experience and in many ways challenges our previous experience and assumptions about sound, rooms and speakers!

That looks great Steve. A little off-topic but can you share how you decided on the HSU subs?

Alistair

We have been testing every sub we can get our hands on. There are few professional options at reasonable prices available. We prefer sealed cabinets, high power ratings and 15" drivers. It is especially hard to find options that allow the user to defeat the onboard crossover/processing. We ordered the HSU units based on specifications and reviews. The results exceeded our expectations by far, especially at $799 per unit.

Yes, full range does matter. It is really most about sound quality and not so much about more powerful and house-shaking bass.

And it has to be experienced, on a system properly set up so that both frequency response and timing are reasonably good. The usual belief that 40hz is all you need is a result from what most people have experienced.

Exactly!! When you hear this kind of extension with good time alignment it is a whole new experience and challenges you to re-orient your expectations and perceptions, it is quite amazing!

Fascinating thread, except for the bickering...

Currently, I've got 2 15" subs, one each to go with the left and right main speakers. Stereo. They are effectively in the corners of the front wall, the mains are up at ear level and the subs are on the floor. I've time aligned and experimented with crossover points and slopes to get quite a good response. The room has quite a fair amount of bass trapping: VPRs, corner traps, etc.

If I was to add two more subs after the teaching of Geddes, where should I put them, and how should they be bass managed?

If I read him correctly, I would put the next sub (third, in my case) in the center of the side or rear wall. Then the fourth would be some place off the ground farthest away from the other three. Correct, or am I oversimplifying?

Would you recommend mono summing the left and right bass to feed these two new subs?

I've got a miniDSP system with enough capability to do this anyway that makes sense.

Thoughts?

Geddes system does not require matching subs or even very specific locations. His method has you start with one big sub to excite all the modes and then calculates what each additional sub needs to do to enhance the response. If you go with that method you can use his tools to give you the needed response.

We have tried that method but tend to prefer the approach outlined by Floyd Toole and Todd Welti by choosing a placement and number of subs that fits the situation and then using DSP and time alignment to bring it all together.

How big is your room? You might not need additional subs, it might just be a matter of placement and then perhaps DSP/Time aligment to bring it together

How would a stereo monitor controller with integrated DA work in a multi-sub system? For time alignment I could see the need to delay the mains to properly integrate with the furthest sub. This means doing the needed DSP pre-DA which is also pre-volume control. How do you get the sub level(s) to track properly with the mains?

It varies by different controllers but one scenario is that output of the controller LR feeds the multichannel DSP. This can act as a master volume and the DSP does the splitting and summing to the LR mains and subs

Another is the the DSP is before the controller and the LR go through the controller but the subs do not. In this scenario when you switch away from these speakers you need to also mute the subs

Hi Steve,

it's not clear how you got rid of those spikes around 200Hz
I guess the subs don't work that high?

Thanks

That's a great question! What is going on is the effect of harmonics and modulations. The natural room modes jack up key frequencies and those anomalies get reflected in the harmonics above. When you smooth those out you positively impact the harmonics above them as well. This is why the listening experience is so dramatic because you hear the mids and highs cleanly without being imposed upon by the room modes.

Fascinating stuff. I really want to try this. I just re-read the Harman pdf on this.

If you are summing all of the subs as one channel,
how do you time align the subs if you're not sitting in the center (lengthwise) of the room? If you're sitting at 38% from the front wall, for example, you'd be sitting closer to the front sub(s) and further from the rear sub(s). Or, do you just sit in the center of the room?

They also had some configurations where the listeners would not be equidistant from the subs in the study. I had always assumed you'd want each sub to be at equal time. So if sitting closer to one it would be timed differently than the sub further away from you.

typically you are crossing over somewhere around 80-100Hz. At these frequencies the subs are working squarely in the pressure zone of the room. Think of holding a long balloon and squeezing one side, the whole thing expands on the opposite side. It's not really the same thing as higher frequencies and the precise time alignment varies by the room it's in, the volume, shape, response, modes, etc.

Any thoughts on the HSU vs Rythmik subs? 12" vs 15"? And also is the minidsp 4x10 a good option for integrating the subs?

Haven't used the Rythmik subs, but I cant say enough good things about the HSUs, they are totally professional and sound great at an extremely reasonable price.

I havent used the MiniDSP 4x10 either but it seems to have a nice feature set. I have seen their software and it has good support and nice extras such as integration with REW

Thanks. I'm open to other suggestions for handling the crossover/management.

Hey Steve, are you still likeing the Darnley labs processor?

How crucial is placement with 2 subs? Would having them fire perpendicular to each other be a nightmare or potentially ok?

Probably not a problem at all. Low frequency sound is not very directional at all. The most important point if you have more than one sub, is to place them appropriately in the room so that they compliment each other in killing the modes that can be killed, and smoothing out and extending the low end. That's not easy to achieve, sometimes. It needs many moves in small increments. Or you can use the "plane wave sub array" (sometimes called the "double bass" sub array, or "double sub"), which is easy in theory, not so easy in practice, but can produce excellent results.

- Stuart -

Earl Geddes thought of you

Multiple Subwoofer after Geddes

Hey, interesting stuff.
I'm in the process of turning my bedroom into a "proper" mixing room. I have no treatment yet, but will tackle that soon. Room is all concrete walls, about 5,1*3,1*2,5m³. Front wall has an offset window, but is free for putting subs anywhere. Back wall is mainly taken up by bed and door. Side walls have some furniture (unfortunately in the middle...). I have K+H O110s plus Adam Sub7, I could quite easily get another Sub7 and either use my PA's driverack or get a miniDSP.
So, where would you experts put the subs?
Harman suggests mid of front and back wall, but that would leave me with severe 55Hz SBIR-dips from the sidewalls (which I could treat, at least on the front wall). Would it make sense to try and fill those dips with the mains?
The other "obvious" option seems to be on the front wall, 1/4 from the sides, eliminating the side wall SBIR dips, but leaving the big 30Hz 1-0-0 node untouched. I wouldn't really want to use more than two subs right now. Any Thoughts?

Cheers, Peer

If you find the need for a high x-over (due to SBIR related to floor) then place subs under (or at least close to under) the mains. If not, at least close to front wall:

Add a sub instead of even more bass trapping to even out freq response?

1.0.0 can be nuked by DSP assuming somewhat treated and sweet spot not close to the nodal line: How to tame a resonance at 22hz