Mix Challenge

Hi guys,

So, I'm looking for a very nice (and hopefully not too expensive) sub for my mixing/mastering studio for two main considerations:

- extend my nearfields from 45Hz (-3 dB) down into the 20s somewhere..
This also has another positive side-effect of taking the load off the nearfiled's woofer (say having the sub-crossover set at ~ 80Hz) so they maybe gain some extra clarity in the low mids.

- place the low freqs psychically in a different place in the room to lessen the room modes impact on the sweetspot.

My room is a bit larger than the classic "small" room (around L x W x H: 5.2 x 3.2 x 2.5 meters) acoustically treated but still has some problems in the lows of around -|+ 7-8 dBs .. so far I've been using precise eq correction to get that more into the -|+ 3 dB range. I really think getting a sub will help... what do you think?

So I understand that it needs to be more or less capable to reach the SPL that my nearfields do (118 dB SPL) I never use my monitors anywhere close that level.. so would a sub around 106-114 dB SPL be enough?
I also know placing the sub is very important.. anything else?

These made it to the short list:
https://www.thomann.de/ro/dynaudio_18s.htm

https://www.thomann.de/ro/dynaudio_9s.htm

also these but unless someone has something very negative to say about Dynaudio ...

https://www.thomann.de/ro/adam_sub10.htm

https://www.thomann.de/ro/eve_audio_ts110.htm

https://www.thomann.de/ro/adam_sub8.htm

This last one might be a bit too weak..

Though my experience is limited, I'd like to point out that a subwoofer is a difficult animal that does not make a studio more "mastering-proof" without going the full journey of room geometry/architecture and room treatment.
The sub in the project studio had always problems with the transition to the 3 pairs of monitors. Although there was professional tuning when the system was put together.
The monitors are on poles, a bit above the head of the engineer at his desk. The sub is sitting on the ground. It does not blend, the room is too short for that. We have to walk around the whole room, to find out about excessive bass, and we can hardly judge the pressure of the upper bass range in musical terms. Like you want to feel these Marshall amps hit in your belly, replaying the mix.
It is all about the context and unity, compactness. Breaking up sound sources can become problematic.
I think, testing 2 or 3 different sub cubes, and boldly change their position, and sending them back when not sufficient, might be inevitable.

If you are compromising a bit with available SPL power, the overload protection should have a very visible red light, else you might miss an excessive bass git slam or something..

^ Thanks for the input!

Of course adding a sub won't magically turn a studio into a "mastering-proof" one (although in my situation I think a sub will help a good bit just for the simple fact of physically placing the low freqs in a different place )

I will of course experiment with placement, I plan to also use REW+Measurement mic, I know placement is very important.
I will also experiment with height (and decoupling), lifting the sub from the floor until it sound right on that axis also..
I want to optimize the sound ONLY for one spot in the room so I won't mind it sounding quite totally off in other places in the room..

The reason these two Dynaudio subs don't have higher SPL (the 18S model for example specs at 110 dB SPL) for the given power is probably due to being a closed, non-ported designs.. however I don't think it will be a problem (not sure about that, will study some more) since I usually monitor around 60-70 dB, .. maybe 80-85 dB the LOUDEST ever! ..