Bro @GundamUnicorn,
Before u decide to buy any sub, it is vital to discern if the wide band deep valley is due to:
Could u post the above FRs? These FRs will be able to tell us what is happening in your room to a good extent
Thanks havenāt got a quiet moment to do any sweeps. Thinking to shift sub to front wall mid pt to see if it helps. Havenāt got any longer cable to move to any other possible locations. Will post them once available.
You canāt randomly move your sub bro. At least try the crawling method, just google for it
My room are tiny so practically thereās only a few spots for placing the subs. Currently is right side 1/4 of front wall. Whole front wall is free except where center speakers is. So I tested front center and side wall center for comparison today. It seems side wall mid pt has better graph, only concern is itās take valuable floor space.
Back is occupied with a big 3S sofa leaving a narrow gap 300mm between sofa n built in wardrobe. What happen if I stick a svs300micro in that spot? The drives will be firing into sofa at one side n into wardrobe doorā¦ thereāll be rattled?
Iām afraid itās not about buying your way out of trouble.
The Starke is pretty tight. I owned it before
REW will allow simulations, and give you an idea of which positions help. Then you narrow it down based on your own limitations.
Then you measure your room, show those keen on helping you, and diagnose whatās wrong before you plonk down hard earned $$ā¦
But basic principles is two equal subs even outs the curveā¦
Yes aware so Iām looking at better sub locations and the right side wall mid pt side seems a better graph
3P comparison
Side wall mid pt
These graphs are useful! The side mid side wall placement has the least serious dips amongst all 3 and can maintain the bass quite well till 130hz.
I would use this placement to start with.
Could u use this sub placement, measure and post the graphs I mentioned earlier? Then we can take the next step to see what are the issues.
I already did use the A1 Evo optimizer to check the response with mains using the 1/4 of right side wall and the selected xo 150hz gives much better FR. Iām settled on sub placement now and remeasures whole system again this weekend. Any concern for xo at 150? Bass integration with mains poor?
Seems like no urgency for adding 2nd sub for now but eventually will.
Thanks everyone for your help
Just take note on safety , please check all your mounted equipment example . Wall mounted speakers , projection screen and projector.
Ensure you have better hardware or some adhesive to ensure it does not turn loose ,prolong use off low frequency those item does come off .
Have fun on the new toy .
Great!
For your xover w mains, u seem to be saying that setting xover at 120hz does not yield a good combined result w your mains? Like what @Wechnivag mentioned, it could be a xover vs timing issue, causing cancellations around the xover point. Based on your subās FR in the new position, your sub+mains combined FR shld maintain quite well when crossed between 100hz-150hz. Need to see the FR to know.
Pls try to post the 3 categories of graphs i mentioned when u do the remeasure. Then we can help u see where is the issue. We donāt know what we canāt see.
Graph #3 that i mentioned earlier, measure using both 120hz and 150hz xover w your mains. So that members can help u take a look at the sub integration w your mains, b4 and after they combine. And check for cancellations.
So graph #3 should have 3 graphs in total and each graph will have 3 FR lines.
Looking fwd to see the graphs!
finally go ahead and add 2nd sub, the modest KEF HTB2 which suppose to comes with the KEF KHT 3005 i used as a package but stupidly didnāt took it, thinking the Starke SW12 is sufficient and not required that sub. With HTB2 filling the gap in 50~200 hz, the XO is better now as the satellite 3001 rolls down around 150hz. still no ideal, but did some measurements:
Center
FL
FR
Sub
Thanks for posting it.
The labelling of the FR lines are confusing. And u did not mention whether they are measured w room eq on or off.
For the subs only graph,
For the FR and FL graph,
Suggest u hold first. More might not be better.
U need to be v clear what problem are u trying to solve actually? Itās not clear. 30-50hz is not an issue from the graphs, deploying a dsp for the subs should give u a good sub response from 25-130hz.
adding subs of different model and make is highly unadvisable. Unless u have the tools and know-how to integrate them well. U already have 2 diff subs: starke sw12, and a kef htb2. Then u still want to add a 3rd non identical sub svs micro. I feel it will have more cons then pros. Plus in such a small room w limited placement positions, do u really need 3x subs?
Sorry I am v confused. I thought that the previous conclusion was that mid wall placement for your sw12 gives a good FR to work with liao? This shld likely give a nice response bwteen 25hz-150hz if u have the know-how and tools to do so.
Secondly, we asked your assistance to remeasure and post the relevant categories of graphs using mid wall sub placement to move this to the next step. Did u do that? Could u post graphs of that pls?
We are investing time to help u solve the problem in a guided manner. So we appreciate it if u can take those steps first and post the graphs that members helping u asked for. 
sorry for the confusing posts haha, i had previously lived with sw12 at the side wall mid pt placement for a couple of days but found it to be not practical so had shifted back to 1/4 pt and it had been there since.
Iām using Audysessy One (A1) optimisation script thatās automates vol leveling/time alignment/xo/eq using REW from measurements extracted from Audysessyās MultEQ app. After running the script+REW, the following fronts and sub responses are produced:
Sub -
Front Right (same for FL)
below are the raw individual sub responses from MultEQ which i didnāt include in the sub graphs as their levels are much higher and I donāt know how to offset them to same level for easy comparison 
So A1 will using these raw responses and find the best combination using REW and the result is SW1o.
I really appreciate your help and advice. Thanks!
PS:
Xo are: C -90, FL/R - 120
A very simple question for youā¦if you said HTB2 placed at left of sofa and you ābelieveā that by getting another HTB2 should be able to āfill upā the dip between 30-50hzā¦so did you do measurement by moving the HTB2 from the left to the right and if so, what does the measurement tell you? Does that āright side of the sofaā position truly fill in that range of dip youāve mentioned?
Againā¦I do not advocte the different make and size of driversā¦e.g. SW12 vs a 8" HTB2 and now you are even considering a SVS 3000 micro which is an 8" driver. You might be better off getting a good pair of subs that closelt matches the amplification of your Starke SW12.
I did move the htb2 at different positions when I got it to see which position has the best potential using REW alignment tool and determined left of sofa should be the one before I run thru the A1 optimization script. The right side of sofa was one of the tested positions. So I used that response and aligned with the combined response sw1final shown in above post which yields good result in REW. Thatās why Iām considering getting another to smooth out the response but they are good only to 30hz. Alternatively, Iām also thinking replacing the HTB2 I have now with Svs 3000 micro which according to specs is 23-240hz Ā±3db so can provide more low end.
Ah I see. No wonder.
Cos that placementās FR for sub is good and likely donāt need another sub.
A 3rd sub likely wonāt help much in your case I think (plus u have limited placement) and it might spoilt the soup.
But, I would do what @desray suggested, change your 2nd sub to an identical sub e.g. sw12. You are likely wasting money getting a 3rd sub. I would rather channel the funds to get another sw12, sell the htb2.
Your latest subs + speakers FR is not that bad. I would try running a house curve on your subs that has a 5db-8db slope from 100hz-30hz with your current setup.
But seriously speaking, if u can live with the sidewall midwall placement for single sub, perhaps that would be the best and simplest.
