Not sure why you can't go louder... your speakers and receiver are more expensive than mine, your receiver rated for slightly more power, and mine can go louder and sounds great. My polk monitors have a sensitivity of 90db. The built in subwoofers shouldn't consume that much power given they're 8 inch and probably can't get terribly low. Hooking up my rythmik sub to the kill-a-watt it only uses a decent amount of power during movies when it hits the room shaking frequencies. You could try cutting off frequencies below 80HZ if you can and seeing how loud you can get. If you're looking for a sub I'll save you some digging and give you the best subs for the buck in various price ranges...
Sub $400... Acoustech PL-200 .. a boomy sounding sub... not very 'musical' but ample for movies ... 12 inch ported sub rated at 250 watts with 'bash' technology.
$400-800 ... Rythmik LV12R ... a nice step up... one of the most 'musical' ported subs I've come across... and ample for home threater as well... much flatter frequency response and goes quite a bit lower than the Acoustech. 12 inch ported sub rated at 300 watts with 'direct servo' technology.
$800-1200... HSU VTF-3 MK5 or HSU VTF-15H MK2 .... great bang for the buck.. plenty of power to shake the house... perhaps not quite as tight as the Rythmik for music but very close. 15 inch ported subs rated at 600 watts. Take note of their size and weight before ordering.
Just because the receiver/speakers are more expensive has nothing to do with loudness...
It's all down to tech specs. You don't defy the rules of physics because you spent more cash.
And Polk Monitors sound horrendous at loud volumes. I know, I have them and it's their perf at loud volumes that makes me want to replace them so desperately.
92db sensitivity is very high and only 86db at 10ft away? That reminds me of volumes you'd get outdoors! My living room is slightly larger, actually it's shared with the kitchen, but point being, my speakers are lowish 86db sensitivity and it's plenty loud.
Like other's have mentioned what were you measuring that's 86db? White noise, 1khz tone, whatever is playing on TV? The 1khz tone will be the loudest. I guess the easiest way to find out is to barrow a friend's speakers to see if something is blantantly wrong. Best of luck.
That's maybe for commercial speakers? This is why enthusiasts don't get commercial speakers lol. Funny you said 92 db sensitivity is very high and to me I'm thinking "Gosh... that's so low!" I've been looking at high efficiency designs though and for me, I think 94dB was the lowest sensitivity I'd go.
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I'm surprised Anubis didn't recommend this first, but I'd get new speakers. I'd NOT get commercial speakers if volume is what you're going for.
First off, if you were spending in the range of the speakers you got:
http://www.amazon.com/Klipsch-Reference-Flagship-Floorstanding-Speaker/dp/B00414VRH6
That's what you should have gotten. But since it's in the past, I would sell your speakers now.
I'd pick up this:
http://www.diysoundgroup.com/home-theater-speakers/elusive-1099.html
And build myself.
Sensitivity on those is 99dB.
If you want to go bigger I'd get:
http://www.diysoundgroup.com/home-theater-speakers/maximus-18.html
But they aren't out yet.
If you wanted to keep the design of the Deftech and you have woodworking experience and you want to cheap out I'd get:
http://www.diysoundgroup.com/home-theater-speakers/cinema-8/cinema-8-kit.html
and I'd add a custom compartment at the bottom to house a 10 inch subwoofer.
I wouldn't go with that design though. 10 inch subwoofer is too small to me, but that's me personally.
Those are the options I'd pick though. I would NEVER go with a speaker with such low sensitivity if playing loud is my goal knowing the little speaker building knowledge I've gained over the last couple of years.
Anyway, those are my recommendations.
Don't bother with separates either. You'll gain 3dB (just estimate off an SPL calculator based on the stats of your speakers), and that's just tiny. Building any of the speakers I listed, with your current system would net you 10 dB. Ya, it's more expensive, but if you go over and read on AVSForum.com in the DIY section, people have owned all types of expensive designs there. You just can't beat building your own speaker, especially if you're buying those commercial type designs.
You can also go to JTRSpeakers to get the level of quality speakers I mentioned in the DIY section of this post. However, you're spending a LOT of cash there but some of those are custom speaker parts I believe (I can't remember I do remember seeing their speaker builder post on AVS if I'm not mistaken. Could have been Seaton though).
The Noesis 212HT is the most covetted design if I'm not mistaken due to it's very very high sensitivity. But at $2299 a piece.... You could get most of the performance of that speaker in the 1099 design I listed. You can find the listening impressions of these speakers on avsforum. I doubt the DefTech's you have would be anywhere close to the Noesis212HT or the 1099 design though.
So to sum up.
Klipsch Reference Series - For Cheaper Pre Built
DIYsoundgroup Speakers - For Best Price/Performance Ratio Humanly Possible and most work already done for you
JTRSpeakers - For high quality completed speakers.
That's my recommendation, but I'm assuming you want to get LOUD and don't every want to have to worry about not having enough volume. If I had your speakers, I wouldn't even use them. Sensitivity is a joke they wouldn't get remotely loud enough for me. But that's why they're commercial home theater speakers for the typical user who doesn't listen that loud.