Newbie help with sub choice and room placement

[awdtsi]

Hi, I am building my first theater room and have a few questions regarding subwoofers and placement.

 

First, my Theater room is in the basement. Concrete floor with carpet, 3 concrete walls, 1 interior drywalled wall and unfinished ceiling painted flat gray. Room dimensions are 12' wide, 19' long and 7' 4"' to bottom of ceiling joices. There is a 4' wide hallway at the front left of the room and the stairs come down the back of the room.

 

My audio equipment is a Denon 1913 rx, Infinity Primus 150 fronts, Infinity PC251 center and Dayton SAT-BK's for sides and rear. I initially purchased a Dayton SUB-1500 as my budget is not very large.

 

I did a quick setup with the sub in the front right hand corner of the room and was not very impressed. I have a horrible null where I would prefer to sit, about 12 - 13' from the front wall and centered in the room. The back of the room had decent bass but it was almost non existant in my prefered seating location.

 

With a budget of under $400 I was wondering if a Premier Acoustic PA-150 would suit me better or would you suggest possibly getting two $200 dollar subwoofers and place one at the back of the room?

 

I am not opposed to a DIY solution if it isn't too expensive. I'm already over the WAF budget lol.

 

Thanks a lot for the insight,

 

Ryan

[maxmercy]

Multiple subs will help, but first, try other locations for the sub you have.  Do you have measurements?

 

JSS

[FOH]

+1 on the measuring

 

a few things;

sitting in the middle, front-to-back, is problematic ... as you're seeing. it elicits significant nulls in response. however, this is easily addressed via placement experimentation and seating location experimentation (often not possible).

 

outdoors, there's be no problem, you'd have nice smooth response. but move indoor and add boundaries, creates reflections and resonances, ... it's all about resonances, or room modes.  

 

 

three key issues;

1.)  a room's dimensions determine the resonances

2.)  sub placement determines which resonances are excited

3.)  listener location determines which resonances are heard 

 

the firm concrete walls/boundaries, exacerbate the issues, bass trapping would help significantly, but first placement strategies.    

 

a sub in a corner excites maximum amount of modes, bring it out mid sidewall if possible, or off the front wall somewhat, and out of the corner.

 

a second sub alleviates much of these concerns, if placed one in front, one to the rear.        

 

for a relative newbie diy, I'd examine parts express combo cabinet/subwoofer (dayton ultimax sub and cabinet), sorry wouldn't allow me to link

 

[awdtsi]

Thanks for the reply. I will experiment more with placement once I get my new sub. I'm thinking of going with either the Dayton DIY UM15 with knockdown box or the RSS460 HO 18" with knockdown box. I am also torn between the Inuke 1000 and 3000 DPS amps, as I want to supply enough RMS but also want to keep the cost down low. Any recomendations on which combo would offer me the best babng for the buck?

 

Thanks again

[awdtsi]

I also want to note that once I end up getting everything set up in a week or two I'd be very interested in what you would recommend as far as bass traps go. I'm pretty handy and would like to try a diy bass trap. I've read up on it a bit and it seems like it would be very beneficially to my room.

[FOH]

Bass traps all depend on what material you have to use, and how much space you can sacrifice.

 

Very briefly, using 4" rigid fiberglass, you span as many corners as possible. Using Safe-N-Sound rock-wool based trap, stack 'em up super-chunk style. If you can allocate maximum space, go the cheapest fluffy insulation, as thick as possible super-chunk style being mindful not to compress the product (occasional netting or chicken wire, etc.).

 

Everything works, just trying to maximize material usage...ie., one can stack rigid as thick as you want in a corner, however that amount of product could be better utilized spread around the room straddling the corners,...in that, coverage area trumps one über trap.

 

Most all residential rooms need about as much LF trapping as you can give them. That said, you can get to a point whereby too much MF/HF energy is taken out of the room, which can be quite detrimental. So facing a treatment section with plastic Visqueen or craft paper returns the mid and high range, and focuses the absorption on the LF.     

 

Post trapping subjective results will be dramatic ... tightening up the bass transients and increasing bass detail and clarity. Adequately damped listening rooms/HTs are the exception.

 

Good luck

[maxmercy]

Great advice.  FOH knows what he is talking about.  I prefer rooms as dead as can be, cancelling modes with multiple subs or SBA/DBA and absorbing the rest if possible.  Some like a livelier room.  All comes down to preference.

 

JSS