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Author Topic: Determining Proper Subwoofer for Home Theater Room Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-21-2010 11:59 AM                     One reason for using the larger cone is to move the air with less motion and presumably get a deeper (lower) response. With that one really would want to go to a weaker compliance (say foam or better yet, rubber since foam rots too fast)...this will lower the response of the whole system. Stiffening the spider and compliance would work against that. Steve  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 01-21-2010 01:26 PM                        With respect to the original question, the subwoofer needs to be able to produce 115 dBC SPL at the "average" seating location. You will need to know the location of the subwoofer and its efficiency, as well as the location of the "average" seat. From this, you can determine what size amplifier you need to drive it, and ensure that the number of watts required does not exceed the maximum "program" power capacity of the subwoofer. You may end up needing multiple subwoofers, and you will want a safety margin to ensure that the amp does not clip and damage the speaker. The frequency response plot for both the subwoofer and stage speakers is also important, to ensure that there is a reasonable crossover point with sufficent overlap for both the sub and main speakers. Once everything is installed, you can set the exact crossover point and sub level with an RTA. This much is easy enough. What is not clear to me is how room acoustics affect the math. Efficiency measures are supposed to be done in an anechoic chamber. But what happens when you put the speaker behind a screen? What if the room is super-reflective? What about rooms with dead spots? And how is this affected by being a small room and not a theatre-size room?  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 01-21-2010 06:19 PM                        Just make it downward firing or . . . . better yet, put a clockwork motor in to rotate it slowly like a rotisserie chicken. Louis  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-21-2010 06:51 PM                     Joe, The other "thingy" is called a passive radiator... it's actually a "thingy" that causes higher harmonic distortion because it's movement is slightly delayed from the main driver. You may think it sounds good but the reproduction from that type of subwoofer system is not usually as "fast" as from a plain ole subwoofer. Steve, A late friend of mine that was a retired Radio Engineer had a stereo with a pair of cabinets with the 30" E-V drivers in them. As I remember they were fairly impressive... but I was probably about 16 years old when I first heard them and anything back then that large was bound to be impressive. I'm sure that any speaker that large would suffer form alot of cone breakup since it was just a paper cone. Cone materials have come a very long way since those days. Mark  |  IP: Logged Joe Redifer You need a beating today Posts: 12859 From: Denver, Colorado Registered: May 99 posted 01-21-2010 11:36 PM                        All subwoofers are inherently slow simply based on what frequencies they reproduce. But I know what you mean, the difference is negligible. quote: Mark Gulbrandsen You may think it sounds good but... But I would be wrong in thinking that? Is that what you are saying? I wouldn't recommend it for a real theater, but for the home it kicks tons of ass in a small space. I have mine set up in discrete mode only. I don't do any high-pass filtering of any of the other channels.  |  IP: Logged Ron Lacheur Jedi Master Film Handler Posts: 650 From: British Columbia, Canada Registered: Feb 2002 posted 01-22-2010 11:54 AM                     You could go with the QSC 21" subwoofer, or you could pull out all the stops and go with this.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 01-22-2010 12:07 PM                     Andy, come visit me and I will implode your skull with the QSC. You might look funny after that, but you will agree it is phenomenal.  |  IP: Logged Ron Lacheur Jedi Master Film Handler Posts: 650 From: British Columbia, Canada Registered: Feb 2002 posted 01-22-2010 01:49 PM                     Did you replace your subs in the screening room with the QSCs? Or are you using these in new installs?  |  IP: Logged Sam Graham AKA: "The Evil Sam Graham". Wackiness ensues. Posts: 1431 From: Waukee, IA Registered: Dec 2004 posted 01-22-2010 07:59 PM                        This is what I'm using (in a much smaller space) and am quite happy with it. But for the space you're talking about, I'd suggest this. Or maybe a pair of them.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 01-22-2010 08:38 PM                     Yes and yes.  |  IP: Logged Ron Lacheur Jedi Master Film Handler Posts: 650 From: British Columbia, Canada Registered: Feb 2002 posted 01-22-2010 09:19 PM                     Interesting. Just for curiousity, how many of the 21" did you use to replace to EVs?  |  IP: Logged Victor Liorentas Jedi Master Film Handler Posts: 800 From: london ontario canada Registered: May 2009 posted 01-22-2010 09:23 PM                     I am very impressed with Rel t2 subs,i have a t2 but they also make a t1 and t3! High end home stuff that produces a quality of bass i love!  |  IP: Logged Jake Spell Master Film Handler Posts: 294 From: Johns Island SC Registered: May 2009 posted 01-22-2010 11:20 PM                     personally, I prefer more smaller woffers, to one bigger one  |  IP: Logged Michael Voiland Expert Film Handler Posts: 219 From: Naperville, IL US Registered: Aug 2009 posted 01-23-2010 02:29 AM                     Brad this one wins Big Sub  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-23-2010 06:54 AM                     In what way does it "win?" It doesn't play very deep. JBL has numerous superior subs in the ASB line (will play as loud/louder, deeper, flatter). But for conventional theatre use, ˆ wouldn't use them either. I would stick to cinema subwoofers (JBL 4645C, 4642 or the QSC varients). They are going to perform better and cost less/watt and frequency response than a rental/staging speaker that is built for hanging and road trips. Steve  |  IP: Logged

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