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Author Topic: Subwoofer recommendations Amanda Mundin Expert Film Handler Posts: 122 From: Belper, Derbyshire, UK Registered: Sep 2005 posted 05-14-2006 01:42 PM                     I'm opening a single screen cinema, the auditorium is 45feet wide by 40feet long with a stadium seat rake and will seat 100. What subwoofers and how many subs would anyone recommend for an auditorium of this size? Thanks in advance  |  IP: Logged Mike Blakesley Film God Posts: 12767 From: Forsyth, Montana Registered: Jun 99 posted 05-14-2006 01:51 PM                        We have a slightly larger auditorium than you do (deeper but a bit narrower) and we have two 18" Peavey subs driven by a bridged QSC amplifier, I don't have the model # of the amp in front of me but a similar setup would do you very well. I like the Peavey subs fine and we've never had problems with them but if I had it to do over again, would probably go with JBL.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 05-14-2006 06:50 PM                     You have choices... My favorite sub at the moment is the JBL 4645C with B-6 alignment (use QSC's SF-3 module on one of their DCA or ISA amps or an RDL module (ST-C1XS). If you are going with digital sound, you tune things to spec and will run your fader at "7" (that is, you will need 113dB from your subs 2/3rds back in the room, you will need just over 1300-watts with two JBL 4645C subs. If you use the more popular though less bottom end sub, the JBL 4642A...you will need just one of those with about 1050-watts. If analog is all you are after, things drop down considerably. That is, you can get away with either one JBL 4645C or even the 4641 (about half of the 4642A) and use less than 200-watts. That 113dBc figure really kicks things up a bit.  |  IP: Logged Richard Hamilton Phenomenal Film Handler Posts: 1341 From: Evansville, Indiana Registered: Jan 2000 posted 05-14-2006 10:13 PM                     quote: Mike Blakesley I like the Peavey subs fine and we've never had problems with them but if I had it to do over again, would probably go with JBL. because?????  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-14-2006 11:02 PM                     Mike, Since some Idaho based theatre supply dealer sold the bejesus out of them and just about all theatres in the northern mountain states have them I literally lost count on how many Peavey 18" baskets I've replaced over the years... well over 50 of them! Like SDDS... they sound good when they work..... BTW: This guy even installed a single 18" Peavey sub with a set of Klipsch MWM large three way systems... The Peavey literally just gets lost in the runble the Klipsches put out..... Direct radiator subs and battleship sized horns just don't mix well anyway.... Mark  |  IP: Logged Mike Blakesley Film God Posts: 12767 From: Forsyth, Montana Registered: Jun 99 posted 05-15-2006 12:55 PM                        quote: Richard Hamilton because????? Because when we first bought the system, we got three different quotes. The top-end quote had all JBL speakers and QSC amps. The middle system had Peavey speakers and Peavey amps. (This was in '92.) The lowest-priced system had similar Peavey equipment but was a center-surround system. The middle-range system seemed a good compromise. Last winter we replaced the Peavey amps (because a couple of them had started to give us trouble) with QSCs, replaced the DTS with a CP650, and plan to upgrade the speakers eventually. If I had it to do over, I'd have saved-up a little longer and started with the top system, but that's just because I am kind of a sound nut... at the time I had to balance my economic situation with my huge desire to get us into the 20th century, soundwise.  |  IP: Logged Oliver Pasch Film Handler Posts: 53 From: Europe Registered: Jun 2002 posted 05-15-2006 02:42 PM                    My recommendation: KRIX KX 4610 from "down under" plus a powerful amp! KRIX Homepage Better than anything i've heard or felt before. Oliver  |  IP: Logged System Notices Forum Watchdog / Soup Nazi Posts: 215 Registered: Apr 2004 posted 03-08-2008 05:07 AM                 It has been 662 days since the last post.  |  IP: Logged Catalin Balaceanu Film Handler Posts: 36 From: Pascani, Iasi, Romania Registered: Mar 2006 posted 03-08-2008 05:07 AM                        I hope this is the right topic to ask my question: I've noticed that, in some movie theaters (especially those THX certified), have an incredibly powerful sub bass, that you can actually feel the floor and the chair beneath you, shaking like hell. Does anyone know any subwoofer model(s) that can achieve this kind of effect? The auditorium I have is 70 feet long, 45 feet wide, 25 feet high and has 400 seats. Thanks  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 03-08-2008 08:06 AM                     Which is the correct SPL I must take in consideration whith analog sound? 113dBc is for Digital, and for analog? Thanks Marco  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-08-2008 08:17 AM                     There are many that can do that. It is a matter of chosing a subwoofer that has a low frequency response (goes down to 20Hz or lower) and having enough subwoofer and the power to drive them to the proper level. A JBL 4645C is such a subwoofer (but there are others). If B-6 alignment is employed, its response goes down to about 20Hz. It can handle 800-watts continious and has a sensitivity of 97dB at 1-watt/1-meter. So with just one unit (it is a single 18"), you would need over 8000-watts to achieve proper level...well that won't work. So you add another identical unit. With two subs your power requirements drop to just over 4000-watts but you only have 1600-watts of power handling capability. So you add another sub and your power requirements drop to about 2700-watts but you only have 2400-watts of handling so finally you add a 4th sub and you come to 2024-watts needed and you have 3200-watts of power handling. Now it is a matter of getting enough amplifier power to deliver the 2024-watts across the four subs. One way to do this is with a QSC DCA-3422 amplifier...it has 1100-watts per channel into 4-ohms so wire the subs such that one pair is fed to each channel of the amplifier. Use the QSC SF-3 subwoofer filter to get the B-6 alignment that will extend the 4645C's response down to 20Hz and whola, you too will have a theatre shaking subwoofer system that won't blow up on any film running at fader setting "7" The keys here are that the subwoofers must be mounted together to achieve mutual coupling (that is why the power NEEDED kept decreasing as I added subwoofers) and you MUST use the continious PINK NOISE spec of a speaker...not "program" or "Peak". The subwoofer track resembles a continious signal and it can last for a protracted period of time...time how long the subwoofers were used when the rocket took off in Apollo 13...that scene took out MANY improperly designed subwoofer systems. The next key is that you have enough amplifier. You MUST use the 20-20KHz specification for the power handling. Many amplifier companies will use a 1KHz power rating spec to make them look more powerful....but ask yourself...self....how much single tone 1KHz singals are there in the subwoofer channel (or any other channel for that matter)? The answer is that the 1KHz power rating for amps is bogus and merely a marketing ploy that they all have to use in order to compete with those that only put that number out. QSC does list both 1KHz and 20-20KHz. In the case of the above mentioned DCA-3422...the 1KHz power is 1250-watts/channel into 4-Ohms but only 1100-watts/channel into 4-Ohms from 20-20KHz. When in doubt, over-speaker and over-amp...a system that is too small will fail...a system that is too large will not mind playing things below its maximum just fine! In the cinema industry...things are pretty well defined as to maximum levels so it is much easier to design a proper system...I'm amazed at how many people just guess or merely base a new system on how a system performed in a different theatre of different size. Steve  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 03-08-2008 08:38 AM                     Great informations. And what about the maximum SPL for analog systems? Thanks Marco G.  |  IP: Logged Catalin Balaceanu Film Handler Posts: 36 From: Pascani, Iasi, Romania Registered: Mar 2006 posted 03-10-2008 05:53 AM                        Steve, thank you so much for the detailed info. This is indeed very useful information. I can see you really like the 4645C sub Why is that? Marco, I think the sub level for the analog is the one stated in most of the analog processor manuals, which is 85db. Still, I hear that some keep their subs level to around 90 db.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-10-2008 06:20 AM                     For analog, you have the 85dB reference at 50% modulation...so for 100% modulation you come to 91dB...but for Dolby A there is a 3dB boost (over mono) and for Dolby SR you have a 6 dB boost (over mono or a 3dB boost over Dolby A) so you need to ensure that your sub can play a 97dB level...that is 13dB less than for digital. So, believe it or not...you are down to about 200-225 watts for a single 4645C subwoofer. Digital places HUGE demands on a system that analog does not. Again, this is presumming fader setting of 7. As for the JBL 4645C...yes I like that subwoofer. The driver is phenoninal (2242) and is one of the few that can take 800-watts pink noise...all day long (the way that driver cools its voice coil is better than most others). Also the 2242 in that cabinet with B-6 alignment is pretty darn flat, right out of the box so minimal EQing is ever needed. They can move a ton of air and down to 20Hz too. It seems to have delivered on every installation I've used it. So yeah, I like it quite a bit. Steve  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 03-10-2008 07:42 AM                       quote: Steve Guttag So with just one unit (it is a single 18"), you would need over 8000-watts to achieve proper level...well that won't work. Steve, thanks for all the great info. I was wondering how do you arrive at this figure? Also, what is a B-6 alignment? I'm not familiar with that term.  |  IP: Logged

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