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Author Topic: Subwoofer recommendations Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-10-2008 09:13 AM                     quote: Tim Reed I was wondering how do you arrive at this figure? I just made it up and it sounded impressive No, actually I do the math. If you download (or you may have a copy) of the Dolby Technical Guidlines, you can use their nomograph...just beware, they are too low by 3dB on the Subwoofer graph. I think I heard the reason was something to the effect that the demands on the subwoofer would seem impossible to typical exhibitor and thus they didn't want to scare them away from doing it at least close to properly. 3dB is a doubling of power, as you know but about the difference between 7 and 8 on the Dolby fader scale. If you do use the 1994 version of the Technical guidelines...there is a formula on page 18 that will get you started...for subwoofers, power desired is 113dB, the distance is 2/3rds the length of the room (in meters). While I'm not a speaker designer, there are various design parameters or alignments one can design to and B-6 is one of them. Think of it as slit loss...if you design a speaker system to a standard alignment, apply the complimentary compensation in electronics, you will get a very flat response with a sharp fall-off...this is the case with B-6. A 4645C will play almost ruler flat down to 20Hz and then drop like a rock. This is good because with that cabinet, the driver will unload below 20Hz (actually it is 22Hz, I think)...thus you don't want to try and play below that frequency. A proper B-6 filter will high pass there. If you work with QSC products, their SF-3, SF-1 and all of their booth monitors will provide B-6 alignment. One can recreate a B-6 filter with appropriate parametrics...I believe it is a Q of 2 at 30 Hz. Note, Radio Design Labs also makes a suitable device called the C1XS. Steve  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-10-2008 09:17 AM                     Steve... I think DOlby need to revamp those guidelines based on then uncompressed levels found in D-Cinema. 113 db is simply not enough... Mark  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-10-2008 10:23 AM                     What are you sniffing? Compression and levels? DCinema uses -20dBFS reference...so yes, the subwoofer now needs to be able to make it to 115dB and the stage channels need to hit 105dBc but that is it...this has NOTHING to do with compression. But what the hay...so with a 115dB needed subwoofer here are the numbers for the 4645C.. For one unit, you need: 12,766-watts (see how 2 meezly dB affects things at that end of the power spectrum!). With 4 units you only need 3207-watts which is just about what the 4645C can handle 3200-watts for 4 units, continious pink noise. Add a 5th unit and you are down to about 2550 watts and enough driver to handle it. Again, this is true if you are running at fader 7 in a properly calibrated system. Note, however, I believe SDDS and DTS already had 115dB max rather than Dolby's 113. Then again, if the recording engineer is setting levels that are safe for Dolby Digital, the DCinema levels are not going to rise another 2dB so once again 113dB is safe so long as Dolby Digital films are being made and it has NOTHING to do with compression. Steve  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 03-10-2008 03:39 PM                       Thanks again, Steve. Very informative and enlightening.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 03-10-2008 04:19 PM                     Thanks Steve. I was searching the SR SPL limit figure since a while. I read older threads here about B6, you are always very clear. I'm just puzzled that there isn't many informations on JBL datasheets. For example, if you check on DCM Manager 2007, B6 is enabled on 4632-T, while on JBL's datasheet there is nothing. 4645C is just referring "with EQ". EV and QSC are much clearer. Again, thanks Regards Marco  |  IP: Logged Catalin Balaceanu Film Handler Posts: 36 From: Pascani, Iasi, Romania Registered: Mar 2006 posted 03-10-2008 05:45 PM                        Man, I love this forum!!! Thanks for the very useful information, Steve.  |  IP: Logged Catalin Balaceanu Film Handler Posts: 36 From: Pascani, Iasi, Romania Registered: Mar 2006 posted 03-21-2008 10:49 AM                        is there a big difference between the 2242h and 2242hpl drivers, except the rubber tire around the magnet on 2242h? Thanks Catalin  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 03-21-2008 10:51 AM                        No: only the source: "pl" is private label. Same specs. Louis  |  IP: Logged Catalin Balaceanu Film Handler Posts: 36 From: Pascani, Iasi, Romania Registered: Mar 2006 posted 03-21-2008 10:53 AM                        thanks for the fast reply, Louis!  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-21-2008 11:39 AM                     The "pl" at the end of the model denotes that the frame's outer ring is black rather than silver. A big plus for cinemas...in the 80s we were constantly painting the damn things! As for the rubber boot...it is not normally included (and often the actual driver label isn't either) on pre-assembled speakers. When drivers are sold as components, they come with the boot and the label. In the case of the 2242, I believe the label is always included (it is just a sticker). Steve  |  IP: Logged Ron Funderburg Jedi Master Film Handler Posts: 814 From: Chickasha, Oklahoma, USA Registered: Nov 2007 posted 03-21-2008 01:54 PM                        Just curious about specific type of Sub that seems to have come and gone. Several years ago there were several Tech's that were pushing an aqueous (not sure about sp) sub it had water in a sealed plastic chamber or bladder in the top of the sub. The theory was that can't compress water so the sound waves would push up against the water and it would force it back down and out making and I quote “More bang for the buck”. I went to several demonstrations where they had the aqueous in one theater and would play stuff and you would feel it. Then across the hall they had the regular sub and you wouldn't feel it as much but when I toured the booth the settings on the faders were different so it appeared to me that the aqueous auditorium was being played at 7 and the non was being played at 6. That is big difference and I thought to myself “Self that Aqueous is just a rip” It was only highlighted for about 3 years then went away from what I can remember. It seems like it showed up in 1999 and was gone by 2001 or 2002. Anyone have any unbiased information on them? Steve you are well in to the know on things, what do you know on this? I think the fact I don't seem the advertised anymore speaks volumes or maybe with great volume!  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-21-2008 06:06 PM                     Abingdon Cinemall uses them, as I recall. I have not given them a serious listening so I can not offer any real comments on them. As you know, sound is quite subjective and, as such, there are not definative speakers that are simply the best. Those speakers that I am familiar with, I have voiced noted preferences and I generally can back them up with some not so subjective facts...like sensitivity, frequency response and power handling...which is not to say they necessarily sound good or better than others (except in my opinion) but they technically qualified for the job. Steve  |  IP: Logged Ron Funderburg Jedi Master Film Handler Posts: 814 From: Chickasha, Oklahoma, USA Registered: Nov 2007 posted 03-21-2008 08:04 PM                        Steve I did find a website with an article which reviews Hydrosonic HS-12S, which is a similar sub if not the one! It supposedly moves the sound though the concrete so you feel deeper according the article and they have all kinds of charts and graphs to support the claim but having only heard it once or twice I can't make an honest evaluation on it. Like you I find sound is in the ear of the beholder! We can all agree on pure crap but when it comes to this is better no that is better people seem to be all over the place. This is the web article I can't see upload date on it! http://www.ultimateavmag.com/features/704way/index4.html I saw the movie Rules of Engagement with Tommy Lee Jones and when the helicopters flew over the had part of the blades rotating around in the subs and you could feel air move over you. That impressed me but it could have been as much volume as the design of the sub.  |  IP: Logged

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