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Author Topic: Speaker and Amp recommendations Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-08-2015 09:06 PM                     The 4670D which I used some of in the 80's and 90's was fine in short throw auditoriums that were not over 40' long or more than 30' wide. It crossed over at 800 HZ, not 500 hz. There is no way that horn could do 500hz... Mark  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 09-09-2015 06:41 AM                     Read the 2380 specs...it was rated down to 500Hz and it had NO pattern control over 1000Hz. While people did use an 800Hz crossover to try and help it, it remained a miserable horn and was not suited to 40' throws anymore than it was suited to 70' throws. They only reason people used it was due to space limitations behind the screen, cost or a complete lack of understanding of why it was such much more inferior than the 2360. After all, on the surface, there was no difference in the 2360 and 2380...both had the same effective horn coverage and same crossover point...it is only when you dug deeper that one finds why it was vastly inferior. If you want to read about it...you need look no further than the spec sheet: https://www.jblpro.com/pages/components/2380ser.htm After looking at it...I need to amend my statement...it has no pattern control blow 2KHz! (in truth, it gets its pattern control somewhere between 1K and 2K). Conversely, the Altec MRII594A did small flat-front horns right: http://www.greatplainsaudio.com/vintage_altec/MRII594A_hfhorn_spec_sheet.pdf It had pattern control (and response) down to 500Hz...a FAR superior horn (and more uniform coverage)  |  IP: Logged Hector Perez Film Handler Posts: 2 From: Caracas / Venezuela Registered: Sep 2015 posted 09-09-2015 11:06 PM                     You´re Right Marcos, 105 dB Frontal Speakers, 102 dB Surround Speakers and (my own calc for Subwoofer Speaker are 113 dB if you have a recommendation for the calculation of the subwoofers, I will know to appreciate) in my Mind, i was thinking, i want to know that´s Theater, 100 m, I couldn´t believe it, and It is unthinkable. hehehehe... in 30m lose 29,5 dB, but 2/3 are 23m more and less, well then lose 27,2 dB. Christopher, this Speaker maybe can serve you, but do you need an on-site visit by a qualified tech. Frontal JBL 5742 Subs 4 X JBL 5628  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 09-10-2015 01:17 PM                     Hector, in the digital world the sub is now 115dB. I understand that 113 was used when dolby digital was around.  |  IP: Logged System Notices Forum Watchdog / Soup Nazi Posts: 215 Registered: Apr 2004 posted 10-03-2016 11:45 AM                 It has been 388 days since the last post.  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 10-03-2016 11:45 AM                     When setting up a 7.1 system, can different model surrounds be used for the rear surround channels and the side channels? Basically there will be 2 speakers each for the rear channel and 4 each for the side channels. I will need higher powered surrounds for the rear since there will only be 2 per channel.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 10-03-2016 01:36 PM                       You would need a 4 channel amp to address this mismatch in a satisfactory way. Also, it might be possible depending on location of the rearmost side surrounds to add them to the back surround strings.  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 10-05-2016 05:16 PM                     Yes, I am aware that additional amp channels are required. But, I am asking if it would be OK to use higher powered surrounds for the rear surround channels since there will only be 2 speakers for each of the rear channels?  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 10-05-2016 07:16 PM                     For me the question is how wide the back wall is. You want a "wall of sound" not easily discernible point sources (opinions differ, see Imax practice). I like to have speakers max 8ft apart. More smaller ones in a really small room.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 10-06-2016 01:59 AM                       quote: Tom Wienholt Yes, I am aware that additional amp channels are required. But, I am asking if it would be OK to use higher powered surrounds for the rear surround channels since there will only be 2 speakers for each of the rear channels? Your question does not have a simple answer. You can put more powerful speakers on the back wall but they need to be set to the same SPL as the side channels. More important, do they sound like the ones on the sides, as I'm timbre. This is usually close if you stay to the same brand and style as the sides, assuming the side speakers are "good" and in good condition. I agree with Dave here. You are very short on details for anyone to be truly helpful and you fail to understand we are trying to guide you, while you want oversimplified yes/no answers and seem annoyed at followup questions.  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 10-07-2016 04:59 PM                     Sam, thanks for the response. The room in question is 38' wide and 55' long with 21' ceilings. There are 4 surrounds on each side wall spaced 10 feet apart. There are 4 surrounds on the rear wall (2 per rear channel) spaced 8' apart. I was just curious if anyone had used higher power handling speakers on the rear wall, compared to the side channels (same manufacturer of course).  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 10-08-2016 12:33 PM                       Since the back surrounds are directly behind people's heads you have the set the level the same as the side speakers, 82 dB or 85 depending on the processor, the higher power may go to waste. The real question for any surround speaker array or "zone" is will it produce 100% modulation which is around 102dB without blowing up. That involves a bit of math and has to start with the power rating of the speaker, its efficiency, for example (95dB@ 1 Meter/1 Watt) and the amplifier power. You calculate the sound pressure level at the desired seat which might be 40 feet away. As a guide, it's a 6 dB drop every time you double the distance from the speaker, 2 meters, 4 meters, 8 meters, etc. This will tell you power required for the amplifier and the speaker array or zone. Don't be surprised if the existing side speakers won't meet this spec. Now with Atmos, each speaker in the surrounds would have the meet the standard above. Have fun. Guttag will be along to correct my math if he's in earshot. He always does.  |  IP: Logged Jarod Reddig Jedi Master Film Handler Posts: 513 From: Hays, Ks Registered: Jun 2011 posted 10-09-2016 07:32 AM                     All digital and no film make Film-Techers some dull boys. Me too but its almost my fav time of year. Go to QSC website and click solutions and choose the one that fits your room size best. Then make calls to reps or ones from reps past and find the best deal. Get it installed and EQd and your set. Mid-sized room solution on there may be your best bet with budget. Won't have to buy another system for many wonderful years just some minor upkeep. JBL? 3 used 4675 as said, 8340(a) or 8350(a) surround minimum 12 if using 7.1. 4 per wall has worked well in many theaters ive visited. One in a small town Ive seen many a classic at used two surrounds per wall and they had a balcony so all surround effects went unnoticed. Or in my case I noticed I didn't notice them  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-09-2016 09:18 AM                     Surrounds are supposed to be a non-directional non point source so i always prefer a large quantity of smaller speakers spaced closer together so there is no actual locating which speaker giving a diffuse and even coverage  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 10-09-2016 10:21 AM                       While Gordon is correct that it should be a diffuse field, it should at minimum be able to discern let wall, left back etc., i.e. 4 zones. Atmos takes off from there.  |  IP: Logged

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