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Author Topic: Thoughts on the JBL 3678. Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-08-2015 07:54 AM                     quote: Gerald Dente I also have twelve ported 18" subs in that room also I would probably add a couple to be on the safe side.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 07-08-2015 08:59 AM                     What makes you think that the DSi amps would get the most out of the speaker (or any speaker, for that matter)? Because Crown/Harmon put in a cheeseball DSP setting into it? Believe that if you like.  |  IP: Logged Gerald Dente Film Handler Posts: 14 From: southborough MA usa Registered: Jun 2015 posted 07-08-2015 10:15 AM                     I like the idea of having the active presets built into the amp. Sure you will need to configure the settings after the fact but its nice to have the basic's of running the active speaker setup for you. As for crown amps I think they are pretty decent quality.  |  IP: Logged Gerald Dente Film Handler Posts: 14 From: southborough MA usa Registered: Jun 2015 posted 07-13-2015 07:32 AM                     Since QSC doesnt list measurements for their small Cinema line I called them and ask for more info. The active version is anechoically flat +\- 2db and the directivity from 50hz to 19khz. It would be an easy choice but, its still very large and has far more output then my small room would need. I heard good things about the 1120 and I would pick that over the 15" due to the horn being smaller to not having their diretivity match  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-13-2015 08:36 AM                     which speakers was that?  |  IP: Logged Gerald Dente Film Handler Posts: 14 From: southborough MA usa Registered: Jun 2015 posted 07-13-2015 12:31 PM                     I was referencing the 4722 JBL. Sorry.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-13-2015 03:40 PM                     you were mentioning the 'small cinema line" from QSC, which one do you refer when you mention the frequency response?  |  IP: Logged Gerald Dente Film Handler Posts: 14 From: southborough MA usa Registered: Jun 2015 posted 07-16-2015 07:24 AM                     I am speaking about the sc-1120 they only state some specs. Not actual measurements or when the khz drops off. Rated Coverage Angle (-6 dB) 90° Axisymmetric Frequency Range 1 (-10 dB) 48 Hz to 19 kHz Rated Noise Power 2 300 Watts Sensitivity 3 95.5 dB Maximum Continuous SPL 4 120 dB Maximum Peak SPL 4 126 dB Rated Impedance 8Ω Maximum Recommended Amplifier Power 600 Watts Transducers LF: 12" (305 mm) woofer, 2.5" voice coil HF: Compression driver with 1.75" (44 mm) voice coil Enclosure MDF, non-reflective vinyl wrap Dimensions (HxWxD) 27.2" x 19.5" x 11.7" (690 mm x 497 mm x 297 mm) Net Weight 51 lb (23.2 kg) I am boiling a choice down to the sc-1120, jbl 3677 and 4722. I am leaning more towards the qsc 1120 at the moment. Cost is not the issue. Mostly size and I want to make sure I get the right speaker for my small room application.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-17-2015 01:23 AM                     Ok. If they claim they're flat +/-2 till 19k, why the specs say +/-10dB? What happened to the other 8dB?  |  IP: Logged Gerald Dente Film Handler Posts: 14 From: southborough MA usa Registered: Jun 2015 posted 07-17-2015 07:12 AM                     Thats exactly what I want to know. I heard back from QSC and they have no other documentation on the speaker except whats listed on the site. I cant demo these things, and changing them out after I build a wall around them will be a pain to change over again. Less the price more about the work involved with installation and configuration. I am sure they sound decent but, it would be great if they had anything more for me.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-17-2015 01:55 PM                     good luck! Let us know what you find.  |  IP: Logged Jarod Reddig Jedi Master Film Handler Posts: 513 From: Hays, Ks Registered: Jun 2011 posted 07-17-2015 06:57 PM                     Just go with the 4722 and don't look back!!  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 07-18-2015 01:36 PM                     quote: Gerald Dente I heard back from QSC and they have no other documentation on the speaker except whats listed on the site. It puzzles me that they don't have any. How did they come up with the two figures they gave you? I assume the speaker went in an anechoic chamber for testing. Why shouldn't they share that graph with their customers? If the speaker is so flat as they claim they should share as many documents as possible to back their claims and show people how good their speakers are.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-19-2015 09:35 AM                     Not all manufacturers test in an anechoic chamber. We certainly don't listen in one. Some companies actually do testing out doors and in real life. Meyer Sound Labs is one that does that... Mark  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 07-19-2015 09:57 AM                     A VERY bad trend in speaker manufacturers that have their own DSP brand associated with them (like Harmon does with dbx and BSS ) is that they will come up with their own special DSP settings that may have been done in an anechoic chamber and may have even been done with their own super-duper testing that they think gives validity. As such, the specs are based on that and so long as you use their DSP, it should all work. Mark brings up a valid point...anechoic chamber testing is but one sort of test to see how the components perform without outside influences...but how do they perform in their intended application? There are speakers that don't "look" so bad on their anechoic response but absolutely sound horrendous, particularly in theatrical environments. I've found that factory settings don't always work the best in the world...I've really seen this on time delays for time alignment on multi-way systems. And if you aren't using the system that the speaker manufacturer tested it on, it definitely will be different due to the differing processing times. I expect speaker manufacturers to provide frequency response curves and ideally polar plots on the horn loaded stuff but they rarely do. These give good indication as to what one can expect. With the smaller "Economical" systems, one is less likely to get detailed information. It probably doesn't help their cause to publish them since it is less likely a value priced system is going to perform like a higher-end system. There is no "free" in this world. Using a -10dB response may be standard for the industry but it really doesn't tell you when it started to nose dive nor what sort of bouncy response it has in the pass-band. Another thing to look out for in speaker specs is the sensitivity. The standard is 1-watt/1-meter. When one uses the voltage like 2.83V...they are likely hiding something because they want YOU to do the math (and it isn't hard...V^2/R = Watts)...Miss reading this spec will likely make you think it is more sensitive (needs less power) than it does.  |  IP: Logged

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