This is topic how much watts for JBL speakers and subs ? if $$ was not at issue, how much U'd give in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by David Baum (Member # 568) on 01-02-2001, 05:36 PM:
them ?
options coming to my mind:
1. IEC ratings
2. twice the IEC ratings
3. 4 times the IEC ratings ( almost kidding 
)amps considered : QSC DCA ( I really love these )
I know that wires length will intervene as power will be lost along the lines but let's consider very short lenghts, less than 40ft, and AWG 10, and room 2/3 length being 10meters.
My opinion is option 1 considering the size of the room. Total system is 3677 for the front and center channels, 2x4645C for the subs and 4x8330.
Much interested into what power you guys give to your speakers system in say, 400seats theater ( medium sized ).
Do you often bridge amps or keep them in a stereo/parallel configuration to preserve damping factor and limit THD ?
thanks ahead
David
Posted by Paul G. Thompson (Member # 655) on 01-02-2001, 06:25 PM:
Efficiency of the speakers I think is very important. If they are too efficient, you could lose control. Check with John Allen. He is a nut when it comes to speaker efficiency vs room size.
Posted by Gordon McLeod (Member # 33) on 01-02-2001, 06:55 PM:
You calculate the head room you wish to have ie optical a type or sr digital or mag SR and then use the 1 watt one metre rating of the speaker to calculate the amplifier size required
Posted by Scott Norwood (Member # 30) on 01-02-2001, 07:09 PM:
You can blast a 400-seat theatre with somewhat less than one watt with Altec Voice of the Theatre speakers. I forget the efficiency rating, but it's something over 100 dB/watt at one metre.
Posted by David Baum (Member # 568) on 01-02-2001, 07:33 PM:
so, your main system to calculate the amp power required is to work with the log chart JBL provides ( as for instance with their 5000 serie speakers ) to assess the watts needed, given nr of speakers and their sensitivity ? and to increase dB level at low frequencies, adding more subwoofers rather than increasing wattage per any given subwoofer ?
Posted by Darryl Spicer (Member # 711) on 01-02-2001, 07:44 PM:
In some of our theater setups wee use both 400 and 800 watt amps. subs usualy use 800 watt amps feeding two subs. the main channels by 400watt amps switched to run left and center at 200 wats each and right and surround at 200watts each. our dts theaters have the amps byamped to feed 200watts to the horns and 200watts to the bass. Our newer theaters use all 800watt amps byamped to 400 watts. If when you pump 85 db of pink noise into your speakers you encounter the inability to obtain proper eq results your speakers may not be handling the wattage output. I wouldn't think that you would be having this problem with newer speaker designs but ask the experts about this.
Posted by John Pytlak (Member # 331) on 01-03-2001, 07:20 AM:
Next week's ITEA Seminar Series in Los Angeles has an entire session devoted to "Pleasing the Audience --- Applying Advanced Audio Engineering to Cinema Speaker Design for Full Auditorium Coverage" on Wedesday Morning, January 10.------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com