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Author Topic: powering Community R.25 94tz speakers  (Read 2139 times)

Scott Stephens

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powering Community R.25 94tz speakers
« on: January 31, 2013, 04:54:38 pm »

Hi guys,
I've been asked to help a friend install 6 community R.25 200W/70v speakers in a small gymnasium. He wants to power them with a Crown 1160 MA 180 W/70v  4 channel in 1 out  mixer amp. I am questioning him on adequate power . I s it enough? Since it is 70v does it even matter?
Thanks,
Scott Stephens
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Chris Clark

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Re: powering Community R.25 94tz speakers
« Reply #1 on: January 31, 2013, 05:20:26 pm »

In my experience, 180W amplifier would only be enough if you were to run them all on the 25W setting. Best bet for amplifiers running 70V systems is to make sure your amplifier has adequate power for the sum of all transformer taps plus 20% to cover various transformer and line losses and such. If you plan to run these on the 200W setting (I have personal experience with these, they're pretty good at that setting) you'd want at least 1200 watts, 1440 to cover the 20%.

http://www.bogen.com/support/productcatalog/pdfs/SysDsgn.pdf
http://www.yorkville.com/default.asp?p1=6&p2=17&p_id=73
http://www.crownaudio.com/media/pdf/amps/138905-1_10-05_constant_voltage.pdf

Might want to read up on those, pretty good information (and more if you google) on best practice for designing 70V systems, including the theories behind "overpowering" the system (as opposed to the 50-65% typically recommended for sound reinforcement).

Additionally QSC has a handy spreadsheet to help determine amplifier sizes: http://www.qscaudio.com/support/resources/Ampifier_Matrix_Spreadsheet_with_70-100_Volt_system_calculator_v4-1-1.xls
Enter the number of wattage taps that will be on the system in the white boxes and it will show you the information about the power requirements.

(for the record, the R series seems a bit over the top with the weatherproofing involved in them which adds to cost, unless he already got them for free or perhaps there's a pool involved, but that's not really of my concern - just throwing it out there)
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Brad Weber

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Re: powering Community R.25 94tz speakers
« Reply #2 on: January 31, 2013, 06:28:54 pm »

I've been asked to help a friend install 6 community R.25 200W/70v speakers in a small gymnasium. He wants to power them with a Crown 1160 MA 180 W/70v  4 channel in 1 out  mixer amp. I am questioning him on adequate power . I s it enough? Since it is 70v does it even matter?
Yes, it matters at least as far as the amp needing to be able to drive the connected load.
 
They have six speakers with selectable 25W/50W/100W/200W 70V taps.  And an amp rated at 160W (at 1kHz) into 70V.  However, you are probably planning on reproducing more than just a 1kHz signal which means the amp may be capable of a bit less than 160W with wider bandwidth content.  And there will be some losses in the cabling to the speakers, through the transformers, etc.  Combine those and you seem to be just a bit on the low side even with the speakers at the lowest 25W tap.  I won't go as far as to say it won't work but if I were designing the system I would look at a larger amp.
 
It may also be worth noting that you would typically provide a high pass filter and some equalization for those speakers.
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Re: powering Community R.25 94tz speakers
« Reply #2 on: January 31, 2013, 06:28:54 pm »


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