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Discussion Starter #1
Hey All,


I have a 5.1 B&W CM9 setup with Towers in the front / bookshelf's in the rear.


Do I need a dedicated amp? I have been using my RX-Z7 Yamaha receiver which supplies 140 watts per channel, but I wanted to know if I would see a big increase in quality with an Amp. Thanks!
 

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Quote:
Originally Posted by Halbrium  /t/1522420/b-w-cm9s-do-i-need-an-amp-or-am-i-ok-with-rx-z7-140-watts-per-channel#post_24478592


Hey All,


I have a 5.1 B&W CM9 setup with Towers in the front / bookshelf's in the rear.


Do I need a dedicated amp? I have been using my RX-Z7 which supplies 140 watts per channel, but I wanted to know if I would see a big increase in quality with an Amp. Thanks!

What sort of SPLs do you drive those CM9s to? Have you invested in a SPL meter to measure that?


How far do you sit from the speakers?
 

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I don't have an SPL meter. I used the included mic and auto calibration and just made some adjustments to make things "sound better".


I sit probably 9 feet or so from the speakers +-2
 

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Quote:
Originally Posted by Halbrium  /t/1522420/b-w-cm9s-do-i-need-an-amp-or-am-i-ok-with-rx-z7-140-watts-per-channel#post_24478658


I don't have an SPL meter. I used the included mic and auto calibration and just made some adjustments to make things "sound better".


I sit probably 9 feet or so from the speakers +-2

You need something like a SPL meter if you wish to have people understand your preferences for listening when they are thousands of miles away.


Here is one that you can probably afford:

http://www.ebay.com/itm/8928-Decibel-Meter-Digital-Accurate-Sound-noise-pressure-Level-tester-40-130-db-/271167212819?pt=LH_DefaultDomain_0&hash=item3f22d34d13




It measures peak SPL and has a peak hold feature. That's what we need to know!
 

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What is your crossover point? 80Hz? The bass always requires the most power. So you will need more power in 2.0 mode than 2.1 mode. Farther listening distance like > 10 ft and louder volume like > 95 dB will also require more power.


Most non-deaf people just listening to music at regular comfortable volume will probably don't need more power than your AVR.
 

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The CM9 has a sensitivity of 92.5dB/2.83V/m. Minimum impedance is 3.4 ohms @ 116Hz.

http://www.soundandvision.com/content/bampw-cm9-speaker-system-ht-labs-measures


Let's say total volume from 2 speakers is 100dB (each speaker is about 97dB x 2 speakers in 2.0 stereo mode, no subwoofers). Distance is 10ft. Then it would take about 60 Watts into 4 ohms & 90 Watts into 3 ohms to produce a total volume of 100dB.


If total volume from 2 speakers is 103dB, it would require about 120W into 4 ohms and 180W into 3 ohms.


If total volume is 106dB, it would require about 240W into 4 ohms, 360W into 3 ohms.


Since your AVR can probably output 287 watts into 4 ohms, it should have plenty of power reserve given those parameters.
 
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